This blog has described a number of examples of problematic surface temperature observations at a number of sites, with a recent blog noting issues at Yakima Airport in central Washington, where temperatures have consistently been too warm compared to other observing locations in the region. These problems have been obvious for several years.
The problem had to be the temperature sensor, since there was little urbanization in the area (see satellite map below).
The good news is that the National Weather Service has finally replaced the Yakima temperature sensor on May 8 and the problems seem to have been ameliorated. Let me show you the impact of the new sensor and show you more about this long-standing problem.
Here is the temperature anomaly (the difference from average) for daily average temperature over Washington State for the last three years. Repeat: three years. Temperatures have generally been above normal for the past three years over Washington, with one location being crazy warm (red color, 3-5F above normal). Which location? Yakima Airport.
Last two years? Yakima was too warm.
Last year? Yakima is again standing out as an anomalously warm location.
Last three months? Yakima is still very warm.
The last month, which only includes a short period with the bad sensor? The Yakima problem is almost non-existent.
The last week? The warm anomaly is gone!
The bottom line: it is clear Yakima had a bad temperature sensor for years and that replacing the unit corrected the issue.
But why did it take so long to identify this problem and swap out the sensor?
You might have noticed another problem station...a cool one..over the northeast side of Washington State. Perhaps a topic of a future blog.
from Cliff Mass Weather and Climate Blog https://ift.tt/2Hl4X0b
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