scholarly journals Aerosol optical properties in the southeastern United States in summer – Part 1: Hygroscopic growth

2015 ◽  
Vol 15 (18) ◽  
pp. 25695-25738 ◽  
Author(s):  
C. A. Brock ◽  
N. L. Wagner ◽  
B. E. Anderson ◽  
A. R. Attwood ◽  
A. Beyersdorf ◽  
...  
Keyword(s):  
United States ◽  
Layer Structure ◽  
Southeastern United States ◽  
Field Studies ◽  
Hygroscopic Growth ◽  
Particle Volume ◽  
Aerosol Composition ◽  
Optical Extinction ◽  
Airborne Measurements ◽  
Southeastern Us

Abstract. Aircraft observations of meteorological, trace gas, and aerosol properties were made during May–September 2013 in the southeastern United States (US) under fair-weather, afternoon conditions with well-defined planetary boundary layer structure. Optical extinction at 532 nm was directly measured at three relative humidities and compared with extinction calculated from measurements of aerosol composition and size distribution using the κ-Köhler approximation for hygroscopic growth. Using this approach, the hygroscopicity parameter κ for the organic fraction of the aerosol must have been < 0.10 to be consistent with 75 % of the observations within uncertainties. This subsaturated κ value for the organic aerosol in the southeastern US is consistent with several field studies in rural environments. We present a new parameterization of the change in aerosol extinction as a function of relative humidity that better describes the observations than does the widely used power-law (gamma, γ) parameterization. This new single-parameter κext formulation is based upon κ-Köhler and Mie theories and relies upon the well-known approximately linear relationship between particle volume (or mass) and optical extinction (Charlson et al., 1967). The fitted parameter, κext, is nonlinearly related to the chemically derived κ parameter used in κ-Köhler theory. The values of κext we determined from airborne measurements are consistent with independent observations at a nearby ground site.

scholarly journals Aerosol optical properties in the southeastern United States in summer – Part 1: Hygroscopic growth

2016 ◽  
Vol 16 (8) ◽  
pp. 4987-5007 ◽  
Author(s):  
Charles A. Brock ◽  
Nicholas L. Wagner ◽  
Bruce E. Anderson ◽  
Alexis R. Attwood ◽  
Andreas Beyersdorf ◽  
...  
Keyword(s):  
United States ◽  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Layer Structure ◽  
Southeastern United States ◽  
Organic Aerosol ◽  
Hygroscopic Growth ◽  
Aerosol Composition ◽  
Optical Extinction ◽  
Southeastern Us

Abstract. Aircraft observations of meteorological, trace gas, and aerosol properties were made during May–September 2013 in the southeastern United States (US) under fair-weather, afternoon conditions with well-defined planetary boundary layer structure. Optical extinction at 532 nm was directly measured at relative humidities (RHs) of  ∼  15,  ∼  70, and  ∼  90 % and compared with extinction calculated from measurements of aerosol composition and size distribution using the κ-Köhler approximation for hygroscopic growth. The calculated enhancement in hydrated aerosol extinction with relative humidity, f(RH), calculated by this method agreed well with the observed f(RH) at  ∼  90 % RH. The dominance of organic aerosol, which comprised 65 ± 10 % of particulate matter with aerodynamic diameter  <  1 µm in the planetary boundary layer, resulted in relatively low f(RH) values of 1.43 ± 0.67 at 70 % RH and 2.28 ± 1.05 at 90 % RH. The subsaturated κ-Köhler hygroscopicity parameter κ for the organic fraction of the aerosol must have been  <  0.10 to be consistent with 75 % of the observations within uncertainties, with a best estimate of κ  =  0.05. This subsaturated κ value for the organic aerosol in the southeastern US is broadly consistent with field studies in rural environments. A new, physically based, single-parameter representation was developed that better described f(RH) than did the widely used gamma power-law approximation.

scholarly journals Public entrepreneurs and the adoption of broad-based merit aid beyond the Southeastern United States

2013 ◽  
Vol 21 ◽  
pp. 58
Author(s):  
William Kyle Ingle ◽  
Ruth Ann Petroff
Keyword(s):  
United States ◽  
Diffusion Theory ◽  
Full Range ◽  
Southeastern United States ◽  
Merit Aid ◽  
Theoretical Frameworks ◽  
Southeastern Us ◽  
Public Colleges And Universities ◽  
Aid Programs ◽  
K 12

The concentration of broad-based merit aid adoption in the southeastern United States has been well noted in the literature. However, there are states that have adopted broad-based merit aid programs outside of the Southeast.  Guided by multiple theoretical frameworks, including innovation diffusion theory (e.g., Gray, 1973, 1994; Rogers, 2003), Roberts and King’s (1991) typology of public entrepreneurs, and Anderson’s (2003) stages of the policymaking process, this qualitative study sought to answer the following questions. First, in the absence of regional diffusion pressures, what internal determinants are reported as accounting for the diffusion of broad-based merit aid programs outside of the Southeastern US?  What types of public entrepreneurs were identified as playing key roles in establishing merit aid in states outside the southeastern US?  During which stages of the policymaking process were they active? We found that merit aid was a means of addressing an array of public problems, including low college going rates at in-state public colleges and universities, and weak K-12 accountability. Consistent factors reported as facilitating merit aid creation included a strong, vocal public advocate (governors and a university system president) and a desire to strengthen state economies and diversify workforces.  A full range of public entrepreneurs played key roles in developing merit aid in the sampled states. Political and executive entrepreneurs were in the forefront of merit aid efforts, but our data suggest that a cast of supporting public entrepreneurs were integral to the eventual adoption of broad-based merit aid in the sampled states.

scholarly journals Modelling the High Mercury Wet deposition in the Southeastern US by WRF-GC

2022 ◽  
Author(s):  
Xiaotian Xu ◽  
Xu Feng ◽  
Haipeng Lin ◽  
Peng Zhang ◽  
Shaojian Huang ◽  
...  
Keyword(s):  
United States ◽  
Wet Deposition ◽  
Deep Convection ◽  
Southeastern United States ◽  
Convective Precipitation ◽  
Mercury Deposition ◽  
Southeastern Us ◽  
Different Types ◽  
High Mercury ◽  
Simulation Results

Abstract. High mercury wet deposition in southeastern United States has been noticed for many years. Previous studies came up with a theory that it was associated with high-altitude divalent mercury scavenged by convective precipitation. Given the coarse resolution of previous models (e.g. GEOS-Chem), this theory is still not fully tested. Here we employed a newly developed WRF-GEOS-Chem (WRF-GC) model implemented with mercury simulation. We conduct extensive model benchmarking by comparing WRF-GC with different resolutions (from 50 km to 25 km) to GEOS-Chem output (4° × 5°) and data from Mercury Deposition Network (MDN) in July–September 2013. The comparison of mercury wet deposition from two models both present high mercury wet deposition in southeastern United States. We divided simulation results by heights, different types of precipitation and combination of these two variations together and find most of mercury wet deposition concentrates on higher space and caused by convective precipitation. Therefore, we conclude that it is the deep convection caused enhanced mercury wet deposition in the southeastern United States.

Financial Returns for Biomass on Short-Rotation Loblolly Pine Plantations in the Southeastern United States

2021 ◽  
Author(s):  
Andrew Trlica ◽  
Rachel L Cook ◽  
Timothy J Albaugh ◽  
Rajan Parajuli ◽  
David R Carter ◽  
...  
Keyword(s):  
United States ◽  
Loblolly Pine ◽  
Southeastern United States ◽  
Field Studies ◽  
Pine Plantations ◽  
Planting Density ◽  
Financial Returns ◽  
Short Rotation ◽  
Competition Control ◽  
Whole Tree

Abstract Rising demand for renewable energy has created a potential market for biomass from short-rotation pine plantations in the southeastern United States. Site preparation, competition control, fertilization, and enhanced seedling genotypes offer the landowner several variables for managing productivity, but their combined effects on financial returns are unclear. This study estimated returns from a hypothetical 10-year biomass harvest in loblolly pine plantation using field studies in the Coastal Plain of North Carolina and the Virginia Piedmont testing combinations of tree genotype, planting density, and silviculture. Although enhanced varietal genotypes could yield more biomass, open-pollinated seedlings at 1,236–1,853 trees ha−1 under operational silviculture had the greatest returns at both sites, with mean whole-tree internal rates of return of 8.3%–9.9% assuming stumpage equal to current pulpwood prices. At a 5% discount rate, break-even whole-tree stumpage at the two sites in the optimal treatments was $8.72–$9.92 Mg−1, and break-even yield was 175–177 Mg ha−1 (roughly 18 Mg ha−1 yr−1 productivity), although stumpage and yield floors were higher if only stem biomass was treated as salable. Dedicated short-rotation loblolly biomass plantations in the region are more likely to be financially attractive when site establishment and maintenance costs are minimized. Study Implications: Our study suggests that dedicated loblolly pine plantations in the US Southeast may be managed to generate positive financial yields for biomass over relatively short (10 year) rotation windows, even at lower stumpage value than at present for pulpwood in the region (&lt;80% current). Intensive use of costly inputs like fertilizer, vigorous chemical competition control, and elite genetics in planting stock did improve biomass yields. However, the management combinations that favored the highest financial returns emphasized the least expensive open-pollinated stock, lower-input operational silviculture, and moderate-to-high planting density.

scholarly journals Aerosol optical properties in the southeastern United States in summer – Part 2: Sensitivity of aerosol optical depth to relative humidity and aerosol parameters

2016 ◽  
Vol 16 (8) ◽  
pp. 5009-5019 ◽  
Author(s):  
Charles A. Brock ◽  
Nicholas L. Wagner ◽  
Bruce E. Anderson ◽  
Andreas Beyersdorf ◽  
Pedro Campuzano-Jost ◽  
...  
Keyword(s):  
United States ◽  
Refractive Index ◽  
Relative Humidity ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Mixed Boundary ◽  
Southeastern United States ◽  
Geometric Standard Deviation ◽  
Aerosol Mass ◽  
Southeastern Us

Abstract. Aircraft observations of meteorological, trace gas, and aerosol properties were made between May and September 2013 in the southeastern United States (US). Regionally representative aggregate vertical profiles of median and interdecile ranges of the measured parameters were constructed from 37 individual aircraft profiles made in the afternoon when a well-mixed boundary layer with typical fair-weather cumulus was present (Wagner et al., 2015). We use these 0–4 km aggregate profiles and a simple model to calculate the sensitivity of aerosol optical depth (AOD) to changes in dry aerosol mass, relative humidity, mixed-layer height, the central diameter and width of the particle size distribution, hygroscopicity, and dry and wet refractive index, while holding the other parameters constant. The calculated sensitivity is a result of both the intrinsic sensitivity and the observed range of variation in these parameters. These observationally based sensitivity studies indicate that the relationship between AOD and dry aerosol mass in these conditions in the southeastern US can be highly variable and is especially sensitive to relative humidity (RH). For example, calculated AOD ranged from 0.137 to 0.305 as the RH was varied between the 10th and 90th percentile profiles with dry aerosol mass held constant. Calculated AOD was somewhat less sensitive to aerosol hygroscopicity, mean size, and geometric standard deviation, σg. However, some chemistry–climate models prescribe values of σg substantially larger than we or others observe, leading to potential high biases in model-calculated AOD of  ∼  25 %. Finally, AOD was least sensitive to observed variations in dry and wet aerosol refractive index and to changes in the height of the well-mixed surface layer. We expect these findings to be applicable to other moderately polluted and background continental air masses in which an accumulation mode between 0.1–0.5 µm diameter dominates aerosol extinction.

scholarly journals Modeling the potential impacts of climate change on the water table level of selected forested wetlands in the southeastern United States

2017 ◽  
Vol 21 (12) ◽  
pp. 6289-6305 ◽  
Author(s):  
Jie Zhu ◽  
Ge Sun ◽  
Wenhong Li ◽  
Yu Zhang ◽  
Guofang Miao ◽  
...  
Keyword(s):  
Climate Change ◽  
United States ◽  
Water Table ◽  
Potential Evapotranspiration ◽  
Southeastern United States ◽  
Forested Wetlands ◽  
Wildlife Habitat ◽  
Future Climate ◽  
Future Climate Change ◽  
Southeastern Us

Abstract. The southeastern United States hosts extensive forested wetlands, providing ecosystem services including carbon sequestration, water quality improvement, groundwater recharge, and wildlife habitat. However, these wetland ecosystems are dependent on local climate and hydrology, and are therefore at risk due to climate and land use change. This study develops site-specific empirical hydrologic models for five forested wetlands with different characteristics by analyzing long-term observed meteorological and hydrological data. These wetlands represent typical cypress ponds/swamps, Carolina bays, pine flatwoods, drained pocosins, and natural bottomland hardwood ecosystems. The validated empirical models are then applied at each wetland to predict future water table changes using climate projections from 20 general circulation models (GCMs) participating in Coupled Model Inter-comparison Project 5 (CMIP5) under the Representative Concentration Pathways (RCPs) 4.5 and 8.5 scenarios. We show that combined future changes in precipitation and potential evapotranspiration would significantly alter wetland hydrology including groundwater dynamics by the end of the 21st century. Compared to the historical period, all five wetlands are predicted to become drier over time. The mean water table depth is predicted to drop by 4 to 22 cm in response to the decrease in water availability (i.e., precipitation minus potential evapotranspiration) by the year 2100. Among the five examined wetlands, the depressional wetland in hot and humid Florida appears to be most vulnerable to future climate change. This study provides quantitative information on the potential magnitude of wetland hydrological response to future climate change in typical forested wetlands in the southeastern US.

scholarly journals Frost Damage of Carinata Grown in the Southeastern US

EDIS ◽  
2018 ◽  
Vol 2018 (3) ◽  
Author(s):  
Michael J. Mulvaney ◽  
Ramdeo (Andy) Seepaul ◽  
Ian M. Small ◽  
David L. Wright ◽  
Silvana V. Paula-Moraes ◽  
...  
Keyword(s):  
United States ◽  
Southeastern United States ◽  
Frost Damage ◽  
Jet Fuel ◽  
Commercial Production ◽  
Brassica Carinata ◽  
Oilseed Crop ◽  
Fact Sheet ◽  
Southeastern Us

Brassica carinata is an annual oilseed crop used for the commercial production of jet fuel. One of the challenges to commercialization of this crop in the southeastern United States has been frost damage. This 4-page fact sheet discusses symptomology and ways to minimize risk of frost damage to carinata. Written by Michael J. Mulvaney, Ramdeo Seepaul, Ian Small, David Wright, Silvana Paula-Moraes, Carl Crozier, Paul Cockson, Brian Whipker, and Ramon Leon, and published by the UF/IFAS Agronomy Department, May 2018. https://edis.ifas.ufl.edu/ag420

scholarly journals Evaluation of Deciduous Azaleas for Cold Hardiness Potential in the Southeastern United States

2000 ◽  
Vol 18 (4) ◽  
pp. 230-233
Author(s):  
S.M. Scheiber ◽  
Carol D. Robacker ◽  
Orville M. Lindstrom
Keyword(s):  
United States ◽  
Cold Hardiness ◽  
Southeastern United States ◽  
Temperature Fluctuations ◽  
Field Studies ◽  
Flower Buds ◽  
Cultural Effects ◽  
Laboratory Procedures ◽  
Freeze Test

Abstract Twelve taxa of deciduous azalea were evaluated using laboratory procedures to determine hardiness of stems and flower buds. Rhododendron atlanticum, ‘My Mary’, ‘Nacoochee’, and ‘TNLV1’ exhibited the greatest stem cold hardiness, surviving to at least −29C ± 1 (−20F ± 2) in February 1996. Rhododendron oblongifolium exhibited the least stem cold hardiness, surviving to only −11C ± 1 (10F ± 2). All results were consistent with previous field studies. Except for R. viscosum and R. serrulatum, lowest survival temperatures for stems were analogous to reports available in the literature. Rhododendron viscosum and ‘My Mary’ had the lowest survival temperature recorded for flower buds, −23C ± 1 (−9F ± 2), in February 1998 and February 1999, respectively, though not significantly different than most other taxa examined. Lowest survival temperatures for flower buds varied from published accounts, with buds in the present study being less hardy than previously reported. Differences from published reports in the lowest survival temperatures of stems and flower buds are attributed to provenance, temperature fluctuations, cultural effects on the plants, and differences among freeze test protocols.

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