Type
Text
Type
Dissertation
Advisor
Khairoutdinov, Marat | Geller, Marvin | Colle, Brian | Chang, Edmund | Bryan, George.
Date
2015-12-01
Keywords
Atmospheric convection, Atmospheric thermodynamics, Cloud Resolving Model, Conditional instability, Mesoscale convective systems, Mesoscale dynamics | Atmospheric sciences
Department
Department of Marine and Atmospheric Science.
Language
en_US
Source
This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree.
Identifier
http://hdl.handle.net/11401/77785
Publisher
The Graduate School, Stony Brook University: Stony Brook, NY.
Format
application/pdf
Abstract
The structural dependence of quasi-linear mesoscale convective systems, herein referred to as squall lines (SLs), on the characteristics of the embedding environment is investigated, contemplating the latent instability properties of air throughout the atmospheric column. The focus of this thesis is on idealized SLs, simulated in tropical and mid-latitude environments with the System for Atmospheric Modeling. The soundings used for simulating storms are specified using an original method, in which temperatures and moisture are prescribed primarily via vertical profiles of the convective available potential energy (CAPE) and the level of free convection (LFC). Analyses are based on latent instability concepts and the layer-lifting conceptual model, emphasizing inter-comparisons among simulated storms. Results show that the precipitable water accounts for much of the precipitation rate variation for a given strength of the low level shear, irrespective of the CAPE profile. The precipitation efficiency is lower in the environments with weaker shear and dryer mid-tropospheric conditions. A key finding is that, while frequently used CAPE indices are generally unsuitable for diagnosing SL characteristics, the integrated CAPE (ICAPE) is an environmental diagnostic which, for a given value of environmental shear, discriminates the amplitude of the storm induced heating. The skill of ICAPE follows from its relation to the buoyancy attained by the low and mid-tropospheric parcels as they ascend over the cold pool through layer-lifting convection. The dependence of the storm induced heating on environmental kinematics is also explained via the layer-lifting model, as the low level shear modulates the fraction of inflowing latent unstable air among the total storm relative inflow. Mid-latitude storms are weakly affected by LFC variations for a given CAPE profile, while the sensitivity of tropical SLs to the LFC is more noticeable, possibly due to their relatively shallow cold pools. It is shown that cold pool shear-balance does not robustly predict the verticality of updrafts or the intensity of storm attributes within varying thermodynamic environments. Two-dimensional simulations using a simplified microphysics scheme confirm that latent instability variations can substantially affect the verticality and intensity of simulated updrafts, for a given degree of cold pool-shear balance. These simulations also indicate that the propagation speed of SLs is weakly affected by the amplitude of the storm induced heating, in contrast to steady analytical models of organized convection. | 177 pages
Recommended Citation
Alfaro Berea, Diego Adolfo, "Modulation of Mesoscale Convective Systems by Environmental Kinematics and Thermodynamics" (2015). Stony Brook Theses and Dissertations Collection, 2006-2020 (closed to submissions). 3563.
https://commons.library.stonybrook.edu/stony-brook-theses-and-dissertations-collection/3563