Date of Award
8-2014
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Legacy Department
Civil Engineering
Committee Chair/Advisor
Dr. Weichiang Pang
Committee Member
Dr. Scott D. Schiff
Committee Member
Dr. Sezer Atamturktur
Committee Member
Dr. Nigel B. Kaye
Abstract
Hurricane is among the most dangerous and costliest natural hazards that affect the coastal environment of the United States (U.S.) every year. Hurricane activities have been observed to change in many aspects since the last century including the changes in both intensity and annual storm frequency. The extent to which aspect of climate change contributes to the variation in hurricane activities from long-term historical statistics is still not clearly understood at this point. This study examines the impacts of two climate change effects (change in annual storm frequency and sea surface temperature) on future U.S. design wind speeds for the coastal regions and projects potential hurricane losses under different speculated future climate scenarios. To realize the goal of investigating climate change effect on hurricane activities, a baseline hurricane simulation model was first developed and was used to simulate 200,000 years of hurricanes without considering climate change effects. The landfall rates, central pressures at landfall and other relevant parameters of the simulated hurricanes were validated against historical observations. Next, the baseline hurricane simulation program was modified to include the effects of two climate change factors, namely, change in annual storm frequency and change in sea surface temperature (SST). Three annual frequency models were utilized to simulate the effect of change in annual storm frequency. The first model is a baseline model which assumes the annual storm frequency to remain stationary over time with a constant mean and a constant standard deviation. The second model was a linear moving average (LMA) mean model which assumes the mean annual storm frequency follows a linear trend. The third model was an oscillating moving average (OMA) model which has similar oscillating periods with the Atlantic multi-decadal oscillation of sea surface temperature. These three annual storms frequency models were used to simulate and project annual number of storms through the end of the century. SST is one of the key inputs that affect the storm intensity. Its changes over time are projected based on the global climate models (GCMs) under multiple future climate scenarios in the United Nations Intergovernmental Panel on Climate Change (IPCC) fifth assessment report (AR5). Four SST projections were considered in this study. Similar to the annual storm frequency model, a baseline SST model, which assumes the mean SST remains stationary over time, was employed. The other three SST models were based on the IPCC Representative Concentration Pathway (RCP) of different greenhouse gases emission scenarios and projected radiative forcing for the year 2100. The three RCPs utilized in this study are (1) a climate change mitigation scenario leading to a very low forcing level of 2.6 W/m2 (RCP2.6), (2) a medium stabilization scenario (RCP4.5) and (3) a high emission scenario (RCP8.5). Six hurricane databases considering different climate change scenarios were generated. Each climate scenario considers the effects of changes in annual storm frequency and SST. Four scenarios consider the effects of changes in storm frequency and SST jointly while the other two scenarios consider the effects of changes in SST and annual storm frequency independent of each other. Using the simulated hurricane databases, future design wind speeds under the speculated climate change scenarios were computed and compared to those in the current design code (ASCE 7-10). It is found that the design wind speeds for Occupancy Category II (700 years MRI) buildings, which were developed based on the current climate condition, may increase significantly by the end of the century under the most drastic climate change scenario (increase in storm frequency and RCP8.5). While changes in annual storm frequency and SSTs both contribute to increases in design wind speeds, it was found that with the rise in SSTs having the most influence on design wind speeds. In order to examine the influence of climate change on future hurricane activities and the associated hurricane losses in coastal environment, a hurricane simulation program was developed and the simulated hurricanes were utilized to perform loss assessments. To evaluate the financial impact of climate change, loss estimations were performed using HAZUS-MH program for four coastal cities (New Orleans, LA, Miami, FL, Charleston, SC and New York, NY). A methodology to select hazard-consistent hurricane events for loss assessment was developed and ensembles of full-track hurricanes were selected for the four case study cities. The hurricane ensemble selection procedure was developed to capture the event-to-event uncertainty. In addition to consider changes in wind hazards, changes in building resistances (with and without wind retrofits) were also considered in loss estimation study. To evaluate the effectiveness of existing wind retrofits for mitigating the effects of climate change, it was assumed either none of the residential buildings were retrofitted or 100% of the residential buildings were retrofitted with all wind retrofits available in the HAZUS-MH program. From the loss estimation study, it was determined that implementing wind retrofits is a win-win strategy regardless of whether the future hurricane wind hazard is rising or is stationary. Retrofitted buildings not only reduce the losses due to climate change but also the variability in the losses.
Recommended Citation
Liu, Fangqian, "Projections of Future US Design Wind Speeds Due to Climate Change for Estimating Hurricane Losses" (2014). All Dissertations. 1305.
https://open.clemson.edu/all_dissertations/1305