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Exploring the Contrast in Convective...

Hansen, Zachary R.

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Exploring the Contrast in Convective Intensity between Land and Ocean.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Exploring the Contrast in Convective Intensity between Land and Ocean./
Author:	Hansen, Zachary R.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2018,
Description:	141 p.
Notes:	Source: Dissertations Abstracts International, Volume: 80-06, Section: B.
Contained By:	Dissertations Abstracts International80-06B.
Subject:	Meteorology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=13423311
ISBN:	9780438740044

Exploring the Contrast in Convective Intensity between Land and Ocean.
Hansen, Zachary R.

Exploring the Contrast in Convective Intensity between Land and Ocean. - Ann Arbor : ProQuest Dissertations & Theses, 2018 - 141 p.

Source: Dissertations Abstracts International, Volume: 80-06, Section: B.

Thesis (Ph.D.)--The University of Wisconsin - Madison, 2018.

This item must not be sold to any third party vendors.

In this dissertation, we examined the influence of various physical mechanisms on the land-ocean contrast in convective intensity. The first mechanism is the impact of deeper boundary layers associated with land surfaces on convective intensity in cloud resolving model simulations. It is found that deeper boundary layers do not produce enhanced convective intensity when looking at metrics of high intensity vertical velocity. In one case, deeper boundary layers did show potential for convective intensity enhancement, as measured by the scale height of graupel dissipation in the column. We diagnosed the parcel entrainment being experienced in these simulations with a 1-D parcel model. Contrary to previous suggestions that entrainment should decrease significantly with increasing boundary layer depth, we found that entrainment was nearly unchanged in deeper boundary layer cases. This lack of change may be due to that fact that cloud widths do not increase with boundary layer depth when looking at levels higher than the lifting condensation level. The second mechanism analyzed was the enhanced diurnal cycle in surface temperature over land. It had been predicted that the enhanced diurnal cycle in conjunction with a free troposphere influenced by oceanic convection could lead to greater CAPE and convective intensity over land. We show that neither CAPE nor convective intensity are enhanced, once one accounts for differences in precipitation. The reason for this lack of enhancement is that our boundary layer dries as temperatures increase, preventing the boundary layer's moist static energy (MSE) from increasing. We analyzed this boundary layer quasi-equilibrium and found that convective downdrafts played the largest role in keeping MSE stationary, contrary to previous studies that had proposed boundary layer entrainment as the main contributor. The speed at which our equilibrium occurs is also much faster than had been previously found. Finally, we examine the impact of free tropospheric saturation deficit on convective intensity and CAPE in equilibrium and field campaign simulations. We find that increases in dryness can increase CAPE and convective intensity, even when precipitation doesn't increase. Field campaign simulations show that saturation deficit is a good predictor for maximum CAPE, and that high intensity updrafts are increasing with increasing CAPE. Further analysis of the geographic distribution of saturation deficits is needed to effectively evaluate its role in the land-ocean convective intensity contrast.

ISBN: 9780438740044Subjects--Topical Terms:

542822
Meteorology.

Exploring the Contrast in Convective Intensity between Land and Ocean.
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245 1 0 $a Exploring the Contrast in Convective Intensity between Land and Ocean.
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300 $a 141 p.
500 $a Source: Dissertations Abstracts International, Volume: 80-06, Section: B.
500 $a Publisher info.: Dissertation/Thesis.
500 $a Advisor: Back, Larissa E.
502 $a Thesis (Ph.D.)--The University of Wisconsin - Madison, 2018.
506 $a This item must not be sold to any third party vendors.
520 $a In this dissertation, we examined the influence of various physical mechanisms on the land-ocean contrast in convective intensity. The first mechanism is the impact of deeper boundary layers associated with land surfaces on convective intensity in cloud resolving model simulations. It is found that deeper boundary layers do not produce enhanced convective intensity when looking at metrics of high intensity vertical velocity. In one case, deeper boundary layers did show potential for convective intensity enhancement, as measured by the scale height of graupel dissipation in the column. We diagnosed the parcel entrainment being experienced in these simulations with a 1-D parcel model. Contrary to previous suggestions that entrainment should decrease significantly with increasing boundary layer depth, we found that entrainment was nearly unchanged in deeper boundary layer cases. This lack of change may be due to that fact that cloud widths do not increase with boundary layer depth when looking at levels higher than the lifting condensation level. The second mechanism analyzed was the enhanced diurnal cycle in surface temperature over land. It had been predicted that the enhanced diurnal cycle in conjunction with a free troposphere influenced by oceanic convection could lead to greater CAPE and convective intensity over land. We show that neither CAPE nor convective intensity are enhanced, once one accounts for differences in precipitation. The reason for this lack of enhancement is that our boundary layer dries as temperatures increase, preventing the boundary layer's moist static energy (MSE) from increasing. We analyzed this boundary layer quasi-equilibrium and found that convective downdrafts played the largest role in keeping MSE stationary, contrary to previous studies that had proposed boundary layer entrainment as the main contributor. The speed at which our equilibrium occurs is also much faster than had been previously found. Finally, we examine the impact of free tropospheric saturation deficit on convective intensity and CAPE in equilibrium and field campaign simulations. We find that increases in dryness can increase CAPE and convective intensity, even when precipitation doesn't increase. Field campaign simulations show that saturation deficit is a good predictor for maximum CAPE, and that high intensity updrafts are increasing with increasing CAPE. Further analysis of the geographic distribution of saturation deficits is needed to effectively evaluate its role in the land-ocean convective intensity contrast.
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