Comparison of Spatial and Temporal Cloud Coverage Derived from CloudSat, CERES, ISCCP and Their Relationship with Precipitation Over Africa

Ntwali Didier

doi:10.11648/j.ajrs.20150302.11

Abstract

The spatial and temporal cloud coverage derived by CloudSat, CERES, ISCCP satellite observations and their relationship with GPCP and TRMM precipitation in West, East and South of Africa were analyzed in this study. CloudSat, CERES and ISCCP show that the high spatial cloud coverage is more frequent in equatorial regions mainly due to more strong convection than other regions. CloudSat shows a low temporal cloud coverage than CERES and ISCCP which are close. Only ISCCP was used to investigate seasonal and temporal variability of different cloud types. The stratocumulus, altostratus, and cirrus clouds are the low, middle and high cloud types with high cloud coverage during JJA, JJA, MAM in West of Africa, during SON, JJA, MAM in East of Africa, and during SON, DJF, DJF in South of Africa respectively . The correlation between cloud coverage and precipitation dataset generally shows a low positive correlation in East of Africa probably due to GPCP and TRMM observations biases whereas a high positive correlation in West and South of Africa. Only middle clouds level in East of Africa, both low and middle in West of Africa show negative correlation with precipitation, whereas all cloud types level in South of Africa show a positive correlation with precipitation.

Highlights

Clouds are one the components which contribute to the Earth's weather and climate
Many researches have been done on cloud variability in Africa, but there are no studies focused on relationship between cloud types and precipitation for temporal and spatial variabilities for specific regions
Many previous studies have been done at global scale which doesn't allow us to know in details cloud and precipitation distribution at small scale. [5] showed that seasonal variation high cloud coverage is related to the movement of the ITCZ. [30] used surface observations data and found that the global average shows a decrease of stratus, altostratus, nimbostratus and high clouds as the major contributor to the decrease of total cover, while there is an increase of stratocumulus, cumulus, cumulonimbus, altostratus

Summary

Introduction

Clouds are one the components which contribute to the Earth's weather and climate. The study of cloud microphysics help to understand the impacts of clouds on the formation of precipitation. Clouds are one of the major factors that influence the general circulation of the atmosphere, the hydrological cycle and the Earth radiation budget [1]. They are the fundamental stage of water cycle processes in the atmosphere, while by condensation of water vapor they form precipitation and the use various instruments as the millimeter-wave CloudSat radar systems help to a broader understanding of the radar reflection properties of various cloud types [2]. [5] explained that for thin high clouds above low clouds, the detection of multiyear clouds is difficult for ISCCP and CERES to accurately retrieve cloud tops because they are based on single layer clouds. High clouds are more distributed over the Intertropical convergence zone which is correlated to deep convective clouds [11]. [12]

18 Ntwali Didier

Data and Methodology

Results and Analysis

Conclusion