1. SST and vegetation in modulating the diurnal cycle forcing of convection during the warm season Michael Douglas, NSSL Co-PI’s: Christopher Watts, Univ. of Sonora Russel Schott, USDA-ARS

2. Seasonal cycle of monthly mean precip expressed as % of annual total (maximum inland in July, over Gulf in September)

11. Schematic evolution of the monsoon convection as function of SST and land temperature from pre-monsoon to late monsoon

12. SST and vegetation in modulating the diurnal cycle forcing of convection during the warm season This study proposes to make observations to quantify the vegetation changes, the atmospheric boundary layer changes, and the diurnal circulation changes that will help to explain the observed migration of precipitation towards the coast as the season progresses. Measuring the seasonal evolution of the diurnal cycle of the sea-land breeze circulation and the surface layer characteristics will require an observational array operating over a 4-month period. The observations will include surface measurements from several automated surface stations and a flux tower, an array of pilot balloon sites, and other measurements of vegetation, cloudiness, and atmospheric humidity and temperature profiles.

13. Key science issues being addressed: Hypothesis: changes in precipitation climatology around the Gulf of California during the warm season are mainly associated with land-sea temperature contrasts that modulate the atmospheric convection. We expect to show that the onset of the rains over the TDF cools inland temperatures, which in turn weakens the afternoon slope and sea-breeze circulations. This, coupled with rising SST's in the Gulf of California, moves the region of most favored convection towards the coast, explaining the observed precipitation climatology.

14. Platform description: Pilot balloon soundings at various sites Surface automated station data Some (~100) simple and fewer (~10) digital recording raingauges Instrumented dry-forest tower for measurements of humidity, temp, momentum fluxes plus radiation... Some radiosonde measurements

15. Measurement strategies... Polygonal array of sounding sites to measure divergence throughout summer season Rainfall and vegetation measurements to correlate with changes in diurnal breeze intensity Flux tower measurements to describe the diurnal to seasonal changes in surface fluxes from dry forest as function of vegetation change.

16. Outline of observations Twice-daily pibals from June 1 - Sept 15th for polygon of sites Once-daily radiosonde observations in early PM at one dry forest site (non-windfinding RS-80 sondes) Surface automated weather stations at coastal sites measuring at least at 5 min resolution throughout the summer. Dry forest flux tower operating throughout the summer Simple and digital raingauges in study domain throughout the summer

17. The proposed observational array for this study. Each corner of the polygon is a pilot balloon site, as well as the central site at Huatabampo. Special micro- meteorological measurements would be made near the letter "E". Daily radiosonde observations would be made at either Tezopaco or Choix, the two inland sites.

18. Intensive Observation periods Three 15-day periods proposed... One before onset of rains, one several weeks after onset of rains, and one near end of special observation period During the IOPs: –Pibals 4X daily at each site –Radiosondes at dry forest site 4X daily –Digital cloud photography at selected (but undetermined) sites

19. Data dissemination plan... Most data will be made available to JOSS as soon as it is quality controlled. No reason/desire to hold any data hostage...

20. Field coordination requirements IOP coordination: –How will we participate in coordination? No IOP coordination needed - unless desired by other participants... –Will we need to coordinate with ship/aircraft and other systems? No

21. Expected coordination with data assimilation / modeling groups... Desired but not arranged to date...

22. Near term coordinations needed with: ISS sites to minimize redundant observations SMN radiosonde site to ensure coverage PACS-SONET site (Topolobampo) for coordination of IOP observations Other?