Simulating moisture transport over the Tibetan Plateau in Summer across
hydrostatic to non-hydrostatic scales with a global variable-resolution
model
Abstract
Moisture transport in summer induces annual precipitation peak over the
Tibetan Plateau (TP) thus being one crucial sustentation of water cycle
between the TP and its surrounding areas. Simulating moisture transport
accurately over the TP remains uncertain for current numerical models
with one important influencing factor as horizontal resolution. In this
study, in order to investigate the difference in moisture transport at
resolutions from hydrostatic to non-hydrostatic scales, three
experiments are conducted for summer of 2015 using a global
variable-resolution model, including one with a globally quasi-uniform
resolution of 60 km (U60km) and two with regional refinements over the
TP at resolutions of 16 km (V16km) and 4 km (V4km), respectively. The
differences in moisture transport among three simulations are
significantly influenced by the changes in wind fields through the
Himalayas and eastern TP at two layers, 700~600 and
600~400 hPa, which is largely modulated by their
difference in large-scale circulations particularly monsoon depression.
At hydrostatic scale (from 60 km to 16 km), the monsoon depression is
slightly stronger and shifts northward along with the mid-latitude
westerlies, which is due to the combination of the sensitivity of
convection scheme to integrating timestep and different extents of
resolved dynamical processes at different resolutions. With horizontal
resolution increasing to convection-permitting scale (from 16 km to 4
km), the resolved moist convection along with its associated less latent
heat leads to weaker monsoon depression over the south of TP, which is
much larger than the resolution induced difference at hydrostatic scale.