Improve the downscaling accuracy of high-resolution precipitation field using classification mask

Due to the low spatial and temporal density of early meteorological observations in China, The China Meteorological Administration Land Data Assimilation System V3.0 (CLDAS3.0) could not obtain high-quality historical, high-resolution assimilated data. In particular, with high-resolution precipitation assimilation data, it is difficult to estimate the precipitation range accurately because of its substantial spatiotemporal heterogeneity. To solve this problem, our team proposes a two-stage downscaling framework for the precipitation field based on multi-task learning, CLDASSD-PRCP. It improves the accuracy of the downscaling task by predicting the precipitation classification mask first. We verify the algorithm using CLDAS3.0 and site observations as ground truth in Yunnan, China. The results show that CLDASSD-PRCP can accurately generate three types of precipitation masks and reduce the MAE of downscaling results by 0.32 mm/h after adding multi-classification masks (MutiClassesMask). In addition, the effects of light and extreme precipitation on precipitation spatial downscaling are also revealed. CLDASSD-PRCP is significant for establishing statistical downscaling models based on deep learning and provides a new way to deal with atmospheric elements with significant spatiotemporal heterogeneity. [Display omitted] •A two-stage precipitation downscaling framework CLDASSD-PRCP based on multi-task learning is proposed•The different effects of precipitation level on the downscaling task are revealed.•The feasibility of CLDASSD-PRCP in CLDAS-V3.0 historical precipitation data back-calculation is verified.