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Anomalous DCA anomalies?


Inverted_Trough

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Ok, went to the Utah St climate center and downloaded the IAD temps and the Sterling coop/ghcn data.  The Sterling data is in rough shape right now, but you can do a comparison after correcting for missing, bad (August 11/12th?), or days where highs may have been corrupted by time of day (early June murk).

 

During June, IAD ran almost 0.5° higher than Sterling

During July, IAD ran less than 0.1° higher

During August, IAD ran lower than Sterling by a bit over 0.3°

 

Of course, that doesn't help at all.  But I did the work, so there it is.  :P

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Ok, went to the Utah St climate center and downloaded the IAD temps and the Sterling coop/ghcn data.  The Sterling data is in rough shape right now, but you can do a comparison after correcting for missing, bad (August 11/12th?), or days where highs may have been corrupted by time of day (early June murk).

 

During June, IAD ran almost 0.5° higher than Sterling

During July, IAD ran less than 0.1° higher

During August, IAD ran lower than Sterling by a bit over 0.3°

 

Of course, that doesn't help at all.  But I did the work, so there it is.  :P

Is LWX right at IAD? I guess I should know that. 

 

Does seem generally close enough to be about the same. Tho do they do 12z to 12z reporting there? I guess so if it's listed as a coop. 

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Is LWX right at IAD? I guess I should know that.

Does seem generally close enough to be about the same. Tho do they do 12z to 12z reporting there? I guess so if it's listed as a coop.

The office is about 5 miles from the ASOS and a little lower in elevation. My house is actually closer than the office.

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When doing the comparisons, I'd be wary of incorporating the daily minimums for IAD and DCA.  The reason I only looked at daily maximums for my comparison is because the atmosphere is better mixed in the afternoon, mitigating the impact of UHI somewhat.  Daily minimums have wide variance and the difference between minimums could fluctuate greatly even month to month.  In other words, it's much harder to "separate the signal from the noise" if you're comparing minimums.

 

I don't think there's a way to quantify with any certainty what the warm bias was with the old sensor.  I've believed for quite some time that DCA was reading a couple degrees too warm - based on a lot of other evidence besides the subject of this topic - but I guess there's no way to know for sure.

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When doing the comparisons, I'd be wary of incorporating the daily minimums for IAD and DCA.  The reason I only looked at daily maximums for my comparison is because the atmosphere is better mixed in the afternoon, mitigating the impact of UHI somewhat.  Daily minimums have wide variance and the difference between minimums could fluctuate greatly even month to month.  In other words, it's much harder to "separate the signal from the noise" if you're comparing minimums.

 

I don't think there's a way to quantify with any certainty what the warm bias was with the old sensor.  I've believed for quite some time that DCA was reading a couple degrees too warm - based on a lot of other evidence besides the subject of this topic - but I guess there's no way to know for sure.

Even comparing only daily DCA/IAD maximum temperatures, there have been significant historical month-to-month fluctuations with respect to differentials. For example, in June 1976 the daily maximum DCA/IAD differential averaged 5.00 degrees, but it fell to 3.48 degrees in July 1976 and only 1.06 degrees in August 1976.  Of course, in view of analyses questioning the reliability of both the DCA and IAD sensors in recent months, one might now ask:  Did they change both sensors in mid-July of that year? ;)

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Even comparing only daily DCA/IAD maximum temperatures, there have been significant historical month-to-month fluctuations with respect to differentials. For example, in June 1976 the daily maximum DCA/IAD differential averaged 5.00 degrees, but it fell to 3.48 degrees in July 1976 and only 1.06 degrees in August 1976. Of course, in view of analyses questioning the reliability of both the DCA and IAD sensors in recent months, one might now ask: Did they change both sensors in mid-July of that year? ;)

There was a paper from the 80s regarding problems with the DCA thermometer around that time. I think it was linked from a blog that was linked from the original CWG article on the recent discrepancies.
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Its been nice to see DCA highs tempered lower by the correction. Still warmer than IAD and BWI as it should be. This recent streak DCA and surrounds have been couple degrees apart but not the 4/5/6 that had become commonplace.

This fall and winter when we radiate out nice let's see what happens.

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Its been nice to see DCA highs tempered lower by the correction. Still warmer than IAD and BWI as it should be. This recent streak DCA and surrounds have been couple degrees apart but not the 4/5/6 that had become commonplace.

This fall and winter when we radiate out nice let's see what happens.

You don't need to wait.  There have already been some strong radiational nights where the difference was over 10 degrees in August, after the sensor was replaced.  Which is to be expected.

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There was a paper from the 80s regarding problems with the DCA thermometer around that time. I think it was linked from a blog that was linked from the original CWG article on the recent discrepancies.

I apologize if it's already posted, but I didn't notice, so....

http://www.nwas.org/digest/papers/1986/Vol11-Issue3-Aug1986/Pg18-Andrews.pdf

Don't know if this is the paper, but I've read it a few times and often thought of TenMan J. when I did.

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You don't need to wait. There have already been some strong radiational nights where the difference was over 10 degrees in August, after the sensor was replaced. Which is to be expected.

How does a 15'x15 measure by station area achieve such a warming factor? How would that occur in total snow cover for the region. If you went 200 feet from the site in any direction I bet the vales would be 5 degrees cooler on a strong radiating at night. Back in the late 70's when airport security was vastly different Stanley R did exactly that and found a difference of -4 average on the three thermometers that he set up

Vindication is sweet and if I am still a nut then so is the Post and several state climatologists and mets. Lot of pushback on getting this done and got a feeling that more will be revealed

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How does a 15'x15 measure by station area achieve such a warming factor? How would that occur in total snow cover for the region. If you went 200 feet from the site in any direction I bet the vales would be 5 degrees cooler on a strong radiating at night. Back in the late 70's when airport security was vastly different Stanley R did exactly that and found a difference of -4 average on the three thermometers that he set up

Vindication is sweet and if I am still a nut then so is the Post and several state climatologists and mets. Lot of pushback on getting this done and got a feeling that more will be revealed

Ummm... What?
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I apologize if it's already posted, but I didn't notice, so....

http://www.nwas.org/digest/papers/1986/Vol11-Issue3-Aug1986/Pg18-Andrews.pdf

Don't know if this is the paper, but I've read it a few times and often thought of TenMan J. when I did.

Thanks for posting -- very interesting article, which again points to the need for a second sensor at official NWS stations.  I note however, that the Summer 1976 DCA temperature numbers were not called into question.  So, if the IAD sensor was also accurate during that season, it would seem that the DCA/IAD average daily maximum differential may have truly fallen from 5.00 degrees in June 1976 to 1.06 degrees in August 1976

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Seems he does not want to acknowledge that there is really no mystery here. UHI in DC often results in dramatic contrasts in temps between the city itself and close by outying areas. This is not a seasonal thing. And I really doubt the sensor itself or the measuring circuit was the cause of any significant errors.

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Seems he does not want to acknowledge that there is really no mystery here. UHI in DC often results in dramatic contrasts in temps between the city itself and close by outying areas. This is not a seasonal thing. And I really doubt the sensor itself or the measuring circuit was the cause of any significant errors.

And you do not correctly comprehend the relationship between the atmosphere, the overall geography, and a tiny patch of ground. Were the thermometer located next to the Williard in an entire asphalt environment that would be a different matter. Other than the airport building itself DCA is surrounded by water and a parklike environment  Several hundred yards to the west is extensively urbanized.

There will be more changes coming it was just that the only way to get this first step done was to ease in gradually.

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Several hundred yards isn't much. The airport is surrounded by big urbanization and the predominant wind during hot days is off the hotness a few hundred yards away. Again look at the city temps at night basically the same.

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Elevation is king, it often remains overlooked in accounting for temperature differentials. DCA is somewhat locked in a coastal valley, there is way more to the story than UHI. It's a brutal combination of AGW heated water, asphalt, elevation, and southern location relative to IAD.

Its mostly UHI in this case. Tenman even complained about Annapolis temps during good radiating nights in winter being significantly colder than DC. Not King Elevation in that case. And not a faulty sensor either. 

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Its mostly UHI in this case. Tenman even complained about Annapolis temps during good radiating nights in winter being significantly colder than DC. Not King Elevation in that case. And not a faulty sensor either. 

And Annapolis is closer to the bay than DCA is to the river.

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All I know is that KWWD has very similar climatology. Take it for what it's worth. ;)

Well, you are on the same latitude, as am I. My location is at the same latitude as the very northern tip of DC. But, I am on the interior of the upper eastern shore, away from any effects from UHI, or proximity to water(unlike you). So even though I lack elevation, around 60 feet, my temps are almost always cooler than DC, as well as places like Annapolis, and Dover, and anywhere along the bay really. On cold winter mornings it is very common for temps imby to be 5 to as much as 10 degrees colder than Easton MD, where I work. And of course there is no hint of urban anything near me, other than the tar and chip road.

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Its mostly UHI in this case. Tenman even complained about Annapolis temps during good radiating nights in winter being significantly colder than DC. Not King Elevation in that case. And not a faulty sensor either.

Ten man did not complain about Annapolis and that sort of falsehood is what turns legitimate discussion into food fights. Get your shi$ straight. I use Annapolis as the example of why Dca proximity to water does not work because Annapolis is located due west also of a much bigger body of water. You out of area guys are clueless and Ian's comment No better as dca is 70% surrounded by water marsh and extensive tree scape. The very idea that Nothing was wrong at dca has already been squashed with more adjustments likely on the way
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