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Topic: Chems heavier in east or west? | Topic page views:
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Feelin Kocky
A Member
Underground Weather Control Bunker
537 posts, Jan 2003
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posted 01-22-2003 12:29 AM
   
canex are you refering to rawinsonde, GOES, or model derived soundings?
[Edited 1 times, lastly by Feelin Kocky on 01-22-2003] 
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Lulu
ice behaving badly
right here
2553 posts, Dec 2000
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posted 01-23-2003 07:38 AM
>>most of the trails appeared to stop abruptly just north of the Portland/Vancouver area.<<canex or FK could you explain the abrupt ending of trails...thanks. Weather for later in the evening on the 18th "That night a fog rolled in &
the next morning was misty with very low cloud cover." The reason I ask about the RH readings canex is that I was under the impression these readings mean squat when predicting if trails will persist or not. quote:
Wild Bill says:Well, there simply aren't enough data points anyway, even if they were accurate enough. You simply can't look at the ADDS modeling and then claim that what's over your head isn't a contrail.
http://adds.aviationweather.noaa.gov/projects/adds/forum/?read=581 quote:
Wild Bill asks:
How accurate is the Rh data with the flight path tool? We have a group of folks using that data to claim that contrails cannot form over an area, and therefore what they see (contrails) are not actually contrails, but a sprayed substance.
http://pub31.ezboard.com/fcontrailsandchemtrails22884frm1.showMessage?topicID=1110.top ic quote:
D. Rodgers responds:
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. Other factors are involved, such as vertical motion.
http://adds.aviationweather.noaa.gov/projects/adds/forum/?read=582 canex could you address the vertical motion? and why RH readings are so unreliable? and what data is reliable for determining persisting trails? thanks again canex and FK.
[Edited 1 times, lastly by Lulu on 01-23-2003]
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Feelin Kocky
A Member
Underground Weather Control Bunker
537 posts, Jan 2003
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posted 01-23-2003 10:34 AM
"canex or FK could you explain the abrupt ending of trails...thanks."My recolection is that the west coast was near or just east of an upper level ridge. To the east of a ridge, there is general downward moition which would dry the atmosphere. If you ever get a chance to look at an IR or WV satellite loop (try this link: http://www-frd.fsl.noaa.gov/sat/) you should see clouds disipate east of the ridge axis. " "That night a fog rolled in &
the next morning was misty with very low cloud cover." " The weather at the surface does't generally directly coorispond to what is going on at 35K ft.
"canex could you address the vertical motion? and why RH readings are so unreliable? and what data is reliable for determining persisting trails? thanks again canex and FK."
RH readings are not necessarily inaccurate. A dewpoint measurement + or - a couple of degrees C is not so bad. However, when computing RH when the temp is -45C a small error in dewpoint means a larger error in RH. This error gets worse the colder it is. This is why, I think, we sometimes see contrails when the atmospheric conditions are measured as "marginal" or "not favorable." Also, the troposphere can have numerous thin layers. Some are moist and some not. So you could see one aircraft fly over with no contrail and another, at a slightly different altitude, produce contrails. F.K.
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Lulu
ice behaving badly
right here
2553 posts, Dec 2000
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posted 01-23-2003 05:02 PM
>>That night a fog rolled in &
the next morning was misty with very low cloud cover.<<
canex was wondering >>"Should have cleared out some by evening."<< FK--I realize weather at the earth's surface does not affect contrails.>>RH readings are not necessarily inaccurate.<< Well, apparently they are so I no longer consult them FK.
[Edited 1 times, lastly by Lulu on 01-23-2003]
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theseeker
One moon circles
Damnit...I'm a doctor jim
3403 posts, Jul 2000
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posted 01-23-2003 05:25 PM
I have noticed quite often that contrails were forming in areas that were orange on the ADDS display, and canex can correct me if I'm wrong here but even rh in the 25 to 50% level may not usually form natural clouds...but rh levels of contrails can be as high as 150% with respect to ice, meaning to me that formation and persistence of cirrus is possible with the aid of a few jets passing by...in an otherwise blue, cloud free sky....
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Lulu
ice behaving badly
right here
2553 posts, Dec 2000
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posted 01-23-2003 06:49 PM
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
A Member
Underground Weather Control Bunker
537 posts, Jan 2003
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posted 01-23-2003 07:42 PM
Why do you say apparently so (that RH is inaccurate)?
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Lulu
ice behaving badly
right here
2553 posts, Dec 2000
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posted 01-23-2003 07:50 PM
>>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
A Member
Underground Weather Control Bunker
537 posts, Jan 2003
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posted 01-23-2003 07:58 PM
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
ice behaving badly
right here
2553 posts, Dec 2000
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posted 01-23-2003 08:02 PM
>>marginal<<is 0 to 5% marginal?
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Feelin Kocky
A Member
Underground Weather Control Bunker
537 posts, Jan 2003
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posted 01-23-2003 08:04 PM
+-5% RH? no, I thinks that's darn good at -45C
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theseeker
One moon circles
Damnit...I'm a doctor jim
3403 posts, Jul 2000
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posted 01-23-2003 09:36 PM
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
ice behaving badly
right here
2553 posts, Dec 2000
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posted 01-25-2003 10:06 AM
>>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
Senior Member
USA
164 posts, Oct 2000
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posted 01-25-2003 10:21 PM
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
A Member
Underground Weather Control Bunker
537 posts, Jan 2003
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posted 01-26-2003 01:05 PM
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
Senior Member
Orange County, CA,USA
162 posts, Jan 2003
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posted 01-28-2003 02:14 AM
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. ------------------
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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