Inside Report (3)

Those cloudy jet trails you often see high overhead can affect the temperature and amount of sunshine in your neighborhood.

University of Illinois climatologist Wayne Wendland says the effects depend upon how wide a swath the high trails cover and for how long. The shadows cast can slow the rate that morning warms up or evening cools down by two degrees or more an hour and cut sunlight intensity by one-fourth to two-thirds.

Wendland just finished a two-year study on jet trails in a 10-state area in the Midwest. He notes that jets issue ''contrails,'' as they are technically labeled, on only about one-third of all flights, but the resulting cloud cover can stretch as much as 70 miles in length and 40-50 miles in width and last 40- 60 minutes.

You may not notice the effect - other than by having to wear a coat a little more. But Wendland wants to assess the impact on agriculture - if his National Science Foundation grant is continued.m