@InProceedings{Adedoyin:2006:PaMeCo,
author = "Adedoyin, Akintayo",
affiliation = "Physics Department, University of Botswana, P.O. Box 70121,
Gaborone, Botswana",
title = "On the parameterisation of mesoscale convective systems in
regional climate models over Southern Africa",
booktitle = "Proceedings...",
year = "2006",
editor = "Vera, Carolina and Nobre, Carlos",
pages = "691--692",
organization = "International Conference on Southern Hemisphere Meteorology and
Oceanography, 8. (ICSHMO).",
publisher = "American Meteorological Society (AMS)",
address = "45 Beacon Hill Road, Boston, MA, USA",
keywords = "Mesoscale Convectyive Systems, Climate Models, Classification of
Precipitation.",
abstract = "Mesoscale Convective Systems (MCS) are organized groups of
thunderstorms that range in horizontal dimension from 5-500 km and
typically possess lifetimes of 6-24 hours. Vertical motions within
MCSs could be as significant as horizontal motions. These
updraughts and downdraughts impact heavily on local rainfall,
wind, lightning and other forms of severe weather. However, their
limited lateral extent and timescale do not often make them
evident on synoptic charts. These also keep them at sub-grid
levels in most climate models. It seems therefore that a realistic
understanding of MCSs lies in the correct formulation of the
physics and dynamics associated with them. This is more so in
tropical Africa where more than seventy per cent of precipitation
is associated with MCSs. These dynamics are examined with a
linearised inviscid form of the hydrodynamical equations, solved
in shear with the aid of a two-layer model of the atmosphere,
which is consistent with the synoptic situation over tropical
Africa. Results over tropical Africa confirm the existence, among
others, of: a westward-propagating perturbation of wavelength 100
km, phase speed of 7.7 m s-1, period of 3.6 and an amplification
of 1.8 per hour (which has been shown by Adedoyin(1989) to trigger
the dominant MCS in tropical Africa namely, line squalls) and a
wave-like disturbance which has a phase speed of 6.0 ms-1 in the
East-West direction, a wavelength of 2000 km, a period of 3.49
days and growth rate of 3.6 per hour at 500 hPa, which axis
Mphale(1999) has shown to be influenced by the Indian Ocean sea
surface temperature (a study of the ECMWF analyses of vertical
velocity at 400 hPa during a period of convective activities over
Botswana, Southern Africa, (15-21 February 1995) confirmed the
existence of this wave pattern. These perturbations have direct
bearing on tropical Africa MCSs, and the development of mesoscale
models based on them, as done by Abiodun(2003), is envisaged to
improve current parameterisation schemes in regional climate
models. Classification of precipitation as either stratiform or
convective in climate models is examined against the backdrop of
the model. In the case of convective classification, the model is
shown to be useful in informing the choice of its representation
in any of the following approaches: traditional, explicit or
hybrid.",
conference-location = "Foz do Igua{\c{c}}u",
conference-year = "24-28 Apr. 2006",
language = "en",
organisation = "American Meteorological Society (AMS)",
ibi = "cptec.inpe.br/adm_conf/2005/08.31.16.35",
url = "http://urlib.net/ibi/cptec.inpe.br/adm_conf/2005/08.31.16.35",
targetfile = "691-692.pdf",
type = "Hydrological variability and modeling",
urlaccessdate = "27 abr. 2024"
}