Contrail Diagnosis

In "Foucault's Pendulum" by Umberto Eco (translated from the Italian by William Weaver), Chapter 106, Lia has just demonstrated to Casaubon that a mysterious document, upon which Casaubon and his friends have constructed a huge and complex story they call "The Plan", is simply a merchant's "to do" list. She warns him about faking.
"Beware of faking: people will believe you. People believe those who sell lotions that make lost hair grow back. They sense instinctively that the salesman is putting together truths that don't go together, that he's not being logical, that he's not speaking in good faith. But they've been told that God is mysterious, unfathomable, so to them incoherence is the closest thing to God. The farfetched is the closest thing to a miracle. You've invented hair oil. I don't like it. It's a nasty joke."

There are many web sites on the Internet about persistent contrails or "chemtrails", as they have become to be known by some people. The premise of those sites is that persistent contrails are a recent phenomenon and are fundamentally different in nature and origin from ephemeral (short) contrails; that they are unnatural and artificial, and evidence that some agency (government and/or military) is secretly conducting a spraying operation for some purpose. It is often suggested that this operation is conducted well below normal jet cruising altitudes. The theory is advanced that there is a huge conspiracy involving governments, military, commercial airlines, atmospheric research institutions and universities. It is also suggested that anyone who advances an opposing view, that is "debunkers", are paid disinformationists, and therefore part of the conspiracy. A subset of those who subscribe to the "chemtrail" spraying theory have the view that the "black/grey beams/lines" sometimes seen projecting along the line of a contrail may be connected in some way with the spraying.

The premise of this site is that persistent contrails are no different from ephemeral contrails, except that they have been formed where the air is supersaturated with respect to ice. In that condition the ice cloud cannot evaporate because the air is already saturated with respect to ice. Eventually the air temperature (forming the environment of the contrail cloud) rises sufficiently, by descending, for example, that the air is no longer saturated with respect to ice, and the ice evaporates. The "black/grey beams/lines" are shadows in the air, cast by the contrail. These can only be seen from a point within the shadow; that is, the observer is in such a location that the contrail (or the extension from either end) is in front of the sun.

The area in New Zealand where contrails (ephemeral and persistent) are most commonly seen are the regions of Nelson, Marlborough, Wellington, Manawatu/Wanganui and Taranaki. Since the author of this site is located in Wellington, the focus is on central New Zealand. Contrails also occur over Canterbury, Waikato, Auckland and Northland.
This site discusses and explores a way of determining if jet contrails would be expected to be visible (and possibly persistent) on any day and at any location close to a meteorological upper air (radiosonde) station. There are some utilities for accessing an analysis/diagnosis of local atmospheric data (specifically for central New Zealand, and also for any location in the world), for determining the altitude and location of contrails using ground based measurements.

This is a reference to and gentle send-up of Chemtrail Awareness Day - 06.07.08 where comemorative mugs, bags, caps and T-shirts can be bought (Linked from "Products" on that site). There doesn't seem to be anything special planned for "Chemtrail Awareness Day". There isn't for "Supersaturation With Respect to Ice" Awareness Day either but it will occur first, and there seems to be a tactical advantage with that. Supersaturation Over Ice (or With Respect to Ice; it means the same) is not as catchy as Chemtrail, so a search is on for some really cool graphics. Watch this space.

Analysis Calendars
The analysis charts presented in the form of a calendar (see the navigation bar) are simply a plot of the temperature and other elements against altitude based on the midday radiosonde data from the MetService upper station at Paraparaumu Airport. In addition the atmospheric conditions are tested for the occurrence of contrails, and Supersaturation Over Ice for their persistence. There is a chart for each midday sounding from 1 November 2007. Details of the contents of the charts and what they mean are explained in Analysis Chart.

Height Calculator
It is often difficult to estimate the height of a plane because there are seldom any visual clues about size and distance. If it is heavily contrailing, the scale of the contrail (its width) can give a false clue. There are ways to estimate the height of a plane flying directly overhead provided the aircraft type is known. These are based on gross measurements in a photo of the wing span or fuselage length, and the planform of the plane. This utility offers a more elaborate method. Some equipment and organisation are required.

Contrail Calculator
Contrail Critical Temperature Calculator and Contrail Diagnosis will calculate the Contrail Critical Temperature for Flight Levels 360 and 380 based on radiosonde data from any station. Stations in New Zealand and southeastern Australia are easily obtained, but any station's data can be used. It will indicate if, on the basis of the sounding data acquired, contrails will be formed, and what their characteristics will be; short lived (ephemeral) or persistent.

Contrail Bearing Calculator
It is often difficult to determine the direction (or bearing, heading) of a contrail. This utility describes how to make some measurements and calculate the direction to reasonably good accuracy. Of course, you can use this method to measure the direction that a plane is moving, even if it isn't contrailing.

A page full of links to research published over the last 3 decades about various aspects of contrail formation, persistent contrails, transition to cirrus cloud, impact on the weather and climate.