Indirect Determination of Surface Heat Fluxes in the Northern Adriatic Sea via the

Heat Budget

R. P. Signell, A. Russo, J. W. Book, S. Carniel, J. Chiggiato, H. Perkins, J. Pullen, J. D. Doyle

2004 ROMS/TOMS European Meeting

Motivations• Many processes in the Northern Adriatic Sea are strongly affected by

surface forcing (i.e., production of one of the densest water in the Mediterranean)

• Its coastal features, shallowness and surrounding complex orography critically stress the correctness of our ABL parameterizations and surface fluxes estimates, eventually degenerating model solutions

• Surface fluxes are poorly measured and their value at a basin level in the Adriatic is still an open issue.

…therefore…… we used a model-based experiment to infer what the fluxes

should have been (period fall 2002 – winter 2003), comparing changes in the heat content in the model with those estimated using observations

Hypothesis• Shallow water, strong surface cooling and vertical mixing

result in homogenization of the water columnthis allows to work with a 2D “vertically averaged temperature” field. (to be estimated via collected

data)• Although with negligible stratification, the use of a 2D

averaged temperature leads to small bias (to be evaluated).we need to compute somewhat error bars associated to the estimates

• *When* the lateral advection of heat outward/inward the basin is playing a minor role, changes in the heat content can be related to exchanges at the air-sea interface

we run the model to check when this is supposed to be applicable

ADRIA 2002data

Transect bounding our domain

Selecting suitable days (clear sky and wind dominated…)

Comparison SST data vs moorings

Full mixing conditions hypothesis: SST, surface and bottom temperature revealed similar

Heat content by means of measurements

• Selection of clear sky –wind dominated days in order to have good SST images

• Check if data suggest nearly full mixing• Estimate of the heat content:

– Lower bound: SST - OA (SST-SBT) – Upper bound: SST – OA (SST-SSTBULK)– Reference temperature = mean between the two

bounds

Model Set-Up

FullABL

Limited Area Model ItalyNon-hydrostatic

7 Km horz resolution, 3-hourlyOperational forecast twice a day00+03…+12, 12+03…+12 GMT

Open Boundary:Tidal elevation and currents

48 rivers,daily runoff:

measured or climatology

Initialization: spun up at rest with temperature and salinity fields obtained by

OA on data collected during the cruise ADRIA 02 (late sep 2002)

Grid 160x60 variable resolution up to 3 Km

to the North

Length of the run: Sep 02 -- > Jun 03

Is the lateral advection of heat playing a minor role?

Are our modeled transports consistent with

measurements (ADCPs)?

Evaluation of the heat content estimate methods on ROMS output

Comparison between ROMS and LAMI fluxes

Comparison between ROMS and LAMI fluxes

• LAMI turbulent fluxes are always more negative• COAMPS turbulent fluxes show similar values as LAMI

• This is due to different parameterizations of fluxes, not to the SST used by ALAMs (we tested)

Question: Which one is realistic? Is at least one of them realistic?

What if we run applying the fluxes as they come from the met model?

Conclusions• by carefully choosing nearly cloud-free images during periods of nearly uniform

mixing, we computed heat content estimates of the Northern Adriatic Sea by means of the SST and in-situ measurements, during 5 different days between November 2002-February 2003 (planning to have more);

• model results indicate that, in the period investigated, the heat budget is dominated by surface fluxes;

• the total heat fluxes resulting from the ROMS/LAMI simulation fall within the reasonable bounds of total heat fluxes determined by data in each of the 4 intervals studied, indicating that using ROMS SST with LAMI meteo parameters and its own bulk formula (Fairall, 1996) is producing results as good as can be determined by data;

• care must be taken when computing these estimates and associated errors (feedbacks are welcome!!!), depending then very much on the nature and distribution of available data;

• LAMI (and COAMPS) turbulent fluxes are too high, indicating a suboptimal bulk flux parameterization over the ocean during strong forcing events; care must be taken when using directly model derived turbulent fluxes.