A JUNE MONSOON?

David L. Mitchell1, Dorothea Ivanova1 and David Gochis2

1. Desert Research Institute, Reno, Nevada2. National Center for Atmospheric Research, Boulder, Colorado

Acknowledgment: We thank the people at NOAA/NESDIS, CIMSS at Univ. Madison, Wisc., the Navel Research Laboratory in Monterey and UNiSYS for hosting their products on the internet regarding satellite SSTs, total precipitable water, rainfall amounts and wind fields.

AZNM region cumulative normalized rainfallfor periods having N. GC SSTs ≤ indicatedSST. Time is implicit with increasing SSTs.

Mean rainfall rates for the AZNM regionfor N. GC SST intervals of 0.5oC based onfive June-August seasons.

7 July 2002at 00 UTC,Total Precip.Water (TPW)

9 July 2002at 00 UTC,TPW

11 July 2002at 00 UTC,TPW

2.4oC increase in N. GC SST over 2 days,reaching 29.8oC.

11 July 2002at 00 UTC.24 hour rainfallaccumulation

15 July 2002at 00 UTC.24 hour rainfallaccumulation

2002 AZ MonsoonOnset Period

Hypothesis Development: MM5 Modeling of the 1999 Arizona Monsoon Onset

SST Evolution along the NW coast of Mexico

SST Dependence of Vertical Mixing Over the Northern Gulf

Northern gulf SST: 26 oCSST below N. GC: 28 oC

Northern gulf SST: 30 oCSST below N. GC: 30 oC

Cross-Section A-B: Potential temperature

5 AM LST, day 3

Cross-Section C-D: Water vapor mixing ratio

Northern gulf SST: 29 oCSST below N. GC: 30 oC

Northern gulf SST: 30 oCSST below N. GC: 30 oC

5 AM LST, day 3

N. GC 26oC; 28oC otherwise N. GC 29oC; 30oC otherwise N. GC. 30oC; 30oC otherwise

Sensitivity of CAPE (Convective Available Potential Energy) to GCsea surface temperatures. Simulation time = 54 h; 11 pm LST.

Yellow ≈ 1300 J/kg (CAPE)Orange ≈ 2100 J/kgRed ≈ 2900 J/kgBrown ≈ 3700 J/kg

5 AMMSTDay 3

5 PMMSTDay 3

26/28 oC 29/30 oC 30/30 oC

Dependence of CIN on GC SST

Conceptual Model of Moisture Advection Dependence on SST

Comparison of modeled and observed normalized rainfall rates for AZNM region , for modeled conditions in conformity with hypothesis

Temperature, Dewpoint, deg. C Temperature, Dewpoint, deg. C

3 km2.5 km

Alt

itu d

e

100 30 0 10 3020 20

Examples of NAME Soundings over the GC; August Cruise

A June Monsoon?

Blended SSMI/TRMM experimental rainfall estimates from NRL, Monterey

NG: 24.2 oC NG: 26.7 oC

16 June 2005 20 June 2005

SST & TPW

Wind fields suggest Gulf of Calif. moisture source

5 pm MST June 20th, 700 mb 5 pm MST June 20th, 850 mb

June monsoon summary

Food for Thought

Annual Time Series of Regionalized Aug Gulf of California SST

R2 = 0.4261

R2 = 0.4799

R2 = 0.31

R2 = 0.2512

25

26

27

28

29

30

31

32

1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002

Year

SS

T (

deg

C)

N-GoC

C-GoC

S-Goc

Pre-Goc

Linear (N-GoC)

Linear (C-GoC)

Linear (S-Goc)

Linear (Pre-Goc)

What will happen next?

SUMMARY

1. MM5 simulations suggest that the marine boundary layer in the Gulf of California (GC) may be sensitive to GC SSTs. This MBL may act as a moisture source for monsoon rainfall over AZ.

2. The moisture source for the June period of scattered thundershowers affecting AZ, the Great Basin and Colorado appears to be the GC. This same pattern is commonduring the monsoon season.

3. Soundings over the GC during NAME are consistent with MM5 soundings.

4. Observations of SST, TPW, winds and rainfall during the “June monsoon” of 2005appear consistent with the hypothesis developed from the MM5 study.

5. Since the GC appears to be warming at a rate of about 1.4 oC over the last 20 years, it is important to understand the role that GC SSTs play in monsoon dynamics.