Visual Range Trends in the Yangtze River Delta Region of China during 1981-2005

摘要

Visual range (VR) data from 1981 to 2005 are examined for 20 meteorological monitoring sites in the Yangtze River Delta Region (YRDR) of China. Cumulative percentile analysis was used to construct VR trend. The 25-year average domain average 50% VR was about 21.9 ± 1.9 km. Domain average 50% VR decreased from 1981 to 2005 with a trend of -2.41 km /decade. The worst 20%, 50% and best 20% VR and variation rates for the 20 sites are analyzed. The 50% VR of the town, county-level city and prefecture-level city sites are 24.1 km, 21.5 km and 19.4 km, respectively. The best 20% VR decreased fastest with the rate -3.5 km/decade. Regional median VR decreased from the coastal sites to the inland sites. Ridit analysis and cumulative percentile have been adopted to study the VR variation properties between economically developed areas (e.g., Nanjing and Hangzhou) and remote areas (e.g., Lvsi). The two analyses both show that VR decreased in Nanjing and Hangzhou while remained constant in Lvsi from 1981 to 2005.