Alfred Helbig

Observations of supercooling and frazil ice formation in the Laptev Sea coastal polynya

This paper examines a hydrographic response to the wind‐driven coastal polynya activity over the southeastern Laptev Sea shelf for April–May 2008, using a combination of Environmental Satellite (Envisat) advanced synthetic aperture radar (ASAR) and TerraSAR‐X satellite imagery, aerial photography, meteorological data, and SBE‐37 salinity‐temperature‐depth and acoustic Doppler current profiler land‐fast ice edgemoored instruments. When ASAR observed the strongest end‐of‐April polynya event with frazil ice formation, the moored instruments showed maximal acoustical scattering within the surface mixed layer, and the seawater temperatures were either at or 0.02°C below freezing. We also find evidence of the persistent orizontal temperature and salinity gradients across the fast ice edge to have the signature of geostrophic flow adjustment as predicted by polynya models.

Impact of River Discharge and Regional Climatology on the Decay of Sea Ice in the Laptev Sea during Spring and Early Summer

Summer sea-ice conditions in the Laptev Sea are characterized by high interannual variability. The impact of Lena River discharge, one of the Arctics major rivers discharging roughly 525 km3 annually onto the Laptev shelf, and the regional meteorological regime affect the spring and summer ice regime of the Laptev Sea. Using ground and remote-sensing data and statistical analyses, it is shown that river discharge plays an insignificant role in the large-scale decay of the Laptev Sea ice cover. Hydrological and remote sensing data for the period 1979-1990 show that discharge/sea-ice interactions are confined to the coastal regions, with Lena River water flooding a fast-ice belt, roughly 25 km wide, in early to mid-June. Sea-ice decay and summer ice extent are shown to be affected most strongly by dynamic atmospheric forcing and by opening and enlargement of coastal polynyas in early spring.

Impact of river discharge and regional climatology on the decay of sea ice in the Laptev Sea

Summer sea-ice conditions in the Laptev Sea are characterized by high interannual variability. The impact of Lena River discharge, one of the Arctics major rivers discharging roughly 525 km(3) annually onto the Laptev shelf, and the regional meteorological regime affect the spring and summer ice regime of the Laptev Sea. Using ground and remote-sensing data and statistical analyses, it is shown that river discharge plays an insignificant role in the large-scale decay of the Laptev Sea ice cover. Hydrological and remote sensing data for the period 1979-1990 show that discharge/sea-ice interactions are confned to the coastal regions, with Lena River water flooding a fast-ice belt, roughly 25 km wide, in early to mid-June. Sea-ice decay and summer ice extent are shown to be affected most strongly by dynamic atmospheric forcing and by opening and enlargement of coastal polynyas in early spring

Screening and Scenarios of Traffic Emissions at Trier, Germany

Scope and BackgroundIn the course of the European Council Directive on permissible air pollutant limit values, valid starting from 2005 there is an urgent call for action, particularly for fine dust (PM10). Current investigations (Junk & Helbig 2003, Reuter & Baumüller 2003) show that the limit values in certain places in congested areas are exceeded. Only if it is possible to locate these Hot Spots purposeful measures to reduce the ambient air pollution can be conducted. For an efficient identification of these Hot Spots numerical computer models or establishing special measurements networks are too expensive. Using the statistical model STREET 5.0 (KTT 2003) a cost-effective screening of the air pollution situation caused by the traffic can be done.MethodsSTREET is based on the 3-dimensional micro-scale non-hydrostatic flow- and dispersion model MISCAM (Eichhorn 1989). The results of over 100.000 different calculations with MISCAM are stored in a Database and used to calculate the emissions with STREET. In collaboration with the city council of Trier more than 150 streets were investigated, mapped, and calculated. A special urban climate measuring network supplies the necessary meteorological input data about the wind field and precipitation events in the valley of the Moselle. Information about road width and road orientation as well as building density was derived from aerial photographs. Traffic censuses and mobile air pollutants measurements supplied the remaining input data. We calculated the mean annual air pollutant concentrations for NO2, CO, SO2, O3, benzene as well as PM10-.ResultsA comparison of the model results with the values obtained from the stations of the central emission measuring network of Rhineland-Palatinate (ZIMEN, annual report 2002) shows very good agreements. The model was not only used to calculate the annual air pollutant but also for urban planning and management. The absolute level of the air pollutant is mainly dependent on the amount of traffic in the street canyons. Therefore four different case-scenarios with varying quantity of traffic were calculated and interpreted for each street. The results of the calculation show that on the basis of the mean values for both NO2 and benzene, it is not to be expected that the limits will be exceeded significantly.PerspectivesFurthermore the model can be used to find the maximum tolerable numbers of cars for a street without exceeding the air pollutant thresholds.

An observational and modelling analysis of Laptev Sea (Arctic Ocean) ice variations during summer

Abstract In this study we investigate the relationship of the atmospheric circulation and the sea-ice distribution in the Laptev Sea, Arctic Ocean, in the summers 1979−96. Sea-ice data from passive-microwave radiometers, global atmospheric data analyses, cyclone statistics and simulations of the regional climate model HIRHAM4 were analyzed to find out if periods of reduced or increased sea-ice concentrations are linked to synoptic patterns (circulation anomalies, cyclone activity). A canonical correlation analysis between Arctic sea-level pressure and sea-ice concentration anomalies confirms large-scale relationships among these variables. We did not find a simple relationship between sea-ice area anomalies and cyclone activity in the Laptev Sea area

Grundzüge und Ursachen des Stadtklimas

Das mesoskalige klimatische System einer Stadt oder eines Industriegebietes last sich, wie bereits in Kap. 2.3 vorgestellt, als Produkt externer und interner Wechselwirkungen beschreiben. Die internen Wechselwirkungen vollziehen sich uber die Veranderungen der Erdoberflache, uber Eingriffe in den Energiehaushalt und in den Stoffhaushalt der atmospharischen Grenzschicht uber diesen Gebieten.