Autumn rain in western China(ARWC)is a unique and significant precipitation phenomenon that occurs during the summer-to-winter transition of the atmospheric circulation.Using the fifth generation of global climate and...Autumn rain in western China(ARWC)is a unique and significant precipitation phenomenon that occurs during the summer-to-winter transition of the atmospheric circulation.Using the fifth generation of global climate and weather reanalysis data from the European Centre for Medium-Range Weather Forecasts and CN05.1 grid precipitation data,this study examined the anomalous characteristics and mechanisms of ARWC by combining the synergistic effect of the westerly jet and meridional wind.Over the past 60 years,ARWC has exhibited significant interdecadal and interannual variations,as well as a north-south seesaw pattern.The westerly jet index(meridional wind index)exhibited a negative(positive)correlation with precipitation in the northern autumn rain zone(NARZ),and a positive(negative)correlation with precipitation in the southern autumn rain zone(SARZ).The coupling of a weak meridional southerly wind with a southward westerly jet and a strong meridional southerly wind with a northward westerly jet are the two primary modes that synergistically influence the ARWC.These synergistic effects cause significant atmospheric changes throughout the troposphere.The contrasting circulation structure,temperature advection,vertical motion,and water vapor flux contributed to the opposite precipitation anomalies observed in the NARZ and SARZ.A new comprehensive index that reflects the coupled synergistic effect is proposed to characterize the anomalous changes in ARWC.This study improves the understanding of the anomalous characteristics and mechanisms of ARWC.展开更多
利用NCEP/NCAR再分析数据集和CMAP(Climate Prediction Center Merged Analysis of Precipitation)降水资料,分析了东亚副热带夏季风与热带夏季风的区别和联系,以及两者相互作用问题,深入讨论了东亚副热带季风的本质。分析发现东亚副热...利用NCEP/NCAR再分析数据集和CMAP(Climate Prediction Center Merged Analysis of Precipitation)降水资料,分析了东亚副热带夏季风与热带夏季风的区别和联系,以及两者相互作用问题,深入讨论了东亚副热带季风的本质。分析发现东亚副热带夏季风建立早于热带夏季风,于3月中旬已经开始建立。两者是相互独立的两个过程,前者并非是后者向北推进的结果;相反,前者建立后的突然南压有利于后者的爆发。副热带夏季风为渐进式建立,但撤退迅速;热带夏季风爆发突然,但撤退缓慢。副热带夏季风的建立以偏南风的建立为特征,而热带夏季风的建立以偏东风向偏西风转变为特征。热带夏季风的建立时间取决于经向海陆热力差异转向,而东亚副热带夏季风则更依赖于纬向海陆热力差异的逆转。亚洲大陆(含青藏高原)与西太平洋之间的纬向海陆热力差异的季节逆转无论对东亚副热带夏季风还是热带夏季风均有重要作用。展开更多
基金National Natural Science Foundation of China(42030611)Second Tibetan Plateau Scientific Expedition and Research(STEP)Program(2019QZKK0103)。
文摘Autumn rain in western China(ARWC)is a unique and significant precipitation phenomenon that occurs during the summer-to-winter transition of the atmospheric circulation.Using the fifth generation of global climate and weather reanalysis data from the European Centre for Medium-Range Weather Forecasts and CN05.1 grid precipitation data,this study examined the anomalous characteristics and mechanisms of ARWC by combining the synergistic effect of the westerly jet and meridional wind.Over the past 60 years,ARWC has exhibited significant interdecadal and interannual variations,as well as a north-south seesaw pattern.The westerly jet index(meridional wind index)exhibited a negative(positive)correlation with precipitation in the northern autumn rain zone(NARZ),and a positive(negative)correlation with precipitation in the southern autumn rain zone(SARZ).The coupling of a weak meridional southerly wind with a southward westerly jet and a strong meridional southerly wind with a northward westerly jet are the two primary modes that synergistically influence the ARWC.These synergistic effects cause significant atmospheric changes throughout the troposphere.The contrasting circulation structure,temperature advection,vertical motion,and water vapor flux contributed to the opposite precipitation anomalies observed in the NARZ and SARZ.A new comprehensive index that reflects the coupled synergistic effect is proposed to characterize the anomalous changes in ARWC.This study improves the understanding of the anomalous characteristics and mechanisms of ARWC.
文摘利用NCEP/NCAR再分析数据集和CMAP(Climate Prediction Center Merged Analysis of Precipitation)降水资料,分析了东亚副热带夏季风与热带夏季风的区别和联系,以及两者相互作用问题,深入讨论了东亚副热带季风的本质。分析发现东亚副热带夏季风建立早于热带夏季风,于3月中旬已经开始建立。两者是相互独立的两个过程,前者并非是后者向北推进的结果;相反,前者建立后的突然南压有利于后者的爆发。副热带夏季风为渐进式建立,但撤退迅速;热带夏季风爆发突然,但撤退缓慢。副热带夏季风的建立以偏南风的建立为特征,而热带夏季风的建立以偏东风向偏西风转变为特征。热带夏季风的建立时间取决于经向海陆热力差异转向,而东亚副热带夏季风则更依赖于纬向海陆热力差异的逆转。亚洲大陆(含青藏高原)与西太平洋之间的纬向海陆热力差异的季节逆转无论对东亚副热带夏季风还是热带夏季风均有重要作用。
