Soil moisture impacts on convective margins.

Ben R. Lintner and J. David Neelin, 2009:
J. Hydrometeor., revised.

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Abstract. An idealized prototype for the location of the margins of tropical land region convection zones is extended to consider the effects of soil moisture and associated evaporation. The impact of evaporation, integrated over the inflow trajectory into the convection zone, is realized nonlocally where the atmosphere becomes favorable to deep convection. This integrated effect produces "hotspots" of land surface-atmosphere coupling downstream of soil moisture conditions. Overall, soil moisture increases the variability of the convective margin, although how it does so is nontrivial. In particular, there is an asymmetry in displacements of the convective margin between anomalous inflow and outflow conditions which is absent when soil moisture is not included. Furthermore, the simple cases presented here illustrate how margin sensitivity depends strongly on the interplay of factors including net top-of-the-atmosphere radiative heating, the statistics of inflow wind, and the convective parameterization.

Citation. Lintner, B. R. and J. D. Neelin: Soil moisture impacts on convective margins. J. Hydrometeor., revised, Feb. 2009.

Acknowledgments. The authors thank R. D. Koster and N. Zeng for insightful discussion and J. E. Meyerson for graphical assistance. This work was supported partly by National Oceanic and Atmospheric Administration NA05OAR4311134 and [CPPA2007] and National Science Foundation ATM-0645200. JDN acknowledges sabbatical support from the J. S. Guggenheim Memorial Foundation.