1. Ocean Surface heat fluxes Lisan Yu and Robert Weller lyu@whoi.edu rweller@whoi.edu http://oaflux.whoi.edu

2. Ocean Surface heat fluxes A brief introduction of the OAFlux project Surface latent and sensible heat fluxes — the state of the latent and sensible heat fluxes in 2005 — its relation to 2004 and to the analysis record that starts from 1981 — the long-term trend in latent heat flux Surface longwave and shortwave radiations (ISCCP) — time series of the global averaged long- and short-wave radiations (1984-2004) — Problems of the ISCCP datasets Comparisons — mean pattern comparison with SOC, NCEP1, and ERA40 — time series comparison with buoy measurements

3. Objectively Analyzed air-sea Fluxes (OAFlux) website: http://oaflux.whoi.edu/ The project is supported by NOAA Office of Climate Observation (OCO) and Climate Change and Data Detection (CCDD). PIs: Yu and Weller, with technical support from X.Jin It is to develop gridded air-sea heat fluxes analysis for the global ice-free oceans for the past 50 years The development is based on a weighted objective analysis that combines surface meteorology from satellite retrievals, COADS ship observations, and model outputs from atmosphere reanalyses. Data currently available online: – Global Q LH and Q SH on daily/monthly and 1º-grid for the years 1981- 2005. – Global Q LW and Q SW (1983-2004) are from ISCCP (Bill Rossow).

4. Input Data Sources Atmospheric reanalyses (NCEP/DOE and ERA40) Air humidity and temperature at 2m, surface wind at 10m, SST, sea level pressure Satellite retrievals: SSMI wind speed and air humidity, AVHRR SST, TMI and AMSR-E SST, scatterometer winds Weighted Objective Analysis: produce optimal estimate for variable fields through combining data from various sources Best estimates of daily flux-related variable fields Daily latent and sensible heat fluxes COARE bulk flux algorithm 3.0 (Fairall et al. 2003) References regarding the methodology and validation: Yu, L., R. A. Weller, and B. Sun, 2004a: Improving latent and sensible heat flux estimates for the Atlantic Ocean (1988-1999) by a synthesis approach. J. Climate, 17, 373-393. Yu, L., R. A. Weller, and B. Sun, 2004b: Mean and variability of the WHOI daily latent and sensible heat fluxes at in situ flux measurement sites in the Atlantic Ocean. J. Climate, 17, 2096-2118. Yu, L., and R. A. Weller, 2006: Objectively Analyzed air-sea heat Fluxes (OAFlux) for the global ice-free oceans: Trend and variability during 1981-2005. Submitted to Bull. Amer. Meteor. Soc. OAFlux: estimating Q LH and Q SH Q LH =  L e c e U (q s – q a ) Q SH =  c p c p U (T s – T a ) Four independent variables U, Ts, q a, and T a.

5. State of ocean heat fluxes in 2005

6. Difference 2005 -2004

7. Changes in oceanic heat fluxes and SST since 1981

8. Linear trends 1981-2005

9. Variance contributions of  q’ and U’

10. ISCCP Surface longwave and shortwave radiations yearly-mean averaged over the global oceans

11. Problems in the ISCCP datasets (1) spatial structure

12. Effect on the EOF analysis The Atlantic Ocean

13. Problems in the ISCCP datasets (2) mean bias: Q LW +Q SW (1984-2002) Positive downward

14. TRITON heat fluxes at (1.5S, 90E) (H. Hase/IORGC) 2-year average (from Jan., 2002 to Dec., 2003) Net heat flux 13.9 Latent heat flux -119.8 Sensible heat flux -8.9 Net short-wave radiation 181.0 Net long-wave radiation -38.4 shortwave net sensible longwave latent (provided by Dr. Yoshifumi Kuroda) OAFlux ISCCP

15. All components No Q LW x No Q LW and Q SW Locations of in situ measurements

16. Stratus buoy (693 days, 10/08/00 to 08/31/02) Fluxes comparison statistic based on daily means ---------------------------------------------------------------------- Q NET Q LH +Q SH Q SW +Q LW ---------------------------------------------------------------------- Buoys 50 -110 160 OAFlux&ISCCP 54 ( +4) -113 ( -3) 168 ( +8) NCEP1 -14 (-64) -144 (-34) 130 (-30) ERA40 47 ( -3) -124 (-14) 171 (+11) ---------------------------------------------------------------------- 30-day running mean applied Statistics based on daily means

17. Pacific Basin: TAO array Q SW Q LW 09/91 – 08/02 04/00 – 08/02 TAO ArrayBOUY 227 -42 ISCCP 238 (+10) -30 (+11) NCEP1 208 (-19) -50 (-8) NCEP2 196 (-31) -38 (+3) ERA40 206 ( -21) -40 (+2) The meridionally averaged mean Q SW (Sep.1991 – Aug.2002) for TAO array, ISCCP, ERA40, NCEP1 and NCEP2 as a function of longitude

18. Atlantic Basin Q SW Q LW Q SW +Q LW PIRATA Array (09/97 – 08/02) BOUY 217 ISCCP 235 (+18) -39 196 NCEP1 212 ( -5) -54 158 NCEP2 193 (-23) -43 150 ERA40 194 ( -22) -45 149 NTAS (03/01 – 08/02) BOUY 242 -53 189 ISCCP 254 (+12) -58 (-5) 196 (+7) NCEP1 217 (-25) -57(-4) 161 (-28) NCEP2 244 (+2) -56 (-3) 188 (-1) ERA40 227 (-15) -51 (+2) 176 (-13) Subduction (06/91 – 06/93) BOUY 200 -63 137 ISCCP 207 ( +7) -58 (+5) 149 (+12) NCEP1 188 (-12) -60 (+3) 128 ( -9) NCEP2 207 ( +7) -59 (+4) 148 (+11) ERA40 201 ( +1) -60 (+3) 141 (+4) CMO (07/96 – 06/97) BOUY 132 -39 93 ISCCP 138 ( +6) -54 (-15) 84 ( -9) NCEP1 147 (+15) -61 (-22) 86 ( -7) NCEP2 167 (+35) -68 (-29) 99 ( +6) ERA40 150 (+18) -60 (-21) 90 ( -3)

19. Summary The OAFlux product 1981-2005: a synthesis of satellite observations and NWP reanalyses outputs of surface meteorology. Surface latent and sensible heat fluxes – There is a long-term trend in latent heat flux. The mean has increased by about 10Wm -2 since 1981, which amounts to almost 12% change. – The increasing trend in latent heat flux is in concert with the warming trend of global SST. Surface longwave and shortwave radiations (ISCCP) — time series of the global averaged long- and short-wave radiations (1984-2004) — Problems of the ISCCP datasets: (1) spatial structure is affected by the mean drifts in different sensors (2) mean bias in the tropical oceans: Too much net downward Q SW