Paleoclimate Modeling - precipitation over Africa

Modified from Joussaume et al. (1999) GRL 26: 859-862.

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Caption: The change in zonal average annual precipitation (mm/y) between 6kBP and the control, averaged over all land cells between 20W-30E (North Africa), b) latitudinal distribution of biome types (desert, steppe, xerophytic and dry tropical forest/savannah) for all available data points for today and 6kBP over the longitudes 20W-30E, and c) zonal average annual precipitation (mm/y) in the control simulation, averaged over all land cells between 20W-30E, compared to the climatology of Legates and Willmott ( Int. J. Climatol., 111, 1990). In Figure 3a, the two heavy dashed lines indicate the amount of annual mean precipitation that would be required to produce steppic biomes in now desertic regions (footnote 1). This diagram also provides a graphical representation of the shifts of the simulated desert-steppe limit at 6kBP: the limit is shifted from the present day position (15-16N, at the intersection between the dashed curves and the zero line) to the latitude of intersection between the simulated change of annual precipitation and the dashed curves (amount required to shift biomes).

Joussaume, S., et al. Monsoon Changes for 6000 Years ago: Results of 18 Simulations from the Paleoclimate Modelling Intercomparison Project (PMIP). Geophysical Research Letters, 26, 859-862. 1999.