A heavy-rainfall event that occurred in North China during 19–20 July 2016,resulting in severe flooding,was investigated in this study.In this event,high-value total deformation overlapped the precipitation region,im...A heavy-rainfall event that occurred in North China during 19–20 July 2016,resulting in severe flooding,was investigated in this study.In this event,high-value total deformation overlapped the precipitation region,implying a close relationship between them.By deriving the nongeostrophicωequation in a non-uniformly saturated moist atmosphere,the relation between vertical velocity and deformation was diagnosed.The Q-vector divergence on the right-hand side of the newωequation was divided into three compositions,associated with horizontal divergence,vertical vorticity,and horizontal-wind deformation,respectively.It was found that the deformation component of Q-vector divergence contributed most to the negative Q-vector divergence in the precipitation region,implying an important role of deformation forcing in facilitating the vertical motion.In order to track the precipitation on the basis of deformation,potential deformation was proposed by virtue of the generalized potential temperature.The high-value potential deformation and precipitation were always overlapping,and shared an analogous temporal trend.This means that potential deformation can reflect the variation of heavy precipitation to a certain extent,and can serve as a tracker of the precipitation region.展开更多
This paper demonstrates that,for a moist baroclinic frontal system,the large-value deformation belt in the low-level atmosphere overlaps with precipitation.To precisely describe the relationship between deformation an...This paper demonstrates that,for a moist baroclinic frontal system,the large-value deformation belt in the low-level atmosphere overlaps with precipitation.To precisely describe the relationship between deformation and heavy precipitation,deformation is introduced into the nongeostrophic Q^#-vector.Q^#is then decomposed into three parts:the divergence-related term,the vorticity-related term,and the deformation-related term.By calculating the divergence of Q#and its components,it is found that in strong ascending areas within precipitation regions the nongeostrophic Q^#-vector divergence shows strong negative values.Its deformational component can contribute about 68%to these negative values.This verifies that strong deformation in a precipitating atmosphere is favorable for the development of convection and precipitation.In addition,by calculating the correlation coefficients between the Q^#-vector(including its components)divergence and vertical motions,it is also found that the Q^#-vector divergence shows higher correlation with vertical motion within the precipitation belt and lower correlation in the non-precipitation areas,which indicates a larger contribution of Q^#to vertical motion when precipitation occurs and implies an effect of Q^#to the precipitation distribution or spatial variability.Among the three components of the Q^#-vector,the correlation coefficients between the deformational component and vertical motion are the most similar in pattern to that of the correlation coefficients between the Q#-vector and vertical motion,which further reflects the important contribution of deformation to the large spatial variability of precipitation.展开更多
基金supported by the Strategic Pilot Science and Technology Special Program of the Chinese Academy of Sciences(XDA17010105)the Special Scientific Research Fund of the Meteorological Public Welfare of the Ministry of Sciences and Technology(GYHY201406002)+2 种基金the Science and Technology Project of Guangzhou(201604020069)the National Natural Science Foundation of China(41505040,41575065,and 4177510)the Open Projects of the Plateau Atmosphere and Environment Key Laboratory of Sichuan Province(PAEKL-2015-K2)
文摘A heavy-rainfall event that occurred in North China during 19–20 July 2016,resulting in severe flooding,was investigated in this study.In this event,high-value total deformation overlapped the precipitation region,implying a close relationship between them.By deriving the nongeostrophicωequation in a non-uniformly saturated moist atmosphere,the relation between vertical velocity and deformation was diagnosed.The Q-vector divergence on the right-hand side of the newωequation was divided into three compositions,associated with horizontal divergence,vertical vorticity,and horizontal-wind deformation,respectively.It was found that the deformation component of Q-vector divergence contributed most to the negative Q-vector divergence in the precipitation region,implying an important role of deformation forcing in facilitating the vertical motion.In order to track the precipitation on the basis of deformation,potential deformation was proposed by virtue of the generalized potential temperature.The high-value potential deformation and precipitation were always overlapping,and shared an analogous temporal trend.This means that potential deformation can reflect the variation of heavy precipitation to a certain extent,and can serve as a tracker of the precipitation region.
基金supported by the National Basic Key Research Program of China(Grant No.2015CB452804)the National Key Technology Research and Development Program of China(Grant No.2015BAC03B04)+2 种基金the National Natural Science Foundation of China(Grant Nos.41505040,91437215,41575047,41575065,4177510)the Open Projects of the Plateau Atmosphere and Environment Key Laboratory of Sichuan Province(Grant No.PAEKL-2015-K2)the Guangzhou Science and Technology Planning Project(201604020069)
文摘This paper demonstrates that,for a moist baroclinic frontal system,the large-value deformation belt in the low-level atmosphere overlaps with precipitation.To precisely describe the relationship between deformation and heavy precipitation,deformation is introduced into the nongeostrophic Q^#-vector.Q^#is then decomposed into three parts:the divergence-related term,the vorticity-related term,and the deformation-related term.By calculating the divergence of Q#and its components,it is found that in strong ascending areas within precipitation regions the nongeostrophic Q^#-vector divergence shows strong negative values.Its deformational component can contribute about 68%to these negative values.This verifies that strong deformation in a precipitating atmosphere is favorable for the development of convection and precipitation.In addition,by calculating the correlation coefficients between the Q^#-vector(including its components)divergence and vertical motions,it is also found that the Q^#-vector divergence shows higher correlation with vertical motion within the precipitation belt and lower correlation in the non-precipitation areas,which indicates a larger contribution of Q^#to vertical motion when precipitation occurs and implies an effect of Q^#to the precipitation distribution or spatial variability.Among the three components of the Q^#-vector,the correlation coefficients between the deformational component and vertical motion are the most similar in pattern to that of the correlation coefficients between the Q#-vector and vertical motion,which further reflects the important contribution of deformation to the large spatial variability of precipitation.
