Recent FEWS NET research
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Transcript of Recent FEWS NET research
Recent FEWS NET research
i) Cropped Area
ii) Improved Rainfall Estimates
iii) Climate Change Analyses
TM to Hi-Res Comparison
High Resolution imagery used to classify dots spaced at 500m intervals, and represent “truth”
Field photos provided by USDA give a ground-view of landscape
TM with classification
Quickbird with classification
Mathematical Comparison
• TM tends to systematically overestimate cropped area
• Assessing the relationship between TM cropped area and ‘true’ cropped area reveals an approximately linear relationship
• R^2 = 0.62• For our tested locations cropped area is
20.1% +/- 1.9%
HRTM 46.0%
Improved RFE Estimates (IRE)
ARC MeansSlopeElevationClimate Normals
regressionEnhanced MonthlyMean Fields RFE %s
Multiplication
Unbiased Rainfall Estimates
IDW
Station Data
Improved Rainfall Estimates(IRE)
Mean Fields Comparison
• R=0.8 at 0.1°• Bias=0.01 mm
Much better mean fields than the CHARM
N=73 n=19
Driven by GPCP
MAM
Western Kenya Temporal Error Validation
Driven by GPCP
Regional Metrics At-pixel metrics
Spatial R2
MBE MAE MAESTD-1
TimeR2
MAE MAESTD-1
TimeR2
Seasonal 0.67 0.01 8 0.31 0.87 26 0.52 0.54
Monthly 0.64 0.00 14 0.37 0.75 39 0.54 0.49
Monthly March, Apriland May Observations
SPI Regression Maps
• Compare 1979-2005 IRE SPI values
• 2 predictors– Southwest
Indian Ocean Precip
– Indian Ocean Dipole
850 MAM winds
Concerning TrendsDry Tanzania/Kenya/Ethiopian MAM SPI
-2.5
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
3
Year
SP
I