Wednesday 27 October 2021

July - September 2021


Quarterly Joournal of the Hungarian Meteorological Service

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Basics of the atmospheric energetics: A brief summary of global and regional atmospheric energetics reflected upon the university curricula
Réka Ágnes Dávid and Péter Tasnádi
 PDF (1374 KB)   |   Abstract

The purpose of this study is to provide an overview of the science and development of atmospheric energetics, its so far matured parts to date, and the direction of the researches. However, we restrict ourselves to the discussion of the very basic results of the researches to reveal the parts the introduction of which can be suggested into the compulsory education of the future meteorologist. This became feasible especially due to the rapid development of the personal computer that makes possible the calculation of the atmospheric energies for students by using their own laptops, so this field of meteorology now can be a tactile reality for them. The founder of atmospheric energetics was Lorenz, who formulated for a global, dry atmosphere the concept of available potential energy, which is the difference between the current energy state of the atmosphere and a reference state with minimum energy. His basic results concerning the global description of atmospheric energetics have already become part of the university curriculum. It is important to be able to describe the energy balance of the atmosphere both locally as well as globally, for which the introduction of enthalpy and exergy seemed appropriate. The advantage of examining the dry atmosphere is that significant simplifications can be applied, but the atmosphere is finally moist, so research has also started in this direction, first with a global and then with a local approach. The key is to find the reference state, which is a complex, computationally demanding task. In this paper, we focus on the most important steps of this process and concentrate on the thermodynamic basis of the new concepts.


Validation of subgrid scale ensemble precipitation forecasts based on the ECMWF’s ecPoint Rainfall project
Boglárka Tóth and István Ihász
 PDF (2195 KB)   |   Abstract

Nowadays, state-of-the-art numerical weather prediction models successfully predict the general weather characteristics several days ahead, but forecasting extreme precipitation is quite challenging even in the short time range. In the framework of the ecPoint Project, the European Centre for Medium-Range Weather Forecasts (ECMWF) developed a new innovative probabilistic post-processing tool which produces 4-day precipitation forecast as accurate as the raw ensemble forecast at day 1. In the framework of the scientific co-operation between ECMWF and the Hungarian Meteorological Service (OMSZ), we were invited to participate in the validation of the experimental products. Quasi operational post-processed products have been available since July 1, 2018. During our work, besides using different verification technics, a new ensemble meteogram was also developed which can support operational forecasters during extreme precipitation events. As a result of our work, products of the ecPoint Project have been included in the operational forecasting activity.


Evapotranspiration estimation at the Kis-Balaton wetland
Angela Anda, László Menyhárt, and Brigitta Simon
 PDF (800 KB)   |   Abstract

Evapotranspiration rate, ETaand vegetation composition strongly influence the water budget of wetland impacting available water and water resource management. One of the goals of this study was to estimate the areal ETa of the Kis-Balaton wetland, KBW (natural ecosystem) between 1997 and 2012. This time period was free of any human intervention. ETa was accounted for different vegetation classes through the multiplication of the reference evapotranspiration, ET0 by previously determined crop coefficients in each vegetation/open water classes. Besides common reed and cattail, five other groups were separated, including open water as an independent class. The evapotranspiration sums were strongly impacted by annual mean air temperature, Ta. One degree increment in annual average Ta will increase the yearly ETa sums in about 100 mm. The yearly areal ETaof KBW ranged from 737.08 mm to 896.63 mm with an average of 802.07 mm during the 16-year study.


Analysis of heating and cooling periods in Budapest using station data
Csenge Dian, Attila Talamon, Rita Pongrácz, and Judit Bartholy
 PDF (3278 KB)   |   Abstract

The built environment has a very complex role in cities. On the one hand, various urban climatological phenomena are caused and influenced by buildings (e.g., urban heat island effect, local wind conditions, air pollution). On the other hand, buildings are important contributors to energy use via heating and cooling, e.g. they account for about 40% of total energy consumption on average in Europe. Daily average outdoor temperature is taken into account to design the heating and cooling systems of residential, commercial, or office buildings. That is why we analyzed the available temperature time series of the capital of Hungary, Budapest for the period between 1901 and 2019. The aims of this study are (i) to investigate the changes in temperature data series that influence building energy design parameters, (ii) to analyze the heating and cooling periods in the last 119 years based on different definitions, and (iii) to define a third (transitional) period between the heating and cooling periods. Based on the results, it can be concluded that the variability of warm days is smaller than that of cold days, consequently, the optimal design of heating systems is a greater challenge compared to cooling systems. Furthermore, the length of the temperature-based heating period decreased substantially, while the length of the cooling period increased as a consequence of overall regional warming.


Influence of climate change on river discharges over the Sava River watershed in Bosnia and Herzegovina
Slobodan Gnjato, Tatjana Popov, Dragutin Adžić, Marko Ivanišević, Goran Trbić, and Davorin Bajić
 PDF (1571 KB)   |   Abstract

The paper examines changes in air temperature, precipitation, and river discharges on seasonal and annual scale over the Sava River watershed in Bosnia & Herzegovina during the period 1961–2016. Based upon data gathered from 11 meteorological stations and 3 hydrological stations, hydroclimatic variables trends were established by utilizing the nonparametric Mann-Kendall test and the nonparametric Sen’s slope estimator. The results show significant positive seasonal and annual trends (expect for autumn, during which upward trends were insignificant) in air temperature, whereas both positive and negative insignificant seasonal and annual precipitation trends are shown where determined for the entire watershed. Most prominent upward trends in air temperature were found in summer and afterwards in winter and spring, indicating a pronounced warming tendency over the Sava River watershed. Trends in river discharge displayed a negative tendency in all seasons. Nevertheless, a majority of estimated trends of river discharges were weak and statistically insignificant. Throughout the year, river discharges showed significant positive correlation with precipitation, whilst connection with air temperature was mostly significant and negative. The study results suggest that climate is an important factor affecting river regimes, as well as that changes in river discharges are reflecting recent abrupt changes in climatic variables.


Impact of meteorological drought on vegetation in non-irrigated lands
Tahereh Sadat Mirmohammadhosseini, Seyed Abbas Hosseini, Bagher Ghermezcheshmeh, and Ahmad Sharafati
 PDF (990 KB)   |   Abstract

Drought is a natural phenomenon that causes a lot of damages annually in various sectors, including agriculture and natural resources. The aim of this study is to evaluate the influence of meteorological drought index on vegetation index. For this purpose, the standard precipitation index (SPI) as a meteorological drought index is calculated using the precipitation data of 28 meteorological stations located on the area of Lorestane province, Iran, during the years 1987–2017. Then, the vegetation condition index (VCI) is computed using normalized difference vegetation index (NDVI) images that obtained from MODIS images of Terra satellite during 2000–2017. Dry, normal, and wet years were obtained based on the SPI results for 2008, 2013, and 2016, respectively. SPI and VCI were correlated using Pearson's correlation method. The results of the relationship between VCI and SPI showed that the highest Pearson correlation coefficient related to 9-month SPI in November was equal to 0.64. Multivariate linear regression was also performed between SPI and VCI, and the results showed that SPI was significantly correlated with VCI at 5% level over a period of 9 and 12 months. Finally, a confusion matrix was used to evaluate the compliance of the SPI and VCI drought classes. Results showed that the VCI had the highest compliance in the moderate drought class with SPI.


Spatiotemporal distribution of heavy and extreme snowfalls in the Transcarpathian region
Ruslan Ozymko, Alina Semerhei-Chumachenko, and Vasyl Manivchuk
 PDF (7431 KB)   |   Abstract

This paper presents a spatiotemporal analysis of the dynamics of heavy and extreme snowfalls in the Transcarpathian region during 1990-2019. Data on snowfalls are obtained from the observation points of the state hydrometeorological network of the Transcarpathian Regional Center of Hydrometeorology. Also there are data included from the Pozhezhevska snow avalanche station (Ivano-Frankivsk region) as a representative observation point for the highland zone of the eastern part of the Transcarpathian region. The analysis took into account the date of snowfall, the amount of precipitation that fell during the snowfall,l and its duration. The recurrence of different indicators of snowfall distribution was calculated for each observation point separately for the specified thirty-year period. Some results were mapped by the isolines using kriging interpolation. Spatio-temporal heterogeneities and regularities in the distribution of heavy and extreme snowfalls have been revealed.


Downscaling diurnal temperature over west and southwest Iran: A comparison of statistical downscaling approaches
Mohammad Reza Poodineh
 PDF (1969 KB)   |   Abstract

This study aimed to forecast temperature variations in the western and southwestern part of Iran using a general circulation model and artificial neural networks (ANN). The data included mean diurnal temperatures from synoptic stations, National Centers for Environmental Prediction/ National Center for Atmospheric Research (NCEP/NCAR) reanalysis data, and outputs of a third-generation global climate model, the Hadley Centre Coupled Model version 3 (HadCM3), under A2 and B2 scenarios for the baseline period (1961–1990). The data of the first (1961–1975) and second 15 years (1976–1990) of the baseline period were used for model calibration and validation, respectively. Both models, however, produced reliable estimates at the plain stations with neither outperforming the other due to their negligible errors. However, the neural network results of mountain synoptic stations showed a lower error rate than the statistical downscaling model (SDSM) outputs. All in all, we can say that there was a larger amount of error in the outputs of the atmospheric general circulation models (AGCMs) in the mountainous regions. According to the outputs of the neural network and the AGCMs, temperatures at the studied stations were on the rise. In fact, this increase was more noticeable at the plain stations. This can be attributed to their proximity to the sea, to their latitude, and to the more intensive industrial activities (especially, extraction of petroleum and production of petroleum products) taking place near the plain stations.


On the correction of processed historical rainfall data of siphoned rainfall recorders (Short Contribution)
Tibor Rácz
 PDF (612 KB)   |   Abstract

Historical rainfall data registered by siphoned rainfall recorder (SRW) devices have been widely used for a long time in rainfall intensity investigations. A relatively known counting error of the SRW devices is the siphoning error, when the registration of rainfall is blocked temporarily, during the drainage of measure tank. This issue causes a systematic underestimation in the rainfall and rainfall intensity measurement results. To reduce its consequences, a data correction is crucial when SRW data are used, for example as a reference for climate comparison studies, or for proceeding of intensity-duration-frequency curves, etc.  In this paper, a formula is presented to fix the siphonage error of SRW devices for historical rainfall data. The early measures were processed in a significant percentage of cases, and sometimes the original measurement results (registration ribbon) have been lost. An essential advantage of the presented formula is that it can be applied for these processed data, which show only the intensity of a known length time interval. For this correction, the average rainfall intensity and the length of the time window are needed, over the physical parameters of the SRW device. The data correction can provide a fixed value of the rainfall intensity, which is undoubtedly closer to the real average rainfall intensity. The importance of this formula is in the reprocessing and validation of the historical rainfall intensity data, measured by siphoned rainfall recorders.