Long‐term (2001–2020) trend analysis of temperature and rainfall and drought characteristics by in situ measurements at a tropical semi‐arid station from southern peninsular India

Abstract

AbstractWith the effects of climate change prevailing worldwide, it is essential to understand the long‐term rainfall and temperature trends at regional scales to plan for adaptation strategies. Investigating the temporal dynamics of meteorological variables in climate‐induced changes, particularly in rain‐fed agriculture countries such as India, is needful. The present study focused on the temporal variation of rainfall and temperature trends to analyse the drought characteristics over the past 20 years (2001–2020) using ground‐based Automatic Weather Station (AWS) data at a semi‐arid station Anantapur in southern peninsular India. The seasonal maximum mean temperature (Tmean) was observed in summer (32.20 ± 1.36°C), followed by the monsoon (29.08 ± 1.02°C), postmonsoon (26.45 ± 2.44°C), and winter (25.45 ± 1.01°C) during the study period. The Mann–Kendall trend test result showed the decreasing trend in seasonal mean temperature during the drying period (winter [−0.069°C·year−1] and summer [−0.081°C·year−1]) and increasing trend in the wetting period (monsoon [0.012°C·year−1] and postmonsoon [0.034°C·year−1]). On the other hand, the seasonal rainfall decreases in the postmonsoon (−2.276 mm·year−1) while increasing in winter (0.5 mm·year−1), summer (2.137 mm·year−1), and monsoon (6.901 mm·year−1) seasons. The annual trends of minimum, maximum, and mean monthly temperatures decrease at the rate of −0.121, −0.123, and −0.022°C·year−1, respectively, while the rainfall increases at the rate of 8.979 mm·year−1. Furthermore, the temporal evolution of meteorological drought characteristics was estimated with the help of the standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI) on multiple timescales ranging from 1 to 24 months on a monthly basis during the study period. The 24‐month SPI values showed that 1 “severely dry” and the 29 “moderately dry” long‐term drought events were observed. From 24‐month SPEI, a total of 15 “severely dry” and 20 “moderately dry” long‐term droughts were observed during the study period. The severely dry years were observed in 2002 and 2003, while the wettest periods were 2007 and 2010. Both indices are identified as more severe dry periods from 2002 to 2006 and 2013 to 2017 than rest periods. Also, a significant decreasing tendency of droughts was observed in both indices. The SPI values are compared with El Niño–Southern Oscillation (ENSO) and normalized difference vegetation index (NDVI) and found that the SPI versus ENSO index negatively correlates with the coefficient of −0.58 significantly, while the SPI versus NDVI correlation is insignificant. The study region converted to wetter conditions during the last 20 years.