1School of Geography and Planning, Nanning Normal University, Nanning 530001, China 2Guangxi Institute of Meteorological Sciences, Nanning 530022, China 3Laboratory of Beihai National Climate Observatory, Nanning 530022, China;2.1Guangxi Institute of Meteorological Sciences, Nanning 530022, China 2Laboratory of Beihai National Climate Observatory, Nanning 530022, China;3.广西南宁市民族大道81号
Based on the satellite derived snow depth over the Tibetan Plateau (TP), daily rainfall data of 261 meteorological stations in South China (SC) and the ERA5 reanalysis dataset during 1979-2018, relationships between the TP winter snow depth and precipitation during the first rainy season (FRS) in SC have been investigated. Results show that: (1) Connections between snow depth over the western TP and precipitation during the FRS in SC are the most robust and the TP snow depth mainly affects frontal precipitation of the FSR, whereas it shows less impact on summer monsoonal rainfall. (2) Onset date of the FRS in above normal TP snow years is about 20 days earlier than that in below normal snow years, leading to more rainy days, longer of the FRS and more rainfall during the FRS. However, rainfall intensity during the FRS shows small difference between different types of the TP snow years. (3) The TP is colder in above normal snow year and the cooling effect stimulates an abnormal anticyclonic circulation over the TP. However, tripole anomaly patterns of 500 hPa geopotential height occur at East Asian coastal region. Configurations of the circulation facilitate cold air in middle-high latitude regions invade SC, which makes a colder SC. And the enhanced northwest Pacific subtropical high intensifies the low-level southerly flow and water vapor supplement. The front swings northward-southward in northern part of the SC during March-April. The FRS has been established once the dry cold northerly and the warm-wet southerly flow invade the SC in early April. In below normal TP snow years, both the cold northerly and warm southerly flow are weak and inactivity and the front in northern part of the SC is interrupted in early April. When the northerly and southerly flow invades the SC in mid-to-late April, the front is reverted and the FRS occurs later.
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