Contrails and Cloudiness

contrail1
Photo by Jim Angel, Champaign, IL, January 28, 2015.

This morning we had a brilliant display of airplane contrails, enough to significantly increase the cloudiness (as if we needed more cloudiness this winter). Despite rumors to the contrary, airplane contrails are just the byproducts of burning jet fuel at high altitudes where the air is very cold and dry. The basic chemistry involves combing a carbon-based fuel and oxygen to produce CO2 and water.  CH4 + 2O2 –> CO2 + 2H2O

It’s the same process you see on a cold morning with car exhaust. The water vapor exits the exhaust pipe and condenses when it hits the colder air temperature, resulting in a white fog.

There have been some studies (mentioned below) to suggest that airplane contrails can lead to regional increases in cloudiness over time. As a result, in certain regions the daytime highs may be lower and the nighttime lows higher. In other words, a reduction in the range of daily temperatures. Continue reading

Fort Armstrong Weather Records (1820-1836)

This semester a University of Illinois Department of Atmospheric Science student, Lauren Graham, worked to make available scanned images of the weather records for Fort Armstrong that cover the period 1820 to 1836. Fort Armstrong was located at the present-day Rock Island Arsenal. The original records were maintained and scanned by staff at the Rock Island Arsenal Museum.

These are the oldest official weather records that I have been able to find for Illinois. The records contain daily temperature readings taken at 7 am, 2 pm, and 9 pm, as well as comments on the weather. My favorite is a note in the first month about a “violent hurricane” on July 21 1820 (see image below). I’m sure it was not really a hurricane but either a tornado or severe thunderstorm with high winds.

Here is the press release of the story.

Here is the Fort Armstrong page containing the images and preliminary analysis.

The plans are to introduce more analysis of these data over the summer.

Fort Armstrong, July 1820. Note the comment on July 21 about the “violent hurricane”. Click to enlarge.

New Climate Normals for Illinois

The new 1981-2010 climate normals are available for Illinois. You can find them through a station list or a Google Map on my homepage.

Climate normals are 30-year averages that are updated every 10 years in the U.S. The National Climatic Data Center produces the climate normals for the US. By settling on a standard averaging period, users are able to compare climate conditions between two or more locations.

By updating every 10 years, the climate normals can reflect data from newer stations as well as reflect any changes to the climate.  One impact of switching from the 1971-2000 to the 1981-2010 climate normals was that the cold, snowy winters of the 1970s fell out of the calculations. As a result, the new normal snowfall has dropped a little in most places. For example, the new normal annual snowfall is 3 inches less in Champaign-Urbana.

The National Climate Data Center has a climate normals page dedicated to the new climate normals and frequently asked questions.

Snowfall Totals from around Illinois

The winter storm of February 1-2, 2011, will be remembered by many in northern and central Illinois. The National Weather Service (NWS) did an excellent job of producing forecasts and warnings on this storm. In the aftermath, we have began collecting the snowfall measurements from a variety of networks. Rather than list all the data here, I have provided some links to data sources.

Snowfall totals and some maps provided by NWS offices are available here:

Here is a preliminary look at snowfall totals across the Midwest. Snowfall amounts in excess of 12 inches extend from Oklahoma, into Missouri, the northern half of Illinois, and on into northern Indiana and southern Michigan.

Experimental Hour Snowfall Analysis
Preliminary snowfall totals map for the February 1-2, 2011 storm (NWS image).

And zooming in on northern Illinois.

Snowfall totals for the February 1-2, 2011, event in northern IL (NWS image).

Short-Term Weather Lore Holds a Kernel of Truth

Before the Internet, The Weather Channel, and NOAA radios, our ancestors relied on nature to tell its tale of upcoming weather. Moss growing on the south side of trees and squirrels hiding their nuts deep underground were thought to foretell a severe winter ahead.

Some natural prognostications like these are grounded in truth, given our current knowledge of meteorology, but others are purely fiction, according to State Climatologist Jim Angel of the Illinois State Water Survey at the University of Illinois at Urbana-Champaign.

Short-term weather forecasts based on nature observations are more likely to be accurate than long-term seasonal predictions.  In fact, there may be some merit to the notion that bad weather is coming when cattle lie down in the pasture and birds fly low.

“Many animals have a better sense of hearing and smell than we do, so when humidity, air pressure and wind direction change right before a storm, as well as the distant rumble of thunder, some animals may become restless,” Angel said.  “They can pick up on weather changes hours before we can.”

Predictions based on the appearance of the sky are thought to be particularly valuable, since certain clouds are associated with certain weather conditions, according to Angel.  Clouds described as mare’s tails and mackerel scales are very high-level cirrus and cirrocumulus clouds that can precede an approaching warm front, with rain not far behind.

Likewise, a halo around the moon is actually the refraction of moonlight through the ice crystals that make up high-level cirrus clouds, indicating an approaching low-pressure system bringing rain or snow.

Long-term forecasts, such as winter weather predictions, are much more uncertain.

“Centuries ago, it was important to determine how severe the winter would be so that adequate wood and supplies would be stored for the duration,” Angel said.  “The early settlers’ lives may have depended on their predictions, so they were grasping at anything to forecast the coming weather.  However, the size of the brown band on woolly worms, the groundhog seeing its shadow, or spoon-shaped persimmon seeds are just happenstance.”

Even with today’s modern technology, the theoretical limit of daily weather forecasts is about two weeks. Within the 6- to 14-day range, forecast errors can be large enough to limit their usefulness.

That is why forecasters typically only discuss general patterns of weather behavior beyond five days, usually in terms of probability or odds. For example, the 8- to 14-day forecast may show the eastern U.S. with an increased chance of below-normal temperatures.

The same is true for seasonal forecasts that are driven by both long-term trends and specific weather patterns such as El Niño.

For the upcoming winter, forecasters look at historical records to decipher a pattern.  The Midwest is under the La Niña effect, which is characterized by unusually cold waters in the eastern tropical Pacific Ocean.

The National Weather Service’s winter forecast for Illinois is an increased chance for above normal temperatures in the southern two-thirds of Illinois, and equal chances of above, below, and normal temperatures in the northern third of Illinois. All of Illinois has an increased chance of above normal precipitation.

What does the woolly worm predict?

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Source: Jim Angel, Ph.D. (217) 333-0729, Fax: (217) 244-0220, jimangel@illinois.edu

Editor: Lisa Sheppard (217) 244-7270, sheppard@illinois.edu

The Illinois State Water Survey at the University of Illinois at Urbana-Champaign, a division of the Institute of Natural Resource Sustainability, is the primary agency in Illinois concerned with water and atmospheric resources.