Application of lidar in the observation of atmospheric particulate pollutants in Taipei
Journal
Proceedings of SPIE - The International Society for Optical Engineering
Journal Volume
6299
Date Issued
2006
Author(s)
Abstract
For the assessment of climatic impact of aerosols, the knowledge of both the temporal and spatial distributions of aerosol is essential. Laser radar, more popularly known as Lidar, has becoming one of the most powerful techniques for active detection of aerosols in the atmosphere. Lidar can provide vertically resolved of extinction and backscatter coefficients, and thereby the height of the planetary boundary layer or the nighttime residual layer. As the long-term changes in the structure and dynamics of the lower and middle troposphere is now becoming a priority, a pulsed Nd:YAG Lidar system is applied for measuring the vertical distribution of aerosol properties in the metropolitan Taipei. Two years (2004-2005) of aerosol optical depth (AOD) measured by Lidar, Cimel Sunphotometer and MODerate resolution Imaging Spectroradiometer (MODIS) were compared. The AOD shows strong seasonal variation with maximum values (AODLidar > 1, AODCimel > 1 and AODMODIS > 0.39) occurred in April. AODMODIS shows significant underestimation. AODLidar has good correlation with AODCimel, but the Lidar measurement is biased toward lower values as presented by the 0.725 slope in the linear regression. This bias is mostly caused by the Lidar blind distance at the lowest part of the atmosphere. The R-squared of AODCimel and surface PM2.5 concentration is about 0.44. This reflects the fact that the atmospheric boundary layer is often not well-mixed, so aerosols there cannot represent the total AOD value. Particles in the free troposphere also need to be concerned. Further comparison of our Lidar data with the CALIPSO measurements is intended.
SDGs
Type
conference paper