Degree Type

Thesis

Date of Award

2018

Degree Name

Master of Science

Department

Geological and Atmospheric Sciences

Major

Meteorology

First Advisor

William Gallus

Abstract

Nocturnal Mesoscale Convective Systems (MCS) are frequent over the Great Plains in the summer, and the Great Plains low-level jet (LLJ) is a contributing factor to their initiation and evolution. Moisture brought in by the LLJ plays a key role in the formation and sustenance of MCSs. Thus, the ability of models to depict specific humidity as well as equivalent potential temperature (πœƒπ‘’) flowing into the region where convection initiates is likely to play a role in how accurately they forecast MCSs. The Weather Research and Forecasting (WRF) model was used to examine the relationship between displacement errors for the initiating MCSs, and moisture and temperature errors that were present up to three hours before initiation upstream of the MCSs in WRF model simulations. A total of 18 cases are examined and differentiated into two groups based on a strongly and weakly forced synoptic environment. Rapid Update Cycle (RUC) analyses were used to represent observations, and all analyses were focused in 3 layers below 1500 m AGL. The WRF was configured to use the Thompson microphysics scheme and 2 planetary boundary layer (PBL) schemes (Yonsei University (YSU) and Mellor-Yamada-Janjic (MYJ)). Correlations were explored and discovered in regions near and upstream of both observed and simulated MCSs between the mean errors of both moisture variables, and the distances between simulated and observed MCS initiations. Correlations varied depending on the synoptic environment. A large dry bias resulting in a simulated MCS initiating further downstream from the observed MCS with respect to the low-level flow in a strongly forced-synoptic regime, to a small dry bias resulting in a simulated MCS to initiate far the observed MCS with respect to the left or right direction of the inflow direction (in a weakly forced-synoptic regime). The statistically significant correlations were present at all times examined, suggesting that forecasters might

be able to anticipate how to adjust a WRF forecast based on the errors seen a few hours prior to MCS initiation.

Copyright Owner

Nicholas Vertz

Language

en

File Format

application/pdf

File Size

47 pages

Included in

Meteorology Commons

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