Work in progress: EPIC Enhanced Monitoring
Meghan Cronin (NOAA/PMEL), Nick Bond (NOAA / JISAO), Chris Fairall (NOAA / ETL) and Bob Weller (WHOI)

Next step... Compare the buoy cloud forcing (cfrs vs. cfrl) scatterplots to ISCCP and NWP products.
QUESTIONS:

Where are these other cloud forcing datasets?
Where can I get ISCCP and/or NWP surface cloud forcing data?

I have searched through the IRI/LDEO Data Library: http://iridl.ldeo.columbia.edu/
and have come up with several possible options for the comparison:

Option (1) Cloud forcing based on ISCCP Use NASA ISLSCP GDSLAM Radiation-clouds mth_mean downwelling surface sw and lw computed from ISCCP-C1 (for Jan 1987 - Dec 1988 (l=1:24)). Compute corresponding clearsky sw and lw using Iqbal and Fairall formulae with ECMWF reanalysis data. Compute surface solar cloud forcing (cfrs) as difference between ISCCP sw and ECMWF clearsky. Likewise for cfrl. Bob Weller says he has new ISCCP data direct from Bill Rossow. However, the README file "must be converted with BinHex 4.0". My sense is that it will take a huge effort to sort through this data set. Let's postpone decision to do buoy vs. ISCCP cloud forcing comparison until after the EPIC workshop. Fig. ISLSCP GDSLAM (ISCCP-C1) swr (top) and lwr (bottom) along 95W.

Option (2) NASA ERBE climatological cloud forcing at top of atmosphere. Use top of atmosphere cloud forcing to compare to bottom of atmosphere (i.e. surface) cloud forcing? QUESTION: Does this make sense? Nick Bond says that it doesn't make sense to compare toa cloud forcing to surface cloud forcing, unless we are doing a full radiative balance analysis. Fig. ERBE top of atmosphere solar (top) and longwave (bottom) cloud forcing.

Option (3) ERBE surface solar cloud forcing from the surface radiation budget. As far as I can tell, srb as computed by Li et al. (1993) http://iridl.ldeo.columbia.edu/SOURCES/.ERBE/.dataset_documentation.html is an ERBE cfrs. PROBLEM: This is only solar cloud forcing. Is there an ERBE surface longwave "thermal" ?? cloud forcing ? Let's reevaluate doing an ERBE vs. buoy comparison of cloud forcing after the EPIC workshop. Fig. ERBE global mean cloud forcing srb.

THE WINNER !!

Qsw and Qlw are net solar radiation at surface and net longwave radiation at surface.

To get the comparable cfrs and cfrl,

• the ECMWF net Qsw and Qlw must be converted into downwelling swr and lwr, and then
• compute clearsky swr and lwr, and
• subtract out the clearsky radiation from the downwelling radiation to get surface cloud forcing.

I will need ECMWF data for stratus buoy site.