Climatic Trends in Temperature, Relative Humidity, and Wind Speed Over Indian Landmass and Isle in Andaman Nicobar and Lakshadweep During 1981–2021

Abstract

An analysis is performed to examine trends in temperature, relative humidity, and wind-speed over the Indian landmass and in the isles of Lakshadweep (Arabian Sea side) and Andaman and Nicobar (Bay of Bengal side) over the last four decades (from 1981 to 2021). MERRA data deployed for revealing the large-scale fluctuations and linear trends in these parameters covering 36 locations. Surface temperature (2 m above ground) data showed a linear rise, which is more prominent after 2000, both in the Arabian side and the Bay of Bengal. Over this period, temperature increased ~ 0.7–0.8 °C on both sides of Indian landmass. About two third locations (24 locations) in the study showed increase in temperature. However, relative humidity data on all island locations exhibited a decrease (prominent during 2000–2021). Quasi-periodic fluctuations in temperature (which is linearly rising) closely relates with the ENSO parameter (correlation coefficient ‘r’ in Arabian Sea and Andaman and Nicobar ranged from ~ 0.20 to 0.34; which is statistically significant and relatively larger towards Andaman Islands). ‘r’ increased considerably (> 0.5) during 2000–2021. Wind-speed, in general, showed larger magnitude over Andaman and Nicobar Islands (~ 5.0 m/s yearly averaged) in comparison to Arabian Sea (~ 4.0 m/s) and landmass (~ 2.2 m/s). On the other hand, solar cycle (sun spot numbers) and wind-speed reflects a weak positive correlation coefficient (< ~ 0.40) but statistically significant while no consequential correlation found between solar cycle and relative humidity. Detailed analysis suggests that relative humidity decreased both over landmass and islands during 2000–2021. Interestingly, surface temperature increased more rapidly between latitudes 7.03°N and 12.91°N after 2000. Rise in temperature and long period fluctuations (> 2–3 years) in the lower latitudes (< 15°N) showed a strong association with ENSO signal suggesting invigorated atmosphere ocean interaction.