The Illinois State Water Survey has this fascinating press release.
October Solar Radiation in Illinois: Record High in 2010, Record Low Last Year
11/9/10
Source: Bob Scott, 217-333-4966, rwscott1@illinois.edu
Did it seem to you that the weather in October was quite a bit sunnier than in Octobers of the past? Do you remember last October as being rather cloudy?
If these are your impressions, you are correct, according to Bob Scott, Director of the Water and Atmospheric Resources Monitoring Program at the Illinois State Water Survey, a division of the Institute of Natural Resource Sustainability. Scott operates an array of weather sites across the state called the Illinois Climate Network, and one of the sensors on the stations measures solar radiation.
Solar radiation totals for October 2010 were higher than in any past October since sites were installed in 1989, while the solar radiation totals for 2009 were the lowest.
“Our sensors measure what we call direct solar radiation,” Scott said. “This includes pure sunshine and reflected sunshine from clouds and blue sky.”
October typically is drier than the spring and summer months that precede it, and sunshine in October is in a seasonal decline with fewer daylight hours and the sun getting progressively lower in the sky.
“But this October was much drier than normal,” Scott said. “Consequently, there were many more days with bright sunshine and fewer days with clouds and rain, as opposed to last October which had many rain events.”
During the 20-year history of the weather station in Champaign prior to last year, sunshine in October has averaged about 379 mega joules per square meter.
If you ignore the units, Scott said, the range of solar radiation values in October in Champaign through 2008 varied from a low of 328 in 2004 to a high of 414 in 1992. The very wet October of 2009 had a total of 264 units of solar radiation, while the very dry October of 2010 reported 449.
“Both prior maximum and minimum values were slammed in the past two years,” Scott reported.
The current dry conditions have now continued into November with strong indications that it too will see above normal solar radiation.
As far as a cause for these events, “There is none,” said Scott. “Our data by themselves are far too short of a record to suggest a cause, and they are on opposite sides of the scale from each other. Without more information, these data must be categorized right now as simple natural variability.”
-30-
October Is Warm and Dry
So far, October in Illinois has been both warmer and drier than normal. As of October 19, the statewide average temperature was 59.8 degrees, 1 degree warmer than normal. The statewide average rainfall was only 0.22 inches, 12 percent of normal. See table below.
If this were July, the dryness would be a major source of concern. However, the impacts are much less in fall. In fact, the warm, dry weather aided in the maturing and harvesting of corn and soybeans. At the moment, the impacts are mostly focused on:
- winter wheat – farmers are waiting on rains for germination;
- landscaping – trees and shrubs may need more water before winter arrives;
- fall color – I’ve noticed that the fall colors on trees and shrubs this year are muted with lots of shades of brown and yellow.
The NWS forecast shows a weather system moving through Illinois over the weekend. The potential rainfall amounts from this system range from 0.25 inches along the Wabash River in south-eastern Illinois to 1.25 inches in north-central Illinois. Another system is expected to move into the region on Tuesday/Wednesday. So the current dry weather may be short-lived.
Illinois
10/01/2010 to 10/19/2010
Climate <------Temperature-----> <---------Precipitation--------->
Division Actual Normal Dev Actual Normal Dev Percent
-----------------------------------------------------------------------------
Northwest 55.2 53.4 1.9 0.09 1.82 -1.73 5
Northeast 55.8 53.7 2.0 0.27 1.82 -1.56 15
West 57.6 56.3 1.4 0.10 1.90 -1.80 5
Central 56.7 55.7 1.0 0.22 1.86 -1.64 12
East 56.0 55.4 0.6 0.38 1.86 -1.48 20
West-southwest 58.0 57.5 0.5 0.13 1.72 -1.60 7
East-southeast 58.4 57.8 0.6 0.28 1.92 -1.65 14
Southwest 58.9 58.9 0.0 0.23 1.85 -1.63 12
Southeast 59.8 59.2 0.6 0.35 1.84 -1.49 19
State 57.3 56.3 1.0 0.22 1.84 -1.62 12
Dev means Deviation From Normal, Percent means Percent of Normal
October Temperature Swings in Chicago
Like most sites in Illinois, Chicago has experienced large temperature swings in October. The month started with below-normal temperatures on October 2-5. The departures were as large as 8 degrees below normal on October 3 and 4.
This cold period was followed by a period of much above normal temperatures on October 6-12. The departures were as large as 16 degrees above normal on October 9 and 10. In fact, the high of 86 degrees reported at O’Hare on October 9 tied the record set in 1962.
Slightly above-normal temperatures prevailed on October 13-18. The early cold period and later warm periods resulted in an average of 58.7 degrees for the first 18 days in Chicago, 3.9 degrees above normal.
