scholarly journals North American CO<sub>2</sub> exchange: inter-comparison of modeled estimates with results from a fine-scale atmospheric inversion

2012 ◽  
Vol 9 (1) ◽  
pp. 457-475 ◽  
Author(s):  
S. M. Gourdji ◽  
K. L. Mueller ◽  
V. Yadav ◽  
D. N. Huntzinger ◽  
A. E. Andrews ◽  
...  
Keyword(s):  
Spatial Patterns ◽  
North American ◽  
Co2 Fluxes ◽  
Fine Scale ◽  
Bottom Up ◽  
Near Surface ◽  
Continental Scale ◽  
The North ◽  
Atmospheric Observations ◽  
Atmospheric Inversion

Abstract. Atmospheric inversion models have the potential to quantify CO2 fluxes at regional, sub-continental scales by taking advantage of near-surface CO2 mixing ratio observations collected in areas with high flux variability. This study presents results from a series of regional geostatistical inverse models (GIM) over North America for 2004, and uses them as the basis for an inter-comparison to other inversion studies and estimates from biospheric models collected through the North American Carbon Program Regional and Continental Interim Synthesis. Because the GIM approach does not require explicit prior flux estimates and resolves fluxes at fine spatiotemporal scales (i.e. 1° × 1°, 3-hourly in this study), it avoids temporal and spatial aggregation errors and allows for the recovery of realistic spatial patterns from the atmospheric data relative to previous inversion studies. Results from a GIM inversion using only available atmospheric observations and a fine-scale fossil fuel inventory were used to confirm the quality of the inventory and inversion setup. An inversion additionally including auxiliary variables from the North American Regional Reanalysis found inferred relationships with flux consistent with physiological understanding of the biospheric carbon cycle. Comparison of GIM results with bottom-up biospheric models showed stronger agreement during the growing relative to the dormant season, in part because most of the biospheric models do not fully represent agricultural land-management practices and the fate of both residual biomass and harvested products. Comparison to earlier inversion studies pointed to aggregation errors as a likely source of bias in previous sub-continental scale flux estimates, particularly for inversions that adjust fluxes at the coarsest scales and use atmospheric observations averaged over long periods. Finally, whereas the continental CO2 boundary conditions used in the GIM inversions have a minor impact on spatial patterns, they have a substantial impact on the continental carbon budget, with a difference of 0.8 PgC yr−1 in the total continental flux resulting from the use of two plausible sets of boundary CO2 mixing ratios. Overall, this inter-comparison study helps to assess the state of the science in estimating regional-scale CO2 fluxes, while pointing towards the path forward for improvements in future top-down and bottom-up modeling efforts.

scholarly journals Impact of hydrological variations on modeling of peatland CO2 fluxes: Results from the North American Carbon Program site synthesis

2012 ◽  
Vol 117 (G1) ◽  
Author(s):  
Benjamin N. Sulman ◽  
Ankur R. Desai ◽  
Nicole M. Schroeder ◽  
Dan Ricciuto ◽  
Alan Barr ◽  
...  
Keyword(s):  
North American ◽  
Co2 Fluxes ◽  
The North

scholarly journals Evolutionary Algorithms for Community Detection in Continental-Scale High-Voltage Transmission Grids

Symmetry ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1472 ◽  
Author(s):  
Manuel Guerrero ◽  
Raul Baños ◽  
Consolación Gil ◽  
Francisco G. Montoya ◽  
Alfredo Alcayde
Keyword(s):  
Genetic Algorithm ◽  
Evolutionary Algorithms ◽  
Power Systems ◽  
Community Detection ◽  
North American ◽  
Flow Analysis ◽  
Power Grids ◽  
Improved Genetic Algorithm ◽  
Continental Scale ◽  
The North

Symmetry is a key concept in the study of power systems, not only because the admittance and Jacobian matrices used in power flow analysis are symmetrical, but because some previous studies have shown that in some real-world power grids there are complex symmetries. In order to investigate the topological characteristics of power grids, this paper proposes the use of evolutionary algorithms for community detection using modularity density measures on networks representing supergrids in order to discover densely connected structures. Two evolutionary approaches (generational genetic algorithm, GGA+, and modularity and improved genetic algorithm, MIGA) were applied. The results obtained in two large networks representing supergrids (European grid and North American grid) provide insights on both the structure of the supergrid and the topological differences between different regions. Numerical and graphical results show how these evolutionary approaches clearly outperform to the well-known Louvain modularity method. In particular, the average value of modularity obtained by GGA+ in the European grid was 0.815, while an average of 0.827 was reached in the North American grid. These results outperform those obtained by MIGA and Louvain methods (0.801 and 0.766 in the European grid and 0.813 and 0.798 in the North American grid, respectively).

scholarly journals The Impact of Large-Scale Orography on Northern Hemisphere Winter Synoptic Temperature Variability

2019 ◽  
Vol 32 (18) ◽  
pp. 5799-5814 ◽  
Author(s):  
Nicholas J. Lutsko ◽  
Jane Wilson Baldwin ◽  
Timothy W. Cronin
Keyword(s):  
North America ◽  
Northern Hemisphere ◽  
North American ◽  
Large Scale ◽  
Temperature Variability ◽  
Temperature Gradients ◽  
Northwest Pacific ◽  
Near Surface ◽  
The North ◽  
The Impact

Abstract The impact of large-scale orography on wintertime near-surface (850 hPa) temperature variability on daily and synoptic time scales (from days to weeks) in the Northern Hemisphere is investigated. Using a combination of theory, idealized modeling work, and simulations with a comprehensive climate model, it is shown that large-scale orography reduces upstream temperature gradients, in turn reducing upstream temperature variability, and enhances downstream temperature gradients, enhancing downstream temperature variability. Hence, the presence of the Rockies on the western edge of the North American continent increases temperature gradients over North America and, consequently, increases North American temperature variability. By contrast, the presence of the Tibetan Plateau and the Himalayas on the eastern edge of the Eurasian continent damps temperature variability over most of Eurasia. However, Tibet and the Himalayas also interfere with the downstream development of storms in the North Pacific storm track, and thus damp temperature variability over North America, by approximately as much as the Rockies enhance it. Large-scale orography is also shown to impact the skewness of downstream temperature distributions, as temperatures to the north of the enhanced temperature gradients are more positively skewed while temperatures to the south are more negatively skewed. This effect is most clearly seen in the northwest Pacific, off the east coast of Japan.

The Lithoprobe trans-continental lithospheric cross sections: imaging the internal structure of the North American continentThis article is one of a series of papers published in this Special Issue on the theme Lithoprobe — parameters, processes, and the evolution of a continent.Lithoprobe Publication 1487.

2010 ◽  
Vol 47 (5) ◽  
pp. 821-857 ◽  
Author(s):  
Philip T.C. Hammer ◽  
Ron M. Clowes ◽  
Fred A. Cook ◽  
Arie J. van der Velden ◽  
Kris Vasudevan
Keyword(s):  
Cross Sections ◽  
North American ◽  
Lithospheric Mantle ◽  
Large Scale ◽  
Passive Margin ◽  
Cascadia Subduction Zone ◽  
American Continent ◽  
North American Continent ◽  
Continental Scale ◽  
The North

Three lithospheric cross sections provide a continental-scale synthesis of more than two decades of coordinated multidisciplinary research during the Canadian Lithoprobe project. The sections are based on seismic reflection and refraction data combined with a broad range of geological, geochemical, geochronological, and geophysical data. The dataset is derived from remnants of nearly every kind of tectonic regime, and the geologic history of the entrained rocks spans the Present to the Mesoarchean. The longest of the three cross sections is located within a 6000 km long Trans-Canada corridor traversing the North American continent at 45°N–55°N. From west to east, the profile crosses the Juan de Fuca ridge and active Cascadia subduction zone, the Cordilleran, Albertan, and Trans-Hudson orogens, the Superior Province, the Midcontinent rift, the Grenville and Appalachian orogens, and the Atlantic passive margin. The two northern cross sections include (i) a 2000 km long corridor in northwestern Canada (54°N–63°N) crossing the Cordilleran, Wopmay, and Slave orogens; and (ii) a 1600 km long corridor in northeastern Canada (52°N–61°N) crossing the New Quebec and Torngat orogens, the Nain craton, and the Makkovik and Grenville orogens. The unprecedented scale of the cross sections illuminates the assembly of the North American continent. Relationships between orogens are emphasized; plate collisions and accretions have sequentially stacked orogen upon orogen such that the older crust forms basement to the next younger. The large-scale perspective of these regional sections highlights the subhorizontal Moho that is indicative of either structural or thermal re-equilibration (or both), as few crustal roots beneath orogens are preserved. In contrast, heterogeneities in the lithospheric mantle suggest that, in certain situations, relict subducted or delaminated lithosphere can remain intact beneath and eventually within cratonic lithospheric mantle.

scholarly journals The Basic Ingredients of the North Atlantic Storm Track. Part II: Sea Surface Temperatures

2011 ◽  
Vol 68 (8) ◽  
pp. 1784-1805 ◽  
Author(s):  
David James Brayshaw ◽  
Brian Hoskins ◽  
Michael Blackburn
Keyword(s):  
North Atlantic ◽  
Gulf Stream ◽  
Storm Track ◽  
Horizontal Wind ◽  
Near Surface ◽  
Continental Scale ◽  
The North ◽  
The North Atlantic ◽  
The Impact ◽  
Sst Gradient

Abstract The impact of North Atlantic SST patterns on the storm track is investigated using a hierarchy of GCM simulations using idealized (aquaplanet) and “semirealistic” boundary conditions in the atmospheric component (HadAM3) of the third climate configuration of the Met Office Unified Model (HadCM3). This framework enables the mechanisms determining the tropospheric response to North Atlantic SST patterns to be examined, both in isolation and in combination with continental-scale landmasses and orography. In isolation, a “Gulf Stream” SST pattern acts to strengthen the downstream storm track while a “North Atlantic Drift” SST pattern weakens it. These changes are consistent with changes in the extratropical SST gradient and near-surface baroclinicity, and each storm-track response is associated with a consistent change in the tropospheric jet structure. Locally enhanced near-surface horizontal wind convergence is found over the warm side of strengthened SST gradients associated with ascending air and increased precipitation, consistent with previous studies. When the combined SST pattern is introduced into the semirealistic framework (including the “North American” continent and the “Rocky Mountains”), the results suggest that the topographically generated southwest–northeast tilt in the North Atlantic storm track is enhanced. In particular, the Gulf Stream shifts the storm track south in the western Atlantic whereas the strong high-latitude SST gradient in the northeastern Atlantic enhances the storm track there.

scholarly journals Flow-dependent and dynamical systems analyses of predictability of the Pacific-North American summertime circulation

2021 ◽  
Author(s):  
Ebrahim Nabizadeh ◽  
Sandro Lubis ◽  
Pedram Hassanzadeh
Keyword(s):  
Dynamical Systems ◽  
North American ◽  
Initial Conditions ◽  
Weather Prediction ◽  
Self Organizing Map ◽  
Near Surface ◽  
Pacific North American ◽  
The North ◽  
Temperature And Precipitation ◽  
Precipitation Anomalies

Forecast skills of numerical weather prediction (NWP) models and intrinsic predictability can be flow-dependent, e.g., different amongweather regimes. Here, we have examined the predictability of distinct Pacific-North American weather regimes in June-September. Fourweather regimes are identified using a self-organizing map analysis of daily 500-hPa geopotential height anomalies, and are shown to havedistinct and coherent links to near-surface temperature and precipitation anomalies over the North American continent. The 4 to 14-dayforecast skills of these 4 regimes are quantified for the ECMWF and the NCEP models (from the TIGGE project) and the Global EnsembleForecast System (GEFS). Based on anomaly correlation coefficient, persistence, and transition frequency, the highest forecast skills areconsistently found for regime 3 (Arctic high). In general, the least skillful forecasts are for regime 1 (Pacific trough). The instantaneous localdimension and persistence of each regime are computed using a dynamical systems-based analysis. The local dimension and persistenceare indicators of intrinsic predictability. This analysis robustly shows that regime 3 has the highest intrinsic predictability. The analysisalso suggests that overall, regime 1 has the lowest intrinsic predictability. These findings are consistent with the high (low) forecast skillsof NWP models for regime 3 (regime 1). Weather regime 1 is associated with above-normal temperature and precipitation anomalies overwestern North America and around the Gulf of Mexico region, indicating potentially important implications for the poor predictability ofthis regime. The dynamical systems analysis suggests that better estimates of initial conditions might improve the forecasts of this regime.

scholarly journals Spatiotemporal distribution of Holocene populations in North America

2015 ◽  
Vol 112 (39) ◽  
pp. 12127-12132 ◽  
Author(s):  
Michelle A. Chaput ◽  
Björn Kriesche ◽  
Matthew Betts ◽  
Andrew Martindale ◽  
Rafal Kulik ◽  
...  
Keyword(s):  
North America ◽  
North American ◽  
Kernel Method ◽  
Temporal Frequency ◽  
Human Populations ◽  
Human Occupation ◽  
Migration Routes ◽  
Frequency Distributions ◽  
Continental Scale ◽  
The North

As the Cordilleran and Laurentide Ice Sheets retreated, North America was colonized by human populations; however, the spatial patterns of subsequent population growth are unclear. Temporal frequency distributions of aggregated radiocarbon (14C) dates are used as a proxy of population size and can be used to track this expansion. The Canadian Archaeological Radiocarbon Database contains more than 35,000 14C dates and is used in this study to map the spatiotemporal demographic changes of Holocene populations in North America at a continental scale for the past 13,000 y. We use the kernel method, which converts the spatial distribution of 14C dates into estimates of population density at 500-y intervals. The resulting maps reveal temporally distinct, dynamic patterns associated with paleodemographic trends that correspond well to genetic, archaeological, and ethnohistoric evidence of human occupation. These results have implications for hypothesizing and testing migration routes into and across North America as well as the relative influence of North American populations on the evolution of the North American ecosystem.

scholarly journals Meta-Analysis of Salmon Trophic Ecology Reveals Spatial and Interspecies Dynamics Across the North Pacific Ocean

2021 ◽  
Vol 8 ◽  
Author(s):  
Caroline Graham ◽  
Evgeny A. Pakhomov ◽  
Brian P. V. Hunt
Keyword(s):  
Spatial Patterns ◽  
North Pacific ◽  
Large Scale ◽  
Prey Availability ◽  
Gulf Of Alaska ◽  
Marine Ecology ◽  
Niche Width ◽  
Fine Scale ◽  
The North ◽  
The North Pacific

We examined spatial patterns in diet, trophic niche width and niche overlap for chum, pink and sockeye salmon across the North Pacific during 1959–1969. This is a baseline period before major hatchery enhancement occurred coinciding with a negative phase of the Pacific Decadal Oscillation. Large-scale (between regions) and fine-scale (within regions) spatial and interspecies differences were apparent. In the Western Subarctic, all species tended to consume zooplankton. In the Bering Sea, chum consumed zooplankton, while sockeye and pink alternated between zooplankton and micronekton. In the Gulf of Alaska/Eastern Subarctic, chum and sockeye specialized on gelatinous zooplankton and cephalopod prey, respectively, while pink consumed a mixture of zooplankton and micronekton. The highest diet overlap across the North Pacific was between pink and sockeye (46.6%), followed by chum and pink (31.8%), and chum and sockeye (30.9%). Greater diet specialization was evident in the Gulf of Alaska/Eastern Subarctic compared to the Western Pacific. Generally, species had higher niche width and overlap in areas of high prey availability, and this was particularly evident for chum salmon. In addition to the large-scale trophic patterns, our data revealed novel fine-scale spatial patterns, including latitudinal, onshore-offshore, and cross-gyre gradients. Our results showed that pink tended to be more generalist consumers, and their diets may be a better reflection of overall prey presence and abundance in the environment. Conversely, chum and sockeye tended to be more specialist consumers, and their diets may provide a better reflection of interspecies dynamics or prey availability. This study provides a baseline for comparison with current and future changes in salmon marine ecology and North Pacific ecosystems. Finally, we identify two important data gaps that need addressing, that of improved taxonomic resolution diet data for Pacific salmon and focused research on sub-mesoscale oceanographic features that may play an important role in salmon health and productivity.

scholarly journals Gradients of Column CO<sub>2</sub> across North America from the NOAA Global Greenhouse Gas Reference Network

2017 ◽  
Author(s):  
Xin Lan ◽  
Pieter Tans ◽  
Colm Sweeney ◽  
Arlyn Andrews ◽  
Andrew Jacobson ◽  
...  
Keyword(s):  
North America ◽  
Greenhouse Gas ◽  
Spatial Patterns ◽  
Reference Network ◽  
Spatial Gradients ◽  
Continental Scale ◽  
The North ◽  
Satellite Retrievals ◽  
The Impact ◽  
Total Column

Abstract. This study analyzes seasonal and spatial patterns of column carbon dioxide (CO2) over North America calculated from aircraft and tall tower measurements from the NOAA Global Greenhouse Gas Reference Network from 2004 to 2014. Consistent with expectations, gradients between the eight regions studied are larger below 2 km than above 5 km. The 11-year mean CO2 dry mole fraction (XCO2) in the column below ~ 330 hPa (~ 8 km above sea level) from NOAA's CO2 data assimilation model, CarbonTracker (CT2015), demonstrates good agreement with those calculated from calibrated measurements on aircraft and towers. Total column XCO2 was attained by combining modeled CO2 above 330 hPa from CT2015 with the measurements. We find large spatial gradients of total column XCO2 during June to August, and the north and northeast regions have ~ 3 ppm stronger summer drawdown than the south and southwest regions. The spatial gradients of total column XCO2 across North America mainly reflect large-scale circulation patterns rather than regional surface sources and sinks. We have conducted a CarbonTracker experiment to investigate the impact of Eurasian long-range transport. The result suggests that the large summer time Eurasian boreal flux contributes about half of the north-south column XCO2 gradient across North America. Our results confirm that continental-scale total column XCO2 gradients simulated by CarbonTracker are realistic and can be used to evaluate the credibility of spatial patterns from satellite retrievals, such as the long term average spatial patterns from satellite retrievals reported for Europe which show larger spatial difference (~ 6 ppm) and scattered hot spots.

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