Characterizing basin-scale precipitation gradients in the Third Pole region using a high-resolution atmospheric simulation-based dataset

[摘要] Altitudinal precipitation gradient plays an important role in theinterpolation of precipitation in the Third Pole (TP) region, where thetopography is very complex but in situ data are very sparse. This study proves that the altitude dependence of precipitation in the TP can bereasonably reproduced by a high-resolution atmospheric simulation-baseddataset called ERA5_CNN. The precipitation gradients,including both absolute (APGs) and relative gradients (RPGs), for 388 sub-basins of the TP above 2500 m a.s.l. are calculated based on theERA5_CNN. Results show that most sub-basins have positiveprecipitation gradients, and negative gradients are mainly found along theHimalayas, the Hengduan Mountains and the western Kunlun. The annual APG and RPG averaged across all sub-basins of the TP are 0.05 mm d −1   ×  100 m −1 and 4.25 %  ×  100 m −1 , respectively. The values of the APG are large in wet seasons but small in dry seasons, while the RPG shows oppositevariations. Further analyses demonstrate that the RPGs have negativecorrelations with relative humidity but positive correlations with windspeed, likely because dry air tends to reach saturation at high altitudes,while stronger wind can bring more humid air to high altitudes. In addition,we find that precipitation gradients tend to be positive at small spatialscales compared to those at large scales, mainly because local topographyplays a vital role in determining precipitation distribution at smallscales. These findings on the spatiotemporal variations of precipitationgradients provide useful information for interpolating precipitation in theTP region.

[学科分类] 妇产科学