Estimation of net radiation over complex urban environment - A case study of Hong Kong

Net radiation is one among the important indicators of global climate change, it empower to distinguish the changes in local meteorological condition due to local anthropogenic activity or global climate change. This study measured net radiation over Hong Kong using ASTER level 1B satellite images of 30-Nov-2007, 11 am local time. The aerosol and atmospheric models in 6S atmospheric correction algorithms were defined using locally measured sun photometer and radiosonde values respectively. Simple and efficient emissivity technique was adopted for the calculation of emissivity and net radiation. The net radiation values in this study range between 35 and 975 watts/meter square, some pixels within the city possess high net radiation value when compared to rural area, which was evident that the anthropogenic activities have impact on net radiation. The net radiation measured using satellite image was validated using net radiometers; both the values were almost equal. The satellite measured net radiation value along with field validation is the first study in Hong Kong. The techniques used here can be adopted for any city in the world possess complex urban environment similar to Hong Kong.