Model representation of the diurnal Model representation of the diurnal cycle and moist surges along thecycle and moist surges along theGulf of California during NAMEGulf of California during NAME

Emily J. Becker and Ernesto Hugo BerberyEmily J. Becker and Ernesto Hugo Berbery

Department of Atmospheric and Oceanic ScienceDepartment of Atmospheric and Oceanic ScienceUniversity of Maryland, College ParkUniversity of Maryland, College Park

October 28, 2005October 28, 2005

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

Outline• IntroductionIntroduction

• Model and observation dataModel and observation data

I.I. The diurnal cycle of The diurnal cycle of precipitation in the North precipitation in the North American MonsoonAmerican Monsoon

II.II. Moisture surges in the Gulf of Moisture surges in the Gulf of CaliforniaCalifornia

The North American Monsoon

Bordoni et al., 2004

NAME

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

Eta Model domain

Observation Data

CMORPH– CPC Morphing Method

– passive microwave satellite scans; propagated by motion vectors derived from satellite infrared data

– high spatial and temporal resolution; 0.25° x 0.25° grid, 3-hourly used for our study

crh.noaa.gov

I. The diurnal cycleof precipitation in the core North American Monsoon

region

July-August average daily precip

CMORPH ETA

40°N

20°N

30°N

30°N

28°N

26°N

24°N

22°N

CMORPH ETA diurnal cycle

westward propagation

speed (m/s)

6

4

2

0

latitude20 25 30

CAPE/CIN MFC

30°N

28°N

26°N

24°N

22°N

II. Advective processes in II. Advective processes in the Gulf of California—the Gulf of California—

moisture surgesmoisture surges

NASA: earthobservatory.nasa.gov

Moisture Surges

NCEP Eta model analyses

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 + (0.5*standard deviation) at northern Gulf of California: 30N, 113W

Surges and precipitation

CMORPH CMORPH surge ETA ETA surge

Surge effects in SW U.S.

40°N

25°N

-120 -100

ETA CMORPH

Percent of total precip coincident with surge

ETA CMORPHsurgesurge

30°N

28°N

26°N

24°N

22°N

no surge no surge

Summary and future plans

• Diurnal cycle:– Eta model shows lesser intensity than

CMORPH; similar spatial representation

– westward propagation of diurnal precipitation in core region most prominent in region of 25°N-29N°

– Eta model shows lesser westward propagation

Summary and future plans

• Surges:– Eta model shows 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

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, doi:10.1029/2004GL020009.

• 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.