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.
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BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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.
•Urban heat island (UHI) intensities were estimated for the fifty most populous cities in the USA using PRISM climate data.•The urban morphologies of the cities were quantified using spatial metrics and the NLCD 2006 land use/land cover dataset.•The statistical analyses suggested that highly contiguous dense and sprawling urban development both enhance the UHI effect.•City contiguity should be considered when devising strategies for UHI intensity mitigation.•More discontiguous city configurations, especially if achieved by introducing urban green spaces, will likely reduce UHIs.
There is increasing observational evidence that urban land cover can have a significant effect on precipitation variability. Atlanta, because of its rapid urbanization, has been a focus for several ...observational studies on urbanization and rainfall. Yet, there is a lack of numerical model studies in the literature to examine physical processes linked to the Atlanta “urban rainfall effect” or URE. This study employs the Weather Research and Forecast (WRF) model to simulate convective precipitation for two cases: 17 August 2002 (“an urban interaction case”) and 26th July 1996 (an urban “initiation” case). Case 1 was chosen based on analysis of radar composites and surface maps which identified it as an event likely to have some urban forcing with minimal large scale forcing; while Case 2 was based on a previous observational study indicating that the storm was initiated by urban heat island induced convergence zone.
The control (URBAN) simulations begin 3 h prior to the observed storm initiations and reveal that the model captures the convective evolution of the cases. The alternative (NOURBAN) simulations indicate that removing the city of Atlanta causes distinct differences in the temporal and spatial evolution of the explicitly resolved precipitation. However these differences point more to the likelihood of modification rather than initiation of the convective systems.
Time series of cumulative rainfall totals indicate that the explicitly resolved rainfall is initiated at the same time in both the URBAN and NOURBAN simulations. The rainfall initiation time even within sub-sections of the domain is the same for the URBAN and NOURBAN scenario. Rainfall amounts downwind of the city are higher by 10% to 13% within a strip 20–50 km east of the city, for the URBAN schemes in comparison to NOURBAN.
The urban heat island (UHI), together with summertime heat waves, foster's biophysical hazards such as heat stress, air pollution, and associated public health problems. Mitigation strategies such as ...increased vegetative cover and higher albedo surface materials have been proposed. Atlanta, Georgia, is often affected by extreme heat, and has recently been investigated to better understand its heat island and related weather modifications. The objectives of this research were to (1) characterize temporal variations in the magnitude of UHI around Metro Atlanta area, (2) identify climatological attributes of the UHI under extremely high temperature conditions during Atlanta's summer (June, July, and August) period, and (3) conduct theoretical numerical simulations to quantify the first-order effects of proposed mitigation strategies. Over the period 1984-2007, the climatological mean UHI magnitude for Atlanta-Athens and Athens-Monticello was 1.31 and 1.71°C, respectively. There were statistically significant minimum temperature trends of 0.70°C per decade at Athens and −1.79°C per decade at Monticello while Atlanta's minimum temperature remained unchanged. The largest (smallest) UHI magnitudes were in spring (summer) and may be coupled to cloud-radiative cycles. Heat waves in Atlanta occurred during 50% of the years spanning 1984-2007 and were exclusively summertime phenomena. The mean number of heat wave events in Atlanta during a given heat wave year was 1.83. On average, Atlanta heat waves lasted 14.18 days, although there was quite a bit of variability (standard deviation of 9.89). The mean maximum temperature during Atlanta's heat waves was 35.85°C. The Atlanta-Athens UHI was not statistically larger during a heat wave although the Atlanta-Monticello UHI was. Model simulations captured daytime and nocturnal UHIs under heat wave conditions. Sensitivity results suggested that a 100% increase in Atlanta's surface vegetation or a tripling of its albedo effectively reduced UHI surface temperature. However, from a mitigation and technological standpoint, there is low feasibility of tripling albedo in the foreseeable future. Increased vegetation seems to be a more likely choice for mitigating surface temperature.
Within the Charlotte, North Carolina, to Atlanta, Georgia, megaregion (Charlanta), the Atlanta metropolitan area has been shown to augment proximal cloud‐to‐ground (CG) lightning occurrence. Although ...numerous studies have documented this “urban lightning effect” (ULE) with regard to CG lightning, relatively few have investigated urban effects on distributions of total lightning (TL). Moreover, there has yet to be a study of the ULE using TL observations from the Geostationary Lightning Mapper (GLM). In an effort to fill this gap, we investigated spatial distributions of TL around the cities of Atlanta, GA, Greenville, SC, and Charlotte, NC, using GLM data collected during the warm seasons of 2018–2021. Analyses reveal augmentation of TL intensity and frequency over the major cities of Atlanta and Charlotte, with a diminished urban signal over the smaller city of Greenville. This work also demonstrated the potential efficacy of the emerging satellite‐based TL climatology in ULE studies.
Plain Language Summary
Studies using ground‐based lightning detection networks have revealed an “urban lightning effect” (ULE) around major cities. In 2016, the U.S. launched a weather satellite with a unique lightning mapping instrument. This study, possibly for the first time, demonstrated the ability to utilize space‐based observation of total lightning to detect the ULE within the Charlotte, North Carolina, to Atlanta, Georgia, urban corridor. The study also paves the way for future ULE analyses as the satellite lightning data record lengthens.
Key Points
The urban lightning effect (ULE) is detectable in Geostationary Lightning Mapper total lightning observations
The ULE is most discernible in the larger metropolitan areas of the Charlotte, NC, to Atlanta, GA, urban corridor
The emerging Geostationary Lightning Mapper data set enables a new generation of urban lightning studies as the record lengthens
ABSTRACT
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.
Flooding is routinely one of the most deadly weather-related hazards in the United States, which highlights the need for more hydrometeorological research related to forecasting these hazardous ...events. Building upon previous literature, a synergistic study analyzes hydrometeorological aspects of major urban flood events in the United States from 1977 through 2014 caused by locally heavy precipitation. Primary datasets include upper-air soundings and climatological precipitable water (PW) distributions. A major finding of this work is that major urban flood events are associated with extremely anomalous PW values, many of which exceeded the 99th percentile of the associated climatological dataset and all of which were greater than 150% of the climatological mean values. However, of the 40 cases examined in this study, only 15 had PW values that exceeded 50.4mm (2 in.), illustrating the importance of including the location-specific PW climatology in a PW analysis relevant to the potential for flash floods. Additionally, these events revealed that, despite geographic location and time of year, most had a warm cloud depth of at least 6 km, which is defined here as the layer between the lifting condensation level and the height of the −10°C level. A "composite" flood sounding was also calculated and revealed a characteristically tropical structure, despite cases related to tropical cyclones being excluded from the study.
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Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Preventive care and routine clinic visits declined sharply, limiting cancer care to patients who were symptomatic. ...during lockdown, many patients could not travel to access necessary services, ...further complicating cancer care. Cooperative Institute for Research in the Atmosphere at Colorado State and the National Oceanic and Atmospheric Administration 2017 Hurricane Maria Hurricane Maria brought major hurricane (category 3–5) winds to five small island states and tropical storm force winds to 11 more. Deluging rains produced precipitation extremes exceeding 1 m. Wind damage, torrential rains, flash floods, and widespread landslides contributed to extensive devastation and disruption of electrical power, transportation, water, and supply chains for food, medicine, and fuel, with long-lasting physical and mental health consequences for the citizens.
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