Last week in this blog I posted a couple of stories about the unusual number of warm nights experienced in New Orleans and then about questions surrounding the accuracy of the record. In response to these questions, the Louisiana State Climatologist has posted this article about what he found out about the station and how land cover change around a weather station can potentially influence its readings.
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Addendum/Correction to Crazy Warm Morning Temperatures This Past Summer
Barry Keim, Louisiana State Climatologist, Louisiana State University
I noted last week in the title of my article that the minimum temperatures were “crazy high.” Well, “crazy” only begins to describe the temperatures, what is likely affecting them, as well as the entire plight of this story over the past week.
What started out as my writing a folksy article on a whim, soon thereafter took wings. This story was simply inspired by a couple of “off the cuff” conversations with NWS personnel about the high number of 80°+ degree mornings experienced at the New Orleans International Airport (MSY). As a result, I snuck a peek at the data from the Airport for summer 2016 last Friday evening, then processed the number of 80°+ degree mornings over the period of record using some programs from the Southern Regional Climate Center, and off I went to writing what I thought was a human interest story. Well, the story was later “tweeted” out by my associate, Kyle Brehe at LSU, and it was picked up and recast in an article the Washington Post, which was then written up and cited by Nola.com.
As the scientific process played out, all of the flaws of the New Orleans Airport data were pointed out by numerous experts, from far and wide. Some of the issues at hand in the interpretation of the MSY data include economic/industrial growth along Airline Highway (U.S. 61) and the change in instrumentation at the site in the 1990s (installation of the ASOS station). Both of these examples likely influenced the trends and shifts in the data at the site, especially regarding temperature. Other weather aficionados correctly pointed out that surrounding weather stations were not showing the same level of extraordinary 80°+ degree mornings, though this past summer was hot and humid across the region. However, I would argue that the “smoking gun” regarding the unusually high number of 80°+ degree mornings at the Airport was presented by Brad Panovich, as well as Chip Knappenberger. If Brad Panovich’s name sounds familiar, it’s because he once worked for WWL-TV as an on-air meteorologist, and he is now the Chief Meteorologist at the NBC affiliate in Charlotte, NC. What they showed was the dramatic change in land use surrounding the weather station at the Airport, which stems from the construction of a new terminal for MSY. Figure 1 shows what the landscape looked like on August 25, 2015 compared to August 31, 2016 (Figure 2), and in each image the location of the ASOS station is designated by the arrow. The difference in the landscape is dramatic to say the least, and the construction site quite clearly influenced the weather data. As shown, what was once mostly a grassy meadow surrounded by airport runways, was carved up with makeshift roadways and landfill as the site was readied for construction. This has clearly altered the energy exchanges at the site, leading to an enhancement in the minimum temperatures by reducing the amount of evaporation and transpiration, changing the surface color (known as the albedo), and the heat storage capacity of the surface. The bottom line is that the official data from the “flagship” station for New Orleans is clearly flawed for this past summer due to this construction around the weather station, and all of these records need to be noted with an asterisks, or simply removed altogether. I note that I flew out of New Orleans Airport in June and I honestly don’t remember seeing all of that construction. Furthermore, we have had related peculiar weather here in Baton Rouge as well, as we went for 111 straight days with minimum temperatures at or above 70 degrees (from June 9 to September 27) shattering the previous record of 98 straight days from summer 1977. This example from New Orleans is but one of the many complexities in the interpretation of weather and climate data, which keeps climate data and its interpretation a prominent research area. And just to point out, “science” is a quest for the truth, and in this case, the truth prevailed. E-mail me with questions or feedback at keim@lsu.edu.
