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- 114 - Distribution of Snow Cover over Northern Eurasia Lev Kitaev 1 , Eirik Førland 2 , Vjacheslav Rasuvaev 3 , Ole Einar Tveito 2 , Olaf Krueger 4 1 Institute of Geography RAS, 109017, Moscow, Staromonetniy, 29, Russia, lkitaev@online.ru 2 Norwegian Meteorological Institute, Niels Henrik Abels Vei 40, 0313 Oslo, Norway 3 All-Russian Scientific Research Institute of the Hydrological and Meteorological Information – World Data Center, 249020, Obninsk, Koroleva, 6, Russia 4 Max Planck Institute for Meteorology, Bundesstrasse 55, 20146 Hamburg, Germany 1. Introduction Snow cover is one of the most sensitive indicators of environmental changes since it depends on climatic changes and at the same time greatly predetermines these changes being an interlink between climatic and hydrological processes. This paper presents results of an analysis of variations of the period with stable snow cover. This is an important parameter for studies of albedo and accordingly for climate variability. The study considers the area of north Eurasia in boundary of CIS and Nordic countries. The daily data of ground observations of snow depth and its distribution for 1936- 2000 are used. Duration of snow cover is characterized by number of days with snow cover ≥ 50%. For the analysis the average air temperature for November - May is also used. 2. Mean values – spatial and temporal variability Mean snow depth of February and number of days with snow cover >50% during November - May (1936-2000) was calculated for an estimation of regional patterns and for long-term variability over the Northern Eurasia (CIScountries, Fennoscandia). The spatial variability of snow depth over Northern Eurasia corresponds to features of atmospheric circulation and orography (fig.1A) (Kitaev et al. 2001; Kitaev et al. 2002-b). The maximum values of snow depth are found in the Ural region and the western part of low-mountainous of the East Siberia. High values are also found in a zone influenced by the Aleutian low pressure system at the Far East. Small snow depths are found in a zone influenced by the Siberian high pressure system, in the south of East European plain. The long-term mean values of snow depth has regional differences, and varies from 11 cm in the Kazakhstan region to 39 cm in Western Siberia. Number of days with snow cover >50% is smoothly increasing from the south to the north according to the spatial variability of mean air temperature of winter (November - May) (fig.1B). The regional mean values of number of days with snow cover >50% varies from 86 in Kazakhstan to 220 in Eastern Siberia. These features correspond to the regional variations of air temperatures (November – May, Figure 1C). Typical regional mean winter temperatures vary from 1.2 o C in Kazakhstan to - 22.8 o C in Eastern Siberia. A long-term increase of snow depth and number of days with snow cover is typical for most parts of northern Eurasia (fig. 2). A long-term decrease of snow depth takes place in some southern regions. These features occur on a background prevailing positive long-term trends of winter temperature in most parts of the region, with the largest increase in Kazakhstan. Over some separate northern regions there are negative temperature trends (fig. 2C). The highest positive linear trend of snow depth is found in the Far East and the East European plain. In the latter region also the largest increase in number of days with snow cover is found. For the total region of Northern Eurasia the analysis indicate positive trends (fig.2) of both snow depth (+0.091 cm year -1 ), number of days with snow cover >50 % (+0.119 days year -1 ) and winter air temperature (+0.015 o C year -1 ) The reason for increasing snow indices in regions with increasing winter temperatures is probably that higher temperatures are associated with higher amounts of precipitable water. Because of the low winter temperatures in this regions, most of this increased precipitation is falling as snow. Figure 1. Spatial variability of mean values of A) snow depth (cm) in February, B) number of days with snow cover >50% (days) and C) air temperature (degC) of winter (November-May) for 1936-2000.
Figure 2. Long-term variability in Nortern Eurasia of A) snow depth, B) number of days with snow cover >50% and C) winter temperature (November-May). Solid lines indicate liner trends. The variation of the period with stable snow cover in the Arctic coasts of Europe occurs due to a long-term increase of winter precipitation. The trend of total precipitation over November-May is positive (+0.54 mm year -1 ) for the North- European region. A Special feature observed during the last decades in Scandinavia is a tendency to decrease of solid precipitation and increase of liquid. According to data from the weather station Ny-Ålesund (Spitsbergen), the normal average annual and winter (DJF) temperatures are resp. –6.0 and –12.1 o C. Normal liquid, solid and mixed annual precipitation is 103, 176 and 125 mm, and during winter resp. 12, 133 and 81 mm. The annual sum of precipitation increases by 0.536 mm year -1 ). The increase of annual average temperature (+0.9 o C year -1 ) implies changes in precipitation structure. The amount of mixed precipitation grows and that of solid precipitation decreases (trends are +0.43 and –0.77 mm year -1 ), while there is no significant trend in liquid precipitation. This is caused by increasing air - 115 - temperature in the Barents Sea, and is linked to variations in the oceanic and atmospheric circulation in the Northern Atlantic (Førland & Hanssen-Bauer 2000). 3. Duration of snow cover and features of atmospheric circulation The correlation between spatial-temporal variations of the snow cover parameters and variation of the indexes NAO and the Siberian baric minimum is poor (Kitaev et al. 2002-a). Significant correlation is observed between the period with stable snow cover in the Far East and variability of the Aleutian baric maximum only. Positive fluctuations of the cyclonic activity of baric maximum predetermines increase of autumn and spring air temperatures and reduction of the period with stable snow cover under the maintenance of considerable snow water equivalents. 4. Conclusions As a whole for North Eurasia there has been an increase of snow depth and duration of snow cover during 1936-2000. Also the winter temperature has increased in this period. This situation is consistent with the tendencies of the present warming, where the increase of air temperature cause an increase of annual precipitation and winter precipitation in particular, and consequently also an increase in the snow water equivalent (Førland & Hanssen-Bauer 2000; Kitaev et al. 2002-b). Although there is an universal long-term increase of air temperature of winter in the region, the duration of snow cover increases in the north of the studied region and decreases in the south. This may be connected to zonal increase of air temperature from the north to the south at weak change of precipitation. The exception is the Scandinavian Peninsula, where there is a long-term tendency of decrease in number of days with stable snow cover and a change of precipitation structure (increase of amount of mixed precipitation and decrease of amount of solid). Statistical correlation between variations of the snow cover and variation of the indexes NAO and the Siberian baric minimum is poor Detailed elaboration of the results should be based on longer period of observation data and on quantitative estimation of interaction of changes of snow cover, precipitation and air temperature References Førland E.J., Hanssen-Bauer I. Increased precipitation in the Norwegian Arctic: true or false? Climatic Change, No 46, pp. 485-509, 2000. Kitaev L., Razuvaev V. and Martuganov R. Spatial peculiarity of the climatic and snow cover parameters fields interannual changes of North Eurasia. Third <strong>Study</strong> <strong>Conference</strong> on BALTEX, Publication No 20, pp.107-108, 2001. Kitaev L.M. Spatial and temporal variations of snow depth in the Northetn Hemisphere. Russian Meteorology and Hydrology, No 5, pp.20-25, 2002. Kitaev L., Kislov A., Krenke A., Razuvaev V., Martuganov R., Konstantinov I. The snow cover characteristics of northern Eurasia and their relationship to climatic parameters. Boreal Environment Research, Vol. 7, No, pp. 437-44, 2002.
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Fourth Stu
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Preface The 4 th Study</str
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- I - Table of Abstracts Title Auth
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- III - Sensitivity in Calculation
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- V - Parameter Estimation of the S
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- VII - The Realism of the ECHAM5.2
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Adam, W. K. .......................
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- 1 - Activities of the GEWEX Hydro
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eference site archive (Cabauw, Neth
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- 5 - Remote Sensing of Atmospheric
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minute averages around the satellit
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- 9 - Precipitation Type Statistics
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- 11 - Assimilation of New Land Sur
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Multichannel Microwave Radiometer f
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output has been processed in an equ
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height dependence of the Z-R-relati
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- 19 - CERES and Surface Radiation
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- 21 - Coastal Wind Mapping from Sa
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- 23 - Clouds and Water Vapor over
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- 25 - Broadband Cloud Albedo from
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- 27 - Observation of Clouds and Wa
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shows a ground-track of the vessel
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- 31 - Determination and Comparison
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- 33 - Spatial Variability of Snow
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- 35 - EVA-GRIPS: Regional Evaporat
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- 37 - LITFASS-2003 - A Land Surfac
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-39- Calibrated Surface Temperature
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- 41 - The Marine Boundary Layer -
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- 43 - Characteristics of the Atmos
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Figure 2. Surface stress from two d
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During the experiment the water was
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While the number of smallest drops
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SCANDIA will not be supported any l
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- 53 - Relationships Between Precip
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- 55 - Analysis of the Role of Atmo
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- 57 - Meteorological Peculiarities
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Baltic Sea Inflow Events Jan Piechu
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- 61 - The Different Baltic Inflows
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- 165 - Figure 1. Modeled seasonal
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- 167 - Present-Day and Future Prec
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- 169 - Extreme Precipitation on a
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at the stations Pärnu (Estonia) an
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6. Results There are many possible
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and vegetation, and to derive the h
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The structure of water bodies cadas
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Figure 1. The area of Gdańsk subje
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- 181 - Climate and Water Resources
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- 183 - Generating Synthetic Daily
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The evapotranspiration is affected
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Model parameters and coefficients:
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3. Hydrodynamic model of nutrient l
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No. 15: Minutes of 8 th Meeting of
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Fourth Study Conference on BALTEX Scala Cinema Gudhjem

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