Convective response to changes in the thermodynamic environment in idealized weak temperature gradient simulations

Journal of Advances in Modeling Earth Systems

Sharon L. Sessions¹  Michael J. Herman¹ 

[1] Department of Physics and Geophysical Research Center, New Mexico Tech, Socorro, New Mexico, USA

关键词: weak temperature gradient approximation (WTG);    horizontal moisture advection;    multiple equilibria;    tropical convection;    thermodynamic environment;   

DOI  :  10.1002/2015MS000446

来源: Wiley

【 摘 要 】

Abstract

We investigate the response of convection to idealized perturbations in the thermodynamic environment in simulations which parameterize the large-scale circulations using the weak temperature gradient (WTG) approximation. The perturbations include a combination of modifying the environmental moisture and atmospheric stability via imposing anomalies in reference moisture and temperature profiles. We find that changes in atmospheric stability strongly influence the character of convection by drastically modifying the vertical motion profile, whereas changes to atmospheric moisture modulate the intensity of precipitation produced by the convection, but do not qualitatively change the shape of the vertical motion profile. An important question is how does horizontal moisture advection into the domain affect convection? We test several different parameterizations of this process; these include lateral entrainment by circulations induced by enforcing WTG, a moisture relaxation which parameterizes the advection of moisture by large-scale nondivergent circulations, and control simulations in which both of these mechanisms are turned off so horizontal advection is assumed negligible compared to vertical advection. Interestingly, the most significant differences resulting from the choice of horizontal moisture advection scheme appear in environmental conditions which suppress–rather than support–the development of deep tropical convection. In this case, lateral entrainment related to WTG circulations is the only parameterization which results in extreme drying of the troposphere in environments which suppress convection. Consequently, this is the only parameterization which permits multiple equilibria—dry or precipitating steady states—in convection.

【 授权许可】

CC BY-NC-ND   
© 2015. The Authors.

Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.