Investigating Arctic Cyclone-Tropopause Polar Vortex Interactions with Observing System Simulation Experiments
| dc.contributor.advisor | Cavallo, Steven | |
| dc.contributor.author | Bray, Matthew | |
| dc.contributor.committeeMember | Parsons, David | |
| dc.contributor.committeeMember | Wang, Xuguang | |
| dc.date.accessioned | 2023-05-09T14:50:47Z | |
| dc.date.available | 2023-05-09T14:50:47Z | |
| dc.date.issued | 2023-05-12 | |
| dc.date.manuscript | 2023-04 | |
| dc.description.abstract | Tropopause polar vortices (TPVs) are upper-level cyclonic circulations that are common in high latitudes. TPVs most directly impact weather at the surface by providing baroclinic forcing for the development of Arctic cyclones (ACs), surface low-pressure systems over the Arctic Ocean and surrounding landmasses. ACs, in turn, help to drive the Arctic heat and moisture budgets via transport from the midlatitudes and govern sea ice variability on short timescales via dynamic and thermodynamic influences. Although prior studies have demonstrated and examined the link between TPVs and ACs, the exact role played by the TPV and its characteristics in the development of the surface cyclone has yet to be established. In the present study, we seek to take a step forward toward closing this gap using an idealized observing system simulation experiment (OSSE). This approach involves simulating dense dropsondes over a TPV as a surface cyclone is forming and examining the changes that the additional observations produce to the TPV and resulting surface cyclone. The ECMWF Cubic Octahedral grid Nature Run (ECO1280) is taken as the truth for the OSSE (all observations are simulated from the output of this model), and the Model for Prediction Across Scales (MPAS) is coupled with the Data Assimilation Research Testbed's (DART) ensemble adjustment Kalman filter in order to run numerical experiments. It is expected that the development of the TPV and surface cyclone will be especially sensitive to moisture observations, which influence TPV strength via diabatic processes, and that proper representation of mesoscale dynamic features along the tropopause will be key to accurate forecasts. In addition to a control in which only existing observations are simulated from ECO1280, we conduct four primary experiments assimilating additional dropsonde observations of (1) temperature, (2) humidity, (3) temperature and humidity, and (4) temperature and humidity over a broad region. All of the experiments reduce errors relative to the control throughout the atmosphere and at the surface, with Experiment 4 producing the most accurate forecast of the surface cyclone. The humidity observations lead to enhanced PV generation near the tropopause and, by the end of the forecast, a deeper surface cyclone. These improvements are more limited when temperature and humidity dropsondes are combined. Experiment 4 exhibits a much more accurate representation of the PV features surrounding the main TPV and other synoptic scale features surrounding the system (including a Rossby wave breaking into the Arctic from the midlatitudes), which may explain its better forecast performance with respect to the surface cyclone. Additionally, it is discovered that AC strength is linked to the accuracy of the modeled distance between the surface cyclone and the core of the TPV throughout its lifetime (an indicator of baroclinic growth potential). This TPV-AC distance is, in turn, controlled by a breaking midlatitude Rossby wave that was not directly observed in any of the experiments. | en_US |
| dc.identifier.uri | https://shareok.org/handle/11244/337606 | |
| dc.language | en_US | en_US |
| dc.subject | Atmospheric Sciences | en_US |
| dc.subject | Meteorology | en_US |
| dc.subject | Geophysical Fluid Dynamics | en_US |
| dc.subject | Polar Studies | en_US |
| dc.thesis.degree | Master of Science | en_US |
| dc.title | Investigating Arctic Cyclone-Tropopause Polar Vortex Interactions with Observing System Simulation Experiments | en_US |
| ou.group | College of Atmospheric and Geographic Sciences::School of Meteorology | en_US |
| shareok.nativefileaccess | restricted | en_US |
| shareok.orcid | 0009-0002-6444-4383 | en_US |