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Your comment "isn't as useful " is somewhat of an understatement - it all looks like gibberish to me. :?
Indeed. There is a key to the data in the help files, but it takes a bit of looking back and forth to get a feel for what all the numbers mean. As I say, it's nice of MetVUW to do the decoding.
John Anderson wrote:
What could be extremely useful would be the availability of an accessible database of met-info for say the last 6-8 years or so with, in particular, upper tropospheric temperature and relative humidity measurements. Do you, or anybody else, know of one?
NIWA probably provide this data as part of their climate database. Try getting in touch with Jim Salinger, he'll let you know exactly what datasets are available.
What could be extremely useful would be the availability of an accessible database of met-info for say the last 6-8 years or so with, in particular, upper tropospheric temperature and relative humidity measurements. Do you, or anybody else, know of one?
Select "South Pacific" as the Region (not New Zealand).
Select "Text: List" for Type of Plot, and select the date and time range.
Click on the station and the data will appear, or type the station number at botton left and press Enter.
Radiosond stations in New Zealand are Whenuapai (93112), Paraparaumu (93417) and Invercargill (93844).
The other stations on the NZ map are wind only stations.
You will need to collect all the data over 6-8 years and do your own analysis.
Or you can get a plot over any part of the earth of monthly mean temperature for any month and any pressure level over any year range from the NCEP Re-analysis site. http://www.cdc.noaa.gov/cdc/data.ncep.reanalysis.html
Joined: 05 Nov 2003
Posts: 387
Location: Auckland, New Zealand
Posted: Wed Jul 26, 2006 10:03 pm Post Subject:
Many thanks jaygee and Hector for your suggestions and links...
The University of Wyoming database seems to be just what we require, in fact it seems most excellent. :-)
Quote:
What would you use this information for?
One purpose, Hector, is to link the occurrence of Persistent Contrails with a specific range of atmospheric criteria. As you are no doubt aware, sometime in the 1990s the Schmidt Appleman Criterion stopped working as a predictive tool for formation of PTs. We're trying to understand how PTs can now form in locations and in conditions that once were not possible. In the Far North, for example, in mid summer...
As you are no doubt aware, sometime in the 1990s the Schmidt Appleman Criterion stopped working as a predictive tool for formation of PTs.
No I was not aware of that. Do you have a reference to the paper that reveals this.
Quote:
We're trying to understand how PTs can now form in locations and in conditions that once were not possible. In the Far North, for example, in mid summer...
I find this hard to believe... mysterious even. How can a region of New Zealand be somehow exempt from the Laws of Thermodynamics?
The Clausius-Clapeyron equation is true everywhere.
http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch14/clausius.php
Have you got some date and times when this happened or didn't happen? I will check it out... as best I can.
No I was not aware of that. Do you have a reference to the paper that reveals this.
We do have some material on this - we'll need to dig out the relevant documents again and will post links to them as soon as we can...
Hector wrote:
Have you got some date and times when this happened or didn't happen? I will check it out... as best I can
We are currently putting this data together - again, we will post as soon as possible.
We do believe that there are some genuine mysteries here and we have a sincere desire to understand the processes at work.
You are obviously aware of the discussions on this website relating to contrails and also what are referred to as 'chemtrails' and no doubt have read over some of the past threads...
We would appreciate and value some input from someone with your level of expertise. (Forgive us for being cautious - presumably, you are for real and your motives and interest may be trusted? We have had experience on these forums of folks who are not what they purport to be...)
We have been researching these occurrences for over three years now and have seen (and photographed) things in the skies over New Zealand that are truly anomalous. We are preparing written material about these matters, from our own experience and the experience of others, many of them on this forum. This will be published in due course as it reaches an appropriate level of readiness.
The Far North is of particular interest to us. We have been going there as a couple for at least sixteen years, mainly during summer months. It wasn't until the year 2004 that we saw persistent contrails up there. If you want to do some initial research, here are some dates to work with...
First occurrence in the real Far North (apparently over the Northern end of 90 mile beach):
January 17th 2004: From around 11:40 am to 2:30pm
Persistent contrails in all directions, planes making patterns and leaving persistent and spreading contrails
Again on February 24th 2005 on the Karekare Peninsular: 10:50 am onwards thoughout the day
Not just one or two persistent contrails, but dozens over the course of a week in locations we had never, ever seen any contrails before (persistent or otherwise) in almost two decades...
We've been trying to find the original material on investigations into why the Schmidt Appleman Criterion 'stopped working'. It's been quite some time since we looked at the subject - due to various events, our life got very hectic over the last 12 months or so and it's only now that we're getting back into the whole subject...
This is the document we have been trying to locate - the initial research on why the Schmidt Appleman criterion had become unreliable as a predictive tool:
"New techniques for Contrail Forecasting" by Captain J L Peters 1993 - Air Weather Service, Scott Air Force Base, Illinois
Peters (1993) performed a validation study of the Appleman (1953 , 1957) contrail forecast method using a large database of U.S. Air Force contrail observations. Peters found that the Appleman method correctly forecasted the occurrence of contrails in less than 30% of the cases below 12.19 km (40000 ft). Peters attributed this result to the fact that modern high-bypass jet engines emitted less heat per mass of water vapor emitted. He proposed engine-specific corrections to the contrail factors for low-bypass, high-bypass, and nonbypass engines to account for these differences. This approach differed from that of Appleman (1953) , who recommended the use of a single contrail factor for all jet aircraft based upon a study of typical jet engines in use at that time.
Busen and Schumann (1995) also showed that the contrail factor varies as flight parameters change and that the use of a single contrail factor for all modern jet aircraft is not appropriate.
It should be remembered that because of his links with the Intergovernmental Panel on Climate Change, Ulrich Schumann is somewhat of a controversial figure. The IPCC itself is controversial and is seen by many as a vested interest run organisation which falls in line with government policy makers and other vested interest groups. The organisation has fallen foul of many serious scientists - but this is perhaps a topic for another time...
As coordinating lead author of Chapter 3 "Aviation-Produced Aerosols and Cloudiness" of the IPCC Assessment "Aviation and the Global Atmosphere" in 1998/1999, Schumann's statements in the report were hotly disputed at the time.
Schumann has justified there not being a modern predictive model to replace the Schmidt Appleman criterion, which has now proven to be unreliable. So there are no charts for us to refer to such as the Appleman charts, examples below.
Basic Appleman Chart (in use for over 5 decades)
Temperature Profile: Mid Latitude (NZ) Summer
Temperature Profile: Mid Latitude (NZ) Winter
Using the graphs: The two most important lines on the chart are the 0 percent relative humidity line and the 100 percent relative humidity line. If the atmosphere were colder than the temperature indicated by the 0% line, a contrail would form even if the relative humidity of the atmosphere were zero. By itself, the airplane will supply enough moisture to make the contrail, and no moisture is necessary from the atmosphere to form the cloud. According to the chart, contrails will always form when the temperature profile is to the left of the 0% line. If the atmosphere were warmer than the temperature indicated by the 100% line, a contrail could not form even if the relative humidity of the atmosphere were 100 percent. The combined moisture from the jet exhaust and the atmosphere will never be enough for the mixture to produce a cloud. Temperature profiles to the right of the 100% line will never form a contrail. For temperatures between the 0% and 100% lines, the possibility of a contrail forming will depend on the atmospheric moisture, represented on the chart as relative humidity. A contrail may or may not form when the temperature is between the 0% and 100% lines.
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We're not disputing the laws of thermodynamics here Hector, we are trying to understand when people report persistent contrails, what are the associated atmospheric conditions? What is normal, what is not normal? Normal contrails need certain atmospheric conditions to form. However a plane spraying hydrophilic aerosols can create persistent contrails in any atmospheric conditions, certainly in relatively low temperatures and low RH.
It's interesting that the Schmidt Appleman criterion is still being disseminated and even provided as a student resource by NASA, even though they know it's unreliable:
Quote:
The US Air Force conducted studies to test the accuracy of the Appleman chart. Military pilots sometimes remark in their flight reports whether or not contrails form during their flights. Using these reports and observations of temperature, pressure and relative humidity, the USAF found that the forecasts using the Appleman method were correct about 60 to 80 percent of the time. Looking more closely at the data, they found that when no contrails were forecast, the forecast was correct 98 percent of the time! However, when contrails were forecast to occur, the forecast was correct only 25 to 35 percent of the time, and often failed to predict the occurrence of contrails. Thus, the Appleman chart tends to underpredict the occurrence of contrails and to overpredict the non-occurrence of contrails. For this reason, the USAF is actively investigating better ways to compute contrail formation.
Source: NASA
We don't have a scientific background and much of this stuff is a lot to wade through and requires persistence - but we do our best. We want to eventually create a resource for people to use, that will enable them to be more discerning about what they see in our skies...
Ah, yes, the literature is not with out some controversy. After you have got the basic physics correct, you need good data.
You need to know the moisture content of the environment. The temperature is also important, but that is easy to measure to sufficient accuracy with standard radiosonde equipment operated by the meteorological people. RH at low temperaures is not so easy, and below about -30 or -40 some sensors just do not work as well as at higher temperatures (where I suppose it is more important to have some knowledge of the RH).
The other important variable is the so called "contrail factor" which depends on the characteristics of the particular jet engine and the power setting during flight at the time.
This determines the location (left or right) of the lines on the Appleman charts.
I do not think that the basic method has "stopped working"; it is basic thermodynamics. The problem is with the data - the variables in the situation.
These phenomena you see in the sky are genuine jet exhaust condensation trails. No one is spraying chemicals. The medical symptoms, electric shocks, etc, you may associate with seeing contrails are caused by something else. There are certainly contrails on overcast days and you do not see them.
I am working on something, and I will put it up when it's ready.
They look like condensation trails. Nice ones, too.
Could you annotate each photo with the date that it was taken? Then we can have a look at the Paraparaumu upper air data for that day and make an objective assessment.
Joined: 05 Nov 2003
Posts: 387
Location: Auckland, New Zealand
Posted: Mon Aug 07, 2006 7:59 pm Post Subject:
Hi Hector,
Rereading your reply, I'm not too sure that you actually followed the link that Deano posted, probably thinking that he was directing you to the photographs on his gallery. His link actually goes to a video, which is already annotated with date and approximate time...
