Snow Cover Change

Snow cover (SC) is a great indicator of climate change. It is highly related to temperature. Since the Polish climate faces warmer conditions, changes in the wintertime precipitation phase are observed. More frequent rainfall instead of snowfall is noticed at the end of the 20th and beginning of the 21st centuries. This work presents the spatial distribution, its changes, and variabilities of selected parameters that described snow cover in Poland from 1966/1967 to 2020/2021. The snow characteristics used in the study comprise of SC duration (SCD), the first and last day with SC in the season (SCbeg and SCend), the potential duration of SC season (PSCD), SC stability (SCS), average, maximum and accumulated SC depth (HS, HSmax and AHS). The changes in snow cover waves were analysed. Generally, the Polish climate is mild in the west, where the snow cover is finer and occurs relatively rarely and becomes more continental toward the north‐east, where the snow cover has a better condition to accumulate and preserve. The southern parts of the country are covered by mountain ranges of the Carpathians and Sudetes, where the snow cover remains the longest. The spatial distribution of the coefficient of variability is reversely proportional to SC characteristics—the highest in the north‐east (especially for the HS, HSmax and AHS). The most significant changes in SC are related to a decrease in SCD (5–7 days/decade), HSmax (1–2 cm/decade) and AHS (30–60 cm/decade). At the same time, the snow cover season becomes considerably shorter (especially in the western and central parts—about 10 days/decade). The trends in SCS are not yet significant in most of the country. This study reveals that the snow cover in Poland is under constant change, and the negative trends, which were hardly or not visible at the end of the 20th century, in the last decades have become statistically significant in a greater number of Polish stations.

Section: Discussionsupporting

confidence: 89%

Section: Discussionsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

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Recent changes in the snow cover characteristics in Poland

Wibig

Jędruszkiewicz

2023

“…There are concepts of intensifying meridional circulation and enhancing extreme weather in mid‐latitudes due to slower and wavier jet stream (e.g., Francis and Vavrus, 2012). However, they do not seem to prove themselves in the winter season in central Europe, and global warming seems to reduce the severity of winters and frequency of heavy snowfall and snow cover occurrence in general (Falarz and Bednorz, 2021).…”

Section: Discussionmentioning

confidence: 99%

Climatology and extreme cases of sea‐effect snowfall on the southern Baltic Sea coast

Bednorz

Czernecki

Tomczyk

2022

Self Cite

Heavy snowfall events of possible sea‐effect origin, occurring on the southern Baltic Sea coast, are described in this study. The analysed region is not very snowy, with an average of 40 days with snow cover in the winter season and a mean maximum snow depth of 8–12 cm. Twenty‐five snowfall events were selected using the threshold of 20 cm/2 days (i.e., 20 cm of snow depth increase during 2 days), and the synoptic climatology, as well as triggering factors of their occurrence, were defined. The bipolar pattern of sea level pressure with a high‐pressure over Scandinavia and a low‐pressure system southward of it was identified as favourable for sea‐effect snowfall on the southern Baltic Sea coast. This pressure field, causing northeastern circulation in the lower troposphere, brings cold air masses over the relatively warm sea basin, and the negative anomalies of air temperature at 850 hPa geopotential level, amounting to −9°C, encompass Scandinavia, as well as central and northeastern Europe. This makes the temperature difference between the air at the 850 hPa geopotential height and the sea surface exceeding 15°C. This large temperature difference establishes favourable conditions for convection in cold air masses, which become unstable while crossing over the warm sea. The formed clouds give snowfall in the coastal areas. In the further part of the study, three sea‐effect snowfall cases were chosen for detailed analysis, including atmospheric sounding, radar and satellite images, air parcel backward trajectories, and synoptic maps. They reveal high‐pressure wedges associated with low air temperature over Scandinavia and northern airflow over the Baltic Sea. The wind direction and the temperature of air masses are key components in the occurrence of sea‐effect snowfall, and global warming conditions seem to reduce the frequency of snow events over the Polish Baltic Sea coast.

“…Changes in NAO index values largely explain changes in dates of snow disappearance, the number of days with SC, and its depth in Poland as well (Bednorz, 2002; Czarnecka, 2011; Falarz, 2007; Tomczyk et al, 2021), whose contribution to SC in Europe is decreasing in an easterly direction (Bednorz, 2004; Hori & Yasunari, 2003; López‐Moreno et al, 2011; Szwed et al, 2017). Recent research results indicate a progressive negative trend in snow conditions in Poland (Falarz & Bednorz, 2021; Tomczyk et al, 2021). By the end of the 21st century, SC in the Northern Hemisphere is projected to decrease further by 7% to 25%, depending on climate scenarios (IPCC, 2013, 2021).…”

Section: Introductionmentioning

confidence: 99%

Reasons for shortening snow cover duration in the Western Sudetes in light of global climate change

Urban

Richterová

Kliegrová

et al. 2023

This article discusses the reasons for shortening snow cover duration in the Western Sudetes, considering local changes in: air temperature; amount and type of precipitation; sunshine duration and atmospheric circulation leading to changes in the number of days with snow cover and its depth; and its start and end dates. All factors were linked to the exposure and relief of the study area. The analysis was made for the winter seasons (Nov–Apr) 1961/1962–2020/2021. It was found that the primary reasons for the shortening of snow cover duration in the Western Sudetes are: a multi‐year increase in air temperature and sunshine duration; changes in precipitation patterns—a decrease in the proportion of solid precipitation, changes in atmospheric circulation—including an increase in anticyclonic circulation types with sunny weather, especially in April (snow cover disappears in most of the elevation profile of the Sudetes); and less cyclonic weather types. The above factors synergistically affect the lower snow depth, and fewer days with solid precipitation, which promotes its faster spring ablation. In the subsequent 30 years (climatological norms), there is a successive shortening in its duration. On the snow cover start dates, there are no clear trends in the direction and rate of change. On end dates, negative trends are observed, in most cases statistically significant. The rate of change for the end dates of snow cover is about twice as high as the start dates. The rate of decline in snow cover is higher at stations at similar altitudes with northern macro‐exposure than southern. The results correspond with other studies from Europe and the world on the earlier disappearance of snow cover. They confirm the successive global warming and shortening snow cover duration, especially evident in the last few decades.