Abstract

The surface temperature of the globe during the last few decades has been rising sharply due to global warming, which in turn increases humidity in the atmosphere. The increased temperature and humidity in the atmosphere leads to increasing propensity of occurrence of heat-waves (HWs) in the vari... Show moreThe surface temperature of the globe during the last few decades has been rising sharply due to global warming, which in turn increases humidity in the atmosphere. The increased temperature and humidity in the atmosphere leads to increasing propensity of occurrence of heat-waves (HWs) in the various parts of the globe, particularly in the tropical belt. HW, one of the dangerous extreme weather events that evident mostly during summer (March-June; MAMJ) over India, is the state of the atmosphere owing to prolonged high and above normal temperature and becomes dreadful when prodigious humidity has prevailed and is significantly affecting on various sectors such as health, agriculture, fishers, poultry firm, hydropower, hydrology, etc. The drought in the All India summer monsoon rainfall (June to September; AISMR), which monsoon contributes near about 80% of annual rainfall over India following with more number of HWs is significant in the distress it causes. Thus, there is a necessity to examine the characteristics of surface air maximum temperature (Tmax) and associated HWs over India during MAMJ. In the present study, several standard and derived parameters associated Tmax, short-(2 day) and long-duration (≥5-day) heat wave spells from 1st March to 30th June over India using India Meteorological Department (IMD) gridded analysis dataset from 1951 to 2019 have been analyzed. The most recent changes (2000-2019) in the Tmax and the frequency of total number of HW days, short and long-duration HW spells with the earlier period (1951-1999) have been evaluated. The role of antecedent AISMR on the occurrence of HW days, short and long-duration HW spells and its spatial coverage over India has been examined. The results suggest that the higher Tmax values (>36⁰C) and associated HW days, short and long-duration HW spells and its spatial coverage is prominent in most parts of the country during May followed by June, April and March. In the recent period, a notable increase in the Tmax and associated HW days, short and long-duration HW spells and its spatial coverage during all the months and MAMJ when compared with the earlier period and is mainly due to the increase of number of drought AISMR years associated with El Nino events in the recent period. The correlation analysis reveals that the antecedent AISMR having an inverse relationship with the frequency of HW days, short and long-duration HW spells in most parts of the country during all the months and MAMJ and these inverse relationships are highly significant in most parts of the country where these HW events are more prominent. It is interesting to notice that the frequency of HW days, short and long-duration HW spells and its spatial coverage is noticeably high during the AISMR drought+1 years when compared with AISMR excess+1 years. It has also been found that the probability of occurrence of above normal frequency of HW days, short and long-duration HW spells in most parts of the country is remarkably high (>60%) during the AISMR drought+1 years where the all types of HWs are more prominent. Therefore, the AISMR is giving good signal and helping in the estimation of the probability of occurrence above normal frequency of HW days, short and long-duration HW spells and this information is very useful in determining the effects on various sectors and planning of adaptation techniques and prevent measures through appropriate strategies for a sustainable future over India in the present global warming era. Show less