Thermal dynamics of Jaipur: Analyzing urban heat island effects using in-situ and remotely sensed data

Abstract The Urban Heat Island (UHI) effect is a phenomenon where urban areas experience higher temperatures than surrounding rural areas. In these issues, enhanced air or surface temperature is one of the major issues that led to the UHI phenomenon. In this article, we come up with a study on the diurnal UHI effect caused in Jaipur city, India, and surrounding areas of Jaipur. In-situ temperature monitoring has been carried out at seven dispersed locations to properly understand and evaluate the effects of surface UHI (SUHI) and atmospheric UHI (AUHI), as well as to assess the thermal profile of diverse land surfaces in Jaipur. With the use of satellite data, the intensity of AUHI and SUHI has been determined between 10.30 a.m. and 10.30 p.m. The observations point out that positive AUHI intensity (AUHII) exists at many locations, irrespective of time periods. During the day period, negative SUHI intensity (SUHII) was noticed at many locations, whereas during the night period, positive SUHII was noticed. According to our observations, AUHI and SUHI have a direct correlation at night but a negative or inverse correlation during the day. That is, AUHI was active both during the day and at night. Various land surfaces play a significant role in contrasting the diurnal UHI effect. This study evaluates the potential of remotely sensed data in monitoring the UHI effect and provides recommendations for urban planners and policymakers to mitigate the UHI effect in the city of Jaipur.


Introduction
In many human activities, urbanization is the most important activity that creates major impacts on the local and regional eco systems and also globally (Nasir et al., 2022;Rendana et al., 2023;Turner et al., 1990).It is the major reason for the transformation of natural surface areas into anthropogenic impervious surface areas.Dramatic climate changes occur when low-and high-albedo materials are introduced.Atmospheric and surface changes made by urbanization give rise to a change in thermal climate that is much warmer when compared to neighbouring rural regions, especially at night.This phenomenon is denoted as an urban heat island (UHI) (Voogt & Oke, 2003).
The land surface temperature (LST) and air temperature can be used to determine the UHI effect, referred to as the surface UHI (SUHI) effect and the atmospheric UHI (AUHI), respectively.The main reason for the SUHI is due to the changes on the land surfaces through urban enhancement by utilizing the materials that retain the heat effectively.Due to urbanization, physical and chemical characteristics of the atmosphere are modified, which leads to environmental pollution and changes in the soil surface (Badugu et al., 2023a(Badugu et al., , 2023b;;Gupta et al., 2020;Kaya et al., 2012;Khare et al., 2021;Kwofie et al., 2022;Ma et al., 2023;Santamouris et al., 2001;Tabatabaei & Fayaz, 2023;Xi et al., 2023).UHI and climate change are significant environmental factors that have a negative impact on the comfort of building occupants, increased resource use, and environmental footprint of existing structures (Akkose et al., 2021;Badugu et al., 2023aBadugu et al., , 2023b)).
The difference between rural and urban temperatures as well as the magnitudes of UHI can be referred to as UHI intensity (UHII) (Clinton & Gong, 2013).Urban heat islands are present when there is a positive difference (urban areas are hotter than rural areas), while urban heat sinks (UHS) are present when there is a negative difference (rural areas are hotter than urban areas).On a daily and seasonal basis, SUHI and SUHS can be categorized as temporal variables (Clinton & Gong, 2013).Throughout the day, a variety of materials absorb and store solar energy, which is then gradually released at night.As a result, SUHI intensity is rather high at night (Abutaleb et al., 2015).Another well-known factor that affects the impact of UHI is urban geometry.Urban canyons are characterized by the presence of narrow streets and tall structures, which decrease the wind speed and trap heat due to the presence of reflective surfaces (Vasenev et al., 2021).Solar and infrared radiations will be absorbed as shortwave radiation by the building fabric material, these stored heats will be released as longer wave radiation to the atmosphere by this fabric material (Santamouris et al., 2011).Based on time, environmental conditions and structural attributes, the calculation of UHI intensity in urban regions was described using simple methods (Arnfield, 2003).
In the recent half century, global warming has become one of the most-identified issues in the atmosphere which is developed by rapid industrialization and urbanization (Chung et al., 2004;Dewan et al., 2021;Mathew et al., 2022).The factors that involve magnitude and extent of the UHI are geometry, size, and population of the city (Oke, 1981).Due to the rise in population and physical infrastructure in East Asian cities, the UHI phenomenon is considerably more noticeable there (Hulme et al., 1994;Hung et al., 2006).Ichinose et al. (1999) reported that throughout the last 135 years, urbanization has produced temperature shifts, resulting in a warm bias of 2.8°C as the lowest temperature in the Tokyo climate record.Chung et al. (2004) observed that between 1951 and 1980 and 1971 to 2000, the lowest temperature in Seoul rose by 0.7°C.According to Boonjawat et al. (2000), Bangkok saw its lowest air temperature in 50 years at 1.23°C.According to Zhou et al. (2004), development in southeast China has caused the LST to expand by 0.05 OC/ decade since 1978.Lokoshchenko (2014) reported that there was an average UHI intensity of 1.0-1.2K at the end of the nineteenth century, 1.2-1.4K in the first two decades of the 20th century, and 1.6-1.8K in the middle and at the end of the 20th century after analyzing long-term temperature data for Moscow.
Many UHI studies were performed for the past few years to identify changes in temperature using both ground sensor readings (Dash et al., 2002;Golden & Kaloush, 2006;Snyder et al., 1998) and remotely sensed data (Chen et al., 2012;Friedl, 2002;Seguin & Itier, 1983).For analysing the climatic alteration of a city, the most important parameter that needs to be measured is UHII (Mathew et al., 2017;Stewart & Oke, 2010).While surface UHII (SUHII) is produced from satellite data based on LST, atmospheric UHII (AUHII) is UHII derived from a weather monitoring station based on air temperature (Memon et al., 2009).It has been demonstrated that the UHII maximum typically develops on calm, clear evenings throughout the summer (Mihalakakou et al., 2004;Oke, 1973;Ripley et al., 1996).Compared to metropolitan regions, rural areas see higher cooling rates and temperature drops (Oke, 1982).Theoretical and empirical study data are gathered in North American cities, and it is observed that UHII rises in 3-5 h after the sunset (Oke, 1987).However, numerous study publications state that the UHI intensity rises and peaks at various times of the day, such as during the day, at midnight, or just before and after sunset, and this is amply demonstrated by the thermal balance for certain rural and urban locations (Livada et al., 2002;Skoulika et al., 2014).
The peak UHII always occurs during the warm weather except in the humid weather.It is observed that the average daytime UHI is smaller than the Night time UHI particularly at the period of the summer in arid cities and coastal areas (Ramamurthy & Sangobanwo, 2016).
According to Tan et al. (2010), Shanghai, China, experiences its highest UHII during the night, particularly in the autumn and winter.From the observations, it is noticed that high UHII occurs during the noon time in the summer season Saito et al. (1990) has been noticed that high UHI occurs during the daytime in Kumamoto, Japan, whereas during night-time second peak UHI is observed.The UHII is apparent in Guwahati City, India, both during the day and at night Borbora and Das (2014).According to Sofer and Potchter (2006), urban temperature variations cause significant UHI to occur in Eilat, Israel, during the afternoon.In Muar, Malaysia, both the daytime UHI maximum and the nighttime UHI peak occur Rajagopalan et al. (2014).In Beijing, China, strong UHII has been found late at night (Liu et al., 2007;Miao et al., 2009), but in Muscat, Oman, a high intensity of UHI was observed 6-7 h after sunset (Charabi & Abdelhamid, 2011).According to Mohan et al. (2012), high UHI occurrences are reported in Delhi in the late afternoon and at night, whereas in Ulan Bator, Mongolia, the UHII during the day is five times lower than that during the night (Ganbat et al., 2013).Since the UHI impact exhibits considerable fluctuations during the daytime and night-time, it is crucial to examine the daytime and night-time UHI effects in the semi-arid Indian towns as well as to understand the main reasons for the contrast temperature pattern for day and night.
At the time of low wind conditions in India during the months of November and December, Pandey et al. (2012) have noticed that daytime urban cool island (UCI) occurs at central region of Delhi.During these months, daytime LSTs in Delhi experienced 5-6°C when compared to rural areas.In daytime, air temperature-based UHIIs have been noticed to be lower, whereas it is higher at the night time (Hafner & Kidder, 1999;Montavez et al., 2000).Numerous studies have revealed that elevated UHII levels can be seen at any time of day or night (Hung et al., 2006;Memon et al., 2009;Pongracz et al., 2006).Kim and Baik (2005) observed that the UHII experienced during the day is 3.3 times less than that experienced during the night, whereas Montavez et al. (2000) reported that the least UHIIs are experienced during the day and the most are experienced during the night.In the whole spatio-temporal patterns, greater UHIIs are observed during the solar offpeak period (i.e., early morning, evening, and night-time when solar energy is not the foremost source).Atmospheric UHI fluctuations in 10 U.S. cities have been studied by Ramamurthy and Sangobanwo (2016), who reported that many coastal cities had negative UHI, while many inland towns had positive UHI.In Singapore, underdeveloped regions exhibit a cool island effect, as noted in the forested areas studied by Chow and Roth (2006).Conversely, high Urban Cool Islands (UCIs) were observed in the Central Business District (CBD).This UCI phenomenon in the CBD is attributed to factors such as the shading provided by tall buildings during the day and the proximity to the sea and local river, as detailed in the research conducted by Chow and Roth (2006).Protracted shading in urban canyons reduces diurnal thermal flows, cool sea breeze in coastal areas, and less anthropogenic heat will lower the temperature in urban areas when compared to rural areas and also the existence of cool islands.In many cities of India, cool islands are noticed and it influences a diverse climatic change in each city.During the diurnal cycle, noticeable changes occur in UHI intensity, which suggests the existence of a diurnal UHI effect.Whereas in semi-arid Indian cities, contrasting diurnal SUHI pattern was noted, contradicting the observations of past studies.Therefore, studying and analysing the diurnal impact of Jaipur city with semi-arid climate is considered more significant.
A significant research gap exists in the understanding of diurnal atmospheric and surface UHI effects in Jaipur City.Despite extensive studies on UHI effects in various urban areas, there is limited research specifically examining the UHI effect in this rapidly growing urban center in India.This gap in the literature hinders our knowledge of the unique UHI dynamics in Jaipur City, which is essential for tailored urban planning and mitigation strategies.By addressing this research gap, the study contributes valuable insights into the UHI effect's impacts on urban environments in a previously underexplored context.
This study integrates both in-situ and remotely sensed data to compare the spatial and temporal patterns of the UHI effect over Jaipur City.This approach provides a more comprehensive understanding of the UHI effect and its impacts on urban environments.This approach allows for a better understanding of UHI effects at the city level, including their spatial and temporal variations.While the UHI effect has been extensively studied in other cities, there is limited research on the diurnal atmospheric and surface UHI effect in Jaipur City.This study fills this gap in the literature and provides insights into the UHI effect in a rapidly growing urban center in India.Overall, the study provides a unique perspective on the UHI effect and its impacts on urban environments, and makes a valuable contribution to the literature on this topic.This study integrates both in-situ and remotely sensed data to analyze the spatial and temporal patterns of UHI effects across the city.This approach provides a more accurate and detailed understanding of UHI effects and their variations across different seasons, urban landscapes, and land-use patterns.Additionally, the study contributes to the scientific literature on UHI effects in the region, which is important for policymakers and urban planners to develop effective strategies to mitigate the adverse impacts of UHI on urban environments and human health.

Study area
Jaipur, the tenth-largest city in the nation, is the capital of Rajasthan, which is the largest state in terms of land.Jaipur has a population of 3.15 million (Census of India, 2011).The West, West-East, and South slopes of the Aravalli hills encircle the city, which is situated on a largely level plain.The majority of the study area has a semi-arid climate, which Köppen Geiger categorizes as "BSh" and is characterized by extremes in daily and yearly temperatures, little precipitation, and low relative humidity.The Jaipur region has frigid winter nights with average air temperatures of 3°C.The mean daily air temperature significantly varies during the monsoon season due to the various weather conditions.In the summertime, the maximum air temperature is 48°C, and the afternoons are the hottest times of the day.In general, the region has water shortages during the monsoon season, with an average annual rainfall of 550 mm (Tyagi et al., 2011) (http://www.imdpune.gov.in/Temp_Extremes/histext2010.pdf).
The 2011 MODIS LC type image (https://lpdaac.usgs.gov/dataset_discovery/modis/modis_products_table/myd11a2) was used to retrieve the urban region, and the LC image was used to produce the urban area polygon (UAP).Figure 1  UAP was retrieved from the LC product derived from the MODIS image in order to identify Jaipur City's urban limit (MCD12Q1, spatial resolution of 463.30 m).The UAP ranges for Jaipur's study area are 24 km in the north-south direction and 16 km in the east-west direction.There should be adequate rural and semi-urban landscapes in the research area.A 12 km buffer, or half the size of the whole metropolitan region, was built outside UAP to delineate the study area's boundaries.The area within this borderline was the subject of the investigation.Between latitudes 26°42'57.48and 27°04'39.17north and latitudes 75°40'12.22and 75°51'37.09east, the research region is mostly located.The study region occupies a region of approximately 1370 km 2 (1595 pixels), including sufficient non-urban /suburban areas and the city's satellite towns for association with urban areas (Figure 2).

Land surface temperature
The 8-day MODIS LST product, MYD11A2 has been used for both daytime and night-time.This is measured by combining two to eight days view-time LST for clear-sky environments (Wan, 2007).The product MYD11A2 also has a consistency flag with SDS layers format, for LST.This consistency flag includes details on the methodology results for each pixel that can be interpreted in a spatial sense.The consistency flag can be used to evaluate the results of the algorithm to determine whether the output of the algorithm for a specific LST is trivial, abnormal, or whether a pixel has met some other specified condition.

In-situ atmospheric and surface temperature measurement
In-situ atmospheric and surface temperatures were measured over a span of 27 h (2 PM to 5 PM next day) at seven sites in the study region of Jaipur, simultaneously where three are within the city boundary and four are in rural areas.Table 1 provides descriptions of the field survey observations date and period.The goals of this field research are to compare the effects of SUHI and AUHI and analyze the comparative temperature profiles of various land uses at these locations.Figure 3 displays the specific locations of seven field survey sites.Table 2 provides a description of the geographic specifics of the actual field survey locations.The temperature was measured every one to two hours at specific intervals.The interval was set at 1 h during the day, 1 h 30 minutes at night and 2 h during the night based on fluctuations observed in LSTs.8-14 measurements were taken on each surface layer of the land, and the mean value of these surface measurements was perceived as the LST of that surface layer at the time.For the calculation of LSTs for various surfaces, infrared thermometers were used.A miniinfrared thermometer (Make Fluke, Model 59) was utilized to measure in-situ temperatures ranging from −18.15°C to 274.85°C.The unit functions on 9-V battery.Optical resolution is 8:1 (the ratio of distance to spot size).The system is designed to operate with an accuracy of about 2% between the ambient temperature range of −0.15°C to 49.85°C and 10-90% relative humidity @ 29.85°C.In order to ensure the accuracy of calibrated equipment used for monitoring the field atmospheric temperature, air temperature was also computed at 1.5 m above Earth's surface utilizing data logger and sensor instruments as well as the heat stress meter technique.AUHII and SUHII were identified at the time of the AQUA/TERRA satellite's transit over the research region (10:30 AM and 10:30 PM).The location where the lowest air temperature was recorded at 10:30 PM was where the UHI intensity was calculated.
Measurement in-site was performed for four various surfaces, and the thermal pattern of these surfaces was measured simultaneously.The terrestrial surfaces chosen for the analysis are concrete paving over a well-compressed stone course (concrete layer), pavement with bitumen stretching over well-compressed water-bound macadam (WBM) surfaces (road layer), soil layer with zero flora (soil layer), and grass cover with no clear soil layer under it and dense plant or shrub (green cover).Throughout the tests, no exterior water was applied to any of the surface layers.

Diurnal surface temperature variations on Jaipur city
In order to conduct the 13-year (2003-2015) LST seasonal research in Jaipur City, the year was divided into the winter, monsoon, and summer seasons.Separately, images of daytime and nighttime were considered.

Day period LST images
In general, despite large seasonal oscillations in the LST in the study region, the daytime surface temperature trend has remained stable over the course of the investigation.However, daylight surface temperature differences in both space and time can be quite significant.Additionally, there are noticeable shifts throughout the seasons, especially in rural locations.A negative or inverse SUHI is seen across the area of analysis throughout the year in the spatial profile of day LST images.The occurrence of the urban cool island phenomenon in the CBD can be ascribed to several factors.These factors encompass the daytime shading effects generated by tall buildings and the close proximity of the CBD to waterbodies and vegetation (Chow & Roth, 2006;Mathew et al., 2018).
Outside the urban boundary, a significant part of the region appears red in color reflecting high daytime temperatures in this region.For all seasons, the rural region displays higher LSTs than the urban region (Figure 4(a,c,e)).High-temperature pixels within the urban boundary almost do not exist during the daytime.South and East parts of rural regions experience greater temperatures than urban regions.The majority of the region that falls within this region is unfertile barren ground.Energy interactions between bare soil and green land are recognized to be varying because there is no moisture present in bare soil and the cooling rate of the two types of land surfaces is also varied, causing temperature profiles to vary across different sections of the study region.Due to the reduced wintertime heat and the weak effect of differential cooling, this difference is less noticeable during the wintertime.Due to the presence of agricultural/vegetation lands around this region, north-eastern zones of rural regions display low surface temperatures.
During various seasons, the daytime LST images display identical patterns and it is possible to find certain variations as well.Throughout the summer season, the East zone of the urban limit experiences low surface temperature pixels, while the East zone of the urban region experiences higher surface temperature than the West zone of the urban region.The south zone of the research region exhibits high surface temperature pixels, and peak surface temperature is also only noticed during the winter season in this region.

Night period LST images
The LST trend across the research region changes during the nighttime to that seen during the daytime trend.At nighttime, the urban region shows higher LST than the rural region.Annually, the LST trend over the research area does not fluctuate significantly.
Peak LST is seen in the urban area that is closest to the eastern edge of the urban area.This area of the urban zone is mostly made up of paved and built-up areas, hence the nighttime LST is at its highest point in all seasons.This sector also has some pixels with extremely high temperatures.A piece of the rural area, next to this portion and outside the urban boundary, belongs to the range of the Aravalli Mountain ranges.In this region, mining was done to meet the requirement for rocks for construction activities which caused direct solar radiation in rock surfaces.The rocks' energy interaction is close to the built-up environment, causing peak temperatures in this zone.Most of rural regions exhibit low surface temperatures for green land or bare land.From the images, it is clear that there is a thermal gradient as we pass from peak LST pixels to rural or other areas of the city region.
Lower surface temperatures are identified over the region at the study region boundary, particularly in the North-West part.LSTs in the East and South zones of rural regions are greater than in other portions of rural areas (Figure 4(i) b,d,f).Certain portions of rural regions, during the monsoon season, exhibit significant variations in LST.The winter season, however, reveals a significant gap in urban and rural surface temperatures relative to other seasons.
The LST of different zones in Jaipur study area shows seasonal and nocturnal variations.UHI intensity (UHII) was calculated during concurrent observations as the difference in LST between two pixels or locations inside the study area.The UHII maximum was discovered to be the UHII that corresponds to the pixels or spots that record the greatest and lowest temperatures (Arunab & Mathew, 2023).
UHII is influenced by climatological settings including cloud, wind, and anthropogenic heat release circumstances, and it exhibits both diurnal and seasonal cycles.The seasonal and annual  mean of maximum UHII for Jaipur is given in Table 3.Over the period of the study from 2003 to 2015, the maximum nighttime UHII during the summer period ranges from 9.80°C to 13.90°C and from 7.58°C to 12.42°C during the monsoon season and from 10.04°C to 15.10°C during the winter season.Similar to this, the minimum UHII nighttime temperatures range from 3.96°C to 6.22°C, 2.12°C to 5.26 °C, and 6.28°C to 8.78°C, respectively, during the summer, monsoon, and winter seasons.The mean maximum SUHII temperatures for the summer, monsoon, and winter are 8.39°C, 6.83°C, and 9.60°C, respectively.The average SUHII during the experiment was 8.50°C.
Significant diurnal LST changes were observed in the study region across the different seasons.The diurnal thermal trend reveals a consistent strong SUHI at night (for all seasons) and a significant temperature difference between urban and rural areas.During the day, the study region also exhibits negative or inverse SUHI (especially in summer and winter) or no SUHI (during the monsoon season).

Inter-comparison of AUHI and SUHI effect on Jaipur
Using atmospheric temperature acquired from in-situ measurements at seven different places and surface temperature data acquired from satellites, the occurrence of AUHI and SUHI in Jaipur was investigated.When the Terra satellite passed over the research zone at 10.30 a.m. and 10.30 p.m., the intensity of SUHI and AUHI was estimated.The UHII was measured as the difference of two points between the highest and lowest temperatures.The position where the atmospheric temperature is low at 10.30 PM was taken as the reference temperature and was measured with respect to this reference temperature for the UHII at all other locations.AUHI intensities were determined by means of in-situ atmospheric temperature measurements, and SUHI intensities were estimated using data from the MODIS Terra LST.

Summer season
Table 4 indicates the atmospheric and LST values during the summer season, as the satellite passes time at different locations.At Sitapura, a minimum air temperature of 30.2°C was recorded, and the UHI intensity was measured with respect to the Sitapura temperature.The MODIS generated diurnal LSTs noticed at 10:30 AM (45.75°C) and 10:30 PM (27.75°C), respectively, were taken as the basis LSTs for SUHII measurements.For day and night AUHII measurements, the atmospheric temperature reported at Sitapura at 10:30 AM (40.4°C) and 10:30 PM (30.2°C) was taken, respectively.4.2.1.1.Day Period.During the daytime, Kanwar Nagar exhibits the lowest SUHII −1.90°C which obviously depicts the presence of the inverse SUHI effect in the region.Similarly, when using MODIS day LST results, most research sites display negative SUHII varies from −0.10°C to −1.90°C.This clearly indicates that, if LST is utilized for the study of UHI influence, inverse or negative SUHI occurs in the research region during the daytime.In comparison, most of the sites display positive AUHII varying from 0.20°C to 3.10°C, when using atmospheric temperature that evidently indicates the AUHI effect on the research region during the day.At urban sites, the AUHII is greater than that found at rural sites.At Kukas, a negative AUHII of −2.20°C indicates that at Kukas, the atmospheric temperature is lesser than the corresponding Sitapura temperature.

Night period.
At the PGIS location, a peak AUHII of 3.90°C was measured, whereas Kanwar Nagar displays a peak SUHII of 3.80°C, while utilizing Terra surface temperature data.The AUHII varies from 0°C to 3.90°C, while for Terra LST data, the SUHII varies from 0°C to 3.80°C.For urban sites, both the AUHII and SUHII are greater than the rural sites.10:30 PM (23.15°C), respectively, were taken as the base LSTs for SUHII determination.The atmospheric temperature reported at Benad at 10:30 AM (28.1°C) and 10:30 PM (24.1°C) was taken for AUHII computations for the day period and night period, respectively.4.2.2.1.Day period.During the daytime, Kanwar Nagar exhibits the lowest SUHII of −2.40°C which obviously indicates the presence of negative or inverse SUHI effect in the studied region.Similarly, when using MODIS day LST results, most sites display negative SUHII varies from −0.40°C to − 2.40°C.This clearly depicts that during the daytime period, inverse or negative SUHI occurs in the research region while using LST.When analyzing daytime air temperature data, most of the sites show positive AUHII fluctuating between 0.90°C and 2.70°C, which clearly supports the AUHI influence on the study region during the day.With the exception of Kukus, a rural site that shows an AUHII of −0.40°C, the majority of the sites exhibit positive AUHI impacts.

Night period.
At the Vaishali spot, a maximum AUHII of 3.4 K was noted, whereas Kanwar Nagar displays the peak SUHII of 2.60°C while utilizing Terra LST.The AUHII varies from zero to 3.40°C, while for Terra data the SUHII varies from −0.20°C to 2.60°C.Both SUHII and AUHII are much higher at the three urban locations than they are at the corresponding rural sites.The single exception is PGIS, where the level of AUHII is at peak, while the strength of SUHII is almost zero.This could be due to the effect of the predominant wind direction.

Winter season
Table 6 displays the air and surface temperature values of different sites during the winter season at the time of satellite passage.In Benad, a minimum air temperature of 9.2°C was reported, and UHII was determined with respect to the Benad temperature.The daytime and nighttime surface temperatures provided by MODIS at 10:30 AM (24.65°C) and 10:30 PM (8.05°C), respectively, are used as reference LSTs for SUHII measurements.The atmospheric temperatures measured at Benad at 10:30 AM (16.1°C) and 10:30 PM (9.2°C), respectively, were used to determine the daytime and nighttime AUHII computations.

Day period.
The MODIS daytime data show that MNIT has the lowest SUHII of −40°C, clearly showing that the research region has an inverse or negative SUHI impact.Similarly, while using MODIS daytime surface temperature data, most of the study regions exhibit negative SUHII varies from −1.30°C to −4.0°C.This clearly demonstrates that during the daytime period, inverse or negative SUHI happens in the study region, while using LST.In comparison, most of the study regions display positive AUHII variations from 0°C to 5°C when using daytime atmospheric temperature data that evidently demonstrates the AUHI effect on the research region during the day.

Night period.
Most locations in the research area display positive SUHII and AUHII during both times.At the PGIS site, a peak AUHII of 3.70°C was recorded, whereas Kanwar Nagar exhibits a peak SUHII of 5.30°C when using Terra surface temperature data.The AUHII varies from −0.80°C to 3.70°C, while for Terra LST data, the SUHII varies from −0.90°C to 5.30°C.Kanwar Nagar, which falls within Jaipur city's CBD, experiences the highest nighttime SUHI and AUHI intensities.

Discussions
The SUHI level at urban locations during the day is negative, as shown by the aforementioned data, since rural areas have a higher surface temperature than urban sites, creating an Urban Cool Islands (UCI) (Mishra & Mathew, 2022).Several factors contribute to the UCI phenomenon.Increased vegetation and green spaces, as well as the shading effect of buildings and trees, can help reduce daytime temperatures in urban areas.Additionally, differences in the thermal properties of various surfaces within cities can lead to cooler conditions during the day (Gupta et al., 2020).However, the same UCI effect must also be seen in AUHII.However, AUHII differs from SUHII throughout the day, and the urban locations show higher air temperature than the rural sites.If night-time data is taken into consideration for urban sites, both the SUHII and AUHII are greater than the rural sites.Peak AUHII and SUHII are found in one or more urban sites (mostly at the position of the city's CBD).AUHII and SUHII are also greater at other urban sites.Similar diurnal SUHI and AUHI effects are seen during all three seasons.SUHI is more noticeable at night, hence it was thought to be a phenomenon that only occurred at night and was not as common during the day.Both during the day and at night, AUHI was recorded.During the daytime across the study region, strong incidence of AUHI and non-occurrence of SUHI were seen by the field survey analysis, however strong AUHI effect and SUHI effect were observed during the night-time.A significant diurnal AUHI impact was seen in the study area, indicating that the urban area is significantly warmer than the rural area.SUHI has a negative or disastrous effect on certain cities because of variances in the thermal characteristics of different terrain surfaces on Earth.These temperature differences can have significant implications for local climate, energy consumption, public health, and urban planning.This phenomenon is primarily attributed to the alteration of land surfaces, human activities, and the modification of the natural environment within cities (Arnfield, 2003;Badugu et al., 2023aBadugu et al., , 2023b)).SUHI is typically not evident throughout the day.A number of SUHI studies employed Daytime LST data.SUHI varies during the day, and at night or in the evening it is more noticeable.

Diurnal differences of SUHI and AUHI influence using in-situ field temperature recordngs
In-situ field surveys were done at seven sites throughout the Jaipur research area to analyse diurnal fluctuations in the temperatures of various land covers and to evaluate the AUHI and SUHI impacts.

Diurnal differences of temperatures of various land covers for various seasons at seven sites of Jaipur
Daytime and night-time LST investigation for Jaipur study area reveals differing thermal patterns during the day and at night.In these cities, the nocturnal SUHI impact has been seen, and the majority of urban regions have greater LSTs than non-urbanized locations.The average LST in the urban region is approximately 3.0 K greater than the average LST in the non-urbanized region.The highest SUHI intensity, which corresponds to the urban area's maximum LST and the rural region's least LST, is 12 K.The day LST profile, on the other hand, appears to be distinct from the night LST pattern.In Jaipur, the day LST profile reveals a negative or inverse SUHI effect.The LST spatial patterns reveal a thermal profile with a wide range of temperature changes on the surface.The SUHI impact has been observed in several prior SUHI investigations in different cities during the day.Daytime SUHI intensity was also found to be greater than night-time SUHI intensity.In this study, the SUHI effect was found to be absent during daytime.Over the research region throughout the day, an inverse SUHI influence was shown, with rural parts having higher LSTs than urban regions.However, a strong SUHI effect was noticed over the research region at night.This section examines the thermal behaviour of various surface cover materials and plots the thermal pattern of various land coverings using the in-situ temperature data.

Monsoon Season.
Figure 5 depicts the temperature pattern of different land covers at seven sites during the monsoon period.
The diurnal LST readings of several land materials show that there are considerable differences in LSTs during the day (Al-Tamimi et al., 2022).The variance in LSTs at night is, however, far lesser than during the day.Large fluctuations in temperature are observed on various land surfaces during the monsoon season as a result of dispersed clouds blocking sunlight from reaching some areas, which casts shadows over those areas.Due to the shadow effect, LST will fluctuate across similar surfaces that receive various solar radiations at the same time.
Soil has been found to have greater LST than urban materials such as concrete and bitumen, particularly when the sky is clear, and the sun is shining brightly.Increased soil surface temperature has been reported for various measurements at Kanwar Nager, PGIS, MNIT, and Kukas, especially during the day, when compared to concrete and road.During the day, the temperature of the road at Sitapura and Vaishali Nagar was reported to be greater than the temperature of the soil and concrete.Because of the cloud cover in Benad, the temperature of the asphalt and concrete is greater than the temperature of the soil.Thermal inertia, one of the primary surface properties that defines surface features, has been observed to have a considerable influence on surface temperature variations due to the dispersed cloud cover during the monsoon season.There have been reports of dramatic temperature changes on various surfaces in some locations when clouds block sunlight.In contrast to concrete and roads, soil cools quite fast when cloud cover develops.Built-up materials like bitumen and concrete take far longer to cool than soil does.Compared to concrete and bitumen, soil has a low thermal inertia.This explains the huge differences in soil temperatures seen at Kanwar Nagar, PGIS, MNIT, and Kukas.During the day, significant differences in LSTs for various land covers were reported, which are substantially greater than those found at night.Numerous factors, such as cloud cover, shadow, location, and wind speed, can affect the temperature of different land surfaces (Donateo et al., 2023;Gupta et al., 2020).With the exception of shadow caused by cloud effects, all observations were made at locations open to the sky and far enough away from other structures or objects of height to eliminate the effect of shade on surface temperature measurements.
The charts show that vegetation had the lowest minimum peak temperature and the lowest overall minimum temperature of all the surfaces studied.During the monsoon season, the difference in the highest and lowest temperatures of flora cover ranges by around 7.53°C to 20.84°C for seven sites.The temperature range between the highest and lowest points of other surfaces dramatically changes during the monsoon season, ranging from 15.84°C to 28.50°C and 19.28°C to 30.31°C for cement concrete and road covers, respectively, over a 27-h period.During the monitoring period for seven sites, the variance in the highest and the lowest soil temperatures ranges by around 22.39°C to 27.62°C during the monsoon period.This indicates that vegetation has the effect of moderating temperature variations, and regions with good flora should have a lesser temperature than spaces with no green cover, sparse flora, or any other type of built-up land.
Soil, vegetation, roads, and concrete had absolute maximum surface temperatures of 52.78°C, 45.10°C, 57.96°C, and 53.30°C, respectively.Soil, vegetation, roads, and concrete had absolute minimum surface temperatures of 23.83°C, 22.70°C, 26.03°C, and 24.80°C, respectively.During the monsoon season, the temperatures of various land covers were reported in the following order ranking from the highest to the lowest: roads > concrete cover > soil cover > vegetation cover.
The highest road LST of 57.96°C was recorded at 1:30 PM at Vaishali Nagar; the road's LST was around 6.00°C and 7.50°C over the temperatures of the soil cover and cement concrete covers, respectively, and it was nearly 20.00°C above the LST of flora, as shown in the monsoon season chart (Figure 5).In Benad, the highest concrete LST of 53.30°C was recorded at around 2:00 PM.This temperature was around 1.00°C and 6.00°C higher than that of the roadways and soil covers, respectively, and about 16.00°C higher than that of the vegetation.At Kukus, the highest soil LST of 52.78°C was recorded at approximately 1:30 PM.This value is equivalent to the corresponding road and soil cover LSTs with a smaller variation, and it is around 18.00°C higher than the LST of vegetation.
As the sun rises, the LST of all land surfaces begins to rise, and this increase in LST continues until the moment of peak sun radiation.During the period of observation, the temperature of all land covers, except flora, alters in tandem with each other, and the LST of all land covers is significantly greater than that of flora.The highest LST of all land covers was recorded between 12:00 Noon and 3:00 PM, which is when sun energy is at its highest.After the peak solar radiation, the LST of all surfaces begins to decline.The temperature drops throughout the night and begins to increase with sunrise the succeeding day.
According to the in-situ LST investigation, soil warms up quickly in the presence of solar radiation and cools down quickly in its absence.During the season's peak daylight hours, the soil LST is even greater than the LST of the road/concrete surface.Up until around 3:00 PM, soil has a higher temperature than other materials, and then the temperature begins to fall under clear sky conditions.When compared to other materials, the rate of cooling of soil is the fastest.The crossing time of soil LST with regard to concrete and road surfaces is not significant due to the undulations in the soil LST pattern brought on by cloud cover during the monsoon season.For all sites, it was noticed that concrete and roads have greater LSTs at night than soil cover.For all sites, the surface temperatures of concrete and roads are nearly identical, with fewer differences.Also, for all areas, soil and vegetation display a similar LST pattern with fewer changes at night.As a result, at night, the thermal profiles of all land surfaces are comparable and less variable.Hence, temperature fluctuations over all land covers are nearly constant at night.It is obvious from the figures that during the night, comparative variances in LSTs appear to be consistent across all land surfaces.
During the observation period (monsoon season), the maximum and minimum air temperatures in Vaishali Nagar and Benad were 35.93°C and 21.40°C, respectively.Table 7 indicates air temperatures in seven distinct places at various times.The seven places' highest and minimum air temperatures are shown in red and green, respectively, at any given time.Vaishali Nagar and Kanwar Nagar have the highest night-time atmospheric temperatures, while Benad has the minimum night-time atmospheric temperatures.During the day, Vaishali Nagar and Sitapura (rural regions) have greater atmospheric temperatures, while Benad, Kukas, and PGIS (rural regions) have minimum atmospheric temperatures.

Winter Season.
Figure 6 indicates the temperature pattern of different land covers of seven sites during the winter period.
Greater air and surface temperature variations are seen during the day than at night during the winter season.During the day when the sun is at a higher height, it has been observed that soil temperature in clear sky conditions is much higher than road and concrete temperature.It was also noticed that newly constructed roads had higher LSTs than older roads because fresh black bitumen catches and holds more heat than aged black brown bitumen.Because the vegetation is drier/scarce in Kukas and MNIT, throughout the day, the temperatures of the flora are practically identical to the soil temperatures.It displays that vegetation spectral reflectance pattern is comparable to that of bare earth.As a result, the surface characteristics of various materials differ and have a substantial impact on surface temperature changes.
The difference between the highest and lowest LSTs of the vegetation varied from around 17.28°C to 30.70°C in the winter over the seven monitoring locations.For cement concrete, roadways, and soil covers, respectively, the range between the maximum and minimum LSTs varies significantly over the assessment period, ranging from 18.18°C to 31.35°C, 19.00°C to 41.89°C, and 27.00°C to 44.04°C.
The maximum LSTs for soil, vegetation, roadways, and cement concrete throughout the monitoring period were 44.20°C, 32.90°C, 43.82°C, and 35.10°C, respectively.The minimum LSTs for soil, vegetation, roads, and concrete were 2.55°C, −2.0°C, −1.73°C, and 1.93°C, respectively.When related to other land covers during the winter period, soil exhibits the highest absolute LST during the day and the lowest absolute LST during the night.
Up until around 4:00 PM, soil has a higher temperature than other materials, and then the temperature begins to fall under clear sky conditions.
As shown in Figure 6, the maximum LST of road, 43.82°C was recorded at about 1:30 PM at the Vaishali Nagar site for the winter season.The LST of road was about 14.04°C and 8.72°C higher than the temperatures of vegetative cover and concrete surfaces, respectively, and it was about 0.38°C lower than the LST of soil cover.The maximum LST for concrete, 35.10°C, was recorded in Vaishali Nagar at 2:00 PM.This LST was 5.32°C higher than the LST of vegetation and was 8.72°C and 9.10°C lower than the LST of the road and soil covers, respectively.The greatest soil temperature of 44.20°C was recorded in Vaishali Nagar at 1:30 PM, which was around 0.38°C and 9.10°C higher than the LST of the concrete and road, respectively, and about 14.04°C higher than the LST of the vegetation.
Table 8 indicates air temperatures in seven distinct places at various times.Kukus has a maximum air temperature of 25.65°C and a minimum air temperature of 2.25°C during the winter season.The thermal profile of various materials varies consistently during the night.The surface temperatures of the road and concrete are higher than those of the soil and green cover.It was noticed that the LSTs of both soil and green cover are nearly same at night.LSTs of both soil and flora have been reported to be negative in the PGIS area.The temperature of the air throughout the night has been reported to be greater than that of the soil and vegetation cover.The temperature patterns of concrete and roads are nearly the same, with fewer fluctuations at night.Temperatures were reported to be steadily lowering until 6.30 a.m., with less volatility during the night.
After sunset, the soil temperature is substantially lower than that of other built-up covers, and it is similar to that of flora.The LST of soil is significantly lower in the winter than the LST of vegetation.It can therefore be concluded that soil cover typically experiences rapid warming during the hottest part of the day, when the sun is directly above it, and rapid cooling during the absence of solar radiation.By separating the graphs in Figure 7 into two-halves, they can be analysed more thoroughly.The first component should be examined between the hours of 8:00 AM and 5:00 PM.This period refers to the  hours of sunlight.After 5:00 PM, in the evening and before 8:00 AM, in the morning, the second portion can be regarded.As the sun rises in the morning, the LST of all land surfaces begins to rise, and this increase continues until the moment of peak sun radiation.The maximum LST of all land covers was recorded between 12:00 Noon and 3:00 PM, which is when the sun's energy is at its highest.After the peak solar radiation, the LST of all land surfaces begins to decline.The temperature drops throughout the night and begins to rise again after sunrise the next day.

Summer Season.
During the day, soil gets hotter than urban covers such cement concrete, bitumen, and so on, and during the night, urban covers display greater LSTs than soil and vegetation cover, according to an in-situ LST analysis of diverse surfaces during a 27-h period.
During the summer day period, the LST of various land covers was measured in the following order: soil cover > roads > concrete cover > vegetation cover.During the summer period, the following order was seen at night: road and concrete cover > soil cover > vegetation cover.This order changes during the monsoon and winter period to concrete > roads > soil cover > vegetation cover during the day and roads > concrete cover > soil cover > vegetation cover during the night.
During the monitoring hours for seven sites, the difference between the highest and the lowest LSTs of green cover varied by around 18.20°C to 24.92°C during the summer period.During the monitoring hours, the LST difference between the peak and minimum of other land covers varied greatly, ranging from 28.40°C to 37.48°C, 30.20°C to 43.78°C, and 40.94°C to 45.29°C for cement concrete, roads, and soil covers, respectively.In comparison to other seasons, the summer season has a substantial variation in the LSTs of various surfaces.
During the monitoring period, the absolute highest LSTs of soil, vegetation cover, roads, and concrete were 72.48°C, 51.80°C, 70.58°C, and 68.50°C, respectively.Soil, vegetation cover, roads, and concrete had the absolute lowest surface temperatures of 24.40°C, 24.80°C, 26.80°C, and 36.64°C,respectively.When compared to other land covers throughout the summer period, soil exhibits the highest absolute LST during the day and the lowest absolute LST during the night.
Up until around 4:00 PM, soil has a greater temperature than other materials, and then the temperature begins to fall under clear sky conditions.
The maximum road LST of 70.58°C was measured at about 2:00 PM at Vaishali Nagar, and the road's LST was about 18.78°C and 4.35°C greater than the temperatures of green cover and cement concrete, respectively, and it was about 1.11°C greater than the LST of soil cover, as shown in the chart for the summer season (Figure 7).At MNIT, the highest concrete LST of 68.5°C was observed about 3:00 PM, which was about 1.62°C lesser than the LST of the soil cover and around 20.48 °C and 1.26°C greater than the LST of the green cover and the road.At Benad, the highest soil LST of 72.48°C was measured at 2:00 PM, which was about 23.56°C, 7.41°C, and 9.9°C greater than the LSTs of green cover, roads, and cement concrete covers, respectively.
Table 9 depicts atmospheric temperatures at seven diverse places at various times.At Benad and MNIT, the absolute higher and lower atmospheric temperatures were 48.8°C and 27.00°C, respectively.Concrete and road LSTs were found to be greater than soil LSTs at all sites during the night.During the night, the thermal profile of road and concrete surfaces is comparable, and the LST of road and concrete covers is nearly identical.During the night, air temperature was found to be quite close to vegetation cover and soil temperatures.The lowest temperature is found in the vegetation at night, but it is usually very close to the soil temperature.Up until about 7.30 AM, the soil LST was lower than the road and cement concrete temperatures.After this time, soil surfaces have a greater LST than other land surfaces such as roads, concrete, vegetation, and so on, until around 4 PM, when sun radiation begins to decrease.Due to the lengthy daytime clear sky conditions and intense solar radiations during the summer season, open soil covers have greater LSTs than other land surfaces for a longer period of time than other seasons.During the day, diverse materials absorb and retain solar energy, which is subsequently released at night.Consequently, the intensity of SUHI is notably elevated during nighttime (Abutaleb et al., 2015).4.4.1.4.Discussions on in-situ temperature recordings for various seasons.During the day, significant variations in temperature between various land covers have been noted (Al-Tamimi et al., 2022;Gupta et al., 2020).During the day, soil absorbs more heat and displays a greater LST than built-up materials such as concrete and bitumen.As a result, land surface temperatures in rural locations (where soil/ sparse/dwarf/drier flora covers are more common) are greater than in urban regions (where concrete structures or buildings and highways predominate) (Mathew et al., 2018).Urban building materials like stone, concrete, and asphalt absorb and retain heat during the day.In order to maintain ambient thermal homeostasis after sunset, these urban materials gradually release this heat, resulting in the SUHI effect at night.SUHI can therefore be categorized as a nocturnal or night-time occurrence.
The season has an effect on the surface temperature changes of diverse land covers, according to the seasonal analysis (Chen et al., 2012).Due to the existence of cloud cover throughout the monsoon season, the thermal pattern of the soil fluctuates inconsistently.Because soil has a lower thermal inertia than other land surfaces, it cools quickly when cloud cover appears.In the absence of cloud cover, soil warms up more quickly than other land surfaces.The surface and air temperatures measured during the winter period are less than those recorded during the monsoon period.
In all seasons, there are fewer changes in the thermal patterns of different types of land cover at night.At night, soil and vegetation have lower LSTs than built-up areas like highways and concrete in all seasons.Urban surfaces are more thermally conductive and capable of storing more heat than rural ones, and they release more of that heat at night.Additionally, urban surfaces absorb more solar energy than rural ones do.Variations in the thermal characteristics of the radiating surfaces lead to an increase in the amount of sensible heat stored in the city's infrastructure.In light of this, data collected at night are preferred over data collected during the day for the SUHI study.Although using remote sensing techniques for SUHI research has several advantages, it is crucial to note that the calculated temperatures are the LSTs of the emitted materials, which differ from the in situ observed ambient temperatures.The availability of different land surface types in the urban setting results in significantly larger regional variance in surface temperatures than in concurrent atmospheric temperatures (Mathew et al., 2022;Streutker, 2002).
Flora has the lowest LSTs during the day and night and has a constant thermal pattern throughout all observations, acting as a cooling medium both during the day and at night.The soil's thermal profile varies both throughout the day and at night.When the sky is clear throughout the day, soil has higher  LSTs than vegetation and the built-up areas.The lowest temperatures are found in the soil and on the vegetation, while built-up surfaces have higher LSTs at night.

Correlation of change in temperatures of different land surfaces with respect to time
For each season, the differences in soil cover and roads or concrete covers LSTs at various periods were plotted (Figures 8 and 9).In the winter, the research locations' differences in LST between soil and road range from −6.60°C to 18.00°C, while those between soil and concrete range from −8.68°C to 15.65°C.If the difference is positive, it means that soil has a greater LST than other types of land covers, whereas if it is negative, it means that soil has a lower LST than concrete or other hard surfaces like roads.While the LST difference between soil and concrete varies from −15.00°C to 8.09°C during the monsoon season, it ranges from −11.52°C to 7.04°C for soil cover.For the summer season, the temperature difference between soil cover and roads varies from −11.64°C to 12.10°C, whereas the temperature difference between soils cover and cement concrete varies from −13.92°C to 13.69°C.
The highest positive difference between the LST of soil cover and concrete cover during the summer, monsoon, and winter seasons ranged from 5.37°C to 13.69°C, 0.20°C to 8.09°C, and 3.40°C to 15.65°C, respectively.The highest positive difference between LST of soil cover and roads or concrete was observed between the time period 12.30 PM and 3.00 PM.
The maximum negative difference between the LST of the soil and the road was observed to vary from −11.64°C to −6.82°C, −11.52°C to −5.15°C, and −6.60°C to −2.32°C, respectively, for the summer, monsoon, and winter seasons.
During sun-off hours, a negative differential in temperature between the soil and the road or concrete was noted.Between 1.30 AM and 6.30 AM, the highest negative difference between soil cover and roads or concrete LST was found.
As shown in Figures 8 and 9, time is the main factor determining the difference between soil and concrete or road LSTs.In most regions, the variation in LST between urban surfaces and soil throughout the night is less variable.However, during the day, a sizable variation in LST between natural and built-up regions has been observed.Different types of land surfaces behave differently thermally during solar peak hours than they do at night when there is no sunlight (Mathew et al., 2018).It has been shown that soil has a higher thermal profile than urban materials like cement, concrete, asphalt, and so on throughout the summer and winter seasons and that urban materials have a higher temperature pattern than soil and vegetation at night.It has been observed that throughout the monsoon and winter seasons, the temperature differential between the earth and the road or concrete is more consistent at night than during the day.That is, there are significant daytime changes in the temperature differential between the soil and the road or concrete.The crossover time when the soil temperature starts to decrease is extended during the summer period compared to the winter period, according to insitu surface temperature studies for various land cover materials.
During the day, bituminous roads have greater LSTs than concrete and lower LSTs than barren soil.Almost everywhere, soil has somewhat higher LSTs than the roads, particularly during the day.In Vaishali Nagar, the difference between soil cover and road's LST was reported to be negative during both seasons, indicating that the bituminous roads had slightly greater LSTs than the soil cover.Newly constructed roads have greater LSTs than older roads.In all other places, the difference between soil cover and road LST is seen to be positive during the summer period with clear skies and to be negative at other times of observation, particularly during the monsoon season with cloud cover circumstances.During the night, all sites show negative values for the difference between soil cover and road LST in all seasons, indicating that soil has far lower LSTs than the road.As a result, the preceding figures clearly show diurnal thermal behaviour of soil.UHI effects, including SUHI and AUHI, exhibit complex diurnal patterns and have far-reaching consequences for urban areas.Understanding these patterns and their underlying causes is essential for designing resilient, sustainable, and livable cities. Urban planners, policymakers, and researchers must consider these variations to develop effective strategies for mitigating UHI and improving the quality of life for urban residents.Additionally, addressing UHI can contribute to broader climate change adaptation efforts by reducing energy consumption and greenhouse gas emissions in urban environments.

Conclusion
The study conducted in Jaipur city reveals significant insights into the dynamics of UHI, specifically the SUHI and AUHI effects, their diurnal variations, and the impact of land cover types.It was observed that SUHI tends to be more noticeable at night, while AUHI occurs both during the day and night.This highlights the importance of considering nighttime data for SUHI analysis and understanding the distinct patterns of UHI effects throughout the day.
• An in situ temperature survey was performed at seven spread points within the research region of Jaipur city, to analyze the temperature profile of various land covers at these sites as well as to relate the effects of SUHI and AUHI.
• At the time of the satellite transit, AUHI and SUHI strengths were determined (10.30AM and 22.30 PM).The UHII was determined as to where the lowest atmospheric temperature was observed at 10:30 PM.The mean maximum SUHII temperatures for the summer, monsoon, and winter are 8.39°C, 6.83°C, and 9.60°C, respectively.The average SUHII during the experiment was 8.50°C.
• Positive AUHII was noticed at most of the sites irrespective of time.Positive SUHII was identified at most places at night, but negative or inverse SUHII was seen during the day at most locations.While there was an inverse link between AUHI and SUHI during the day, there was a direct relationship between the two throughout the night.AUHI was observed both during the day and at night.Our study shows that the use of daytime images for SUHI analysis mostly depends on the land surface covers and may present different effects that may not be the same as the AUHI effect.
• Regardless of the season, different land coverings' thermal patterns vary less at night.In all seasons, night-time LSTs are lower for soil and vegetation than for built-up areas like highways and concrete.
• Urban surfaces can release more heat that has been absorbed throughout the day at night because they have higher thermal conductivity and storage capabilities than rural land coverings.The amount of sensible heat trapped in the city's structure increases as a result of the differences in the thermal characteristics of the radiating surfaces.Therefore, night-time data is preferable above daytime data for SUHI study.
• Flora has the lowest surface temperatures during the day and night and has a constant thermal pattern throughout all observations, acting as a cooling medium both during the day and at night.The soil's thermal profile varies both throughout the day and at night.When the sky is clear throughout the day, soil has higher LSTs than vegetation and the built-up areas.The lowest temperatures are found in the soil and on the vegetation, while built-up surfaces have higher LSTs at night.
• All three seasons exhibit similar diurnal SUHI effect and AUHI effect.The SUHI effect is more obvious at night, i.e.SUHI can be considered as a night-time phenomenon, and is not considered predominant in the daytime.AUHI was noticed in daytime and at night.Strong occurrence of AUHI and nonoccurrence of SUHI was ascertained through the field survey analysis during the daytime period over the study region, while strong presence of both SUHI and AUHI was noticed at night.
• Substantial diurnal AUHI effect was noticed in the study region concluding that the urban region is warmer than the rural region.Due to differences in the thermal properties of various land coverings on Earth, SUHI was reported to have an adverse or detrimental influence in some cities.SUHI is typically not evident throughout the day.A number of SUHI investigations employed daytime LST data.SUHI varies during the day, and at night or in the evening, SUHI is more noticeable.
• To mitigate Urban Heat Island (UHI) effects in the future urban planning for Jaipur City, several recommendations should be considered.First, prioritize the incorporation of green spaces, parks, and vegetation into urban development to increase shade and cool the environment.Secondly, promote cool roofing and green roofing technologies to reduce heat absorption by buildings.
Implementing cool and reflective surfaces on roads and pavements can also help.
• Additionally, encourage sustainable transportation options and reduce reliance on personal vehicles to decrease heat emissions.Finally, ensure urban planning integrates climate-resilient designs that consider local climatic conditions, aiming to reduce heat stress on residents while enhancing the overall quality of life in the city.
• The results of the study provide insights into the spatial and temporal patterns of the UHI effect over Jaipur City.The study identified the areas of Jaipur city that are most vulnerable to the UHI effect and the times of day and seasons when the UHI effect is most severe.
• This study evaluates the potential of remotely sensed data in monitoring the diurnal UHI effect and provides recommendations for urban planners and policymakers to mitigate the UHI effect in Jaipur City.Overall, the study will contribute to the understanding of the UHI effect and its impacts on urban environments, and provide a basis for future research in this area.
This study offers valuable guidance for addressing UHI effects in Jaipur City and contributes to the broader understanding of UHI dynamics in urban environments.It emphasizes the importance of considering both SUHI and AUHI, leveraging nighttime data, and adopting sustainable urban planning practices to create more livable and resilient cities.
Figure 1.Geographical location of the study area.

Figure 2 .
Figure 2. Google Earth© map of the Jaipur research region.

Figure
Figure 4. Spatio-temporal variation of average LST over Jaipur.
Assessment of atmospheric and SUHI effect on Jaipur city during the monsoon

Figure
Figure 5.Diurnal variations in surface and atmospheric temperatures at different locations in Jaipur (monsoon period).

Figure
Figure 6.Diurnal differences of surface and atmospheric temperatures at various sites of Jaipur (Winter period).
Figure 7 displays the temperature pattern of different land covers of seven sites during the summer period.

Figure
Figure 7.Diurnal differences of surface and atmospheric temperatures at various sites of Jaipur (Summer period).

Figure 8 .
Figure 8. Variance in temperature vs.Time between Winter and monsoon periods.

Figure 9 .
Figure 9. Variance in temperature vs.Time between Summer and monsoon periods.

Table 1 .
Date and time of the field recordings

Table 5 .
Table5presents the atmospheric and surface temperature values during the monsoon season at the period of satellite passage at various sites.At Benad, the lowest atmospheric temperature of 24.1°C was noticed, and UHII was measured with respect to the Benad temperature.The MODIS generated day period and night period surface temperatures noticed at 10:30 AM (34.05°C) and