ROMS Operational in the Adriatic Sea: the AdriaROMS ocean forecasting systemJ Chiggiato a, M Deserti b, S Tibaldi b, T Paccagnellab, A Valentini b

a Istituto di Scienze Marine, Consiglio Nazionale delle Ricerche, Venezia, Italy b Servizio Idro-Meteorologico, ARPA Emilia Romagna, Bologna, Italy

Introduction

The Hydro-Meteorological Service of ARPA Emilia-Romagna (ARPA-SIM) provides a service of sea-state and oceanographic numerical forecasting, as a side activity of weather forecast, the core business. Adriatic Sea sea-state and ocean forecast are published daily on the public website www.arpa.emr.it/sim/?mare (see web page panel to the right). The forecast system is composed by a wave model (SWAN), run over different geographical domains and with different resolutions, and by the ocean model ROMS, running over the full Adriatic Sea since June 2005.The models are forced by the surface output fields of the limited area meteorological model COSMO-I7, a non-hydrostatic numerical weather prediction model (formerly known as LAMI, Limited Area Model Italy). Data and numerical model outputs are necessary for several applications dedicated to support the ICZM by the Regional Government as well as to support the coastal hazard early warning released by the national and regional civil protection services.

AdriaROMS system

The AdriaROMS operational ocean forecasting system is based on the Regional Ocean Modeling System. This configuration set up for the Adriatic Sea has a variable horizontal resolution, ranging from 3 km in the north Adriatic to ~10 Km in the south, with 20 s-coordinate levels. Regarding model kernel, MPDATA scheme (Margolin and Smolarkiewicz, 1998) is used for advection; a Laplacian operator adds a weak grid-size dependent on horizontal diffusivity, while no horizontal viscosity is used. The Mellor and Yamada scheme is used for the vertical mixing, and density Jacobian with spline reconstruction of the vertical profiles is used for the pressure gradient.Surface forcing is provided by the limited area model COSMO-I7 (Italian implementation of the LM model, Steppeler et al, 2002), a non hydrostatic numerical weather prediction model with 7 km horizontal resolution providing tri-hourly shortwave radiation, 10 m wind, 2 m temperature, relative humidity, total cloud cover, mean sea level pressure and precipitation. All of them are used to compute momentum and heat fluxes. Long wave radiation is estimated using, Berliand formula (Budyko, 1974), turbulent fluxes following Fairall et al. (2003). Data provided by the general circulation model of the Mediterranean MFS are used at the open boundary to the south, with relaxation-radiation boundary conditions and superimposed four major tidal harmonics (S2, M2, O1, K1), from the work of Cushman-Roisin and Naimie (2002). Forty-eight rivers and springs are included as well, using monthly climatological values from Raicich (1996). Persistence of daily discharge measured one day backward is used for the Po River, the larger.

Up to now, two different operational systems have been implemented:

AdriaROMS 1.0 - initialized in September 2004 with model data provided by MFS model, objectively analyzed onto ROMS grid. ROMS version is 2.1. Starting from June 2005, forecasts have been published on the web.

AdriaROMS 2.0 - initialized in September 2006, based on CTD data collected during the project Dynamics of the Adriatic in Real Time (DART06) objectively analyzed onto ROMS grid. AdriaROMS 2.0 is based on ROMS-2.2, and in Novemebr 2006 it became the official AdriaROMS version, with AdriaROMS-1.0 no longer used. Soon will be implemented a version with ROMS-3.0.

There are some relevant differences between versions 1.0 and 2.0, besides the initialization and the actual ROMS version. In fact, in AdriaROMS-1.0 the advection for tracers was resolved using third order upstream; bulk fluxes were estimated using 1996 version of Fairall et al.; at the boundary Clamped OBC were used and no evaporation-precipitation flux was considered. Preprocessing options for AdriaROMS-2.0 are shown in the panel to the right..

AdriaROMSBathymetry

(Source NURC, La Spezia, IT)

COSMO-I7 (formerly LAMI)

• wind 10 m • mean sea level pressure• air temperature 2 m• dew temperature 2 m• total cloud cover• net short-wave radiation

MediterraneanGCM MFS(by INGV)

daily temperature, salinity and momentum

+tidal elevation and

currents (M2, S2, O1, K1) from QUODDY model

48 rivers and springs

RESTARTfrom previousforecast

COSMO-I7 forecast 00+00 … 00+72

Po constant; others clima

00 UTC00 UTC -24 h 00 UTC+ 72 h

-24 -21 -18 -15 -12 -09 -06 -03

+03 +06 +09 +12 +15 +18 +21 +24 +27 +30 +33 +36 +39 +42 +45 +48 +51 +54 +57 +60 +63 +66 +69 +72

Short-termCOSMO-I7forecast (12 hrs)

Measured Po,others clima

OPA forecasted daily fields + astronomical tide

meteo

rivers

openboundary

PreProcessing Options AdriaROMS 2.0 /* ** Options for AdriaROMS 2.0 */ #define CURVGRID #define UV_ADV #define UV_COR #define DJ_GRADPS #define TS_MPDATA #define SPLINES #define TS_DIF2 #define MIX_GEO_TS #define NONLIN_EOS #define SALINITY #define MASKING #define SOLVE3D #define TS_PSOURCE #define UV_PSOURCE #define STATIONS #define AVERAGES #define AVERAGES_AKV #define AVERAGES_AKT #define AVERAGES_AKS #define AVERAGES_FLUXES #define NOSEDBBL /* define only one of the four following */ #define UV_LOGDRAG #undef MB_BBL #undef SG_BBL #undef SSW_BBL /* define one vertical mixing scheme here*/ #define MY25_MIXING #if defined GLS_MIXING || defined MY25_MIXING # define KANTHA_CLAYSON # define N2S2_HORAVG #endif

/* define bottom and surface fluxes here*/ #define ANA_SSFLUX #define ANA_BSFLUX #define ANA_BPFLUX #define ANA_BTFLUX #define ANA_SPFLUX #define BULK_FLUXES #define LONGWAVE #define EMINUSP /* define open boundary condition here*/ #define WESTERN_WALL #define NORTHERN_WALL #define SOUTHERN_WALL #define RADIATION_2D #define EAST_M3RADIATION #define EAST_M3NUDGING #define EAST_TRADIATION #define EAST_TNUDGING #define SSH_TIDES #define EAST_FSCHAPMAN #define ANA_FSOBC #define UV_TIDES #define EAST_M2FLATHER #define ADD_M2OBC

AdriaROMS System

AdriaROMS operational suite

The forecast cycle is composed by 1 day of hindcast, using short term COSMO-I7 forecast and measured Po river discharge and 3 days of forecast.. The model starts from the previous forecast and no data assimilation is performed.

Skill Assessment of AdriaROMS-1.0

In January 2006, an extensive dataset of CTD measurements has been collected during the cruise done with R/V URANIA (by CNR-ISAC Gruppo di Oceanografia da Satellite, Roma, IT), covering the western part of the Adriatic Sea, and the project DART06 by NRL and NATO URC, in the Southern Adriatic. This dataset has provided the opportunity to assess the quality of the ocean forecasting system. To the same purpose, also AVHRR SST data have been included, as well as available data from buoys or fixed platform.

It can be noted in the figures to the right that model simulated temperature and salinity in the southern Adriatic are lower than observations. The overall bias considering CTD casts in depth exceeding 200 m (offshore region to the south of latitude 42 N) is -1.05 °C and -0.34 PSU, although these bias cancel out on the density field, nearly unbiased, and therefore suggesting good representation of the dynamics. This is associated to the initial heat content (derived by another model, not in situ data) and to the proximity of the boundary, where it was used Clamped type boundary conditions. Using such OBC, when the outer model behaves in a different way, spurious fronts may develop preventing the correct flux of tracers (Blayo and Debreu, 2005). OBCs are now in AdriaROMS -2.0 relaxation-radiation. Another critical region is the coastal current along the western side of the Adriatic, which is a challenging area anyway given its steep gradients. In this region, the (climatological) discharge of major rivers can produce salinity fields substantially different when we are not in typical ‘climatological’ years.

Once biases are removed, amplitude errors and linear association model vs. observations are indeed farily good in particular in the shallower part of the Adriatic (the Northern). This can be argued also by means of the plot to the left, where AdriaROMS has been intercompared also with other operational ocean forecasting systems in the Adriatic (the regional AREG and the large scale MFS, both run by INGV). Profiles are averages of model results (and observations) on all CTD casts in depth not exceeding 50 m during January 2006. Note, in particular in the case of salinity, that AdriaROMS show good linear association and amplitude errors, although with a evident bias throughout the water column. Assessing AdriaROMS-1.0 SST showed that in summer it is usually warmer than AVHRR SST by a mean error of 1°C (July 2005 overall mean, maximum value) and RMSE of 1.5 °C. CTD data in summer 2006 (from DART06 summer cruise) also suggest that AdriaROMS thermocline is often too shallow and not steep enough. In winter instead simulated SST are lower than AVHRR SST by 0.5 °C.

Additional details of the skill score assesssment done for winter 2006 can be foundf in Chiggiato & Oddo (2007). Skill assessment for summer 2006 is in progress. No skill assessment for AdriaROMS-2.0 is yet available.References

Budyko, K., 1974. Climate and life. Academic Press, 508 pp.Blayo E., L. Debreu, 2005. Revisiting open boundary conditions from the point of view of characteristic variables. Ocean Modelling, 9: 231-252.

Chiggiato J. and P. Oddo, 2007. Operational Ocean Models in the Adriatic Sea: a skill score assessment. Ocean Science discussion 3, S808-S804. Currently under revision in Ocean Science. Cushman-Roisin, B., C. E. Naimie, 2002. A 3D finite-element model of the Adriatic tides. Journal of Marine Systems, 37, 279-297.

Fairall, C. W., E. F. Bradley, J. E. Hare, A. A. Grachev, J. B. Edson, 2003. Bulk parameterisations of air-sea fluxes: updates and verification for the COARE algorithm. Journal of Climate, 16: 571-591.Margolin L., P. K. Smolarkiewicz, 1998. Antidiffusive velocities for multipass donor cell. SIAM J. Sci. Comput., 20: 907-929.

Raicich, F., 1996. On the fresh water balance of the Adriatic Sea. Journal of Marine Systems, 9: 305-319.Steppeler J., G. Doms, U. Shatter, H. W. Bitzer, A. Gassmann, U. Damrath, G. Gregoric, 2003. Meso-gamma scale forecasts using the nonhydrostatic model LM. Meteorology and Atmospheric physics, 82:75-96.

AcknowledgmentsThe set-up of AdriaROMS has been possible also thanks to insightful suggestions and various contributions of Richard Signell, John Warner (USGS), Hernan Arango, John Wilkin (Rutgers University). JC would like to thanks in particular RP Signell for the collaboration during Adria0203 project which posed the basis for the development of AdriaROMS system as well as D

Haidvogel along with the full ocean modeling group at Rutgers University for the kind hospitality in 2002. AdriaROMS system has been developed within the framework of the European projects MFTSEP and CADSEALAND and the Italian project MODMET. INGV is acknowledge for making available daily forecast of MSF system.