29. Evaluation of Multiple Satellite Precipitation Gridded Products for Standard Precipitation Index Based Drought Assessment at Different Time Scales

Standard Precipitation Index (SPI) computed at multiple time scales is considered as a key indicator for short-term agricultural to long-term hydrological drought monitoring. SPI computed at multiple timescales namely 1, 3–6 and 12 months represent meteorological, agricultural and hydrological droughts, respectively. Traditionally, precipitation based SPI drought index is being computed using raingauge station data, which is often limited by sparse and uneven distribution of raingauge stations. However, uncertainty in aerial estimation of rainfall and data scarcity regions can be overcome by envisaging various quasi-global satellite derived precipitation products such as TRMM multi-satellite Precipitation Analysis (TMPA), Climate Hazards Group Infrared Precipitation with Stations data (CHIRPS), Climate Research Unit (CRU) data for drought monitoring. Hence in this study, characterization of spatially varying drought occurrences and its severity at different time scales was carried out using various precipitation gridded products (TRMM, CRU and CHIRPS) for part of Indo-Gangetic Plain, India. Further, drought severities assessed by these gridded products were relatively evaluated with reference to rain gauge based IMD gridded product. The spatial pattern of TRMM and IMD based SPI for all the time scales were observed to be similar for both wet and dry years. The spatial pattern of low and high number of drought events is mostly similar for CHIRPS, TRMM and IMD. Overall, it was observed that spatial pattern of drought frequency identified through CRU based SPI was completely distinct compared to other datasets. In general, CHIRPS appears to have overestimated the drought area and frequency compared to IMD, while TRMM data exhibited a similar pattern as that of IMD product which could be due to the fact that CHIRPS underestimates the rainfall.