Average rainfall 2001-2016, global tropics

Map: Average rainfall 2001-2016, global tropics

GRACE water pillar - results

This post presents the graphical results of the analysis of Earth’s water content (equivalent water pillar depth), as estimated from remotely sensed gravitation, for Sub-Saharan Africa. The processing for deriving the images and movies are presented in the previous post.

Monthly GRACE

The movie below is constructed from all the GRACE dates over Sub-Saharan Africa used in this project.

Monthly GRACE variations in equivalent water pillar depth

Note how the water depth varies seasonally, with the Intertropical Convergence Zone (ITCZ) bringing summer rains to southern Africa.

The GRACE equivalent water pillar depth statistics and trends are calculated from annually aggregated data.

GRACE mean and standard deviation

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Equivalent water pillar depth over sub-saharan Africa estimated from GRACE gravitational data for the period 2003 to 2016; the left panel shows average and the right standard deviation. The scaling is different between the two panels.
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Comparison of regression slopes for equivalent water pillar depth over sub-saharan Africa estimated from GRACE gravitational data; clockwise, starting with the upper left panel, the maps show ordinary least square (OLS), median Theil-Sen (TS), upper bound of the 95 % confidence interval of the median TS slope, and the lower left panel the lower bound of the 95 % confidence interval of the median TS slope.
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Estimated absolute changes in GRACE equivalent water pillar depth 2003 to 2016: the left panel shows the change for all regions, the right only changes where the Mann-Kendall test indicates significant changes (p<0.05).

Note how the estimates of the Theil-Sen 95 % confidence level fits well with the map of significant changes as estimated from the Mann-Kendall test. Regions that show a negative (positive) trend at the 95 % upper (lower) confidence interval of the TS are also indicated as areas with significant negative (positive) trend using the MK test.