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 Spatial/Temporal Variability Skin effect SST / Sea Surface Salinity Interactions

SST/SSS Interactions Talks today

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

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

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

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

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

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

GHRSST XIV, Woodshole, 17-21June A DW dedicated Matchup database Overview - DW dedicated MDB based on SEVIRI data S to 80 N and 80 W to 80 N - June to September daily files in ~1 GB netCDF4 format. 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 Sonia Péré, Anne Marsouin, Gérard Legendre, Pierre Le Borgne Météo-France/Centre de Météorologie Spatiale, Lannion, France

GHRSST XIV, Woodshole, 17-21June Conclusion (still many mysteries…) Anyone interested please contact AATSR, METOP,… Local time

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 Tropical Warm Pool Diurnal Variability Project (TWP+) Wick Modified Kantha-Clayson DW MTSAT-1R Observed DW Castro Look-Up Table DW 26 Apr 2010 Helen Beggs, Bureau of Meteorology

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 Tropical Warm Pool Diurnal Variability Project (TWP+) MTSAT-1R Observed DW Castro Look-Up Table DW 26 Apr 2010 ACCESS-R 10m Wind

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

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

Comparison of Subskin and Foundation Estimates (Argo – SEVIRI) WarmCountBiasStdevBiasStdev Yes No All WarmCountBiasStdevBiasStdev Yes No All Subskin SST Foundation SST Castro et al., RSE, doi: /J.RSE

Comparison of Derived Diurnal Warming WarmCountsBiasStdev Yes No All Castro et al., RSE, doi: /J.RSE

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

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

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

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

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

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

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 – Kantha Clayson with wave effects – COARE – Parameterizations

Sample Forcing Fields

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

Kantha Clayson Stokes Drift Model Diurnal Warming Evolution, UTC, 21 March 2013 SAMPLE MODEL RESULTS

Comparison of Warming with SEVIRI Observations SEVIRI warming computed as SST hour – SST Foundation SST Foundation 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 SEVIRI-Derived Diurnal Warming 1400 UTC, 21 March 2013

Comparison of Observed and Modeled Diurnal Warming SEVIRI Domain – 21 March 2013, 1400 UTC K-C Stokes DriftK-C Stokes Enh (2)K-C Stokes Enhanced COAREWick K-C BlendedGentemann

Comparison of Observed and Modeled Diurnal Warming SEVIRI Domain – 21 March 2013, 2200 UTC K-C Stokes DriftK-C Stokes Enh (2)K-C Stokes Enhanced COAREWick K-C BlendedGentemann

TIME EVOLUTION OF WARMING DISTRIBUTIONS FOR MODELS

Comparison of Observed and Modeled Diurnal Warming SEVIRI Domain – 21 March 2013 Kantha Clayson Model with Stokes Drift 0200 UTC0600 UTC1000 UTC 1800 UTC1400 UTC2200 UTC

Comparison of Observed and Modeled Diurnal Warming SEVIRI Domain – 22 March 2013 Kantha Clayson Model with Stokes Drift 0200 UTC0600 UTC1000 UTC 1800 UTC1400 UTC2200 UTC

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

Extra Slides

Gentemann Parameterization Diurnal Warming Evolution, UTC, 21 March 2013

COARE Model Diurnal Warming Evolution, UTC, 21 March 2013

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

Comparison of Warming with SEVIRI Observations SEVIRI warming computed as SST hour – SST Foundation SST Foundation 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

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. Castro et al., RSE, in press