South drying and north wetting over the Tibetan Plateau modulated by a zonal temperature dipole across timescales

Precipitation over the Tibetan Plateau and surrounding highlands is a crucial process in the hydrological cycle and is very important for local and downstream ecology,and previous research mainly focused on a certain range of timescales.A better understanding of the variability across various timescales,which has been largely ignored,can provide new insight on the regional weather and climate.Here,a north‒south dipole pattern of precipitation shaped by a zonal dipole of the upper-tropospheric temperature is revealed in this region.Both dipole patterns of the precipitation and the accompanied temperature exist from daily to interdecadal scales.The three-dimensional circulation anomalies connecting the temperature and precipitation dipoles are consistent across various timescales.The frequencies of daily events with opposite phases of the temperature dipole modulate the interannual and interdecadal variability in precipitation.The south drying and north wetting pattern over the Tibetan Plateau is an interdecadal manifestation of the precipitation dipole and can be ascribed to the temperature trend favourable for the positive phase of the zonal temperature dipole.The consistent dipole pattern constructs a more complete portrayal of precipitation over the Tibetan Plateau from synoptic scale to climatology.

Evaluation of CMIP6 HighResMIP models in simulating precipitation over Central Asia

The High Resolutio n Model Intercomparison Project(HighResMIP)experiment within the Coupled Model In tercomparison Project Phase 6(CMIP6),for the first time,has provided an opportunity to evaluate the performance of climate models over complex topographies.Based on the HighResMIP's historical simulations of atmospheric general circulation models,the performances of global high-resolution models,with a horizontal resolution finer than 50 km,in representing precipitation over Central Asia were evaluated using rain gauge observation datasets.All the models successfully reproduce the large precipitation regions that are located over the mountainous areas and Northern Central Asia.However,nearly all the models overestimate precipitation frequency over Central Asia and large overestimations of precipitation amount and frequency are located over the mountainous areas.Although the HighResMIP multi-model ensemble mean performs better than all individual models at simulating the spatial pattern of precipitation frequency,it is inferior to HadGEM3-GC31-HM and ECMWF-IFS-HR at simulating that of precipitation amount.The simulation performance exhibits remarkable regional differences.Over the Qilian Mountains,the relationship between precipitation and elevation is totally captured by climate models.In contrast,over the Tianshan Mountains,the models fail to simulate the decrease in precipitation frequency after elevation higher than the maximum precipitation elevation.Most models successfully reproduce the annual cycle shape of precipitation amount over the Southern Central Asia,Qilian Mountains and Tianshan Mountains,but fail to reproduce it over the Northern Central Asia.More than half of the high-resolution GCMs have a reduced bias relative to the corresponding low-resolution GCMs.The performances of most high-resolution GCMs in simulating precipitation pattern are well over the Tianshan Mountains.