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Corn, CAPS & CAPE: Convective Climate in the Corn-Belt

Recent reasearch about agricultural practices in the upper Midwest have indicated that since the 1950's there has been a huge increase in acreage of Corn and Soybeams at the expense of Wheat, Pasture and other rural land use types. (See Sandstrom et al (2004), Physical Geography vol 25, No 3, pp. 191-207)

Corn and Soybeams extract soil moisture more agressively then many other crops, resulting in more of the daytime heating being used to pump up dew points at the expence of sensible heating. The result has been a statisticaly significant increase in the number of days with extreme dewpoints, but extreme daytime high temps may be supressed.

One might anticipate that more Corn and Soybeams mean stronger CIN and potentialy a more extreme CAPE climatology when cap strength supresses the development of early convection and allows more time for the buildup of extreme theta-e and CAPE.

One has to wonder how this might be effecting the climatology of severe convection in the upper Midwest. Although most strong tornadoes occur north of the Cornbelt in mid-summer, the atmospheric environment promoted by agressively transpiring plants would promote thunderstorms with low LCL's and these storms may be less likely to become outflow dominated as quickly as those occuring in environments with higher dew-point depressions. Is it possible that if storms take longer to become outflow dominant they might have a longer window for tornadogenesis? Many other questions about thunderstorm climatology could be asked

Does anyone have any thoughts on this, this could be an interesting topic.
 
To help this discussion, we should identify the states:

The US Cenus Bureau and many other studies refer to the Midwest containing the following states:
Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, and Wisconsin

The Corn Belt is not as clearly defined, but studies and maps I have run across usually includes these 12 states:
Illinois, Indiana, Iowa, Kansas, Kentucky, Michigan, Minnesota, Missouri, Nebraska, Ohio, South Dakota and Wisconsin.

To narrow it down, from various sources, the Corn Belt consist of the following 7 states:
Illinois, Indiana, Iowa, Minnesota, Nebraska, Ohio, South Dakota.

Mike
 
Adding to that the fact that almost all soybeans and corn fields are heavily irrigated in KS, CO, and NE, and you've certainly got an increase in moisture without contributing precipitation or "imported" moisture from the south.

With my father-in-law planting 3,000+ acres of corn each year, I'd say he's making a good contribution to my hobby :wink:

Tim
 
Re: Corn, CAPS & CAPE: Convective Climate in the Corn-Be

One might anticipate that more Corn and Soybeams mean stronger CIN and potentialy a more extreme CAPE climatology when cap strength supresses the development of early convection and allows more time for the buildup of extreme theta-e and CAPE.

After thinking about this - I'm not sure this is fair to say. It should depend on the height of the LCL/CCL, as if the LCL/CCL is below the cap, then adding moisture will get you through the cap more easily than sensible heating alone. It might be simpler to think in terms of equivalent potential temperature, and then you'd question whether this value has markedly changed over the the period when crops switched over to largely corn and soybeans. Another factor that you may need to consider is how the increased moisture may lead to greater cloud cover/haze, that subsequently limits the amount of surface heating and perhaps the probabilities for surface-based convection as a whole in that region. That said, the less solar energy that actually reaches the plants, the less evapotranspiration - so it is a somewhat self-limiting process.

From experience in living in the corn belt for a few years, it is when tasseling begins that the moisture really starts to crank up - which isn't until July around here. This is past peak severe weather season in these parts. 'Normal' weather patterns for that time of year would have southwest surface winds across the corn belt - so much of the added moisture is probably transported out of the Midwest, and may lead to modest increases in rainfall elsewhere.

Glen
 
It would not surprise me if agricultural evapotranspiration was partly responsible for the sudden phasing of parameters that led to the June 23 '04 Wisconsin outbreak.

From the 0100Z Day 1 Outlook issued on 6-24:

CONVECTION INVOF SURFACE LOW AND ON THE COLD FRONT NOW APPEAR TO BE TAPPING INTO AXIS OF RICHER LOW LEVEL MOISTURE ADVECTING INTO THE REGION FROM THE CORN BELT.
 
Cornbelt defined

To help this discussion, we should identify the states:

The Paper I mentioned shows the cornbelt as:
-E 1/4 of SD
-most of NE (except the NW)
-SW MN
-IA
-SW WI
-IL
-IN
-W part of OH

The soybeam areas are mostly the same, except for much of N MO where the map shows soybeams only.

The paper mentioned July and Aug as the peak months of water use for corn.
 
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