N. I. Kolev, P. B. Savov, E. H. Donev, D. I. Ivanov, A. P. Blagoev, B. K. Kaprielov, V. N. Grigorieva, V. C. Danchovski, I. N. Kolev – Atmospheric boundary layer and surface ozone concentration study over Sofia area by lidar and ozonemeter.
Abstract. The ecological problems caused by the increasing ozone concentration are not easy to be solved because ozone is not directly emitted by certain sources but its concentration is defined by numerous dynamical and chemical processes. Stratosphere-troposphere exchange and subsequent ozone penetration into the boundary layer define the contribution of so-called “natural” ozone to ozone pollution near the ground. The purpose of this research is the studying of the surface ozone concentration behavior during the period of the destruction of stable boundary layer and residual layer and the formation of convective boundary layer, so as the influence of the temperature, the relative humidity and the height of the mixing layer as well as that of the formation of mixing layer in different areas of Sofia, Bulgaria to be determined. The surface ozone concentration in the area of the Institute of Electronics changes synchronously with the development of the mixing layer. The maximum values of the surface ozone concentration are being reached when the height of the mixing layer reached its maximum and afterwards. The maximum growth of the surface ozone concentration is around 11-12:30h local standard time when a fast growth of the mixing layer begins and the complete destruction of the residual layer is observed, i.e. the two processes of mixing layer growing and entrainment of aerosol and ozone from the higher layers of atmosphere boundary layer are observed. The values of the surface ozone concentration during summer months are higher than those during fall.

A. Deleva – Lidar monitoring of Saharan dust transport over the city of Sofia in the period 2006-2008

Abstract. Desert dust aerosols are the most abundant and massive type aerosol particles that are present in the atmosphere. One environmental consequence of atmospheric dust loadings is their significance for climate through a range of possible influences and mechanisms. In this work results from three years long lidar monitoring of Saharan dust transportation over the city of Sofia are presented. Remote atmospheric investigations are carried out at the second Nd:YAG laser wavelength in the period 2006-2008. Vertical profiles of the aerosol backscatter coefficient are processed and analyzed. The mass temporal evolution and the spatial distribution of the registered desert dust layers are illustrated by 2D-colormaps in height-time coordinates. The observations described here are in good agreement with the forecasts of Barcelona Supercomputing Centre, concerning Saharan dust transport to Europe.

A. Deleva, A. Slesar, S. Denisov – Investigations of the aerosol fields and clouds in the troposphere with Raman-aerosol lidar
Abstract. In this work we present experimental results from regular laser remote investigations of tropospheric aerosols and clouds. Computed vertical profiles of the aerosol backscattered coefficient are included and analyzed. The temporal evolution and the spatial distribution of the observed atmospheric layers are visualized by 2Dcolormaps in height-time coordinates. The measurements were performed by a new three-channel lidar developed in the Laser Radar Lab, Institute of Electronics. The light source in the lidar is a powerful Q-switched frequency-doubled Nd:YAG laser (output pulse power: 1 J at 1064 nm; 100 mJ at 532 nm; pulse duration 15 ns FWHM; repetition rate 2 Hz). The backscattering radiation from the atmosphere is collected by means of a big Cassegrain-type telescope (35 cm diameter, 200 cm focal length). The wavelength spectral separator consists of two aerosol channels and one Ramanchannel. A simple, fast, and efficient receiving system is based on newly developed high sensitivity photo-receiving modules with very compact design and reliable operation. The acquisition system is provided with specialized software, well adapted to different lidar tasks, allowing for performing comfortable detection, conversion, and processing of lidar data. The good parameters of all the laser, telescope, photoreceiving modules and software make it possible for the developed lidar to be utilized for carrying out fast and accurate long-range remote atmospheric measurements with high spatial and temporal resolution. The presented results illustrate the abilities of the lidar for monitoring of the aerosol fields and clouds in the troposphere and low stratosphere.casts of Barcelona Supercomputing Centre, concerning Saharan dust transport to Europe.

N. Gromkova, I. Butchvarov – Applying the model for transformation of the annual climatic wind rose in the air pollution modeling from point source
Abstract. The necessity to transform the standard (for Bulgaria) climatic 8-point wind roses, named Observed Wind Roses here (OWR), appears in connection with the determination of the climatic (annual mean) air pollution concentration field from a point source, that is the purpose of most Environmental Impact Assessments. Using an 8-point wind rose for calculating the pollution by existing applied models – a Gaussian plume model for a continuous point source, the concentration isopleths follow the 8 compass directions of the wind rose and it seems that between them there is no pollution. A more adequate qualitative concentration field should be obtained by using a better-described wind rose at a given place, defined in more compass directions. The development of a simple algorithm for the transformation of the OWR, in the general case, defined in n-point to m-point, where n > m or vice versa n < m, is the purpose of the present paper. The new rose will be named Transformed Wind Rose (TWR).

I. Butchvarov, N. Gromkova – Algorithm for transformation of wind rose by increasing or decreasing of compass directions
Abstract. The necessity to transform the standard (for Bulgaria) climatic 8-point wind roses, named Observed Wind Roses (OWR), was described in previous paper of the authors – Gromkova at al. The algorithm of calculation of the so-called Primitive Wind Rose (PWR) and further on the Transformed Wind Rose (TWR) in different number of compass directions then 8 is the purpose of the present paper.

M. Syrakova – Outliers in the seasonal and annual temperature series on the territory of Bulgaria in the period 1900-2000
Abstract. The mean seasonal and annual temperature series at 31 stations, representative for the lowlands of Bulgaria, are checked for outliers, i.e. for observations very distant from the mean value. The data cover the period 1900-2000. Winter outliers are only negative, spring outliers are only positive. Summer, autumn and annual outliers are both positive and negative with dominance of positive outliers in summer and negative outliers in autumn. The magnitudes of the negative outliers reach grater absolute values than those of the positive outliers. The number and frequency of the outliers, except for some cases in the series, are greater in the first half of 20th century.

E. Marekova – Statistical modeling of space-time distribution for earthquakes in various seismic regions (in Bulgarian)
Abstract. Two different cases of declustered series of earthquakes from six different seismic regions and aftershock series of several strong contemporary earthquakes were investigated. The main aim of the research was to describe by means of mathematical functions the distances and time intervals distributions between the subsequent pairs of events. The mathematical models were compared with other model distributions, derived at defined initial conditions. Based on the comparison between the observed and model distributions of the series of declustered events, a conclusion may be made that the examined earthquakes series are independent. Analogous investigation of the aftershock series show the events clustering in the frames of certain investigated sequences

I. Cholakov, S. Mihovski – Magnetic repeat station survey of Bulgaria in 2007 and 2008
Abstract. During the summer months of 2007 and 2008 seven repeat stations and seven first class stations were measured in the eastern Bulgaria. The magnetic declination and inclination were determined by a DI-flux (theodolite Zeiss 020B and Mag-01H) while the total intensity was measured by a proton magnetometer PMP-5A. The geographic azimuths were determined by GPS. The observations were reduced by the diurnal variations of the geomagnetic field taken from the geomagnetic field records in the Panagyurishte geomagnetic observatory. The results are reduced to the epochs 2007.0 and 2008.0. Maps of the geomagnetic declination for the same epochs were drawn, as the measured points from the geomagnetic survey 1978-1980 were used as well.

E. Botev, R. Glavcheva, I.Popova, B. Babachkova, S. Velichkova, I. Tzoncheva, S. Dimitrova, G.Georgieva – Data and analysis of the events recorded by NOTSSI in 2006
Abstract. A map of epicenters of 1424 earthquakes that occurred in the Balkan Peninsula sector outlined by latitude j =370-470N and longitude l=190-300E is presented. Expert generalized analysis of the seismicity over the territory of Bulgaria and its very adjacent lands (with more than 620 localized events) is proposed. Catalog of earthquakes with magnitude M>2.5 is applied.

E. Botev, R. Glavcheva, I.Popova, B. Babachkova, S. Velichkova, I. Tzoncheva, S. Dimitrova, G.Georgieva – Data and analysis of the events recorded by NOTSSI in 2007
Abstract. A map of epicenters of 1152 earthquakes that occurred in the Balkan Peninsula sector outlined by latitude j =370-470N and longitude l=190-300E is presented. Expert generalized analysis of the seismicity over the territory of Bulgaria and its very adjacent lands (with more than 810 localized events) is proposed. Catalog of earthquakes with magnitude M>2.5 is applied.

N. Miloshev – Earthquakes – risk and reaction