Abstract
This study identified summer and annual drought events using the Standard Precipitation Index (SPI) for 107 stations across Nepal from 1977 to 2018. For this, frequency, duration, and severity of drought events were investigated. The SPI4 and SPI12 time scales were interpolated to illustrate the spatial patterns of major drought episodes and their severity. A total of 13 and 24 percent of stations over the country showed a significant decreasing trend for SPI4 and SPI12. Droughts were recorded during El Niño and non-El Niño years in Nepal. Among them, 1992 was the worst drought year, followed by the drought year, 2015. More than 44 percent of the locations in the country were occupied under drought conditions during these extreme drought events. Droughts have been recorded more frequently in Nepal since 2005. The areas of Nepal affected by extreme, severe, and moderate drought in summer were 8, 9, and 18 percent, while during annual events they were 7, 11, and 17 percent, respectively. Generally, during the drought years, the SPI and Southern Oscillation Index (SOI) have a strong phase relation compared to the average years.
Highlights
Drought is a typical natural locally or regionally recurring characteristic of the climate
Meteorological drought is the consequence of a natural reduction in the amount of precipitation received over an extended period, usually a season or more in length [4]
The years of abnormally high sea surface temperature (SST) from the west coast of South America towards the equatorial mid-pacific are known as El Niño years, and the years of abnormally colder waters in the same region are known as La Nina years [8]
Summary
Drought is a typical natural locally or regionally recurring characteristic of the climate. It occurs in virtually all climatic regimes in areas with high and low rainfall. Drought is a temporary aberration, in contrast to aridity, a permanent feature of the climate, and is restricted to low rainfall areas [1]. The effects of drought often accumulate slowly over a considerable time period and may linger for years after the termination of the event [4]. Meteorological drought is the consequence of a natural reduction in the amount of precipitation received over an extended period, usually a season or more in length [4]. Most drought years are associated with El Niño episodes, followed by non-El Niño events in India [9–12]. The decrease in Indian monsoon rainfall was associated with the warm phase of ENSO due to anomalous regional Hadley circulation with decreasing motion over the Indian subcontinent [12]
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