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Title: The precipitation response to the desiccation of Lake Chad

Abstract

Located in the semi-arid African Sahel, Lake Chad has shrunk from a surface area of 25000 km2 in 1960 to about 1350 km2 due to a series of droughts and anthropogenic influences. The disappearance of such a large open-water body can be expected to have a noticeable effect on the meteorology in the surroundings of the lake. The impact could extend even further to the west as westward propagating convective systems pass Lake Chad in the rainfall season. This study examines the sensitivity of the regional hydrology and convective processes to the desiccation of the lake using a regional atmospheric model. Three Lake Chad scenarios are applied reflecting the situation in 1960, the current situation and a potential future scenario in which the lake and the surrounding wetlands have disappeared. The model simulations span the months July-September in 2006, which includes the rainfall season in the Lake Chad area. Total precipitation amounts and the components of the hydrological cycle are found to be hardly affected by the existence of the lake. A filled Lake Chad does, however, increase the precipitation at the east side of the lake. The model results indicate that the boundary layer moisture and temperature are significantlymore » altered downwind of the lake. By investigating a mesoscale convective system (MCS) case, this is found to affect the development and progress of the system. At first, the MCS is intensified by the more unstable boundary layer air but the persistence of the system is altered as the cold pool propagation becomes less effective. The proposed mechanism is able to explain the differences in the rainfall patterns nearby Lake Chad between the scenarios. This highlights the local sensitivity to the desiccation of Lake Chad whereas the large-scale atmospheric processes are not affected.« less

Authors:
; ;
Publication Date:
Research Org.:
BROOKHAVEN NATIONAL LABORATORY (BNL)
Sponsoring Org.:
USDOE SC OFFICE OF SCIENCE (SC)
OSTI Identifier:
1044788
Report Number(s):
BNL-98144-2012-JA
Journal ID: ISSN 0035-9009; QJRMAM; R&D Project: 2014-BNL-EE630EECA-Budg; KP1701000; TRN: US201214%%834
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Quarterly Journal of the Royal Meteorological Society; Journal Volume: 138; Journal Issue: 664
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; AIR; BOUNDARY LAYERS; CHAD; DROUGHTS; HYDROLOGY; LAKES; METEOROLOGY; MOISTURE; PRECIPITATION; SEASONS; SENSITIVITY; SURFACE AREA; WETLANDS

Citation Formats

Lauwaet D., VanWeverberg K., and vanLipzig, N. P. M., Weverberg, K. V., Ridderb, K. D., and Goyens, C. The precipitation response to the desiccation of Lake Chad. United States: N. p., 2012. Web. doi:10.1002/qj.942.
Lauwaet D., VanWeverberg K., & vanLipzig, N. P. M., Weverberg, K. V., Ridderb, K. D., and Goyens, C. The precipitation response to the desiccation of Lake Chad. United States. doi:10.1002/qj.942.
Lauwaet D., VanWeverberg K., and vanLipzig, N. P. M., Weverberg, K. V., Ridderb, K. D., and Goyens, C. Sun . "The precipitation response to the desiccation of Lake Chad". United States. doi:10.1002/qj.942.
@article{osti_1044788,
title = {The precipitation response to the desiccation of Lake Chad},
author = {Lauwaet D. and VanWeverberg K. and vanLipzig, N. P. M., Weverberg, K. V., Ridderb, K. D., and Goyens, C.},
abstractNote = {Located in the semi-arid African Sahel, Lake Chad has shrunk from a surface area of 25000 km2 in 1960 to about 1350 km2 due to a series of droughts and anthropogenic influences. The disappearance of such a large open-water body can be expected to have a noticeable effect on the meteorology in the surroundings of the lake. The impact could extend even further to the west as westward propagating convective systems pass Lake Chad in the rainfall season. This study examines the sensitivity of the regional hydrology and convective processes to the desiccation of the lake using a regional atmospheric model. Three Lake Chad scenarios are applied reflecting the situation in 1960, the current situation and a potential future scenario in which the lake and the surrounding wetlands have disappeared. The model simulations span the months July-September in 2006, which includes the rainfall season in the Lake Chad area. Total precipitation amounts and the components of the hydrological cycle are found to be hardly affected by the existence of the lake. A filled Lake Chad does, however, increase the precipitation at the east side of the lake. The model results indicate that the boundary layer moisture and temperature are significantly altered downwind of the lake. By investigating a mesoscale convective system (MCS) case, this is found to affect the development and progress of the system. At first, the MCS is intensified by the more unstable boundary layer air but the persistence of the system is altered as the cold pool propagation becomes less effective. The proposed mechanism is able to explain the differences in the rainfall patterns nearby Lake Chad between the scenarios. This highlights the local sensitivity to the desiccation of Lake Chad whereas the large-scale atmospheric processes are not affected.},
doi = {10.1002/qj.942},
journal = {Quarterly Journal of the Royal Meteorological Society},
number = 664,
volume = 138,
place = {United States},
year = {Sun Apr 01 00:00:00 EDT 2012},
month = {Sun Apr 01 00:00:00 EDT 2012}
}
  • This paper reports on Mango 1, which is an exploration well started in September 1990 on a block adjacent to Lake Chad by Esso, Chevron and Shell was suspended after the coup in that nation's capital later in the year. The small Sedigi oil field, discovered in the 70s, will be developed with a pipeline to a 3,000-bpd refinery. Improved relations with Libya and future internal stability may further open the door to exploration.
  • This overview of the petroleum geology of rift basins in Niger, Chad, and Central African Republic (CAR) is based on exploration work by Exxon and partners in the years 1969-1991. The work included 50,000 km of modern reflection seismic, 53 exploration wells, 1,000,000 km[sup 2] of aeromagnetic coverage, and about 10,500 km of gravity profiles. The results outline ten Cretaceous and Tertiary rift basins, which constitute a major part of the West and Central African rift system (WCARS). The rift basins derive from a multiphased geologic history dating from the Pan-African (approximately 750-550 Ma) to the Holocene. WCARS in themore » study area is divided into the West African rift subsystem (WAS) and the Central African rift subsystem (WAS) and the Central African rift subsystem (CAS). WAS basins in Niger and Chad are chiefly extensional, and are filled by up to 13,000 m of Lower Cretaceous to Holocene continental and marine clastics. The basins contain five oil (19-43[degrees]API) and two oil and gas accumulations in Upper Cretaceous and Eocene sandstone reservoirs. The hydrocarbons are sourced and sealed by Upper Cretaceous and Eocene marine and lacustrine shales. The most common structural styles and hydrocarbon traps usually are associated with normal fault blocks. CAS rift basins in Chad and CAR are extensional and transtensional, and are filled by up to 7500 m of chiefly Lower Cretaceous continental clastics. The basins contain eight oil (15-39[degrees]API) and one oil and gas discovery in Lower and Upper Cretaceous sandstone reservoirs. The hydrocarbons are sourced by Lower Cretaceous shales and sealed by interbedded lacustrine and flood-plain shales. Structural styles range from simple fault blocks through complex flower structures. The main hydrocarbon traps are in contractional anticlines. Geological conditions favor the discovery of potentially commercial volumes of oil in WCARS basins, of Niger, Chad and CAR. 108 refs., 24 figs., 4 tabs.« less