Cold- and warm-deep-snow winters in Mongolia

Abstract

Eurasian snow cover in spring has followed a decreasing trend since the mid-1960s, but winter conditions remain unknown because of a lack of data. To address this issue with a regional focus on the eastern part of Eurasia, we conducted an observational study of winter temperature, precipitation, and snow depth in Mongolia and the associated atmospheric circulation. We used the meteorological data at 21 representative Mongolian weather stations for four winter months (November to February) from 1960 through 2007. Time series analysis was applied to three indices: standardized deviations from the mean for this 4-month period averaged over the 21 stations in Mongolia for snow depth, precipitation, and temperature. This analysis revealed a significant multi-decadal trend in temperature, but not in snow depth.During the 1960s and 1970s deep-snow winters coincided with extreme cold. However, beginning in the winter of 1992-1993, a new type of deep-snow winter with warmer conditions has occurred in some years. Moreover, a synoptic analysis demonstrated that a trough at the 500-hPa level that is usually climatologically located east of Mongolia extended westward to Mongolia during the cold-deep-snow winters. This indicates that enhanced cold surges from the north to Mongolia led to the historically typical deep snow conditions. On the other hand, the warm-deep-snow winters were characterized by a weakened trough, weakened cold surges, and concurrently intensified moisture transport from the west into Mongolia. The new circulation pattern observed here shows that warm winters, which may become more frequent in the future, still have the potential to cause deep snow in Mongolia.

Recently increased cold air outbreaks over Mongolia and their specific synoptic pattern

“…Our finding is in accord with the results of Koike et al . (2010), Wang et al . (2009a), and Chen et al .…”

“…These studies imply that the propagation and the intensity of the SH have substantial impact on the conditions of COEs in Eurasia, by contributing to the incursion of cold air from the north. Moreover, several severe COEs have occurred in the Northern Hemisphere during the negative phase of the North Atlantic Oscillation and El Niño–Southern Oscillation (Thompson and Wallace, 2001; Morinaga et al ., 2003; Cattiaux et al ., 2010; Koike et al ., 2010).…”

Temperature changes before and after precipitation in Mongolia

“…Koike et al (2010) showed that in response to the winter warming trend the relationship between winter temperature and snow depth has changed in recent years. During the 1960s and 1970s, deep-snow winters were extremely cold winters.…”