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Abstract
This work is two pronged, discussing 1) the morphology of contrails and their transition to cirrus uncinus, and 2) their microphysical and radiative properties. It is based upon the fortuitous occurrence of an unusual set of essentially parallel contrails and the unanticipated availability of nearly simultaneous observations by photography, satellite, automated ground-based lidar, and a newly available database of aircraft flight tracks. The contrails, oriented from the northeast to southwest, are carried to the southeast with a component of the wind so that they are spread from the northwest to southeast. Convective turrets form along each contrail to form the cirrus uncinus with fallstreaks of ice crystals that are oriented essentially normal to the contrail length. Each contrail is observed sequentially by the lidar and tracked backward to the time and position of the originating aircraft track with the appropriate component of the wind. The correlation coefficient between predicted and actual time of arrival at the lidar is 0.99, so that one may identify both visually and satellite-observed contrails exactly. Contrails generated earlier in the westernmost flight corridor occasionally arrive simultaneously with those formed later closer to the lidar to produce broader cirrus fallstreaks and overlapping contrails on the satellite image. The minimum age of a contrail is >2 h and corresponds to the longest time of travel to the lidar. The lag between the initial formation of the contrail and its first detectability by Moderate-Resolution Imaging Spectroradiometer (MODIS) is ≈33 min, thus accounting for the distance between the aircraft track and the first detectable contrail by satellite. The lidar also provides particle fall speeds and estimated sizes, optical extinction coefficients, optical thickness (τ = 0.35), and ice water path (IWP = 8.1 g m−2). These values correspond to the lower range of those found for midlatitude cirrus by Heymsfield et al. The ice water per meter of length along the cloud lines is 103–104 times that released by typical jet aircraft. The synthesis of these findings with those of prior investigators provides confidence in the present results. Various authors find that contrail-generated cirrus such as reported here contribute to net regional warming.
Received: December 27, 2004; Accepted: June 30, 2005
2. Observations
a. Photograph
At about 1100 LT (1500 UTC) on 7 September 2003 the lead author noticed a series of contrails apparently emanating from some point to the southwest of his residence in Silver Spring, Maryland. Some of these had already been converted to cirrus uncinus with fallstreaks and others were being transformed as he watched. At about 1530 UTC he began to photograph these clouds for their aesthetic interest with no intent to study them scientifically. Thus, he did not record the exact time. Figure 1 was taken toward the south at a central elevation of about 25°. There are four lines of clouds (1–4), and probably a fifth (5), that appear to emerge from the southwest in the lower right corner of the picture. All of these had been contrails during the previous hour as he watched. Otherwise the sky was clear. The youngest of these is obviously 1.
To obtain the geometric structure of the clouds we used a telescope to measure the elevation angles of points X and Y on the building at the left. The azimuth angles were measured with a compass and corrected for the 12° magnetic declination west of true north. Using the 10-km height of the cloud-generating level obtained from the lidar (see Fig. 5) we computed the horizontal scales (L) on the right of Fig. 1 from tan(ψ) = (10/L), where ψ is the elevation angle and L is the horizontal distance from the zenith point above the observer. To estimate distances from left to right across the image use the portion of the scale centered at the appropriate elevation angle. As the elevation angle decreases one sees that the spacing of the cloud lines 1 and 2 is ≈5 km regardless of the angle of view. In short, they are parallel to one another; their apparent convergence is due only to perspective. The same is true for the other cloud lines. We shall discuss the size of the cloud elements later.
3. Interpretation
a. Contrail orientation and spacing
From the Figs. 1, 2 and 3a we have seen that the contrails are oriented toward the northeast. Their spacing is ≈4–5 km. The motion of the base of the fallstreaks is toward ≈58°, consistent with the winds at and below the generating level, and the orientation of the bands.
The horizontal dimension of the tufts in line 1 is ≈1 km and their spacing is also ≈1 km regardless of ψ. The older contrail clouds in line 2 have dimensions of ≈1 by 2 km at all ψ. And the largest dimension of the ice crystal fallstreaks are typically 2 km wide. Similarly, we have seen that all of the prior cloud lines (1, 2, 3) are parallel to one another although their spacing depends upon their relative age, that is, the time between successive aircraft flights.
Originally posted by greenfox83
The put bans on cars that omit too much carbon dioxide. What about these planes?
4. Remarks—Climatic impact
It is interesting that the mean optical depth found in this case (0.35) corresponds to that found in climatological satellite measurements by Ponater et al. (2002) and Minnis et al. (2004), and that the microphysical properties are consistent with a wide range of observations and models by prior authors. Accordingly, it is appropriate to speculate on their effect on climate.
The issue of the impact of contrail-generated cirrus (CS) on climate change has been treated by a number of investigators. Sassen (1997) suggested that the unusually small particles typical of many persistent contrails might favor the albedo cooling over the greenhouse warming. Using a 2D mesoscale cloud model Khvorostyanov and Sassen (1998) computed the distribution of the mean crystal radius, concentration, and ice water content of a contrail after 30 min of development. They found a twofold effect. At the surface, the net greenhouse minus albedo effect was negative with a cooling of 15 W m−2. However, at the top of the atmosphere (corresponding to the entire atmospheric column), the net effect was a warming of 8 W m−2. We note that the latter simulation for the early stage of the cloud produced very large concentrations of small crystals and that the longwave warming would be increased relative to the shortwave cooling with the much larger particles, such as found in the present study.
I have always thought that the most likely explanation for chemtrail flights were experiments at creating artificial clouds with the intent on controlling global temperatures/weather.
Originally posted by JibbyJedi
reply to post by Chadwickus
According to that graph, air travel has increased 50%. These trails use to show up maybe once per month pre 90s, I use to notice them, very rare occurrences based on atmospheric levels that were conducive for them to be sustained.
They have not increased 50%, it's more like 1000% (not an exact figure so lay off).
Originally posted by buddhasystem
Originally posted by greenfox83
The put bans on cars that omit too much carbon dioxide. What about these planes?
Hopefully, very few people get to breath atmospheric air at 33,000 ft.
Originally posted by JibbyJedi
reply to post by stars15k
Contrail Science? Are you serious? I'd trust a DOT.GOV website before I trust anything from them.
I'm not a rookie with these things myself, I've researched all sides of the argument and there are still many holes and a lot of psychological defensiveness coming from the debunkers that doesn't make me feel comfortable with their "facts".
People seem to forget that ANY expert on any topic can be paid to publish anything he's paid to publish, or say on TV.
I don't trust most people on this planet of greed and power mongers, I believe what comes from the heart, not the tainted mind.
These trails are purposeful, and not doing any good to this planet or us.
Originally posted by JibbyJedi
Again I have to say, where were these things pre 1990s? The skies weren't this bad until then, I know because I've been an amateur astronomer-sky watcher all my life. It gets worse as the years go by. We are still waiting for a decent explanation as to their sudden full-on appearances.