Impact of model resolution on simulating the water vapor transport through the central Himalayas: implication for models’ wet bias over the Tibetan Plateau

• Published in: Climate dynamics Vol. 51; no. 9-10; pp. 3195 - 3207
• Main Authors: Lin, Changgui, Chen, Deliang, Yang, Kun, Ou, Tinghai
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.11.2018; Springer; Springer Nature B.V
• Subjects: Analysis; Bias; China; climate; Climate models; Climate Science; Climatology; Computer applications; Computer simulation; Earth and Environmental Science; Earth Sciences; Environmental aspects; Geophysics/Geodesy; Himalayan region; Himalayas; Klimatvetenskap; landscapes; Meteorologi och atmosfärsvetenskap; Meteorology and Atmospheric Sciences; monsoon season; Oceanography; Plateaus; Precipitation; Precipitation (Meteorology); Resolution; Resolution dependency; Slope; summer; Summer monsoon; Terrain; Tibetan Plateau; Transport; Water balance; Water vapor; Water vapor transport; Water vapour; Weather forecasting; Wet bias; Wind speed; Tibet; Himalaya Mountains; Tibetan Plateau; Himalayan region; China; Tibetan Plateau; Resolution dependency; Wet bias; Himalayas; Water vapor transport
• ISSN: 0930-7575; 1432-0894; 1432-0894
• DOI: 10.1007/s00382-018-4074-x

Current climate models commonly overestimate precipitation over the Tibetan Plateau (TP), which limits our understanding of past and future water balance in the region. Identifying sources of such models’ wet bias is therefore crucial. The Himalayas is considered a major pathway of water vapor transport (WVT) towards the TP. Their steep terrain, together with associated small-scale processes, cannot be resolved by coarse-resolution models, which may result in excessive WVT towards the TP. This paper, therefore, investigated the resolution dependency of simulated WVT through the central Himalayas and its further impact on precipitation bias over the TP. According to a summer monsoon season of simulations conducted using the weather research forecasting (WRF) model with resolutions of 30, 10, and 2 km, the study found that finer resolutions (especially 2 km) diminish the positive precipitation bias over the TP. The higher-resolution simulations produce more precipitation over the southern Himalayan slopes and weaker WVT towards the TP, explaining the reduced wet bias. The decreased WVT is reflected mostly in the weakened wind speed, which is due to the fact that the high resolution can improve resolving orographic drag over a complex terrain and other processes associated with heterogeneous surface forcing. A significant difference was particularly found when the model resolution is changed from 30 to 10 km, suggesting that a resolution of approximately 10 km represents a good compromise between a more spatially detailed simulation of WVT and computational cost for a domain covering the whole TP.