Climatic Characteristics and Possible Causes of Continuous Rainy Weather in Henan Province during the Wheat Harvest Season in 2023
During the wheat harvest season in 2023,Henan Province suffered rare and persistent rainy weather,in which the amount of precipitation and the number of rainy or sunless days were pro-nounced high,ranking the fifth and the second since 1961,respectively.This paper analyzed the climato-logical causes of this event and the main conclusions were as follows:(1)Geopotential height anomaly at 500 hPa was positive in the west,while was negative in the east over Eurasian mid-high latitude during the wheat harvest season,the Ural Mountain ridge developed sustainably with staged blocking,and the Northeast China cold vortex(NECV)was very active,making cold air keep moving down to the south.The western Pacific subtropical high(WPSH)was much stronger than normal,located more northwards and westwards,thus the warm and humid air from the northwest edge of the WPSH and cold air could converge in Henan Province.The above circulation systems were conducive to the continuous rain.(2)The pattern of the WPSH was mainly affected by the guidance of the South Asian high(SAH)and the East Asian sub-tropical westerly jet.The Southeast Asian warm center at mid-upper level was larger,more eastward and northward than normal,having an east-west zonal distribution,which resulted in the strong,large,north-ward and eastward pattern of the SAH.The combination of the warm center and the NECV increased the temperature gradient at mid-upper level of East Asia,thus intensified the westerly jet.(3)The La Nina event in early 2023 was favorable for northward shift of the WPSH during the wheat harvest season,but wasn't conducive to the strong and distinct westward pattern of the WPSH.Due to the influence of Ty-phoon Mawa,more condensation latent heat was released by active convection from the Gulf of Thailand to tropical western Pacific east of the Philippine Islands during the wheat harvest season,meanwhile the sur-face sensible heat and the latent heat from the Iranian Plateau to the Tibetan Plateau were much stronger than normal in the spring before the wheat harvest season and during the wheat harvest season,which con-tributed to the distribution of the warm center,and ultimately determined the position and intensity of the SAH and the WPSH.(4)During the 2023 wheat harvest season,the high sea surface temperature(SST)in the North Atlantic and the negative phase of the North Atlantic tripole led to the sustained development of the Ural Mountain ridge.At the same time,the surface sensible heat and the latent heat in the spring before the wheat harvest season and during the wheat harvest season were much stronger than normal from the Volga River to the northwest of the Lake Baikal,while were weaker from the southeast of the Lake Bai-kal to the Sea of Okhotsk,which to a certain degree resulted in positive and negative geopotential height anomalies in their corresponding regions,respectively.
wheat harvest seasoncontinuous rainwestern Pacific subtropical highUral bloc-kingNortheast China cold vortexSouth Asian highwesterly jet
万方数据
维普
