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The Impact Of North Pacific And North Atlantic Baroclinic Cyclones On Downstream Predictability, Adam Wayne Sisco
The Impact Of North Pacific And North Atlantic Baroclinic Cyclones On Downstream Predictability, Adam Wayne Sisco
Legacy Theses & Dissertations (2009 - 2024)
Baroclinic cyclogenesis can act as an impulsive disturbance along the midlatitude waveguide and promote the dispersion of Rossby waves, potentially impacting the predictability of the downstream midlatitude flow. Indeed, several studies have traced medium-range forecast errors and uncertainties to upstream cyclone development, especially when diabatic processes are involved in modifying the upper-tropospheric potential vorticity (PV) distribution. However, it remains unclear why some forecasts downstream of cyclogenesis are particularly uncertain while others are not. This study uses a 30-yr (1985–2014) sample of cool-season North Pacific and North Atlantic baroclinic cyclones and forecasts from the second-generation Global Ensemble Forecast System (GEFS) reforecast …
Examining The Impact Of Synoptic-Scale Waves On Stratospheric Polar Vortex Variability From An Ensemble Forecast Perspective, Michael E. Main
Examining The Impact Of Synoptic-Scale Waves On Stratospheric Polar Vortex Variability From An Ensemble Forecast Perspective, Michael E. Main
Legacy Theses & Dissertations (2009 - 2024)
Major Sudden Stratospheric Warming (SSW) events are characterized by rapid warming of the polar regions at 10 hPa and are accompanied by a reversal of the 10-hPa zonal-mean zonal wind at 60˚N from westerly to easterly. Following an SSW event, stratospheric thermal and momentum anomalies can progress downward and linger near the tropopause for up to 60 days. These anomalies have major impacts on tropospheric sensible weather including increased likelihood of cold air outbreaks and heavy precipitation events. SSW events are largely forced by upward propagation of planetary-scale Rossby waves from the troposphere to the stratosphere. Synoptic-scale waves can contribute …
The Significance Of The Nontraditional Coriolis Terms In Tropical Large-Scale Dynamics, Heng Wang
The Significance Of The Nontraditional Coriolis Terms In Tropical Large-Scale Dynamics, Heng Wang
Legacy Theses & Dissertations (2009 - 2024)
The nontraditional Coriolis terms (NCTs) turn eastward motion upward and upward motion westward, and vice versa. NCTs are omitted in most of the current global atmospheric models. However, NCTs are significant in tropical large-scale dynamics in at least three aspects. 1) Using an idealized model that can switch NCTs on or off, omitting NCTs biases large-scale flow response to prescribed diabatic forcing mimicking the intertropical convergence zone (ITCZ). The omission yields a westerly wind bias in the heating region ~ 10% of the westerly jet stream. This bias is due to lack of westward NCT when heating-induced upward motion is …
The Impact Of Warm Conveyor Belt Forecast Uncertainty On Downstream Predictability, Jeremy Berman
The Impact Of Warm Conveyor Belt Forecast Uncertainty On Downstream Predictability, Jeremy Berman
Legacy Theses & Dissertations (2009 - 2024)
Perturbations to the potential vorticity (PV) waveguide can lead to the downstream radiation of Rossby waves, and in turn high-impact weather events. The PV waveguide is often perturbed in association with cyclogenesis, largely due to the latent heat release within the cyclone’s warm conveyor belt (WCB). Previous studies have hypothesized that forecast uncertainty associated with diabatic heating in WCBs can result in large downstream forecast variability; however these studies have not established a direct connection between the two. This hypothesis is evaluated for six cyclogenesis events characterized by highly amplified flow over the North Atlantic using ensemble model simulations.
Variability Of African Easterly Waves, Yuan-Ming Cheng
Variability Of African Easterly Waves, Yuan-Ming Cheng
Legacy Theses & Dissertations (2009 - 2024)
African Easterly Waves (AEWs) are the most important rain modulators in the sub-Saharan Africa and precursors for tropical cyclone genesis in the Atlantic. While most previous studies have focused on the mean structure and dynamics of AEWs, evidence has shown that AEWs can vary substantially in terms of their structure and characteristics. Therefore, the overarching goal of this dissertation is to document the variability of AEWs and understand its causes. The goal is accomplished through two different but complementary approaches: (1) statistical analysis and (2) vorticity tracking.
16-Day Free-Traveling Rossby Waves And Their Association With Northern Hemisphere Blocking, Ernesto W. Findlay
16-Day Free-Traveling Rossby Waves And Their Association With Northern Hemisphere Blocking, Ernesto W. Findlay
Legacy Theses & Dissertations (2009 - 2024)
An analysis of the 16-day free Rossby wave is performed. The behavior of this wave includes a barotropic vertical structure that is independent of local forcing. An Empirical Orthogonal Function (EOF) analysis was performed on 15–30-day filtered geopotential height anomalies to extract the spatial patterns of the wave. Results show that the first two EOFs are in quadrature with each other, representing a westward moving signal with an average period of around 23 days and a phase velocity of. The Principal Components (PCs) from these EOFs were used to construct a 16-day wave index, which was employed as a tool …
An Analysis Of The Linkages Between Large-Scale Flow Regime Transitions On The Spatiotemporal Distribution Of Clustered Extratropical Cyclone Events Over The Northern Hemisphere, Eric Merton John Bunker
An Analysis Of The Linkages Between Large-Scale Flow Regime Transitions On The Spatiotemporal Distribution Of Clustered Extratropical Cyclone Events Over The Northern Hemisphere, Eric Merton John Bunker
Legacy Theses & Dissertations (2009 - 2024)
An Analysis of the Linkages Between Large-Scale Flow Regime Transitions on the Spatiotemporal Distribution of Clustered Extratropical Cyclone Events over the Northern Hemisphere
Global Response To The Madden-Julian Oscillation As A Function Of Phase Speed In Era-Interim Reanalysis And Miroc5 Model Data, Kaitlyn Krzyzaniak
Global Response To The Madden-Julian Oscillation As A Function Of Phase Speed In Era-Interim Reanalysis And Miroc5 Model Data, Kaitlyn Krzyzaniak
Legacy Theses & Dissertations (2009 - 2024)
Many authors state that the phase speed of the Madden–Julian oscillation (MJO) is near 5ms–1, but observations suggest it varies considerably. MJO propagation typically sets off Rossby wave trains that interact with and alter this extratropical pattern; however, differences in the MJO phase speed could alter the Rossby wave response, leading to a unique response in the extratropics. An understanding of the mechanisms and extratropical responses to variable MJO phase speeds would provide innovative and invaluable insight for subseasonal forecasting.
Agricultural Drought Transition Periods In The United States Corn Belt Region, Nicholas Joseph Schiraldi
Agricultural Drought Transition Periods In The United States Corn Belt Region, Nicholas Joseph Schiraldi
Legacy Theses & Dissertations (2009 - 2024)
Agricultural drought in the U.S. Corn Belt region (CBR) has tremendous global socioeconomic implications. Unfortunately, the weather and climate factors that contribute to transition events toward or away from such droughts, and how well those factors are predicted, are poorly understood. This dissertation focuses on the atmospheric circulation signals associated with agricultural drought transitions periods in the CBR that evolve over 20 and 60 days, and how well those circulation signals are predicted on seasonal to sub-seasonal time scales.
Rossby Wave Breaking And Widespread Extreme Precipitation Events In The Central And Eastern U.S, Benjamin John Moore
Rossby Wave Breaking And Widespread Extreme Precipitation Events In The Central And Eastern U.S, Benjamin John Moore
Legacy Theses & Dissertations (2009 - 2024)
This dissertation examines climatological and dynamical linkages between widespread extreme precipitation events (EPEs) in the central and eastern U.S. and Rossby wave breaking (RWB), and assesses forecast skill for EPEs occurring in conjunction with RWB. The analysis primarily focuses on linkages of EPEs to LC1 (anticyclonic) and LC2 (cyclonic) RWB.
Associations Between The Madden-Julian Oscillation, Equatorial Rossby Waves, And Extratropical Northern Hemisphere Predictability, Lawrence Gloeckler
Associations Between The Madden-Julian Oscillation, Equatorial Rossby Waves, And Extratropical Northern Hemisphere Predictability, Lawrence Gloeckler
Legacy Theses & Dissertations (2009 - 2024)
The Madden-Julian oscillation (MJO), the leading mode of tropical convective and circulation variability on intraseasonal time scales, has become increasingly leveraged to improve empirical prediction of the global atmospheric circulation. Significant progress has been made in recent years to advance subseasonal (10-30-day) prediction of atmospheric circulation anomalies, and much of this progress can be attributed to the inclusion of information about the phase and amplitude of the MJO in various forecast processes. Despite this progress, however, forecasts based only on the state of the MJO omit information about other important tropical convective and circulation anomalies, and coherent MJO signals are …
On The Mjo And Anticyclonic Wavebreaking, Kyle Macritchie
On The Mjo And Anticyclonic Wavebreaking, Kyle Macritchie
Legacy Theses & Dissertations (2009 - 2024)
The Madden Julian oscillation (MJO) is the primary mode of intraseasonal variability in the tropics. The MJO often couples with convection as it moves over the Indian Ocean and decouples as it leaves the west Pacific Ocean. The association between convection coupled to the MJO and the midlatitude flow pattern has been the primary focus of numerous studies. In particular, it has been shown that there is a statistical relationship between the position and strength of the MJO and anticyclonic wavebreaking (AWB). This study expands on this statistical relationship by examining, in detail, the two-way relationship between the MJO and …
The Downstream Extratropical Flow Response To Recurving Western North Pacific Tropical Cyclones, Heather M. Archambault
The Downstream Extratropical Flow Response To Recurving Western North Pacific Tropical Cyclones, Heather M. Archambault
Legacy Theses & Dissertations (2009 - 2024)
The factors that govern the downstream flow response to recurving western North Pacific (WNP) tropical cyclones (TCs) are investigated from climatological, composite analysis, case study, and predictability perspectives. A 1979–2009 climatology of WNP TC recurvature indicates that TC recurvature is followed by a four-day period of above-normal North Pacific meridional flow. The relationship between TC recurvature and above-normal North Pacific meridional flow is found to be stronger in late summer through mid-fall than in early summer and early winter, and stronger for TCs that interact strongly with the jet stream than for TCs that interact weakly with the jet stream. …