Subtropical High Pressure 两个全球性大气环流在 洛杉矶所在的纬度高空 Cool Air Aloft 相汇,到达这里的空气 向地表扩散沉降。空气 Inversion Layer- Warm Air 小在下沉的过程中因为被 Cool Sea Breeze 压缩而升温,在该区域 形成了一个持久的高压 沉降逆温层 坐落于洛杉矶东部的圣盖博山脉 可以阻止海风将这个区域的污染 物吹走
两个全球性大气环流在 洛杉矶所在的纬度高空 相汇，到达这里的空气 向地表扩散沉降。空气 在下沉的过程中因为被 压缩而升温，在该区域 形成了一个持久的高压 沉降逆温层。 坐落于洛杉矶东部的圣盖博山脉 可以阻止海风将这个区域的污染 物吹走
另一种典型的逆温形成机制叫辐射逆温, 相对来讲,辐射逆温出现地更频繁但不 易引发严重的污染事件。 在一个晴朗无云的夜晚,地表会向外太 空辐射热量,因此地表的温度会下降 这也同时降低了地表附近的空气温度。 经过一个晚上的冷却,第二天早上靠近 地表的空气温度会比它上面的空气温度 低些,于是就形成了辐射逆温层。 由于在夜间地表向外辐射随着上午的太阳越升越高,地表以及近 热量,近地面大气受到冷地面大气层被太阳加热,所以辐射逆温 却,以致于它的温度比其现象就会慢慢消失直到中午完全消失。 上层空气还要低
另一种典型的逆温形成机制叫辐射逆温， 相对来讲，辐射逆温出现地更频繁但不 易引发严重的污染事件。 在一个晴朗无云的夜晚，地表会向外太 空辐射热量，因此地表的温度会下降， 这也同时降低了地表附近的空气温度。 经过一个晚上的冷却，第二天早上靠近 地表的空气温度会比它上面的空气温度 低些，于是就形成了辐射逆温层。 随着上午的太阳越升越高，地表以及近 地面大气层被太阳加热，所以辐射逆温 现象就会慢慢消失直到中午完全消失。 由于在夜间地表向外辐射 热量，近地面大气受到冷 却，以致于它的温度比其 上层空气还要低
2013年月中国大陆大气环流背景 circulation med 20 130201 30d 分 →→→→+份÷-;+;+ 15N··F+v -++++、 1月56hP均wntn 13E 明全降水距平百分率180 588 近30天对流层中层东亚槽偏东、范围偏大,副热带高压略偏强偏西。尤其是 月中旬以来,我国北方冷空气势力弱,大风天气减少,中东部地区低空大气长时间 处于相对稳定的状态,冬季由于地面夜间的辐射降温明显,大气低空容易出现“逆 温层”,空气的垂直方向交换流通能力变弱,不利于空气中污染物的扩散,就形成 了越聚越多的积聚效应,导致雾霾天气多发
2013年1月中国大陆大气环流背景 近30天对流层中层东亚槽偏东、范围偏大，副热带高压略偏强偏西。尤其是一 月中旬以来，我国北方冷空气势力弱，大风天气减少，中东部地区低空大气长时间 处于相对稳定的状态，冬季由于地面夜间的辐射降温明显，大气低空容易出现“逆 温层”，空气的垂直方向交换流通能力变弱，不利于空气中污染物的扩散，就形成 了越聚越多的积聚效应，导致雾霾天气多发。 1月500hPa平均场 1月全国降水距平百分率
news views ATMOSPHERIC SCIENCE Warming boosts air pollution Atmospheric conditions play an important role in driving severe air pollution events in Beijing, China Now research finds that global warming will enhance weather conditions favouring such events, increasing the chances of severe inter-time haze in the future Renhe Zhang nature LETTERS imate change PUBLISHED ONLINE: 20 MARCH 2017 I DO1: 10. 1038/NCLIMATE3249 Weather conditions conducive to beijing severe haze more frequent under climate change Wenju Cai 12, Ke Li. 4, Hong Liao5*, Huijun Wang and Lixin Wu' The frequency of Beijing winter severe haze episodes has of episodes occurred. In January 2013, severe haze events increased substantially over the past decades, and is com- affected 30 cities-2, and the maximum daily PM2s average monly attributed to increased pollutant emissions from China's near Beijing reached 500 ug m. While the underlying cause rapid economic development. During such episodes, levels is increased pollutant emissions, local weather conditions play of fine particulate matter are harmful to human health and a part 4. 6. Further, decadal variability and change, including the environment, and cause massive disruption to economic weakened northerly winds, decreased relative humidity, reduced activities.-, as occurred in January 2013-.Conducive Arctic Sea ice, and declined East Asian winter monsoon", may weather conditions are an important ingredient of severe haze have contributed. However, no long-term PM2s observations are episodes, l, and include reduced surface winter northerlies 2, available for attribution of the increased frequency
HWI Future changes 8 P value< 0.001 1950-1999 2050-2099 of Beijing winter§7 severe haze weather conditions 4 based on climate models 82 0 2 They define a haze weather index(Hwi that describes whether meteorological conditions ( vertical air temperature difference between the lower and upper atmosphere lower tropospheric wind velocity, and midtropospheric zonal flow are favorable for extreme smog. Using observations they find that positive Hwl values (that is, favorable haze conditions have increased in frequency by 10% when comparing 1948-1981 with 1982-2015. Thus, climate change over the past several decades is thought to create weather conditions more favorable for triggering haze events BeijIng
Future changes of Beijing winter severe haze weather conditions based on climate models They define a haze weather index (HWI) that describes whether meteorological conditions (vertical air temperature difference between the lower and upper atmosphere, lower tropospheric wind velocity, and midtropospheric zonal flow) are favorable for extreme smog. Using observations, they find that positive HWI values (that is, favorable haze conditions) have increased in frequency by 10% when comparing 1948–1981 with 1982–2015. Thus, climate change over the past several decades is thought to create weather conditions more favorable for triggering haze events in Beijing