Deciphering the Shift from Warm-Dry to Warm-Wet Events in Ice-Covered
and Non-Ice-Covered Regions
Abstract
Compound warm events exert profound impacts on environment, health, and
socioeconomics. A recent study indicated a shift or transition from
warm-dry events (WDEs), common in non-ice-covered areas, to warm-wet
events (WWEs) in ice-covered zones. Utilizing ERA5 reanalysis data, this
study determined the duration and frequency of WDEs and WWEs across
ice-covered and non-ice-covered regions. A comprehensive analysis
uncovers the physical mechanisms responsible for this shift and
attributes it to the weakening of land-atmosphere interaction caused by
ice-cover, which inhibits soil moisture feedback and reduces the
intensity and duration of warm events in ice-covered areas. Both WDEs
and WWEs are associated with high-pressure systems (HPs). WDEs, situated
directly beneath HPs, intensify due to adiabatic warming from subsidence
motions. Conversely, WWEs, located beneath the poleward fringes of HPs,
emerge from advective warming and moistening associated with poleward
intrusions of warm-moist air.