State of the ground: Climatology and changes during the past 65 years over Northern Eurasia for snow cover, dry, wet, and frozen ground conditions

Significant climatic changes over Northern Eurasia during the 20th century are revealed in numerous variables including those affecting and characterizing the state of the ground. Synoptic archives in the former USSR (as well as some other countries) contain regular daily and semi-daily reports about the state of the ground in the area surrounding the station. Information about frozen, dry, wet, ponded, snow-covered land, and in the case of snow-covered land, about the characteristics of snow cover is available in these reports. A new Global Synoptic Data Network consisting of 2100 stations within the boundaries of the former Soviet Union created jointly by National Climatic Data Center and Russian Institute for Hydrometeorological Information was used to assess the climatology of dry/wet land conditions, snow cover, frozen and unfrozen ground reports, and their temporal variability for the period from 1936 to 2000. Comparison with satellite measurements of snow cover extent has been conducted.

During the second half of the 20th century and over many regions in Northern Eurasia, a reduction of the cold-ground conditions (snow covered and frozen) was compensated by an increase in unfrozen-ground conditions (6 days since 1956 over Russia). The most prominent changes occurred in the spring season in Siberia, by approximately 5 days during April and May. Since the beginning of the data set, surface temperature changes in high latitudes have not been monotonic. As a result, linear trend analyses applied to the entire period of observations can lead to paradoxical conclusions. Specifically, changes in snow cover extent during the 1936-2000 period cannot be linked with “warming” (particularly with the Arctic warming) because in this particular period it was absent.

Dynamics of the duration of the dry land surface periods based on state of the ground reports will be presented at the Conference.