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THE AMERICAN MONSOONS AND THEIR ROLE IN THE WATER CYCLE

THE AMERICAN MONSOONS AND THEIR ROLE IN THE WATER CYCLE E. Hugo Berbery, Estela Collini, Viviane Silva Department of Meteorology University of Maryland with thanks to Julia Nogu é s-Paegle, Lee Byerle, Brant Liebmann, Rong Fu PACS PI Meeting - Boulder. Outline

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THE AMERICAN MONSOONS AND THEIR ROLE IN THE WATER CYCLE

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  1. THE AMERICAN MONSOONS AND THEIR ROLE IN THE WATER CYCLE E. Hugo Berbery, Estela Collini, Viviane Silva Department of Meteorology University of Maryland with thanks to Julia Nogués-Paegle, Lee Byerle, Brant Liebmann, Rong Fu PACS PI Meeting - Boulder

  2. Outline • 1. The North American monsoon and the low-level jets • 2. The South American monsoon • a. Advective processes • b. Surface processes • Keywords • Low-level Jet • Sources of moisture • Land surface – atmosphere feedbacks • Hydrologic Cycle

  3. Mississippi Basin North American Monsoon South American Monsoon La Plata Basin Summer Monsoons LLJs MCCs Impact on large basins LS-A feedbacks

  4. Great Plains Gulf of California Berbery and Fox-Rabinovitz (2003)

  5. Byerle and Paegle LLJ and Precipitation Responseto Ambient Zonal flow and Orography Deviations from Climatology wet U200 hPa Forcing Response dry LLJ correlation coefficients shown (JJA 1951-2000)

  6. Byerle and Paegle LLJ and Precipitation Responseto Ambient Zonal flow and Orography Deviations from Climatology LLJ wet U200 hPa Forcing dry Response correlation coefficients shown (DJF 1951-2000)

  7. The mechanical blocking of the upstream zonal winds by Andes has a strong control on SALLJ, especially on seasonal and intraseasonal scales: Strong northerly SALLJ Strong westerly upstream westerly wind to the west of Andes Wang and Fu, 2003, J. Climate

  8. Berbery and Barros, 2002: JHM

  9. Unlike the Great Plains LLJ, the South American LLJ is present throughout the year Berbery and Barros, 2002: JHM

  10. Liebmann et al.

  11. Annual cycle of precipitation (mm/day) as a function of the latitude. From Berbery and Barros 2002, JHM.

  12. The Eta model Model Configuration • Horizontal resolution: 80 km and 22 km (tests at 48, 25, 15) • Vertical resolution: 38 lyrs (tests w/ 45 lyrs) • Initial and boundary conditions: AVN; NCEP Reanalyses • Further online information and forecasts:http://www.atmos.umd.edu/~berbery/etasam

  13. While there is an excess of model precipitation over the Monsoon region, the Eta model successfully reproduces the day to day variability. In the southern region, the model reproduces the variability and magnitude of the precipitation.

  14. Active monsoon Monsoon break -

  15. The structure of the summer LLJ estimated from the Eta at two resolutions: 80 km and 22 km

  16. Composites based on: P > Pm +1.5 Psd Moisture flux at 925 hPA V. Silva

  17. Precipitable Water

  18. Theta-e

  19. Precipitation

  20. Runoff

  21. The South American monsoon region Precipitation Runoff

  22. Land surface - atmosphere processes Drier land surface (lower surface latent flux and higher Bowen ratio) during dry and early transition seasons appears to be the cause of strong delay (> 1.5 months) of the wet season onset. 1979: Early onset 1984: late onset 1986: late onset 1990: normal Fu and Li, 2003, J. Theor. & obs. Clim., LBA special issue

  23. Land surface  Precipitation

  24. Austral Summer Latent heat Sensible heat Soil Moisture vs Surface variables Precipitation Bowen Ratio Each dot represents a 15-day average

  25. Schematic of the precipitation-soil moisture feedback Increased Soil Moisture (time scales of 2 weeks or longer) Decreased Sensible Heat Increased Latent Heat Decreased Bowen Ratio (and increased Evaporative Fraction) Increased Precipitation

  26. Eta model simulations - October 1983 IC: SM(%) -45, -30, -15, 15, 30, 45 E. Collini

  27. Summary • The role of advective and local processes was discussed and their impact on precipitation and runoff was assessed. • Two precipitation regimes whose centers form a dipole pattern were discussed; their active/break periods seem to be associated with lateral shifts of the Low-level Jet east of the Andes. • The precipitation-soil moisture interactionsover SAMreveal apositive feedback at time scales larger than ~2 weeks.

  28. The Eta model (2) Alternative settings: Large domain for seasonal simulations Higher resolution domain for studies of hydrologic impacts

  29. VIC Hydrologic Model Input:Runoff + baseflow at each grid cell Output:River discharge at the basin’s exit point

  30. La Plata basin and the river routing model River routing model resolution: 1/8 degrees

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