Oct. 14, 2004 Contrail Count-a-Thon

Results for Oct. 14, 2004

A total of 215 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.

We received observations this time from more places, but clearly, most of the observations came from the US and Europe, with almost no contrails reported in other parts of the globe where observations were made. Thus, let us look more closely at these two regions.

Europe

Count-a-thon observations were made covering large parts of Europe. Contrail cover is relatively sparse on this day, with a few observed in Spain, the UK, and Central Europe. Looking at the satellite imagery for this day, this is because there is a large amount of cloud cover over Europe. You can, however, see some contrails around the edges of the clouds in Central Europe, as indicated by the ground observers. Image from MODIS instrument on Aqua, at 11:50 UT on Oct. 14, 2004.

On the next orbit, at 13:25 UT, MODIS provides a good view of Spain. Again there is lots of cloud cover, with clearing in the Southern half. The contrails reported by the ground observers cannot be seen in this image, most likely because they are too narrow to be picked up. Count-a-thon observers indeed reported no spreading contrails in this region. The red dots in these images represent places where MODIS has identified active fires.

North America

Again, observations were made covering a large area of North America, especially the eastern half. On this day very few contrails were observed. If we look at some of the satellite imagery for this day, in this case from the AVHRR instrument on the NOAA-17 spacecraft, the reason for that is quite clear: most of the area was covered by clouds.

Relative Humidity with Respect to Ice, Percent

If we look at a prediction of contrail occurrence, using the relative humidity with respect to ice (RHI) predicted in the upper atmosphere by a weather prediction model, we see that the areas where contrails are likely are also areas where cloud cover already exists on this day (green and yellow areas in the map below). In theory, contrails should only form when the RHI is 100%, but the model calculation is approximate, and also averaged over a wide slice of the atmosphere where planes typically fly. Thus, this picture only gives a qualitative idea that contrails are more likely to form where the RHI is higher, and less likely to form in areas of low RHI where the atmosphere is drier.