On Tuesday, December 17, 2013 11:21:39 AM UTC, Norman wrote:
Norman wrote: Scott W wrote: Of interest to contributors in the Home Counties I have published a snow survey / winter index on my blog for my area in east London. It is inspired by the old Snow Survey of Great Britain which ceased publication after the 1991/92 season. Further to Dave Cornwell's comment a few weeks back that people mostly remember a winter through the amount of days with snow lying I decided to use the data I produced for my winter forecast and try to find out what snow cover has been like in my area going back to 1946/47 - the first year of the original snow survey. I then divided the snow lying days by the winter mean to give the index. I realise there is the work of Bonacina to consider but as this is national I wanted to look more indepth Not surprisingly the 62/63 season came out a long way ahead of the rest - mostly through the sheer sustained depth of the cold. There's also one or two surprises - strange how the memory can fool you. It is a work in progress and I would welcome any input. http://wp.me/p2VSmb-8M Using the mean temp in deg C gives a highly non-linear index as the temp approaches 0 deg C. For example, for the same snow depth the index calculated with a mean temp of +0.1 is double the index calculated with a mean temp of +0.2 deg C, which is certainly not the sort of result you are looking for. A mean temp of 0 deg C would give an index of infinity then as mean temps dropped below 0 deg C the index would be a decreasing negative value. Using a mean temp in deg K would be a much more valid approach. Sorry, I meant "for the same number of snow-lying days" not the "same snow depth". To illustrate the non-validity of using temps in deg C, if you carry out an identical exercise using temps in deg F instead, the relative severity of the individual winters changes markedly. Neither method is valid. The only valid way is to use deg K. -- Norman Lynagh Tideswell, Derbyshire 303m a.s.l.

Thanks, Norman. the degK approach makes complete sense - I'll address the necessary changes on the spreadsheet when I get a moment. As for the snow 'cm days' it is looking increasingly like I'll need a trip to Exeter to view daily data - apart from my own relatively limited stats I only have access to the monthly data in the Snow Survey. All fascinating stuff