IEM Daily Feature
Wednesday, 18 April 2018
Wednesday, 18 April 2018
How to Warm the Soil
Posted: 18 Apr 2018 05:34 AM
Today's chart is a bit of a deep dive into drivers for changes in soil temperature. A big
current weather story is the cold soil temperatures statewide which are preventing crop
planting progress. The featured chart attempts to look into what it takes to produce
warmer soil temperatures, in particular four inch depth soil temperatures based on period
of record data from the Ames ISU AgClimate weather station during the month of April. In
focus is what may drive the day to day warming or cooling of soil temperatures. The top
two panels present the relationship between the day to day change in air temperature
and solar radiation with the response in day to day soil temperature. The bottom two
panels look more into the absolute relationship between these three parameters. One
may suggest that simply having sunny days are sufficient to increase soil temperatures.
While the bottom left panel does show a positive relationship (increasing radiation
increases the day to day temperature change), the correlation is a bit low and would
indicate other factors are at play. The upper left plot shows a stronger relationship
between day to day changes in air and soil temperatures, but this relationship is
physically complex via the surface energy budget. Energy will flow from warmer soils to
the air and from warmer air to the soil. During the spring time, a major source of warm air
is from wind transporting warmer air into the state and from daytime mixing of warmer air
aloft down to the surface. The moral of the story is that these plots seem to indicate that
air temperatures are more important of a driver of soil temperatures than solar input. One
could think of it this way, we just had our coldest 1-15 April period on record for air
temperatures not wholly due to a lack of sunshine, but from dominant cold air masses
being transported into the state. Of course, it also does not help to have snow covering
the ground which will be added to today, sigh!
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Tags: soiltemp
Voting:
Good = 10
Bad = 1
Tags: soiltemp