Transcript 2002-2003 VEPIC scientific progress talk from VPM6 (ppt)

VEPIC Update
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
Galapagos I.
P
I
C
Lima
WHOI buoy
San Felix I.
Arica
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
[cm s-1]
ECMWF VERTICAL VELOCITY
Daytime subsidence max
EPIC2001-Sc
Diurnal Cycle
(20S, 85 W)
10
[dBZ]
0
-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
Garreaud
18LT
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
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.