At a glance the correlation with winter temperatures in the UK looks to be either non-existent or weak, but I will be happy to stand corrected on this.
Originally Posted by: Brian Gaze
Here's another chart (sources: MetOffice, NOAA and Tutiempo)
It shows CET, AMO, plus the number of ice days and days with sleet or snow falling at Manston. I've also added days of just snow falling - as you can see, the majority of "snow falling" days are actually just sleet. Click for a bigger version.
My conclusions:
- The 80s really were special!
- Ice days have been much less frequent since the switch away from a negative AMO
- The amount of "pure snowfall" days has fallen, but not as much as the number of ice days
- Everything's become just that bit more marginal down here
The marginality is key. It really is a rare thing to get days on end of snow, but when it happens it used to linger for a while (which markedly increased the chance of ice days, once the cold air aloft had moved away). With more marginality, what little does fall gets washed away or simply melts that much faster. Snow depths here have become much less since the 90s - if you counted snow depth days (simply adding the snow depth at 9am, in centimetres, each day there's a cover) you'd find a startling drop since 1997. Again, 2005 is an exception here as it did manage a slushy covering for several days in a row.
The snow:sleet ratio for the decades from the above data is as follows - a higher percentage means more snow dayes versus sleet days:
72-80: 17:81 (17%)
81-90: 38:86 (31%)
91-00: 11:52 (17%)
01-10: 19:53 (26%)
11-16: 6:33 (15%)
As can be seen, again the 80s come out as special. The 90s don't, which is interesting as that decade had plenty of ice days and was the last time we had icicles here and deep powder snow. The 00s (whatever you want to call them) have a high ratio too, but this isn't due to 2010 (which only had 3 "pure snow" days), no, it's 2008 which had a large number of "pure snow" days - at 6, it contributed a third of the decade's total. Despite all that snow, there were no ice days - a key difference to earlier decades, as it meant the snow that fell thawed every day.
Phew. What turned out as a simple exercise turned into a marathon, but yet again it shows our winters down here have changed in the last 20 years. I'd be interested to see figures from our friends further north and further inland!
Edited by user
01 October 2017 15:41:18
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