D. M. Ivanov, D. G. Lazarov, A. P. Blagoev, V. C. Danchovski, E. H. Donev and Bo L.B. Wiman – A seventy nine day’s time-series of Black sea coastal ozone, aerosol, and meteorological parameters: statistical interrelationships, and implications

Abstract. This paper applies a variety of statistical methods for exploring relationships between time series of ground-level ozone concentrations, aerosols (in terms of number-concentrations of particles larger than 0.5 μm) and meteorological parameters. The time sequences were obtained automatically and simultaneously (records of the every hour averages) at a coastal station near Ahtopol in Bulgaria for
the period May 10 – July 27, 2002. Introductory statistical analyses suggested a number of potential interrelationships between ozone concentration variations and some meteorological parameters. There were also indications of aerosol-particle concentrations showing some connections with wind speed and wind direction, and also with solar radiation; the latter relationship however likely to be a result of the partly radiation-driven pattern for wind speed and direction. These introductory findings warranted the use also of Mathematical Spectral Analysis (MSA) in analysing the time series, so as to show the usefulness of MSA for meteorological applications. The conclusions based on the power spectra, the cross-amplitude spectrum, the absolute coherency spectrum and the phase spectrum are confirmed by the diurnal cycles. The power spectrum of the observed data as well as the cross-amplitude, absolute coherency and phase spectra were calculated for hourly meteorological parameters, aerosols and ozone data. The present article contains the calculations of the spectra and their interpretation. Among conclusions is that diurnal variations of meteorological parameters well explain diurnal variation of ozone concentrations, but that the daily aerosol concentrations variations are less affected by diurnal variability of meteorological parameters except solar radiation.

A. Brandiyska, R. Mitzeva, B. Tsenova – A new non-inductive thunderstorm electrification scheme in RAMS atmospheric model

Abstract. A new scheme of non-inductive thunderstorm electrification is developed, imbedded in the bulk microphysical scheme of RAMS v.6.0. The charge separation mechanisms use the rime accretion rate (RAR) approach (Brooks et al., 1997) and are based on the laboratory experiments of Takahashi (1978) and Saunders and colleagues (Saunders et al., 1991). A new type of hybrid scheme is tested, based on the assumption that the laboratory experiments of Saunders et al. (1991) (one-chamber) represent the charging in regions with weak mixing, while the experiments of Takahashi (1978) (two-chambers) represent the charging in regions with strong mixing. Numerical simulations of a typical thundercloud (CCOPE, 19 July 1981) indicate that the proposed hybrid scheme is capable to reproduce the basic charge structure of the storm in general agreement with observations.

V. C. Danchovski, D. M. Ivanov, A. P. Blagoev, E. H. Donev – Parameterization and verification of soil water potential microclimatic model. Case study at Sofia and Plana stations

Abstract. The purpose of present work is to model the behavior of soil water potential (SWP). The model is constructed as a nonlinear combination of precipitation and evapotranspiration (ET). It is designed and tested with simulations of SWP with a time step of one hour. Investigation is done over data from two stations located in Borisova Garden, Sofia and Plana Mountain area for a period over one year. Verification is performed over obtained and actually measured values at both meteorological stations. It is concluded that the model adequately describes the course of SWP except in periods of drought where some deviation from measured data is observed. The designed mathematical model can be used as a tool for simulations of local soil water potential and hence for periods for which SWP values are not measured. Also SWP is important parameter controlling ozone flow through the stomata of the leaves and can be used to assess the risk of damage of vegetation caused by ground-level ozone.

L. Dimitrova, S. Nikolova – Ambient seismic noise at broadband seismic stations of Bulgarian national digital seismic network (BNDSN)

Abstract. The main goal of this study is to evaluate ambient seismic noise at the Bulgarian National Digital Seismic Network (BNDSN) stations equipped with new broadband seismometers. In order to compare the performance of the network against international standards a detail analysis of the noise was performed using method and software that are applied in the international practice. To estimate the distribution of power spectral density (PSD) of the noise over the wide frequency band probability density function (PDF) was calculated. Annual, frequency, seasonal and diurnal analyses were performed. The levels of the ambient seismic noise were determined and the full range of the factors influencing the quality of the data and the performance of a seismic station were analyzed. The estimated PSD functions were compared against two global models (NHNM and NLNM) for high and respectively low noise levels. The results show that estimated PSDes fall within NLNM and NHNM for all of the BNDSN stations and the Bulgarian seismic stations belong to the medium noise level stations worldwide. It has been shown in the study that the seismic noise analysis is very useful tool for evaluation performance of the BNDSN seismic broadband stations.

L.Christoskov, L.Dimitrova, D.Solakov – Digital broadband seismometers of NOTSSI for practical magnitude determinations of p waves

Abstract. The paper aims to define an appropriate magnitude calibration function and station corrections of PV (PVS) wave for broadband (BB) instruments of the National Operative Telemetric System for Seismological Information (NOTSSI). The calibration function is defined by an adaptive treatment of the existing calibration function for the short period seismometers. The existing magnitude station corrections are reconsidered in level and the corrections for the new broadband stations are determined. The values of the adapted calibration function and the new set of station corrections have to be considered as a necessary step for realization of practical comparative proof of NOTSSI magnitude determinations regarding the assessments of the international seismological centres as EMSC, NEIC or ISC.

E.Botev, I.Popova, B.Babachkova, S.Velichkova, I.Tzoncheva, S.Dimitrova, L.Dimitrova – Data and analysis of the events recorded by NOTSSI in 2008

Abstract. A map of epicentres of 1775 earthquakes that occurred in the Balkan Peninsula sector outlined by latitude φ =370- 470N and longitude λ=190-300E is presented. Expert generalized analysis of the seismicity over the territory of Bulgaria and its very adjacent lands (with more than 1070 localized events) is proposed. Catalog of earthquakes with magnitude M>2.5 is applied.

E.Botev, I.Popova, B.Babachkova, S.Velichkova, I.Tzoncheva, S.Dimitrova, L.Dimitrova – Data and analysis of the events recorded by NOTSSI in 2009

Abstract. A map of epicentres of 2744 earthquakes that occurred in and around of the central part of Balkan Peninsula (sector outlined by latitude φ =370- 470N and longitude λ=190-300E) during 2009 is presented. Expert generalized analysis of the seismicity over the territory of Bulgaria and its very adjacent lands (with 2017 localized events) is proposed. Catalog of earthquakes with magnitude M>3.0 is applied.

E.Botev, I.Popova, B.Babachkova, S.Velichkova, I.Tzoncheva, S.Dimitrova, L.Dimitrova

Abstract. A map of epicentres of 2401 earthquakes that occurred during 2010 in the Balkan Peninsula (sector outlined by latitude φ =370- 470N and longitude λ=190-300E) is presented. Expert generalized analysis of the seismicity over the territory of Bulgaria and its very adjacent lands (with more then 1600 localized events) is proposed. Catalog of earthquakes with magnitude M>2.5 is applied.

P. Trifonova, M. Metodiev., I. Cholakov, I. Radev

Abstract. Although the modern electronic devices are used as a primary direction indicators for aircrafts, magnetic compasses remain important back-up systems on airplanes. Airports infrastructure must include special sites which allow an aircraft check to be performed, and to calibrate onboard compasses. There are certain requirements towards those sites and the most important one is the geomagnetic declination homogeneity. The present paper describes methodology and results of the geomagnetic survey performed at the Sofia airport investigating the suitability of the north deicing pad to be used as a calibration site for aircraft compass systems. The total intensity of the geomagnetic field and geomagnetic declination were measured and analyzed. As a result, major magnetic disturbers were delineated and the suitable for compass calibration area was determined.