Diagnosis of deformation-derived ascending areas in a rainband

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.

Deformation characteristics of the ‘7.20' heavy rainfall event in North China

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.

Impacts of the atmospheric apparent heat source over the Tibetan Plateau on summertime ozone vertical distributions over Lhasa

The Tibetan Plateau(TP)is an area sensitive to climate change,where the ozone distribution affects the atmospheric environment of the TP and its surrounding regions.The relatively low total column ozone over the TP in boreal summer and its spatiotemporal variations have received extensive attention.In this study,five-year balloon-borne measurements of ozone over Lhasa in boreal summer are used to investigate the influences of the apparent heat source(Q1)on the ozone vertical structure over the plateau.The mechanisms for the above processes are also explored.The results show that the tropospheric ozone mixing ratio over Lhasa decreases when the total atmospheric Q1 in the troposphere over the TP is relatively high.Strengthened ascending motions are accompanied by enhanced Q1 over the main TP region.Consequently,the tropospheric ozone mixing ratio over Lhasa decreases when Q1 is higher in summer,which is attributed to the upward transport of the ozone-poor surface air.

Diagnosis Analysis of One Cold Airflow Snowfall in Shandong Peninsula

[Objective]One cold airflow snowfall in Shandong Peninsula was analyzed.[Method] Using conventional weather observation data,the NCEP /NCAR 1° ×1° grid point by 6 h in data analysis,the synoptic weather dynamics principle and diagnosis analysis method,the cold airflow snowfall in Shandong Peninsula on December 4,2008 to 6 th was analyzed and summarized.[Result]The results showed that the cold deep groove of large scale circulation form caused the cold airflow snowfall in Shandong Peninsula.While the 850 hPa mistral wind strengthened,cold airflow snow in Shandong Peninsula will be strengthened.During the eruption of snowstorm,the relative humidity from 925 to 750 hPa was larger than 90%.The area formed by 90% relative humidity line corresponded with the period of heavy snowfall.The changes of relative humidity line reflected the changes of warm and wet air transmitting to the higher place.The more warm and wet air being sent to the upper air,the more conductive to the formation of cold airflow snowfall in Shandong Peninsula.The cold airflow snowfall had distinct temporal and spatial distribution characteristics and corresponded with the vertical increasing movement zone.[Conclusion]The study provided reference for the preciseness of short term and incoming report of cold airflow snowfall in Shandong Peninsula.