Extreme dry advection dominates the record-breaking Yangtze River
heatwave in midsummer of 2022
Abstract
The Yangtze River Valley (YRV) experienced an unprecedented heatwave in
midsummer of 2022, but the detailed physical processes involved in the
influence of anomalous large-scale atmospheric circulation on the
heatwave remain unknown. Here, we show that the positive meridional
gradient of anomalous atmospheric moisture at the middle-lower
troposphere and associated extreme dry air advection over the YRV are
key prerequisites for the formation of the 2022 YRV heatwave. The 2022
YRV heatwave is dominated by the interannual variability, which
contributes 72.7% to the total temperature anomalies. Diagnosis of the
surface heat budget equation indicates that the surface cloud radiative
forcing is the most important process in driving the 2022 YRV heatwave,
which is dominated by the positive surface short-wave cloud radiative
forcing associated with the suppressed precipitation and the middle-low
clouds. The suppressed precipitation is induced by the vertical
dynamical processes of anomalous moisture advection caused by the
anomalous descending flows over the YRV, which are driven by the
negative advection of anomalous latent heat energy by climatological
meridional wind (anomalous dry air advection) according to the
atmospheric moist static energy equation. Simulations from the
Lagrangian model FLEXPART further indicate that the moisture anomaly
over the north of YRV is mainly originated from the surface evaporation
in the YRV, implying that there is a positive land-air feedback during
the life cycle of the YRV heatwave. Our study adds a perspective to the
existing mechanism analyses of the 2022 YRV heatwave to serve accurate
climate prediction and adaptation planning.