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

POST-PROCESSING OF ALADIN WIND SPEED PREDICTIONS WITH AN ANALOG-BASED METHOD

In this paper, different post-processing methods are described and evaluated for deterministic and probabilistic point-based 10-m wind speed forecast over Croatia. These methods are applied to forecasts of operational high-resolution dynamical adaptation model (DADA) run with 2 km horizontal resolution to address the following question: which point-based post-processing method is the best suited for wind forecasting in the operational suite at DHMZ (Meteorological and Hydrological Service of Croatia). The verification procedure includes several metrics computed considering wind speed as continuous, categorical and probabilistic predictand. Those metrics were used to optimize the configuration, and to test both the deterministic and probabilistic prediction performance. This study shows that deterministic analog-based predictions (AnEn) improve the correlation between predictions and measurements while reducing forecast error better than using Kalman filter based predictions (KF), even though KF shows better bias reduction. The best results are achieved when forecasting the mean of analog ensemble or the Kalman filter of the mean of analog ensemble. Probabilistic AnEn predictions are properly dispersive, while having better resolution, discrimination and skill than forecast generated via logistic regression. These results encourage the potential use of AnEn in an operational environment at the location of meteorological stations, as well as at wind farm s

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

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

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

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