# Presentation: 080695

## 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

**Notes:**
I am a grad student at the University of Maryland; Hugo Berbery is my advisor at Maryland
... during the NAME 2004 field campaign

## 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

**Notes:**
we will compare model simulations to observations in the hopes of studying potential forcings of the diurnal cycle.  As well, we will be looking into the effects of gulf surges

## Outline

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

## The North American Monsoon

- Bordoni et al., 2004

## NAME

**Notes:**
tier 1: warm-season convective processes
tier 2: intraseasonal variation
tier 3: boundary forcing

## 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

**Notes:**
NCEP workstation Eta model
run at the University of Maryland

## Eta Model domain

**Notes:**
just a bit larger than NAME tier 2

## 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

**Notes:**
3 hourly observations

## I. The diurnal cycleof precipitation in the core North American Monsoon region

- 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**

**Notes:**
20N to 40N and 120W to 100W
precip highest 24-26N
Eta higher than CMORPH: max about 10, CMORPH max about 6
Eta may have more detail due to higher resolution
most spatial features represented by Eta; e.g. core region and northeast New Mexico

## CMORPH

**CMORPH**

**ETA **_**diurnal cycle**_

**Notes:**
Structure & evolution of the diurnal cycle in the core NAM region
every 2 degrees latitude between 22N and 30N
y-axis is 24hours, from midnight to midnight
x-axis is 112W to 102W: core region
surface elevation is shown beneath each diagram
Eta peaks at about 1 mm/3hr higher than CMORPH, and between 24-26N; CMORPH peaks 26-28N
precip begins around 1200-1500 in east (mountains), peaks downslope at 1800-2100, peters out in small hours of the morning near coast
can see this cycle in Eta as well, although Eta tends to show more precipitation in the morning
visual inference of slope of blobs to get estimate of speed of propagation

## westward propagation

**speed (m/s)**

**6**

**4**

**2**

**0**

**latitude**

**20**

**25**

**30**

**Notes:**
possibly separates into N of 25 and S of 25?

## CAPE/CIN

- MFC

**Notes:**
Potential forcings of the diurnal cycle:
convective available potential energy
convective inhibition
regions of high CAPE and minimum CIN occur just prior to the heaviest precipitation; highest CAPE occurs in southern Gulf, south of highest precipitation

vertically integrated moisture flux convergence
due to the noisy structure of the fields, moisture flux convergence has been smoothed by two applications of a 9-point smoothing function to highlight the more relevant features
highest MFC precedes most intense precip by ~3hrs, mid-afternoon strong mfc over western slopes of SMO and strong moisture flux divergence over Gulf of California; while MFC matches up with latitude of most intense precip, westward propagation signal does not appear, except perhaps in the south...?

## II. Advective processes in the Gulf of California—moisture surges

**NASA: earthobservatory.nasa.gov**

## Moisture Surges

*NCEP Eta model analyses*

**Notes:**
low-level, northerly surge of moist tropical air through the Gulf of California
usually related to passage of easterly wave; tropical storms can trigger strong surges

## 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

**Notes:**
low-level, northerly surge of moist tropical air through the Gulf of California
usually related to passage of easterly wave; tropical storms can trigger strong surges

## Surges and precipitation

**    ****CMORPH     ****CMORPH surge      ****ETA     ****ETA surge**

**Notes:**
these are not the same scale!
surges generally coincide with high precipitation
point out TS Blas

## Surge effects in SW U.S.

**Surge effects in SW U.S.**

**40****°N**

**25****°N**

**-120**

**-100**

**ETA**

**CMORPH**

- Percent of total precip coincident with surge

**Notes:**
if you ignore the non-monsoon regions, reasonably ok match, espec. in SW Arizona where precip has previously been observed to be strongly related to surges
- core region doesn’t show big effect: this is in line with previous studies that have found that the core region precip is less affected by surge

## ETA				CMORPH

**ETA****	****	****	****	****CMORPH**

**surge**

**surge**

**no surge**

**no surge**

**Notes:**
eta and cmorph have some agreement in magnitude and time for non-surge conditions, although Eta is further East than CMORPH

Eta seems to have some problems when simulating 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

**Notes:**
Eta model shows lesser westward propagation:  difficult to know to what extent CAPE/CIN and MFC simulations are accurate

## 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.