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New Empirical Downscaling for Africa

Explore the innovative approach of New Empirical Downscaling for Africa, addressing community climate needs through advanced modeling techniques. Learn the methodology, applications, and future directions of this cutting-edge technique.

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New Empirical Downscaling for Africa

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  1. South New Empirical Downscaling for Africa ^ Bruce Hewitson & Robert Crane AF 07 Second AIACC Regional Workshop for Africa and Indian Ocean Islands Dakar, Senegal, 24-27 march 2004

  2. Approach Downscaling of present rainfall Model Comparison Future Climates New Empirical Downscaling for Africa Why this approach? Convergent Solutions? Future Directions?

  3. Why Empirical Downscaling? Why this Approach? Little done on sensitivity analysis Little consensus on climate requirements Majority of impacts community requires statistics of daily data within month (not actual daily data) Local-scale climate only partially determined by larger-scale controls Requires a stochastic component to the generation of local climate Therefore: GCM fields used to condition a stochastic generation of local climate

  4. Methodology SOM-based Approach -- extracts non-linear relationships in a multivariate data set. • Produces: • Representations of the range and continuum of atmospheric states. • Map rainfall distributions to those states

  5. % mm x 10 Percent Frequency of daily rainfall events for two contrasting atmospheric states % mm x 10

  6. For a given downscaled target location: We have: ~100 atmospheric states, and the rainfall distribution for each state

  7. To apply the downscaling to the models: We take the GCM fields: Identify corresponding atmospheric states for each day in a month Sample from the associated frequency distributions From that, determine dry or wet state and distribution of daily rainfall for the month

  8. Observed Rainfall 1970-1999 Daily Data NCEP Reanalysis

  9. ECHAM Control NCEP Reanalysis

  10. CSIRO Control NCEP Reanalysis

  11. The downscaling procedure still needs some refinement • Choice of atmospheric parameters • However:

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