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Continuous Cropping and Moist Deep Convection on the Canadian Prairies
Eastern Cereal and Oilseed Research Center, Agriculture and Agri-Food Canada, 960 Carling Avenue, K. W. Neatby Building, Ottawa, ON K1A 0C6, Canada
Centre for Earth Observation Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
* Author to whom correspondence should be addressed.
Received: 29 August 2012; in revised form: 27 November 2012 / Accepted: 4 December 2012 / Published: 13 December 2012
Abstract: Summerfallow is cropland that is purposely kept out of production during a growing season to conserve soil moisture. On the Canadian Prairies, a trend to continuous cropping with a reduction in summerfallow began after the summerfallow area peaked in 1976. This study examined the impact of this land-use change on convective available potential energy (CAPE), a necessary but not sufficient condition for moist deep convection. All else being equal, an increase in CAPE increases the probability-of-occurrence of convective clouds and their intensity if they occur. Representative Bowen ratios for the Black, Dark Brown, and Brown soil zones were determined for 1976: the maximum summerfallow year, 2001: our baseline year, and 20xx: a hypothetical year with the maximum-possible annual crop area. Average mid-growing-season Bowen ratios and noon solar radiation were used to estimate the reduction in the lifted index (LI) from land-use weighted evapotranspiration in each study year. LI is an index of CAPE, and a reduction in LI indicates an increase in CAPE. The largest reductions in LI were found for the Black soil zone. They were −1.61 ± 0.18, −1.77 ± 0.14 and −1.89 ± 0.16 in 1976, 2001 and 20xx, respectively. These results suggest that, all else being equal, the probability-of-occurrence of moist deep convection in the Black soil zone was lower in 1976 than in the base year 2001, and it will be higher in 20xx when the annual crop area reaches a maximum. The trend to continuous cropping had less impact in the drier Dark Brown and Brown soil zones.
Keywords: Bowen ratio; convective available potential energy; moist deep convection; land-use change; summerfallow
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Shrestha, B.M.; Raddatz, R.L.; Desjardins, R.L.; Worth, D.E. Continuous Cropping and Moist Deep Convection on the Canadian Prairies. Atmosphere 2012, 3, 573-590.
Shrestha BM, Raddatz RL, Desjardins RL, Worth DE. Continuous Cropping and Moist Deep Convection on the Canadian Prairies. Atmosphere. 2012; 3(4):573-590.
Shrestha, Bharat M.; Raddatz, Richard L.; Desjardins, Raymond L.; Worth, Devon E. 2012. "Continuous Cropping and Moist Deep Convection on the Canadian Prairies." Atmosphere 3, no. 4: 573-590.