Air-Sea Interactions in Tropical Cyclones Workshop

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Appendix C: List of Participants/Breakout Groups (1/2, C:Chair)

Visitor (Break Out Group) Affiliation E-Mail

Bao, Jian-Wen (1) NOAA/ETL

Barnes, Gary (1) University of Hawaii

Bender, Morris (1) NOAA/GFDL

Black, Peter (1) NOAA/AOML

Chang, Paul (1) NOAA/NESDIS

Cione, Joe (1) NOAA/AOML

Conteras, Bob (1) University of Massachusetts

Drennan, Will (1-C) University of Miami

Fairall, Chris (1) NOAA/ETL

Falkovich, Alexandr (1) NCEP/EMC

Fernandez, Dan (1) NOAA/NESDIS

Foster, Ralph (1) Applied Physics Laboratory

French, Jeffrey (1) NOAA/OAR/ARL

Gaynor, John (1) NOAA/OAR

Ginis, Isaac (1) University of Rhode Island

Girton, James (1) University of Washington/APL

Halliwell, George (2) University of Miami

Hara, Tetsu (2) University of Rhode Island

Howard, Armando (2) NASA/Goddard

Jacob, S. Daniel (2) NASA/GSFC

Liou, Chi-Sann (2) NRL/MRY

Liu, Qingfu (2) NCEP/EMC

Lord, Steve (2) NCEP/EMC

Lozano, Carlos (2) NCEP/EMC

Lumpkin, Rick (2) NOAA/AOML

Shay, Lynn (Nick ) (2) University of Miami

Surgi, Naomi (2) NCEP/EMC

Terrill, Eric (2) Scripps Institution of Oceanography

Tolman, Hendrik (2) NCEP/EMC

Tracton, Steve (2) Office of Naval Research tractos@ONR.NAVY.MIL

Tuleya, Bob (2) NCEP/EMC

Uhlhorn, Eric (2) NOAA/AOML

Vincent, Linwood (2) Office of Naval Research vincenc@ ONR.NAVY.MIL

Waldrop, John (2) NCEP/EMC

Walsh, Ed (2) NOAA/ETL

Wilczak, James (2-C) NOAA/ETL

Yablonsky, Richard (2) University of Rhode Island

Appendix D: Workshop Organizers

Naomi Surgi


National Weather Service

Camp Springs, DC


Phone: 301-763-8000 (Ext 7285)

Cell: 240-676-5016

Fax: 301-763-8545

Lynn K. (Nick) Shay

Division of Meteorology and Physical Oceanography

Rosenstiel School of Marine and Atmospheric Science

University of Miami

Miami, FL. 33149


Phone: 305-421-4075

Cell: 305-205-0305

Fax: 305-421-4696

Joseph J. Cione

NOAA Hurricane Research Division

Atlantic Oceanographic and Meteorological Laboratory

Miami, FL. 33149


Phone: 305-361-4406


Appendix E: Data needs for the Air-Sea Component of Coupled Hurricane WRF

Necessary types and resolution of observations to define the coupled ocean-atmosphere problem for modeling:

1) Ocean structure and heat content

  • Essential for verification (T, u, v, S)

  • Radial and azimuthal resolution - critical between center and 200-250 km (24 h) ahead of storm

  • Vertical resolution – mean values in the mixed layer critical – need to resolve mixed layer (2-4 m resolution)

2) Wind

  • radial resolution most important – 0.5-1.0 km

  • height resolution next most important – high resolution (100 m) in ABL, outflow, and to resolve eyewall

3) Moisture

  • Vertical structure and latent heat fluxes

  • Height resolution critical – high resolution (100 m) in ABL.

  • Azimuthal resolution next most important

  • Radial resolution – a function of Rmax.

4) Temperature profile

  • Vertical structure and sensible heat fluxes

  • Mean vertical profile, plus variation in radius

  • Height resolution critical – high resolution (100 m) in ABL and near tropopause.

  • Resolution a function of Rmax.

5) Ocean waves

  • Essential for verification

  • Azimuthal structure critical – resolve asymmetry in wave height and length – wave# 2

  • Radial structure next critical – resolve radius of 8’ and 12’ seas - 20-50 km

Appendix E: Instrumentation needs for the Air-Sea Component of Coupled Hurricane WRF

  1. Oceanic Structure

  • Aircraft Expendables (AXCPs, AXCTDs, AXBTs): Weakness: limited time resolution

  • Profiling Floats: Weakness: deployment into fronts

  • Satellite IR. Weakness: no data in cloudy regions

  • Satellite altimetery. Weakness: vertical projection in models

  • Interferometric SAR: Weakness surface currents only

  • HF radar networks: Weakness large gaps along the coastline

  • Fixed/drifting buoys. Weakness limited spatial resolution (Cannot deploy in Loop Current, Gulf Stream)

2) Wind

  • Airborne and ground based Doppler radars (limitation is winds only where it is raining, and poor vertical coverage near the surface because of ground clutter)

  • Satellite Scatterometers/SAR and cloud drift winds (Weakness of scatterometer/SAR: only at the surface level. Weakness of cloud drift winds: coarse and uncertain vertical resolution

  • Surface drifters: Weakness: one level

  • Aircraft in-situ. Weakness: one level.

  • Dropsondes. Weakness: limited spatial resolution

  • Doppler LIDAR. Weakness: limitation to winds in non cloudy regions.

  • SFMR. Weakness: only at surface.

  • IWRAP?

3) Waves

  • Radar altimetery (SRA):Weakness only Sweel Components

  • Laser altimetery. Weakness limited to no cloud or precipitation

  • Fixed/drifting buoys. Weakness limited spatial resolution

  • Solo Floats

  • SAR imaging

4) Moisture

  • Dropsondes/Rawinsondes. Weakness: limited spatial resolution

  • Microwave radiometric/interferometry. Weakness: limited vertical resolution

  • Aircraft in-situ. Weakness: one level


5) Temperature

  • Dropsondes/Rawinsondes. Weakness: limited spatial resolution

  • Radiometric/interferometry. Weakness: limited vertical resolution

  • Aircraft in-situ. Weakness: one level

6) Rainfall

  • Buoys/ground stations. Weakness one level and limited spatial coverage

  • Radar/polarization diversity. Weakness limited vertical resolution, limited view near coastline, and calibration between radars

  • SFMR rain. Weakness one level surface

  • Satellite. Weakness: limited to cloud/no cloud

  • Profilers and sub-millimeter radars

Appendix F: Breakout Group 1 Notes

Data Base for Observation-Model Comparisons: CBLAST and other data constitute a good basis for joint investigations by operational/OAR/University researchers: Need to create data base

What Ocean data are available?

    • 1988 - Hurricane Gilbert (Shay)

    • 2002 – AXCP, AXCTD, AXBT; Isidore and Lili (Shay and Uhlhorn)

    • 2003 – CBLAST 10 drifters/profilers Fabian

    • 2004 – CBLAST 40 drifter/profilers Francis and Jean

    • Collections of current profilers before/after storms – Steve Riser

  • What Atm data are available?

    • HRD data base

    • Various NSF/CBLAST field programs

    • Coastal Radars

  • What model outputs (initializations, NWP fields, HWIND)

  • What satellite data

  • Other data – waves, buoys,

  • Metadata – descriptions, reports, papers, movies

Recommend allocating resources to set up infrastructure to create data base for existing data and facilitating rapid production of usable, quality controlled, standard products, integrated data for future hurricane program (HRD, FSU, NCAR-JOSS, NCDC?)

Maximize Usefulness of the data base

  • Already discussed the need for model-usable data archive

  • Questions about what data in which form

  • Streamline future observation analysis

  • Analysis of model outputs with data

  • Comprehensive, easy to use

Observational Technologies Research and/or Transition to Operational

  • Walsh’s scanning radar wave measurement – 2D spectra available in realtime

  • UAV – near surface fluxes/BL

  • Airborne remote sensors for look-down near surface measurements (sea spray, wind profiles, breaking wave characteristics, )

  • ARL batprobe for buoys (research)

  • Ocean profilers

Our Big Three (four):

  • Public data base for model studies to promote joint studies (see slides 1&2)

  • Basic structure of near-surface BL in both ocean and atmosphere

    • Secondary Circulations

    • Mean profiles (u,T,q)

    • Upper boundary (fluxes, definition,..)

  • Sea spray and enthalpy transfer coefficient U>30 m/s still a big question

  • Ocean problems

    • Initialization

    • Mixing parameterizations

What observations to test coupled ocean-atmosphere models

  • Before – snapshot synoptic field of ocean structure to 200 m …1000 m(u,v,T,S)

  • During

    • Float array (u,v,T, S, P, waves, acoustics)

    • Airdrop profiler snapshots in storm

    • 2-D wave spectra surveys

    • Standard a/c everything package

  • After – another snapshot along track

  • Routine

    • NDBC enhancements (thermistors, stress,…)

    • ARGO, APEX floats; drifters

    • Coast Radar (HF, WSR-88D)

    • Gliders

What observations to advance coupled ocean-atmosphere physics and develop parameterizations: atmospheric

  • Sea spray profiles below 50 m

  • Direct turbulent flux profiles

  • Mean profile structures (radius, quadrant, etc)

  • Complete 2-D wave spectra and wave breaking statistics

  • Accurate fields of rain rate

  • Near surface bulk variables

Appendix G: Breakout Group 2 Notes

  • We are still a long way away from many aspects of the project (bulk transfer coefficient)

  • Advancement of physics is a long term project.

  • Just because we haven’t made vast improvements, we are working toward a long-term goal

    • It may look like the GFDL model, but there are long term goals

  • There is improved skill in the operational model

  • Incremental upgrades => bigger impact on some things like track forecasting

  • We can’t degrade the track forecast in the HWRF or the project will not be accepted

  • Same model is used for the East Pacific

    • Must also make sure that the East Pac forecast isn’t degraded

  • Started talking about what the actual weak points are of the project

    • Is it model components or the coupling?

      • Getting models to run together

      • Deciding what we are going to transfer between models

      • Physics problem & the coupling problem

  • Increasing the levels from 42 to 64

    • This vertical upgrade should vastly improve the forecast

  • Navy doesn’t seem interested in the intensity of the storms

    • Intensity isn’t correlated to the structure of the storm

  • There is a need for scale dependent background

  • Observational programs are very expensive

    • Must fully-utilize programs that we currently have

  • There is difficulty in getting flux in high winds

  • Hurricane Center needs buoy data

    • Wave part doesn’t use data assimilation because of how quickly it moves away

  • Is the ocean data coming in real-time? No- but it will be coming in soon

  • Overcooling the upper ocean causing the air-sea interaction to die and the storm doesn’t develop

  • How should we deal with compensating errors?

    • We should try and put in the best science

  • Need multiple parallel tracks

    • One for the best physics

    • Another one for research purposes and have the best science

    • Finally, one that does best in reality

  • Until we have the observations of intensity, it’s useless putting a forecast out.


  • Series of sensitivity tests on coupled system when it becomes available

  • Researchers need access to model output and vice-versa

  • Maximize use of data sets

  • Determine which data has value to assimilation, evaluation, validation

Where should we go in the next 5-10 years as far as modeling?


  1. Uncertainty in air-sea parameterizations, and depending on what you do, one can obtain any intensity that can be tuned to fit the best track data. From an observational perspective, we have to place error bounds on what are realistic values, but we still must address these parameterizations (e.g. ch, cd, sea spray).

  2. Timeline for HWRF is 2007 which sets the physics timeline. By this time next year, GFDL physics will be frozen, so advancements in physics will occur after this GFDL freezing. In other words, the physics of HWRF will be similar to GFDL.

  3. What observations will be useful for data assimilation? and for model evaluation (vice



  1. Constrained by resolution (i.e. computer resources) in terms of what we can explicitly resolve vs. what is parameterized.

  2. Can the intensity problem be addressed given the current resolution of the models? To some extent, but we must work within our computational constraints, so we should ask, “what can we address given a 9-km grid spacing?”


  1. If nothing else is done between now and 07 other than build the HWRF infrastructure and migrate the physics, it must be at least as skillful as GFDL to become operational.

  2. That is one of the issues. In HWRF development, comparing against the heavily tuned GFDL model so we might require a scientific side path to get the HWRF as good as GFDL.

  3. Purpose of everyone being here is that if all goes as planned with an operational HWRF in 07, then as long as we have been working on improvements all along, it will be possible to implement these improvements much faster (soon after initial operations).

  4. There should be opportunities for statistics and data to become available to researchers immediately so researchers can advise the forecasters in a timely manner


  1. Where are the biggest weaknesses? In the atmospheric, wave, or oceanic components? The first issue is getting all of the three components to work together correctly (technical issue). This is the current problem. Second issue: what parameters do you transfer between the different model components?

  2. For the atmospheric side, the parameterizations are the key issue. The other problem is the coupling problem between the various models.

Physics and Assimilation Issues:

  1. For ocean and wave model, are there similar parameterization problems such as incorporating Stokes drift, Langmuir Cells, wind-driven currents, and small-scale turbulence in wave model.

  2. Increase in vertical resolution from 45 to 64 levels, will affect physical parameterizations and in some cases not necessarily cost-effective for the gain in resolution (i.e. diminishing returns)

  3. From Navy’s perspective, intensity problem should be separate from structure problem and may not be well correlated. That is, structure problem may be more amenable to advances in prediction than just intensity (max winds). This contrasts the NCEP view in that storm structure is well correlated to intensity.

  4. Underestimating the work required for good data assimilation into the models. What other than satellites would be helpful for modelers? AXBT’s, altimeter data, floats, aerosondes (UAV) for boundary measurements. These data should be able to be assimilated if it improves background states and intensity/structure predictability.

  5. Coastal Ocean Observing Systems are including high frequency Doppler current radars along the US coastline. Surface current measurements can help constrain the coastal ocean models (nudge towards reality) or Coastal Ocean Data Assimilation Experiments.

  6. Big issue: is the evaluation of model simulations in that it requires enough data coverage in space and time to account for model bias and uncertainty This is especially true when resolution decreases from submesoscale (<10 km) to the mesoscale (50 to 100 km). Observations must also capture this variability for a true comparison. We do not have enough of basic ocean data (T, S, u, v).

  7. Need differing types of observations (Eulerian and Lagrangian) to assess model performance in the global and coastal oceans. Most of these data used to be for local purposes, but now they are becoming widely available at various websites. Evaluation of model output must be done with data not assimilated into the model-parallel numerical experiments.

  8. Impact studies for each type of satellite data assimilated into models at NCEP-which satellite(s) are providing more bang for the buck.

  9. In only a few storms, we have model simulations with in situ data. Need to quantitatively assess cooling patterns (magnitude and spatial extent). However, cooling is sensitive to shear and stress-induced mixing parameterizations. Will we get better parameterizations or better assimilations from new observations?

Air-Sea Parameterizations:

  1. Observations suggest a leveling off of ch and cd some of which were based on similarity theory in the surface layer. Is this valid under high wind conditions? How do we parameterize the fluxes that can differ by factor of 2 depending on assumptions and surface layer thickness? Challenge is acquiring concurrent measurements in both fluids to address the problem.

  2. z0 has wind speed and wave age dependency, but what about enthalpy flux above 30 m s-1 which may be constant. One possibility is to use ocean velocity measurements of mixed layer as evidence of momentum flux. Gridded ocean observations to help close the ocean mixed layer heat and salt budgets to estimate heat fluxes. Difficult to close the oceanic heat budget in high wind conditions, diagnostic model fields are beginning to converge to observed fields, but these simulations are sensitive to the imposed mixing scheme, initial ocean conditions and wind field. Still cannot get turbulent flux measurements down to 10-20 m… Note the same PBL and surface physics are in HWRF and GFDL. Current state is that GFDL is coupled to POM that will be coupled to HYCOM.

  3. There may be PBL issues related to resolution and at high-resolution, can get double-counting of eddies because of PBL parameterization being based on large eddy statistics. GFDL ocean and atmospheric data are archived, so these data can be validated w/ observations. Oceanographers can start looking at HYCOM output where observations show warmer mixed layers than predicted. This bias may be due to the fact that NRL initializes from biased climatology.

Model Initialization:

  1. Is there a sense in the model community of how much error there is in the initial ocean state prior to the storm? When you incorporate upper ocean observations that is much warmer than climo, it can make significant improvements in model simulations.

  2. What other kinds of observations are on the horizon? Drifters that can take temp (have thermistor chains) deployed by aircraft with an expected lifetime of months-year. Difficult to make good current and shear measurements from drifters.

  3. What spatial scale is required for moorings to make a significant improvement in models?. Assimilating data in wave models is pointless because there is no way of evaluating (eventually validating) the results. Need wave buoy data or SAR data from satellites etc. For the modeling effort, wave observations are not important, but it is vital for forecasters… it would be great to have the wave data from aircraft available in real time. SRA will eventually be transferred to NOAA with data link to NHC to acquire wave spctra from the time the aircraft leaves the coast until it gets back.

  4. Two issues with waves: if a sensor is deployed on a buoy/float in front of a hurricane, you will at best get a 1-D spectra because array is too small to get 2-D. Compact Doppler sonars can give you 2d, but it is difficult and you will need several buoys and floats to get the 2-D wave field. From data collection standpoint, it is much more feasible to collect wave data from aircraft ahead of storm (continuous measurements) than dropping buoys a few days in advance (risky because storm may avoid buoys).

  5. Oceanic mixing parameterizations: 6 diff mixing schemes yields 6 diff answers… can overcool upper ocean, etc…“coupled” model system is really just 3 models running together. It is important to test one or two at a time and conduct sensitivity studies to evaluate the output, rather than couple three differing models together with a detailed set of agreed upon metrics for rigorous evaluation.

  6. How should oceanic and atmospheric turbulence interact w/ the wave model where a vertical resolution of 1-2 m in the vertical is necessary in the surface mixed layer. SHOULD get down to this res. and do sensitivity experiments. In atmosphere, have sharp changes near surface, which is why surface layer fluxes are needed to rather resolve this. On the ocean side, when energy is transferred from atmos to ocean, see large diff when using 1 m resolution than when using 10 m resolution.

Coupling and Compensating Errors:

  1. What is the correct philosophical approach to dealing w/ compensating errors, esp. when dealing with coupled models. By including, e.g. wave model results in atmosphere model, could be including more realism.

  2. Need to put the best science first and foremost, but this may degrade the forecast, and forecasters won’t deal with a degradation in track forecast. Have two parallel model experiments with a control data set with one model tuned by best forecasts and one with the “best” physics as we understand it. NCEP is always making tradeoffs…

  3. Parameterizations are not perfect… meant to work in specific ranges… the “compensating errors” are what keep everything running. You run into all kinds of problems when you do “plug and play” physics because everything interacts nonlinearly. Sensitivity testing of different parameterization for numerical models require data (moored ADCPs from Ivan, airborne profiles from Isidore and Lili, float measurements in Frances, Georges mooring data) with concurrent atmospheric measurements. Thus we need to maximize use of the sparse (available data sets).

  4. Should feel comfortable enough with bulk transfer coefficients and sea spray to implement into model over the next two years. Still working on the vertical mixing scheme – only a few good data sets with current and shear to test schemes.

  5. Evaluating coupled models on storm “intensity” is not enough rather should also include size or storm structure in addition to max wind. Waves would be much worse in bigger storm… perhaps maximum wave height? At the present time it doesn’t make sense to have wave metric because of lack of observations. Till 4 years ago, ATCF files just contained max winds, radius to max winds, pressure, and track location. Now includes max winds and location in each quadrant as well. If there is a strong signal, it should be model independent.


  • Series of sensitivity tests on coupled system when it becomes available

  • Researchers need access to model output and vice-versa

  • Maximize use of data sets

  • Determine which data has value to assimilation, evaluation, validation

Experimentalists and theorists need to be aware of why or how model parameterizations perform under differing conditions. Forecasters have a responsibility to provide good forecasts, whereas experimentalists and theorists have a responsibility to acquiring high quality measurements and understanding them within the context of good science.

Note that we don’t want duplication of effort… so communication between NCEP and other researchers are vital. Funding must be allocated for standardizing the observational and numerical data in a format that is easily and publicly accessible.
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