基于MODIS AOD数据的南京市大气能见度估算

以南京市为研究区,利用MODIS气溶胶产品数据(MOD04L2)获取研究区气溶胶标高数据,结合地面气象站点能见度观测数据,构建研究区不同季节能见度估算模型,估算南京市2013年能见度时空分布。研究结果表明,研究区能见度模型估算值与实测值总体趋势较为一致,分季节模型能见度估算均值相对误差为14.3%;南京市2013年能见度年均值为6.07km,大致呈现出由市区向周边郊区逐渐升高的趋势;研究区不同季节能见度差异明显,夏季能见度显著高于其他3个季节,在该季节全市能见度均值达到9.93km,约为其余3个季节均值的2倍左右,气候状况与经济社会发展布局是影响研究区能见度时空差异的主要因素。

ESTIMATING VISIBILITY OF NANJING USING MODIS AOD DATA

Visibility is one of basic parameters in meteorological observation, which can be used to represent the degree of atmospheric quality. Accurate measurement of atmospheric visibility is important for both human health and transportation. Visibility measurement through ground-based instrumentation on regional scale is lacking. In this paper, seasonal models are fitted using visibility measurement data from meteorological observation station located in Nanjing university of Information Science & Technology and aerosol scale height data from MODIS aerosol optical depth production. Using the seasonal models, visibility distribution of Nanjing in 2013 was mapped and the temporal and spatial distribution of regional visibility over the Nanjing area was analyzed. The results showed that the aerosol scale height in summer had the highest value of 1.328 km and the value in winter had the lowest value of 0.587 6 km in the Nanjing City. According to the validation of estimated visibility values using meteorological station measurement data, the average absolute error and average relative error of estimated visibility values were 1.72 km and 30.71%, respectively. The seasonal average estimated visibility values present better consistency with measurement data with the seasonal average absolute error and relative error of 1.29 km and 14%, respectively. Spatial scale difference between the observational station data and remote sensing data was the main cause of estimation error. Furthermore, the high wind speed will increase the model estimation error through the analysis of synchronous observation wind data. The annual average visibility of 2013 over the Nanjing area is 6.07 km presenting an increasing trend from the city center to the suburbs. In the study area, the visibility values in different seasons were obviously different. Visibility value of summer was 9.93 km and it was higher than the other three seasons with visibility value. According to the natural and economic conditions in study area, the spatio-temporal distribution of visibility is mainly affected by weather and the arrangement of regional economic developments. Besides, the effect of human activities was also an important factor in affecting visibility value. A large number of construction projects in the city central areas in 2013 contributed to produce local dust weather which can result in high value of visibility.