Identification

Title

Anthropogenic aerosols dominate forced multidecadal Sahel precipitation change through distinct atmospheric and oceanic drivers

Abstract

Sahel precipitation has undergone substantial multidecadal time scale changes during the twentieth century that have had severe impacts on the region's population. Using initial-condition large ensembles (LE) of coupled general circulation model (GCM) simulations from two institutions, forced multidecadal variability is found in which Sahel precipitation declines from the 1950s to 1970s and then recovers from the 1970s to 2000s. This forced variability has similar timing to, but considerably smaller magnitude than, observed Sahel precipitation variability. Isolating the response using single forcing simulations within the LEs reveals that anthropogenic aerosols (AA) are the primary driver of this forced variability. The roles of the direct-atmospheric and the ocean-mediated atmospheric responses to AA forcing are determined with the atmosphere-land GCM (AGCM) components of the LE coupled GCMs. The direct-atmospheric response arises from changes to aerosol and precursor emissions with unchanged oceanic boundary conditions while the ocean-mediated response arises from changes to AA-forced sea surface temperatures and sea ice concentrations diagnosed from the AA forced LE. In the AGCMs studied here, the direct-atmospheric response dominates the AA-forced 1970s 2 1950s Sahel drying. On the other hand, the 2000s 2 1970s wetting is mainly driven by the ocean-mediated effect, with some direct atmospheric contribution. Although the responses show differences, there is qualitative agreement between the AGCMs regarding the roles of the direct-atmospheric and ocean-mediated responses. Since these effects often compete and show nonlinearity, the model dependence of these effects and their role in the net aerosol-forced response of Sahel precipitation need to be carefully accounted for in future model analysis.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d74f1v3x

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

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

2020-10-01T00:00:00Z

Frequency of update

Quality and validity

Lineage

Conformity

Data format

name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

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