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The North American Drought Atlas as a Template for Developing an Old World Drought Atlas

The North American Drought Atlas as a Template for Developing an Old World Drought Atlas. Edward R. Cook Tree-Ring Laboratory Lamont-Doherty Earth Observatory Palisades, New York Presented at: Bert Bolin Centre for Climate Research Stockholm University September 7, 2009. Or if you wish,

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The North American Drought Atlas as a Template for Developing an Old World Drought Atlas

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  1. The North American Drought Atlas as a Template for Developing an Old World Drought Atlas Edward R. Cook Tree-Ring Laboratory Lamont-Doherty Earth Observatory Palisades, New York Presented at: Bert Bolin Centre for Climate Research Stockholm University September 7, 2009

  2. Or if you wish, Towards Near-Global Reconstruction and Understanding of Hydroclimate Variability and Change Over the Past Several Centuries

  3. The Goal • Develop a gridded ‘Old World Drought Atlas’ (OWDA) using the North American Drought Atlas (NADA) as a template for exact compatibility and comparability. • The OWDA will complement the NADA and Monsoon Asia Drought Atlas (MADA). • This will provide coverage across much of the Northern Hemisphere to provide the needed spatio-temporal paleo-drought data sets for modeling the causes of drought on interannual to centennial time scales. • OWDA will be an important step ‘Towards the Near-Global Reconstruction and Understanding of Hydroclimate Variability and Change Over the Past Several Centuries’- a project funded by NOAA with Richard Seager and Yochanan Kushnir at Lamont.

  4. Here is what I am talking about. Existing and Proposed Drought Atlases But why do we need them?

  5. For the NH Subtropics, the future might be much drier: precipitation, soil moisture, and runoff all decrease significantly while evaporation increases over northern Europe. The Need: Understanding the Causes of Hydroclimatic Variability and Change IPCC AR4 A1B Scenario Changes: 2080 to 2099 from 1980 to 1999

  6. P-EPE Average PDSI Over North America 1999-2006 Have we started? For the American Southwest and Mexico, the projected drying may have already begun.

  7. Wetter North Drier South Wetter North Drier South Over Europe, North Africa, and the Middle East (the ‘Old World’ here), the projections for the future are not much better, especially in the Mediterranean region. IPCC AR4 A1B Scenario Changes: 2080 to 2099 from 1980 to 1999

  8. Understanding Drought in the ‘Old World’: the Present Drying trend

  9. Understanding Drought in the ‘Old World’: the Present 1950-2002 So has the projected drying trend in the South begun? Large-scale drying

  10. Understanding Drought in the ‘Old World’: the Past Medieval megadroughts in northern Europe and Morocco. Why? Same or different causes as in North America? Understanding past drought and its causes does matter.

  11. The ‘OWDA’ Target Drought Index Field Self-Calibrating PDSI (scPDSI) based on CRU TS 3.1 monthly temperature and precipitation data (0.5x0.5 degree resolution). Kindly supplied by Gerard van der Schrier from KNMI.

  12. The ‘OWDA’ Target Drought Index Field

  13. The OWDA Tree-Ring Network (Somewhat Dated) All series begin on or before 1700 and end on or after 1979. A great deal of work is needed here to enlarge the network and completely restandardize it using ‘signal-free’ methods. A chance to get back to Medieval times, but more long tree-ring records are needed.

  14. Method of Reconstruction for the OWDA • Point-by-Point Regression (PPR; Cook et al., 1999). Same as used for producing NADA and MADA. • Doing so guarantees that the three drought atlases are compatible for comparison and modeling purposes. • Each predictand or grid point record is reconstructed separately. • Each grid point regression model can be assessed on its own merits - changing a grid point model does not affect estimates elsewhere in the grid. • Runtime per grid point is very fast - runtime scales linearly allowing very large problems to be done, so an ensemble of runs can be made relatively easily.

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