Milivoj B. Gavrilov

Geostrophic Adjustment on Hexagonal Grids

A simple two-dimensional linearized model of the atmosphere is used to investigate behavior of the geostrophic adjustment process on five selected horizontal hexagonal grids. This study shows that hexagonal lattices have some advantages over commonly used square grids. Having better isotropy, they provide more accurate dispersion of gravity waves than square grids do, and therefore they can be more appropriate for simulation of smaller-scale divergent processes. The gravity‐inertia wave frequencies of most of the considered grids are also closer to the true solution than those on square grids. However, some hexagonal grids are not completely free of numerical inconsistencies. For example, one of the selected grids generates nonsymmetric roots of the gravity‐inertia solution that may lead to the unwanted simulation of the atmospheric process. The analysis indicates which hexagonal distributions can be an appropriate choice for use in atmospheric and ocean models.

Aridity in Vojvodina, Serbia

For investigating aridity in Vojvodina, two parameters were used: the De Martonne aridity index and the Pinna combinative index. These indices were chosen as the most suitable for the analysis of climate in Vojvodina (a region in northern part of Serbia). Also, these indices were calculated from data obtained from 10 meteorological stations for the period from 1949 to 2006. The spatial distribution of the annual and seasonal De Martonne and the Pinna combinative indices as well as the mean monthly values of the De Martonne index and aridity trends of these indices are presented. There were two, four, and five types of climate on a yearly, seasonal, and monthly basis in Vojvodina, according to the De Martonne climate classification which consists of a total of seven types. In addition, semi-humid and humid climate types were represented in the region, on a yearly basis. The winter season was dominated by wetter types of climate, while the summer season was characterized by drier ones. During the spring and autumn seasons, there were types of climate which range between both aforementioned types. Two out of three climate types, which can be identified using the Pinna combinative index, were registered in Vojvodina region. The most dominant climate type was the semidry Mediterranean with formal Mediterranean vegetation, while the humid type was only identified in one small part of southwestern Vojvodina. The calculated values of both aridity indices showed that there were no annual trends. Therefore, it can be considered that there were no recent aridity changes during the observed period. For paleoclimate, the general story is more complex. The lack of aridity trends in the recent period from 1949 to 2006 supports the fact that Vojvodina has very well preserved loess–palaeosol sequences from the Middle and Late Pleistocene, which indicates that crucial point for their preservation was caused by the weak aridity variability in the region.

Tracing the influence of Mediterranean climate on Southeastern Europe during the past 350,000 years

Loess-palaeosol sequences are valuable archives of past environmental changes. Although regional palaeoclimatic trends and conditions in Southeastern Europe have been inferred from loess sequences, large scale forcing mechanisms responsible for their formation have yet to be determined. Southeastern Europe is a climatically sensitive region, existing under the strong influence of both Mediterranean and continental climates. Establishment of the spatial and temporal evolution and interaction of these climatic areas is essential to understand the mechanisms of loess formation. Here we present high-resolution grain-size, environmental magnetic, spectrophotometric and geochemical data from the Stalać section in the Central Balkans (Serbia) for the past ~350,000 years. The goal of this study is to determine the influence of the Mediterranean climate during this period. Data show that the Central Balkans were under different atmospheric circulation regimes, especially during Marine Isotope Stages 9 and 7, while continental climate prevailed further north. We observe a general weakening of the Mediterranean climate influence with time. Our data suggest that Marine Isotope Stage 5 was the first interglacial in the Central Balkans that had continental climate characteristics. This prominent shift in climatic conditions resulted in unexpectedly warm and humid conditions during the last glacial.

Relating the Astronomical Timescale to the Loess–Paleosol Sequences in Vojvodina, Northern Serbia

In this study the first astronomical time scale for loess-paleosol sequences of Vojvodina region, northern Serbia is presented astronomical timescale for the loess–paleosol sequences of the Vojvodina region, northern Serbia. The sequence is the longest and most detailed orbitally tuned European loess record, comparable to Asian sequences to the east. Magnetic susceptibility (MS) records from two continuous loess–paleosol sequences in Vojvodina have been used to construct the timescale, with the aim of investigating climatic and environmental evolution and variability over the last million years. The 47.3-m-thick Mosorin (MO) section covers the time interval between marine isotope stages (MIS) 1 and 15, while the lower part of the Stari Slankamen (SS) section covers the time frame prior to MIS 16. The MS records were tuned to June 65°N insolation over the period between 0 and approximately 1 million years. The new timescale suggests older than expected ages for a number of the magnetic polarity boundaries, consistent with lock-in depth offsets reported for other loess sequences. Spectral analyses of the stacked MS variations indicate that climatic dynamics are dominated mainly by the changes in orbital eccentricity and subdominantly by obliquity and precession bands, over the past 1 million years.

Influence of Hail Suppression on the Hail Trend in Serbia

The influence of hail suppression by silver iodide seeding on the trend in the number of hail days (hail trend) in the Republic of Serbia was studied in three cases: (1) in Vojvodina region, Northern Province of Serbia, in two periods, from 1967 to 2002 when there was no hail suppression, and from 2003 to 2009 when hail suppression was extended to the entire territory; (2) in Serbia proper (Serbia without the Provinces), in two periods, from 1967 to 1984 when hail suppression was spreading, and from 1985 to 2009 when hail suppression occurred over the entire territory; and (3) in the same period from 1967 to 2002 on the two adjacent territories of Vojvodina and Serbia without the Provinces, where no hail suppression occurred in the first and hail suppression did occur in the second. The hail trend in Serbia was calculated on the basis of all observed data from all synoptic and climatological stations for the period 1967 to 2009. The results associate hail suppression with the stagnation of the hail trend rather than its decrease, and show that hail suppression did not have statistically unique influence on the hail trend.

Classification of natural disasters between the legislation and application: experience of the Republic of Serbia

The paper discusses the definitions of natural disasters and recommends the implementation of definitions and classifications of natural disasters in accordance with those decreed at the Centre for Research on the Epidemiology of Disasters (CRED) and Munich Re insurance Company (Munich RE) for administrative use in the Republic of Serbia. For the Republic of Serbia, the issue of natural disasters is presented both through government documents (e.g. the Law on Emergencies and the National Strategy of the Protection and Rescue in Emergencies) and the survey of the frequency and typology of disasters. Significant discrepancies exist between older and more contemporary classifications of disasters in Serbia. They are especially emphasized in comparison to the CRED and Munich RE classifications and databases. This causes problems in the monitoring, recording and assessment of the effects of natural disasters. It is proposed that definitions be adapted and implemented into legislative and other documents.

Is hail suppression useful in Serbia? – General review and new results

Anthropogenic influence on weather has been increasingly published and discussed in the last decades. Climate changes caused by inadvertent anthropogenic influence are well underway. Hail suppression, which has been proven to have no influence on weather, will be considered in the article. Even though hail suppression as scientifically ungrounded activity seemed to promise certain success several decades ago, it has spread over the whole territory of the Republic of Serbia after abundant experience, when many developed countries have given up on this activity. Reasons will be presented for the senselessness of hail suppression based on the latest research. By processing all hail data from the territory of Serbia in the period from 1967 to 2010, it was found out that the hail trend is rising which is in contrary to expectations and previous claims that hail suppression decreases hail frequency.

Modelling of the Aral and Caspian seas drying out influence to climate and environmental changes

The complete drying out of the Aral and Caspian seas, as isolated continental water bodies, and their potential impact on the climate and environment is examined with numerical simulations. Simulations use the atmospheric general circulation model (ECHAM5) as well as the hydrological discharge (HD) model of the Max-Planck-Institut fur Meteorologie. The dry out is represented by replacing the water surfaces in both of the seas with land surfaces. New land surface elevation is lower, but not lover than 50 m from the present mean sea level. Other parameters in the model remain unchanged. The initial meteorological data is real; starting with January 1, 1989 and lasting until December 31, 1991. The final results were analyzed only for the second, as the first year of simulation was used for the model spinning up. The drying out of both seas leads to an increase in land surface and average monthly air temperature during the summer, and a decrease of land surface and average monthly air temperature during the winter, above the Caspian Sea. The greatest difference in temperature between dry and not dry cases have the same values, about 7–8 °C in both seasons, while daily extremes of temperature are much more pronounced. In the wider local/regional area, close to both seas, drying out leads to a difference in average annual temperatures by about 1 °C. On a global scale, the average annual temperature remains unchanged and the configuration of the isotherms remain unchanged, except for over some of the continents. In winter, Central Asia becomes cooler, while over Australia, southern Africa, and South America, it becomes slightly less warm. Furthermore, a new heat island occurs in western Sahara during summer.

Seasonal prevailing surface winds in Northern Serbia

Seasonal prevailing surface winds are analyzed in the territory of Northern Serbia, using observational data from 12 meteorological stations over several decades. In accordance with the general definition of prevailing wind, two special definitions of this term are used. The seasonal wind roses in 16 directions at each station are analyzed. This study shows that the prevailing winds in Northern Serbia have northwestern and southeastern directions. Circulation weather types over Serbia are presented in order to determine the connections between the synoptic circulations and prevailing surface winds. Three controlling pressure centers, i.e., the Mediterranean cyclone, Siberian high, and the Azores anticyclone, appear as the most important large-scale factors that influence the creation of the prevailing winds over Northern Serbia. Beside the synoptic cause of the prevailing winds, it is noted that the orography of the eastern Balkans has a major influence on the winds from the second quadrant. It was found that the frequencies of circulation weather types are in agreement with those of the prevailing winds over Northern Serbia.

Dispersion Characteristics of Discrete Quasigeostrophic Modes

Abstract Dispersion characteristics of the shallow water quasigeostrophic modes are discussed for the rectangular grids. It is shown that the propagation of the quasigeostrophic modes is affected by the orientation of the semistaggered grids. Also, it is found that the A and E Arakawa grids produce frequencies of the Rossby waves with the wrong sign, that is, positive instead of negative. The B grid gives better propagation of the quasigeostrophic modes than any of the Arakawa grids. Finally, it appears that the B grid has certain advantages over the Z grid.