1. Annual cycle of cloud fraction and surface radiative cloud forcing in the South-East Pacific Stratocumulus region
Virendra P. Ghate and Bruce A. Albrecht (U Miami)
Christopher W. Fairall (NOAA ESRL)
Robert A. Weller (Woods Hole Oceanographic Institution)

2. Significant Component of Earth’s radiation budget.
20% increase can offset global warming due to doubling of CO2.
Strong feedback with ENSO
Klein & Hartmann 1993

3. WORS
Wood’s Hole Oceanographic Institute (WHOI)’s Ocean Reference Station (WORS).
Location: 20° S 85° W
Continuous observations of surface broadband radiative fluxes and thermodynamic variables since October 2000.

4. Cruise Name
Cruise Period
EPIC 2001
Oct 9-25
PACS 2003
Nov 11-24
Stratus 2004
Dec 5-23
Stratus 2005
Oct 5-20
Stratus 2006
Oct 9-27

5. Seasonal variation of meteorology at WORS

6. Seasonal Variations: Other Properties
Surface fluxes of sensible and latent heat, LCL, convective velocity scale, and temperature and moisture advection

7. Estimating Low Cloud Fraction fro a Buoy
LW = Measured downwelling longwave radiation at the surface.
CF = Cloud Fraction
LWcld = Cloud emitted longwave radiation
LWclr = Clear sky longwave radiation.

8. Technique LW = Observed at WORS LWcld = σTLCL4
LWclr = f(qsfc,Tsfc,IVsfc); Fairall et al. 2007

9. Technique Evaluation: Ceilometer Observations

10. Model-satellite comparison

11. Seasonal Cycle: Monthly Means
Cloud Fraction
Annual cycle
Cloud Forcing: Surface radiative fluxes
Annual Cycle:
Solar -125 to -65 W/m2
IR to 35 W/m2

12. Diurnal Cycle

13. Diurnal Cycle Cloud Fraction
Months
Range
Phase
Mean Night-time
DJF
0.33 18
0.68
MAM
0.22 19
0.59
JJA
0.11
0.64
SON
0.23 17
0.79

14. More Detailed Data Sets
Annual Cruises
VOCALS field
Program
Fall 2008