In the Chamonix Valley, winter 2016-2017 has been a weird one. In terms of temperatures (which have been highly variable) and precipitation (which has been well-below average), this season has been a departure from the norm. Geoffrey Klein, PhD student in climatology working at CREA Mont-Blanc, brings us the story.
Freezing overnight and huge temperature swings
Month after month, winter 2015-2017 has seen significant variability in air temperature. Both the months of December and January were marked by frequent frosts—including 61 consecutive days with below-freezing temperatures between November 27th and January 26th. In addition, these frosts were more intense than the average established between 1981 and 2010: 51 days in December and January had temperatures that fell below -5°C compared with an average of 36 days. These conditions were caused by long periods of high-pressure, clear nights, an absence of wind, and cold air coming from Northern and Eastern Europe.
By contrast, during the month of February the number of days when the temperature dropped below -5°C was below normal (5 days vs. 15 on average) and maximum temperatures were also higher than usual (9.4°C vs. an average of 4.8°C). This meant that February temperatures exceeded the 1981-2010 average by nearly 5°C (3.7°C compared with an average of -0.8°C).
Overall, the average temperature in Chamonix during the first few months of winter has been 1.3°C above the 1981-2010 average, with high daytime maximum temperatures compensating for frequent overnight frosts.
Precipitation 60% below normal
The biggest news this winter has been the drought, with precipitation levels at nearly 60% below the average for the period between 1981 and 2010. At the beginning of the season, the Chamonix Valley didn’t receive any snow or rain for 40 consecutive days, from November 26th to January 5th. Snow cover in the valley was directly impacted: the Mont Blanc Observatory in Chamonix recorded a maximum snow depth of 35cm, in contrast with an average of 60cm during the last ten years. At higher elevations, the maximum snow depth was also very low. In the Aiguilles Rouges (near Lac Blanc, at 2330m), the maximum snow depth was only 50cm, and in early February, there was only 5cm on the ground.
Stay tuned to hear how the second half of the winter turns out.
Reported by Geoffrey Klein
Translated by Hillary Gerardi