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

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.The diurnal cycle of precipitation in the North American Monsoon II.Moisture surges in the Gulf of California

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 cycle of precipitation in the core North American Monsoon region

July-August average daily precip CMORPHETA 40°N 20°N 30°N

28°N 26°N 24°N 22°N CMORPHETA diurnal cycle

westward propagation speed (m/s) latitude

CAPE/CINMFC 30°N 28°N 26°N 24°N 22°N

II. Advective processes in the Gulf of California— moisture 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 ETACMORPH Percent of total precip coincident with surge

ETACMORPH surge 30°N 28°N 26°N 24°N 22°N 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, 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: /2004GL 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,