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The Physical Basis of SST Measurements One (biased) look at progress

The Physical Basis of SST Measurements One (biased) look at progress. Gary A. Wick NOAA ESRL/PSD October 29, 2013. Physical Basis – Priority Topics. Diurnal Variability Spatial/Temporal Variability Skin effect. Physical Basis – Priority Topics. Diurnal Variability

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The Physical Basis of SST Measurements One (biased) look at progress

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  1. The Physical Basis of SST MeasurementsOne (biased) look at progress Gary A. Wick NOAA ESRL/PSD October 29, 2013

  2. Physical Basis – Priority Topics • Diurnal Variability • Spatial/Temporal Variability • Skin effect

  3. Physical Basis – Priority Topics • Diurnal Variability • Spatial/Temporal Variability • Skin effect • SST / Sea Surface Salinity Interactions

  4. SST/SSS Interactions • Talks today

  5. Skin Effect • Undertake additional research into the physics and modeling of the skin effect • Improve our understanding of how errors in model forcing parameters impact skin model errors • Relevant measurements continue • MAERI and other radiometric time series • Marginal Ice Zone Processes Experiment - MIZOPEX • Radiometric and in situ SST measurements near melting ice

  6. Spatial/Temporal Variability • Develop methods to integrate an improved understanding of the SST variability into the SST retrievals error • Expand the library of sub-pixel scale SST data sets • Improve understanding of sub-pixel scale variability to better characterize the contribution of point-to-pixel errors to overall retrieval uncertainty estimates • Explore methodologies to validate representation of spatial variability in SST products • Investigate development of a high-resolution μ-wave sensor

  7. Spatial Variability - Activities • MIZOPEX • UAS-based infrared imagery collocated with surface observations • Satellite-buoy comparisons • Frontal Work

  8. L4 SST Analysis Evaluation in the Beaufort Sea • Castro et al., in preparation

  9. Diurnal Variability • Continue/expand research into development of diurnal warming models and analysis of satellite observed diurnal warming • Improve specification of diurnal model uncertainty • Continue and expand research into the role of penetrating radiation and its relationship to available optical properties in the water column • Perform additional field observations of diurnal warming events • Develop/enhance links with other communities with interests in diurnal warming such as the ocean color and the meteorological communities

  10. Diurnal Variability - Progress • Measurements • Satellite-based • Diurnal warming matchup database • TWP+ • Climatology work • In situ • Argo • SPURS • Models

  11. A DW dedicated Matchup database Overview - DW dedicated MDB based on SEVIRI data. - 20 S to 80 N and 80 W to 80 N - June to September 2012. - daily files in ~1 GB netCDF4 format. Sonia Péré, Anne Marsouin, Gérard Legendre, Pierre Le Borgne Météo-France/Centre de MétéorologieSpatiale, Lannion, France • Content • Continuous drifting and moored buoy measurements • “sst” and “flx” data in a 5-pixel square box in satellite coordinates • box is centred at the nearest pixel to the buoy position • Model outputs: • air temperature at 2m, air humidity at 2m, • surface pressure and integrated water vapour • wind speed at 10m GHRSST XIV, Woodshole, 17-21June 2013

  12. AATSR, METOP,… Local time Conclusion (still many mysteries…) Anyone interested please contact Gerard.Legendre@meteo.fr GHRSST XIV, Woodshole, 17-21June 2013

  13. MTSAT-1R Observed DW Castro Look-Up Table DW Wick Modified Kantha-Clayson DW Tropical Warm Pool Diurnal Variability Project (TWP+) 26 Apr 2010 Helen Beggs, Bureau of Meteorology Aims • Assess multiple satellite SST products over TWP • Quantify diurnal warm-layer events using satellite data • Assess ≥ 8 diurnal warming models run using common inputs Period Jan–Apr 2010 Location 25°S to 15°N, 90°E to 170°E Collaborators Bureau of Meteorology, NOAA, Meteo- France, Met Office, WHOI, Uni of Colorado, Uni of Edinburgh, Uni of Arizona, Uni of Miami, JMA

  14. Tropical Warm Pool Diurnal Variability Project (TWP+) 26 Apr 2010 MTSAT-1R Observed DW TWP+ Data Set • Satellite SST • IR: AVHRR (METOP-A, NOAA-17,18 & 19) • IR dual-view: AATSR (Envisat) • MW: AMSR-E (AQUA) • MW: WindSat (Coriolis) • Geo: JAMI (MTSAT-1R) • Bureau Regional foundation SST Analysis (RAMSSA) • In Situ SST (buoys, ships) • Bureau Numerical Weather Prediction surface flux fields (ACCESS-R) • Bureau Sea State Forecasts (AUSWAM) • 7 DV Model outputs Castro Look-Up Table DW ACCESS-R 10m Wind

  15. Diurnal Warming Climatology • NASA funded project • How large is DW throughout the globe and how do magnitudes vary with season? • How does frequency vary with magnitude? • What are the spatial scales of DW? • Influences on air-sea fluxes and climate variability

  16. Diurnal Variability - Progress • Measurements • Satellite-based • Diurnal warming matchup database • TWP+ • Climatology work • In situ • Argo • SPURS • Models

  17. Castro et al., RSE, doi:10.1016/J.RSE.2013.08.042 Comparison of Subskin and Foundation Estimates (Argo – SEVIRI) Subskin SST Foundation SST

  18. Castro et al., RSE, doi:10.1016/J.RSE.2013.08.042 Comparison of Derived Diurnal Warming

  19. Dedicated ARGO Diurnal Warming Experiment • Discussed at GHRSST 2013 Science Team Meeting • Dedicated experiment “perfectly doable” • Majority of new floats use iridium communications • Float could repeatedly sample near-surface ocean for period of 3-5 days • Willing to explore sampling closer to surface • Group to develop plans for experiment of opportunity • Explore forecasting capability

  20. Diurnal Variability - Progress • Measurements • Models • Clayson and Bogdanoff • Weihs and Bourassa • Karagaliand Høyer • Coupled modeling • Scanlon et al. • Wick • …

  21. GHRSST DVWG Focus • Desired approaches/requirements for diurnally resolved SST • Provision of diurnal warming estimates • Temporal frequency • Representative depth • Representative spatial scale • Direct provision of models/parameterizations • Provision of error characteristics for existing models and predictions • Increasing available validation data • Understanding of basic physics

  22. Scanlon et al., Ocean Science, in press • Compared simulated near-surface temperature profiles from the Kantha-Clayson model with observations from SkinDeep • Individual profile comparison difficult, but reasonable agreement in average sense • Base scheme performed well • Provides some estimate of errors with depth

  23. Real-Time Diurnal Warming Estimates Forced with GFS Model Inputs Gary A. Wick NOAA ESRL/PSD

  24. Motivation • Compensation for presence of diurnal warming in SST analyses • Facilitation of further comparison and validation of models

  25. Components • Model Inputs • GFS analysis fields, 6 hourly, 0.5 degree • Wind stress • Radiative and turbulent fluxes • Wave Watch III Wave Model • Wave period, direction, and significant wave height • Models initially evaluated • KanthaClayson with wave effects • COARE • Parameterizations

  26. Sample Forcing Fields

  27. Logistics • Models initialized based on SST • Fluxes interpolated to model time step • Model run globally for 2 days with output taken from the second day • Warming taken as Tsubskin - Tdepth • Warming compared against SEVIRI observations

  28. Sample model results KanthaClayson Stokes Drift Model Diurnal Warming Evolution, 00-23 UTC, 21 March 2013

  29. Comparison of Warming with SEVIRI Observations • SEVIRI warming computed as SSThour– SSTFoundation • SSTFoundationcomputed as nighttime average • Initial comparison in terms of warming distribution • Tests models ability to reproduce range of diurnal warming • Less sensitive to errors in model wind stress • Supplementary absolute comparisons to follow SEVIRI-Derived Diurnal Warming 1400 UTC, 21 March 2013

  30. Comparison of Observed and Modeled Diurnal Warming SEVIRI Domain – 21 March 2013, 1400 UTC K-C Stokes Drift K-C Stokes Enh (2) K-C Stokes Enhanced Wick K-C Blended COARE Gentemann

  31. Comparison of Observed and Modeled Diurnal Warming SEVIRI Domain – 21 March 2013, 2200 UTC K-C Stokes Drift K-C Stokes Enh (2) K-C Stokes Enhanced Wick K-C Blended COARE Gentemann

  32. Time evolution of warming distributions for models

  33. Comparison of Observed and Modeled Diurnal Warming SEVIRI Domain – 21 March 2013 KanthaClayson Model with Stokes Drift 0200 UTC 0600 UTC 1000 UTC 1400 UTC 1800 UTC 2200 UTC

  34. Comparison of Observed and Modeled Diurnal Warming SEVIRI Domain – 22 March 2013 KanthaClayson Model with Stokes Drift 0200 UTC 0600 UTC 1000 UTC 1400 UTC 1800 UTC 2200 UTC

  35. Summary • Automated daily computation of global diurnal warming from NWP forcing coming on line for application to SST analyses • Distribution of diurnal warming reasonably well reproduced • Some instances of persistent warming, but not entirely without support • Display, distribution, and further evaluation of products to follow

  36. Extra Slides

  37. Gentemann Parameterization Diurnal Warming Evolution, 00-23 UTC, 21 March 2013

  38. COARE Model Diurnal Warming Evolution, 00-23 UTC, 21 March 2013

  39. Scanlon et al., Ocean Science, in press • Compared simulated near-surface temperature profiles from the Kantha-Clayson model with observations from SkinDeep

  40. Comparison of Warming with SEVIRI Observations • SEVIRI warming computed as SSThour – SSTFoundation • SSTFoundation computed as nighttime average • Initial comparison in terms of warming distribution • Tests models ability to reproduce range of diurnal warming • Less sensitive to errors in model wind stress • Supplementary absolute comparisons to follow

  41. Castro et al., RSE, in press Conclusions: The potential utility of Argo data for diurnal warming applications has been a key question for the DVWG • Results demonstrate remarkable consistency between the estimates of the subskin and foundation temperatures and corresponding diurnal warming from SEVIRI and unpumped Argo. This lends support to both products and associated methodologies. • Unpumped Argo floats provide accurate estimates of diurnal warming. They constitute a very valuable independent data set for L4 SST validation and diurnal warming studies, suggesting we advocate for more unpumped Argo floats.

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