MAP IOP 15 CASE STUDY

The paper presents the ability of forecasting severe bura events on the Adriatic coast using the ALADIN model operationally used at the Croatian Meteorological Service. Both versions currently in use, the LACE and the Croatian version, as well as the dynamical adaptation of the surface wind field from the latter have been tested on a MAP IOP 15 case. The MAP IOP 15 took place between 5th and 10th November 1999. The strongest bura was recorded around 12 UTC on 7th November. Different versions of the same numerical model have been used on different domains and resolutions. The output surface wind fields from the 8-km resolution Croatian domain have been dynamically adapted to orography with a 2-km resolution, and both results have been compared to the measured data. The latter method proved to be very useful for locations where bura is the most severe, like the Maslenica bridge. The impact of a better representation of orography on the forecasted wind field in the mountainous parts of the coast is visible in the increased spatial variability of the field

SENSITIVITY TO THE INITIAL CONDITIONS – NUMERICAL SIMULATIONS OF THE MAP IOP5 AND MAP IOP15

Numerical simulations of the precipitation system during the MAP IOP5 and the extreme Bura wind case during the MAP IOP15 have been performed with ALADIN/HR (hydrostatic) limited area model. Three experiments were performed. For the reference experiment (ARPE) ARPEGE operational analysis from 1999 were used. The other two experiments (ECAR and ECMW) have the same upper-air fields, from the 4D-Var ECMWF MAP reanalysis. In the experiment ECAR the surface fields were taken from ARPEGE operational surface analysis from 1999. In the ECMW experiment, initial surface fields are taken partly from ECMWF MAP reanalysis and partly from the ARPEGE climatology file for appropriate months. Results of the numerical experiments show the higher sensitivity to the initial conditions for the MAP IOP5 heavy precipitation case. The different initial and boundary conditions for the extreme Bura wind case during the MAP IOP15 have not given significantly different wind field in the corresponding numerical experiments

VERIFICATION OF THE OPERATIONAL 10 M WIND FORECAST OBTAINED WITH THE ALADIN MESOSCALE NUMERICAL WEATHER PREDICTION MODEL

This paper presents the results of the verification of operational 10 m wind forecast obtained with the ALADIN mesoscale numerical weather prediction model. In the period 2010-2012 ALADIN/ALARO 8 km forecasts were initialized daily at 00 UTC and driven with the ARPEGE global model forecasts through the 72-hourly forecasting range. Obtained forecasts were further refined to 2 km grid spacing, using the simplified and cost-effective dynamical adaptation method (ALADIN/DADA 2 km forecasts). Since the primary objective of this study is to assess the efficiency of wind forecast in regions of complex terrain as well as high wind energy potential, eight stations from different wind climate regions of the eastern Adriatic coast were selected to perform the verification procedure. Based on variety of statistical and spectral scores, it is suggested that the wind forecast generally improves with the increase of horizontal resolution. At bora dominated stations, the multiplicative mean systematic error is reduced by more than 50%. The largest portion of root-mean square errors can be attributed to dispersion or phase errors at majority of stations and their contribution increases with model horizontal resolution. Spectral analysis in the wavenumber domain suggests that the slope of kinetic energy spectra of both models decreases from k-3 in the upper troposphere towards ~ k-5/3 near the surface (corresponding to orography spectra) and shows minor seasonal variability. Spectral decomposition of measured and modeled data in the frequency domain indicates a significant improvement in simulating the primary and secondary maximum of spectral power (related to synoptic and diurnal motions) by using the ALADIN/DADA 2 km model, especially for the cross-mountain wind component mostly related to strong and gusty bora flows. Finally, the common feature of both models is a significant underestimation of motions at scales below semi-diurnal, which is a result of their absence in initial conditions and of limited model ability to represent small-scale processes

VERTICAL STRUCTURE OF THE DINARIC ALPS FLOW DURING MAP IOP 15

In this study, a detailed analysis has been undertaken of the Bura flow structure downwind and over the Dinaric Alps on 7 November 1999 during MAP IOP15. Grubišić (2004) used the flight-level data from the coordinated NCAR Electra and NOAA P-3 coast-parallel tracks and cross-mountain tracks by the Electra to document the origin, structure and steadiness of secondary potential vorticity (PV) banners generated by the Dinaric Alps. The observed flow structure is compared here with simulation results from the ALADIN/HR hydrostatic mesoscale model run at the horizontal resolution of 8 km and the 2 km dynamical adaptation. The good agreement between the flight-level data and model simulations provided the basis for the detailed analysis of the evolution and structure of the Bura flow along the entire Adriatic during IOP 15

CHANGES IN THE ALADIN OPERATIONAL SUITE IN CROATIA IN THE PERIOD 2011-2015

National weather services issue weather forecasts based on the output from the numerical weather prediction models. Particular weather phenomena that have significant effect on safety can be characteristic of a certain country or region and may require specific model set-up in terms of model resolution and complexity to be forecast. However, the computational expenses of model set-up for operational purposes are limited by the available computer resources. In Meteorological and Hydrological Service (DHMZ) the operational numerical weather prediction uses ALADIN model. This paper describes the current NWP system and the changes introduced to the operational suite during the last few years. The operational suite in 8 km resolution and the dynamical downscaling of the wind field to 2 km resolution is run with higher frequency, the large scale model that provides the prognostic lateral boundary conditions has changed, operational forecast uses new model version with changes in model physics, dynamics and vertical discretization. Non-hydrostatic set-up of ALADIN has been running in 2 km resolution and 4 km resolution forecast using ALADIN model has been introduced. Here we show that improvements in the model physics that are beneficial for certain weather types, can deteriorate forecast quality otherwise. Although the increase in horizontal and vertical resolution improves the forecast, it partially restores the moist bias in the upper troposphere

OVERVIEW OF METEOROLOGICAL RESEARCH ON THE PROJECT “WEATHER INTELLIGENCE FOR WIND ENERGY” - WILL4WIND

This paper presents an overview of the research results achieved during implementation of the project “Weather Intelligence for Wind Energy” - WILL4WIND (IPA2007/HR/16IPO/001-040507). The overall goal of the WILL4WIND project was to reduce the wind forecast uncertainties in coastal and complex terrain of Croatia in order to support a more efficient integration of wind energy in the national electric system. The paper presents the following key results of applied meteorological research conducted on the project: i) evaluation of wind forecasts showed greater accuracy of the ALADIN/HR model when increasing the model resolution, ii) deterministic forecasting using analogue-ensemble post-processing method noticeably improved numerical weather predictions iii) probabilistic forecasting using analogue-ensemble method provided useful information on the uncertainty of wind predictions, and iv) targeted knowledge diffusion and extensive two-way networking supported identification of the joint research priorities of meteorology and wind energy communities and contributed to development of dedicated software to ease the use of ALADIN/HR forecasts in operational wind energy sector activities. PROJECT was implemented by a Croatian consortium led by Meteorological and Hydrological Service, Croatia, in collaboration with the University of Zagreb Faculty of Electrical Engineering and Computing, Croatian Transmission System Operator Ltd., RP Global Projekti Ltd. and Energy Institute „Hrvoje Požar”. Europen Union co-funded the project through the Science and Innovation Investment Fund within the Instrument for Pre-Accession Assistance (IPA) for Croatia

OPERATIONAL VALIDATION AND VERIFICATION OF ALADIN FORECAST IN METEOROLOGICAL AND HYDROLOGICAL SERVICE OF CROATIA

The numerical forecast using ALADIN model in Meteorological and Hydrological Service of Croatia is run operationally since July 2000. Over the years, various methods of validation and verification of the operational forecast have been applied. The classical methods using root mean square error and mean absolute error would often renalize the high resolution ALADIN when compared to a low resolution global model forecast due to double penalty paradigm. Therefore, the model was mostly evaluated by plotting the forecast and the measurements to allow subjective comparison, especially in weather situations that have high impact on the living and traffic conditions in Croatia. Here we show an overview of validation and verification products created operationally. These products intended for subjective validation in real time can help the forecaster in the decision if to rely on a particular forecast run more or less than to another. Statistical verification scores provide information on model bias and root mean square error but suffer from missing data due to automatic procedures used quality check and filtering of the measured data