The present study aims to assess agricultural drought using remote sensing based NDVI and soil moisture products in a drought prone river basin of India. The study is conducted in the Ghataprabha river basin which is a sub basin of river Krishna, in India and is agriculturally dominated. Major portion of the basin is semiarid and rainfall is the major sources of water for agriculture. Gridded soil moisture data from Modern-Era Retrospective analysis for Research and Applications (MERRA) from 1980 to 2015 is considered to derive Standardized Soil moisture Index (SSI) at different time scales. The Vegetation Condition Index (VCI) was calculated from MODIS NDVI products from 2000-2013. The results of VCI and SSI indicated significant number of drought episodes during the study period while severe agricultural drought was observed during 2001-2003. A Good agreement between SSI and VCI was observed during drought year.
Drought is commonly occurring natural hazard. It has vicious impact on agricultural production as well as on socioeconomic status of an area. Meteorological drought will induce with the deficit of rainfall and leads to agricultural drought as it prolongs. Rainfall is crucial parameter to assess meteorological drought and NDVI based indices can capture agricultural drought satisfactorily. The present study aims to assess meteorological and agricultural drought in the Ghataprabha river basin using Standardized Precipitation Index (SPI) and Vegetation Condition Index (VCI). Monitoring of SPI and VCI will benefits to mitigate drought impacts with the proper water resources managements. Ghataprabha river basin is the sub basin of river Krishna, in India and is agriculturally dominated. Major portion of the basin is semiarid and rainfall is the major sources of water for agriculture. Average annual rainfall of the basin varies from 600 mm to 2000 mm. Gridded rainfall data was procured from the Indian Meteorological Department for the period of forty three years (1970- 2013) and considered same as input for SPI. To calculate SPI with multiple time scale, two parameter gamma distribution was implemented. MODIS NDVI products from 2000-2013 was considered for calculation of VCI. Significant number of meteorological drought episodes were observed during the study period while severe agricultural drought was observed during 2001-2003 and in 2012. SPI and VCI were compared to quantify variation of VCI with respect to SPI. Good agreement between SPI and VCI was observed during drought and non-drought periods. Results indicates that eastern part of the basin was more prone to severe droughts as compare to other part of the basin. This study assistances to formulate drought mitigation strategies and to establish effective water resources policies in the study region.
Rapid increase of population and urban sprawl have an immense impact on local climatic conditions. Urban heat island, increased surface roughness and enhanced aerosol are some of the prominent factors affecting precipitation in such highly populated urban areas. Among these, the complex interaction of aerosol particles with solar radiation have acknowledged their importance in radiation budget and hence climate dynamics. Being cloud condensation nuclei they also influence cloud lifetime and microphysics in turn influencing precipitation. Present investigation emphases on understanding rainfall and aerosol trends and its spatial occurrence pattern with respect to urbanization. An approach where population as an indicator for urbanization is used in this study rather than a profound investigation on the individual factors of urban induced precipitation anomalies. Mann Kendall trend test is carried out at grid level on a 0.25 degree gridded rainfall data and the trends are then related with the distribution of population in the study area. Areas of significant rainfall trends are identified and are analyzed for spatial patterns around urban areas. These identified urban zones are then further analyzed for aerosol variability. Being a monsoon region, a seasonal variation of aerosols are performed. The results shows that during the monsoon season there is a significant increase in rainfall along the Western Ghats, whereas certain grids along the western coast located at the downwind of populated areas such a Mangalore shows a significant decreasing trend. The overall spatial pattern of rainfall trend during pre-monsoon season is indicative of the influence of urban areas on rainfall. This observation during the pre-monsoon season is quantified which shows that 61% of the trends are included within urban influence zones which are only 36% of the size of Karnataka. Further various cloud characteristics and its association with aerosol loading in these urban areas were investigated. The results are indicative of higher aerosol events suppressing rainfall in these urban areas.
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