Fourth Study Conference on BALTEX Scala Cinema Gudhjem

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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.