{"id":24403,"date":"2024-08-14T08:01:25","date_gmt":"2024-08-14T14:01:25","guid":{"rendered":"https:\/\/www.thorntonweather.com\/blog\/?p=24403"},"modified":"2024-08-22T08:37:47","modified_gmt":"2024-08-22T14:37:47","slug":"part-2-data-shows-denver-weather-records-skewed-by-move-to-dia","status":"publish","type":"post","link":"https:\/\/www.thorntonweather.com\/blog\/thornton-weather\/part-2-data-shows-denver-weather-records-skewed-by-move-to-dia\/","title":{"rendered":"Part 2: Data shows Denver weather records skewed by move to DIA"},"content":{"rendered":"
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Two airports, two different climates. How Denver’s weather and climate records are skewed by a 12 mile move. (ThorntonWeather.com)<\/figcaption><\/figure>\n

ThorntonWeather.com\u2019s owner and operator used to write for a now-defunct website called Examiner. This was a national site but with locally focused content. As the Denver Weather Examiner, Tony covered a number of topics related to Denver and Colorado weather.<\/p>\n

Among them, he was always quick to point out how Denver\u2019s weather records were being skewed by the move of Denver\u2019s official weather station to Denver International Airport. In 2009, he wrote a three-part series explaining why this was an issue and why it mattered.<\/p>\n

Fifteen years later, this continues to be a problem and thus we are re-publishing the series here. While the data is not current and some of the images were lost with time, readers can still understand and appreciate the problem.<\/p>\n

Part 2: Data shows Denver weather records skewed by move to DIA<\/strong>
\nOriginally published March 3, 2009, Examiner.<\/strong><\/p>\n

Did you hear February was Denver\u2019s least snowiest month?\u00a0 Or was it?\u00a0 As we discussed yesterday, a growing chorus of voices are objecting to the National Weather Service\u2019s use of measurements at Denver International Airport for official Denver weather record keeping.\u00a0 They claim that comparing data from DIA to previous records compiled for more than 40 years at Stapleton and more than 75 years before that in downtown isn\u2019t a fair analysis.<\/p>\n

In this second of a three part series, we take a look at some of the data to see just how big of a difference the 12 mile move from Stapleton to DIA made.\u00a0 We also investigate potential issues with accuracy at the automated monitoring station at DIA that could forever be altering our climate records.\u00a0 Tomorrow we will take a look at why all of this matters and why you should care.<\/p>\n

Temperatures<\/strong><\/p>\n

An analysis shows that in just the last eight years DIA registers warmer high temperatures and cooler low temperatures than stations closer to downtown and in areas where people actually live.\u00a0 For our comparison, we compared the last eight years of data for Denver International Airport versus the measurements taken at Buckley Air Force Base.\u00a0 We chose Buckley because that is the closest official measuring station to the location of the old Stapleton International Airport.<\/p>\n

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As you can see, the differences between where measurements have been taken for the last 14 years at DIA and where they were taken previously is significant.\u00a0 DIA\u2019s highest recorded temperatures each year averages nearly 2 degrees more than those closer to Denver.\u00a0 Similarly, the station\u2019s low temperatures are more than 2 degrees cooler.\u00a0 This essentially throws any record high or record low temperatures that were recorded in the last 14 years out the window.\u00a0 Any comparison of today\u2019s data with historical records taken at Stapleton are invalid because the location move to DIA has clearly impacted the measurements.<\/p>\n

Precipitation<\/strong><\/p>\n

This is probably the single most astonishing statistic and helps to show just how much of a difference 12 miles can make.\u00a0 The National Weather Service has been taking precipitation measurements at both DIA and at the former Stapleton site so we can do a direct comparison between the two sites.\u00a0 The results are astonishing.<\/p>\n

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The chart clearly shows that precipitation measurements at DIA consistently underperform as compared to those at Stapleton.\u00a0 Over the 8 year period, DIA on average measures 13% less precipitation than Stapleton.<\/p>\n

One year in particular stands out.\u00a0 In 2002 Colorado was in a drought by any measurement.\u00a0 At the end of the year the National Weather Service proclaimed it as Denver\u2019s driest on record.\u00a0 However, that claim was based on measurements at DIA.\u00a0 If you use the measurements at Stapleton \u2013 where weather records were kept for more than 40 years \u2013 the claim doesn\u2019t stand up to scrutiny.\u00a0 Stapleton\u2019s 8.49 inches of precipitation in 2002, while certainly a dry, below normal year, would actually make it only the 6th<\/sup> driest year.\u00a0 It can easily be argued that the claim that 2002 was Denver\u2019s driest year should be discarded.<\/p>\n

As a more recent example, March 2008 was proclaimed the \u201cthird driest March on record\u201d when a mere 0.17 inch of precipitation was recorded at DIA.\u00a0 However, 0.55 inch was recorded at Stapleton, an amount which would not put the month anywhere near the top 10 driest.<\/p>\n

Snowfall<\/strong><\/p>\n

Historical snowfall measurement comparisons between the two locations unfortunately cannot be directly performed as it was only this year that the National Weather Service began measuring snow at DIA.\u00a0 However, we can infer from the precipitation measurements noted above that there will be a comparable discrepancy in snowfall measurements as well.\u00a0 This stands to reason as the plains receive less snow than areas closer to the mountains and going 12 miles east can make a big difference.<\/p>\n

Issues of accuracy?<\/strong><\/p>\n

The precipitation and snowfall issue gets even further convoluted this year with the move to measuring snowfall at DIA.\u00a0 While this would seem to solve the problem of inconsistency between taking precipitation measurements at DIA but snowfall at Stapleton, it turns out things aren\u2019t quite that easy.<\/p>\n

Weather enthusiasts have noticed problems with recent snowfall and precipitation measurements.\u00a0 Just recently on Monday, January 12th<\/sup>, when a small snow storm moved through the Front Range the National Weather Service recorded 3 inches of snowfall but only 0.03 inch precipitation.<\/p>\n

On average snow has a 10:1 moisture content which means that 1 inch of snow equals 0.1 inch of moisture.\u00a0 Using the standard, approximately 0.3 inch precipitation should have been recorded \u2013 10 times what was actually reported.<\/p>\n

Extending the observation period out to include the two month period from December 1, 2008 to January 31, 2009, similar problems have occurred.\u00a0 At Stapleton, where measurements are taken manually, 12 inches of snowfall was recorded with a moisture content of 1.08 inches \u2013 approximately an 11:1 ratio and one that could be expected.\u00a0 By contrast, DIA \u2013 using automated precipitation measurements \u2013 recorded 15 inches of snow but a meager 0.37 inch of precipitation.\u00a0 That is an unfeasibly dry 40:1 snow to precipitation ratio.<\/p>\n

Detractors abhor the use of automated stations for such important climate records and are quick to point out that this is but one of many examples of inconsistent measurements.\u00a0 One former NWS employee said, \u201cthe NWS sold their soul to automation years ago\u201d and as a result we are stuck with inaccurate records.<\/p>\n

Two airports, two different climates. Read the series:<\/strong><\/p>\n