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

2. 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

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

4. The North American Monsoon Bordoni et al., 2004

5. NAME

6. 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

7. Eta Model domain

8. 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

9. I. The diurnal cycleof precipitation in the core North American Monsoon region crh.noaa.gov

10. July-August average daily precip CMORPH ETA 40°N 30°N 20°N

11. 30°N 28°N 26°N 24°N 22°N CMORPH ETA diurnal cycle

12. westward propagation 6 4 speed (m/s) 2 0 20 25 30 latitude

13. 30°N 28°N 26°N 24°N 22°N CAPE/CIN MFC

14. II. Advective processes in the Gulf of California—moisture surges NASA: earthobservatory.nasa.gov

15. Moisture Surges NCEP Eta model analyses

16. 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

17. Surges and precipitation CMORPH CMORPH surge ETA ETA surge

18. Surge effects in SW U.S. ETA CMORPH 40°N 25°N -120 -100 Percent of total precip coincident with surge

19. 30°N 28°N 26°N 24°N 22°N ETA CMORPH no surge surge no surge surge

20. 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

21. 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

22. 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.