|Posted by: polymorph, 3:54 PM GMT on February 07, 2013||+1|
ARM is a DOE facility with the mission to conduct measurements and support research into better understanding the effects of clouds and aerosols on radiation (light and heat) and on climate. At each of the ARM sites is a collection of instrumentation that makes continuous and largely automated measurements of all sorts (see this link for more information). All ARM data is freely and publicly available for download by researchers and anyone else here. This is exactly the approach needed to study such a complex topic as climate and global warming.
Radiosonde measurements (like all measurements) have sources of error, such as imperfect calibration accuracy from the manufacturer, and solar heating of the sensor during the daytime, and slow sensor response at low temperatures, among other things. My method of deriving a correction is to compare radiosonde measurements to measurements from other more accurate instruments, and to do computer modeling of how the sensor responds to changing conditions based on laboratory experiments. Then I write up my method and results and submit a paper to a technical journal, and the editor sends it out for “peer review” where others who are knowledgeable about this area of study scrutinize the paper in great detail and submit line-by-line comments and a recommendation about publishing it. Then I must respond to the editor’s satisfaction about each of the reviewer comments and explain either how I changed the paper to address the comment or why I thought it better not to change it. If the paper is published, it has been “vetted” by experts, and other scientists will use the ideas to make their data better, and someone else will come along one day with a better idea that gives better results and science will again move incrementally forward. If the paper doesn’t pass muster with the reviewers and editor, then the idea probably won’t gain much attention. That’s how science works.
Jet engines emit heat, water vapor and combustion products like soot and sulfate aerosols into the atmosphere, which immediately forms a contrail when the exhaust begins to mix with the atmosphere and cool. Cooling causes the air to become supersaturated and form droplets by condensation on the aerosols, somewhat like the way a glass of ice water will cause condensation of water vapor on the outside, because the thin layer of air next to the glass is cool and the air can't hold as much water vapor at lower temperatures (relative humidity exceeds 100%) so the "excess" water vapor condenses on the glass. What happens to the contrail depends on the atmospheric temperature and relative humidity, and on how much heat/moisture/aerosols are injected (which depends on the fuel type and the engine efficiency). If the atmosphere is very dry then the mixing of exhaust and atmosphere will quickly drop the mixture below 100% relative humidity with respect to ice ("ice-saturation") and the contrail will evaporate in seconds. If the atmosphere is closer to ice-saturation then the contrail will last longer because more mixing is needed to dilute the contrail enough that the relative humidity drops below ice-saturation and the contrail evaporates. If the atmosphere is already at or above ice-saturation, then no amount of mixing will bring the contrail below ice-saturation, it will simply spread and in fact it can grow since the atmosphere was already primed for cloud formation (supersaturated air). These are termed "persistent contrails" and they can evolve into what's called "contrail cirrus".
Yes it does look like contrail cirrus. For sure the linear features with ice crystals falling out. Others that are more isolated puffs may be "cirrus uncinus", which form the way cirrus normally do, by the air being cooled by one or another mechanism until the humidity reaches the "homogeneous nucleation threshold", which is approximately 150% relative humidity with respect to ice. Substantial supersaturation is needed for cirrus to form this way, as opposed to "heterogeneous nucleation" where ice crystals form directly on some solid aerosol particle at lower supersaturations.
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|Posted by: polymorph, 7:25 PM GMT on January 04, 2013||+0|
|Posted by: polymorph, 7:21 PM GMT on January 04, 2013||+0|
|Updated: 7:23 PM GMT on January 04, 2013||Permalink | A A A|
|Posted by: polymorph, 12:30 AM GMT on January 02, 2013||+1|
|Updated: 12:31 AM GMT on January 02, 2013||Permalink | A A A|
|Posted by: polymorph, 5:56 PM GMT on December 29, 2012||+0|
|Updated: 6:00 PM GMT on December 29, 2012||Permalink | A A A|
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