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Lulu
Joined: 22 Dec 2000
Posts: 2501
Location: right here |
 Fri Jan 24, 2003 1:49 am
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well seeker that means nothing to me i'm afraid--rh readings were next to nil (at almost every altitude), some readings well under 30% 2 summers ago--and yet trails formed and persisted--for hours. I just would like to know what good reliable data us lay people can use to predict the formation and persistence of contrails--you know like a contrail forcast... |
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Feelin Kocky
Joined: 07 Jan 2003
Posts: 537
Location: Underground Weather Control Bunker |
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Fri Jan 24, 2003 2:42 am
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Why do you say apparently so (that RH is inaccurate)? |
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Lulu
Joined: 22 Dec 2000
Posts: 2501
Location: right here |
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Fri Jan 24, 2003 2:50 am
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>>The RH field is a model-produced (and therefore smoothed) field based on observed data. It is not sufficient to determine whether contrails will form or persist.<< |
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Feelin Kocky
Joined: 07 Jan 2003
Posts: 537
Location: Underground Weather Control Bunker |
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Fri Jan 24, 2003 2:58 am
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Well that statement is true when the fields are generated by models. However, RH/dewpoint is directly measured by rawinsodne observations (like those on the SPC link I gave you). This data is fairly accurate. My point is that very small errors in either T (temperature) or Td (dewpoint) will make bigger differences in RH at very cold temperatures. So, you should not read too much into persistant contrails being observed in an environment that is marginal for contrail formation.
F.K. |
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Lulu
Joined: 22 Dec 2000
Posts: 2501
Location: right here |
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Fri Jan 24, 2003 3:02 am
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>>marginal<<
is 0 to 5% marginal? |
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Feelin Kocky
Joined: 07 Jan 2003
Posts: 537
Location: Underground Weather Control Bunker |
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Fri Jan 24, 2003 3:04 am
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+-5% RH? no, I thinks that's darn good at -45C |
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theseeker
Joined: 25 Jul 2000
Posts: 3403
Location: Damnit...I'm a doctor jim |
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Fri Jan 24, 2003 4:36 am
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yes yes and a plane with 150% rh (with respect to ice) squirting out the tailpipe passes through that -45 and viola...fat trail !
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Lulu
Joined: 22 Dec 2000
Posts: 2501
Location: right here |
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Sat Jan 25, 2003 5:06 pm
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>>is 0 to 5% marginal?<<
Many days here with RH readings between 0 and 5% with trails persisting all day long...
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canex
Joined: 26 Oct 2000
Posts: 164
Location: USA |
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Sun Jan 26, 2003 5:21 am
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Sorry for not replying earlier.
"canex are you refering to rawinsonde, GOES, or model derived soundings?"
Rawinsonde data available on line at university of wyoming weather site.
Current rawinsonde instruments (most from Vaisala) typically yield low values of relative humidity when the temperature is below -40C. The weather service used to throw out data when the temperatures were that low. They started keeping the data and reporting it around 1993. It has some value in that it varies in the right direction (real humidity goes up, the measured humidity goes up on average), but it does not measure enough, hence the dry bias. A measurement of relative humidity around -70C can be biased by as much as 80%. In other words, at 20% RH, the true RH can be 100%. THe bias decreases as the temeprature rises. Model-generated humidities start with the rawinsonde data and adjust them. Sometimes the adjustments increase the values but not always. The model fields are still biased low on average. The random error in the RH is much larger than 5% at low temperatures.
A rawinsonde measurement only provides the humidity at one point in time over a pencil thin column of air. As noted in another post, the humidity can vary dramatically over small and large scales depending on the dynamics and origin of the water vapor. When you see a trail end abruptly, it simply means that the plane stopped flying in saturated air. |
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Feelin Kocky
Joined: 07 Jan 2003
Posts: 537
Location: Underground Weather Control Bunker |
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Sun Jan 26, 2003 8:05 pm
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canex, you said that much better than I. Yes, the NWS does not plot on the Skew-T below minus 40C, but the data is kept in the coded messages. This is why I try not to get to fired up one way or another when contrails form in what appears to be very dry air becuase measuring "RH" is so difficult when only small errors in the data make a huge difference. RHI is what we need to consider. |
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ScaredForTheFuture
Joined: 27 Jan 2003
Posts: 162
Location: Orange County, CA,USA |
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Tue Jan 28, 2003 9:14 am
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I JUST ADDED ANOTHER PICTURE OF TODAY'S MASSIVE CHEMTRAILS WHICH INCLUDE RANDOM BLACK CLOUDS THAT JUST DON'T LOOK NATURAL.
http://www.geocities.com/youarereallypathetic/page1.html?1043742085250 See the pictures here (2).
"01.27.2003, Orange County (home of Disneyland). THE WEATHERMAN HAD THE AUDACITY TO SAY THE DAY WAS "CLOUDY"!! There wasn't a single natural cloud in that sky!!!!!".
It's 12:22am right now and there are STILL long lines everywhere going from East To West I believe.
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Tuesday 7:53am - they must have been spraying all night because the sky is one big fluff of fake looking clouds this morning. Big long streaks of lines, very unnatural. Hey, I crave colder weather, but am I getting it at a price of bad health?
[Edited 2 times, lastly by ScaredForTheFuture on 01-28-2003] |
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