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Időjárás - Quarterly Journal of the Hungarian Meteorological Service (OMSZ)

Vol. 110, No. 2 * Pages 91–192 * April - June 2006

Quarterly journal of the Hungarian Meteorological Service

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Case study and numerical simulations of the November 19, 2004 severe windstorm in Central Europe
Simon André, Horváth Ákos, Vivoda, J.
idojaras.2006.2.1 (p. 91–)
  |   Abstract

The study analyses the synoptic weather situation and mesoscale impacts of the November 19, 2004 windstorm, which affected several countries of central Europe. Particular attention was paid to the windstorm at the High and Low Tatra regions in Slovakia, where the event showed several attributes of downslope windstorm. This was investigated by using the ALADIN and MM5 numerical models with high horizontal resolution. Effects of the hydrostatic and non-hydrostatic dynamics were compared, as well as the method of the so called dynamical adaptation. It is concluded that downslope windstorms similar to the November 19 case can be forecasted by numerical models of 2.5 km resolution with higher precision than by using the current operational models. Nested version of the MM5 model at 1.0 km indicated possibility of simulation of microscale effects as orographically induced jets. It is shown that computationally effective hydrostatic models based on dynamical adaptation approach can be sufficient in forecasting extreme non-convective wind, similar to the evaluated event. Nevertheless, the results are strongly dependent on the physical parameterization of the model (turbulence, orographic drag, etc.). Hence, future versions of both hydrostatic and non-hydrostatic numerical models should be carefully examined and tested to keep the performance of forecasting severe downslope windstorms.

Developing an optimal system of circulation pattern types for downscaling purposes
Matyasovszky István
idojaras.2006.2.2 (p. 125–)
  |   Abstract

A methodology to develop an optimal system of circulation pattern (CP) types is proposed for downscaling purposes. The success of downscaling depends on how strongly the stochastic behavior of a climate element can be related to CP types. Therefore, an optimal system of CP types has as much information on the specific climate element as possible. The problem includes also the choice of the number of CP types. The procedure proposed is applied to normally distributed daily mean temperatures and daily precipitation amounts having intermittence. In this latter case, CP types may be different for sequences of dry and wet days and for precipitation amounts on wet days.

Relationship between soil texture and near surface climate in Hungary
Drucza Miklós, Ács Ferenc
idojaras.2006.2.3 (p. 135–)
  |   Abstract

The near surface climate of Hungary in the period 1901–1950 is analyzed using a Thornthwaite-based model. Annual and monthly mean values of energy- and water balance components are determined for each Thornthwaite’s climatic region. The analysis is performed for both constant and texture-dependent soil water holding capacity. The main purpose of this study is to evaluate the effect of soil texture on the near surface climate of Hungary. The main findings are as follows: (1) The Thornthwaite-based model is suitable for reproducing the pattern of climate on mesoscale in Hungary; (2) The effect of soil textural characteristics on the mesoscale pattern of climate in Hungary is pronounced. This effect is commensurable with the effects of relief and atmosphere.
The results suggest that Thornthwaite-based models can be applied not only for climate classification purposes but also for purposes of physical and ecological climatology. 

Characteristics and synoptic classification of heavy snowfall events in Budapest for the period 1953–2003 Part II
Hirsch Tamás, Babolcsai György
idojaras.2006.2.4 (p. 155–)
  |   Abstract

In this research, heavy snowfall events (HSEs) in Budapest have been investigated based on a 50-year period. Following the results connected with the main characteristics of HSEs presented in Part I of the paper, the synoptic classification of the cases has been addressed in Part II. Because of the well-known deficiencies of previous synoptic classifications, it was necessary to define our own weather type system. For this purpose, temporally averaged fields of selected meteorological parameters have been used to characterize processes during the whole event, rather than only reflecting the instantaneous state of the atmosphere. In this way, 8 weather types have been defined with quite different characteristics in many aspects. Not surprisingly, most of the HSEs in Budapest have been caused by different types of Mediterranean cyclones. Our classification has also been tested with the help of case studies taken from an independent winter period (2005/2006). Our results show that synoptic-scale processes are strongly connected to heavy precipitation in winter, and that synoptic climatological investigations covering long periods are very useful for operational weather prediction.

Estimating global radiation using the meteorological input data of crop models
Fodor Nándor
idojaras.2006.2.5 (p. 175–)
  |   Abstract

Although not measured at many meteorological stations, the daily global radiation at the earth’s surface is a very important component of ecosystem mass and energy processes and so it is in crop modeling. The lack of radiation data is a limitation to the use of crop models. The original and an improved form — that takes precipitation data into account — of the Bristow-Campbell solar radiation estimation method were investigated regarding their performance for providing radiation estimates as crop model input. While the original method did not gave acceptable radiation estimations for the used crop model, the improved method did. With an additional site specific calibration, the new method gave so good radiation estimates that the average errors of simulated yield and cumulative evapotranspiration could be decreased below 2% and 0.5%, respectively.

Comparison of values of the chosen meteorological fields measured at the aerological stations and the values taken from NCEP/NCAR Reanalysis
Woyciechowska, J., Bqkowski, R.
idojaras.2006.2.6 (p. 183–)
  |   Abstract

Statistical relationship between the air temperature and the geopotential height of the pressure levels measured at the air-sounding station in Poland and taken from NCEP/NCAR Reanalysis for the same location was analyzed, based on data from the 30-year period of 1974–2003. It was shown, that NCEP/NCAR Reanalysis data is fully complementary and valuable data series, particularly in the lower and middle troposphere, and it can be used along with direct measurements (meteorological sounding of the atmosphere).

IDŐJÁRÁS - Quarterly Journal