M. Kim Johnson

October 31, 1999

Attorney General's Office

State of New Mexico

I have finished a review of letters sent to the Attorney General of New Mexico's office from several writers. In each of these letters, the writers express concern that aircraft are spraying biological or chemical materials into the atmosphere for unspecified purposes. One of the letters quotes anecdotal incidences of sickness that might be tied to the aircraft activity. The letters refer to "chemtrails" as well as contrails.

I have read the letters and reviewed the referenced web pages . In so doing, I have viewed a number of photos purporting to be of aircraft spraying the chemical or biological material into the atmosphere. I have also discussed these letters with another scientist familiar with upper atmospheric phenomena from Sandia National Laboratory and an retired general and fighter pilot who is an Air Force Hall of Fame Member inducted in at the same time as Neil Armstrong and former President Ford.

In summary, there is no evidence that these "chemtrails" are other than expected, normal contrails from jet aircraft that vary in their shapes, duration, and general presentation based on prevailing weather conditions. That is not to say that there could not be an occasional, purposeful experimental release of, say, high altitude barium for standard wind tracking experiments. There could also be other related experiments that occur from time-to-time which release agents into the atmosphere. However, not one single picture that was presented as evidence indicates other than normal contrail formation.

The variation in presentation is explained by the tropospheric conditions and, to some extent, the positioning of aircraft engines. When the troposphere experiences a relatively stable, supersaturated condition (water vapor in excess of 100% humidity without condensation), then any disturbance that causes formation of ice crystals provides nucleation surfaces for the supersaturated moisture to condense upon. When a jet engine burns its fuel, the major byproduct is water vapor. When the exhaust passes over the rear stabilizer of an aircraft, the tips or ends of the stabilizer cause the exhaust to expand rapidly. When it does, the temperature decreases rapidly within a turbulent flow, and ice crystal formation is forced. Generally, this makes it look as if the jet were spraying a cloud from the ends of the stabilizer. If the atmosphere is not at saturation, the contrail will not persist. The formed ice crystals will sublimate into the surrounding atmosphere. Hence, the appearance of a short, well formed vapor trail. If the water content is very low, then no discernible contrail will form at all. All the exhaust water will be absorbed by the atmosphere before there is time to form ice crystals.

If the atmospheric water content is not consistent with altitude (picture atmospheric "waves" of high water vapor content below a layer of low water vapor content much like waves on the ocean), then a jet will alternately pass through air that allows contrail formation and air that does not. This gives the appearance of a dashed line if the plane is flying at, or near the perpendicular to the waves. If the atmosphere is highly supersaturated, then the formed ice crystals may act as nucleation centers for a continual spreading of the contrail. In other words, the contrail actually causes the supersaturated moisture to condense, spreading out from its original path. This causes the formation of a cirrostratus cloud structure, far in excess of what would occur from a simple contrail.

One other phenomenon observed is the formation of contrails off wing surfaces along with the engine exhaust contrails. This can be caused when the air is highly supersaturated and the expansion of the air coming off of the wing surface is sufficient to cause ice crystallization. In this case, it appears that the whole plane is leaving a trail. This can often be observed by a passenger flying in a commercial airplane when entering cold, supersaturated air, particularly in the winter when close to a storm front.

There were no pictures or evidence that indicated anything other than the above contrail formation phenomena. Anecdotal stories of persons getting sick after contrails from obviously supersaturated tropospheric conditions lend no basis for belief that there are chemicals or biological agents being released. This type of story provides as much credence to "chemtrails" as does the belief that drinking milk is causally linked to heroin addiction. (Almost all heroin addicts in the US drank milk as children.)

Please contact me if there are any questions.

Sincerely,

M. Kim Johnson, Physicist 

	This F-22’s condensation trails (contrail) from the rear vertical and horizontal stabilizers that occur generally only at lower altitudes. These typically do not persist for any significant length and are reabsorbed back into the atmosphere. At higher altitudes, these type contrails can be generated with engine created water vapor streaming over the stabilizers and are created by non- turbulent flow conditions that allow the formation of ice crystals and/or water droplets (rapid expansion and cooling of the air). These are typically non-persistent, too, but appear to be ejected from the aircraft. For some beautiful pictures of some special aerodynamic contrails, please see this site. At the referenced site, the explanation centers on wing airflow, which is generally very non-turbulent, but causes rapid expansion of the air to allow rapid cooling and the attendant condensation.
The picture at the right of an F-22 and an F-15 demonstrates the lack of contrail formation at higher altitudes, where humidity is too low for non-turbulent air flow to create the short lived contrails described above.
	Here is a normal contrail from a four-engine jet (contrails can come from internal combustion or turboprop engines, too). Atmospheric conditions are good for allowing the water vapor from the burnt fuel to condense and persist. Note that the contrails start behind the engines, and there are no apparent aerodynamically caused contrails. This is, by far, the most common contrail generated and observed.
Finally, as is often the case, atmospheric conditions are such that no contrail can even form.

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