SPATIO-TEMPORAL ANALYSIS OF URBAN HEAT ISLAND USING LANDSAT 8 OLI/TIRS IMAGERY IN KLATEN DISTRICT IN 2013 – 2021

Klaten Regency is one of the areas that has experienced changes in use over time, such as agricultural land becoming built-up or non-agricultural land. This has an impact on the increase in air temperature which can lead to the occurrence of the phenomenon of the Heat Island or Urban Heat Island. This study aims to determine the spatio-temporal variation of vegetation index value (NDVI), Surface Temperature and in Klaten Regency in 2013 - 2021 and determine the relationship between vegetation index value (NDVI) and UHI in Klaten Regency. The method used in this research is Landsat 8 image data processing such as NDVI, LST and UHI calculation to get the final result. Meanwhile, to get the relationship between NDVI and Surface Temperature related to the UHI phenomenon, simple regression testing was carried out. The results obtained from the processing results show that Klaten Regency is dominated by vegetation cover density with very high and high classifications despite the decrease in area from 2013 to 2021. Surface temperature in Klaten Regency is dominated by surface temperatures within the range of 25 - 28 o C spread across the entire region from 2013 to 2021. The results of the linear regression have a coefficient value of r2 where the value shows results with a value of 0.377. The result of the coefficient of determination shows that the amount of influence obtained from the density of vegetation land cover with an average surface temperature of 37.7% where other factors can influence the rest.


Introduction
Heat island or commonly referred to as Urban Heat Island (UHI) is a phenomenon that is increasingly appearing over time due to continuous development.This also occurs due to the impact of reduced vegetation land which causes reduced absorption of heat energy from the

International Journal for Disaster and Development Interface
IJDDI 2024, 4, 1, 2 http://ijddi.netsun so that the temperature in the area affected by the phenomenon of the Bahang Island increases slowly.The presence of vegetation in an area is related to the formation of the island, where CO2 is absorbed by vegetation less and less due to the continuous reduction of vegetation land.This results in an imbalance of air in the region.The conversion of vegetation land into facilities such as settlements or industrial sites reduces the balance of air composition, which has a serious impact on temperature increases that can increase up to 10o C -20o C from the ambient air temperature (Sadeghian and Vardanyan, 2013).
Klaten Regency is one of the areas that has experienced land use changes from time to time, such as agricultural land becoming built-up or non-agricultural land from 2013 of 33,375 Ha reduced in 2021 to 31,943 Ha.Agricultural land is generally defined as land that functions as a cultivation development of various varieties of vegetation, so agricultural land can also be interpreted as agricultural land, so that the reduction in agricultural land is the cause of the reduction in vegetation land varieties.Vegetation is one of the important factors for the fundamentals of an environment, this is because vegetation is able to regulate the flow of a number of biochemical cycles such as water, carbon and nitrogen which are useful as local and global energy balancers.In addition, vegetation has benefits as a view controller, climate controller, erosion controller, place of life (animal habitat), and has aesthetic value (Carpenter, 1975).
Klaten Regency as a strategic area which is located between two major cities, namely the city of Yogyakarta and the city of Surakarta, makes the Klaten Regency area has activities that lead to an increasing land.From the existence of these two historic cities, Klaten Regency is a link between the two so that this creates an impetus for people to live in the Klaten area, so that from this it also makes the Klaten area have a fairly rapid increase in population from year to year, namely from 2013 to 2021 there was an increase as much as 118,278 people.An increase in population has both positive and negative impacts on an area.The increasing population in an area makes the needs of human resources in the area more fulfilled, but on the other hand it also has an impact on vegetation land which is decreasing due to the needs of population activities which also increase, thus making a change in land from vegetation to built-up land.Land use continues to increase, resulting in a phenomenon called the island of Bahang.The phenomenon of the island of heat is a phenomenon that occurs due to the overcrowding of a building so that the air temperature in areas with higher building levels has a higher temperature than the air temperature in other areas (Mukmin, 2016).
Urban Heat Island can be identified using remote sensing techniques such as NDVI (Normalised Difference Vegetation Index) and LST (Land Surface Temperature) calculations.
NDVI calculations are carried out to obtain vegetation index data while LST calculations are used to obtain temperature data in the Klaten Regency Area.The ease of obtaining image data for NDVI and LST calculations is an opportunity for spatio-temporal-based remote sensing analysis in this study, where the data used uses Landsat 8 data in 2013 and 2021.From some of the calculation results, the results can be concluded in the form of a relationship between surface temperature and vegetation land changes that occurred from 2013 to 2021 in the Klaten Regency Area.

Materials and method
The sampling method used in this research is stratified random sampling, where this method is carried out by random sampling but is still adjusted to the strata or division of the population so that the samples taken do not overlap with each other.The number of samples taken in this method is determined using the Fitzpatrick-Lins formula (McCoy, 2005: 21-22), where the number of samples will be divided into 51 points spread according to the method used, namely stratified random sampling.Sampling in the form of vegetation density data at selected location points and taken randomly, the results of the vegetation density data collection are used as an accuracy test by comparing the results of image processing to whether they are appropriate or not.
The image processing method is carried out to obtain data results in the form of NDVI classification and LST classification.While the survey method is intended as an accuracy test of the results of image processing that has been done.In addition, there are several stages of data processing in this research such as:

a. Image Cropping
The image cropping process is needed so that the image boundaries match the administrative boundaries of the Klaten Regency Area.

b. Radiometric Correction
Radiometric correction is a basic correction on an image that is done to remove IJDDI 2024, 4, 1, 4 http://ijddi.netnoise contained in an image, this method can be done with the Top of Atmosphere Regression test is used to get the relationship between one variable and another.

Results and Discussion
Image processing was carried out from 2013 to 2021 where there is a period of every 2 years.From the results of the processing carried out, it was found that Klaten Regency was dominated by very high and high vegetation cover density.This shows that the quality of vegetation distribution in Klaten Regency is still good since 2013 even though there is always a reduction from time to time.This can be seen in the extent of the classification level of vegetation land cover density or very high NDVI where in 2013 the area was 303.3 km 2 while in 2021 the area decreased very significantly where only 213.5 km remained 2 .From this, it can be concluded that although Klaten Regency is still dominated by vegetation cover density with high and very high classifications, the visible land loss is quite worrying about the existence of Klaten Regency vegetation in the years ahead if something like that continues to happen which of course will have many adverse effects on Klaten Regency itself such as the expansion of the Urban Heat Island phenomenon in Klaten Regency.The results of UHI distribution data are obtained from LST data processing which is reduced by the threshold value to determine the difference in areas affected by UHI or not affected.The threshold value is the average value of each surface temperature so that each image has an unequal threshold value.The distribution of UHI in Klaten Regency in 2013 showed that the UHI phenomenon occurred in only 26% of the total area of Klaten Regency.
In 2013 the UHI phenomenon that occurred tended to be in the low class UHI with an area reaching 179.5 km 2 with a maximum temperature increase of 3.7 C. o The distribution of areas affected by the UHI phenomenon in 2015 in Klaten Regency was 28% of the total area of Klaten Regency where there was an increase of 2% from 2013.
The classification of low-class UHI that occurred in Klaten Regency was 180.5 km 2 which was spread across all sub-districts in Klaten Regency.Similar to 2017 which was dominated by low-class UHI with a total area of 184.27 km 2 .Overall, the Klaten Regency area in 2017 experienced the phenomenon of a heat island or UHI of 27% of its total area, of which 95% was dominated by low-grade UHI.
The distribution of areas affected by the UHI phenomenon in 2019 in Klaten Regency totalled 28% of its total area, this is exactly the same as what happened in 2015.Just like in the following year, the largest UHI classification to be impacted in the Klaten Regency area is the type of low-class classification with a total area of 181.25 km 2 .Then the type of UHI class classification that is the largest in Klaten Regency in 2021 is the same as in previous years, namely the low-class UHI classification with a total area affected in the Klatena Regency area of 203.7 km 2 where this has increased by more than 20 km 2 than in 2019.Calculations to determine the relationship between vegetation cover density and surface temperature to determine the relationship to the phenomenon of bahang island here using simple linear regression.Where the calculation uses 2 variables, namely the independent variable (X) and the dependent variable (Y).In this study, vegetation land cover density is used as the independent variable (Independent) and surface temperature is used as the dependent variable (Dependent).Calculations were carried out from 2013 to 2021 where the data were merged into one.
IJDDI 2024, 4, 1, 10 http://ijddi.net The results obtained from the calculation of simple linear regression show an equation that means there is an influence between changes in the area of vegetation land cover density and changes in surface temperature from 2013 to 2021 because it shows positive results.
Where if the decreasing density of vegetation land cover will make the surface temperature rise in the area where it will have an impact on the emergence of the Urban Heat Island phenomenon.This is also explained in previous research which states that the UHI phenomenon that occurs mainly in urban areas is due to the large amount of built-up land and the lack of vegetation land (Wulandari, 2017).Linear calculation obtained a significant value between vegetation land cover density and surface temperature of 0.000 which means there will also be a significant influence on both variables of vegetation land cover density and surface temperature because the value obtained is less than 0.05.Another result in linear regression is also the r2 coefficient value where the value shows the results with a value of 0.377.The result of the coefficient of determination shows that the amount of influence obtained from the density of vegetation land cover with an average surface temperature of 37.7% where the rest can be influenced by other factors whether it is pollution and so on.In another study belonging to (Indrawati et al, 2020) also explained about the positive relationship where the regression result was 0.893, from these results it explained that the surface temperature data that had been obtained had a relationship with the data in the field.
The linear regression test that has been carried out shows that there is a positive influence between the reduced density of vegetation land cover and the average temperature in Klaten Regency.Reduced vegetation land itself is generally due to the construction of new buildings, or logging either legally or illegally.Of course, this can have an impact on the increase in surface temperature due to the reduced heat absorption of vegetation, especially if a new building is built.This is also explained by (Karyati et al, 2018) where the process of photosynthesis in plants and plants directly involves the use of water, energy and reflection of incoming rays so that it tends to reduce the temperature of the microclimate and indirectly it will also reduce the surface temperature on the ground.
Similar research in this study has also been conducted by (Irza Annesi et al, 2019)   The linear calculation performed obtained a significant value between the density of vegetation land cover and surface temperature of 0.000 which shows the simple linear regression calculation shows a positive result which explains if the lower the density of vegetation land cover will make the occurrence of vegetation land cover.increase in surface temperature which will increase the impact of the Urban Heat Island phenomenon in the region.

(
ToA) method by changing the Digital Number (DN) value.c.NDVI Transformation NDVI (Normalised Different Vegetation Index) is a method that can be used to calculate a vegetation density where the higher the NDVI value, the higher the vegetation density.d.Calculation of PV (Propotional Vegetation) Value PV (Propotional Vegetation) is one of the NDVI scaling processes to reduce interference arising from soil moisture.e. LSE Transformation LSE (Land Surface Emissivity) is a method to obtain surface emissivity data.(Valor & Casseles, 1996).f.LST Transformation LST (Land Surface Temperature) is defined as the temperature of the Earth's surface which is obtained from the reflection of objects recorded by satellite images.g.UHI Calculation UHI (Urban Heat Island) is used because LST has not obtained accurate results, therefore the UHI formula is used to get the final results using the formula below.h.Regression Testing IJDDI 2024, 4, 1, 6 http://ijddi.net

Figure 2
Figure 2 Spatio-Temporal Map of Surface Temperature of Klaten Regency 2013 -2021

Figure 4
Figure 4 Linear Regression Results IJDDI 2024, 4, 1, 11 http://ijddi.net where his research entitled The Effect of Vegetation Density on Surface Temperature in Padang City in 1999, 2009 and 2019.Where the results obtained in linear regression affect surface temperature with an R Square value of 0.95 with the level of influence reaching 95%.
dominated by vegetation cover density with very high and high classifications despite the decrease in area from 2013 to 2021.Where in 2013 the area was 303.3 km 2 until 2021 the area decreased to 213.5 km2 with Kemalang District being the highest dominance of areas that have a classification in this vegetation density with an area of 46.36 km2 in 2013 and also experienced a decrease in 2021 to 42.27 km 2 .Surface temperature in Klaten Regency is dominated by surface temperatures in the vulnerable 25 -28 o C spread across the entire region from 2013 to 2021.While in the highest temperature class classification 28 o C and above is dominated by areas in urban areas such as South Klaten District, North Klaten District, and Central Klaten District where this is due to the low level of vegetation density and more buildings around the area.