Mysteries, Chemtrails, Aerosols :: Mysterious NZ

[John Anderson]

Hector has published a Contrail analysis chart in answer to this statement:

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...

[Hector]

Thank you, John, for recovering my poor effort at an attempt to put these images in the Gallery section with notes, etc.

I have several more for the dates of some of the photos of contrails, or references to contrails elsewgere on this site.
This (above) is the first one. Unfortuately it is a problematic one amongst a number of good examples (see below) of how well the Appleman method works in explaining/predicting the phenomenon considering the problem of unknowable data.

One problem is that the radiosonde stations are often some distance away from where the contrails are observed, as in this case. I plotted the temperature at 300 hPa at midday on 17 Jan 2004 NCEP Reanalysis Project site), and it is about 1 degree WARMER over the Far North, which lifts the lower boundary for contrails a few 1000 feet. This is my main ploblem with this case. Are you sure the date is correct?

You asked about there being no moisture data above 30000 feet. This is because the RH sensor on the equipment used at Whenuapai (and many other locations) is unable to measure when the temperature is below about -40 degC. I am sure there are sites on the Internet about the performance of radiosondes. (Vaisala in one of the main manufacturers.)

The critical temperatures in my analyses assume a contrail factor of 0.039 g/kg/K which is used by Mark Schrader for high bypass jet engines in his 1996 "Calculations..." paper in JAppMet. More modern engines may have a higher CF than this now. A higher CF effectively raises critical temperature, and lowers the altitude for the occurrence of contrails. This is one of the unknowables until reliable engine data is published.

In this problematic case, I am unable to comment about persistence of contrails and so on... Except to say that there is essentially no difference between a transient and a persistent contrail. It is a matter of the the moisture content of the exhaust as is slowly dilutes by mormal mixing and advection (carried by wind) processes in the upper troposhere.

That image was created using an MS Excel spreadsheet I have created and using data from the Wyoming upper air data site (see a post elsewhere - in this thread possibly).

Other cases I have looked at are much more successful than this one... such as your sighting on 24 Feb 2005, one by your team in Nelson on 2 Apr 2003, mine on 25 Jul 2006 in Wellington, and the contrails in the satellite image on 8 Jun 2006 east of the South Island.

I am so disspointed that the first (and only) case I managed to upload is a bit of a problem from the stand point of "These are just contrails". I hope your readers will be patient and make a judgement when they have seen the results from other cases.

There seems to be a variety of issues surrounding the existence of contrails. Perhaps someone could clearly and succinctly describe what the concerns are... That they appear at some times and not others, Chemicals, un-scheduled flights, exhaust products, etc.

Thanks again, John.

[Melody Anderson]

[Hector]

OK, Melody, I can't argue with the tecnology... the date is correct. Thank you for confirming that for us.

Now what? I have already conceded that the temperature in the Far North at 35000 feet was about a degree warmer than at Whenuapai. This effectively raises the lower boundary of the contrail zone. But all is not lost. What about the moisture? The radiosonde can't measure it at these low temperatures.

Take a look at the Landcare sattelite picture for that day.
http://satellite.landcareresearch.co.nz/noaa/?history=2004/jan/md17014.txt
In this picture you can see what looks like contrails, but more important there is plenty of high cloud in the area, and to the west... there is probably a low pressure out there in the middle of the Tasman Sea.

This indicates that the RH is probably very high, even at these altitides. There was probably a fair amount of (non-contrail) cirrus in the western sky indicating the presence of plenty of moisture. Any photos taken that day in that area will confirm my guess.

High RH has the effect of raising the critical temperature (moving it right in the graph) and lowering the lower boundary of the contrail zone. This is because its intersection with the 1-degree warmer (a few pixels right) environment temperature line will be at a lower height. So, I reckon that the lower boundary for contrails could be as low as 35000 feet.

This is within the usual cruise altitude range for jet planes, and contrails will have been visible, and persistent (because of the high RH), if planes were flying above that altitude that day. The only thing we don't really know is the actual height that the plane(s) were flying. They are highly likely to be a normal passenger jets flying at normal heights for passenger jets.

So, having taken the trouble to check out a satellite image for some clues about the likely moisture content of the environment, I am much happier about this case. :D

Normal jet exhaust contrails confirmed! QED

[John Anderson]

Hi Hector,

[Hector]

Hello John,

Thank you for the photos, satellite images and comments.

To answer a few of the points you raise about that day...

The haze, and most of the haze occurring in New Zealand (which is obvously not smoke-haze and other man-made pollution), is salt haze from the sea. This is the remains of sea spray where the water in the droplet has evapourated. There will have been a storm at sea somewhere upstream (up air-stream). Tiny salt particles remain and this is the haze. It will eventually settle to the ground or be "washed" out of the air by rain. Some days you find it on your car or your house walls and windows. Taste it - salty. Wash it off - it will shorten the life of your nice paint work. It is part of living in a maritime country.

I am certain the low level wind was from the east-northeast. The satellite images, N0 8 and No 9, show a good example of cumulus 'cloud streets' originating on the east coast and ending several kilometres off the west coast. This cloud pattern is well known worldwide, and well understood. This is a common occurrence over Northland, Waikato and Bay of Plenty, and other places as well.

Your photos show a gradual invasion of the sky from the west by the cirrus originating from the low pressure weather system developing in the Tasman Sea, as I suspected they would.

I suppose cumulus clouds do appear 'out of nowhere' in the sence that the one you observed did not develop somewhere else and get carried there by the wind.

What is "White Sky" effect? The sky is filling with cirrus from the storm in the Tasman Sea and the spreading out of contrails. There was probably a jet stream at the cirrus height and the horizontal wind shear whould have spread the cirrus and contrails out quite a lot. These are all normal and natural processes.

Photo No 11:
The Mt Taranaki - Nelson cloud feature may well be a condensation trail. The Paraparaumu sounding that day probably shows that contrails were possible at normal jet cruising heights. I have't checked, but anyone could.
(At some stage I will describe a simple method for doing this that does not require a 175KB spreadsheet with macros.)

Where do you draw the line between transient and persistent contrails? Thermodynamical considerations do not suggest anything in that regard.
There is an old saying in Rugby that forwards win matches and backs decide by how much. There is a paralell with contrails.
The temperature (mainly) determines if contrails will be visible, and the humidity determines for how long. :)

Cirrus Aviaticus?? - I don't think "Aviaticus" is part of the fomal system of cloud nomenclature and classification.
I searched on Google for the term and as far as I cared to check it only occurs on "Chemtrail" pages.
Google: Cirrus Aviaticus found 470-odd pages.
Google: cloud nomenclature found 437000 pages.
Google: cloud nomenclature + Aviaticus found none.

What is the importance of establishing the air route that the contrail represents? Is it not sufficient to establish that the atmospheric conditions were suitable for contrails and therefore that is what these clouds are?

As for my analysis in this case, I feel it was complete at the end of my last post. The conlcusion was (and still is) normal contrails from normal jet planes, and that the contrails would be persistent due to the high humidity as evidenced by the presence of natual cirrus. :D

One point of clarification about the time of the temperature sounding: the time of the data from the University of Wyoming site is given as 2100Z (meaning 2100 UTC) on the previous day. I have converted that to the local time by adding 12 hours (ignoring daylight saving).
The coded message containing this data has a nominal data time (0000 UTC or 1200 UTC) and the release time (near 2300 UTC and 1100 UTC).
In summer we are on Daylight Saving time, 13 hours ahead of UTC. In summer the radiosonde flight is released at 11 o'clock local time, so the coded release time will be near 2200 UTC and 1000 UTC. I suspect the Univerity of Wyoming sets the data time by rounding to the nearest 3 hours of the release time. :?
So that is why you get 09:00 NZST for what is the "midday" sounding and 21:00 NZST for the "midnight" sounding in summer. In winter they will be 12:00 and 00:00 NZST, respectively.

I will make post about the next case (24 Feb 2005) when the image has been approved. :wink:

[Hector]

John and Melody, in a post timed Wed Jul 26, 2006 11:17 pm
(see https://www.mysteriousnewzealand.co.nz/forums/viewtopic.php?t=634 ) said "Again on February 24th 2005 on the Karekare Peninsular: 10:50 am onwards thoughout the day".




The graphs are for Whenuapai at midday and midnight 24 Feb 2005 temperature soundings.

Contrail height range: 35106 to 60040 feet.

There is no moisture information above 30000 feet, so the lower boundary is likely to be 1-2000 feet lower. If there was a lot of moisture (look for cirrus nearby in satellite images or photos) then the contrails will persist for long periods.

The lower boundary is below the usual cruise height range for jet aircraft, and contrails would have been visible, possibly for hours.

:D

[Hector]

You will need this table of Critical Temperature for contrails by height (in pressue) and RH.

Critical temperatures for a contrail factor of 0.0390 g/kg/K (high bypass)

Pressure / RH


       0%    10%    20%    30%    40%    50%    60%    70%    80%    90%   100% 


200 -53.85 -53.51 -53.15 -52.74 -52.30 -51.79 -51.20 -50.50 -49.62 -48.35 -44.57 


250 -51.77 -51.43 -51.05 -50.64 -50.18 -49.67 -49.07 -48.35 -47.44 -46.15 -42.28 


300 -50.04 -49.69 -49.31 -48.89 -48.42 -47.89 -47.28 -46.55 -45.63 -44.31 -40.36 


400 -47.23 -46.87 -46.48 -46.05 -45.57 -45.03 -44.40 -43.65 -42.69 -41.34 -37.27 


500 -45.00 -44.63 -44.23 -43.79 -43.30 -42.74 -42.10 -41.33 -40.35 -38.97 -34.80 

Ref: Part of Table A4, Appendix, "Calculations of Aircraft Contrail Formation Critical Temperatures"<br>
Mark L. Schrader<br>
http://ams.allenpress.com/amsonline/?request=get-document&issn=1520-0450&volume=036&issue=12&page=1725
(I tried a nice html table here but the preview showed all the html tags. Luckily 'pre' tags seem to be acceptable.)

Next you need the data from a radiosonde sounding at a time and station close to your sighting.

Let's check out what looks like contrails in the day-time satellite impages posted by John Anderson (above).

Go to the Wyoming upper air data site and get the data for Paraparaumu at midday 17 Jan 2004.
http://weather.uwyo.edu/upperair/sounding.html
You need to enter a time range from 16/12Z to 17/00Z in Jan 2004 to capture the sounding at 2100Z 16 Jan 2004.
See my explanation about the data times of this data a few posts up from here.

Here is the link for that station and date.
http://weather.uwyo.edu/cgi-bin/sounding?region=pac&TYPE=TEXT%3ALIST&YEAR=2004&MONTH=01&FROM=1612&TO=1700&STNM=93417
If you are canny you can use this and edit it for the date range you want and the station.
(93112 for Whenuapai, 93417 for Paraparumu and 93844 for Invercargill.)

This is what the data looks like:

93417 NZPP Paraparaumu Aerodrome Observations at 21Z 16 Jan 2004


-----------------------------------------------------------------------------


   PRES   HGHT   TEMP   DWPT   RELH   MIXR   DRCT   SKNT   THTA   THTE   THTV


    hPa     m      C      C      %    g/kg    deg   knot     K      K      K 


-----------------------------------------------------------------------------


 1022.0     12   21.2   12.2     56   8.80    265      5  292.5  317.9  294.1


 1012.0     95   19.4    8.4     49   6.88    302      6  291.6  311.5  292.8


....

The bit you want is down here between 400 and 200 hPa.

....


  400.0   7470  -24.3  -49.3      8   0.11    185     32  323.3  323.8  323.3


  391.8   7620  -25.8  -48.1     10   0.13    185     32  323.3  323.8  323.3


  376.0   7918  -28.7  -45.7     18   0.17    187     36  323.3  324.0  323.3


  317.0   9121  -38.1  -51.1     24   0.11    193     51  326.4  326.8  326.4


  300.0   9500  -40.1                         195     56  328.7         328.7


  260.0  10460  -46.3                         203     62  333.3         333.3


  250.0  10720  -46.1                         205     64  337.4         337.4


  243.0  10910  -45.9                         205     64  340.4         340.4


  240.7  10973  -46.1                         205     64  341.0         341.0


  200.2  12192  -50.9                         205     83  351.9         351.9


  200.0  12200  -50.9                         205     81  352.0         352.0


....

Notice the RH dropping out when the temperature is too low for the sensor to work reliably.

Anyway, on a bit of paper, note down the pressure, height, temperature and RH for 400, 300, 250 and 200 hPa.

 


   PRES   HGHT   TEMP   RELH


  400.0   7470  -24.3      8


  300.0   9500  -40.1      ?


  250.0  10720  -46.1      ?


  200.0  12200  -50.9      ?

Now make another column for the height in feet. (Multiply the height in metres by 3.2801.)

 


   PRES   HGHT   TEMP   RELH   H ft


  400.0   7470  -24.3      8  24508


  300.0   9500  -40.1      ?  31168


  250.0  10720  -46.1      ?  35171


  200.0  12200  -50.9      ?  40026

Now use the Critical Temperature table (above) for High Bypass jet engines to find the CT for each pressure level.
Where there is no RH in the sounding just guess a value like 80% since we already know there was lots of high cloud that day.
Enter the CT in your little jotting.

 


   PRES   HGHT   TEMP   RELH   H ft     CT


  400.0   7470  -24.3      8  24508 -46.87


  300.0   9500  -40.1    ?80  31168 -45.63


  250.0  10720  -46.1    ?80  35171 -47.44


  200.0  12200  -50.9    ?80  40026 -49.62

Look! The observed TEMP goes below the tabulated CT somewhere between 35171 and 40026 feet.
Guessing half-way, 37000 feet is a very plausible height for a jet plane in cruise. So, what you see in the satellite picture are most likely condesation trails from jet planes.

Too easy. :D
"The truth is out there" for all to access for themselves.

[John and Melody]

Some responses to points raised in this topic:

Ah Sunday, finally got some time to address your prolific correspondence, Hector. :-)

It certainly has been most instructive seeing a professional at work, how you go about using atmospheric data, satellite maps and how you create your charts. Yes, most educational, valuable...

Now with regard to our Far North observations of the 17th January 2004, we have never believed it scientifically impossible for contrails to have formed on this occasion, clearly that would be illogical. We saw them form, they existed and the process must somehow adhere to the physical laws of the universe. We might think that your data does tend to indicate that the prevailing conditions were rather marginal for the formation of persisting, spreading contrails. We may also wonder how such things can now be, but it is probably not something we could pursue in communications with you with any prospect of a resolution.

Our enduring interest in this particular event is only partly due to the contrails themselves. It has to be said though, that it was quite a dramatic occurrence for us, as it was the first time we'd seen persistent trails so far North. Despite visiting the North on over one hundred occasions (no exaggeration) at all times of the year and including weeks onboard charter launches cruising as far North as The Three Kings Islands, we had collectively never seen one contrail. Not one. Now, of course, on every visit (with a clear sky) we see dozens of both persistent and 'transient' trails (good term that, must use it from now on - thanks Hector). Without exception the trails also indicate aircraft flying on vectors that accord with the vector map for international flights produced in a previous post in this thread. Undoubtedly normal aircraft, going about their normal business.

On that day in question though, the trails did not seem to be from normal aircraft going about their normal business. Not at all. We saw the trails heading across the island, both ways, doubling back, doing circuits, forming crosses - most mysterious... It also has to be said that during this day we also did see trails off the West coast that were representative of the vectors of normal commercial flights, though none off the East coast.

It was not the epiphanic event that our experiences of April 2003 represented, where we saw the mysterious Black (or Grey) Beam and other strange stuff associated with what seemed to us to be a Chemtrail operation, but it non-the-less represents true strangeness to us, even two and a half years later.

So, hopefully the above has explained our 'persistent' interest in this particular days event. It is not something that you are expected to provide an answer to, it is a little outside of your field, and besides, you only have your data to go on, you were not there to experience the event first hand.

With that out of the way, we can address some other issues raised by your previous posts...

[John Anderson]

Hi Hector,

I am actually quite keen to have your opinion on this question from an above post.

[Hector]

I posted the work-it-out-in-your-head method using the Paraparaumu sounding on that day as the worked example. The result is that jet exhaust condensation was possible that day for jets flying in the vicinity of 37000 feet.

So it could well be from aviation activity. It is not possible to say for certain, and I am not going to venture a firm opinion. There is not enough information. There is precious little as it is! What is the height of this cloud, for instance. If we has some idea of its height, or if there are photos of a jet producing a contrail on a track parallel to this cloud feature, we could be more certain.

As you observed up north, the wind acts on these as soon as they form, just as the wind messes with any bit of cloud. It gets moved, streached, contracted, distorted, etc. Fairly soon the super cooled water freezes and the ice starts falling and you begin to see Cirro-filum and other forms, as you did. Eventually these become indistinguishable from natural cloud as you said.

The other thing is that each jet that flys through, raises the RH a little making it that much easier for the next jet exhaust to condense. In those cold temperature it does not take much water vapour to raise the RH a considerable amount.

What I am trying to convey is that there are sound methods (that work) to at least determine on any day and in almost any location if jet exhaust condenstation is possible or not. From that point of information and knowledge one can rationally consider any issues that may be important.

There may be none. :idea:

[Deano]

Hector,

Chemtrails are real whether you like it or not. It may be that in the area you come from there are no ' operations ' prevalent hence your textbook views of the issue. When youve seen what Im seeing around my home you know its not natural aircraft emmissions, the switch on switch off spraying is obvious. Hot engine vapour moving through cold temperatures doesnt add up. Most of the people on this website know somethings going on. Your science, though noble is a futile exercise.

Welcome anyways :wink: I am interested in your information all the same.

[Hector]

Thanks for your opinion there, Deano. Futile or not, I am pressing on...

I said earlier that I would put up my analyses of selected contrail cases... Nelson, Canterbury, Upper Hutt and Fielding (This is the one in your video, Deano).

Starting with Nelson in April 2003, here is the analysis chart for Paraparaumu.



Yes, I have pimped m'charts!

Now is a good time to explain various parts of these Contrail Analysis Charts.
The vertical scale (left) is in metres. The sounding data gives the temperature and other data with the height as a pressure as well as the physical height in metres. It is this height scale that everything is plotted against.
The horizontal scale (-80 to 20) is in degrees Celsius for temperature. This scale doubles as the (un-labeled) RH scale from 0 to 100%.
The slanting blue box represents the range of the Contrail Critical Temperature. This temperature depends on the Contrail Factor, the pressure, and the RH at that pressure level. In all of these I have used a Contrail Factor of 0.039 g/Kg/K which is what Mark Schrader uses for high bypass jet engines in his paper "Calculations of Aircraft Contrail Formation Critical Temperatures".
http://ams.allenpress.com/amsonline/?request=get-document&issn=1520-0450&volume=036&issue=12&page=1725
When the RH is zero, the Critical Temperature is at the left (cold) side of the box. When the RH is 50%, the Critical Temp is at the line in the left-centre of the box, and when the RH is 100%, it is at the right (warm) side of the box.

On the right is another scale showing selected flight levels and their corresponding (nominal) pressures in the International Standard Atmosphere.
It's beyond the scope of this little dissertation to explain the importance of the ISA in aviation except to state that "flight level" (expressed in hundreds of feet) refers to a pressure level, and it is the height (in hundreds of feet) of that pressure level in the International Standard Atmosphere. For example, in a real atmosphere F340 may be above or below 34000 feet, but it will always be at a certain pressure near 250hPa. From chart to chart, this scale will move up and down a bit because the chart is a representation of a real atmosphere which may be warmer or cooler than the ISA.

Back to the chart. The two thin white lines represent the normal jet transport operating altitude range which is approximately F300 to F390. Planes do operate above and below this range but mostly within it. The thick white vertical lines represent the ranges of altitiudes where contrails will form if high bypass jet engines are operating there. These lines are labeled with the physical height (in metres) and the flight level (meaning a pressure level).

There are two more lines plotted on the right of the chart. The dark blue one is the vapour pressure (of water vapour). This is the RH times the saturation vapour pressure with respect to water. It is another measure of the moisture present in the environment. The purple line is the saturation vapour pressure with respect to ice. The units of both are Pascals (or hundreds of hectopascals, hPa x100), and plotted in the temperature scale (from 0 to 20) for convenience. The importance of these in this context is that if the environment vapour pressure is greater than the saturation vapour pressure with respect to ice, then contrails at that level will be persistent. See "Calculations of Aircraft Contrail Formation Critical Temperatures" referenced above for more on that, especially see the figure at
http://ams.allenpress.com/amsonline/?request=display-figures&name=i1520-0450-36-12-1725-f02
(non-persistent and persistent contrails diagram and explanation).

While these charts are usefull, care must be taken because of the limitations arising absent or incomplete information. Such as:

The temperature at the altitude of the observed contrail may be different by a few degrees from the temperature at the same height over the radiosonde station.

The altitude of the plane may not be known.

The Contrail Factor of the jet engine may not be 0.039 g/Kg/K.

The RH may not be available, or may be in doubt due to measuring difficulties of some types of radiosonde equipment

These charts were built in MS Office 2000 Excel. A Python script is used to condition the sounding data (limit RH to 100 or less and insert any standard pressure levels that may be missing). The spreadsheet uses macros to load the sounding data files, find the Critical Temperature / environment temperature crossing points, re-title the chart and export it as a GIF image.

Now, about this particular Contrail Analysis Chart...
Contrails were observed and photographed by some contributors from Nelson Airport. See John Anderson's post on Sat Jul 29, 2006 1:21 am ( https://www.mysteriousnewzealand.co.nz/forums/viewtopic.php?t=627 )

The graph is based on the Paraparaumu midday 02 April 2003 upper air data.
Contrail height range is F324 (9977m) to F420 (12910).
There is no moisture information above 370hPa, so the Critical Temperature will be warmer than shown, and the lower boundary for contrails is likely to be 1000 metres (or more) lower, and the height range deeper. (The RH trace goes to zero because there is no data, so ignore that part of the trace.) A lot of natural cirrus (and I think there was that day from the photos) would indicate that there was a lot of moisture at that level.
We do not know the height that the planes were flying but the lower contrail boundary is near the usual cruise height range, so jet aircraft would have been producing contrails. These probably would have lasted a long while due to the high humidity there.

The Canterbury, Upper Hutt and Fielding cases will follow.

[Hector]

I observed a contrail from Upper Hutt at 5:35pm 25 July 2006
See the top post at https://www.mysteriousnewzealand.co.nz/forums/viewtopic.php?t=625



The graph is for Paraparaumu at midday 25 July 2006
Contrail height range: F288 (8760m) to F509 (15318m)
The lower boundary for contrails is below the usual cruise altitude range, so jet aircraft would have been producing contrails.
The contrail was very transient because the humidity was fairly low at the height the plane was flying. I guessed 28000 feet. Well, it could have been a bit higher, but I doubt is was above 35000 feet where the RH was greater and the contail would have lasted a bit longer.

[Hector]

Extensive and persistent Contrails were observed by Hieronymous Bosch from Chrstchurch (and others elsewhere) on 8 June 2006.
See the post at https://www.mysteriousnewzealand.co.nz/forums/viewtopic.php?t=621 where he says "on june 8th, one of the biggest chemtrail operations was being conducted. several others here on the north island also said that activitiy was extremely heavy (smash, deano, and others)."





These graphs are for Paraparaumu and Invercargill at midday 8 Jun 2006.
Contrail height ranges at the two locations are annotated in the charts.
The lower boundary for contrails is well below the usual cruise altitude range, so jet aircraft would have been producing contrails. The humidity was fairly high around F340 to F390 especially towards Invercargill around F340, so the contrails could be expected to take a long time to dissipate, days perhaps. Look at the traces on the right. the vapour pressure (dark blue) is greater than the saturated vapour pressure over ice (purple) at Invercargill, and so close to crossing in the Prarapraumu sounding that you can't tell. Contrails would never dissipate by mixing with the environment. That is what Persistent means in this context. See references to Mark Schrader's paper in the post above that explains these charts.

This is an excellent example of how this vapour pressure thing works, and the ground observations that back it up.

Thanks Hiero, Smash, Deano and the others for recording and commenting on the instance.

[Hector]

Paraparaumu midday on 19 October 2006



This chart contains the data from the Paraparaumu radiosonde at midday (not 9am) on 19 October 2006. The Wyoming site has timed the data at 9am and I haven't changed the data time.
This is the day that Deano made a video of a horizon to horizon contrail from Fielding. Here is the link if you want to see it again.
http://www.mysteriousnewzealand.co.nz/photogallery/displayimage.php?album=43&pos=1

The contral layer extends from F292 (8941 metres) to F406 (12364 metres) or 29200 to 40600 feet as pressure levels in the ISA. This neatly spans the usual height range of jet planes, so you could expect to see contrails on this day over central New Zealand. Actually, the VP and SVPi are so close between F300 and F340 that the contrails could reasonably expected to be persistent for a long period.

So thanks Deano, for bringing this excellent example of jet exhaust condensation to our attention, and documenting it so well on video.

[Hector]

Medford, Oregon, USA, 4pm 7 July 2006 PST



At 1337 Sun 06 Aug 2006, thelawnguy posted "Caught In The Act...Enemy Aircraft!!! I took these on 7/7/2006 over Eureka, Ca"
https://www.mysteriousnewzealand.co.nz/forums/viewtopic.php?t=640
Medford near the Oregon/California state line is the closest radiosonde station to Eureka which is in northern California. The time label in the chart is midday 8 July 2006 NZST which is the same time as 4pm 7/7/2006 Pacific Standard Time. My charting system is not perfect - it doesn't cope with any time zone other than NZST, not even daylight saving.

In this case there are two contrail layers: one is from F343 (10954 metres) to F424 (13433 metres), and another up near F500 (15 to 16 kilometres). The lower layer is in the top of the normal cruising height range for jet aircraft, and so you can expect planes flying there to produce contrails. At F340 the VP and SVPi are pretty close, so contrails formed there will be persistent.

Thanks lawnguy, for providing the opportunity to check out a foreign case on this site.

[Hector]

These two are interesting cases from Tucson, Arizona, USA. They are posted on the watchthesky.org Internet site at
http://watchthesky.org/chems/trailimage.htm
linked from http://watchthesky.org/chems/evidence/evidence.htm
and purports to be evidence that jet exhaust condensation is NOT possible, yet there are the photos, and there is a link to a copy of the sounding data from the Wyoming site.
So I checked it out using my analysis chart, and here are the results...



Tuscon 7 April 2006, 1200 UTC (which is 0000 NZST 8 Apr)
There are 3 contrail layers here, and the important one is from F336 to F400. Jet planes fly at that altitude, as these ones probably are in the photos. What is more contrails will be persistent near F370 where the VP and SVPi are so close together, so persistence at that altitude.
Remarkable! Contrails ARE possible!

Two days later (probably all the time between as well)...


Tuscon 9 April 2006, 1200 UTC (which is 0000 NZST 10 Apr)
The temperature has lowered at 12.5 km and 20km so that there is one thick contrail layer with the bottom at F346.
Again, Contrails ARE possible!

These are put up as examples of how jet exhaust condensation is NOT possible, but the data demonstrates the opposite. How many other examples are there like this? Is this a typical example?

On that site the author states that for contrails to form and be persistent, the RH needs to be at least 60%. This is the rule used to determine that these cases show that persistent contrails are NOT possible, and a reference is cited. According to Mark Schrader in "Calculations of Aircraft Contrail Formation Critical Temperatures".
http://ams.allenpress.com/amsonline/?request=get-document&issn=1520-0450&volume=036&issue=12&page=1725
persistence will occur when the vapour pressure of water is greater than the saturation vapour pressure relative to ice. The values of these depend only on temperature (and RH in the case of VP, VP = RH x SVPw). They are the result of the Clausius-Clapyron equation from the thermodynamics of water substance.

In the table below I have calculated the minimum RH required for contrail persistence for temperatures between -30 and -69 degrees Celsius (to the nearest 1%).

T    -30    -31    -32    -33    -34    -35    -36    -37    -38    -39


RH    75     74     74     73     72     71     71     70     69     69


                                                                                


T    -40    -41    -42    -43    -44    -45    -46    -47    -48    -49


RH    68     67     67     66     65     65     64     63     63     62


                                                                                


T    -50    -51    -52    -53    -54    -55    -56    -57    -58    -59


RH    62     61     60     60     59     59     58     58     57     57





T    -60    -61    -62    -63    -64    -65    -66    -67    -68    -69


RH    56     55     55     54     54     53     53     52     52     51

In the case above, there is a minimum temperature at 12527 metres of -60.9 degrees. At this temperature you need a minimum of 55 % humidity for persistent contrails. The data says it is 54% - close.
The lower the temperature, the less RH you need for persistence.
The 60% rule works... at temperatues below -53. A fine point; and now you know.

Well, that is the end of the case studies I have done so far.

Next, seasonal and geographical variation of the occurrence of contrails. A first in New Zealand; and possibly the world.

[Hector]

The charts in this article were constructed as follows:
1) The January (warmest) and July (coolest) monthly long term mean (1968-1996) air temperature analyses for the area surrounding New Zealand were obtained for all available pressure levels from the NCEP Re-Analysis Internet site as plots on a map of the area. The pressure levels used were 20, 30, 50, 70, 100, 150, 200, 250, 300, 400, 500, 600, 700 and 850 hPa. The same was done for the total monthly standard deviation of air temperature, monthly long term mean relative humidity and total monthly standard deviation of relative humidity.
2) Average air temperature and RH soundings for each of Whenuapai, Paraparaumu and Invercargill were obtained by reading the temperature and RH at the location of the stations in the . And the same for the standard deviation of air temperature and RH.
3) These average soundings were run through my contrail analysis spreadsheet to obtain the average contrail altitude range. There is the additional feature of the expected range of air temperatures and RH. The two thin red lines left and right of the average air temperature line are drawn st +/- 1.96 standard deviations. This means that 95% of observations will be between these lines. The two thin green lines are drawn at +/- 0.575 standard deviations. 43.5% of the observations are between those lines.

FAQ

43.5% ? So, why isn't it 50% or something?
I misread the Normal disribution table for the standardised variate corresponding to +/- 25%. It should have been 0.675. It doesn't matter... the RH distribution is far from 'normal' or classic Gaussian bell shape. It is kind of squarish, partly from being limited between 0 and 100%. I also made a mistake in my first version of Contrail Analysis charts where I spelled Contrail as 'Contral'.

The RH above 300 hPa looks fake. What happened?
There was no RH data available above 300 hPa in the NCEP Re-Analysis dataset, so I simplistically tapered the RH off to zero at the summer time tropopause level (where the temperature in the summer sounding is lowest). It is fake, but what else can you do?

What's the height scale based on? The temperature doesn't go all the way down to the surface.
I only retrieved enough pressure levels to cover a few levels above and below the pressures covered in the contral Crtitcal Temperature table, and from this the proper average physical height cannot be calculated. So, the height scale is based on the International Standard Atmosphere. This means the contrail ranges are based on pressure levels and expressed as Flight Levels, which refer to pressure altitudes anyway.

First, Summer (Junuary) at the three radiosonde stations



At Whenuapai in summer, the average lower boundary for contrails is fairly high at F371; over half way up the nornal cruise altitude range for jet planes. With proper RH data, it could be a bit lower though. So this goes some way to explain a low occurrence of contrails over northern New Zealand, as John and Melody Anderson have already noted. Over the Far North, the occurrence will be less still.



At Paraparaumu in summer, the average lower boundary for contrails is 334 metres (1100 feet) lower than at Whenuapai at F360.



At Invercargill in summer, the average lower boundary for contrails is 462 metres (1500 feet) lower still at F345. It is clear at this southern station that the air temperature spends a lot more time higher than the critical temperature (no contrails) in the jet cruising altitude range.

Now, Winter (July) at the three radiosonde stations



In winter at Whenuapai, the average air temperature trace barely goes below the critical temperature for contrails in the altitude range F322 to F374. So a bit under half the time in winter, contrails are not possible over northern New Zealand.



In contrast to Whenuapai in winter, at Paraparaumu, the average contrail height range completely includes the jet cruising altitude range by about 300 metres. The air temperature spends well over half the time below the the critical temperature (contrails!) in the winter.



At Invercargill in winter, the 'more in the south' trend continues. The average contrail range spans the jet cruising altitude range by a larger margin still. The air temperature is almost always below the the critical temperature (in the jet cruising altitude range) meaning contrails are possible most of the time.

I hope you will find these charts useful.