In the Northwestern US, 2011 has not been a fun year. At least it hasn’t been if you want to be outside enjoying the weather. I have been tracking the temperature and the anomaly for two locations. One is the urban Boise, Idaho area and the other is a low impact, non urban area. This is a good way to show the Urban Heat Island effect and to also show how daily temperature data is converted into sterile anomaly data.
One reason people are unhappy around here with the weather is that it has not been warm. So far in 2011 there have been 2 days over 25 °C. As recently as a couple of days ago the high temperature was 11 °C. McCall has not even had it that nice as it has had only two days this year above 20 °C. Here are the daily temperatures as calculated in the same manner as used to determine the station data.
There is a high degree of correlation between the two locations. The anomaly is calculated by taking the daily temperature and then subtracting the historical average daily temperature. It does not tell you at all if the anomaly (high or low) was from the high temperature or the low temperature. It is simply the difference between the two numbers.
In this manner it doesn’t matter that one is colder than the other. It is simply the deviation from the average temperature that is used to determine the anomaly temperature. It is also clear that both locations are having a below average year.
This doesn’t indicate if the anomaly happened with the high temperature or the low temperature. It can be shown though and the results show something that the regular anomaly fails to show.
Boise itself is having slightly above average temperatures at night (low temp), the difference is the very large negative anomaly in the daily high temperatures. The high temperature anomaly is -2.2 °C for the year. The anomaly that will be used for the official climate data is only -0.8 °C. That is because of the closer to normal night time temperatures.
The low impact station in the study shows that it has been the high temperature that has been decimated so far this year as well, although the night time temperatures are still below average.
McCall is showing the high temperatures as -3.9 °C below average while the the low anomaly is only -1.1 °C. That difference in temperature anomaly between the locations has been fairly stable for the year so far at 1.7 °C. That difference is likely caused by the impact of measuring temperature in an urban location.
Now that I have all the tools in place I might add some other locations to this type of analysis later on this year. It is interesting to see how the anomaly differs from the perception that people will have of the weather. People remember nice days. Since those have been greatly lacking in these locations the perception is that it has not warmed up at all. Certainly May has been warmer than April, just not as much as it should have been.