Identification

Title

Numerical simulation of episodes of organized convection in tropical northern Africa

Abstract

A large-domain convection-permitting numerical model is used to simulate episodes of deep convection, which are generated during the day over the Ethiopian Highlands and then propagate westward over the eastern and central Sahel region (5°-20°N) of northern Africa. The simulation comprises 12.5 days within the African Monsoon Multidisciplinary Analysis (AMMA) field campaign in 2006. During this period, long-lived precipitation episodes that survived beyond a single diurnal cycle occurred in the lee of the Ethiopian Highlands only every 2-3 days in both the simulation and observations. This contrasts with some other latitudinal corridors in the lee of major topography, such as the central United States, where long-lived heavy precipitation episodes frequently occur on successive nights. The intermittency of long-lived events for the current case occurs despite regular daily triggering of convection along the upstream orography, and is linked to strong lower-tropospheric stabilization and reduction of daytime surface sensible heat flux due to residual cloudiness in the wake of long-lived precipitation events during the previous diurnal cycle. The vertical shear that helps organize deep convection is also weakened in the wake of the long-lived events by temporary disruptions of the midtropospheric African easterly jet. The environments of mesoscale convection are presented for the eastern Sahel, a region where most Sahelian convection originates, but about which little is known at the mesoscale. The study describes the potential for early identification of long-lived convection episodes that are likely to have high impact on the central Sahel and West Africa.

Resource type

document

Resource locator

Unique resource identifier

code

https://n2t.org/ark:/85065/d7jh3mzd

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

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keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2012-09-01T00:00:00Z

Frequency of update

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Conformity

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Use constraints

Copyright 2012 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work.

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact