83rd Annual

Monday, 10 February 2003
Cloudiness characteristics over Northern Hemisphere: An analysis based on ISCCP D2 cloud data set
Valery N. Khokhlov, Odessa State Environmental University, Odessa, Ukraine
Poster PDF (746.2 kB)
ISCCP D2 data are collected from the suite of weather satellites operated by several nations and processed by several groups in government agencies, laboratories, and universities. In this work the cloud fraction data, which are small part only of whole archive, are used for period January 1989 December 1993.

The zonal mean total cloud fraction for whole year has two almost equivalent maximums over Northern Hemisphere. The first is associated with intertropical convergence zone (6 N, 72%) and the second is connected to location of polar front (55 N, 76%). At that in tropics this large value consists of almost equal low (23%), mid (21%) and high (24%) cloud fractions, but in middle latitudes the mid cloud fraction makes largest contribution (32%). In Arctic mid clouds are observed mainly. Tropical cloud maximum consists mainly of liquid cumulus (10%), stratocumulus (8%), altocumulus (8%) and altostratus (7%), ice cirrus (21%) and cirrostratus (10%). Frontal cloud maximum consists mainly of liquid cumulus (8%) and stratocumulus (10%), ice altocumulus (12%), altostratus (10%), cirrus (12%) and cirrostratus (7%). Cirrus, liquid cumulus and stratocumulus, ice altocumulus have maximal hemispherical mean values (11.0, 8.4, 8.1 and 5.2 % correspondingly). Also only liquid stratocumulus and altostratus, cirrus, cirrostratus and deep convective cloud have maximums connected with ITCZ and tropical front. In high latitudes the ice altostratus and nimbostratus have maximums, i.e. arctic front consists mainly of frozen clouds.

Largest values of total cloud fraction are observed in summer both in equatorial zone and in middle latitudes and these are low and high clouds mainly. In Arctic maximum of mid clouds is registered in cold season. During this season the liquid cumulus and altocumulus have a maximum in tropics but ice cumulus and altocumulus in middle and high latitudes. Stratus and nimbostratus are observed in non-tropical latitudes only. At that liquid form is registered in warm season and ice form in cold one.

Thus, using information about cloudiness from meteorological satellites can reveal detailed climatic characteristics, which is not accessible from land observation.

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