Marshall Shepherd

Impacts of land use/land cover change on climate and future research priorities.

Several recommendations have been proposed for detecting land use and land cover change (LULCC) on the environment from, observed climatic records and to modeling to improve its understanding and its impacts on climate. Researchers need to detect LULCCs accurately at appropriate scales within a specified time period to better understand their impacts on climate and provide improved estimates of future climate. The US Climate Reference Network (USCRN) can be helpful in monitoring impacts of LULCC on near-surface atmospheric conditions, including temperature. The USCRN measures temperature, precipitation, solar radiation, and ground or skin temperature. It is recommended that the National Climatic Data Center (NCDC) and other climate monitoring agencies develop plans and seek funds to address any monitoring biases that are identified and for which detailed analyses have not been completed.

Urban Modification of Thunderstorms: An Observational Storm Climatology and Model Case Study for the Indianapolis Urban Region*

AbstractA radar-based climatology of 91 unique summertime (May 2000–August 2009) thunderstorm cases was examined over the Indianapolis, Indiana, urban area. The study hypothesis is that urban regions alter the intensity and composition/structure of approaching thunderstorms because of land surface heterogeneity. Storm characteristics were studied over the Indianapolis region and four peripheral rural counties approximately 120 km away from the urban center. Using radar imagery, the time of event, changes in storm structure (splitting, initiation, intensification, and dissipation), synoptic setting, orientation, and motion were studied. It was found that more than 60% of storms changed structure over the Indianapolis area as compared with only 25% over the rural regions. Furthermore, daytime convection was most likely to be affected, with 71% of storms changing structure as compared with only 42% at night. Analysis of radar imagery indicated that storms split closer to the upwind urban region and merge aga...

Thunderstorm associated asthma in Atlanta, Georgia.

Associations between thunderstorm activity and asthma morbidity have been reported in numerous locations around the world.1 The most prominent hypotheses explaining the associations are that pollen grains rupture by osmotic shock in rainwater, releasing allergens, and that gusty winds from thunderstorm downdrafts spread particles and/or aeroallergens, which may ultimately increase the risk of asthma attacks. A full understanding of “thunderstorm asthma” is crucial, especially with projections of increases in heavy rainfall, thunderstorm events and aeroallergen concentrations as the climate system warms.2 3 Many existing studies of this phenomenon have been limited in power and scope.1 Our study seeks to conduct the most extensive investigation of thunderstorm occurrence and asthma morbidity to date in a region, the Southeast US, that has not previously been examined but where thunderstorms …

Assessing the Performance of a Vulnerability Index during Oppressive Heat across Georgia, United States

Extreme heat is the leading weather-related killer in the United States. Vulnerability to extreme heat has previously been identified and mapped in urban areas to improve heat morbidity and mortality prevention efforts.However,onlylimitedworkhasexaminedvulnerabilityoutsideofurbanlocations. Thisstudyseeksto broaden the geographic context of earlier work and compute heat vulnerability across the state of Georgia, which offers diverse landscapes and populations with varying sociodemographic characteristics. Here, a modified heat vulnerability index (HVI) developed by Reid et al. is used to characterize vulnerability by county. About half of counties with the greatest heat vulnerability index scores contain the larger cities in the state (i.e., Athens, Atlanta, Augusta, Columbus, Macon, and Savannah), while the other half of highvulnerability counties are located in more rural counties clustered in southwestern and east-central Georgia. Thesourceofvulnerabilityvariedbetweenthemoreurbanandruralhigh-vulnerabilitycounties,withpoverty and population of nonwhite residents driving vulnerability in the more urban counties and social isolation/ populationofelderly/poor healththedominantfactorinthemoreruralcounties.Additionally,theeffectiveness ofthe HVIinidentifyingvulnerablepopulations was investigated byexaminingtheeffectofmodificationofthe vulnerability index score with mortality during extreme heat. Except for the least vulnerable categories, the relative risk of mortality increases with increasing vulnerability. For the highest-vulnerability counties, oppressively hot days lead to a 7.7% increase in mortality.

Urbanization Impacts on the Summer Heavy Rainfall Climatology over the Eastern United States

AbstractThe relationship between rainfall characteristics and urbanization over the eastern United States was examined by analyzing four datasets: daily rainfall in 4593 surface stations over the last 50 years (1958–2008), a high-resolution gridded rainfall product, reanalysis wind data, and a proxy for urban land use (gridded human population data). Results indicate that summer monthly rainfall amounts show an increasing trend in urbanized regions. The frequency of heavy rainfall events has a potential positive bias toward urbanized regions. Most notably, consistent with case studies for individual cities, the climatology of rainfall amounts downwind of urban–rural boundaries shows a significant increasing trend. Analysis of heavy (90th percentile) and extreme (99.5th percentile) rainfall events indicated decreasing trends of heavy rainfall events and a possible increasing trend for extreme rainfall event frequency over urban areas. Results indicate that the urbanization impact was more pronounced in the...

A seasonal-scale climatological analysis correlating spring tornadic activity with antecedent fall–winter drought in the southeastern United States

Using rain gauge and satellite-based rainfall climatologies and the NOAA Storm Prediction Center tornado database (1952–2007), this study found a statistically significant tendency for fall–winter drought conditions to be correlated with below-normal tornado days the following spring in north Georgia (i.e. 93% of the years) and other regions of the Southeast. Non-drought years had nearly twice as many tornado days in the study area as drought years and were also five to six times more likely to have multiple tornado days. Individual tornadic events are largely a function of the convective-mesoscale thermodynamic and dynamic environments, thus the study does not attempt to overstate predictability. Yet, the results may provide seasonal guidance in an analogous manner to the well known Sahelian rainfall and Cape Verde hurricane activity relationships.

Urban Induced Rainfall Modifications on Urban Hydrologic Response

Potential effects of urban areas on rainfall patterns have been increasingly studied, debated and recorded in the archived literature since 1921, when Horton o…

The Paris COP21 Climate Conference: What Does It Mean for the Southeast?

• Limit the increase of global average temperature below 2 degrees C (3.6 degrees F), but with a specific attempt to remain below 1.5 degrees C, a threshold that has been shown to be the point beyond which highly vulnerable populations can adapt, • Preserve forested landscapes to offset carbon emissions and increase conservation and global sustainability goals, • Encourage climate financing to help all nations transition from fossil-fuel dominant economies to more renewable energy-dominant power systems, • Establish a rigorous and transparent system for accounting for the Parties’ carbon reductions, • Recognize that certain countries are more vulnerable to climate change than others and that efforts must be made to avert, minimize, or address “loss and damage,” • Mandate increasingly aggressive carbon reduction targets every 5-year.2

Modeling Urban Effects on the Precipitation Component of the Water Cycle

Precipitation is an important component of the global water cycle and a proxy for changing climate. Proper understanding and quantification of spatio-temporal precipitation variability is critical for a range of meteorological, hydrological, and climate processes. Past and current literature has presented theories and observational studies on how urbanization affects precipitation. Assessment of the urban environment’s (land use, aerosols, thermal properties) impact on precipitation will be increasingly important in ongoing climate diagnostics and prediction, global water and energy cycle (GWEC) analysis and modeling, weather forecasting, freshwater resource management, urban planning-design, and land-atmosphere-ocean interface processes. This chapter presents a review of findings and methods related to “urban rainfall effect” studies with an emphasis on numerical modeling strategies. Numerical modeling of atmosphere-land interactions enables controlled experimentation to address fundamental research questions.

Inland Tropical Cyclones and the “Brown Ocean” Concept

In several regions of the world, tropical cyclones have been known to maintain or increase strength after landfall without transitioning to extratropical systems. It is hypothesized that these inland areas help sustain tropical cyclones when there has been plentiful rainfall, leading to unusually wet soil and strong latent heat release. Additionally, given the symmetric structure of warm-core cyclones, the atmosphere should tend toward barotropic conditions that mimic an ocean environment. Observational and modeling studies support this “brown ocean” concept, providing a global climatology of inland tropical cyclones, pinpointing regions that are more favorable for re-intensification, and analyzing individual cyclones to better understand the associated land-atmosphere feedbacks.