Projections of summer light rain frequency in typical terrain over eastern China under wind speed constraint

Abstract

The variation in near-surface wind speed is a key dynamic parameter in the orographic effect of precipitation over eastern China. In this study, we used the latest high-resolution outputs from six GCMs in CMIP6-HighResMIP to evaluate the performance of high-resolution models in simulating the orographic precipitation characteristics of typical mountainous areas in summer over eastern China. The orographic precipitation under warming scenarios was projected and constrained according to observational data. The results indicated that during the contemporary climate reference period (1979–2009), although the relationship between model-simulated near-surface wind speed and orographic light rain frequency was consistently stable, the sensitivity of the orographic light rain frequency to surface wind variability was generally underestimated, with a deviation approximately 24.1% lower than the observational values. The estimated orographic light rain frequency corrected based on the observed near-surface wind speed under a 1.5°C warming scenario, was 36.1% lower than that of the contemporary period; this reduction was 8.6 times that without the wind speed constraint (4.2%). The MRI-AGCM3-2-S model, with a longer dataset, demonstrated relatively stable reductions in orographic light rain frequency under different warming scenarios (1.5°C, 2°C, 3°C, and 4°C) after the application of wind speed constraints. In all cases, the reductions exceeded those for the predictions made without the wind speed constraint.