Current Search: Department of Geography (x)
Search results
(1 - 9 of 9)
- Title
- Bayesian Updating of Track-Forecast Uncertainty for Tropical Cyclones.
- Creator
- Kang, Nam-Young, Lim, Myeong-Soon, Elsner, James B., Shin, Dong-Hyun
- Abstract/Description
-
The accuracy of track forecasts for tropical cyclones (TCs) is well studied, but less attention has been paid to the representation of track-forecast uncertainty. Here, Bayesian updating is employed on the radius of the 70% probability circle using 72-h operational forecasts with comparisons made to the classical approach based on the empirical cumulative density (ECD). Despite an intuitive and efficient way of treating track errors, the ECD approach is statistically less informative than...
Show moreThe accuracy of track forecasts for tropical cyclones (TCs) is well studied, but less attention has been paid to the representation of track-forecast uncertainty. Here, Bayesian updating is employed on the radius of the 70% probability circle using 72-h operational forecasts with comparisons made to the classical approach based on the empirical cumulative density (ECD). Despite an intuitive and efficient way of treating track errors, the ECD approach is statistically less informative than Bayesian updating. Built on a solid statistical foundation, Bayesian updating is shown to be a useful technique that can serve as a substitute for the classical approach in representing operational TC track-forecast uncertainty.
Show less - Date Issued
- 2016-04
- Identifier
- FSU_libsubv1_wos_000376216300016, 10.1175/WAF-D-15-0140.1
- Format
- Citation
- Title
- Climate Mechanism for Stronger Typhoons in a Warmer World.
- Creator
- Kang, Nam-Young, Elsner, James B.
- Abstract/Description
-
Violent typhoons continue to have catastrophic impacts on economies and welfare, but how they are responding to global warming has yet to be fully understood. Here, an empirical framework is used to explain physically why observations support a tight connection between increasing ocean warmth and the increasing intensity of supertyphoons in the western North Pacific. It is shown that the energy needed for deep convection is on the rise with greater heat and moisture in the lower tropical...
Show moreViolent typhoons continue to have catastrophic impacts on economies and welfare, but how they are responding to global warming has yet to be fully understood. Here, an empirical framework is used to explain physically why observations support a tight connection between increasing ocean warmth and the increasing intensity of supertyphoons in the western North Pacific. It is shown that the energy needed for deep convection is on the rise with greater heat and moisture in the lower tropical troposphere but that this energy remains untapped when air pressure is high. Accordingly, tropical cyclone formation is becoming less common, but those that do form are likely to reach extreme intensities from the discharge of stored energy. These thermodynamic changes to the environment most significantly influence the upper portion of extreme typhoon intensities, indicating that supertyphoons are likely to be stronger at the expense of overall tropical cyclone occurrences in the western North Pacific.
Show less - Date Issued
- 2016-02
- Identifier
- FSU_libsubv1_wos_000369285500001, 10.1175/JCLI-D-15-0585.1
- Format
- Citation
- Title
- Clouds and temperature drive dynamic changes in tropical flower production.
- Creator
- Pau, Stephanie, Wolkovich, Elizabeth, Cook, Benjamin, Nytch, Christopher J., Regetz, James, Zimmerman, Jess, Wright, S.
- Abstract/Description
-
Tropical forests are incredibly dynamic, showing rapid and longer-term changes in growth, mortality and net primary productivity. Tropical species may be highly sensitive to temperature increases associated with climate change because of their narrow thermal tolerances. However, at the ecosystem scale the competing effects of temperature, light and precipitation on tropical forest productivity have been difficult to assess. Here we quantify cloudiness over the past several decades to...
Show moreTropical forests are incredibly dynamic, showing rapid and longer-term changes in growth, mortality and net primary productivity. Tropical species may be highly sensitive to temperature increases associated with climate change because of their narrow thermal tolerances. However, at the ecosystem scale the competing effects of temperature, light and precipitation on tropical forest productivity have been difficult to assess. Here we quantify cloudiness over the past several decades to investigate how clouds, together with temperature and precipitation, affect flower production in two contrasting tropical forests. Our results show that temperature, rather than clouds, is critically important to tropical forest flower production. Warmer temperatures increased flower production over seasonal, interannual and longer timescales, contrary to recent evidence that some tropical forests are already near their temperature threshold. Clouds were primarily important seasonally, and limited production in a seasonally dry forest but enhanced production in an ever-wet forest. A long-term increase in flower production at the seasonally dry forest is not driven by clouds and instead may be tied to increasing temperatures. These relationships show that tropical forest productivity, which is not widely thought to be controlled by temperature, is indeed sensitive to small temperature changes (1–4°C) across multiple timescales.
Show less - Date Issued
- 2013
- Identifier
- FSU_migr_geo_faculty_publications-0001, 10.1038/nclimate1934
- Format
- Set of related objects
- Title
- Daily Tornado Frequency Distributions in the United States.
- Creator
- Elsner, James, Widen, Holly, Chavas, Daniel, Jagger, Thomas
- Abstract/Description
-
The authors examine daily tornado counts in the United States over the period 1994–2012 and find strong evidence for a power-law relationship in the distribution frequency. The scaling exponent is estimated at 1.64 (0.019 s.e.) giving a per tornado-day probability of 0.014% (return period of 71 years) that a tornado day produces 145 tornadoes as was observed on 27 April 2011. They also find that the total number of tornadoes by damage category on days with at least one violent tornado follows...
Show moreThe authors examine daily tornado counts in the United States over the period 1994–2012 and find strong evidence for a power-law relationship in the distribution frequency. The scaling exponent is estimated at 1.64 (0.019 s.e.) giving a per tornado-day probability of 0.014% (return period of 71 years) that a tornado day produces 145 tornadoes as was observed on 27 April 2011. They also find that the total number of tornadoes by damage category on days with at least one violent tornado follows an exponential rule. On average, the daily number of tornadoes in the next lowest damage category is approximately twice the number in the current category. These findings are important and timely for tornado hazard models and for seasonal and sub-seasonal forecasts of tornado activity.
Show less - Date Issued
- 2014-02-27
- Identifier
- FSU_libsubv1_scholarship_submission_1475085241, 10.1088/1748-9326/9/2/024018
- Format
- Citation
- Title
- Quantifying the sensitivity of maximum, limiting, and potential tropical cyclone intensity to SST: Observations versus the FSU/COAPS global climate model.
- Creator
- Strazzo, Sarah, Elsner, James B., Larow, Tim
- Abstract/Description
-
Previous research quantified the sensitivity of limiting intensity to SST for observed tropical cyclones (TCs) and for TCs generated by two global climate models (GCMs). On average, a 1° C increase in sea surface temperature (SST) is associated with a 7.9 m s−1 increase in the statistical upper limit of observed intensity. Conversely, a 1°C increase in SST does not significantly affect the limiting intensity of GCM-generated TCs. The study presented here builds on previous research in two...
Show morePrevious research quantified the sensitivity of limiting intensity to SST for observed tropical cyclones (TCs) and for TCs generated by two global climate models (GCMs). On average, a 1° C increase in sea surface temperature (SST) is associated with a 7.9 m s−1 increase in the statistical upper limit of observed intensity. Conversely, a 1°C increase in SST does not significantly affect the limiting intensity of GCM-generated TCs. The study presented here builds on previous research in two ways: (1) A comparison is made between the statistically defined limiting intensity and the physically defined potential intensity, and (2) a test is performed on the ability of a ∼0.94° resolution GCM to reproduce the observed statistical relationship between potential intensity and SST. Data from NASA's Modern Era Reanalysis are used to approximate the observed sensitivity of potential intensity to SST for the 1982-2008 time period. Results indicate that the sensitivity of potential intensity to SST is not statistically different from the sensitivity of observed maximum or limiting intensity to SST. This result links the statistically defined sensitivity to the physically based theory of hurricanes. Potential intensity is also estimated from the FSU/COAPS GCM. Although the FSU/COAPS model does not capture the observed sensitivity of TC maximum or limiting intensity to SST, the model reproduces the observed sensitivity of potential intensity to SST. The model generates suitable atmospheric conditions for the development of strong TCs, however strong TCs do not develop, possibly as a result of insufficient resolution. [ABSTRACT FROM AUTHOR]
Show less - Date Issued
- 2015-04-23
- Identifier
- FSU_libsubv1_scholarship_submission_1474986340, 10.1002/2015MS000432
- Format
- Citation
- Title
- The Relationship between Elevation Roughness and Tornado Activity: A Spatial Statistical Model Fit to Data from the Central Great Plains.
- Creator
- Elsner, James B., Fricker, Tyler, Widen, Holly M., Castillo, Carla M., Humphreys, John, Jung, Jihoon, Rahman, Shoumik, Richard, Amanda, Jagger, Thomas H., Bhatrasataponkul, Tachanat, Gredzens, Christian, Dixon, P. Grady
- Abstract/Description
-
The statistical relationship between elevation roughness and tornado activity is quantified using a spatial model that controls for the effect of population on the availability of reports. Across a large portion of the central Great Plains the model shows that areas with uniform elevation tend to have more tornadoes on average than areas with variable elevation. The effect amounts to a 2.3% [(1.6%, 3.0%) = 95% credible interval] increase in the rate of a tornado occurrence per meter of...
Show moreThe statistical relationship between elevation roughness and tornado activity is quantified using a spatial model that controls for the effect of population on the availability of reports. Across a large portion of the central Great Plains the model shows that areas with uniform elevation tend to have more tornadoes on average than areas with variable elevation. The effect amounts to a 2.3% [(1.6%, 3.0%) = 95% credible interval] increase in the rate of a tornado occurrence per meter of decrease in elevation roughness, defined as the highest minus the lowest elevation locally. The effect remains unchanged if the model is fit to the data starting with the year 1995. The effect strengthens for the set of intense tornadoes and is stronger using an alternative definition of roughness. The elevation-roughness effect appears to be strongest over Kansas, but it is statistically significant over a broad domain that extends from Texas to South Dakota. The research is important for developing a local climatological description of tornado occurrence rates across the tornado-prone region of the Great Plains.
Show less - Date Issued
- 2016-04
- Identifier
- FSU_libsubv1_wos_000372839700002, 10.1175/JAMC-D-15-0225.1
- Format
- Citation
- Title
- Spatial Variation In The Quality Of American Community Survey Estimates.
- Creator
- Folch, David C., Arribas-Bel, Daniel, Koschinsky, Julia, Spielman, Seth E.
- Abstract/Description
-
Social science research, public and private sector decisions, and allocations of federal resources often rely on data from the American Community Survey (ACS). However, this critical data source has high uncertainty in some of its most frequently used estimates. Using 2006-2010 ACS median household income estimates at the census tract scale as a test case, we explore spatial and nonspatial patterns in ACS estimate quality. We find that spatial patterns of uncertainty in the northern United...
Show moreSocial science research, public and private sector decisions, and allocations of federal resources often rely on data from the American Community Survey (ACS). However, this critical data source has high uncertainty in some of its most frequently used estimates. Using 2006-2010 ACS median household income estimates at the census tract scale as a test case, we explore spatial and nonspatial patterns in ACS estimate quality. We find that spatial patterns of uncertainty in the northern United States differ from those in the southern United States, and they are also different in suburbs than in urban cores. In both cases, uncertainty is lower in the former than the latter. In addition, uncertainty is higher in areas with lower incomes. We use a series of multivariate spatial regression models to describe the patterns of association between uncertainty in estimates and economic, demographic, and geographic factors, controlling for the number of responses. We find that these demographic and geographic patterns in estimate quality persist even after we account for the number of responses. Our results indicate that data quality varies across places, making cross-sectional analysis both within and across regions less reliable. Finally, we present advice for data users and potential solutions to the challenges identified.
Show less - Date Issued
- 2016-10
- Identifier
- FSU_libsubv1_wos_000385144600012, 10.1007/s13524-016-0499-1
- Format
- Citation
- Title
- The Relationship between Elevation Roughness and Tornado Activity.
- Creator
- Elsner, James B., Fricker, Tyler, Widen, Holly M., Castillo, Carla M., Humphreys, John, Jung, Jihoon, Rahman, Shoumik, Richard, Amanda, Jagger, Thomas H., Bhatrasataponkul, Tachanat, Gredzens, Christian, Dixon, P. Grady
- Abstract/Description
-
The statistical relationship between elevation roughness and tornado activity is quantified using a spatial model that controls for the effect of population on the availability of reports. Across a large portion of the central Great Plains the model shows that areas with uniform elevation tend to have more tornadoes on average than areas with variable elevation. The effect amounts to a 2.3% [(1.6%, 3.0%) = 95% credible interval] increase in the rate of a tornado occurrence per meter of...
Show moreThe statistical relationship between elevation roughness and tornado activity is quantified using a spatial model that controls for the effect of population on the availability of reports. Across a large portion of the central Great Plains the model shows that areas with uniform elevation tend to have more tornadoes on average than areas with variable elevation. The effect amounts to a 2.3% [(1.6%, 3.0%) = 95% credible interval] increase in the rate of a tornado occurrence per meter of decrease in elevation roughness, defined as the highest minus the lowest elevation locally. The effect remains unchanged if the model is fit to the data starting with the year 1995. The effect strengthens for the set of intense tornadoes and is stronger using an alternative definition of roughness. The elevation-roughness effect appears to be strongest over Kansas, but it is statistically significant over a broad domain that extends from Texas to South Dakota. The research is important for developing a local climatological description of tornado occurrence rates across the tornado-prone region of the Great Plains.
Show less - Date Issued
- 2016-04
- Identifier
- FSU_libsubv1_wos_000372839700002, 10.1175/JAMC-D-15-0225.1
- Format
- Citation
- Title
- Tornado Intensity Estimated from Damage Path Dimensions.
- Creator
- Elsner, James, Jagger, Thomas
- Abstract/Description
-
The Newcastle/Moore and El Reno tornadoes of May 2013 are recent reminders of the destructive power of tornadoes. A direct estimate of a tornado's power is difficult and dangerous to get. An indirect estimate on a categorical scale is available from a post-storm survery of the damage. Wind speed bounds are attached to the scale, but the scale is not adequate for analyzing trends in tornado intensity separate from trends in tornado frequency. Here tornado intensity on a continuum is estimated...
Show moreThe Newcastle/Moore and El Reno tornadoes of May 2013 are recent reminders of the destructive power of tornadoes. A direct estimate of a tornado's power is difficult and dangerous to get. An indirect estimate on a categorical scale is available from a post-storm survery of the damage. Wind speed bounds are attached to the scale, but the scale is not adequate for analyzing trends in tornado intensity separate from trends in tornado frequency. Here tornado intensity on a continuum is estimated from damage path length and width, which are measured on continuous scales and correlated to the EF rating. The wind speeds on the EF scale are treated as interval censored data and regressed onto the path dimensions and fatalities. The regression model indicates a 25% increase in expected intensity over a threshold intensity of 29 m s−1 for a 100 km increase in path length and a 17% increase in expected intensity for a one km increase in path width. The model shows a 43% increase in the expected intensity when fatalities are observed controlling for path dimensions. The estimated wind speeds correlate at a level of .77 (.34, .93) [95% confidence interval] with a small sample of wind speeds estimated independently from a doppler radar calibration. The estimated wind speeds allow analyses to be done on the tornado database that are not possible with the categorical scale. The modeled intensities can be used in climatology and in environmental and engineering applications. Research is needed to understand the upward trends in path length and width.
Show less - Date Issued
- 2014-09-17
- Identifier
- FSU_libsubv1_scholarship_submission_1475155297, 10.1371/journal.pone.0107571
- Format
- Citation
