2.1 Study area
Uttar Pradesh, a state in the north-central part of India extends from 23°52′N to 31°28′N latitudes and 77°3'E to 84°39'E longitudes. It is situated east of Delhi which is the capital city of the country and shares a border with Haryana, Rajasthan, Uttarakhand, Madhya Pradesh, Himachal Pradesh, Jharkhand, Bihar, and Chhattisgarh. As per census 2011, it had 71 districts but at present, there are 75 districts in 2024 at the time when this study was being conducted. The state of Uttar Pradesh has a generally humid and subtropical climate with a mostly dry winter. The state ranked as first in terms of population in the country as per data of census 2011. Although UP lags behind the national average of urbanization which is 31.6% but still its urban population increased from about 20.78% in 2001 to about 22.28% in 2011 which shows a rise of about 1.5%. this shows that urbanization is increasing and if the recent census had happened much more rise in urbanization would have occurred. Figure 1 depicts the description of the study area of Uttar Pradesh.
2.2 Heatwave Vulnerability Index (HVI)
In this present study, the estimation of the heatwave vulnerability index was done by calculating the exposure, sensitivity, and adaptive capacity of the locals living in the area. As per the calculation done in this study exposure and sensitivity add to the HVI positively and adaptive capacity negatively (Raja et al., 2021).
Heatwave vulnerability index (HVI) = E + S-A…………………………………………..(1)
Here exposure is represented by E, sensitivity by S, and adaptive capacity by A. Many literatures were reviewed to decide the variables which are present in this study. The variables were also decided based on their easy availability. They are expressed such that minimal spatial bias occurs.
Exposure
This study was conducted using land surface temperature (LST) and population density as variables of the respective districts. Many studies in recent times show that LST can be used for measuring heat exposure intensity (Raja et al. 2021). Its influence as a variable on the heatwave vulnerability index is highest among all other variables. If occurs in excess it can induce many cardiovascular and respiratory-related diseases. There are many pieces of evidence available that indicate that a rise in land surface temperature could be linked to increased vulnerability due to heatwaves (McGeehin and Mirabelli 2001). Similarly, there are other studies which show that areas with very dense populations are much more susceptible to heat (Tomlinson et al. 2011).
Sensitivity
On the basis of various other studies which were performed similarly, ten variables are selected which are mentioned in Table 1. People aged > 60 years are categorized as older people and most of these people have underlying medical conditions due to their old age and have cardiovascular problems (Aldrich and Benson for CDC 2008). Children with age less than 6 years are also at risk of getting affected by heat waves due to their vulnerability to various diseases that are vector-born (Wilhelmi and Hayden 2010). There are many studies that suggest that illiteracy also makes people somewhat sensitive towards heatwave events as they do not know about the risks (Uejio et al. 2011). Studies also suggest that socioeconomic factors may also be associated with such extreme events. For instance, the people who are affected by poverty cannot afford various utility facilities (e.g. fans, coolers, AC) and it also makes them vulnerable and sensitive to heatwaves (McMichael et al. 2008). The poverty was explained using the multidimensional poverty index (MPI) which was developed by the Department of Planning, the government of Uttar Pradesh. The MPI was developed by focusing on various qualitative aspects across three dimensions which are health, education, and living standards. This MPI was inspired by the global MPI published by Oxford Poverty and Human Development Initiative. There are studies that suggest that the female population is more sensitive to heat waves in comparison to men (Johnson et al. 2012). The nature of work also affects the sensitivity towards heat waves. For example, people in occupations like agriculture and industrial work have more susceptibility towards extreme events such as heat waves (Cutter et al., 2003). Scheduled Tribe (ST) and scheduled caste (SC) populations are also underdeveloped and lag behind the other social groups on various parameters such as education (Khatoon 2018). The houseless population is always exposed to various extreme events such as heatwaves.
Table 1
Description of data used in the study.
Variables | Description | Unit | Data source |
Latent | Observed |
Exposure | LST | Pixel wise LST | °C | United States Geological Survey (USGS), Landsat 8, May 2023 |
Population density | Number of people living in per km2 | Person/km2 | Census 2011 |
Sensitivity | Very old population | Elder people (> 60 years) in the percentage of the total population | % | Census 2011 |
| Children (0–6 years) in percentage of total population | % | Census 2011 |
Illiteracy rate | Illiterate people in Percentage of the total population | % | Census 2011 |
MPI | Multidimensionally poor people in Percentage of the total population | % | Department of Planning, the Government of Uttar Pradesh, 2023 |
Sex ratio | Female population per 1000 male population | Ratio | Census 2011 |
Workers | People working outside their homes in percentage of the total population | % | Census 2011 |
SC | SC population in the percentage of the total population | % | Census 2011 |
ST | ST population in the percentage of the total population | % | Census 2011 |
Houseless households | Houseless households in the percentage of the total population | % | Census 2011 |
Adaptive capacity | Access to electricity | People with access to electricity in the percentage of the total population | % | Census 2011 |
NDVI | Health of vegetation in the area | Ratio | USGS, Landsat 8, May 2023 |
Number of primary Healthcare centers (PHC) | Number of PHC/ (Lakhs of population) | Ratio | National Family Health Survey, 2019-21 |
Road density | Roads in kilometres per 1000 km2 | Road length/1000 km2 | Basic road statistics, ministry of road transport and highways, 2018-19 |
NDWI | Spatial water distribution over the area | Ratio | USGS, Landsat 8, May 2023 |
Adaptive capacity
There are five variables that were decided on the basis of the study of various kinds of literature for measuring adaptive capacity: Normalised Difference vegetation index (NDVI), access to electricity, road density, normalized difference water index (NDWI), and a number of primary healthcare centers (PHC). NDVI tells about the distribution of vegetation in the area. A good proportion of vegetation in the area can reduce its overall temperature (Kinney et al. 2008). The road density of the area is associated with congestion due to traffic. A good road infrastructure with adequate density in the area would decrease the generation of heat by decreasing the congestion due to traffic (Inostroza et al. 2016). NDWI tells about the distribution of the water in the area. It was found in various studies that water bodies can reduce the intensity of heat as it has an inverse correlation with temperature (Mushore et al. 2018). There are various studies that suggest that at times of extreme weather events load on health facilities gets heavy which in turn increases the need for hospitals and other facilities (Mason et al. 2022; Lee et al. 2024). This study incorporates the number of Primary Healthcare Centres (PHC) as an adaptive measure in this study.
Satellite data processing
Various satellite data processing works were performed using various Landsat 8 images of thirty-metre resolution. LST was calculated using band 10 which are Thermal InfraRed Sensor, spectral band. This approach was used by (He et al. 2019) in their study. NDVI was already used for the calculation of vegetation cover in many studies by using band 5 and band 4 Landsat 8 images (Anyamba and Tucker 2005). Similarly, the NDWI was already used for highlighting water bodies using Band 3 and Band 5. However, these two indices have never been used together for representing adaptive capacity in any of the HVI calculations. The average of the values of LST, NDVI, and NDWI was taken for calculations.
Factor analysis
There could be multicollinearity among the indicators taken for the assessment of HVI. That’s why correlation coefficients were used to check the relationship between these indicators (Schober and Schwarte 2018). There was not that much collinearity among the indicators. But still factor analysis was brought into use for the reduction of dimensions and thereby its complexity (Harlan et al. 2013). Kaiser-Meyer-Olkin (KMO) test and also Bartlett’s sphericity tests were performed to check the adequacy of the sample and the resulting usefulness respectively. The values obtained for the KMO test for each of E, S, and A were 0.50, 0.76, and 0.66 respectively. Performing varimax rotation and using Kaiser-eigenvalue rule extraction of independent components was done. The regression method was used for factor score estimation. Then the obtained scores were used in the previously mentioned formula for HVI calculation. The values that we obtained were then classified into five classes- very low (VL), low (L), medium (M), high (H), and very high (VH).
Distribution of HVI spatially
The results obtained as HVI scores for each district are then taken and used for preparing a spatial distribution map for UP. ArcGIS was used for this operation. The five classes obtained are shown in different colors and can be identified very easily.