Paula Hennon - Profile on Academia.edu (original) (raw)

Papers by Paula Hennon

Cyclone Center: Insights on Historical Tropical Cyclones from Citizen Volunteers

1A.2 Investigating Patterns and Changes in Global Tropical Cyclone Storm Frequency and Intensity

Bulletin of the American Meteorological Society, 2015

The global tropical cyclone (TC) intensity record, even in modern times, is uncertain because the... more The global tropical cyclone (TC) intensity record, even in modern times, is uncertain because the vast majority of storms are only observed remotely. Forecasters determine the maximum wind speed using a patchwork of sporadic observations and remotely sensed data. A popular tool that aids forecasters is the Dvorak technique—a procedural system that estimates the maximum wind based on cloud features in IR and/or visible satellite imagery. Inherently, the application of the Dvorak procedure is open to subjectivity. Heterogeneities are also introduced into the historical record with the evolution of operational procedures, personnel, and observing platforms. These uncertainties impede our ability to identify the relationship between tropical cyclone intensities and, for example, recent climate change. A global reanalysis of TC intensity using experts is difficult because of the large number of storms. We will show that it is possible to effectively reanalyze the global record using crow...

Coastal Climate

SpringerReference

Historical definitions of what determines whether one lives in a coastal area or not have varied ... more Historical definitions of what determines whether one lives in a coastal area or not have varied over time. According to Culliton (1998), a “coastal county” is defined as a county with at least 15% of its total land area located within a nation’s coastal watershed. This emphasizes the land areas within which water flows into the ocean or Great Lakes, but may be better suited for ecosystems or water quality research (Crowell et al. 2007). Some Federal Emergency Management Agency (FEMA) documents suggest that “coastal” includes shoreline-adjacent coastal counties, and perhaps even counties impacted by flooding from coastal storms. An accurate definition of “coastal” is critical in this regard since FEMA uses such definitions to revise and modernize their Flood Insurance Rate Maps (Crowell et al. 2007). A recent map published by the National Oceanic and Atmospheric Administration’s (NOAA) Coastal Services Center for the Coastal Change Analysis Program shows that the “coastal” boundary covers the entire state of New York and Michigan, while nearly all of South Carolina is considered “coastal.” The definition of “coastal” one chooses can have major implications, including a simple count of coastal population and the influence of local or state coastal policies. There is, however, one aspect of defining what is “coastal” that has often been overlooked; using atmospheric long-term climate variables to define the inland extent of the coastal zone. This definition, which incorporates temperature, precipitation, wind speed, and relative humidity, is furthermore scalable and globally applicable - even in the face of shifting shorelines. A robust definition using common climate variables should condense the large broad definition often associated with “coastal” such that completely landlocked locations would no longer be considered “coastal.” Moreover, the resulting definition, “coastal climate” or “climatology of the coast”, will help coastal resource managers make better-informed decisions on a wide range of climatologically-influenced issues. The following sections outline the methodology employed to derive some new maps of coastal boundaries in the United States. (PDF contains 3 pages)

Geophysical Research Letters, 2013

Probable maximum precipitation (PMP) is the greatest accumulation of precipitation for a given du... more Probable maximum precipitation (PMP) is the greatest accumulation of precipitation for a given duration meteorologically possible for an area. Climate change effects on PMP are analyzed, in particular, maximization of moisture and persistent upward motion, using both climate model simulations and conceptual models of relevant meteorological systems. Climate model simulations indicate a substantial future increase in mean and maximum water vapor concentrations. For the RCP8.5 scenario, the changes in maximum values for the continental United States are approximately 20%-30% by 2071-2100. The magnitudes of the maximum water vapor changes follow temperature changes with an approximate Clausius-Clapeyron relationship. Model-simulated changes in maximum vertical and horizontal winds are too small to offset water vapor changes. Thus, our conclusion is that the most scientifically sound projection is that PMP values will increase in the future due to higher levels of atmospheric moisture content and consequent higher levels of moisture transport into storms.

P1. 63 Exploring the Connection of Extreme Convective Events and Upper-Ocean Heat Content in the Tropical Cyclone

ams.confex.com

Page 1. P1.63 EXPLORING THE CONNECTION OF EXTREME CONVECTIVE EVENTS AND UPPER-OCEAN HEAT CONTENT ... more Page 1. P1.63 EXPLORING THE CONNECTION OF EXTREME CONVECTIVE EVENTS AND UPPER-OCEAN HEAT CONTENT IN THE TROPICAL CYCLONE Paula Ann Hennon * Ohio State University, Columbus, Ohio 1. INTRODUCTION ...

Ocean-atmosphere interaction effects on tropical cyclone inner-core convective bursts

29th Conference on Hurricanes and Tropical …, 2010

29th Conference on Hurricanes and Tropical Meteorology P2.26. Ocean-atmosphere interaction effect... more 29th Conference on Hurricanes and Tropical Meteorology P2.26. Ocean-atmosphere interaction effects on tropical cyclone inner-core convective bursts. Paula Ann Hennon, STG, Inc., Asheville, NC; and J. Halverson and CC Hennon. ...

The role of the ocean in convective burst initiation: implications for tropical cyclone intensification

The upper ocean significantly influences tropical cyclone structure and intensity. These effects,... more The upper ocean significantly influences tropical cyclone structure and intensity. These effects, however, are not well understood mostly due to a lack of oceanic and atmospheric boundary layer observations within the inner-core region. This study relates ocean-atmosphere energy exchange processes to mid-to-upper tropospheric latent heating using mesoscale inner-core convective burst events. A global survey of convective burst events in tropical cyclones from the year 1999--2001 was constructed. This study shows that 80% of tropical cyclones have at least one convective burst event and that convective burst events usually occur during the intensification phase of the storm life cycle. Convective bursts are usually accompanied by a moderate (5-15 kt) wind speed increase, although some have little or no wind speed change during the burst itself. However, a period of intensification often follows a convective burst event within 18 to 24 hours. To determine atmospheric and oceanic variables useful in identifying conditions typical of convective burst activity, an ensemble of discriminant analyses were performed. The first procedure tested solely atmospheric variables; the second tested the oceanic variables by themselves, and finally, a combined procedure attempted to distinguish convective burst events using both the atmospheric and oceanic variables. Four main atmospheric conditions characterize convective burst existence when compared to periods with no convective burst: (1) increased precipitable water at 200 km and 500 km, (2) increased 150 mb divergence at 600 km, (3) 2-1/2 times more convective instability in the large-scale environment, (4) 1-1/2 to 2 times more 850 mb moisture divergence at 200 km and 600 km. The main characteristic differences in ocean conditions during convective burst events are: (1) the mean climatological SST is 1.25°C greater; (2) the "hurricane heat content" is double; (3) less inner-core ocean cooling occurs. The combined analysis suggests that the moist static energy provided by the warm ocean is more influential on convective burst occurrence than simply having "enough" available atmospheric moisture. A multivariate Lagrangian time series of the inner-core SST, the inner-core-wake SST, the ahead-of-storm SST, and measures of spatial variability of these variables for 30 tropical cyclones was constructed using an objectively interpolated SST tropical cyclone coldwake climatology. (Abstract shortened by UMI.)

Bulletin of the American Meteorological Society, 2012

Large-scale climate patterns influenced temperature and weather patterns around the globe in 2011... more Large-scale climate patterns influenced temperature and weather patterns around the globe in 2011. In particular, a moderate-to-strong La Niña at the beginning of the year dissipated during boreal spring but reemerged during fall. The phenomenon contributed to historical droughts in East Africa, the southern United States, and northern Mexico, as well the wettest two-year period (2010-11) on record for Australia, particularly remarkable as this follows a decade-long dry period. Precipitation patterns in South America were also influenced by La Niña. Heavy rain in Rio de Janeiro in January triggered the country's worst floods and landslides in Brazil's history. The 2011 combined average temperature across global land and ocean surfaces was the coolest since 2008, but was also among the 15 warmest years on record and above the 1981-2010 average. The global sea surface temperature cooled by 0.1°C from 2010 to 2011, associated with cooling influences of La Niña. Global integrals of upper ocean heat content for 2011 were higher than for all prior years, demonstrating the Earth's dominant role of the oceans in the Earth's energy budget. In the upper atmosphere, tropical stratospheric temperatures were anomalously warm, while polar temperatures were anomalously cold. This led to large springtime stratospheric ozone reductions in polar latitudes in both hemispheres. Ozone concentrations in the Arctic stratosphere during March were the lowest for that period since satellite records began in 1979. An extensive, deep, and persistent ozone hole over the Antarctic in September indicates that the recovery to pre-1980 conditions is proceeding very slowly. Atmospheric carbon dioxide concentrations increased by 2.10 ppm in 2011, and exceeded 390 ppm for the first time since instrumental records began. Other greenhouse gases also continued to rise in concentration and the combined effect now represents a 30% increase in radiative forcing over a 1990 baseline. Most ozone depleting substances continued to fall. The global net ocean carbon dioxide uptake for the 2010 transition period from El Niño to La Niña, the most recent period for which analyzed data are available, was estimated to be 1.30 Pg C yr -1 , almost 12% below the 29-year long-term average. Relative to the long-term trend, global sea level dropped noticeably in mid-2010 and reached a local minimum in 2011. The drop has been linked to the La Nina conditions that prevailed throughout much of 2010-11. Global sea level increased sharply during the second half of 2011.