Author Topic: ASOS/AWOS Accuracy  (Read 3469 times)

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Offline CW7491

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Re: ASOS/AWOS Accuracy
« Reply #50 on: January 20, 2024, 10:26:39 AM »
Thanks for the info. Is this SAWS/AWS part of ASOS as a backup system, or completely independent?

Offline CW7491

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Re: ASOS/AWOS Accuracy
« Reply #51 on: January 20, 2024, 03:21:32 PM »
Looks like I found an answer to my own question. Itís all in a name SAWS (Stand Alone Weather System). Effectively a backup weather system used by the FAA. News to me Ö

https://www.tc.faa.gov/its/worldpac/standards/faa-e-2935.pdf

Offline ASOSWX

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Re: ASOS/AWOS Accuracy
« Reply #52 on: January 20, 2024, 03:27:41 PM »
  The SAWS and AWS are FAA-owned equipment totally separate from the ASOS program.  SAWS came out late 90s. 
Hope this helped

Offline CW7491

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Re: ASOS/AWOS Accuracy
« Reply #53 on: January 20, 2024, 03:54:55 PM »
Thanks Joe!

Offline CW2274

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Re: ASOS/AWOS Accuracy
« Reply #54 on: January 20, 2024, 04:06:41 PM »
They are on a PMS like all FAA equipment, so I'm sure it's checked at least once a year. If it is off, this could potentially be critical with pilots now that icing conditions are becoming more prevalent.

There are quarterly, Semi-annual, and Annuals on the System.  The DTS1 is sent in every 18 months for calibration.
[tup]

Offline ValentineWeather

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Re: ASOS/AWOS Accuracy
« Reply #55 on: January 23, 2024, 09:27:12 AM »
Too bad they can't fix the freezing fog from icing over the temperature sensor. It's happened twice now this winter on the KVTN ASOS. As it ices over, it warms. Why because it blankets the sensor in thick ice like it does everything else. They really need to go back to a naturally aspirated Stevenson Screen with a fan like they use in Canada, and other countries.  At least you can turn the fan off to prevent the sensor from becoming ice covered.
What happens is the RH goes up with the temperature separation (air and dew point), as you can see here. The actual air temperature was near the dew point temp (12į) with the thick ice fog. The dew point sensor is separate and non-aspirated, so was the only true indicator of temperature, with the near zero visibility at times.
 
NOAA just gave a contract to RM Young for their aspirated shield, another mistake. The RM Young is famous for sucking in heated exhaust during light wind and reading high, along with other issues. Just ask Jerry Graves he has one. They really should have considered the naturally aspirated baranidesign gen3 MeteoShield's as shield replacements. They follow the Stevenson Screen with a fan very closely, with extensive testing done by University of Vienna. 
Randy

Offline CW7491

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Re: ASOS/AWOS Accuracy
« Reply #56 on: January 23, 2024, 01:07:51 PM »
Interesting. I wonder if the wire mesh in the HO-1088 intake is helping the ice build. Do you have the Davis mesh installed at the intake? Any issues in those conditions? I also meant to ask if you applied any temp offset to match with the nimbus or if it matches well without one

Offline ValentineWeather

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Re: ASOS/AWOS Accuracy
« Reply #57 on: January 23, 2024, 01:30:11 PM »
Interesting. I wonder if the wire mesh in the HO-1088 intake is helping the ice build. Do you have the Davis mesh installed at the intake? Any issues in those conditions? I also meant to ask if you applied any temp offset to match with the nimbus or if it matches well without one

Don't know about the ASOS.  I don't run with the mesh on. The Davis aspirated also froze up just like the ASOS, didn't see the same rise, only a couple degrees vs the Nimbus using the Gill shield.  The only offset I use is for the humidity on the Davis. -5 and 1.10 on the multiplier.
« Last Edit: January 23, 2024, 01:31:56 PM by ValentineWeather »
Randy

Offline TheBushPilot

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Re: ASOS/AWOS Accuracy
« Reply #58 on: January 23, 2024, 01:42:05 PM »
The dew sensor is warmed so ice accretion is a non-issue. Those Young 43502s frequently experience the hoarfrost in the intake on the NYS mesonet too. Imagine they experience that issue on the OK Mesonet too. Iím not aware of a good way to eliminate the issue completely but I donít think changing shielding methods (aspirated/non-aspirated) inconsistently would be a valid method. Too much variability. FARS are good until they arenít. :roll:


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Offline CW7491

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Re: ASOS/AWOS Accuracy
« Reply #59 on: January 23, 2024, 04:54:51 PM »
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I could definitely see it being a problem especially if itís already loaded up with stuff like this one

Offline drew1021

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Re: ASOS/AWOS Accuracy
« Reply #60 on: January 24, 2024, 07:00:58 AM »
I would hardly call that a screen
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Offline ASOSWX

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Re: ASOS/AWOS Accuracy
« Reply #61 on: January 24, 2024, 06:44:25 PM »
On occasion, the chilled mirror on the 1088 will freeze up.  Usually with a really dirty mirror and moist conditions the heater on the mirror wouldn't keep up.  A good cure for that was to add a step to the cleaning mirror process.  Waxing the mirror made the water droplets much smaller and repelled impurities which really helped with that issue. 

Offline CW7491

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Re: ASOS/AWOS Accuracy
« Reply #62 on: February 05, 2024, 09:25:43 AM »
NWS Louisville had an intern who ended up doing a temperature study at KLEX due to long standing complaints from local news outlets that the airport temperatures were problematic. The intern compared the HO-1088 ASOS hygrothermometer to two nearby MetOne 076b shields. One a KY mesonet station and another a CRN station. The interesting part of his presentation isnít necessarily the results of his comparison, but how it highlights the very loose tolerances on the ASOS instrument partly due to multiple standards (ie manufacturer, FAA, NWS, etc). The sudden, dramatic shifts in temperature for ASOS when the sensor is changed or calibrated also might explain some of the questions of members (Buick) who see unexplained differences in their data in comparison. Itís also interesting to hear how the NWS staff puts itself in pretzels trying to explain and defend something thatís just not really all that defensible for what is considered in this case (and many other cases) national climate sites. An improved system canít come quick enough. Letís also hope that the bureaucratic, conversion and rounding issues are addressed too.

For those who donít have the time or interest in watching it all, an interesting discussion during the Q&A starts at about 28:45.
https://m.youtube.com/watch?v=Sd9JhBjaJGw
« Last Edit: February 05, 2024, 01:06:11 PM by CW7491 »

Offline TheBushPilot

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Re: ASOS/AWOS Accuracy
« Reply #63 on: February 05, 2024, 09:59:47 AM »
WOW is all I have to say.
"There is ó always ó more than one thing influencing anything we are trying to measure." ~ Sherman Fredrickson
"Do it right or don't do it at all."

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Offline hofpwx

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Re: ASOS/AWOS Accuracy
« Reply #64 on: February 05, 2024, 01:40:08 PM »
NWS Louisville had an intern who ended up doing a temperature study at KLEX due to long standing complaints from local news outlets that the airport temperatures were problematic. The intern compared the HO-1088 ASOS hygrothermometer to two nearby MetOne 076b shields. One a KY mesonet station and another a CRN station. The interesting part of his presentation isnít necessarily the results of his comparison, but how it highlights the very loose tolerances on the ASOS instrument partly due to multiple standards (ie manufacturer, FAA, NWS, etc). The sudden, dramatic shifts in temperature for ASOS when the sensor is changed or calibrated also might explain some of the questions of members (Buick) who see unexplained differences in their data in comparison. Itís also interesting to hear how the NWS staff puts itself in pretzels trying to explain and defend something thatís just not really all that defensible for what is considered in this case (and many other cases) national climate sites. An improved system canít come quick enough. Letís also hope that the bureaucratic, conversion and rounding issues are addressed too.

For those who donít have the time or interest in watching it all, an interesting discussion during the Q&A starts at about 28:45.
https://m.youtube.com/watch?v=Sd9JhBjaJGw


Isn't the purpose of the USCRN to address siting and instrument issues and thus provide a baseline for comparison and correction?


Offline CW7491

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Re: ASOS/AWOS Accuracy
« Reply #65 on: February 05, 2024, 02:35:51 PM »
I know USCRN is designed to be the national standard for climate monitoring according to their website. Whether they intend to manipulate/correct weather data from ASOS climate sites using USCRN data is something I couldnít speak to. I guess my point is that Iíve been surprised from researching it just how poor the tolerances are for ASOS, which are used as official climate sites, compared to the USCRN system and state run mesonets. The siting issues are what they are, but for the price of the system, it seems a temperature system with more accurate specs should be possible. To say nothing of the convoluted rounding and conversion processing. Iím hopeful that the new ASOS TRH system based on the HMP155 and RM Young shield will be an improvement, but it has run into delays. I also wish they had gone with the MetOne076b shield for temperature.
« Last Edit: February 05, 2024, 02:53:57 PM by CW7491 »

 

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