High-resolution CMIP6 fashions proven to higher seize long-term precipitation tendencies in excessive mountain Asia

High Mountain Asia (HMA), the supply area of main Asian rivers, performs an important function in sustaining downstream water and ecosystem safety. Over the previous 50 years, summer season precipitation in HMA has exhibited a dipole sample—drying within the south and moistening within the north.

While world local weather fashions are broadly used to discover the mechanisms and projections of those modifications, their efficiency stays restricted by the area’s advanced terrain and distinctive local weather circumstances. A key query thus arises: Can enhanced mannequin decision yield better constancy in simulating HMA precipitation?

A brand new examine published on October 15 in Journal of Climate addresses this difficulty, revealing the added worth and bodily mechanisms of elevated horizontal decision in simulating HMA long-term precipitation tendencies. The work was led by Ph.D. pupil Lan Li from the Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences, and the University of Chinese Academy of Sciences (UCAS).

Using six pairs of CMIP6 fashions with totally different horizontal resolutions, the group analyzed how larger decision improves the simulation of long-term summer season precipitation tendencies (1951–2014) and explored the bodily mechanisms driving this enchancment.

“The high-resolution models capture observed precipitation trends much more accurately than their low-resolution counterparts—especially over the southern margin of the HMA and nearby regions—reducing the wet bias by roughly 65%,” stated Lan Li, the examine’s lead creator.

What drives this enchancment? “The enhanced performance of high-resolution models primarily stems from remote forcing associated with Indian Ocean SST warming, rather than local orographic effects,” defined Professor Tianjun Zhou, the examine’s corresponding creator.

In-depth analyses of moisture finances and moist static vitality finances reveal that the high-resolution fashions can higher seize a heat sea floor temperature (SST) sample over the central tropical Indian Ocean. This SST anomaly suppresses precipitation over the South China Sea and the Maritime Continent, which in flip triggers a Rossby wave response that generates an anomalous anticyclonic circulation over the northern Bay of Bengal. The ensuing anticyclonic circulation transports dry air into the southern HMA, suppressing native convection and assuaging extreme precipitation within the area.

This examine demonstrates that, beneath the identical bodily configuration, local weather fashions with larger horizontal decision extra precisely reproduce precipitation tendencies over High Mountain Asia. The researchers due to this fact advocate utilizing high-resolution fashions when finding out water cycle modifications in areas with advanced terrain. They hope these findings will provide worthwhile insights for enhancing the subsequent era of local weather fashions.