Snowfall and the Sea

Hello everyone! Today we are going to be talking about snowfall and how it is influenced by sea surface temperature (SST). There have been multiple studies focused on how climate change will affect snow in various mountain ranges, but they disagree in how the snow responds to SST. How exactly Europe’s climate responds to SST isn’t completely understood.
I mention Europe specifically here because that’s where today’s article focuses. Projection in snowfall characteristics over the European Alps and its sensitivity to the SST changes: results from a 50 km resolution AGCM” was written by N. FreychetH.-H. HsuA. Duchez and C.-Y. Tu and was published in Atmospheric Science Letters in 2017. Here, a detailed atmospheric global climate model (AGCM) is used to investigate the impact on snowfall from SST.
The authors used historical, daily data, with observations of precipitation and air temperature from 1979 to 2008 to act as a comparison for a projected 2075 to 2100 setting. There were no data sets for snowfall specifically, so here snowfall is taken to be precipitation on days at or below freezing–not a perfect system, but suitable.
The European Alps, shown snow-capped and free of clouds. Image credit NASA Earth Observatory.
The amount of snow that fell is considered its intensity, and this was averaged to find the average intensity. The top one percent of snowiest storms are marked in a separate category of ‘heavy snowfall’.
The authors ran three projections of the model with different SST patterns for the 2075 to 2100 time range. These resulted in less frequent snowfall than is known for the historical data (especially below 600 meters (1,969 feet) elevation, which was 40 to 80 percent less). The intensity also decreased in these projections (except for one, which had an increase in the lower altitudes). This one, C2, shows a 40 to 110 percent increase in intensity and frequency of snow under 1200 meters (3,937 feet), though above this point it decreased similarly to the other models. It would thus appear that the largest impact on snow from the SST is on lower altitudes.
Generally, these projections show intensity decreasing in the south and west sections of the Alps, and increasing in the north and east. Simulation C3 has frequency reduced overall, while C1 and C2 increase slightly in the highest part of the Alps (the center of the range).
That was for the average snowfall. For heavy snowfall projections, C1 and C3 showed an overall decrease except in the eastern/central area. C2 had a notable increase almost everywhere except the southern areas, and its frequency of storms increases over central and northern areas (the other projections showed decrease, though C1 did indicate an increase in the central Alps).
All projections had an increase of 4° C  (7.2° F) in the air temperature.Snowfall reduces in all projections, of course, simply because there are less cold days. Since SST does not affect air temperature, it implies other factors are at work here. One is the atmosphere over the North Atlantic, a known variable in Europe’s climate. The differences here may in part be due to moisture transport, with some areas getting more moisture, others less, and thus less snowfall. While a factor, the SST alone may not strongly impact average snowfall in and of itself, but can be important for local areas. After all, snowfall affects not only the local ecosystem but any tourism or business that relies on snow.
Bibliography
Freychet, N., et al. “Projection in snowfall characteristics over the European Alps and its sensitivity to the SST changes: results from a 50 km resolution AGCM.Atmospheric Science Letters 18.6 (2017): 261-267.
Today’s featured article.
Scott, Michon. A Clear View of the Alps. NASA Earth Observatory. 23 Jan., 2011. Web.
The source of the image used in today’s post.

 

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