Model representation of the diurnal cycle and moist surges along the

1
Model representation of the diurnal cycle and
moist surges along the Gulf of California during
NAME Emily J. Becker and Ernesto Hugo Berbery
Department of Atmospheric and Oceanic
Science University of Maryland, College
Park October 28, 2005
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Motivation

• NAME determining the sources and limits of
  predictability of warm season precipitation over
  North America
• Proper representation of physical mechanisms
  including mesoscale processes the diurnal cycle,
  surges

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Outline

• Introduction
• Model and observation data
• The diurnal cycle of precipitation in the North
  American Monsoon
• Moisture surges in the Gulf of California

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The North American Monsoon
Bordoni et al., 2004
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NAME
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Model Data

• NCEP Eta Model forecasts
• 22km grid spacing 0.25 x 0.25 spatial
  resolution
• 45 vertical levels
• 12-36hr forecasts
• precipitation, winds, moisture
• 3-hourly data used for our study

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Eta Model domain
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Observation Data

• CMORPH
• CPC Morphing Method
• passive microwave satellite scans propagated by
  motion vectors derived from satellite infrared
  data
• high spatial and temporal resolution 0.5 x 0.5
  grid, 3-hourly used for our study

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I. The diurnal cycleof precipitation in the core
North American Monsoon region
crh.noaa.gov
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July-August average daily precip
CMORPH
ETA
40N
30N
20N
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CMORPH
ETA diurnal cycle
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westward propagation
6
4
speed (m/s)
2
0
20
25
30
latitude
13
CAPE/CIN
MFC
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II. Advective processes in the Gulf of
Californiamoisture surges
NASA earthobservatory.nasa.gov
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Moisture Surges
NCEP Eta model analyses
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Moisture Surges

• Low-level, northerly surge of moist tropical air
  through the Gulf of California
• Meridional moisture flux is equal to or greater
  than the mean (0.5standard deviation) at
  northern Gulf of California 30N, 113W

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Surges and precipitation
CMORPH CMORPH surge ETA ETA surge
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Surge effects in SW U.S.
ETA
CMORPH
40N
25N
-120
-100
Percent of total precip coincident with surge
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ETA CMORPH
surge
surge
no surge
no surge
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Summary and future plans

• Diurnal cycle
• Eta model shows greater intensity than CMORPH
  similar spatial representation
• westward propagation of diurnal precipitation in
  core region most prominent in region of 25N-29N
• Eta model shows lesser westward propagation

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Summary and future plans

• Surges
• Eta model shows much higher intensity than CMORPH
  during surges, loses diurnal cycle better match
  for non-surge
• Other data sets
• Rain gauges
• North American Regional Reanalysis
• Tropical Storm Blas case study

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References

• Becker, E.J., and E.H. Berbery Eta model
  representation of the diurnal cycle and moist
  surges along the Gulf of California during the
  2004 NAME field campaign. In development.
• Berbery, E.H., and M.S. Fox-Rabinovitz, 2003
  Multiscale diagnosis of the North American
  Monsoon System using a variable-resolution GCM.
  J. Climate, 16, 1929-1947.
• Bordoni, S., P.E. Ciesielski, R.H. Johnson, B.D.
  McNoldy, and B. Stevens, 2004 The low-level
  circulation of the North American Monsoon as
  revealed by QuikSCAT. Geophys. Res. Lett., 31,
  doi10.1029/2004GL020009.
• Joyce, R.J., J.E. Janowiak, P.A. Arkin, and P.
  Xie, 2004 CMORPH A Method that Produces Global
  Precipitation Estimates from Passive Microwave
  and Infrared Data at High Spatial and Temporal
  Resolution. J. Hydromet., 5, 487-503.