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Anomalous DCA anomalies?


Inverted_Trough

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Dulles did have a rain shower go through.  Today wasn't the greatest day for comparison.

There were several stations that hit 90 or above today.  This is in stark contrast to before the sensor was replaced, where DCA would be the only station within a 300-mile radius that would hit 90 - and this happened consistently.

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The fact that a major metro area news agency ran the article and described who had been involved in the project and what was done was vindication for me.  The immediate results thereafter also further vindication.  Matt unfortunately demonstrated an inability to reconsider his position he has taken.

DCA will upon occassion still be +5 to +10 on the nightime mins, it happens a considerable amount of time, and based on the circumstances I do not have a quarrel with that at times.  However, in full snowcover and a frozen Potomac there is NO mechanism for that to occur as any potential heat producing resource would be blanketed. Does anyone really believe that a 15'X15' area can overwhelm cubic tons of atmosphere, snow cover, frozen river?  Also, DCA is not at the corner where the Williard sits. It's surrounded by water to the ne/e/se/s and tree lined minimally travelled parkway to the west, and granted considerable urbanization further west .  However, under the old measurment regime under the conditions I described DCA would be at 19, Andrews at 9, IAD at 7, BWI at 10 and Annapolis(bigger body of water for those who tote that) 12.  That was always incorrect and will very likley no longer be occurring. 

So my decades long assertions, often childishly ridiculed here, have in fact proven to be true and for all of you who still think not I guess you must be concluding that everyone and everything in that article is "just as dumb as I am"

It is pretty well accepted that DC has one of the most intense urban heat islands among US cities...top 5 I think. Do you deny this? And it is just not plausible that the sensor/measuring instrumentation has been that far off /out of calibration all these years. That basically leaves sensor location as the possible source of any significant error. Also, certainly during winter the urbanized areas can be 10+ degrees warmer at night than outlying areas, even a few miles away. Being out in a very rural area myself, away from any water and nothing remotely considered urban near me, my area radiates incredibly well on a clear, calm, snow covered night. I am between Dover and Annapolis, and sometimes I have low temps more than 10 degrees colder than etiher location. And your comparison of DC  to Annapolis...not a great one- it is a smaller town(and urbanized area) and located west of the "bigger body of water"(the bay). With light W or NW winds, on a clear winter night, the bay would have much less impact on the temps there.

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Probably.. tho Nats park only has reached 86 and it's right across the river basically. I'm still thoroughly unconvinced that there was a continual 1.7 degree anomaly or some such. I don't think that's what the techs implied but that's how it's been received. 

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Bitter little man.  I thought you had it on the ball, now with overwhelming evidence and actions contrary to your opinion and supportive of mine you resort to this. Your fact based debate defense was in fact absent of any fact as it has now turned out. I do not expect you to kiss my as* but I would suggest you get your head out of yours.

 

I actually agreed with you on a lot of your points over the years, but you never showed a modicum of interest in having a dialog on any of this...People tried to engage you on these topics, and you were downright dismissive, derisive, and wasted everyone's time. You were like a bull in a china shop.  Any facts to dispute specific assertions were completely ignored by you.  Don't expect people to kiss your ass after you disrespected everyone'e efforts over the past few years.  You're reasonable when it comes to everything else but when it comes to DCA, you continuously wasted my time for years.  Others were smart enough to ignore it.  Looks like there may be a slight error in the sensor over the last couple years.  You'll find that its replacement still won't validate many of your absurd suggestions over the years.  But what's the difference.  You can say 2+2=5, and I can say no 2+2=4 and you just spit on me and dig deeper...I retract any sort of apology...I apologize to people who are able to engage in good faith debate without being a baby.

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Did you even read the article? On June 9 the sensor was half a degree off from the test equipment. After two days of temps not sure we know anything for sure other than it was replaced. 

 

It does seem like its a little closer aligned to wxbug temps today though for the most part it has been in the past. There have been a handful of odd days in recent times...

 

He's never acknowledged anything that might counter his opinions.  Ever.  That is not how he operates.  And it is too bad.  Because when it doesn't come to DCA, he has a lot to offer that people don't always give him credit for. 

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eh... he's very smart and accomplished but his thoughts on this subject seem iffy at best IMO/somewhat biased. DCA isn't included in warming research. there is no real way to change the temps. 

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eh... he's very smart and accomplished but his thoughts on this subject seem iffy at best IMO/somewhat biased. DCA isn't included in warming research. there is no real way to change the temps.

Maybe just * temps for the months since it was noticed?

I agree it would be hard to actually change the temps, is there another verifiable station close by to compare for the months data?

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Maybe just * temps for the months since it was noticed?

I agree it would be hard to actually change the temps, is there another verifiable station close by to compare for the months data?

Nothing great I guess. Arboretum coop is fairly close and there's another in Vienna and one at Dalecarlia reservoir. But the coop data is often a little questionable. Still, Arboretum and Vienna have 38 and 36 90-degree days respectively compared to 44 at DCA so not hugely different.. perhaps about what you'd expect.  If the wxbug network had records it might help.. or you could comb through PWS on wunderground but all of this is close to guesswork.

 

I'd give in on idea that perhaps a few 90-degree days weren't 90-degree days at DCA but not sure it's many.  Pre-sensor switch IAD had 29% the 90-degree days DCA had. Since the switch it's had 33% of the days.. and the patterns are a bit different with much drier soils especially over western parts of the area lately. A majority of the hot days have had predominant south winds at DCA as well.

 

Truth is a degree or so doesn't even really matter that much it's more about trends. All databases suck to some degree.. we overfocus on this issue I think.

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  • 2 weeks later...

Well, now that August is over and we have a better sample size to compare the new sensor readings with the old, I thought I'd go ahead and do the analysis:

 

The following stats are the average difference in temperature between the DCA and IAD daily maximums

 

July 1-31:  3.97

Aug 1-10: 4.6

Aug 11-31: 1.71 (after sensor was replaced)

 

So it appears that old sensor was anywhere from 2 to 3 degrees too high.  And it had been that way for 19 months.  Unbelievable.

The record warm May and the 90-degree day totals definitely needs as asterisk next to it.

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Well, now that August is over and we have a better sample size to compare the new sensor readings with the old, I thought I'd go ahead and do the analysis:

 

The following stats are the average difference in temperature between the DCA and IAD daily maximums

 

July 1-31:  3.97

Aug 1-10: 4.6

Aug 11-31: 1.71 (after sensor was replaced)

 

So it appears that old sensor was anywhere from 2 to 3 degrees too high.  And it had been that way for 19 months.  Unbelievable.

The record warm May and the 90-degree day totals definitely needs as asterisk next to it.

 

Agree with Ellinwood that the analysis needs to be expanded to tell us anything.

 

 

In addition:

 

1)  Meterologically, this period included a massive change in sensible weather, from extremely wet to very dry.  I have not studied the issue, but it would not shock me if the early summer wetness affected the observation locations much differently, especially considering the substantial land cover differences between IAD and DCA.

 

2)  The sensor was tested earlier in the summer and the error was in the acceptable range.  Where does 19 months come from?

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I need to pull the NCDC numbers but via LWX the end of Aug Dulles has a higher avg high temp than DCA. Possibly a rounding issue or a very small difference. Either way Dulles has finally been putting up some legit numbers the last few weeks when it was struggling prior. I do think the drier pttern matters.

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Well, now that August is over and we have a better sample size to compare the new sensor readings with the old, I thought I'd go ahead and do the analysis:

 

The following stats are the average difference in temperature between the DCA and IAD daily maximums

 

July 1-31:  3.97

Aug 1-10: 4.6

Aug 11-31: 1.71 (after sensor was replaced)

 

So it appears that old sensor was anywhere from 2 to 3 degrees too high.  And it had been that way for 19 months.  Unbelievable.

The record warm May and the 90-degree day totals definitely needs as asterisk next to it.

I calculate a difference of 1.81 degrees for Aug 11-31, and so I believe the difference in the maximums for that period compared with Aug. 1-10 was 2.79 degrees.  However, I calculate that the change in the variation between the DCA and IAD minimums for the two periods was only 0.92 degrees (Aug 1-10, 7.40 degrees; Aug 11-31, 6.48 degrees). Also, in July the difference in the DCA and IAD minimums was 7.10 degrees, so that varied from the Aug 11-31 minimums difference by only 0.62 degrees. 

 

It's unfortunate that we have to play this guessing game, as a new sensor could have been placed right next to the old sensor and a comparison made of the temperature readings for at least a few weeks.  And, as Ian suggested, why not two sensors at all times?

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I need to pull the NCDC numbers but via LWX the end of Aug Dulles has a higher avg high temp than DCA. Possibly a rounding issue or a very small difference. Either way Dulles has finally been putting up some legit numbers the last few weeks when it was struggling prior. I do think the drier pttern matters.

 

Dulles hasn't really changed its tune compared to BWI... or MRB... or CHO... etc... with high temp difference changes of about a degree over the summer.  Below numbers are from the F6's for BWI, MRB, CHO, and Wunderground for the AWOS sites.

 

HIGHS

Mon KIAD KBWI Diff

Jun 82.6 82.9 +0.3

Jul 85.2 86.5 +1.3

Aug 85.4 86.0 +0.6

 

HIGHS

Mon KIAD KMRB Diff

Jun 82.6 81.7 -0.9

Jul 85.2 84.9 -0.3

Aug 85.4 85.3 -0.1

 

HIGHS

Mon KIAD KCHO Diff

Jun 82.6 83.4 +0.8

Jul 85.2 85.6 +0.4

Aug 85.4 85.2 -0.2

 

HIGHS

Mon KIAD KJYO Diff

Jun 82.6 82.8 +0.2

Jul 85.2 85.9 +0.7

Aug 85.4 86.5 +1.1

 

HIGHS

Mon KIAD KHEF Diff

Jun 82.6 83.1 +0.5

Jul 85.2 85.4 +0.2

Aug 85.4 85.0 -0.4

 

HIGHS

Mon KIAD KDAA Diff

Jun 82.6 83.2 +0.6

Jul 85.2 85.6 +0.4

Aug 85.4 85.1 -0.3

 

HIGHS

Mon KIAD KGAI Diff

Jun 82.6 81.1 -1.5

Jul 85.2 83.5 -1.7

Aug 85.4 84.3 -1.1

 

HIGHS

Mon KIAD KHWY Diff

Jun 82.6 83.8 +1.2

Jul 85.2 85.9 +0.7

Aug 85.4 86.1 +0.7

 

HIGHS

Mon KIAD KCGS Diff

Jun 82.6 82.7 +0.1

Jul 85.2 85.7 +0.5

Aug 85.4 85.7 +0.3

 

HIGHS

Mon KIAD KDCA Diff

Jun 82.6 86.1 +3.5

Jul 85.2 89.1 +3.9

Aug 85.4 88.0 +2.6

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I calculate a difference of 1.81 degrees for Aug 11-31, and so I believe the difference in the maximums for that period compared with Aug. 1-10 was 2.79 degrees.  However, I calculate that the change in the variation between the DCA and IAD minimums for the two periods was only 0.92 degrees (Aug 1-10, 7.40 degrees; Aug 11-31, 6.48 degrees). Also, in July the difference in the DCA and IAD minimums was 7.10 degrees, so that varied from the Aug 11-31 minimums difference by only 0.62 degrees. 

 

It's unfortunate that we have to play this guessing game, as a new sensor could have been placed right next to the old sensor and a comparison made of the temperature readings for at least a few weeks.  And, as Ian suggested, why not two sensors at all times?

 

ASOS isn't designed to accommodate two identical thermometers, unfortunately.  But, it does have two thermometers.  The other one is part of the dew point sensor and the thermometer data from it is used to calculate dew point, while the actual thermometer reading isn't used. 

 

As far as using night-time mins... it gets tricky because of the UHI.  As noted

http://www.harc.edu/sites/default/files/documents/projects/UHI_Basics.pdf

the UHI is small to absent during the day, but much more intense at night.

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Dulles hasn't really changed its tune compared to BWI... or MRB... or CHO... etc... with high temp difference changes of about a degree over the summer.  Below numbers are from the F6's for BWI, MRB, CHO, and Wunderground for the AWOS sites.

 

Probably framed it wrong.. was thinking more like on "close to 90 days" IAD seems to have been putting up 90 better lately compared to earlier in the summer but honestly that's just off the top of my head too as I haven't really given this a heavy look yet (may not ever as I don't think we'll ever come to any real conclusions here). Good comparisons tho. 

 

I think clearly DCA was running a bit warm at times at least. I still don't think there's any evidence it was running 2-3 degrees warm all the time for 1.5 yrs or whatever. 

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