Hail is one of the important weather disasters that affects the Beijing-Tianjin(BT) region.To better understand and to improve the forecasting of hail events over the BT region,the precursor weather conditions for hai...Hail is one of the important weather disasters that affects the Beijing-Tianjin(BT) region.To better understand and to improve the forecasting of hail events over the BT region,the precursor weather conditions for hail based on 30 previous hail events were derived.It was found that the high-level trough and low-level cold front over the Mongolian region,the accumulated convective available potential energy,the decrease of the height of the 0℃-isotherm in the morning,and the persistence and intensification of these factors from morning to afternoon are valuable clues for forecasting the occurrence of hail events over the BT region.展开更多
To better understand the characteristics of air quality and the relationship between the chemical composition evolution and source variation,an intensive atmospheric campaign was conducted in Tianjin,a megacity of the...To better understand the characteristics of air quality and the relationship between the chemical composition evolution and source variation,an intensive atmospheric campaign was conducted in Tianjin,a megacity of the North China Plain,from 10 February to 6 March 2015.There were 20 days exceeding the threshold value of secondary Chinese Ambient Air Quality Standards for PM2.5(75 μg m-3,daily average over 24 h)during the study period.Five air pollution episodes were selected for investigation.During the pre-holiday pollution episode,NH^+_4,NO^-_3,and SO^(2-)_4 were more abundant,indicating that air pollution was caused by motor vehicle exhaust emissions and coal consumption under unfavorable meteorological conditions.During Chinese Lunar New Year's Eve,widespread use of fireworks resulted in extremely high aerosol concentrations.Firework displays caused increases in K+ and also enrichment of SO^(2-)_4 relative to NO^-_3.The holiday pollution episode was caused by regional transport,characterized by abundant SO^(2-)_4 and NH^+_4.In addition,the aging processes of the particles from fireworks discharge played an important role in the formation of NO-3and SO^(2-)_4.The Lantern Festival episode was characterized by a transition from the enrichment of K+ to secondary inorganic ions(NO^-_3,SO^(2-)_4,and NH^+_4).The results of this study are useful for a detailed understanding of the variation in atmospheric compositions and sources caused by anthropogenic activity,and highlight the importance of controlling intensive fireworks discharge.展开更多
基金supported by the Scientific Research Foundation for Returned Scholars of the State Personnel Ministry of China,the Research Foundation of Institute of Urban Meteorology, CMA (Grant No. UMRF 200809)the R&D Special Fund for Public Welfare Industry (Meteorology) (Grant No. GYHY200906003)the National Basic Research Program of China (Grant No. 2009CB421406)
文摘Hail is one of the important weather disasters that affects the Beijing-Tianjin(BT) region.To better understand and to improve the forecasting of hail events over the BT region,the precursor weather conditions for hail based on 30 previous hail events were derived.It was found that the high-level trough and low-level cold front over the Mongolian region,the accumulated convective available potential energy,the decrease of the height of the 0℃-isotherm in the morning,and the persistence and intensification of these factors from morning to afternoon are valuable clues for forecasting the occurrence of hail events over the BT region.
基金supported by the Beijing Natural Science Foundation[grant number 8142034]Strategic Priority Research Program(B)of the Chinese Academy of Sciences[grant numbers XDB0502050 and XDB05030203]
文摘To better understand the characteristics of air quality and the relationship between the chemical composition evolution and source variation,an intensive atmospheric campaign was conducted in Tianjin,a megacity of the North China Plain,from 10 February to 6 March 2015.There were 20 days exceeding the threshold value of secondary Chinese Ambient Air Quality Standards for PM2.5(75 μg m-3,daily average over 24 h)during the study period.Five air pollution episodes were selected for investigation.During the pre-holiday pollution episode,NH^+_4,NO^-_3,and SO^(2-)_4 were more abundant,indicating that air pollution was caused by motor vehicle exhaust emissions and coal consumption under unfavorable meteorological conditions.During Chinese Lunar New Year's Eve,widespread use of fireworks resulted in extremely high aerosol concentrations.Firework displays caused increases in K+ and also enrichment of SO^(2-)_4 relative to NO^-_3.The holiday pollution episode was caused by regional transport,characterized by abundant SO^(2-)_4 and NH^+_4.In addition,the aging processes of the particles from fireworks discharge played an important role in the formation of NO-3and SO^(2-)_4.The Lantern Festival episode was characterized by a transition from the enrichment of K+ to secondary inorganic ions(NO^-_3,SO^(2-)_4,and NH^+_4).The results of this study are useful for a detailed understanding of the variation in atmospheric compositions and sources caused by anthropogenic activity,and highlight the importance of controlling intensive fireworks discharge.
