EPIC 2001 SE Pacific Stratocumulus Cruise
9-24 October 2001Chris Bretherton and Sandra Yuter (U. Wash.)
Chris Fairall, Taneil Uttal (NOAA/ETL)
Bob Weller (WHOI)
Goals
• Document cloud and boundary layer structure in the SE Pacific
• Assess the importance of drizzle processes to cloud thickness and extent
• Compare results with other Sc regimes and with large-scale models
• Maintain WHOI IMET buoy at 20S 85W
NOAA/ETL (surface met., fluxes, mm radar, lidar)
Participants
Participants
UNAM (aerosol concentration and characterization)
Participants
WHOI (CTDs, IMET buoy)
Participants
University of Washington (sondes, 5 cm scanning radar,
meth blue, cloud photos)
EPIC Sc cruise9-24 Oct. 2001
3 hr rawinsonde launches
(Kim Comstock, UW)
cld top
cld base
LCL
Cloud top and dBZ (MMCR), base (ceilometer), LCL (surf. met.)
[m s-1] ECMWF VERTICAL VELOCITY
[dBZ]10
-10
0
DiurnalCycle
Sample of C-band scanning
radar and coincident
MMCR
dBZ
0530 0730
Meth BlueRain Rate
Num
ber/
seco
ndZ=58R1.1
Remotely-sensed cloud microphysics
(Rob Wood, UW)
…UNAM also found a strong diurnal signal in submicron aerosol conc.
MODIS 10/16/2001; 10:00 Local (16:00 UTC)
1 3 10 30 100 300 1000 cm-3
0 50 100 150 200 250 300 g m -2
0 5 10 15 20 25 30 mm
Liquid water path Droplet concentrationEffective radius
SHIP
250 km
Comparison of 6-day mean 20S 85W profiles with models
• All models (esp CAM) have too shallow a PBL.• CAM2 LWC all in lowest 3 levels (70-630 m).• Observed LWC mainly at 800-1300 m.
(Peter Caldwell, UW)
Conclusions• A remarkable dataset was gathered
documenting both spatial and diurnal variability of the SE Pacific Sc regime
• Pronounced diurnal cycle, amplified by subsidence wave from S America.
• Mesoscale drizzle cells ubiquitous, especially at night; rain mostly evaporates above surface, sensitive to cld drop conc.
• Boundary layer deeper than current global models; well-mixed in early evening.