Date of Award
2018
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Atmospheric Science
Committee Chair
John R. Mecikalski
Committee Member
Eugene W. McCaul Jr.
Committee Member
Lawrence D. Carey
Committee Member
Kevin Knupp
Committee Member
Cameron R. Homeyer
Subject(s)
Atmospheric circulation., Convection (Meteorology), Geostationary satellites., Dynamic meteorology., Severe storms--Forecasting.
Abstract
Super Rapid Scan (SRS) Operations for the Geostationary Operational Environmental Satellite (GOES) R-series using GOES–14 have made experimentation with 1–min time step imagery possible prior to operational implementation of GOES–16 and beyond. With the vast improvement to temporal resolution, turbulence, outflow, and even rotation is now apparent over severe deep convection (DC). While the SRS imagery has been available since 2012, no attempt has yet been made to quantify and research these apparent flows. This dissertation explores techniques to develop an objective SRS flow-field derivation system to quantify apparent cloud-top horizontal divergence (CTD) and vertical vorticity (CTV) over DC. The relationship of CTD to DC updraft strength and severity is explored, as are the causes of apparent rotation signals over some supercell storms. A mesoscale atmospheric motion vector (mAMV) program is run on SRS data and multiple objective analysis schemes are used to produce flow fields over several DC case studies. These case studies were sampled by ground-based Doppler radar systems and very-high frequency total-lightning mapping arrays. Idealized DC simulations are also performed to compare apparent flow fields to physical flow fields. It is found that supercells have larger derived CTD than non-supercells, and in some cases, persistent adjacent CTV maxima and minima downstream of the primary updraft (termed the “CTV Couplet”) consistent with idealized physical flow-fields that originate from tilting and stretching downstream of the primary updraft (above 10 km). Objectively identified overshooting tops associated with DC and severe weather reports have stronger CTD than those without. The relationship between CTD and total lightning flash rate is non-linear, likely because CTD only reflects changes of the locally tallest (and typically strongest) updrafts. Variation in cloud-top height caused by features over DC such as the above-anvil cirrus plume can modify flows observed within this system, however they are not enough alone to create the rotation and divergence signals witnessed. The new capabilities explored here were only possible with ≤ 1¬–min scan rate imagery and offer new flow observation techniques to infer updraft strength and rotation of DC outside of regions covered with extensive radar networks.
Recommended Citation
Apke, Jason Merritt, "Using super rapid scan geostationary satellite data derived motion to improve understanding and observation of the dynamics of deep convection in the atmosphere" (2018). Dissertations. 145.
https://louis.uah.edu/uah-dissertations/145