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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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Presentation Transcript
slide1

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

slide2

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
slide3

Mississippi

Basin

North

American

Monsoon

South American

Monsoon

La Plata Basin

Summer Monsoons

LLJs

MCCs

Impact on large basins

LS-A feedbacks

slide4

Great Plains

Gulf of California

Berbery and Fox-Rabinovitz (2003)

slide5

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)

slide6

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)

slide7

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

slide9

Unlike the Great Plains LLJ, the South American LLJ is present

throughout the year

Berbery and Barros, 2002: JHM

slide11

Annual cycle of precipitation (mm/day) as a function of the latitude.

From Berbery and Barros 2002, JHM.

the eta model
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
slide13

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.

slide16

Active monsoon

Monsoon break

-

slide17

The structure of the

summer LLJ estimated

from the Eta at two

resolutions:

80 km and 22 km

slide18

Composites based on: P > Pm +1.5 Psd

Moisture flux at 925 hPA

V. Silva

slide24

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

slide26

Austral Summer

Latent heat

Sensible heat

Soil Moisture

vs

Surface variables

Precipitation

Bowen Ratio

Each dot represents

a 15-day average

slide27

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

slide29

Eta model simulations - October 1983

IC: SM(%) -45, -30, -15, 15, 30, 45

E. Collini

slide30

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.
slide31

The Eta model (2)

Alternative settings:

Large domain for

seasonal simulations

Higher resolution

domain for studies of hydrologic impacts

slide32

VIC

Hydrologic Model

Input:Runoff + baseflow

at each grid cell

Output:River discharge at

the basin’s exit point

slide33

La Plata basin and the river routing model

River routing model resolution: 1/8 degrees

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