An interesting aspect of the current weather regime is the large diurnal (daily) temperature range--the difference in temperature between the daily highs and lows. At a number of Northwest locations we have seen highs in the 80s and 90s, while temperature have plummeted at night into the lower 50s and even some 40s, with some dropping into the 30s. I am talking about surface air temperatures here, measured at roughly 2 meters. Some good examples:
Baker, Oregon--high of 90 and a low of 39F: a diurnal range of 51F!
Olympia,WA--high of 85 and low of 44: range of 41F
Or consider the Turnbull climate reference network site near Spokane that had a 51 deg temperature range today with a low of 36 and a high of 87 on Tuesday. What is really amazing is the range of surface (ground) temperature that on Tuesday jumped from 32 F to 114 F (82F!!) on Tuesday. You read that right....from frost on the ground to 114F in one day. That will crack some rocks!
Here are graphs of temperature for the last two weeks--all of which show the huge range. First, Sea-Tac, then Pasco, and finally Spokane. All have a much greater range than normal.
We start with fairly warm aloft and the sun being still fairly strong....that allows warming.
We have weak offshore flow aloft...that keeps the low clouds and marine influence at bay.
We have clear or nearly clear skies...that allows good infrared radiational cooling to space--and thus good temperature falls at night.
And nights are getting longer--that gives more time for nighttime cooling. And the relatively equal time for heating and cooling at this time of the year is helpful
Put this all together and you get one big temperature range. During the winter the range is far less in general, particularly because the cloud cover reduces heating during the day and infrared cooling at night.
Now for the controversial part of this blog. There seems to be some difference in opinion whether a large temperature range is good for viniculture. Does a big range help or hurt the quality of grapes used in wine-making? Some online sources claim that such a range is good since it has the effect of producing high acid and high sugar content as the grapes' exposure to sunlight increases the ripening qualities while the sudden drop in temperature at night preserves the balance of natural acids in the grape. Others, like the book by Gladstone, claims that a narrow temperature range is good. Any wine experts read this blog? What is the correct story? I have always found the meteorology of wine making fascinating...and will climate change make eastern Washington wines even better? Perhaps in another blog.