Drought is a function of time as well as climate variables such as temperature and precipitation. The process of drought forming is slow, and it manifests at different time scales, which adversely affects the economy of a country. The identification and characterization of droughts at various spatiotemporal scales are of great importance. It helps in the planning and management of water resources, policymaking, and agribusiness industries. In the present paper, the Cauvery River basin is chosen as a study area to analyze the changes in the frequency distribution of extreme droughts and duration, with the combined effect of evapotranspiration and rainfall. The drought indices such as Standard Precipitation Index (SPI) and Standard Precipitation Evapotranspiration Index (SPEI) are implemented on monthly rainfall data and potential evapotranspiration of resolution 0.25° × 0.25° long./lat. for the period 1931–2010. The results reveal that the frequency of the extreme droughts over the basin has significantly increased over the post-era of global warming. The increased rate of extreme droughts is particularly evident in downstream of the basin, mainly due to the increase in temperature and deficit rainfall. Further, the implementation of continuous wavelet transform reveals that SPI at 3-(SPI-3) and 12-(SPI-12) month scale are associated with extended reconstruction of sea surface temperature (ERSST) in anti-phase and in-phase, respectively. It is concluded that the in-phase association of SPI-12 and ERSST enhances the drought situation compared to the anti-phase link of SPI-3 and ERSST.

干旱是时间以及温度和降水等气候变量的函数。干旱形成过程缓慢，并且表现在不同的时间尺度上，对一个国家的经济产生不利影响。各种时空尺度的干旱的鉴定和表征非常重要。它有助于水资源，政策制定和农业综合企业的规划和管理。本文以Cauvery河流域为研究区域，结合蒸散量和降雨的影响，分析极端干旱和持续时间的频率分布变化。干旱指数，例如标准降水指数（SPI）和标准降水蒸散指数（SPEI），是根据月降雨数据和分辨率为0.25°×0.25°/ lat的潜在蒸散量计算的。1931年至2010年期间。结果表明，在全球变暖后时期，流域内极端干旱的发生频率显着增加。在流域下游，极端干旱的增加尤其明显，这主要是由于温度升高和降雨不足所致。此外，连续小波变换的实施揭示了3-（SPI-3）和12-（SPI-12）月尺度的SPI与反相和同相海面温度（ERSST）的扩展重建有关，分别。