Piotr Wolski. Climatic and hydrological changes in the Okavango Delta. The Okavango. Mohembo. Maun. The Okavango. it is Delta, not delta it is the 5th largest Ramsar site in the world it is the 3rd largest inland “delta” in Africa. The Okavango. Regional tectonic setting
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Climatic and hydrological changes in the Okavango Delta
Regional tectonic setting
(after Kampunzu, 1998)
Frequency of tectonic events
(after McCarthy, 1993)
Interannual and multidecadal variability. Or is it change?
After McCarthy et al.
CRU dataset and observations
Multi-Taper Method (MTM) of spectral analysis
Discharges respond stronger to multidecadal variability in rainfall than in temperature!
Wolski et al. submitted
Pacific Decadal Oscillation ???
20th century rainfall:
21st century rainfall:
Multidecadal variability present, but superimposed on downward trend
Simulations of Okavango River discharges based on ensemble of GCM runs
Stone, Lennard, Tadross, Allen, Stott & Pall (2011)
Okavango discharge at Mohembo
Probability of high floods
decreases in warmer climate
FAR: -0.03 for 2009
-0.19 for 2010
How good is the GCM-hydro model combination in simulating Okavango flows?
Classes of synoptic variables in a 6x4 SOM based on NCEP reanalysis data
Air temperature @ 2 m
Relative Humidity @ 850 mbar
Frequency of synoptic states for each year
Significance of difference in frequency between “good” and “bad” years
There is potential for distinguishing “good” years from “bad” ones based on synoptic conditions
Simulations of Okavango flows based on TRMM rainfall
“Tweaked” MIRA + obs
Particularly significant in the context of seasonal forecasting
Pixel inundation status
as a function of system’s inundation area
Deviation of probability
as a function of time
Temporal trend in deviation of probabilities of inundation status
Causes not fully understood, yet have implications on planning, management, cc adaptation etc.