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Meteorology and Air-Sea Fluxes from Ocean Reference Stations

Meteorology and Air-Sea Fluxes from Ocean Reference Stations Al Plueddemann and Bob Weller, WHOI, Woods Hole, MA. ORS provide accurate surface meteorology and air-sea fluxes at key sites. The goals are to: Quantify air-sea exchanges of heat, freshwater and momentum

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Meteorology and Air-Sea Fluxes from Ocean Reference Stations

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  1. Meteorology and Air-Sea Fluxes from Ocean Reference Stations Al Plueddemann and Bob Weller, WHOI, Woods Hole, MA ORS provide accurate surface meteorology and air-sea fluxes at key sites • The goals are to: • Quantify air-sea exchanges of heat, freshwater and momentum • Describe the local oceanic response to atmospheric forcing • Assess and motivate improvements to NWP and satellite products • Provide anchor points for the development of new, basin scale flux fields

  2. Geographic Distribution • Three ORS are presently operational: • STRATUS (initiated Oct 2000) • NTAS (initiated March 2001) • WHOTS (initiated August 2004) UOP is also operating ASIMET meteorological systems on three VOS lines (see Weller, Bahr and Hosom poster)

  3. Stratus First long-term, high quality surface flux measurements beneath the Peru/Chile stratus deck • Key issues: • Cooling influence of stratus clouds on local and global heat balance • Role of stratus clouds in maintaining the equatorial asymmetry of sea surface temperatures and winds

  4. NTAS Long-term surface flux record in NE trade wind region of tropical Atlantic • Key issues: • Air-sea interaction processes controlling local SST variability and the cross-equatorial SST gradient • Modulation of the annual cycle of ITCZ migration and its role in regional climate dynamics

  5. WHOI-HOT Site (WHOTS) • Deployment of HOT site ORS accelerated as a result of cooperation between NOAA/OCO and NSF • Key addition to a long-standing, interdisciplinary ocean observatory • First 9 months of meteorological data available on UOP web site, mooring turnaround scheduled for July 2005

  6. Partnerships/Collaborations • ECMWF: Data Exchange • WHOTS: Fluxes for HOT; Ocean sensors from R. Lukas, UH (NSF) • NCEP: Routinely acquire and examine reanalysis products. • Stratus: Chilean Universities; Chilean and Ecuadorian Naval Hydrographic Offices; DART buoy servicing; Focal point for CLIVAR VOCALS process study • ETL: Field intercomparisons • Argo: Drifter and float deployments • Radiometer data: Instruments on NDBC buoys, Chesapeak Light Tower (BSRN); Data to PCMDI; CERES-ARM Validation Exp; Establishment of GEWEX Radiation Panel - Ocean Subgroup • NTAS: Co-located with GAGE/ MOVE transport array; Dialog with NHC/TPC for data exchange • ORS Concept: Expansion to be proposed to NSF/ORION • Participation in international planning and management activities through: CLIVAR, CCSP, OOCP, GOOS, GWEX, SOLAS, ORION, OceanSITES • With links to: NRC, WCRP, JCOMM, POGO, SURFA, CPT-Clouds, CPT-EMILIE, …

  7. Sensor Calibration • Pre- and post-calibration at WHOI and by sensor manufacturers • Field intercomparisons: buoy vs. ship and buoy vs. buoy • Adjustment of bias and drift prior to flux calculation by bulk formulas

  8. Sensor Accuracy • First-generation IMET systems evaluated by Hosom et al., 1995 • Second-generation ASIMET presently being evaluated (Colbo, et al.)

  9. The Seasonal Cycle of Surface Heating Stratus NTAS

  10. Seasonal Cycle: NTAS Comparison with NWP products and climatology Qnet: NWP biased low, 2 yr means are <0 whereas buoy shows +40 W/m2 Timing of zero-crossings differ by 1-2 months Climatology better than any of the model products t: NWP typically within 0.01 of buoy and clearly better than climatology

  11. Seasonal Cycle: Stratus Comparison with NWP products and climatology Heat flux components: Qsw: NCEP1 biased low, NCEP2 seasonal high-bias Qlw: NCEP2 biased low Qlat: Both NCEP1 and 2 show low bias Qsen: NCEP1 low bias Qnet: NCEP1 low, NCEP2 high

  12. Annual Mean Heat Flux Comparison with NWP and reanalysis products • ECMWF Qnet disagrees with buoy by ~25 W/m2 in both years • Interannual variability at buoy not reflected in ECMWF • ECMWF agrees well with climatology Stratus • NWP products under-estimate buoy Qnet by 40-50 W/m2 • Latent and shortwave fluxes are the primary contributors to discrepancy • NWP products do not agree well with climatology NTAS

  13. Improved Regional Flux Fields • Evaluation of in-situ data vs. NWP products (Sun, Yu and Weller, 2003) • Improved fluxes using NWP and satellite data: Synthesis using objective analysis, Validation with in-situ data (North Atlantic: Yu, Weller and Sun, 2004) • Diagnosis of climate trends in the synthesized fluxes • (Yu, Weller, and Jin, in progress)

  14. Heat Budget Estimates Annual mean heat budget estimated at the Stratus site (Colbo and Weller, in progress) • Non-local cooling is required to balance the surface fluxes • Upwelled coastal water has little impact at the mooring site • Eddy flux divergence is important even though overall eddy KE is relatively low

  15. Synergy with the global observing system Colbo and Weller heat budget estimate uses a combination of: • ORS mooring fluxes and heat content • Satellite winds (QuikSCAT SeaWinds scatterometer) • Satellite altimetry (TOPEX/Poseidon) • Satellite SST (Reynolds, TRMM/TMI) • Surface drifter trajectories (Pazan and Niiler, MEDS/AOML) • Climatology (World Ocean Atlas)

  16. Recommendations Improvements to ORS • Portable shipboard met standard • Direct covariance fluxes and motion packages on buoys • Near real-time heat content from moorings • High latitude sites Improved regional and global flux fields • Continued validation, assessment and synthesis studies

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