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Featured researches published by Shaowu Bao.


Monthly Weather Review | 2006

A Real-Time Hurricane Surface Wind Forecasting Model: Formulation and Verification

Lian Xie; Shaowu Bao; Leonard J. Pietrafesa; Kristen M. Foley; Montserrat Fuentes

A real-time hurricane wind forecast model is developed by 1) incorporating an asymmetric effect into the Holland hurricane wind model; 2) using the National Oceanic and Atmospheric Administration (NOAA)/ National Hurricane Center’s (NHC) hurricane forecast guidance for prognostic modeling; and 3) assimilating the National Data Buoy Center (NDBC) real-time buoy data into the model’s initial wind field. The method is validated using all 2003 and 2004 Atlantic and Gulf of Mexico hurricanes. The results show that 6- and 12-h forecast winds using the asymmetric hurricane wind model are statistically more accurate than using a symmetric wind model. Detailed case studies were conducted for four historical hurricanes, namely, Floyd (1999), Gordon (2000), Lily (2002), and Isabel (2003). Although the asymmetric model performed generally better than the symmetric model, the improvement in hurricane wind forecasts produced by the asymmetric model varied significantly for different storms. In some cases, optimizing the symmetric model using observations available at initial time and forecast mean radius of maximum wind can produce comparable wind accuracy measured in terms of rms error of wind speed. However, in order to describe the asymmetric structure of hurricane winds, an asymmetric model is needed.


IEEE Transactions on Geoscience and Remote Sensing | 2017

Ocean Upwelling Along the Yellow Sea Coast of China Revealed by Satellite Observations and Numerical Simulation

Shaowu Bao; Xiaofeng Li; Dongliang Shen; Zizang Yang; Leonard J. Pietrafesa; Weizhong Zheng

Satellite observations reveal that an ocean cooling event happened along the Yellow Sea coast of China intermittently in spring 2008, which lasted for days. During this period, the sea surface temperature (SST) dropped 3 °C-4 °C and the chlorophyll A (Chl-a) content increased by 0.5-1 mg/m3, as determined from satellite-derived products. The cold water also suppressed the sea surface capillary waves and made the ocean surface smooth, a distinct feature shown as dark patches observed in the synthetic aperture radar image acquired during this period of time. The surface wind direction varied between alongshore and offshore. We implemented an interactively coupled ocean (regional ocean modeling system) and atmosphere (Weather Research and Forecasting model) model to capture the dynamical processes of this seemingly wind-driven cooling event. When the wind changed direction such that the alongshore component blew with the land on its left side, stronger upwelling occurred; and when the wind blew offshore with no alongshore component, the upwelling still occurred in this area, but with less strength. Two simulations with idealized alongshore and offshore winds show that the upwelling can be set up within several hours. The alongshore wind is more effective than the offshore wind in transporting upper level water offshore and triggering upwelling and causing SST cooling areas that are relatively large in size, although the maximum SST cooling they cause is on the same order of magnitude.


IEEE Transactions on Geoscience and Remote Sensing | 2016

SAR Observation and Numerical Simulation of Mountain Lee Waves Near Kuril Islands Forced by an Extratropical Cyclone

Qing Xu; Xiaofeng Li; Shaowu Bao; Leonard J. Pietrafesa

Several groups of atmospheric gravity waves (AGWs) were observed on a Sentinel-1A synthetic aperture radar (SAR) image acquired near the Kuril Islands in the Northwest Pacific Ocean on June 1, 2015 during the passage of an extratropical cyclone (ETC). These waves occurred on the lee side of the mountains located on the islands. Both diverging and transverse waves with wavelengths ranging between 20 and 30 km are shown as alternating bright-dark patterns in the SAR image. For the diverging waves, there exists a prominent asymmetry in the wave motions of the two arms. The Moderate Resolution Imaging Spectroradiometer and Landsat 7 Enhanced Thematic Mapper Plus images acquired 5-7 h prior to the Sentinel-1A pass also contain the same groups of AGWs. The mesoscale Weather Research and Forecasting model simulation confirms that the AGWs are lee waves triggered by the airflow over the islands. AGWs are aligned perpendicular to the wind direction and locked on the lee side of the islands. The life span of the waves is about two days, consistent with that of the ETC over the region. The numerical model also successfully reproduces the main characteristics of the lee waves. Simulation results demonstrate that the variation in the wave parameters (i.e., wavelength, amplitude, orientation, wedge angle of the diverging wave, and vertical propagation characteristic) and the wave asymmetry of the diverging wave are mainly caused by the wind and stratification changes. The smaller amplitude of the diverging wave seems to be associated with a smaller Froude number.


Advances in Adaptive Data Analysis | 2010

NORTH ATLANTIC OCEAN BASIN TROPICAL CYCLONE ACTIVITY AS RELATED TO CLIMATE FACTORS FOR THE 2010 HURRICANE SEASON

Tingzhuang Yan; Leonard J. Pietrafesa; David A. Dickey; Shaowu Bao; Norden E. Huang; Zhaohua Wu

Atmospheric and oceanic climate factors and conditions play a crucial role in modulating seasonal/annual tropical cyclone activity in the North Atlantic Ocean Basin. In the following, correlations between North Atlantic tropical cyclone activity including frequency of occurrence and pathways are explored, with special emphasis on hurricanes. The value of two-dimensional and three-dimensional data sets representing climate patterns is investigated. Finally, the diagnostic study of historical tropical cyclone and hurricane temporal and spatial variability and relationships to climate factors lead to a statistical prognostic forecast, made in April, 2010, of the 2010 tropical cyclone and hurricane season. This forecast is tested both retrospectively and presently and is shown to be quite accurate. Knowing the probability of the frequency of occurrence, i.e. the numbers of named storms to form in general and the number of hurricanes (NHs) that are likely to form, is important for many societal sectors. However, the reliable forecasts of probable pathways of predicted events, specifically the likely NH land falls along the coastlines of the United States, should have great potential value to emergency planners, the insurance industry, and the public. The forecast provided in this study makes such a prognostication. As the 2010 hurricane season has progressed, an update of the goodness of the forecast is shown to be quite accurate in numbers of named events, hurricanes, major hurricanes (MHs), and landfalls. The mathematical and statistical methodology used in this study, which could be coupled to next generation empirical modal decomposition, suggests that this may signal a new era in the future of tropical cyclone forecasting, including the reliable prognostication of numbers of events, intensities of events, and the pathways of those events. The ability to reliably predict the probability and location of land falls of these destructive events would be very powerful indeed.


Modeling Earth Systems and Environment | 2018

Hurricane Matthew (2016) and its impact under global warming scenarios

Mansur Ali Jisan; Shaowu Bao; Leonard J. Pietrafesa; Dongliang Shen; Paul T. Gayes; Jason O. Hallstrom

A coupled atmosphere–ocean model was used to study the impact of future ocean warming, both at and below the water surface, on hurricane track and intensity and the associated coastal storm surge and inundation. A strong Saffir–Simpson Category-5 hurricane, Hurricane Matthew made landfall on the South Carolina (SC) coast of the United States (US) in September 2016 and was used as our study case. Future ocean warming was calculated based on the Inter-Governmental Panel on Climate Change (IPCC) RCP 2.6 and RCP 8.5 scenarios. Validated setup of the model was used to simulate the changes in track, intensity, storm surge, and inundation of Hurricane Matthew under future climate ocean warming scenarios. Results showed that the future ocean warming could make the hurricanes stronger in intensity, which, in turn, will greatly increase subsequent coastal storm surge and inundation. For example, under the RCP 8.5 scenario, Matthew’s maximum wind speed would increase by 18 knots (12.97%), its minimum sea-level pressure would deepen by 26xa0hPa (2.78%), and the coastal area inundated would increase by 70.20% from that of the present day. Moreover, the increases in coastal surge and inundation could likely lead to a downstream blocking of upstream water systems, thereby exacerbating upstream lateral flooding as the rivers go into storage modes; but that potential is beyond the scope of this study.


international geoscience and remote sensing symposium | 2016

SAR imaging and numerical simulation of upwelling processes near the coastal area of Qingdao in China

Len Pietrafesa; Shaowu Bao; Xiaofeng Li; Zizang Yang; Dongliang Shen; Weizhong Zheng

SST cooling episodes in the early Spring are often observed by various remote sensing measurement systems near the coast of Qingdao, a city in Chinas Shandong province (Figure 1). Several wind-SST interaction mechanisms that can cause colder deep water to force its way upward and drive away and subsequently replace the warmer surface water, also known as upwelling, have been previously documented. Most of the previous coastal upwelling work has been focused on the mechanism of upwelling processes on a large scale and caused by winds blowing parallel to the coast and Ekman transport. Upwelling on small local scales such as the one shown in Figure 1 has not been extensively studied. However, on a more local and smaller scale, not associated with Coriolis force or Ekman transport, winds blowing offshore can also push water mechanically away from land to produce upper level divergence and upwelling. But it is not clear if the recurring upwelling in Figure 1 can be attributed to the along-coast winds or the offshore winds or the local bathymetry, or a combination of several factors. We will look into the possible mechanisms.


Journal of Climatology and Weather Forecasting | 2016

Great Lakes Water Levels: Decomposing Time Series for Attribution

Leonard J. Pietrafesa; Shaowu Bao; Norden E. Huang; Paul T. Gayes; Tingzhuang Yan; Michael Slattery

Great Lakes water levels have been trending downwards throughout the 20th and into the 21st Centuries. Potential causes are numerous. There have been dredging and water diversion projects over the last 110 years, increasing demand for fresh water consumption from a rising population, and considerable variations in environmental factors (rainfall, snowfall, air temperature and wind), all causal in nature. A thorough assessment of United States federal agency and laboratory data archives of time series of winds, air temperatures, rainfall and snowfall, and water level data, reveals that falling lake levels can be linked to rising air temperatures. Non-uniform, post-glacial, isostatic adjustments of the entire Great Lakes region has further complicated the system as land mass tilting causes localized uplift or subsidence that has also altered relative water levels. A mathematical decomposition of the various data sets and accessory calculations strongly indicate regional atmospheric temperature increases over the entire 20th century and the early 21st century resulting in increased evaporation, is the dominant driving factor in the continued downward trend of water levels in the Great Lakes. Moreover, a high degree of correlation was discovered in comparing water level in the Great Lakes with the comparable temporal variability and record length trends evident both the Global (Land and Ocean) Surface Temperature Anomaly time series and the Atlantic Multi-Decadal Oscillation. It is of note that there have been several water level events since 2013 from which the long term losses of fresh water have undergone a change and the lakes have gained fresh water. This received a great deal of attention in both the public press and a scientific newsletter and shows that there is a danger in only dealing with a small portion, 2 years, of a 120 year climate record.


Advances in Adaptive Data Analysis | 2015

On Sea Level Variability and Trends in United States Coastal Waters and Relationships with Climate Factors

Leonard J. Pietrafesa; Shaowu Bao; Tingzhuang Yan; Michael Slattery; Paul T. Gayes

Significant portions of the United States (U.S.) property, commerce and ecosystem assets are located at or near the coast, making them vulnerable to sea level variability and change, especially relative rises. Although global mean sea level (MSL) and sea level rise (SLR) are fundamental considerations, regional mean sea level (RSL) variability along the boundaries of U.S. along the two ocean basins are critical, particularly if the amplitudes of seasonal to annual to inter-annual variability is high. Of interest is that the conventional wisdom of the U.S. agencies, the National Aeronautics and Space Administration (NASA) and the National Oceanic and Atmospheric Administration (NOAA) which both contend that the sources of sea level rise are related principally to heat absorption and release by the ocean(s) to the atmosphere and vice versa, and by Polar glacier melting and freshwater input into the ocean(s). While these phenomena are of great importance to SLR and sea level variability (SLV), we assess a suite of climate factors and the Gulf Stream, for evidence of correlations and thus possible influences; though causality is beyond the scope of this study. In this study, climate factors related to oceanic and atmospheric heat purveyors and reservoirs are analyzed and assessed for possible correlations with sea level variability and overall trends on actionable scales (localized as opposed to global scale). The results confirm that oceanic and atmospheric temperature variability and the disposition of heat accumulation or the lack thereof, are important players in sea level variability and rise, but also that the Atlantic Multi-Decadal Oscillation, the El Nino-Southern Oscillation, the Pacific Decadal Oscillation, the Arctic Oscillation, the Quasi-Biennial Oscillation, the North Atlantic Oscillation, Solar Irradiance, the Western Boundary Current-Gulf Stream, and other climate factors, can have strong correlative and perhaps even causal, modulating effects on the monthly to seasonal to annual to inter-annual to decadal to multi-decadal sea level variability at the community level.


Advances in Adaptive Data Analysis | 2011

AN EMPIRICAL STUDY OF TROPICAL CYCLONE ACTIVITY IN THE ATLANTIC AND PACIFIC OCEANS: 1851–2005

Shaowu Bao; Leonard J. Pietrafesa; Norden E. Huang; Zhaohua Wu; David A. Dickey; Paul T. Gayes; Tingzhuang Yan

The trends and intrinsic frequencies in the time series of the number of Tropical Cyclones (TCs), hurricanes and typhoons, and Categories 4 and 5 hurricanes and typhoons in the Atlantic and Pacific Ocean domains, and the yearly integral of hurricane wind energy, represented by the Power Density Index (PDI), in the Atlantic and Eastern North Pacific Ocean domains are studied. The results show that the Empirical Modal Decomposition (EMD) method [Huang et al. (1998)] successfully reveals that there are intrinsic modes of variations that are controlled by climate systems such as the Quasi-Biennial Oscillation (QBO), the El Nino Southern Oscillation (ENSO), and the Atlantic and Pacific Multi-Decadal Oscillations (AMO and PDO), along with the Meridional Overturning Circulation (MOC). It also reveals some oscillation modes whose controlling factors are not yet identified. In both the Atlantic and Pacific Ocean domains, the frequencies of TCs, hurricane/typhoon-strength TCs and the strongest (Saffir-Simpson Categories 4 and 5) TCs have slowly rising trends. In the Atlantic Ocean, our study indicates that since the mid-1970s, the observed rise in the number of the strongest (Cats. 4 and 5) TCs as discussed previously by Webster et al. [2005] and the rise in the measure of destructiveness, the Power Density Index (PDI), developed by Emanuel [2005], were not the cause of rising trends, but instead, they are the result of the combination of positive phases of several intrinsic frequency modes. In the Pacific Ocean, the rising trends have larger amplitudes than those in the Atlantic Ocean, but the higher frequency modes appear to play a more important role in deciding the year-to-year Pacific TC, hurricane/typhoon and Cats. 4 and 5 TC activity levels.


Archive | 2017

Tropical Cyclone Eye Morphology and Extratropical-Cyclone-Forced Mountain Lee Waves on SAR Imagery

Qing Xu; Xiaofeng Li; Shaowu Bao; Guosheng Zhang

This chapter introduces an objective method for determining the center of the tropical cyclone (TC) from spaceborne synthetic aperture radar (SAR) data based on the structures of the well-defined TC eyes in the SAR images. A series of Radarsat-1 SAR images are used, which capture the TCs over the world ocean basins during the years from 2001 to 2007. Also, a case study of the atmospheric gravity waves over the Kuril Islands observed in a Sentinel-1A SAR image during the passage of an extratropical cyclone will be presented together with the use of the state-of-the-art atmospheric numerical model. The objective is to obtain a more complete understanding of the generation mechanism and the dynamics governing the gravity waves.

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Leonard J. Pietrafesa

North Carolina State University

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Paul T. Gayes

Coastal Carolina University

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Tingzhuang Yan

Coastal Carolina University

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David A. Dickey

North Carolina State University

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Xiaofeng Li

National Oceanic and Atmospheric Administration

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Huiqing Liu

North Carolina State University

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Mansur Ali Jisan

Coastal Carolina University

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Dongliang Shen

Shanghai Ocean University

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Norden E. Huang

National Central University

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