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The 2009 Atlanta flood was a historic event that resulted in catastrophic damage throughout the metropolitan area. The flood was the product of several hydrometeorological processes, including moist antecedent conditions, ample atmospheric moisture, and mesoscale training. Additionally, previous studies hypothesized that the urban environment of Atlanta altered the location and/or overall quantities of precipitation and runoff that ultimately produced the flood. This hypothesis was quantitatively evaluated by conducting a modeling case study that utilized the Weather Research and Forecasting Model. Two model runs were performed: 1) an urban run designed to accurately depict the flood event and 2) a nonurban simulation where the urban footprint of Atlanta was replaced with natural vegetation. Comparing the output from the two simulations revealed that interactions with the urban environment enhanced the precipitation and runoff associated with the flood. Specifically, the nonurban model underestimated the cumulative precipitation by approximately 100 mm in the area downwind of Atlanta where urban rainfall enhancement was hypothesized. This notable difference was due to the increased surface convergence observed in the urban simulation, which was likely attributable to the enhanced surface roughness and thermal properties of the urban environment. The findings expand upon previous research focused on urban rainfall effects since they demonstrate that urban interactions can influence mesoscale hydrometeorological characteristics during events with prominent synoptic-scale forcing. Finally, from an urban planning perspective, the results highlight a potential two-pronged vulnerability of urban environments to extreme rainfall, as they may enhance both the initial precipitation and subsequent runoff.

Due to the vulnerability of the Edwards Aquifer to urban development, policy measures have been implemented to protect the important water resource in South–Central Texas. This paper analyzed land use change trends across different portions of the Edwards Aquifer to better understand the degree to which protective measures influenced aquifer urbanization rates. Specifically, the National Land Cover Database was used to quantify urban development within the contributing and recharge zones of the Edwards Aquifer across Bexar, Travis, Williamson, Comal, and Hays counties for three time periods: 2001–2006, 2006–2011, and 2011–2016. Bexar County exhibited the greatest reduction in the rate of urbanization within the recharge zone although the percentage of the zone developed remained the highest. Conversely, the pace of recharge zone development in Travis and Williamson County decreased less rapidly, but the percentage of the zone urbanized was lower. Limited urban development was observed across the aquifer in Comal and Hays County during the study period. Overall, the consistent declining rate of urbanization throughout the sensitive Edwards Aquifer recharge zone suggests that the policies protecting the aquifer were largely effective, particularly given the rapid pace of urban growth throughout the region.

Atmospheric rivers (ARs) are narrow and elongated bands of anomalous water vapour transport that have been widely studied due to their notable influence on regional weather patterns, surface hydrology, and the global water cycle. Although ARs produce a relatively large proportion of the annual precipitation in the southeastern quadrant of the United States, a detailed climatological analysis of Southeastern atmospheric rivers (SE-ARs) has not been conducted. In this study, a climatology of SE-AR coastal interactions from 1979 to 2014 was constructed from a global AR data set to examine the spatiotemporal characteristics of SE-ARs as well as the importance of synoptic-scale and low-frequency modes of climate variability in modulating their frequency. The climatology revealed that SE-ARs were most prevalent during the cold season, with the majority of these wintertime coastal interactions occurring predominately in the Gulf of Mexico. The synoptic-scale and low-frequency modes of climate variability favourable for SE-AR development differed depending on the season and sub-region of the Southeast considered. More specifically, a dipole effect was discovered, as conditions conducive for SE-AR coastal interactions along the western Gulf generally inhibited SE-AR interactions with the Florida Peninsula and vice versa. Overall, a better understanding of the seasonality of SE-ARs as well as the synoptic-scale and low-frequency modes of climate variability that encourage their development could lead to improved forecasting and community awareness of the devastating AR-related flood events that occur throughout the Southeast.

The spatial configuration of cities can affect how urban environments alter local energy balances. Previous studies have reached the paradoxical conclusions that both sprawling and high-density urban development can amplify urban heat island intensities, which has prevented consensus on how best to mitigate the urban heat island effect via urban planning. To investigate this apparent dichotomy, we estimated the urban heat island intensities of the 50 most populous cities in the United States using gridded minimum temperature datasets and quantified each city's urban morphology with spatial metrics. The results indicated that the spatial contiguity of urban development, regardless of its density or degree of sprawl, was a critical factor that influenced the magnitude of the urban heat island effect. A ten percentage point increase in urban spatial contiguity was predicted to enhance the minimum temperature annual average urban heat island intensity by between 0.3 and 0.4 °C. Therefore, city contiguity should be considered when devising strategies for urban heat island mitigation, with more discontiguous development likely to ameliorate the urban heat island effect. Unraveling how urban morphology influences urban heat island intensity is paramount given the human health consequences associated with the continued growth of urban populations in the future.

Although advances have been made regarding the influence of aerosols on precipitation processes, the ability of power plant aerosol emissions to alter cloud microphysics and enhance atmospheric convection is not yet fully understood. By analyzing the relationship between proximity to coal power plants and lightning flash density in Georgia from 1992–2003, we find that lightning strike frequency is not substantially enhanced near power plants in the long-term warm season climatology. If existent, any signal was likely masked by the more dominant mechanisms of the sea breeze circulation, Sandhills-Fall Line convection, and Atlanta urban environment. Despite the lack of a definitive signal in the climatology, several cases of potential lightning amplification were identified for Plant Scherer. Therefore, power plant lightning enhancement may potentially occur in isolated events, but it is difficult to link such events conclusively to power plant aerosol emissions without a more detailed analysis of the causa...

Superstorm Sandy was an unprecedented meteorological event that devastated the Caribbean and the Northeastern Coast of the USA in October 2012. While many research efforts will focus on the atmosph...

Previous research exploring the environmental justice implications of urban flood hazards has produced contrasting results due to the different dasymetric mapping techniques used, the various spatial scales of the analyses, and the specific geographical context of the individual study cities, particularly as it relates to the presence of coastal water-based amenities. To better understand if vulnerable populations are disproportionately exposed to urban flood hazards in non-coastal cities, this study assessed the magnitude of socio-economic inequities in flood risk throughout the Charlanta megaregion. Specifically, population characteristics within the 500-year flood zone were estimated using United States Census Bureau data for race, ethnicity, and poverty by applying three dasymetric mapping techniques at four spatial scales. Risk ratios were used to statistically evaluate if vulnerable populations were overrepresented in areas at risk for flooding overall as well as for lake and non-lake regions. Although the results varied according to the scale and socio-economic variable, the most accurate dasymetric mapping approach indicated that environmental injustices were systemic, as vulnerable individuals were between 14% and 42% more likely to reside in areas at risk for flooding when analyzing the entire megaregion. At the metropolitan scale, vulnerable individuals were still significantly more likely to reside in flood zones, and the influence of lake amenities on the disparities was nuanced. A complex spatial landscape of inequities was also observed at the county and census tract levels. Overall, the notable disparities faced particularly by non-Hispanic black and Hispanic populations suggest that urban flood risk inequities in the megaregion are largely due to structural forms of discrimination and residential segregation, which have been pervasive throughout the development of Charlanta.

Air travel emissions comprise 20% of tourism's global carbon footprint. The purpose of this study was to determine whether non-stop routes to tourist destinations can mitigate air travel carbon emissions relative to routes that connect through airline hubs. Based on International Civil Aviation Organization data, we analyzed carbon emissions for both direct and connecting routes between the ten most populated metropolitan areas located in the Northeastern United States and 13 different tourist destinations located in the Sunbelt and Western regions of the US. Direct routes generally outperformed connecting routes regarding carbon emissions, although there were several exceptions. On average, non-stop routes reduced carbon emissions by roughly 100 kg/person relative to the next best connecting option.

The human population on Earth has increased by a factor of 4.6 in the last 100 years and has become more centered in urban environments. This expansion and migration pattern has resulted in stresses on the environment. Meteorological applications have helped to understand and mitigate those stresses. This chapter describes several applications that enable the population to interact with the environment in more sustainable ways. The first topic treated is urbanization itself and the types of stresses exerted by population growth and its attendant growth in urban landscapes—buildings and pavement—and how they modify airflow and create a local climate. We describe environmental impacts of these changes and implications for the future. The growing population uses increasing amounts of energy. Traditional sources of energy have taxed the environment, but the increase in renewable energy has used the atmosphere and hydrosphere as its fuel. Utilizing these variable renewable resources requires meteorological information to operate electric systems efficiently and economically while providing reliable power and minimizing environmental impacts. The growing human population also pollutes the environment. Thus, understanding and modeling the transport and dispersion of atmospheric contaminants are important steps toward regulating the pollution and mitigating impacts. This chapter describes how weather information can help to make surface transportation more safe and efficient. It is explained how these applications naturally require transdisciplinary collaboration to address these challenges caused by the expanding population.