Understanding Compound Dry-Hot Events in New Delhi: HistoricalTrends and Projections under +2°C and +4°C Warming Scenarios

Compound Dry and Hot Events (CDHEs) are increasingly recognized as critical
challenges of the 21st century, marked by the simultaneous occurrence of prolonged
dry periods and high temperatures. These events, more severe than individual
extremes, adversely impact water resources, agriculture, public health, and
infrastructure. Globally, CDHEs are becoming more frequent, longer, and intense,
particularly in climate-sensitive regions, including India. Urban areas like New Delhi,
with its high population density, limited water resources, and susceptibility to extreme
weather, are particularly vulnerable. This study examines CDHEs in New Delhi over 66
years (1958–2023) using monthly precipitation and temperature data from the
TerraClimate database. Standardized indices like the Standardized Compound Event
Indicator (SCEI), Standardized Precipitation Index (SPI), and Standardized
Temperature Index (STI), along with the joint probability density function (JPDF), are
applied to assess trends in frequency and severity. The analysis reveals a marked
increase in CDHEs post-1990, linked to regional climate changes, accelerated
urbanization, and evolving land-use patterns. Future projections under +2°C and +4°C
global warming scenarios indicate a substantial rise in both the frequency and severity
of CDHEs, posing critical threats to urban systems, including water scarcity, heat stress,
and economic losses. The results also suggest potential interactions between extreme
temperatures and declining rainfall, which could amplify the vulnerability of socio-
economic sectors. This research underscores the urgent need for integrated climate
adaptation and mitigation strategies tailored to urban environments. By linking historical
patterns of CDHEs with future projections, the study provides a comprehensive
perspective on hydroclimatic extremes in New Delhi. These findings are crucial for
informing urban planning, resource management, and policymaking aimed at enhancing
resilience against the cascading impacts of compound extremes in a rapidly warming
world.