VEPIC Update Goals and methods Targeted extended time observations Chris Bretherton, University of Washington Goals and methods Targeted extended time observations EPIC/DYCOMS-II developments

VEPIC THEME The theme of VEPIC is to better understand and simulate how Eastern Pacific cloud systems interact with the coupled ocean-atmosphere-land system on diurnal to interannual timescales.

VEPIC Scientific Issues (VPM5) On what time and space scales does continental heating/mechanical forcing impact boundary layer cloud/radiative forcing? How sensitive is the overall tropical circulation and ENSO to variations of Eastern Pacific cloud topped boundary layer properties and why? What are dominant S/I feedbacks among Sc clouds, surface winds, upwelling, coastal currents and SST in E Pacific? Does natural and anthropogenic aerosol variability significantly modulate the Sc?

VEPIC STRATEGIES (VPM5) E Pacific as a testbed for model evaluation and improvement (e.g parameterization development) using multiscale data sets. Model sensitivity studies to refine hypotheses and target observations. Synthesis and enhancement of existing data sets, through targeted instrument procurement, algorithm evaluation and development, and enhanced observation periods. Co-ordination with oceanographic, aerosol, cloud process communities, including CLIVAR CPTs.

V E P I C Galapagos I. Lima Arica WHOI buoy San Felix I.

Two BAMS articles submitted. EPIC2001 work continues Two BAMS articles submitted. AGU special session Possible joint meeting in Sept. with US PanAm CLIVAR (Taneil Uttal)

TAO-EPIC has gathered a nice multiyear dataset Yearly Feb-Apr precip in SE Pacific ‘ITCZ’ …and freshening Cronin

2.5 years of data from the WHOI stratus buoy (20S 85W) Weller

Buoy shows large net heat flux into ocean balancing eddy cooling Weller

Ocean altimetry also shows an energetic eddy field Weller

U. Chile has installed ceilometer and surface met at San Felix Is. Decoupled Cloud base (ceilometer) LCL (surface met) Well-mixed Mostly clear Garreaud Shows daytime rise of LCL, cld. base, with synoptic variations

EPIC2001-Sc Diurnal Cycle (20S, 85 W) Daytime subsidence max [cm s-1] ECMWF VERTICAL VELOCITY Daytime subsidence max EPIC2001-Sc Diurnal Cycle (20S, 85 W) 10 [dBZ] -10 Wood

Diurnal variation of horizontal surface wind divergence from Quikscat Wood seabreeze ? AM subsidence max PM subsidence max Hypothesis: Subsidence wave driven by diurnal heating cycle over Andes reaches buoy at noon.

MM5 simulation also shows late afternoon convergence at coast, midnight ascent at buoy! 06LT 18LT Garreaud

Remotely-sensed cloud microphysics from EPIC2001Sc (Rob Wood, UW)

MODIS visible reflectance, 15Z 20 Oct. 2001 Polynya

Modis effective cloud droplet radius – large (clean) in polynya small in coastal pollution

Polynya – drizzle feedback? DYCOMS-II RF02 Polynya – drizzle feedback? Stevens

DYCOMS-II Sc entrainment estimates from RF01 Stevens

Comparison of 6-day mean 20S 85W profiles with models (Peter Caldwell, UW) All models have adequate Sc, but too shallow a PBL. CAM2 LWC all in lowest 3 levels (70-630 m). Observed LWC mainly at 800-1300 m.

Other updates RICO – trade Cu microphysics/turbulence (Antigua, Dec. 2004-Jan. 2005) www.rico.uiuc.eduww.rico.uiuc.edu Proposed CPT on tropical cloud feedbacks on climate sensitivity…includes several US members of VEPIC.

Conclusions VEPIC-related progress in: Atm.-ocean feedbacks in E Pacific S America and SE Pac diurnal cycle of subsidence, cloud Importance of cloud/drizzle/aerosol coupling to E Pac Sc. Model/reanalysis validation using Existing data synthesis, targeted enhancements (WHOI buoy, SFI), field expts. (EPIC2001/DYCOMS-II.) Coordinated modeling. Come to WG meeting to hear more about VEPIC and participate in planning its future.