MODIS 1km Surface Temp Obs

I’ve often wondered what the surface water temperatures of the various lakes are in the Huntsville CWFA.  We have some rather large lakes (Guntersville, Wheeler, Wilson) in our area, and these lakes can have sensible weather impacts on the nearby environment (e.g. the obvious lake vicinity temperature impacts, lake-induced fog, and belive it or not…a case of lake effect snow).  Knowing the differences between lake temperatures and land surface temperatures and environmental dew point temperatures can thus be beneficial.  However, without actually going down to the lake with a thermometer in hand and trying the old fashioned way, the MODIS imagery can serve as a reasonable alternative.  Here is an image I gathered from the other night…

Notice the data point marker, and the temperature reading of 84F on Lake Guntersville in central Marshall County, AL. The temperature seems reasonable, as it is just a few degrees above the actual average air temperature at Guntersville over the previous several weeks. Knowing this difference in lake water temperature and surrounding dew point temperature, for example, can help to determine the likelihood that fog will form over the lakes. This time of year, with the lakes now warmer than the dew point temperature…fog will often form during the overnight when winds and boundary layer mixing have subsided. Of course, the opposite can happen in the late winter and early spring, when warmer air settles across the cooler lakes. This can result in fog formation as well.

Also, since temperature measurements can be rather sparse over our area…especially rural locations, it is nice to have the 1km MODIS as a quick reference. For example, notice in the image below, the MODIS shows that the higher terrain was already considerably cooler than the lower elevations.

The data marker shows a temperature reading of 66F atop the higher terrain east of Lake Guntersville in western DeKalb County, AL. Unfortunately, there were no insitu observations in the vicinity available at the time. However, the next image with a data marker in eastern portions of DeKalb County shows a temperature reading of 68.2F…

Fortunately, a RAWS station situated at approximately 1200 ft atop the Little River Canyon corroborated the temperature of 68F at the time. Now, this may have limited benefits this time of year, but as the fall/winter approaches, the potential benefits will increase…especially when monitoring for subfreezing temperatures.

2 thoughts on “MODIS 1km Surface Temp Obs

  1. Kris,

    I enjoyed your perspective on the use of the MODIS Land Surface Temperature and found it insightful. I would enjoy seeing one of these fog or freezing examples posted to the blog when it occurs. Perhaps the use of this data in the GFE could be incorporated into a SmartTool that diagnoses lake fog or areas of freezing temperatures at high elevations.


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