Analysis of aerosol vertical distribution and variability in Hong Kong
Analysis of aerosol vertical distribution and variability in Hong Kong
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DOI：
10.1029/2008jd009778
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发表时间：
2008-07
影响因子：
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通讯作者：
Qianshan He;LI Chengcai;J. Mao;A. Lau;D. Chu
中科院分区：
文献类型：
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作者：
Qianshan He;LI Chengcai;J. Mao;A. Lau;D. Chu
气溶胶垂直分布是提高卫星遥感气溶胶反演精度的重要信息。利用激光雷达测量可以得到气溶胶消光系数廓线及其积分形式、气溶胶光学厚度(AOD)以及大气边界层(ABL)高度和灰霾层高度。本文利用2003年5月至2004年6月的微脉冲激光雷达观测资料，分析了香港地区气溶胶光学厚度和高度的季节变化。月平均气溶胶光学厚度的约%由混合层内的气溶胶贡献(最大值(∼76%)在11月，最小值(∼55%)在9月)，这表明由于区域输送，在大气边界层上方存在大量气溶胶。研究期间，香港上空气溶胶的季节平均廓线特征被用来说明气溶胶输送的季节现象和相关的气象条件。大气气溶胶光学厚度与地表消光系数之间的相关性一般较差(R2∼0.42)，这是因为气溶胶层的升高增加了柱状气溶胶的丰度，而不是地表消光。大气边界层中典型的气溶胶消光廓线的特征是近地表有一个低值，并且随着高度的增加而增大。在假定气溶胶垂直廓线的情况下，可以利用两种算法由气溶胶光学厚度推算出地表消光系数，本文对这两种算法进行了详细的讨论。初步分析表明，两层气溶胶消光廓线(R2∼0.78、SLOPE∼0.82和Intercept∼0.15)比均匀消光廓线(R2∼0.65、SLOPE∼0.27和Intercept∼0.03)能更好地估计地面消光系数。这种相关性的改进在绘制卫星反演的气溶胶光学厚度与地表气溶胶消光系数的地图方面是有希望的，用于城市和区域环境研究与空气质量相关的问题。
Aerosol vertical distribution is an important piece of information to improve aerosol retrieval from satellite remote sensing. Aerosol extinction coefficient profile and its integral form, aerosol optical depth (AOD), as well as atmospheric boundary layer (ABL) height and haze layer height can be derived using lidar measurements. In this paper, we used micropulse lidar measurements acquired from May 2003 to June 2004 to illustrate seasonal variations of AOD and ABL height in Hong Kong. On average, about 64% of monthly mean aerosol optical depths were contributed by aerosols within the mixing layer (with a maximum (∼76%) in November and a minimum (∼55%) in September) revealing the existence of large abundance of aerosols above ABL due to regional transport. The characteristics of seasonal averaged aerosol profiles over Hong Kong in the study period are presented to illustrate seasonal phenomena of aerosol transport and associated meteorological conditions. The correlation between AOD and surface extinction coefficient, as found, is generally poor (r2 ∼0.42) since elevated aerosol layers increase columnar aerosol abundance but not extinction at surface. The typical aerosol extinction profile in the ABL can be characterized by a low value near the surface and values increased with altitude reaching the top of ABL. When aerosol vertical profile is assumed, surface extinction coefficient can be derived from AOD using two algorithms, which are discussed in detail in this paper. Preliminary analysis showed that better estimates of the extinction coefficient at the ground level could be obtained using two‐layer aerosol extinction profiles (r2 ∼0.78, slope ∼0.82, and intercept ∼0.15) than uniform profiles of extinction with height within the ABL (r2 ∼0.65, slope ∼0.27, and intercept ∼0.03). The improvement in correlation is promising on mapping satellite retrieved AOD to surface aerosol extinction coefficient for urban and regional environmental studies on air quality related issues.