Post by tommyFL on Feb 24, 2022 0:16:42 GMT -5
I've always been interested in how the true daily mean temp (computed from hourly or sub-hourly observations) compared to the traditional mean temp as calculated by NOAA and the WMO (the average of the daily max and min temps). I chose to use USCRN stations since both types of mean temps are already calculated for each month, the stations are high quality, and it's easy to access lots of data very quickly. I then mapped the annual values, where a positive mean bias implies the true daily mean is warmer than the max and min temps would suggest and a negative bias suggests the true mean temp is cooler. USCRN mean temps are calculated from 5-minute observations.
In general, more humid areas are cold-biased, while dry areas are warm-biased. Increasing latitude seems to increase warm bias as well, while exposed mountain locations are mostly cold-biased. The very low value in Southern CA is from a mountain station, the only station in the region. It's unlikely the region as a whole is cold-biased to this extent, so this is not representative. Note that these values are strongly seasonal in most cases. In the absence of a strong precipitation peak, high sun months are the most warm-biased and low sun months the most cold-biased. This is easy to understand as the temp spends more time closer to the max temp when days are longest, and vice versa. In climates with a seasonal precipitation pattern, the wetter months are often cold-biased. Dry valleys are the most warm-biased locations in general (see the Rio Grande valley in New Mexico, Death Valley in California, and the Uintah Basin in Utah).
If there is any interest, I can post maps for different months/seasons or data for specific stations. Also, if you have performed similar calculations for stations in your area, please share.
In general, more humid areas are cold-biased, while dry areas are warm-biased. Increasing latitude seems to increase warm bias as well, while exposed mountain locations are mostly cold-biased. The very low value in Southern CA is from a mountain station, the only station in the region. It's unlikely the region as a whole is cold-biased to this extent, so this is not representative. Note that these values are strongly seasonal in most cases. In the absence of a strong precipitation peak, high sun months are the most warm-biased and low sun months the most cold-biased. This is easy to understand as the temp spends more time closer to the max temp when days are longest, and vice versa. In climates with a seasonal precipitation pattern, the wetter months are often cold-biased. Dry valleys are the most warm-biased locations in general (see the Rio Grande valley in New Mexico, Death Valley in California, and the Uintah Basin in Utah).
If there is any interest, I can post maps for different months/seasons or data for specific stations. Also, if you have performed similar calculations for stations in your area, please share.
