AbstractsChemistry

Study of the boundary layer height, also known as the mixed layer height or mixing height, is of most importance to air pollution research and numerical modelling. In order to measure the mixing heights at various locations in Hong Kong, an eye-safe mobile micro-pulse lidar has been developed and deployed in field campaigns. In this thesis, the principle of lidar operation and our eye-safe mobile micro-pulse lidar design are introduced. These mobile lidar measurements are the first of their kind in Hong Kong. The advantages and limitations of using mobile lidar for mixing height determination are studied and discussed. To investigate the seasonal variation as well as the difference in mixing height at different locations, one-year periodic measurements were made at four selected sites located at the extreme edges of Hong Kong for a collaboration project with the Environmental Protection Department (EPD) during year 2003. The results show that there is a general seasonal trend of the daily maximum mixing height (MMH) among the sites. The MMH was found to be related to the temperature, wind speed and relative humidity of the atmosphere. For example, the MMH in autumn is generally the highest because of warm and dry conditions. The seasonal trend at one particular site is inconsistent with the general trend, and it will be explained in detail. Diurnal variations of the mixing height were observed and analysed with reference to meteorological parameters provided by the Hong Kong Observatory (HKO). Strong correlation between the diurnal variation and the temperature change was found. To verify our lidar data, comparisons were made with radiosonde data provided by the HKO. In addition, a road trip campaign was conducted at eight selected sites in the New Territories region of Hong Kong along a major highway during 2004 and 2005 and the results are presented. CityU Call Number: QC976.L36 C45 2005 xii, 98 leaves : ill. ; 30 cm.