In January 2013,a severe fog and haze event(FHE)of strong intensity,long duration,and extensive coverage occurred in eastern China.The present study investigates meteorological conditions for this FHE by diagnosing bo...In January 2013,a severe fog and haze event(FHE)of strong intensity,long duration,and extensive coverage occurred in eastern China.The present study investigates meteorological conditions for this FHE by diagnosing both its atmospheric background fields and daily evolution in January 2013.The results show that a weak East Asian winter monsoon existed in January2013.Over eastern China,the anomalous southerly winds in the middle and lower troposphere are favorable for more water vapor transported to eastern China.An anomalous high at 500 hPa suppresses convection.The weakened surface winds are favorable for the fog and haze concentrating in eastern China.The reduction of the vertical shear of horizontal winds weakens the synoptic disturbances and vertical mixing of atmosphere.The anomalous inversion in near-surface increases the stability of surface air.All these meteorological background fields in January 2013 were conducive to the maintenance and development of fog and haze over eastern China.The diagnosis of the daily evolution of the FHE shows that the surface wind velocity and the vertical shear of horizontal winds in the middle and lower troposphere can exert dynamic effects on fog and haze.The larger(smaller)they are,the weaker(stronger)the fog and haze are.The thermodynamic effects include stratification instability in middle and lower troposphere and the inversion and dew-point deficit in near-surface.The larger(smaller)the stratification instability and the inversion are,the stronger(weaker)the fog and haze are.Meanwhile,the smaller(larger)the dewpoint deficit is,the stronger(weaker)the fog and haze are.Based on the meteorological factors,a multi-variate linear regression model is set up.The model results show that the dynamic and thermodynamic effects on the variance of the fog and haze evolution are almost the same.The contribution of the meteorological factors to the variance of the daily fog and haze evolution reaches 0.68,which explains more than 2/3 of the variance.展开更多
Projection of future climate changes and their regional impact is critical for long-term planning at the national and regional levels aimed at adaptation and mitigation. This study assesses the future changes in preci...Projection of future climate changes and their regional impact is critical for long-term planning at the national and regional levels aimed at adaptation and mitigation. This study assesses the future changes in precipitation in China and the associated atmospheric circulation patterns using the Couple Model Intercomparison Project 5 Phase (CMIP5) simulations under the RCP4.5 and RCP8.5 scenarios. The results consistently indicate that the annual precipitation in China is projected to significantly increase at the end of the 21st century compared to the present-day levels. The number of days and the intensity of medium rain, large rain and heavy rain are obviously increased, while the number of trace rain days is projected to decrease over the entire area of China. Further analysis indicates that the significant increase of annual precipitation in Northwest China is primarily due to the increase of light rain and the increases in North and Northeast China are primarily due to the increase of medium rain. In the region of southern China, the increases of large rain and heavy rain play an important role in the increase of annual precipitation, while light rain events play a negative role. Analysis of the changes in atmospheric circulation indicates that the East Asian summer monsoon circulation is projected to be considerably stronger, and the local atmospheric stratification is projected to be more unstable, all of which provide a background benefit for the increase of precipitation and extreme rainfall events in China under global warming scenarios.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.41221064)the International S&T Cooperation Project othe Ministry of Science and Technology of China(Grant No.2009-DFA21430)
文摘In January 2013,a severe fog and haze event(FHE)of strong intensity,long duration,and extensive coverage occurred in eastern China.The present study investigates meteorological conditions for this FHE by diagnosing both its atmospheric background fields and daily evolution in January 2013.The results show that a weak East Asian winter monsoon existed in January2013.Over eastern China,the anomalous southerly winds in the middle and lower troposphere are favorable for more water vapor transported to eastern China.An anomalous high at 500 hPa suppresses convection.The weakened surface winds are favorable for the fog and haze concentrating in eastern China.The reduction of the vertical shear of horizontal winds weakens the synoptic disturbances and vertical mixing of atmosphere.The anomalous inversion in near-surface increases the stability of surface air.All these meteorological background fields in January 2013 were conducive to the maintenance and development of fog and haze over eastern China.The diagnosis of the daily evolution of the FHE shows that the surface wind velocity and the vertical shear of horizontal winds in the middle and lower troposphere can exert dynamic effects on fog and haze.The larger(smaller)they are,the weaker(stronger)the fog and haze are.The thermodynamic effects include stratification instability in middle and lower troposphere and the inversion and dew-point deficit in near-surface.The larger(smaller)the stratification instability and the inversion are,the stronger(weaker)the fog and haze are.Meanwhile,the smaller(larger)the dewpoint deficit is,the stronger(weaker)the fog and haze are.Based on the meteorological factors,a multi-variate linear regression model is set up.The model results show that the dynamic and thermodynamic effects on the variance of the fog and haze evolution are almost the same.The contribution of the meteorological factors to the variance of the daily fog and haze evolution reaches 0.68,which explains more than 2/3 of the variance.
基金supported by the National Basic Research Program of China (2012CB955401)the "Strategic Priority Research Program-Climate Change: Carbon Budget and Relevant Issues" of the Chinese Academy of Sciences (XDA05090306)+1 种基金the National Natural Science Foundation of China (41275075)the CAS-CSIRO Cooperative Research Program (GJHZ1223)
文摘Projection of future climate changes and their regional impact is critical for long-term planning at the national and regional levels aimed at adaptation and mitigation. This study assesses the future changes in precipitation in China and the associated atmospheric circulation patterns using the Couple Model Intercomparison Project 5 Phase (CMIP5) simulations under the RCP4.5 and RCP8.5 scenarios. The results consistently indicate that the annual precipitation in China is projected to significantly increase at the end of the 21st century compared to the present-day levels. The number of days and the intensity of medium rain, large rain and heavy rain are obviously increased, while the number of trace rain days is projected to decrease over the entire area of China. Further analysis indicates that the significant increase of annual precipitation in Northwest China is primarily due to the increase of light rain and the increases in North and Northeast China are primarily due to the increase of medium rain. In the region of southern China, the increases of large rain and heavy rain play an important role in the increase of annual precipitation, while light rain events play a negative role. Analysis of the changes in atmospheric circulation indicates that the East Asian summer monsoon circulation is projected to be considerably stronger, and the local atmospheric stratification is projected to be more unstable, all of which provide a background benefit for the increase of precipitation and extreme rainfall events in China under global warming scenarios.
