Changes in snow cover occurrence in five central european stations during the second half of the 20th century

Ponencia presentada en: VI Congreso Internacional de la Asociación Española de Climatología celebrado en Tarragona del 8 al 11 de octubre de 2008.[EN]Changes in snow cover occurrence in central Europe during the second half of the 20th century were investigated. Five stations were taken into consideration. Most of the stations represent central European lowlands and one is placed in the Alpine foreland. Data concerning daily snow cover depth from winters 1950/51-1999/2000 was used. Linear trends show negative changes in the number of days with snow cover in all lowland stations. Trends are statistically significant at the 0.05 level only in two stations (Hamburg and Giessen), where absolute changes reach about -4 days per 10 years. Weak positive changes were found in the Alpine foreland. Changes in the maximum snow cover depth were analysed at the same way and again, negative tendencies were found in lowland stations, statistically significant only in Giessen and Vienna.[ES]El objetivo de este trabajo es analizar los cambios experimentados por la cobertura nivosa en Europa Central durante la segunda mitad del siglo XX. Se han utilizado series diarias de espesor de la cubierta nivosa de cinco estaciones, la mayoría en tierras bajas de esa región y una en la montaña Alpina. Las tendencias lineales indican cambios negativos en el numero de días con nieve en todas las estaciones de tierras bajas, con significación estadística el 95% solo en dos de ellas (Hamburg and Giessen), con una disminución en torno a 4 dias/decada. En la region Alpina se detecta ligeras tendencias positivas. Igualmente, la evolución del espesor máximo de nieve presenta tendencias negativas significativas únicamente en Huyesen y Viena.This work was partly supported by the Polish Committee of Scientific Research under grant 2P04E 05930

Climatology of hail in central Europe

Taking into consideration the spatial variability of the occurrence of hail in central Europe in the warm season (April – September) during the years 1966-2010, five hail regions were distinguished by Ward’s group hierarchy method. For this purpose the daily data of hail occurrence were used. Circulation patterns responsible for hail precipitation at each cluster of stations were analysed using Reanalysis data (NCEP/NCAR). Composite maps of the sea-level pressure, 500 hPa geopotential height and 850 hPa-level temperature means were constructed for the days with hail. Additionally, anomalies of the values of each parameter were presented. It was found that more than 65% of hail events were recorded from April to June, with May as the hail-peak month. In all five distinguished regions hail precipitation was associated with negative anomalies of SLP and 500 hPa heights over Europe, most often with low-pressure systems developing within colder than usual air mass

Wybrane przypadki obfitych opadów śniegu w Poznaniu

Composite maps of the sea level pressure and 500 hPa geopotential heights means and anomalies were constructed for the days with the high snow accumulation in Poznań. Similar maps of the air temperature at the isobaric level 850 hPa and of precipitable water content were presented. Additionally, 48-hours back trajectories of air masses for chosen days with the most effective snowfalls were constructed, using the NOAA HYSPLIT model. Negative anomalies of sea level pressure and 500 hPa heights, which mean low pressure systems spreading over Europe, are the basic condition of abundant snowfalls in Poznań. Snowfalls may appear as a result of fronts in the colder parts of Mediterranean cyclones with the dynamic warm and humid air of distant southern origin climbing upwards on the cooler and more stabile polar air masses from the north or east. The alternative location of snow-bringing low pressure systems is the Baltic Sea region.52337Badania Fizjograficzn

Variability of summer meteorological and biometeorological conditions in the Ebba Valley region (Central Spitsbergen)

Variability of summer meteorological and biometeorological conditions on the topoclimatic scale in the 2008–2010 summer season in the Ebba Valley region (Central Spitsbergen) was investigated. Three measurement sites, representing different altitudes and topography, as well as different types of active surfaces typical of Spitsbergen, were chosen, where automatic, hourly recorded, measurements were taken. The mean diurnal course of the basic meteorological and biometeorological parameters (i.e. air surface temperature, relative humidity, wind speed and wind direction, global solar radiation, wind chill temperature, cooling power, etc.), was computed for each of the three sites, which demonstrated spatial and temporal variability of biometeorological and weather conditions. Furthermore, four relevant weather types which may appear in the summer in different environments represented by the three measurement sites were distinguished. They can be defined as follows: type 1 – cold and windy weather, type 2 – cold and wet weather, type 3 – sunny weather (moderately windy and relatively warm), type 4 – warm and cloudy weather. The characteristics and occurrence of each of these types were described.517211Badania Fizjograficzn

Review of Polish contribution to snow cover research (1880–2017)

The purpose of this article is to present the development of multifaceted research on snow cover conducted by Polish researchers in various parts of the world since the end of the 19th century up to the modern times. The paper describes Polish studies on physical and chemical properties of snow cover, its long-term changes, relationships between snow cover and climate, impact of snow cover on environmental conditions and human activity. This work is also an attempt to show the contribution of Polish snow-related research to the international achievements in this fields

Cyrkulacyjne warunki występowania ekstremalnych opadów atmosferycznych na Spitsbergenie

Circulation conditions of extreme precipitation at Spitsbergen were analyzed in this study at the basis of daily data from 1981–2010 from the Svalbard Lufthavn station. The mean annual precipitation in Svalbard Lufthavn amounts to 189.1 mm. The most of extreme daily precipitation cases appear in autumn and winter. It is related to high frequency of deep polar cyclones in the cold part of the year, which bring snow and rain to the Svalbard Archipelago. The highest daily precipitation at Spitsbergen is observed during cyclonal circulation from south-western or western direction. In summer and autumn abundant precipitation is caused by local cyclones appearing right over or northwest to the island. In winter and spring the pressure pattern typical for the days with abundant precipitation characterizes with a thorough of low pressure spreading from the Icelandic Low through the Fram Strait to the Arctic. These circulation patterns are usually accompanied with higher-than-normal pressure over Scandinavia and northern Europe and high pressure gradients over the North Atlantic.53953Badania Fizjograficzn

Warunki mikroklimatyczne we wnętrzu boru sosnowego na Mierzei Łebskiej

The observed regularities concerning the differentiation of the temperature of individual layers of the pine forest point to the assumption by the tree crowns of the role of the active surface, which is served by the soil surface in the area devoid of vegetation. This is supported among others by the higher values of air temperature to a height of 6 m above ground level between 12.00–15.00 hours, this means during the maximum of the intensity of solar radiation (Molga 1970). Moreover the lowest values of air temperature appears to a bottom part of the pine forest above ground level between 15.00–8.00 hours. The inversion of temperature near the ground is a natural phenomenon in the night hours, particularly at dawn. If no compact vegetation layer is present, it comes into being during calm nights and in the predawn hours above the active surface (above the ground) due to the radiation of heat from the ground zone to higher layers of the atmosphere. Appearance of the cool layer in the bottom part of pine forest under the hight of 6–8 m above ground level during the points to the assumption of the role of the active surface by pine crowns at this very height (Molga 1970; Paszyński et al. 1999). Differences in temperature between the open area and the forest interior or the layer of air above the forest point to the differentiation of energy exchange processes, this being dependent on the nature of the active surface. The forest area is characterised by a clearly lower albedo value than the area of the grey sand dune upon which the MAWS 201 station is located. In addition, forest areas may accumulate a greater amount of heat during the day than the sandy soil covered with grassy vegetation. The stored heat, the quantity of which depends both on the heat capacity and the albedo value, is transferred to the atmosphere in the night. Thus, the layer of atmosphere above the forest is usually warmer at night than the air located above the ground not covered with dense and tall vegetation. During the day, the soil is considerably warmer than the active surface of the forest, which results from the lower heat capacity of the soil. For this reason, a considerably greater quantity of energy radiates in a longwave form than in the case of the forest, and thus the temperature of air above the ground during the day is higher (Paszyński et al. 1999). During the day, the interior of the forest is in turn cooler than the areas devoid of vegetation due to considerably weaker solar radiation reaching the forest bed. At night, however, due the emission of additional quantities of heat from the tall vegetation and the more difficult emission of energy from the forest soil to the atmosphere above the forest (due to its absorption by the vegetation), the temperature of air inside the forest is usually higher than in the area devoid of vegetation (Geiger 1942; Molga 1970). The distribution of humidity in individual layers of the researched forest community does not differ considerably from the results of research carried out on this topic by other authors. The greater content of water vapour in the air inside the forest in comparison with the open area results directly from the considerable intensity of evaporation of the lower active surface of the forest. The maintenance of the greatest air humidity in the lower zone of pine crowns is most probably connected with their additional transpiration (apart from the transpiration of vegetation of the forest bed) and low wind velocities, which make it possible for water vapour to gather and remain in this zone (Molga 1970).A6115716

Zmiany intensywności wyżu syberyjskiego i ich wpływ na temperaturę powietrza w środkowej Syberii

On the basis of daily data from Baseline Meteorological Data in Siberia, Version 5.0 for 5 stations located in central Siberia changes in the intensity of the Siberian High 1950–2008 and their impact on air temperature were examined. It was found that trends of the air pressure were negative in the centre of the Siberian High in the analysed period, particularly from the 1980s. The decrease in Siberian High intensity was correlated with an increase in temperature in the region. Using the average daily values of sea level pressure for the Asian sector of the Northern Hemisphere (reanalysis data), it was demonstrated that the occurrence of extremes in winter air temperature are strongly dependent on the Siberian High intensity and other macro-scale circulation patterns. Occurrence of the lowest values of temperature is accompanied by a strengthening of the Siberian High and by the negative phase of the Arctic Oscillation, while the highest values of air temperature in winter months are associated with negative pressure anomalies over the Northeastern Asia, which means a weakening of the Siberian High and intensifying of the influx of air masses from the west.67201Badania Fizjograficzn