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Modelling Periods of Significant Saharan Heat Low: How Goes It?

Paper Reviewed
Dixon, R.D., Daloz, A.S. and Vimont, D.J. 2017. Saharan Heat Low Biases in CMIP5 Models. Journal of Climate 30: 2867-2884.

In introducing their study of the subject, Dixon et al. (2017) write that "representing the West African Monsoon (WAM) is a major challenge in climate modeling because of the complex interaction between local and large-scale mechanisms." Consequently, they say that their study "focuses on the representation of a key aspect of West African climate, namely the Saharan Heat Low (SHL), in 22 global climate models from phase 5 of the Coupled Model Inter-comparison Project (CMIP5) multi-model dataset." And what did this effort reveal?

It revealed, as they describe it, that (1, 2) "the models tend to place the SHL farther to the south and farther to the west than the re-analyses do." And they further note, in this regard, that (3) "models that simulate the SHL farther to the north produce more Sahel precipitation," and that (4) "models that place the climatological heat low farther to the north also produce [5] "more mean precipitation across the Sahel, while [6] models that place the heat low farther to the east produce stronger African easterly wave (AEW) activity."

"This research," as they thus go on to describe it, further suggests that sea surface temperatures (SSTs) are (7) "secondary to atmospheric biases for understanding the climatological SHL bias," while further suggesting that (8) "local mechanisms that control the SHL may be connected to climate model biases at a much larger scale," which leads them to ultimately conclude that (9) pertinent hypotheses of theirs and others "should be tested with additional model experiments," which is what they thus go on to do, having outlined the path forward.

Posted 25 July 2017