GLOBAL CLOUD COVER AND CLOUD-WATER PATH FROM ISCCP C2 DATA

The International Satellite Cloud Climatology Project (ISCCP) C2 data from 1984 to 1987 are used to form average extreme season zonal means and global climatologies of cloud parameters. The total cloud amount, in general, agrees well with previous cloud climatologies. The level of agreement between the zonal total cloud climatology of Warren et al. and the ISCCP C2 data is extremely good. The main features of the general circulation of the atmosphere are observed in the global climatology, notably the equatorial maximum associated with the Inter Tropical Convergence Zone, the subtropical minima, and mid-latitude maxima. The polar regions are areas of large-disagreement with previous cloud climatologies. For both poles the ISCCP C2 data show that maximum cloudiness occurs in the winter, whereas most previous cloud climatologies indicate that maximum cloudiness occurs in summer. The ISCCP data indicate that Antarctica is an area of relatively small cloud amounts, which concurs with most previous climatologies. However, the amount and season of minimum cloudiness is in disagreement. Results from the amount of cloud types also show features that can be related to the general circulation of the atmosphere. Low clouds are found to be the most common cloud type over the ocean. Large amounts of low cloud are found on the west coasts of subtropical continents, consistent with the presence of marine stratocumulus. The subtropical high pressure zones are areas with small amounts of middle and high cloud types. The Indian south-west monsoon is easily visible by an increase in the amount of high cloud in the region during Northern Hemisphere summer. The total water-path results highlight the difficulties of cloud retrieval over permanent snow or ice cover. At present the water path results are unreliable.