Information and dissemination of data

The capacity of meteorological modelling to limited areas targeted to agrometeorological forecasting operating in the MiPAF environment

Andrea Buzzi
Institute for Atmospheric and Climate Science (ISAC- National Research Council, Bologne)

The activity currently conducted within of the Ministry for Agricultural and Forestry Policies (MiPAF) in the sector of meteorological modelling, is aimed at forecasting the parameters of agrometeorological interest in national territory for up to three days. It is based on simulation and procedures codes, which developed for about ten years, require substantial updating and advancement to keep pace with the growing demands of quality and detail of meteorological forecast, bringing technical/scientific improvements from research and available resources in numerical calculations.

The forecasting activity could be improved considering, in particular, the progresses which intervened in the last years in terms of intrinsic quality and potential spatial resolution of the input into the limited area modelling (provided by the European Centre for Medium-Range Weather Forecasts at Reading, [ECMWF]); the considerable increase in the capability of available calculation; and, above all, the improvement of techniques of meteorological modelling brought from research in the sector. Such techniques have improved in terms of major efficiency of numerical methods of integration of models and of great accuracy in describing the complexity of the physical processes that intervene in meteorological evolution.

International research in these last years has been aimed at improving mesoscale models, the means of describing meteorological phenomena that have spatial scales at, or less than, a few kilometres, for example, the natural convective rainfall system or the circulation system induced from orography. New systems have been or are still at the moment under elaboration that explicitly describe the microphysical processes of formation and transformations of various hydrometeors that characterize the water cycle in the atmosphere. They also describe the processes of interchange with terrestrial surfaces, taking account of the effects of vegetation and soil properties. At the same time, there are improved numerical techniques, such as the advection systems of temporal integration and of nesting. Nesting aims at obtaining high spatial resolutions over restricted areas.

The scope of this research topic is to introduce substantial advances in quality and detail of short-term weather forecasting on the national territory. It is aimed at agricultural applications, permitting in particular an improvement in the forecasting of meteorological parameters at the soil level (maximum and minimum temperature, wind, rainfall, humidity, radiation), making best use of data supplied by ECMWF. We attempt to pursue this aim by getting new modelling instruments ready that allow for improving the various stages of the operative chain and to function at spatial resolutions that are at least double the current ones.

The main aspects of the three-year research concern the following:
  • Updating of the procedures for working out and assimilating input data in order to take advantage of the increase of resolutions of ECMWF available analyses and forecasts. Currently in DALAM (Data Assimilation Limited Area Model), ECMWF fields are used at the standard pressure level and with a horizontal resolution of 0.5x0.5 degrees. The developments offered should permit the use of original hybrid levels (up until now the ECMWF model uses 60 levels) and with spatial resolutions that can be of the nominal order (today of about 40 km).
  • Development of an advanced system for calculating the energy balance and the water surface balance that can take into account soil topography and vegetative cover, in order to improve the forecasting of parameters at soil level and of rainfall. Such a system is intended to improve the description of flux of heat and humidity, to permit a refinement of the modelling at the superficial layer in function of the characteristics of land surface and of under the soil, up until some metres of depth.
  • Implementation of a more efficient system of temporal integration, in particular as regards integration of components of gravity into the equation of movement and the advection terms. We will then define a new grid of rotated geographical coordinates that minimize anisotropy of the grid.
  • Implementation and validation of a rainfall flowchart based on an explicit coverage of the microphysical processes of clouds at intermediate complexity, adapted, that is, to operating models of resolution that is lower than cloud models. The system is based on the explicit treatment of five different types of hydrometeors (water and ice of clouds, rain, snow, graupel/hail) in order to improve the description of the hydrological cycle in the atmosphere.
  • Implementation and validation of a system of convection adapted to the mesoscale models that permit the interaction with the explicit microphysical system , through an interchange of a hydrometeor. The Kain-Fritsch system will be used.
  • Improvement of the current system of superficial turbulent diffusion and in the boundary layer, either over the sea or over the land.
  • Study and implementation of simultaneous “nesting” techniques, in order to achieve large spatial resolutions of particular interest with better calculating efficiency. The validation phases will be fulfilled on a basis of carrying out case tests of forecasting, always comparing the results with those obtained from the current DALAM model and with the observed data at one’s disposal. Further, a validation on the extended period is planned , especially in order to fine-tune the soil model.

  • Acquisition of necessary data for the project (both data of meteorological analyses and physiography);
  • Development and validation of new initialisation procedure;
  • Updating of the dynamic system , development of a microphysical system.

  • First formulation of the model of the exchanges between soil and atmosphere;
  • Validation of the modifications to the system of temporal integration;
  • Complete implementation and validation of the complete hydrological cycle (explicit microphysics and convection);
  • Implementation of the system of treatment of the turbulent exchanges

  • Completing and validating the soil system ;
  • Validating of new system of the surface turbulent diffusion and of the boundary layer;
  • Implementing the technique of simultaneous nesting;
  • Perfecting the complete updated version of the model.

  • Updating of the procedures of elaboration and assimilation of the input data, which is currently used to refer to a limited number of the atmospheric levels defined at constant pressure. For a more adequate use of the original resolution permitted from ECMWF products, which is necessary to set up an accurate forecast at high resolution, it is required to use the greatest possible number of vertical levels, with “hybrid” coordinates in which the meteorological fields in the ECMWF models are defined. We would also take into account the variations of the sizes and available fields studied intervening during this time. To this end, it seems necessary to revise the treatment of data of surface and of soil level. We will carry out a general revision of the code, which defines the set of input data of the initial conditions and those at the edge of the integration area.
  • Development of an advanced system for calculating energy balance and superficial water balance that takes into account physiography of the soil and land cover. This system will improve predictions of the local meteorological variables at the ground level (air temperature at two metres and at the soil level, including maximum and minimum; humidity of air and water content of the soil; wind at 10 metres) as well as that of rainfall, in particular, that of convection. It is necessary to introduce data on the physical characteristics of the soil and its possible vegetation. It is expected, therefore, to elaborate an exchange model of energy and mass between the atmosphere and the soil that takes into account spatial and seasonal variability of the soil and of the characteristics of the vegetation. This part of the research, directly relevant to the agrometereological aspects, will develop in strict collaboration with Central Office of Crop Ecology (UCEA). In the course of the first year, the choice of physical model and of the processes to implement, a partial formulation of the system (above all regarding the part not pertinent to vegetation) and the acquisition of a necessary set of data are expected.
  • Development of more efficient systems of temporal integration and definition of a new grid system in rotated geographical coordinates. The high horizontal (to roughly 15-5 km of grid distance in the configuration with nesting) and the vertical (40-50 levels) resolutions, necessary for a more accurate description of rainfall, require improved calculation efficiency and treatment of gravity waves. However, the current semi-implicit system will be substituted by a “split-explicit”, which permits both a consistent reduction of processing time and of memory use. The rotation of the grid permits a final increase of the temporal step avoiding the accumulation of points toward the poles. Finally, the advection system will be implemented through the “forward-backward” technique of Malguzzi and Tartaglione (1999).

The most innovative aspects of the research are:
  • The use of data to a high resolution as input from a global model;
  • The development of an exchange model between the atmosphere and the soil;
  • The use of original techniques of temporal integration;
  • The implementation of “microphysics” at the intermediate level of parametrization;
  • The development and use of advanced nesting techniques.

The main technico-scientific effects regard the sector of modelling the geophysical fluids applied to meteorological forecasting . Experiences in the sector in Italy are limited and recently formed. This research provides the opportunity to avoid dispersing the acquired expertise and to maintain a national competitiveness in the sector. In addition, this research, as a result of the updated techniques come international research will become more functional. The accuracy of predictions and high resolution targeted to agrometeorology will improve.

The socio-economical effects are those derived from improvements in the forecasting capabilities of the meteorological models in terms of an increase of accuracy and local specificity of the prediction of meteorological parameters that are of notable interest for agriculture. Among such parameters there are, for example, maximum and minimum temperature, wind, and humidity at the soil level, as well as accumulated rainfall. There is also expected to be an increase in the capacity of forecasting of adverse effects in agriculture. From a more accurate forecast of one to three days than is currently available, with a high spatial resolution according also to soil types, positive economic impacts are expected due to the timely dissemination of agrometeorological information at the national level. In fact, one should recall that the estimated increase of production due to a better understanding of climatic factors is about 5 percent.

  • Kain, J.S. & J.M. Fritsch. 1993: Convective parameterization for mesoscale models: The Kain-Fritsch scheme. The Representation of Cumulus in numerical models, Meteor. Monogr., 46, Amer. Meteor., Soc., 165-177.
  • Malguzzi, P. & Tartaglione, N. 1999: An economical second order advection scheme for explicit numerical weather prediction. Quart. J. Roy. Meteor. Soc., 125, 2291-2303.


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