Water Vapor Transport Characteristics Of Winter Precipitation In Jinhua Area In Recent 50 Years

In order to explore the water vapor transport characteristics of winter precipitation in Jinhua area in recent 50 years,understand the winter precipitation characteristics of Jinhua area under different large circulation background,reveal the law of winter precipitation in Jinhua area and even the whole southern area,and the corresponding impact on global climate.Based on the observed precipitation data from 1971 to 2018 and NCEP reanalysis data as well as HYSPLIT model,this paper analyzes the variation characteristics of winter precipitation and precipitation days in Jinhua area in recent 50 years,analyzes the water vapor transport characteristics of winter precipitation in Jinhua area in recent 50 years,and simulates the water vapor source,path and contribution rate of water vapor in the different height layers in 1971-1977,1978-1999 and 2000-2018.Combined with the water vapor flux and water vapor flux divergence at different height layers in three time periods,the differences of water vapor transport in different periods are analyzed,and the main influencing factors of winter precipitation change in Jinhua area are discussed.On this basis,a typical abnormal precipitation in each period is selected to analyze its water vapor transport and circulation characteristics in detail.The main results are as follows:(1)From 1971 to 2018,the winter precipitation in Jinhua area showed an overall upward trend,and the precipitation days showed an obvious downward trend,indicating that the intensity of winter precipitation in Jinhua area increased,the extreme precipitation events showed an increasing trend after 2000,and the frequency of extreme precipitation increased.The precipitation,precipitation days and Precipitation intensity in December,January and February were quite different.The results showed that the winter precipitation in Jinhua area had periodic oscillation of about 4,12 and28 years,with the largest energy and the most obvious change;the periodic oscillation of winter precipitation days was not obvious on the whole,but the periodic oscillation of single month was relatively strong.(2)There are three main water vapor transport channels of winter precipitation in Jinhua area in recent 50 years: the land-based channel in Eurasia and Africa and the long-distance channel near the Mediterranean Sea and North Atlantic,the Bay of Bengal-South China Sea channel and the local water vapor channel.Water vapor mainly comes from Bay of Bengal,South China Sea,Arabian Sea,Western Pacific,North Atlantic and Mediterranean Sea.Local water vapor is the result of low-level convection and evaporation,and the water vapor transport in the Bay of Bengal and South China Sea at low latitudes have a major impact on the amount of precipitation;the upper air is mainly controlled by the westerly belt,but has a small contribution to the precipitation in the study area.The contribution rate and characteristics of water vapor transport in 1971-1977,1978-1999 and 2000-2018 are different.In 1971-1977 and2000-2018,the local channel,the Bay of Bengal-South China Sea channel were the main water vapor channels,the southwest flow of the south branch channel and the South China Sea diversion flow had stronger water vapor transportation,forming a strong convergence area,but the transport of warm and humid air in low latitude was stronger in 2000-2018.From 1978 to 1999,the local channel and Eurasia channel were the main water vapor channels,while the water vapor in the Bay of Bengal and South China Sea decreased significantly,and the water vapor in the study area was mainly dry and cold air in Eurasia.The East Asian winter monsoon,ENSO events,Indian Ocean sea surface temperature dipole(IOD)and Local evaporation are the main influencing factors of precipitation anomaly in Jinhua area in different time periods.(3)By analyzing the characteristics of water vapor transport and general circulation in 1972,1998 and 2018,it was found that the main water vapor channels in typical extreme precipitation years included the land-based channel in Eurasia and Africa,the long-distance channel near the Mediterranean Sea and North Atlantic,the Bay of Bengal-South China Sea channel,the Western Pacific channel and the local water vapor channel.Water vapor mainly came from the Bay of Bengal,South China Sea,Western Pacific,Arabian Sea and Qinghai Tibet Plateau,etc,the water vapor content was sufficient,and the low latitude water vapor transport enhanced and controlled study area.In addition,the background of general circulation such as El Ni(?)o,the positive phase of the Indian Ocean sea surface temperature dipole(IOD)and the weak East Asian winter monsoon were the main influencing factors of extreme precipitation.On the contrary,it was prone to the abnormal precipitation reduction: the main water vapor channels of typical precipitation were the land-based channel in Eurasia and Africa,the long-distance channel near the Mediterranean Sea in the North Atlantic and the Bay of Bengal-South China Sea channel,the main contribution of water vapor came from northwest inland,West Asia and Bay of Bengal-South China Sea,and the water vapor content is less.The study area was mainly controlled by the northerly cold air,and the water vapor transport from Bay of Bengal and South China Sea was weak.