We experienced a very abrupt transition this week, from unseasonably cool temperatures to the usual very hot days of summer. We haven't broken 100 F yet, but we're getting close...The graph at right shows the sunlight levels here for the past seven days, as measured by my weather station. You can see by the nice smooth curve that the past five days have had totally uninterrupted sunshine -- not a cloud to be seen anywhere, and wall-to-wall blue sky. The forecast is calling for partly cloudy today through the weekend, and even a chance of drizzle on Sunday -- but that same forecast called for partly cloudy the last few days, so its credibility with me is quite low!
The graph at right shows our relative humidity (in green, using the righthand scale) and temperature (in red, using the lefthand scale). Here you can see that the past three nights have been very low humidity -- not the usual pattern, but common enough. These low humidity nights are quite reliably followed by rapidly heating air in the daylight, and high temperatures; that pattern holds here, and therefore I expect high temperatures again today. It seems that dry air heats more rapidly than humid air, which makes sense -- there's much less energy to expend. Also, the wet air at night is at least partly caused by evaporation of water from plants and the ground, and the evaporation process reduces the temperature at night, giving it further to climb the next day. It's times like these that make me thankful for a reliable air conditioner!
No comments:
Post a Comment