Atmospheric Chemistry and Physics
www.atmos-chem-phys.net
1680-7316
1680-7324
7
10
2007
10.5194/acp-7-2489-2007
http://www.atmos-chem-phys.net/7/2489/2007/
http://www.atmos-chem-phys.net/7/2489/2007/acp-7-2489-2007.html
http://www.atmos-chem-phys.net/7/2489/2007/acp-7-2489-2007.pdf
2489
2502
2007-05-14
Diurnal variation of upper tropospheric humidity and its relations to convective activities over tropical Africa
E. S. Chung
B. J. Sohn
sohn@snu.ac.kr
J. Schmetz
M. Koenig
School of Earth and Environmental Sciences, Seoul National University, Seoul, Korea
European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), Darmstadt, Germany
Diurnal variations of upper tropospheric humidity (UTH) as well as middle
tropospheric humidity (MTH) were examined in conjunction with the diurnal
cycle of convection over tropical Africa and the adjacent tropical Atlantic
Ocean using Meteosat-8 measurements. Cloud and humidity features were also
tracked to document the diurnal variations of humidity and clouds in the
Lagrangian framework.
<br><br>
A distinct diurnal variation of UTH (and MTH) is noted over regions where
tropical deep convective cloud systems are commonly observed. The amplitude
of the UTH diurnal variation is larger over land, while its variations over
convectively inactive subtropical regions are much smaller. The diurnal
variation of UTH tends to reach a maximum during nighttime over land,
lagging deep convection and high cloud whose maxima occurred in the late
afternoon and evening, respectively. It was revealed that these diurnal
variations over the African continent are likely associated with
continental-scale daytime solar heating and topography, in which
topographically-induced signals develop earlier around the mid-afternoon and
merge into stronger and broader continental-scale convection clusters later,
forming a precipitation maximum in the late afternoon. It was also revealed
that advection effect on the diurnal variation appears to be insignificant.
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