Oct. 15, 2004 Contrail Count-a-Thon

Results for Oct. 15, 2004

A total of 218 observations were received from 3 sources: regular GLOBE observations, regular S'COOL observations, and through the event website. Maps of total and short-lived contrails are shown below.

The distribution of observations is about the same as on the 14th, so we will again look more closely at North America and Europe.

Europe

The satellite imagery shows another very cloudy day in Europe, agreeing well with the reports from the ground observers. Contrails were reported only around edges of this image and are not particularly detectable from space on this day. Image from MODIS instrument on Terra, at 10:50 UT on Oct. 15, 2004.

North America

Again, observations were made covering a large area of North America, especially the eastern half. On this day a few more contrails are reported than the day before. Looking at the satellite imagery, NOAA-17 on the left over the West coast and MODIS on the right over the East coast, one can see that the areas where no contrails were reported correlate well with areas of extensive cloud cover, particularly in the Northwest, Midwest, and Northeast. In the areas between clouds, we do get reports of contrails.

Relative Humidity with Respect to Ice, Percent	If we look at the prediction of contrail occurrence on this day, the relative humidity with respect to ice (RHI) values are quite low over the entire US. Thus contrails would likely not be predicted on this day. However, count-a-thon participants do still report them.
Relative Humidity with Respect to Ice, Percent	In this case, it is interesting to look at the maximum value of RHI within the layers of the atmosphere where planes generally fly. This is shown at left. There are clearly some thin layers of higher humidity even in the relatively dry atmosphere, and the observed contrails correlate well with these areas in most cases.