气候与环境研究
氣候與環境研究
기후여배경연구
CLIMATIC AND ENVIRONMENTAL RESEARCH
2014年
6期
659-669
,共11页
激光雷达%污染天气%逆温%大气边界层%北京
激光雷達%汙染天氣%逆溫%大氣邊界層%北京
격광뢰체%오염천기%역온%대기변계층%북경
Lidar%Pollution atmosphere%Temperature inversion%Atmospheric boundary layer%Beijing
以2009年11月5～8日北京地区发生的一次特殊天气形势下的重污染天气过程为例，研究分析本次污染特点和大气边界层结构特征以及此天气过程的大气温度和相对湿度结构特点。激光雷达是探测大气边界层及气溶胶的一个高效工具，利用 ALS300激光雷达系统测量信号，应用 Fernald 方法反演大气消光系数，根据反演的气溶胶消光系数的最大突变，即最大递减率的高度来确定大气边界层的高度。利用其观测的退偏比分析大气污染物特性。利用微波辐射计数据，确定大气温度和湿度时空特征。研究结果表明：在本次污染天气下，大气具有很强的逆温结构，逆温最大可达近1 K (100 m)?1，500 m 以上的大气相对湿度很低，在这种天气特征下的大气边界层高度在400 m 左右，非常稳定。污染结束降雪开始前，大气逆温结构消失，大气湿度大幅度增加，接近饱和。根据 lidar（light detection and ranging）退偏比的分析，本次污染天气是一次典型的烟尘类颗粒物的污染，污染具有区域性特点。PM2.5（空气动力学当量直径小于等于2.5μm 的颗粒物）与 AOT（Aerosol Optical Thickness）之间有明显的线性关系，相关系数达到0.72。该 lidar 系统能够反演出秋季降雪前本次污染天气背景下北京城区上空的大气污染特性和大气边界层高度。
以2009年11月5～8日北京地區髮生的一次特殊天氣形勢下的重汙染天氣過程為例，研究分析本次汙染特點和大氣邊界層結構特徵以及此天氣過程的大氣溫度和相對濕度結構特點。激光雷達是探測大氣邊界層及氣溶膠的一箇高效工具，利用 ALS300激光雷達繫統測量信號，應用 Fernald 方法反縯大氣消光繫數，根據反縯的氣溶膠消光繫數的最大突變，即最大遞減率的高度來確定大氣邊界層的高度。利用其觀測的退偏比分析大氣汙染物特性。利用微波輻射計數據，確定大氣溫度和濕度時空特徵。研究結果錶明：在本次汙染天氣下，大氣具有很彊的逆溫結構，逆溫最大可達近1 K (100 m)?1，500 m 以上的大氣相對濕度很低，在這種天氣特徵下的大氣邊界層高度在400 m 左右，非常穩定。汙染結束降雪開始前，大氣逆溫結構消失，大氣濕度大幅度增加，接近飽和。根據 lidar（light detection and ranging）退偏比的分析，本次汙染天氣是一次典型的煙塵類顆粒物的汙染，汙染具有區域性特點。PM2.5（空氣動力學噹量直徑小于等于2.5μm 的顆粒物）與 AOT（Aerosol Optical Thickness）之間有明顯的線性關繫，相關繫數達到0.72。該 lidar 繫統能夠反縯齣鞦季降雪前本次汙染天氣揹景下北京城區上空的大氣汙染特性和大氣邊界層高度。
이2009년11월5～8일북경지구발생적일차특수천기형세하적중오염천기과정위례，연구분석본차오염특점화대기변계층결구특정이급차천기과정적대기온도화상대습도결구특점。격광뢰체시탐측대기변계층급기용효적일개고효공구，이용 ALS300격광뢰체계통측량신호，응용 Fernald 방법반연대기소광계수，근거반연적기용효소광계수적최대돌변，즉최대체감솔적고도래학정대기변계층적고도。이용기관측적퇴편비분석대기오염물특성。이용미파복사계수거，학정대기온도화습도시공특정。연구결과표명：재본차오염천기하，대기구유흔강적역온결구，역온최대가체근1 K (100 m)?1，500 m 이상적대기상대습도흔저，재저충천기특정하적대기변계층고도재400 m 좌우，비상은정。오염결속강설개시전，대기역온결구소실，대기습도대폭도증가，접근포화。근거 lidar（light detection and ranging）퇴편비적분석，본차오염천기시일차전형적연진류과립물적오염，오염구유구역성특점。PM2.5（공기동역학당량직경소우등우2.5μm 적과립물）여 AOT（Aerosol Optical Thickness）지간유명현적선성관계，상관계수체도0.72。해 lidar 계통능구반연출추계강설전본차오염천기배경하북경성구상공적대기오염특성화대기변계층고도。
Lidar measurements were performed at a heavily polluted site between 5 Nov 2009 and 8 Nov 2009. Aerosol extinction coefficients, AOT (Aerosol Optical Thickness), and depolarization ratio were measured, temperature and relative humidity profiles were acquired from a microwave radiometer. Lidar is an efficient tool for detecting the ABL (Atmospheric Boundary Layer) and atmospheric aerosols. In this study, the aerosol extinction coefficient was retrieved from the measured signal of an ALS300 lidar system using the Fernald method. The ABL height was determined according to the maximum inflexion point of the inversed aerosol extinction coefficient (the height of the maximum decline rate). Atmospheric pollutant characteristics were analyzed using the depolarization ratio from the lidar. The temperature and relative humidity structure of air were obtained from microwave radiometer data. The results show that under the air pollution conditions, the atmosphere had a strong temperature inversion layer, with an inversion intensity up to 1 K (100 m)-1, and a very low atmospheric relative humidity above 500 m; the atmosphere was highly stable. After the pollution events and before the start of snowfall, the inversion structure disappeared and the relative humidity increased significantly to reach saturation. Lidar depolarization ratio analysis indicated the pollution type to be a typical soot particulate matter pollution with regional characteristics. There was a significant linear relationship between PM2.5 and AOT, with a correlation coefficient of 0.72. Our results show that lidar systems can detect air pollution characteristics and ABL height in polluted weather before snowfall in autumn in urban Beijing.
