Papers by Stjepan Ivatek-Sahdan
International Convention on Information and Communication Technology, Electronics and Microelectronics, Sep 2, 2011
Operational and research numerical weather prediction applications in the Meteorological and Hydr... more Operational and research numerical weather prediction applications in the Meteorological and Hydrological Service of Croatia. B. Ivančan-Picek * , K. Horvath * , S. Ivatek-Šahdan * , M. Tudor * , A. Bajić * , I. Stiperski * and A. Stanešić *. ...
Pageoph topical volumes, 2019
The accurate modelling of sea surface gravity waves is essential for accurate oceanic forecasting... more The accurate modelling of sea surface gravity waves is essential for accurate oceanic forecasting with high sea waves being a major concern for navigation and coastal activities. It is also very important for oceanic modelling, with the wave input being key to the accurate modelling of oceanic surface stress, sediment resuspension, and also to oceanic current modelling. In the Croatian Meteorological Institute, we have implemented the Wind Wave Model III as an operational model. The wind forcing used is based on the numerical weather prediction model ALADIN/ HR. The model uses near-surface winds dynamically adapted to 2 km grid spacing over the 3-day forecast range. The boundary condition at the Otranto Strait is obtained from the WAM model forecasts computed at ECMWF. The model setup uses an unstructured grid to make the forecasts. The numerical modellization uses an implicit scheme that we describe. We found an underestimate of significant wave height by 8 cm, an absolute error of 21 cm and a correlation of 91% on comparing with the altimeter of the SARAL satellite. Comparison with wave radar and buoys show no underestimate and smaller absolute errors.
In the European Union, less-favoured area (LFA) for agriculture is an area with natural handicaps... more In the European Union, less-favoured area (LFA) for agriculture is an area with natural handicaps (lack of water, unfavourable climate, short crop season and tendencies of depopulation), or that is mountainous or hilly, as defined by its altitude and slope. LFAs benefit from area and headage compensatory allowances, and from a number of payments for structural adjustment, so it is a National governments obligation and interest to designate their respective LFAs. Croatia, as a new member of the European Union, prepared detailed analysis of orographic features, climatic conditions, soil characteristics and specific handicaps that induce negative affects to agricultural and rural development. Bio-physical climatic constraints and specific handicaps are analysed and presented here in details. Length of growing season defined by low air temperature and heat stress defined by high air temperature have been selected climatic parameters affecting the agriculture. The specific constraints in Croatia included strong wind and fire danger on the coast and hail inland. This work was initiated and lead by the Ministry of Agriculture while the analysis presented here was conducted in Meteorological and Hydrological Service of Croatia.
Hrvatski meteorološki časopis, 2005
In this study, a detailed analysis has been undertaken of the Bura flow structure downwind and ov... more 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.
ANEMOALARM-iskustva operativne primjene prognoze smjera i brzine vjetra Sažetak: Državni hidromet... more ANEMOALARM-iskustva operativne primjene prognoze smjera i brzine vjetra Sažetak: Državni hidrometeorološki zavod (DHMZ) i µm-meteorološki sustavi u suradnji s Hrvatskim cestama razvili su program za upravljanje prometom s obzirom na opasnost za vozila zbog jakog vjetra nazvan ANEMOALARM. Program je u DHMZ-u operativan od rujna 2007.godine. Ovaj rad daje prikaz dosadašnjih iskustava s radom programa na području od Prizne do Lokvina, s posebnim osvrtom na usporedbu mjerenih i prognoziranih vrijednosti brzine vjetra. Prva zima testnog korištenja pokazala je da program veoma dobro prognozira situacije s vjetrom jačine opasne po sigurnost prometa. Međutim, sigurno je potrebno dalje praćenje rada ovog sustava kako bi se povećala njegova pouzdanost. 1 mr. sc. Alica Bajić mr. sc. Stjepan Ivatek-Šahdan Zvonko Žibrat, dipl. ing.
Dravni hidrometeoroloki zavod (DHMZ) i µm-meteoroloki sustavi u suradnji s Hrvatskim cestama r... more Dravni hidrometeoroloki zavod (DHMZ) i µm-meteoroloki sustavi u suradnji s Hrvatskim cestama razvili su program za upravljanje prometom s obzirom na opasnost za vozila zbog jakog vjetra nazvan ANEMOALARM. Program je u DHMZ-u operativan od rujna 2007.godine. Ovaj ...
Hrvatski meteorološki časopis, 2015
This paper presents the results of the verification of operational 10 m wind forecast obtained wi... more 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.
6th HyMeX workshop 7-10 May 2012, 2012
EMS Annual Meeting Abstracts, Vol.11 / EMS (ur.). - EMS, 2014. EMS2014-484., 2014
The numerical forecast using ALADIN model in Meteorological and Hydrological Service of Croatia i... more 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 penalize 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.
ii) Traditional scores, wind roses, histograms... For reliable wind resource estimates, the globa... more ii) Traditional scores, wind roses, histograms... For reliable wind resource estimates, the global model reanalysis data needs to be downscaled to provide information for regional interpretation. This is especially true in complex terrain of Croatia, where a significant portion of wind energy potential is related to phenomena arising from the non-linear dynamical interaction of the high, steep mountains and the troposphere, such as cross-mountain Bora and along-mountain “Jugo” wind (channeled Sirocco).
The paper presents the ability of forecasting severe bura events on the Adriatic coast using the ... more 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 are 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 are used on different domains and resolutions. The output surface wind fields from the 8-km resolution Croatian domain are dynamically adapted to orography with a 2-km resolution, and both results are compared to the measured data. The latter method proved to be very useful for locations where the 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 visibl...
U ovom radu analizirana je vremenska situacija za vrijeme dva sumska požara na poluotoku Peljescu... more U ovom radu analizirana je vremenska situacija za vrijeme dva sumska požara na poluotoku Peljescu. Požari su podmetnuti u noci s 20. na 21. srpanj 2015. Cilj je rada prouciti situaciju koja je uz ljudski cimbenik dovela do pocetka požara, te provjeriti kakvu su prognozu davali modeli WRF i ALADIN/HR u dane požara i koliko se ta prognoza dobro slagala s izmjerenim podacima. Analiziran je mjesec srpanj u klimatskom smislu za Ploce u razdoblju 1981.-2014. Analizirani podaci pokazali su da je srpanj 2015. bio topliji od visegodisnjeg prosjeka, a oborina je izostala. U srpnju je bilo 30 vrucih dana sto je dvostruko vise od prosjeka. Izostanak oborine i ekstremno topao srpanj pridonjeli su tome da dođe do najgoreg moguceg požara, požara krosnji. Vrijeme je bilo pretežno vedro, na sam dan izbijanja požara temperatura je dostizala vrijednosti 39 °C, a i iducih se dana maksimalna temperatura nije spustala ispod 30 °C na Peljescu. Relativna vlažnost zraka tijekom dana najcesce je iznosila oko...
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Papers by Stjepan Ivatek-Sahdan