| dc.identifier.uri | http://hdl.handle.net/11401/77773 | |
| dc.description.sponsorship | This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree. | en_US |
| dc.format | Monograph | |
| dc.format.medium | Electronic Resource | en_US |
| dc.language.iso | en_US | |
| dc.publisher | The Graduate School, Stony Brook University: Stony Brook, NY. | |
| dc.type | Dissertation | |
| dcterms.abstract | Extratropical cyclones are one of the main drivers of regional climate, and they play a dominant role in both the day-to-day weather and extreme events during cool season (November-March) over eastern North America and western Atlantic. A better understanding of the regional changes of extratropical cyclones under climate change is vital important for decision makers and the public to prepare for these changes and minimize the associated risks. This thesis provides a comprehensive study in the ability of climate and weather prediction models in simulating the variability of extratropical cyclones, the regional future changes of the extratropical cyclones, and their associated regional climate and extreme weather during cool season over eastern North America and western Atlantic. An automated tracking algorithm is employed to identify extratropical cyclones during cool seasons for 15 Coupled Model Intercomparison Project Phase 5 (CMIP5) models and reanalysis products. The model’s performance in simulating cyclones during the historical period is evaluated with respect to the results from reanalysis. The future changes in cyclone activities through 21st century are investigated for the high-emission future experiment of CMIP5 models forced by Representative Concentration Pathway 8.5 (RCP8.5) scenario. Although cyclone frequency along the storm track over eastern North America and western Atlantic decreases significantly in the future, intense cyclones along the U.S. East Coast have a slight increase, with more rapid deepening cases in the models. In addition to the frequency and intensity of extratropical cyclones, a cyclone relative approach is developed to explore the structure and intensity of precipitation within synoptic-scale cyclone systems in CMIP5 models. There is a large increase trend of precipitation associated with cyclones over eastern North America and western Atlantic through 21st century due to the significant increase in available moisture under global warming. The increase of precipitation mainly comes from relatively strong cyclones, while the increase from weak cyclones is inhibited by the decrease of cyclone frequency. Although the baroclinicity is decreasing under global warming, more cyclone cases are accompanied with more extreme precipitation events due to the positive feedback between latent heat release from precipitation and cyclone deepening over U.S. East Coast region. The coarse-resolution CMIP5 GCMs are able to simulate the large-scale structure of cyclones. However, they cannot resolve many terrain specific features and the high-impact mesoscale physical processes. To better understand the future changes in extratropical cyclone activities for regional applications, the global simulations of selected CMIP5 models are dynamically downscaled to develop high-resolution climate simulations over eastern North America and western Atlantic using Weather Research and Forecasting model (WRF). Although the cyclone frequency in WRF is dominated by the corresponding GCM, the high-resolution WRF can simulate cyclone intensity more realistically, while the cyclone intensity in the low-resolution WRF is closer to the GCM. During the future period, the low-level diabatic potential vorticity (DPV) becomes stronger while the baroclinicity is weaker in WRF, indicating that the enhanced latent heat release becomes more important to cyclone developing than the historical period. Meanwhile, the increase of extreme precipitation in WRF is much larger than the increase in GCM, although WRF overestimates the seasonal mean precipitation in the historical period. | |
| dcterms.abstract | Extratropical cyclones are one of the main drivers of regional climate, and they play a dominant role in both the day-to-day weather and extreme events during cool season (November-March) over eastern North America and western Atlantic. A better understanding of the regional changes of extratropical cyclones under climate change is vital important for decision makers and the public to prepare for these changes and minimize the associated risks. This thesis provides a comprehensive study in the ability of climate and weather prediction models in simulating the variability of extratropical cyclones, the regional future changes of the extratropical cyclones, and their associated regional climate and extreme weather during cool season over eastern North America and western Atlantic. An automated tracking algorithm is employed to identify extratropical cyclones during cool seasons for 15 Coupled Model Intercomparison Project Phase 5 (CMIP5) models and reanalysis products. The model’s performance in simulating cyclones during the historical period is evaluated with respect to the results from reanalysis. The future changes in cyclone activities through 21st century are investigated for the high-emission future experiment of CMIP5 models forced by Representative Concentration Pathway 8.5 (RCP8.5) scenario. Although cyclone frequency along the storm track over eastern North America and western Atlantic decreases significantly in the future, intense cyclones along the U.S. East Coast have a slight increase, with more rapid deepening cases in the models. In addition to the frequency and intensity of extratropical cyclones, a cyclone relative approach is developed to explore the structure and intensity of precipitation within synoptic-scale cyclone systems in CMIP5 models. There is a large increase trend of precipitation associated with cyclones over eastern North America and western Atlantic through 21st century due to the significant increase in available moisture under global warming. The increase of precipitation mainly comes from relatively strong cyclones, while the increase from weak cyclones is inhibited by the decrease of cyclone frequency. Although the baroclinicity is decreasing under global warming, more cyclone cases are accompanied with more extreme precipitation events due to the positive feedback between latent heat release from precipitation and cyclone deepening over U.S. East Coast region. The coarse-resolution CMIP5 GCMs are able to simulate the large-scale structure of cyclones. However, they cannot resolve many terrain specific features and the high-impact mesoscale physical processes. To better understand the future changes in extratropical cyclone activities for regional applications, the global simulations of selected CMIP5 models are dynamically downscaled to develop high-resolution climate simulations over eastern North America and western Atlantic using Weather Research and Forecasting model (WRF). Although the cyclone frequency in WRF is dominated by the corresponding GCM, the high-resolution WRF can simulate cyclone intensity more realistically, while the cyclone intensity in the low-resolution WRF is closer to the GCM. During the future period, the low-level diabatic potential vorticity (DPV) becomes stronger while the baroclinicity is weaker in WRF, indicating that the enhanced latent heat release becomes more important to cyclone developing than the historical period. Meanwhile, the increase of extreme precipitation in WRF is much larger than the increase in GCM, although WRF overestimates the seasonal mean precipitation in the historical period. | |
| dcterms.available | 2017-09-20T16:53:33Z | |
| dcterms.contributor | Colle, Brian A | en_US |
| dcterms.contributor | Chang, Edmund KM | en_US |
| dcterms.contributor | Zhang, Minghua | en_US |
| dcterms.contributor | Bowman, Malcolm J | en_US |
| dcterms.contributor | Lackmann, Gary M. | en_US |
| dcterms.creator | Zhang, Zhenhai | |
| dcterms.dateAccepted | 2017-09-20T16:53:33Z | |
| dcterms.dateSubmitted | 2017-09-20T16:53:33Z | |
| dcterms.description | Department of Marine and Atmospheric Science | en_US |
| dcterms.extent | 220 pg. | en_US |
| dcterms.format | Monograph | |
| dcterms.format | Application/PDF | en_US |
| dcterms.identifier | http://hdl.handle.net/11401/77773 | |
| dcterms.issued | 2016-12-01 | |
| dcterms.language | en_US | |
| dcterms.provenance | Made available in DSpace on 2017-09-20T16:53:33Z (GMT). No. of bitstreams: 1
Zhang_grad.sunysb_0771E_13079.pdf: 14320950 bytes, checksum: 654a6aa8a62fc18e846b46aec0f0136d (MD5)
Previous issue date: 1 | en |
| dcterms.publisher | The Graduate School, Stony Brook University: Stony Brook, NY. | |
| dcterms.subject | Atmospheric sciences | |
| dcterms.title | Future Changes in Extratropical Cyclones over Eastern North America and the Western Atlantic in Climate Models and a Downscaled Mesoscale Model | |
| dcterms.type | Dissertation | |
