This analytical story is about Drought, its frequency and intensity across India. This story emerged while working on Drought Vulnerability Management System. This story is due to effort put in processing 15 years of data (2001 to 2015).
For analysing drought we have used Integrated Drought Severity Index (IDSI) developed by IWMI (International Water Management Institute). Index uses 3 sub-indices Vegetation Condition Index(VCI), Precipitation Condition Index(PCI) and Temperature Condition Index(TCI). To develop VCI and TCI we have used MODIS’s NDVI and LST products. For PCI we have used TRMM data.
NDVI used is 16 day temporal data, LST is 8 day temporal data and TRMM data is 1 month aggregated rainfall data. For long term averages, minimums and maximum, we have used 15 years of data. Raw data of MODIS product (HDF format) will reach upto 300 GBs (of which NDVI data is 242 GBs). We have processed this entire dataset to get pixel wise minimum and maximum. We used horizontal averaging concept for this. Then, these min and max were used to generate VCI,TCI and PCI, which were again used to create IDSI. IDSI varies between 0 to 100. IDSI with values near to zero means Extreme Drought condition and IDSI with values near to 100 means a Healthy. Based upon IDSI values, entire India was categorized into 7 classes Healthy, Normal, Watch, Stress, Moderate Drought, Severe Drought and Extreme Drought.
In current study we have taken 6 months( February to July) of every year for studying drought. Monthly IDSI for entire India was generated for all 6 months of 15 years. This data was then aggregated using Hexagon bins of 259 sq km. Using this aggregated data, number of drought and non-drought months was calculated for each hexagon. Likewise drought intensity using type of drought was also calculated. Hexagon bin aggregation was data for data rendering and visualization purpose. We also have 1 Km grid IDSI raster for each months of study period.