Impact of Dust Radiative Forcing upon Climate - Mineral Dust: A Key Player in the Earth System - page 335

Table 13.2 Qualitative summary of dust radiative forcing and the response of surface air
temperature in the Sahara and precipitation in the Sahel. All averages are for NH summer (JJA
or JJAS) unless noted. Figures used to describe the forcing and response in the cited article are also
listed along with the identity of the experiment where there is more than one. All models calculate
SST using a mixed-layer ocean model with fixed heat transport unless otherwise noted
Surface air temperature over the Sahara
Study F T F S Cited figure ıT S Cited figure

5a 1

Miller and Tegen ( 1998 ) C - 2a, 1a -

Unpublished 2 Miller et al. ( 2004b ) - - 8 -

6b 3 Yoshioka et al. ( 2007 ) - C 2c C

4b 6

Yu e e t a l . ( 2011 ) C - 2e,f C

13.5 b 8 This study C - 13.1 b C

Precipitation within the West African and Atlantic ITCZ
Study

F T F S Cited figure ıP Cited figure

7a 1 Miller and Tegen ( 1998 ) - - 2a, 1a -

16 2

Miller et al. ( 2004b ) - - 8 -

4b 3 Yoshioka et al. ( 2007 ) - - 2c -/C

2b, 3 4 Solmon et al. ( 2008 ) -/ C - 1a,b -

5f 5

Perlwitz and Miller ( 2010 ) C 2f

Yu e e t a l . ( 2011 ) C - 2e,f C 4h 6

Solmon et al. ( 2012 ) -/ C 7c - 6d 7

This study 13.7 b 8

1 Dust concentration is largest over the Arabian Sea in this model and unrealistically low over the
Sahara. Cooling occurs over most of Sahara, despite F T >0. A weak precipitation anomaly
extends offshore over the Atlantic toward the ITCZ
2 Forcing is listed for the 1:0

C - 13.1 b C

$ 0 experiment whose shortwave absorption is taken from Patterson
et al. ( 1977 ). F T <0and F S <0within the subtropical Atlantic and precipitation is reduced
downwind within the Atlantic ITCZ. Only annual average precipitation is shown: the anomaly
over the West African coast switches sign to positive as the solar absorption is increased by
10 %. Dust cools the Sahara (unpublished), in part due to moistening of the surface air by the
precipitation anomaly
3 Annual forcing from the SOM.SP experiment, JJAS response from the SOM.SP (precipitation)
and SOM.SL (precipitation, temperature) experiments. Complicated precipitation response with
reduction over the West Atlantic and increase along the Guinea coast. Warming over the Sahara,
cooling over the Sahel
4 Regional model, with prescribed SST. Precipitation is reduced within the Sahel, with an increase
over the Atlantic that is an artifact of the prescribed SST according to Solmon et al. ( 2012 )
5 Forcing is from the 1.0

SSA experiment. Dust concentration peaks over the Arabian Sea, with
comparatively low values over the Sahara. The regional distribution of high cloud cover is used
as a proxy for the precipitation anomaly
6 Annual forcing and response. Forcing from Yue et al. ( 2010 ). Response from MXLSST_FD
experiment. Warming over the Sahara, cooling over the Sahel. Precipitation is reduced over the
Atlantic, with a smaller reduction over the western Sahel and coastal region
7 Forcing is from the standard case, but response is for the experiment where SST is reduced
in proportion to dust optical thickness. Precipitation is reduced within the Sahel, with a larger
reduction over the Atlantic when the ocean is cooled in proportion to the dust load
8 JJAS averages of forcing and response. The simulation with solar absorption taken from Patterson
et al. ( 1977 ) is tabulated here, but use of the absorption compiled by Sinyuk et al. ( 2003 ) results
in nearly zero forcing at TOA, a correspondingly weak warming within the Sahara and virtually
no rainfall anomaly within the Sahel