Impact of the Eurasian wave train on Autumn Precipitation in the Central
Region of China
Abstract
The autumn precipitation in the central region of China (APCC) can exert
great influences to the production and people’s livelihood. With the use
of reanalysis data from 1979−2020, we found a simultaneous relationship
between the interannual variability of APCC and the second mode of the
200-hPa meridional wind field over the Eurasian continent, which
featured a ‘+-+’ wave-like pattern in autumn (denoted by EC-a). When
EC-a is in a positive phase, the coupling of the positive geopotential
height with anticyclonic anomalies in the upper level and low sea level
pressure over the central China provides a conducive moisture and
dynamic condition for precipitation, which is reversed in the negative
phase. As indicated by the diagnostic equation, the local vertical
motion anomaly is mainly dependent on the temperature advection anomaly
by the perturbed wind acting on mean temperature. The strengthened
anticyclonic wind shear over East Asia reinforces the southeasterly,
which induces warmer air to move northward, resulting in a positive
temperature advection and hence enhancing local ascending motion.
Moreover, wave flux analysis and numerical simulations show that the
EC-a wave train could be triggered by an abnormal dipole pattern SST
over the North Atlantic Ocean, which acts as a critical pacemaker on the
variability of EC-a.