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Ocean Surface heat fluxes. Lisan Yu and Robert Weller lyu@whoi.edu rweller@whoi.edu http://oaflux.whoi.edu. 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
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Ocean Surface heat fluxes Lisan Yu and Robert Weller lyu@whoi.edu rweller@whoi.edu http://oaflux.whoi.edu
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
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,withtechnical 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 QLH and QSH on daily/monthly and 1º-grid for the years 1981-2005. – Global QLW and QSW (1983-2004) are from ISCCP (Bill Rossow).
OAFlux: estimating QLH and QSH QLH = Le ce U (qs – qa) QSH = cp cp U (Ts – Ta) Four independent variables U, Ts, qa, and Ta. • 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 COARE bulk flux algorithm 3.0 (Fairall et al. 2003) Daily latent and sensible heat fluxes 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.
ISCCP Surface longwave and shortwave radiationsyearly-mean averaged over the global oceans
Effect on the EOF analysis The Atlantic Ocean
Problems in the ISCCP datasets(2) mean bias: QLW+QSW (1984-2002) Positive downward
TRITON heat fluxes at (1.5S, 90E) (H. Hase/IORGC) shortwave net sensible longwave latent OAFlux ISCCP (provided by Dr. Yoshifumi Kuroda)
Locations of in situ measurements All components No QLW x No QLW and QSW
Stratus buoy (693 days, 10/08/00 to 08/31/02) 30-day running mean applied Fluxes comparison statistic based on daily means ---------------------------------------------------------------------- QNETQLH+QSHQSW+QLW ---------------------------------------------------------------------- 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) ---------------------------------------------------------------------- Statistics based on daily means
Pacific Basin: TAO array The meridionally averaged mean QSW (Sep.1991 – Aug.2002) for TAO array, ISCCP, ERA40, NCEP1 and NCEP2 as a function of longitude
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 QSW