Papers by Ekaterina Batchvarova
Theoretical and Applied Climatology, 2005
Summary The Basel UrBan Boundary Layer Experiment (BUBBLE) was a year-long experimental effort to... more Summary The Basel UrBan Boundary Layer Experiment (BUBBLE) was a year-long experimental effort to investigate in detail the boundary layer structure in the City of Basel, Switzerland. At several sites over different surface types (urban, sub-urban and rural reference) towers up to at least twice the main obstacle height provided turbulence observations at many levels. In addition, a Wind Profiler
Proceedings of the 18th International Congress of Biometeorology, Tokyo Japan, 22-26 September 2008.
Theoretical and Applied Climatology, 2006
The present study addresses recent achievements in better representation of the urban area struct... more The present study addresses recent achievements in better representation of the urban area structure in meteorology and dispersion parameterisations. The setup and main outcome of several recent dispersion experiments in urban areas and their use in model validation are discussed. The maximum concentrations generally are predicted within a factor of two by the best models. If the plume is released down in a closely-packed set of obstacles, it is necessary to account for initial spread. If the plume is released above the obstacles, there is less of an initial spread. For roof level releases (the BUBBLE Tracer Experiment) the horizontal spread of the plume corresponds to a Lagrangian time scale bigger than the value for ground sources. Turbulence measurements up to 3-5 times the building height are needed for direct use in dispersion calculations.
Boreal Environment Research …, 2009
A budget method to derive the regional surface flux of CO 2 from the evolution of the boundary la... more A budget method to derive the regional surface flux of CO 2 from the evolution of the boundary layer is presented and applied. The necessary input for the method can be deduced from a combination of vertical profile measurements of CO 2 concentrations by i.e. an airplane, successive radio-soundings and standard measurements of the CO 2 concentration near the ground. The method was used to derive the regional flux of CO 2 over an agricultural site at Zealand in Denmark during an experiment on 12-13 June 2006. The regional fluxes of CO 2 represent a combination of agricultural and forest surface conditions. It was found that the regional flux of CO 2 in broad terms follows the behavior of the flux of CO 2 at the agricultural (grassland) and the deciduous forest station. The regional flux is comparable not only in size but also in the diurnal (daytime) cycle of CO 2 fluxes at the two stations.
Die Bewertung und Vorhersage der thermischen Umweltbedingungen des Menschen in einer physiologisc... more Die Bewertung und Vorhersage der thermischen Umweltbedingungen des Menschen in einer physiologisch korrekten, wirkungsvollen und praktischen Weise stellt eine der wichtigsten Fragestellungen in der Human-Biometeorologie dar. Dies ergibt sich aus der Notwendigkeit, den Wärmehaushalt des Menschen den thermischen Umweltbedingungen anzupassen, um Gesundheit, Wohlbefinden und Leistungsfähigkeit zu gewährleisten. Vor diesem Hintergrund wurde vor mehr als 3 Dekaden im DWD das Klima-Michel-Modell KMM entwickelt, das die damals ausführlich publizierte Behaglichkeitsgleichung (PMV Predicted Mean Vote) von Fanger (1970) mit einem Strahlungsmodell zur Berechnung der mittleren Strahlungstemperatur verknüpfte und damit die Anwendbarkeit der PMV-Gleichung auf die Bewertung der thermischen Bedingungen im Freien erreichte. Später wurde von Staiger et al. (1997) zwecks leichterer Verständlichkeit der KMM-Ergebnisse ein Äquivalenztemperatur-Ansatz hinzugefügt, womit der Begriff der sehr populär gewordenen "Gefühlten Temperatur" geboren wurde. Eine Verbesserung der physiologischen Relevanz des PMV unter warm-feuchten Bedingungen wurde auf der Grundlage der Arbeit von von Staiger (VDI, 2008) durchgeführt. Das Klima-Michel-Modell blieb über mehr als zwei Jahrzehnte weltweit das einzige thermische Bewertungsverfahren für Außenbedingungen mit integriertem Strahlungsmodell und es stellt noch das aktuelle Standardverfahren des DWD dar. Es wird hier u.a. angewendet zur Vorhersage (COSMO-LM, Hitzewarndienst), Klimaanalyse (Synop-Daten), Stadtklima (UBIKLIM), Kurortklimadienst, Klimawirkungsforschung (ECHAM, CLM) einschließlich der Analyse von Mortalitätsdaten.
Proceedings 18th Int. Congress Biometeorology ICB, 2008
One of the fundamental issues in human biometeorology is the assessment and forecast of the therm... more One of the fundamental issues in human biometeorology is the assessment and forecast of the thermal environment in a sound, effective and practical way. This is due to the need for human beings to adapt their heat budget to the thermal environment in order to optimise comfort, performance and health.
International Journal of Environment and Pollution, 2001
ABSTRACT Measurements from Northern Finland on radiation and turbulent fluxes over a sparse borea... more ABSTRACT Measurements from Northern Finland on radiation and turbulent fluxes over a sparse boreal forest with snow-covered ground were analysed. The measurements represent harsh winter conditions characterised by low sun angles. The absorption of incoming solar radiation in clear skies (turbidity) was found to be a strong function of the solar elevation. At low solar elevation angles, commonly used expressions for turbidity did not fit the measurements well. A simple energy balance type met-processor performed well during daytime, but it was not satisfactory during night time. Simplifications and possible improvements in the energy balance model are discussed.
A parameterization of the wind profile for the entire boundary layer is formulated, with emphasis... more A parameterization of the wind profile for the entire boundary layer is formulated, with emphasis on the lowest 200 - 300 m and considering only wind speeds above 3 m s-1 at 10 m height. The friction velocity is taken to decrease linearly through the boundary layer. The wind profile length scale is composed of three component length scales. In the surface layer the first length scale is taken to increase linearly with height with a stability correction following Monin-Obukhov similarity. Above the surface layer the second length scale becomes independent of height but not of stability, and at the top of the boundary layer the third length scale is assumed to be negligible. A simple model for the combined length scale that controls the wind profile and its stability dependence is formulated by inverse summation. The wind profile for a number of stability classes, based on the Monin-Obukhov stability scale, , is illustrated in Figs 1 and 2. () MBL L
In today's operational atmospheric dispersion models, the meteorological fields are often taken f... more In today's operational atmospheric dispersion models, the meteorological fields are often taken from routinely available weather forecasts. Such forecasts are based on simulations with Numerical Weather Prediction models (NWP). Typical output from a NWP model consists of coarse hourly profiles of wind, temperature and humidity on a rough horizontal grid. The height of the boundary layer does not form a part of the output from the NWP model, but has to be estimated from the available output data, usually by use of bulk Richardson numbers, that vary in their definition. As much emphasis has been devoted to estimate the connection between the critical Richardson number and the NWP output for land conditions, the Richardson methods generally are considered to make reliable predictions of the boundary-layer height over land. Based on measurements the ability from NWP model output to predict the height of the marine boundary layer is studied. It is found that the predicted boundary-layer height in general is too large which suggests that for the marine boundary layer the critical Richardson numbers are smaller than over land -we found critical Richardson numbers around 0.03 to 0.05 to perform best over the sea. Furthermore it is found that a relatively small neighbouring island can influence development of the boundary layer height.
Deeply and in many ways climate affects mankind and human activities. Air temperature and humidit... more Deeply and in many ways climate affects mankind and human activities. Air temperature and humidity, surface wind and radiation balance components are the major parameters of the atmospheric environment determining the bioclimatic conditions, which are one of the important features of the urban environment. Citizens of most European countries have perceived the winter 2005-2006 as exceptional long and cold. At the same time the summer 2006 in Finland was exceptionally warm and dry and the summer of 2007 in Bulgaria was characterized by prolonged heat waves. The aim of presented work is to analyze the human comfort conditions in Sofia and Helsinki during the winter period 2005-2006 and summer 2006. As a tool for assessment of the level of human comfort/discomfort conditions the new wind chill (WCI) and PET indexes have been used. The diurnal variability and the features of thermal comfort have been analyzed. The hourly air temperature, wind speed and relative humidity from the automat...
− mgm ). The drastically increased number of second hand cars imported into the country during th... more − mgm ). The drastically increased number of second hand cars imported into the country during the last few years has contributed to significantly high concentrations of nitrogen dioxide in major Bulgarian cities. 2. Main objectives The main objective for the Bulgarian participants will be to contribute to the improvement of urban boundary layer parameterization schemes, with regard especially to the wind speed and wind direction, and the mixing height. Part of the work will be comparison of previous and new proposed schemes, their validation against urban data sets and their possible implementation in a meteorological preprocessor. We are also interested in gaining knowledge and exchange of information in application-oriented modeling techniques for the atmospheric dynamics and the dispersion of pollutants in cities with complex terrain.
Analysis of meteorological measurements from tall masts in a rural as well as an urban area shows... more Analysis of meteorological measurements from tall masts in a rural as well as an urban area shows that the height of the boundary layer influences the wind profile even in the lowest hundreds of meters. A parameterization of the wind profile for the entire boundary layer is formulated with emphasis on the lowest 200-300 meters. Input to the wind profile parameterisation requires - in addition to the usual surface layer scaling parameters such as friction velocity, roughness length and the Obukhov stability scale - the boundary layer height and baroclinicity. The baroclinicy controls the gradient of the wind profile at the top of the boundary layer and influences the wind profile even inside the boundary layer. Additionally the influence on the wind profile of the Brunt-Vaisala frequency above the boundary layer is introduced. A length scale is introduced for the entire boundary layer, and its dependence on surface roughness, boundary layer height and baroclinicity is discussed.
1] A new objective method for the determination of the atmospheric boundary layer (ABL) depth usi... more 1] A new objective method for the determination of the atmospheric boundary layer (ABL) depth using routine vertically pointing aerosol lidar measurements is presented. A geophysical process-based analysis is introduced to improve the attribution of the lidar-derived aerosol gradients, which is so far the most challenging part in any gradient-based technique. Using micrometeorological measurements of Obukhov length scale, both early morning and evening transition periods are determined which help separate the turbulence regimes during well-mixed convective ABL and nocturnal/stable ABL. The lidar-derived aerosol backscatter signal intensity is used to determine the hourly-averaged vertical profiles of variance of the fluctuations of particle backscatter signal providing the location of maximum turbulent mixing within the ABL; thus, obtained mean ABL depth guides the attribution by searching for the appropriate minimum of the gradients. An empirical classification of the ABL stratification patterns into three different types is proposed by determining the changes in the near-surface stability scenarios. First results using the lidar observations obtained between March and July in 2011 at SIRTA atmospheric observatory near Palaiseau (Paris suburb) in France demonstrate that the new attribution technique makes the lidar estimations of ABL depth more physically reliable under a wide spectrum of meteorological conditions. While comparing lidar and nearby radiosonde measurements of ABL depths, an excellent concordance was found with a correlation coefficient of 0.968 and 0.927 for daytime and nighttime measurements, respectively. A brief climatology of the characteristics of the ABL depth, its diurnal cycle, a detailed discussion of the morning and evening transitions are presented.
Wind lidar measurements of mean wind speed profiles are com-pared to WRF model simulations (Skama... more Wind lidar measurements of mean wind speed profiles are com-pared to WRF model simulations (Skamarock et al., 2008) up to 600 m at a flat coastal site. Two 15-day periods in the autumn of 2010 are modelled using 2 different planetary boundary layer (PBL) schemes (MYNN and YSU) and 2 different vertical resolu-tions. In general the modelled profiles are less sheared than ob-served, which results in an under estimation of the wind speed higher up in the PBL. Both models are not able to reproduce low-level jets satisfactory, which introduces a bias for stable condi-tions.
A Scintec MFAS sodar is in operation since summer 2008 at Ahtopol meteorological observatory (Bul... more A Scintec MFAS sodar is in operation since summer 2008 at Ahtopol meteorological observatory (Bulgarian Black Sea coast) allowing climatological records of the wind profile up to 400 – 600 m height. The simultaneous turbulence observations with ultrasonic anemometers form unique for Bulgaria basis for studies of the structure of the coastal boundary layer. The monitoring will develop further to cover temperature and humidity profiles, ozone and aerosol concentrations, as the site is suitable for atmospheric composition background observations.
Continuous sodar (Scintec MFAS) and ultrasonic anemometer (Typhoon – Obninsk make) measurements w... more Continuous sodar (Scintec MFAS) and ultrasonic anemometer (Typhoon – Obninsk make) measurements were initiated in summer 2008 at the meteorological observatory of Ahtopol at the Black Sea coast (south-east Bulgaria) under a Bulgarian-Russian collaborative programme. These observations of high resolution form the basis for studies of the atmospheric boundary layer turbulence and vertical structure at a coastal site. This sodar is unique in Bulgaria and provides the first continuous high resolution data on the wind profile up to 400 – 500 m above the ground. In addition, the continuous turbulence parameters monitoring allows atmospheric boundary studies needed for different applications. The meteorological observatory at Ahtopol is under development as a background atmospheric composition station in coastal area and the wind data are essential for the studies of gases exchange under breeze conditions. The measurements revealed quite different sea breeze seasons during the years 2008 t...
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Papers by Ekaterina Batchvarova