Regional differences of snow depth variability in Northern Hemisphere

1. Regional differences of snow depth variability in Northern Hemisphere Lev Kitaev Institute of Geography RAS Moscow, Russia

2. The goal The investigation deals with three problem related to the snow cover: • —regional feature of long-term • variability of snow depth • —snow depth relation to the index • North Atlantic Oscillation (NAO) • —regional feature of correlation for snow • depth and snow water equivalent. Lev Kitaev lkitaev@online.ru

3. Initial Data The investigation deals with three problem related to the snow cover: • —regional feature of long-term variability of • snow depth • —snow depth relation to the index North • Atlantic Oscillation (NAO) • —regional feature of correlation for snow depth • and snow water equivalent. Lev Kitaev lkitaev@online.ru

4. Regions and locations of meteorological stations Lev Kitaev lkitaev@online.ru Lev Kitaev lkitaev@online.ru

5. Regional feature of long-term variability of snow depth Trend of snow depths in the north of Eurasia (A) and of Northern America (B) are characterized by opposite signs, i.e. 0.24 and –0.33 correspondingly. Rate of snow cover change in North America is greater than that in Eurasia that is agreeing with differences of snow depths. The outlined tendencies are also typical for individual regions. On the average, for the period since 1967 till 1982 snow depth for February was 1.5 times greater in northern part of the North America in comparison with that in the Northern Eurasia. Maximum snow cover water equivalents differ from each other by the factor of two. Lev Kitaev lkitaev@online.ru

6. Analysis of correlation between long-term variability of the mean of winter NAO index and snow depths in March has been made. Reliable correlation between the dynamics of snow cover water equivalents in the East-European Plain and NAO-index is almost lacking, when positive values of correlation coefficients gravitate towards the northern latitudes and the negative ones to the southern ones. This fact can be concerned with direct relationship between change of NAO-index and cyclone motion in Europe from south-west to north-east that takes place in cold season. Thus, that is the northern part of East-European Plain, which is under their effect. So, when NAO-index increases, precipitation and snow accumulation do the same. Lev Kitaev lkitaev@online.ru

7. Snow depth relation to the index North Atlantic Oscillation In the northern part of Northern America, correlation between snow cover water equivalents and NAO-indexes both averaged over winter and the March ones is also insignificant. At the eastern coast, zone of positive correlation coefficients with some anomalies of reliable correlation coefficients caused apparently by Island Minimum that is elongated along a meridian is observed. Lev Kitaev lkitaev@online.ru

8. Regional feature of correlation for snow depth and snow water equivalent. Currently, shortage of data on snow water equivalent takes place in practice of field observations. We have assessed correlation between variations of snow depths and snow water equivalents. Interannual changes of the seasonal and March snow depth on rack and at survey observation is similar. The differrenses is not more than 10 cm. Lev Kitaev lkitaev@online.ru

9. Currently, shortage of data on snow water equivalent takes place in practice of field observations. We have assessed correlation between variations of snow depths and snow water equivalents. Data of observations over 1966-1990 obtained from meteorological stations of great regions of Northern Eurasia have been used. Coefficient of correlation between long-term variations of seasonal and March snow depths and snow water equivalents obtained in course of snow survey makes up 0.85-0.95.

10. Regression for interannual variability of snow depth (H, cm) and snow water equivalent (SWE, mm) in March(snow surveys, 1966-1990 )

11. Regression equations.was checked through independent data for 1991-1996. Along with that, a difference between a calculated snow water equivalent and that measured in course of snow survey makes up 10-15% and not more than standard lapse of observation. Lev Kitaev lkitaev@online.ru

12. Results On the average, for the period since 1967 till 1982 snow depth for March was 1.5 times greater in northern part of the North America in comparison with that in the Northern Eurasia. Volume of snow cover water equivalents of individual regions also corresponds to this volume.   Reliable correlation between the dynamics of snow cover water equivalents in the East-European Plain and NAO-index is almost lacking, when positive values of correlation coefficients gravitate towards the northern latitudes and the negative ones to the southern ones. In the northern part of Northern America, correlation between snow cover water equivalents and NAO-indexes both averaged over winter and the March ones is also insignificant. At the eastern coast, zone of positive correlation coefficients with some anomalies of reliable correlation coefficients caused apparently by Island Minimum that is elongated along a meridian is observed. Lev Kitaev lkitaev@online.ru

13. Results Coefficient of correlation between long-term variations of snow depths and snow water equivalents obtained in course of snow survey makes up 0.85-0.95. Regression equations were calculated. Equations should be used for regional hydrological balance calculations. Lev Kitaev lkitaev@online.ru