1. Observations of Air-sea Interaction in the Northeast Tropical Atlantic C.W. Fairall, L. Bariteau, S. Pezoa, D. Wolfe NOAA/ Earth System Research Laboratory, Physical Science Division & CIRES 2 nd International AMMA, Karlsruhe, November 2007

2. Objectives of ESRL Studies Local air-sea interaction in the Tropical Atlantic cold tongue and ITCZ. Surface flux parameterizations - deep convection. Variability. Convective clouds and aerosols in cloud radiative forcing. Enhance value of buoy observations: intercalibration, atmospheric profiles, cloud properties, and spatial context. Operational NWP and satellite fluxes

3. Climate Context: Climate Context: IPCC 4 th Assessment Models Climate sensitivity to doubling CO2 Strong correlation of sensitivity with Cloud Radiative Forcing (E. M. Volodin) Low sensitivity ΔCF ~0; High sensitivity ΔCF ~2.7 W/m 2 Decrease in Tropics, increase in midlatitude PBL clouds High sensitivity models tend to overestimate heat into the ocean (E. Tredger). Problems with Tropical seasonal cycle (S. Gualdi) Double ITCZ, cold tongues, Atlantic upwelling

4. The simplest index of cloud effects on the surface energy budget: Focus on the Clouds Cloud forcing is the difference in the observed mean radiative flux versus what the flux would be in the absence of clouds (clear sky model) A related variable that is often used is the maximum cloud forcing, which is the conditional change in the flux when a cloud is actually present: Uses simple measurements that can be made accurately R=radiative flux; subscript x=s, solar or l, longwave 0 implies flux in the absence of clouds (model computation) f is the cloud fraction

5. Objectives: - to collect a suite of oceanographic and meteorological observations in the northeast Tropical Atlantic - to deploy two new moorings as a northeast extension of the PIRATA array (23°W at 4°N and 11.5°N) - to service an existing mooring at 0º, 23ºW Cruise track: 2006 Two Legs: - San Juan to Recife (May 27- June 18) -Recife to Charleston (June 22- July 16)

6. Cruise track of RB-07-03 (black line) and locations of Tropical Atlantic data buoy moorings. Symbols indicate the PIRATA backbone (red squares), the WHOI NTAS buoy (magenta triangle) and the NOAA/NDBC Hurricane buoys (blue diamonds). The PIRATA Northeast Extension is indicated by blue stars. Cruise track: 2007

7. Flux Instrumentation and measurements

8. Instrumentation and measurements: Cloud, Aerosol, PBL

9. Sample Flux Time Series 2006

10. Solar Clear Sky Model: Tuning the Aerosol Optical Thickness

11. Surface Radiative Flux Forcing for AMMA-2006

12. Radiosondes Warmpool Trades ITCZ Cold Brazil ---Brazil Cold ITCZ Trades Gulfstream

13. Microwave Radiometer: Column Water Vapor Warmpool Trades ITCZ Cold Brazil ---Brazil Cold ITCZ Trades GulfstreamWarmpool Trades ITCZ Cold Brazil ---Brazil Cold ITCZ Trades Gulfstream Warmpool Trades ITCZ Cold Brazil ---Brazil Cold ITCZ Trades Gulfstream

14. Ceilometer

15. Linking IR and Solar CF: The CF Phase Diagram Indian Ocean Monsoon Winter Storm Track N. Atlantic Ocean Equatorial EPacEquatorial EAtlan

16. Cruise Summary AMMA06 Still a lot of data processing/reprocessing Intercomparisons (HU, Buoys) X-band ‘Cloud’ Radar (U Miami) Aerosols look interesting – lots of signal in solar flux AMMA07 – In progress C-band Radar!! No Cloud Radar PNE/AMMA08 - Plan full suite of systems

17. Contacts and Data access Chris.Fairall@noaa.gov Ludovic.Bariteau@noaa.gov Daniel.Wolfe@noaa.gov Initial data and preliminary processing available on: ftp://ftp.etl.noaa.gov/et6/archive/AMMA/RHB/