Tuesday, April 13, 2010

Defining the Spring

Beijing, I learned last week, has an official definition for the arrival of Spring: the daytime high temperature has to achieve a 5-day average of 10 degrees Centigrade or better. And we passed that threshold on Wednesday or Thursday last week.

It seems a bit of a wonky criterion to me. Two or three days of reasonably mild weather, or a single properly warm one (and it's not unknown for us to have the odd day nudging above 20 degrees C in early March) will easily bump up the 5-day average to that kind of level - even though the temperature may plunge again subsequently, taking 5-day averages back below the 'Spring threshold'.

I would have thought that a more reliable test would require not just an average over a number of days, but a sequence of days - perhaps three or more - each reaching the required temperature. I would also have thought that it ought to take some account of how long the temperature has been near the highpoint, or above an agreed threshold. We have a lot of days where there's a 20-minute interval of strong sunshine, and the rest of the day is at least 5 degrees colder. If it's not feasible to measure the number of hours at or above a certain temperature, then I'd suggest that the critical threshold temperature needs to be considerably higher; 10 degrees C is still pretty nippy, anyway - I would have thought 12.5 degrees would be more like it (with a requirement of something like 5 hours a day at or above that point), or 15 degrees for an isolated peak.

Oh, and of course, it mustn't freeze overnight. The really odd thing about our weather over the past few weeks is that, although the sunshine has sometimes been quite bright and warm, the weather systems are still predominantly coming from the north - so the air is far nippier than it should be at this time of year, and the wind has a keen edge to it. We've had several nights lately where, despite Spring-like weather during the day, the temperature plummeted perilously close to freezing again overnight. Last night was definitely a good few degrees below, probably the coldest we've had since January.

The Beijing meteorologists claim, of course, that however cockeyed their definition is, in practice it seems to work well enough: for the last several years, at least, it has managed to coincide with the arrival of sustained warm weather, the end of overnight frosts, and the massed, synchronous blossoming of trees around the end of March.

This year, however, the appearance of blossoms has been sporadic thus far; and those trees that have put forth most fully will have been most severely rebuked for their optimism last night. Spring still doesn't feel like it's here, despite what the weathermen were telling us last week.

All of which is merely an excuse for a song..... It Might As Well Be Spring, from Rodgers and Hammerstein's State Fair. There's a very good rendition by the now largely forgotten Dorothy Collins, performing it live on a 1950s TV variety show here; and the classic Dick Haymes recording (no video) here; though the best of the lot is surely Ella Fitzgerald's (but again, no video). But here's Jeanne Crain singing it (well, apparently she was being dubbed by one Louanne Hogan) in the movie...


Froog said...

After a little further pondering on this, I am convinced that the news report I saw - in an English-language Chinese newspaper - must have got it wrong. The "five day average" just wouldn't work. I think the official criterion must be "five consecutive days with a high above 10 degrees C".

John said...

Any idea why it's so important to define the exact moment a season starts anyway? I know we use dates (21st of whenever or whatever it is) but the fact that I'm not 100% on them myself indicates that it can't be all that important surely?
Sorry for all the question today Froog! I just don't understand such a bizarre country (and probably never will.)

Froog said...

Fair point. No, I don't know if there is some practical significance to this. Apart from the possible tie-in to the question of the nationally mandated winter heating dates you saw me mention elsewhere; if it's "officially springtime", that might justify not extending the heating period, even if - as is often the case - it's still arse-freezing cold in the middle of March.

A possibly similar example is old employee-welfare legislation - passed long before the days of near-universal air-conditioning - that requires workplaces to close down for the day if the temperature hits 39 degrees Celsius... which it sometimes does in the summer. Er, except that somehow, "officially" it never quite does.