•Exceptional Bora event of winter 2012 over the northern Adriatic is investigated.•NWP model (BOLAM–MOLOCH) simulations are validated and discussed.•Near-surface meteorological variables, SST and ...surface fluxes are analyzed.•SST initialization strongly impacts surface fluxes prediction.•Possible model improvements are identified.
The Bora wind event occurred in winter 2012 was exceptional in terms of both meteorological effects and impact on the Adriatic Sea circulation. It was associated with intense and persistent winds, very cold temperatures all over the Mediterranean basin and heavy snowfall over the Apennines slopes exposed to north-easterly winds, and it was responsible for triggering dense water formation and driving basin-scale oceanic circulation. The cooling period (29 January–13 February) was characterized by intense air–sea exchanges of momentum and heat, whose accurate simulation is required for a proper description of atmospheric and ocean circulations.
In the present study, results of a number of short-range high-resolution numerical weather prediction (NWP) model simulations for the entire Bora outbreak are discussed. The modeling chain, based on BOLAM and MOLOCH limited area models, has been implemented using initial and boundary conditions provided by different global NWP systems. Model performance has been evaluated in terms of variables of interest for oceanographic applications, such as sea surface temperature (SST), surface heat fluxes, solar radiation and near surface meteorological parameters (air temperature, wind, pressure and humidity). The validation has been undertaken through a comparison against surface data (buoys and oceanographic platforms) available at different locations in the northern Adriatic area, while advanced synthetic aperture radar (ASAR) products have been used to assess modeled wind fields on a larger scale.
Model results indicate a good agreement with the observations concerning meteorological variables, in particular wind, pressure and temperature. However, large differences were found in the SST forecasts, which in turn affect also sea surface flux predictions. The uncertainties in SST forecasts are mainly ascribable to the different initialization fields provided by either the global models or satellite analyses. Thus SST initialization represents a critical issue for an accurate description of surface fluxes at least for this exceptionally severe event.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The oceanographic forecast capability in coastal seas is often limited by the capacity of the numerical models in correctly reproducing the complex morphology of the coastline and the exchange ...processes between the shelf and the open seas. In the marginal Adriatic Sea this task is of uppermost importance due to the presence of several coastal water bodies and rivers. We present here a new operational oceanographic system, called Tiresias, based on the unstructured grid model SHYFEM and representing the whole Adriatic Sea together with the lagoons of Marano-Grado, Venice and Po Delta. The novelty of this oceanographic system resides in the very high-resolution, up to 10 m, of the numerical mesh, and in the high spatial and temporal resolution of the forcing and boundary conditions that drive the forecasts. The forecast results are evaluated against sea temperature and salinity profiles, mean circulation fields derived from a regional ocean model, tide gauges and drifter trajectory. The presented results highlighted the capacity of Tiresias in forecasting the general circulation in the Adriatic Sea, as well as several relevant coastal dynamics, such as saltwater intrusion, storm surge and riverine waters dispersion.
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Results of the assimilation of high-density data to initialize the high-resolution meteorological model MOLOCH (CNR-ISAC) are described. The local analysis and prediction system (LAPS), a mesoscale ...data assimilation system developed at NOAA, is applied to modeling a case study of heavy precipitation that occurred over Liguria, north-western Italy, on November 4, 2011, causing severe flood in the city of Genoa. This case is representative of some episodes that affected the region in the last few years, where the coastal orography, besides enhancing the convective uplift, contributed to the formation of convergence lines over the sea, responsible for the onset of convective cells. The present work aims at the implementation of a model-based operational short-range prediction system, with particular focus on quantitative precipitation forecasting in a time range up to 12-24 h. The use of LAPS analysis as initial condition for the MOLOCH model shows a positive impact on the intensity and distribution of the simulated precipitation with respect to the simulations where only large-scale analyses are employed as initial conditions. Effects on the models simulations are due to the assimilation of surface network data, radio-sounding profiles, radar and satellite (SEVIRI/MSG) data.
We introduce the latest version of the RegCM regional climate modeling system, RegCM5. Compared to the previous model version (RegCM4) the main new development is the inclusion of the non‐hydrostatic ...dynamical core from the weather prediction model MOLOCH, which is more accurate and much more computationally stable and efficient than the previous one. In particular, the new dynamical core is best designed for use at convection‐permitting resolutions of a few km. Several physics schemes and coupled model components have also been upgraded compared to the previous version of the model. A set of test simulations for present day climate conditions at parameterized convection and convection permitting resolutions over different European domains is presented for illustrative purposes. Overall, for these simulations RegCM5 exhibits a better performance than RegCM4 for the majority of statistics analyzed, especially at convection‐permitting resolutions. However, this performance depends on the physics schemes used, and further optimization work is under way to fully test the model in different climate settings and reduce current biases. RegCM5 is a freely available, computationally efficient, flexible, and portable Regional Earth System model designed for community use, so that prospective model users are welcome to access its code and use it for different applications.
Plain Language Summary
We introduce the latest version of the RegCM regional climate modeling system, RegCM5, in which the main new development, in addition to some physics upgrades, is the inclusion of the non‐hydrostatic dynamical core from the weather prediction model MOLOCH. This makes the model more accurate and much more computationally efficient than the previous version, especially at convection‐permitting resolutions of a few km. A set of test simulations for present day climate conditions at parameterized convection and convection permitting resolutions over different European domains is presented for illustrative purposes. Overall, these simulations show that RegCM5 mostly exhibits a better performance than RegCM4 for most statistics analyzed, especially at convection‐permitting resolutions, although this performance depends on the physics schemes used. Further optimization work is under way to fully test the model in different climate settings and reduce current biases. RegCM5 is a freely available, computationally efficient, flexible, and portable Regional Earth System model designed for community use, so that prospective model users are welcome to access its code and use it for different applications.
Key Points
The fifth version of the regional climate modeling system RegCM, has been developed and released
Illustrative experiments show that the model overall performs better and is much more computationally efficient than the previous version
The model is a community resource so that prospective users are encouraged to access it and use it
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A nudging procedure for the assimilation of rainfall data into a mesoscale model the Bologna Limited Area Model (BOLAM) has been developed in order to improve short-range forecasting. The scheme ...modifies the model specific humidity profiles at every time step, according to the difference between observed and forecast precipitation. Different relaxation procedures are applied depending on the precipitation type (large-scale or convective rain), as estimated by the model itself. Optimizations of the nudging parameters and assessment of the scheme's performance was carried out in an idealized framework (Observing System Simulation Experiment) OSSE-type strategy, implementing a lagged forecast scheme. Two events were selected for this purpose, both characterized by heavy precipitation in the Mediterranean Basin. The first was a severe orographic rainfall event, associated with the passage of a frontal system over the Alps during the Mesoscale Alpine Programme (MAP) field phase, in September 1999. The second was characterized by the development of a very deep low close to the Algerian coast, where heavy precipitation caused a disastrous flood in the city of Algiers in November 2001. The effects of rainfall assimilation were evaluated, both qualitatively and quantitatively, in terms of precipitation forecasts and modification of dynamical fields, with particular attention to the impact on cyclone development. Finally, sensitivity tests were performed in order to assess the dependence of the nudging procedure on rainfall data characteristics (length of the accumulation period and associated error) and model error. PUBLICATION ABSTRACT
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MAP D-PHASE Rotach, Mathias W.; Ambrosetti, Paolo; Ament, Felix ...
Bulletin of the American Meteorological Society,
09/2009, Volume:
90, Issue:
9
Journal Article
Peer reviewed
Open access
Demonstration of probabilistic hydrological and atmospheric simulation of flood events in the Alpine region (D-PHASE) is made by the Forecast Demonstration Project in connection with the Mesoscale ...Alpine Programme (MAP). Its focus lies in the end-to-end flood forecasting in a mountainous region such as the Alps and surrounding lower ranges. Its scope ranges from radar observations and atmospheric and hydrological modeling to the decision making by the civil protection agents. More than 30 atmospheric high-resolution deterministic and probabilistic models coupled to some seven hydrological models in various combinations provided real-time online information. This information was available for many different catchments across the Alps over a demonstration period of 6 months in summer/ fall 2007. The Web-based exchange platform additionally contained nowcasting information from various operational services and feedback channels for the forecasters and end users. D-PHASE applications include objective model verification and intercomparison, the assessment of (subjective) end user feedback, and evaluation of the overall gain from the coupling of the various components in the end-to-end forecasting system.
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Four satellite rain estimations based on microwave (MW), infrared (IR) or combined MW-IR techniques are compared with the BOlogna Limited Area Model (BOLAM) rain forecast for a severe weather event ...(8–13 November 2001) over the western Mediterranean Sea. Two of the investigated multi-channel MW rainfall algorithms use data from the Tropical Rainfall Measuring Mission (TRMM). The Frequency Difference Algorithm relies on data from the TRMM Microwave Imager (TMI) and the other one combines data from the Precipitation Radar (PR) with those from the nine-channel radiometer TMI, called PR Adjusted TMI Estimations of Rainfall (PATER) algorithm. The pure IR Rain Estimator uses geostationary IR METEOSAT data and the combined Naval Research Laboratory algorithm uses both MW data from low orbiting satellites and IR data from the geostationary orbit. Validation results, computed over a common grid, which is independent of the different field of view sizes of the applied data sets, indicate that there is generally a better performance for heavy rain (> 6 mm h−1) than for light rain (<1 mm h−1). Both MW algorithms perform rather similarly, although PATER shows some rain detection problems due to thick aerosol loads originating from the desert. The BOLAM model presents a good agreement with the MW and only a minor location error of a heavy rain area was detected. Both IR-based algorithms have problems in identifying the correct rainy areas compared to MW. Overall, the results suggest that there are advantages in combining both techniques – the well-known rain physics of the MW channels with the high temporal resolution of IR algorithms – to retrieve precipitation from satellite data.
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