Assessment of compound dry and hot extremes over India using a
copula-based multivariate standardized index.
Abstract
Compound dry and hot extremes (CDHE) during the Indian summer monsoon
significantly affect agriculture. Due to climate change, the frequency,
spatial extent and severity of CDHE have changed over several parts of
the world. Understanding the variability of CDHE is critical for
designing adaptation strategies to reduce the adverse impacts on
agricultural systems. In particular, traditional assessments have
focused on the variability of frequency and spatial extent using the
quantile-based approach. However, counting the number of events excess
over the threshold helps to understand the variability in frequency and
spatial extent but fails to detect the changes in the severity. Further,
limited studies have investigated the changes in CDHE severity over
India. Hence, in the present study, the variability of CDHE severity is
assessed during the summer monsoon from 1951 to 2020 over homogenous
regions of India using a copula-based Standardized Compound Event
Indicator. A significant increase in the severity of CDHE during the
summer season was found in eight homogenous regions out of ten. The most
vulnerable regions are northeast India and peninsular India, and
interestingly, a significant decrease in the severity is observed for
the north rain-belt Western Himalayan region. In addition, a significant
increase in the spatial extent of the CDHE severe category is also found
in all the homogenous regions over the past three decades. This study
highlights that severe CDHE is associated with a high risk of severe
agricultural drought for a large part of the country. Uni-variate
assessments based on precipitation or temperature can underestimate the
risks associated with CDHE if there is a strong dependence among the
drivers.