High-Resolution Atmospheric Modeling of Fluorotelomer Alcohols and Perfluorocarboxylic Acids in the North American Troposphere

2007 ◽  
Vol 41 (16) ◽  
pp. 5756-5762 ◽  
Author(s):  
Greg Yarwood ◽  
Susan Kemball-Cook ◽  
Michael Keinath ◽  
Robert L. Waterland ◽  
Stephen H. Korzeniowski ◽  
...  
Keyword(s):  
High Resolution ◽  
North American ◽  
Atmospheric Modeling ◽  
The North ◽  
Perfluorocarboxylic Acids ◽  
Fluorotelomer Alcohols

scholarly journals Characterizing the North American Monsoon in the Community Atmosphere Model: Sensitivity to Resolution and Topography

2019 ◽  
Vol 32 (23) ◽  
pp. 8355-8372 ◽  
Author(s):  
Arianna M. Varuolo-Clarke ◽  
Kevin A. Reed ◽  
Brian Medeiros
Keyword(s):  
High Resolution ◽  
Annual Cycle ◽  
North American ◽  
Horizontal Resolution ◽  
North American Monsoon ◽  
Monsoon Precipitation ◽  
Grid Spacing ◽  
Low Level ◽  
The North ◽  
Community Atmosphere Model

Abstract This work examines the effect of horizontal resolution and topography on the North American monsoon (NAM) in experiments with an atmospheric general circulation model. Observations are used to evaluate the fidelity of the representation of the monsoon in simulations from the Community Atmosphere Model version 5 (CAM5) with a standard 1.0° grid spacing and a high-resolution 0.25° grid spacing. The simulated monsoon has some realistic features, but both configurations also show precipitation biases. The default 1.0° grid spacing configuration simulates a monsoon with an annual cycle and intensity of precipitation within the observational range, but the monsoon begins and ends too gradually and does not reach far enough north. This study shows that the improved representation of topography in the high-resolution (0.25° grid spacing) configuration improves the regional circulation and therefore some aspects of the simulated monsoon compared to the 1.0° counterpart. At higher resolution, CAM5 simulates a stronger low pressure center over the American Southwest, with more realistic low-level wind flow than in the 1.0° configuration. As a result, the monsoon precipitation increases as does the amplitude of the annual cycle of precipitation. A moisture analysis sheds light on the monsoon dynamics, indicating that changes in the advection of enthalpy and moist static energy drive the differences between monsoon precipitation in CAM5 1.0° compared to the 0.25° configuration. Additional simulations confirm that these improvements are mainly due to the topographic influence on the low-level flow through the Gulf of California, and not only the increase in horizontal resolution.

scholarly journals Comments on “Regional Impacts of Irrigation in Mexico and the Southwestern United States on Hydrometeorological Fields in the North American Monsoon Region”

2018 ◽  
Vol 19 (2) ◽  
pp. 477-481 ◽  
Author(s):  
Theodore J. Bohn ◽  
Enrique R. Vivoni
Keyword(s):  
North American ◽  
Gulf Of California ◽  
Wrf Model ◽  
Summer Precipitation ◽  
Atmospheric Modeling ◽  
Irrigated Agriculture ◽  
North American Monsoon ◽  
Impact Surface ◽  
The North ◽  
The Impact

Abstract For their investigation of the impact of irrigated agriculture on hydrometeorological fields in the North American monsoon (NAM) region, Mahalov et al. used the Weather Research and Forecasting (WRF) Model to simulate weather over the NAM region in the summer periods of 2000 and 2012, with and without irrigation applied to the regional croplands. Unfortunately, while the authors found that irrigated agriculture may indeed influence summer precipitation, the magnitude, location, and seasonality of their irrigation inputs were substantially inaccurate because of 1) the assumption that pixels classified as “irrigated cropland” are irrigated during the summer and 2) an outdated land cover map that misrepresents known agricultural districts. The combined effects of these errors are 1) an overestimation of irrigated croplands by a factor of 3–10 along the coast of the Gulf of California and by a factor of 1.5 near the Colorado River delta and 2) a large underestimation of irrigation by a factor of 7–10 in Chihuahua, particularly in 2012. Given the sensitivity of the WRF simulations conducted by Mahalov et al. to the presence of irrigated agriculture, it is expected that the identified errors would significantly impact surface moisture and energy fluxes, resulting in noticeably different effects on precipitation. The authors suggest that the analysis of irrigation effects on precipitation using coupled land–atmospheric modeling systems requires careful specification of the spatiotemporal distribution of irrigated croplands.

scholarly journals Atmospherically-produced beryllium-10 in annually laminated late-glacial sediments of the North American Varve Chronology

2020 ◽  
Author(s):  
Greg Balco ◽  
Benjamin D. DeJong ◽  
John C. Ridge ◽  
Paul R. Bierman ◽  
Dylan H. Rood
Keyword(s):  
High Resolution ◽  
North American ◽  
Time Scale ◽  
Ice Core ◽  
The Other ◽  
Varve Chronology ◽  
The North ◽  
Proglacial Lakes ◽  
Period Variations ◽  
Climate Events

Abstract. We attempt to synchronize the North American Varve Chronology (NAVC) with the calendar year time scale by comparing records of atmospherically produced Be-10 fallout in the NAVC and in ice cores. The North American Varve Chronology (NAVC) is a sequence of 5659 varves deposited in a series of proglacial lakes adjacent to the southeast margin of the retreating Laurentide Ice Sheet between approximately 18,200–12,500 years before present. Because properties of NAVC varves are related to climate, the NAVC is also a climate proxy record with annual resolution, and our overall goal is to place the NAVC and ice core records on the same time scale to facilitate high-resolution correlation of climate events. Total Be-10 concentrations in NAVC sediments are within the range of those observed in other lacustrine records of Be-10 fallout, but Be-9 and Be-10 concentrations considered together show that the majority of Be-10 is present in glacial sediment when it enters the lake, and only a minority of total Be-10 derives from atmospheric fallout at the time of sediment deposition. Because of this, an initial strategy to determine whether or not Be-10 fallout variations were recorded in NAVC sediments by attempting to observe the characteristic 11-year solar cycle in high-resolution sections of varve sequences was inconclusive: observed short-period variations at the expected magnitude of this cycle were not distinguishable from measurement scatter. On the other hand, we did observe centennial-period variations in Be-10 fallout that are replicated between separate varve sections and have similar magnitude and frequency as coeval Be-10 fallout variations recorded in ice core records. These are most prominent in glacial sections of the NAVC that were deposited in proglacial lakes, but are suppressed in paraglacial sections of the NAVC deposited in lakes lacking direct glacial sediment input, which leads us to conclude that proglacial lakes whose watershed likely includes a large portion of the ablation area of an ice sheet can effectively record Be-10 fallout. We matched observed centennial-scale Be-10 fallout variations in two segments of the NAVC to ice core Be-10 fallout records. Although the calibration of the NAVC to the calendar year time scale implied by these matches is similar to that proposed previously in independent calibrations based on radiocarbon data and correlation of climate events, matches for the two different segments disagree with each other and with the independent calibrations by 50–200 years. One of these matches is not consistent with independent evidence and is probably not valid, but the other is consistent with most, although not all, evidence and may be valid. This leaves several remaining ambiguities in whether or not Be-10 fallout variations can, in fact, be used for synchronizing NAVC and ice core timescales, but these could likely be resolved by higher-resolution and replicate Be-10 measurements on targeted sections of the NAVC.

scholarly journals Long-Term Regional Estimates of Evapotranspiration for Mexico Based on Downscaled ISCCP Data

2010 ◽  
Vol 11 (2) ◽  
pp. 253-275 ◽  
Author(s):  
Justin Sheffield ◽  
Eric F. Wood ◽  
Francisco Munoz-Arriola
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
North American ◽  
Remote Sensing Data ◽  
Surface Model ◽  
Spatial Average ◽  
Sensing Data ◽  
The North ◽  
True Value

Abstract The development and evaluation of a long-term high-resolution dataset of potential and actual evapotranspiration for Mexico based on remote sensing data are described. Evapotranspiration is calculated using a modified version of the Penman–Monteith algorithm, with input radiation and meteorological data from the International Satellite Cloud Climatology Project (ISCCP) and vegetation distribution derived from Advanced Very High Resolution Radiometer (AVHRR) products. The ISCCP data are downscaled to ⅛° resolution using statistical relationships with data from the North American Regional Reanalysis (NARR). The final product is available at ⅛°, daily, for 1984–2006 for all Mexico. Comparisons are made with the NARR offline land surface model and measurements from approximately 1800 pan stations. The remote sensing estimate follows well the seasonal cycle and spatial pattern of the comparison datasets, with a peak in late summer at the height of the North American monsoon and highest values in low-lying and coastal regions. The spatial average over Mexico is biased low by about 0.3 mm day−1, with a monthly rmse of about 0.5 mm day−1. The underestimation may be related to the lack of a model for canopy evaporation, which is estimated to be up to 30% of total evapotranspiration. Uncertainties in both the remote sensing–based estimates (because of input data uncertainties) and the true value of evapotranspiration (represented by the spread in the comparison datasets) are up to 0.5 and 1.2 mm day−1, respectively. This study is a first step in quantifying the long-term variation in global land evapotranspiration from remote sensing data.

scholarly journals An Evaluation of Paired Regional/Convection-Allowing Forecast Vertical Thermodynamic Profiles in Warm-Season, Thunderstorm-Supporting Environments

2018 ◽  
Vol 33 (6) ◽  
pp. 1547-1566 ◽  
Author(s):  
Clark Evans ◽  
Steven J. Weiss ◽  
Israel L. Jirak ◽  
Andrew R. Dean ◽  
David S. Nevius
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Planetary Boundary Layer ◽  
North American ◽  
Mesoscale Model ◽  
Warm Season ◽  
Regional Models ◽  
The North ◽  
Nest Model ◽  
Model Pair

Abstract This study evaluates forecast vertical thermodynamic profiles and derived thermodynamic parameters from two regional/convection-allowing model pairs, the North American Mesoscale Forecast System and the North American Mesoscale Nest model pair and the Rapid Refresh and High Resolution Rapid Refresh model pair, in warm-season, thunderstorm-supporting environments. Differences in bias and mean absolute error between the regional and convection-allowing models in each of the two pairs, while often statistically significant, are practically small for the variables, parameters, and vertical levels considered, such that the smaller-scale variability resolved by convection-allowing models does not degrade their forecast skill. Model biases shared by the regional and convection-allowing models in each pair are documented, particularly the substantial cool and moist biases in the planetary boundary layer arising from the Mellor–Yamada–Janjić planetary boundary layer parameterization used by the North American Mesoscale model and the Nest version as well as the middle-tropospheric moist bias shared by the Rapid Refresh and High Resolution Rapid Refresh models. Bias and mean absolute errors typically have larger magnitudes in the evening, when buoyancy is a significant contributor to turbulent vertical mixing, than in the morning. Vertical thermodynamic profile biases extend over a deep vertical layer in the western United States given strong sensible heating of the underlying surface. The results suggest that convection-allowing models can fulfill the use cases typically and historically met by regional models in operations at forecast entities such as the Storm Prediction Center, a fruitful finding given the proposed elimination of regional models with the Next-Generation Global Prediction System initiative.

scholarly journals Atmospherically produced beryllium-10 in annually laminated late-glacial sediments of the North American Varve Chronology

Geochronology ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 1-33
Author(s):  
Greg Balco ◽  
Benjamin D. DeJong ◽  
John C. Ridge ◽  
Paul R. Bierman ◽  
Dylan H. Rood
Keyword(s):  
High Resolution ◽  
North American ◽  
Ice Core ◽  
Glacial Sediment ◽  
Climate Proxy ◽  
Varve Chronology ◽  
The North ◽  
Proglacial Lakes ◽  
Short Period ◽  
Period Variations

Abstract. We attempt to synchronize the North American Varve Chronology (NAVC) with ice core and calendar year timescales by comparing records of atmospherically produced 10Be fallout in the NAVC and in ice cores. The North American Varve Chronology (NAVC) is a sequence of 5659 varves deposited in a series of proglacial lakes adjacent to the southeast margin of the retreating Laurentide Ice Sheet between approximately 18 200 and 12 500 years before present. Because properties of NAVC varves are related to climate, the NAVC is also a climate proxy record with annual resolution, and our overall goal is to place the NAVC and ice core records on the same timescale to facilitate high-resolution correlation of climate proxy variations in both. Total 10Be concentrations in NAVC sediments are within the range of those observed in other lacustrine records of 10Be fallout, but 9Be and 10Be concentrations considered together show that the majority of 10Be is present in glacial sediment when it enters the lake, and only a minority of total 10Be derives from atmospheric fallout at the time of sediment deposition. Because of this, an initial experiment to determine whether or not 10Be fallout variations were recorded in NAVC sediments by attempting to observe the characteristic 11-year solar cycle in short varve sections sampled at high resolution was inconclusive: short-period variations at the expected magnitude of this cycle were not distinguishable from measurement scatter. On the other hand, longer varve sequences sampled at decadal resolution display centennial-period variations in reconstructed 10Be fallout that have similar properties as coeval 10Be fallout variations recorded in ice core records. These are most prominent in glacial sections of the NAVC that were deposited in proglacial lakes and are suppressed in paraglacial sections of the NAVC that were deposited in lakes lacking direct glacial sediment input. We attribute this difference to the fact that buffering of 10Be fallout by soil adsorption can filter out short-period variations in an entirely deglaciated watershed, but such buffering cannot occur in the ablation zone of an ice sheet. This implies that proglacial lakes whose watershed is mostly glacial may effectively record 10Be fallout variations. We attempted to match centennial-period variations in reconstructed 10Be fallout flux from two segments of the NAVC with ice core fallout records. For both records, it is possible to obtain matches that result in acceptable correlation between NAVC and ice core 10Be fallout records, but the best-fitting matches for the two segments disagree, and only one of them is consistent with independent calendar year calibrations of the NAVC and therefore potentially valid. This leaves several remaining ambiguities in whether or not 10Be fallout variations can, in fact, be used for synchronizing NAVC and ice core timescales, but these could most likely be resolved by higher-resolution and replicate 10Be measurements on targeted sections of the NAVC.

scholarly journals A new correlation of the Cretaceous formations of the Western Interior of the United States, I: Santonian-Maastrichtian formations and dinosaur biostratigraphy

2016 ◽  
Author(s):  
Denver W Fowler
Keyword(s):  
High Resolution ◽  
Late Cretaceous ◽  
North American ◽  
The United States ◽  
Current Standard ◽  
Continental Scale ◽  
The North ◽  
Stratigraphic Ranges ◽  
First Time ◽  
Radiometric Dates

Late Cretaceous deposits of the North American Western Interior represent the best, if not only, opportunity to construct a high-resolution chronostratigraphic framework within which to conduct continental-scale geological and paleontological analyses. This is due to the serendipitous combination of large areas of outcrop, interfingering marine units with biostratigraphically informative fossils, and a consistent scattering of radiometric dates due to synorogenic volcanic activity. Accurate correlation is essential for testing a large number of current geological and paleobiological hypotheses; however, despite the large amount of data available, many published correlations suffer from inaccuracies or are simply based on outdated information. Here I present a comprehensive high-resolution stratigraphic chart for terrestrial Late Cretaceous units of North America, combining published chronostratigraphic, lithostratigraphic, and biostratigraphic data. For the first time, nearly two hundred 40Ar / 39Ar radiometric dates are recalibrated to both current standard and decay constant pairings, correcting errors in previous recalibrations. Revisions to the stratigraphic placement of most units are slight, but important changes are made to the proposed correlations of the Aguja and Javelina Formations, Texas, and miscalculations in recently published analyses are corrected which in particular affects the relative age positions of the Belly River Group, Alberta; Judith River Group, Montana, Kaiparowits Formation, Utah, and Fruitland and Kirtland Formations, New Mexico. This work represents the most extensive and accurate interbasinal correlation currently available for the North American Western Interior and should replace all previously published similar works and diagrams. The stratigraphic ranges of selected dinosaur clades are plotted on the chronostratigraphic framework, typically forming stacks of short-duration species which do not overlap stratigraphically with preceding or succeeding forms. This is the expected pattern which is produced by an anagenetic mode of evolution, suggesting that true branching (speciation) events were rare and may have geographic significance. Purported north-south provinciality of dinosaurs is shown to be mostly an artifact of stratigraphic miscorrelation. Rapid stepwise acquisition of display characters in many dinosaur clades, in particular chasmosaurine ceratopsids, suggests that they may represent the highest resolution biostratigraphic markers to be used where radiometric dates are not available.

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