Cold pool processes in different environments
| dc.contributor.author | Grant, Leah Danielle, author | |
| dc.contributor.author | van den Heever, Susan C., advisor | |
| dc.contributor.author | Randall, David A., committee member | |
| dc.contributor.author | Rutledge, Steven A., committee member | |
| dc.contributor.author | Niemann, Jeffrey D., committee member | |
| dc.date.accessioned | 2018-06-12T16:13:44Z | |
| dc.date.available | 2018-06-12T16:13:44Z | |
| dc.date.issued | 2018 | |
| dc.description.abstract | Cold pools are localized regions of dense air near Earth's surface. They form in association with precipitating clouds in many environments ranging from moist tropical to semi-arid continental conditions, and they play important roles in weather in climate. The overarching goal of this dissertation research is to improve our process-level understanding of cold pool interactions with different components of the Earth system, focusing on two key knowledge gaps: (1) interactions with Earth's surface in continental environments; and (2) interactions with organized convective systems in tropical oceanic environments. The primary goal of the first study conducted in this dissertation is to evaluate how surface sensible heat fluxes impact cold pool dissipation in dry continental environments via two pathways: (a) by directly heating the cold pool, and (b) by changing mixing rates between cold pool air and environmental air through altering turbulence intensity. Idealized 2D simulations of isolated cold pools are conducted with varying sensible heat flux formulations to determine the relative importance of these two mechanisms. The results demonstrate that the impact of sensible heat fluxes on mixing, i.e. mechanism (b), contributes most significantly to cold pool dissipation. Cold pool – land surface interactions in semi-arid continental conditions are investigated in the second study. Two questions are addressed: (1) how does the land surface respond to the cold pool; and (2) to what extent do land surface feedbacks modulate the cold pool evolution? Idealized 3D simulations of a cold pool evolving in a turbulent boundary layer are conducted to answer these questions. The land surface cools in response to the cold pool, resulting in suppressed sensible heat fluxes in the center of the cold pool. However, sensible heat fluxes are enhanced near the edge of the cold pool in association with higher wind speeds, leading to cold pool dissipation from the edge inwards. The land surface interactions are shown to strongly affect the cold pool, reducing its lifetime, size, and intensity by up to 50%. Preliminary analysis of a cold pool that was observed in northeastern Colorado on 17 May 2017 ("The Bees Day") during the C3LOUD-Ex field campaign is presented in the third study. The observed case exhibits similar environmental and cold pool characteristics to the first two numerical studies, thereby providing observational context for their hypotheses and conclusions. The objective of the fourth study presented in this dissertation is to determine the role of cold pools in organized tropical oceanic convective systems. To address this goal, two convective systems embedded in a weakly sheared cloud population approaching radiative-convective equilibrium are simulated at high resolution. The cold pools are weakened in the sensitivity tests by suppressing evaporation rates below cloud base. Both of the convective systems respond in a consistent manner as follows: (a) when cold pools are weakened, the convective intensity increases; and (b) the mesoscale structure, propagation speeds, and system lifetimes are insensitive to the changes in the cold pools, in contrast to the prevailing (RKW) theory that cold pools are critical to the mesoscale organization of convective systems. In summary, these high-resolution modeling and observational studies demonstrate new insights into cold pool – surface – convection interactions. The results suggest that cold pool interactions with different components of the Earth system are not all created equally; rather, these interactions depend on the environment in which the cold pools find themselves. | |
| dc.format.medium | born digital | |
| dc.format.medium | doctoral dissertations | |
| dc.identifier | Grant_colostate_0053A_14636.pdf | |
| dc.identifier.uri | https://hdl.handle.net/10217/189266 | |
| dc.language | English | |
| dc.language.iso | eng | |
| dc.publisher | Colorado State University. Libraries | |
| dc.relation.ispartof | 2000-2019 | |
| dc.rights | Copyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright. | |
| dc.subject | convective processes | |
| dc.subject | surface fluxes | |
| dc.subject | turbulence | |
| dc.subject | land - atmosphere interactions | |
| dc.subject | cold pools | |
| dc.subject | tropical convective systems | |
| dc.title | Cold pool processes in different environments | |
| dc.type | Text | |
| dcterms.rights.dpla | This Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). | |
| thesis.degree.discipline | Atmospheric Science | |
| thesis.degree.grantor | Colorado State University | |
| thesis.degree.level | Doctoral | |
| thesis.degree.name | Doctor of Philosophy (Ph.D.) |
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