Based on the NOAA’s Advanced Very High Resolution Radiometer （AVHRR） Pathfi nder Atmospheres Extended （PATMOS-x） monthly mean cloud amount data, variations of annual and seasonal mean cloud amount over the Yangtz...Based on the NOAA’s Advanced Very High Resolution Radiometer （AVHRR） Pathfi nder Atmospheres Extended （PATMOS-x） monthly mean cloud amount data, variations of annual and seasonal mean cloud amount over the Yangtze River Delta （YRD）, China were examined for the period 1982-2006 by using a linear regression analysis. Both total and high-level cloud amounts peak in June and reach minimum in December, mid-level clouds have a peak during winter months and reach a minimum in summer, and low-level clouds vary weakly throughout the year with a weak maximum from August to October. For the annual mean cloud amount, a slightly decreasing tendency （-0.6% sky cover per decade） of total cloud amount is observed during the studying period, which is mainly due to the reduction of annual mean high-level cloud amount （-2.2% sky cover per decade）. Mid-level clouds occur least （approximately 15% sky cover） and remain invariant, while the low-level cloud amount shows a signifi cant increase during spring （1.5% sky cover per decade） and summer （3.0%sky cover per decade）. Further analysis has revealed that the increased low-level clouds during the summer season are mainly impacted by the local environment. For example, compared to the low-level cloud amounts over the adjacent rural areas （e.g., cropland, large water body, and mountain areas covered by forest）, those over and around urban agglomerations rise more dramatically.展开更多
基金Supported by the National Basic Research and Development(973)Program of China(2010CB428501)National Natural Science Foundation of China(41375014)
文摘Based on the NOAA’s Advanced Very High Resolution Radiometer （AVHRR） Pathfi nder Atmospheres Extended （PATMOS-x） monthly mean cloud amount data, variations of annual and seasonal mean cloud amount over the Yangtze River Delta （YRD）, China were examined for the period 1982-2006 by using a linear regression analysis. Both total and high-level cloud amounts peak in June and reach minimum in December, mid-level clouds have a peak during winter months and reach a minimum in summer, and low-level clouds vary weakly throughout the year with a weak maximum from August to October. For the annual mean cloud amount, a slightly decreasing tendency （-0.6% sky cover per decade） of total cloud amount is observed during the studying period, which is mainly due to the reduction of annual mean high-level cloud amount （-2.2% sky cover per decade）. Mid-level clouds occur least （approximately 15% sky cover） and remain invariant, while the low-level cloud amount shows a signifi cant increase during spring （1.5% sky cover per decade） and summer （3.0%sky cover per decade）. Further analysis has revealed that the increased low-level clouds during the summer season are mainly impacted by the local environment. For example, compared to the low-level cloud amounts over the adjacent rural areas （e.g., cropland, large water body, and mountain areas covered by forest）, those over and around urban agglomerations rise more dramatically.
