scholarly journals Sampling density and date along with species selection influence spatial representation of tree-ring reconstructions

2020 ◽  
Vol 16 (5) ◽  
pp. 1901-1916
Author(s):  
Justin T. Maxwell ◽  
Grant L. Harley ◽  
Trevis J. Matheus ◽  
Brandon M. Strange ◽  
Kayla Van Aken ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Spatial Variability ◽  
Tree Ring ◽  
Tree Rings ◽  
Large Scale ◽  
The United States ◽  
Species Selection ◽  
Ring Network ◽  
Calibration Period ◽  
The Us

Abstract. Our understanding of the natural variability of hydroclimate before the instrumental period (ca. 1900 CE in the United States) is largely dependent on tree-ring-based reconstructions. Large-scale soil moisture reconstructions from a network of tree-ring chronologies have greatly improved our understanding of the spatial and temporal variability in hydroclimate conditions, particularly extremes of both drought and pluvial (wet) events. However, certain regions within these large-scale network reconstructions in the US are modeled by few tree-ring chronologies. Further, many of the chronologies currently publicly available on the International Tree-Ring Data Bank (ITRDB) were collected in the 1980s and 1990s, and thus our understanding of the sensitivity of radial growth to soil moisture in the US is based on a period that experienced multiple extremely severe droughts and neglects the impacts of recent, rapid global change. In this study, we expanded the tree-ring network of the Ohio River valley in the US, a region with sparse coverage. We used a total of 72 chronologies across 15 species to examine how increasing the density of the tree-ring network influences the representation of reconstructing the Palmer Meteorological Drought Index (PMDI). Further, we tested how the sampling date and therefore the calibration period influenced the reconstruction models by creating reconstructions that ended in the year 1980 and compared them to reconstructions ending in 2010 from the same chronologies. We found that increasing the density of the tree-ring network resulted in reconstructed values that better matched the spatial variability of instrumentally recorded droughts and, to a lesser extent, pluvials. By extending the calibration period to 2010 compared to 1980, the sensitivity of tree rings to PMDI decreased in the southern portion of our region where severe drought conditions have been absent over recent decades. We emphasize the need of building a high-density tree-ring network to better represent the spatial variability of past droughts and pluvials. Further, chronologies on the ITRDB need updating regularly to better understand how the sensitivity of tree rings to climate may vary through time.

scholarly journals Sampling density and date influence spatial representation of tree ring reconstructions

2020 ◽  
Author(s):  
Justin T. Maxwell ◽  
Grant L. Harley ◽  
Trevis J. Matheus ◽  
Brandon M. Strange ◽  
Kayla Van Aken ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Spatial Variability ◽  
Tree Ring ◽  
Tree Rings ◽  
Large Scale ◽  
The United States ◽  
Severe Drought ◽  
Ring Network ◽  
Tree Ring Data ◽  
The Us

Abstract. Our understanding of the natural variability of hydroclimate before the instrumental period (ca. 1900 in the United States; US) is largely dependent on tree-ring-based reconstructions. Large-scale soil moisture reconstructions from a network of tree-ring chronologies have greatly improved our understanding of the spatial and temporal variability in hydroclimate conditions, particularly extremes of both drought and pluvial (wet) events. However, certain regions within these large-scale reconstructions in the US have a sparse network of tree-ring chronologies. Further, several chronologies were collected in the 1980s and 1990s, thus our understanding of the sensitivity of radial growth to soil moisture in the US is based on a period that experienced multiple extremely severe droughts and neglects the impacts of recent, rapid global change. In this study, we expanded the tree-ring network of the Ohio River Valley in the US, a region with sparse coverage. We used a total of 72 chronologies across 15 species to examine how increasing the density of the tree-ring network influences the representation of reconstructing the Palmer Meteorological Drought Index (PMDI). Further, we tested how the sampling date influenced the reconstruction models by creating reconstructions that ended in the year 1980 and compared them to reconstructions ending in 2010 from the same chronologies. We found that increasing the density of the tree-ring network resulted in reconstructed values that better matched the spatial variability of instrumentally recorded droughts and to a lesser extent, pluvials. By sampling tree in 2010 compared to 1980, the sensitivity of tree rings to PMDI decreased in the southern portion of our region where severe drought conditions have been absent over recent decades. We emphasize the need of building a high-density tree-ring network to better represent the spatial variability of past droughts and pluvials. Further, chronologies on the International Tree-Ring Data Bank need updating regularly to better understand how the sensitivity of tree rings to climate may vary through time.

scholarly journals Estimating Crop and Grass Productivity over the United States Using Satellite Solar-Induced Chlorophyll Fluorescence, Precipitation and Soil Moisture Data

2020 ◽  
Vol 12 (20) ◽  
pp. 3434
Author(s):  
Maryia Halubok ◽  
Zong-Liang Yang
Keyword(s):  
United States ◽  
Soil Moisture ◽  
Chlorophyll Fluorescence ◽  
Spatial Variability ◽  
Great Plains ◽  
Gross Primary Production ◽  
European Space Agency ◽  
The United States ◽  
Soil Moisture Data ◽  
The Us

This study investigates how gross primary production (GPP) estimates can be improved with the use of solar-induced chlorophyll fluorescence (SIF) based on the interdependence between SIF, precipitation, soil moisture and GPP itself. We have used multi-year datasets from Global Ozone Monitoring Experiment-2 (GOME-2), Tropical Rainfall Measuring Mission (TRMM), European Space Agency Climate Change Initiative Soil Moisture (ESA CCI SM), and FLUXNET observations from ten stations in the continental United States. We have employed a GPP quantification framework that makes use of two factors whose influence on the SIF–GPP relationship was not evaluated previously—namely, differential plant sensitivity to water supply at different stages of its lifecycle and spatial variability patterns in SIF that are in contrast to those of GPP, precipitation, and soil moisture. It was found that over the Great Plains and Texas, fluorescence emission levels lag behind precipitation events from about two weeks for grasses to four weeks for crops. The spatial variability of SIF and GPP is shown to be characterized by different patterns: SIF demonstrates less variation over the same spatial extent as compared to GPP, precipitation and soil moisture. Thus, using newly introduced SIF–precipitation lead–lag relationships, we estimate GPP using SIF, precipitation and soil moisture data for grasses and crops over the US by applying the multiple linear regression technique. Our GPP estimates capture the drought impact over the US better than those from Moderate Resolution Imaging Spectroradiometer (MODIS). During the drought year of 2011 over Texas, our GPP values show a decrease by 50–75 gC/m2/month, as opposed to the normal yielding year of 2007. In 2012, a drought year over the Great Plains, we observe a significant reduction in GPP, as compared to 2007. Hence, estimating GPP using specific SIF–GPP relationships, and information on different plant functional types (PFTs) and their interactions with precipitation and soil moisture over the Great Plains and Texas regions can help produce more reasonable GPP estimates.

scholarly journals Solar Thermochemical Hydrogen Production in the USA

2021 ◽  
Vol 13 (14) ◽  
pp. 7804
Author(s):  
Christoph Falter ◽  
Andreas Sizmann
Keyword(s):  
Hydrogen Production ◽  
Large Scale ◽  
Low Cost ◽  
The United States ◽  
Solar Irradiation ◽  
Transport Sector ◽  
Fossil Energy ◽  
The Us ◽  
The Usa ◽  
Solar Thermochemical

Hydrogen produced from renewable energy has the potential to decarbonize parts of the transport sector and many other industries. For a sustainable replacement of fossil energy carriers, both the environmental and economic performance of its production are important. Here, the solar thermochemical hydrogen pathway is characterized with a techno-economic and life-cycle analysis. Assuming a further increase of conversion efficiency and a reduction of investment costs, it is found that hydrogen can be produced in the United States of America at costs of 2.1–3.2 EUR/kg (2.4–3.6 USD/kg) at specific greenhouse gas emissions of 1.4 kg CO2-eq/kg. A geographical potential analysis shows that a maximum of 8.4 × 1011 kg per year can be produced, which corresponds to about twelve times the current global and about 80 times the current US hydrogen production. The best locations are found in the Southwest of the US, which have a high solar irradiation and short distances to the sea, which is beneficial for access to desalinated water. Unlike for petrochemical products, the transport of hydrogen could potentially present an obstacle in terms of cost and emissions under unfavorable circumstances. Given a large-scale deployment, low-cost transport seems, however, feasible.

What's new in the "new" US course towards the DPRK?

2021 ◽  
pp. 16
Author(s):  
Alexander Zhebin
Keyword(s):  
North Korea ◽  
Large Scale ◽  
The United States ◽  
Negotiation Process ◽  
Republic Of Korea ◽  
Us Economy ◽  
The Us ◽  
Nuclear Problem ◽  
The Republic ◽  
Taiwan Straits

The article analyzes the prospects for US-North Korean and inter-Korean relations, taking into account the completed policy review of the new US administration towards the Democratic People's Republic of Korea (DPRK), as well as the results of the President of the Republic of Korea Moon Jae-in’s trip to Washington in May 2021 and his talks with US President Joe Biden. It is concluded that the “new" course proposed by the United States in relation to the DPRK will not lead to a solution to the nuclear problem of the Korean Peninsula and will interfere with the normalization of inter-Korean relations. During his visit to the US President Moon failed to obtain the US consent on ROK more “independent policy” toward North Korea. In spite of lavish investments into US economy and other concessions, Seoul was forced to promise to coordinate his approaches to the DPRK with US and Japan and support US position on Taiwan straits and South China Sea. The author argues that in the current conditions, the introduction of a regime of arms limitation and arms control in Korea should be a necessary stage on the way to complete denuclearization of the peninsula. The transition to a such method of the settlement of the nuclear problem could lead to the resumption of the negotiation process, mutual concessions, including reductions in the level of military-political confrontation, partial or large-scale lifting of economic sanctions in exchange for North Korea's restrictions of its nuclear weapon and missile systems.

scholarly journals Spatial variability and its scale dependency of observed and modeled soil moisture over different climate regions

2013 ◽  
Vol 17 (3) ◽  
pp. 1177-1188 ◽  
Author(s):  
B. Li ◽  
M. Rodell
Keyword(s):  
Soil Moisture ◽  
Spatial Variability ◽  
Land Surface ◽  
Large Scale ◽  
Warm Season ◽  
Scale Dependency ◽  
Convex Shape ◽  
Spatial Moments ◽  
Environmental Controls

Abstract. Past studies on soil moisture spatial variability have been mainly conducted at catchment scales where soil moisture is often sampled over a short time period; as a result, the observed soil moisture often exhibited smaller dynamic ranges, which prevented the complete revelation of soil moisture spatial variability as a function of mean soil moisture. In this study, spatial statistics (mean, spatial variability and skewness) of in situ soil moisture, modeled and satellite-retrieved soil moisture obtained in a warm season (198 days) were examined over three large climate regions in the US. The study found that spatial moments of in situ measurements strongly depend on climates, with distinct mean, spatial variability and skewness observed in each climate zone. In addition, an upward convex shape, which was revealed in several smaller scale studies, was observed for the relationship between spatial variability of in situ soil moisture and its spatial mean when statistics from dry, intermediate, and wet climates were combined. This upward convex shape was vaguely or partially observable in modeled and satellite-retrieved soil moisture estimates due to their smaller dynamic ranges. Despite different environmental controls on large-scale soil moisture spatial variability, the correlation between spatial variability and mean soil moisture remained similar to that observed at small scales, which is attributed to the boundedness of soil moisture. From the smaller support (effective area or volume represented by a measurement or estimate) to larger ones, soil moisture spatial variability decreased in each climate region. The scale dependency of spatial variability all followed the power law, but data with large supports showed stronger scale dependency than those with smaller supports. The scale dependency of soil moisture variability also varied with climates, which may be linked to the scale dependency of precipitation spatial variability. Influences of environmental controls on soil moisture spatial variability at large scales are discussed. The results of this study should be useful for diagnosing large scale soil moisture estimates and for improving the estimation of land surface processes.

Introduction

2019 ◽  
pp. 1-15
Author(s):  
Charlie Laderman
Keyword(s):  
United States ◽  
Twentieth Century ◽  
Large Scale ◽  
The United States ◽  
Great Powers ◽  
Great Power ◽  
World Power ◽  
The Us ◽  
Eastern Question

This introductory chapter outlines why the American response to the destruction of the Ottoman Armenians offers such critical insights into the US rise to world power, its evolving relationship with Britain, and the development of ideas on humanitarian intervention and global order at the turn of the twentieth century. It introduces the Armenian question, setting it within the larger Eastern question, and explains why the Ottoman Empire became a target for outside intervention by the European great powers in the nineteenth century. It explains why the United States, which had traditionally avoided political entanglement in the Near East even while its missionaries established an exceptional role there, began to take a greater interest in the region as its emergence as a great power coincided with the first large-scale Armenian massacres.

AIR TRANSPORTATION POLICY FOR SMALL COMMUNITIES: LESSONS FROM THE U.S. EXPERIENCE

2011 ◽  
Vol 2 (2) ◽  
pp. 1-27 ◽  
Author(s):  
Alda Metrass-Mendes ◽  
Richard De Neufville
Keyword(s):  
Large Scale ◽  
The United States ◽  
Transportation Policy ◽  
Small Communities ◽  
Large Scale Analysis ◽  
Global Trend ◽  
Airline Deregulation ◽  
The Us ◽  
Air Carriers ◽  
The U.S

The last decades have witnessed a global trend toward airline deregulation, which has significant impacts on national policies regarding air accessibility to smaller communities. One important result of this liberalisation is that carriers are no longer constrained to serve routes, and may thus neglect service to less profitable destinations with lower traffic. Economic deregulation can therefore have detrimental effects on smaller communities. The United States has dealt with this issue through its Essential Air Service program. Its experience suggests lessons for other countries. U.S. policies have been reasonably successful in sustaining basic air service to smaller communities over the past thirty years of deregulation. Moreover, they have done so relatively effectively and efficiently. A large-scale analysis of the U.S. experience, and three case studies of the communities of Columbia and Jefferson City (Missouri), Rutland (Vermont), and Merced (California) demonstrate this phenomenon. The results show overall gains in efficiency, mostly attributable to the US policy of encouraging competition between air carriers seeking to provide service to small communities. The major flaw in the U.S. arrangements seems to be that the policies have not kept up with changing conditions since deregulation in 1978.

scholarly journals Localized basal area affects soil respiration temperature sensitivity in a coastal deciduous forest

2020 ◽  
Vol 17 (3) ◽  
pp. 771-780 ◽  
Author(s):  
Stephanie C. Pennington ◽  
Nate G. McDowell ◽  
J. Patrick Megonigal ◽  
James C. Stegen ◽  
Ben Bond-Lamberty
Keyword(s):  
Soil Moisture ◽  
Soil Respiration ◽  
Spatial Variability ◽  
Temperature Sensitivity ◽  
Large Scale ◽  
Deciduous Forest ◽  
Basal Area ◽  
Soil Surface ◽  
Study Sites ◽  
Positive Effect

Abstract. Soil respiration (Rs), the flow of CO2 from the soil surface to the atmosphere, is one of the largest carbon fluxes in the terrestrial biosphere. The spatial variability of Rs is both large and poorly understood, limiting our ability to robustly scale it in space. One factor in Rs spatial variability is the autotrophic contribution from plant roots, but it is uncertain how the presence of plants affects the magnitude and temperature sensitivity of Rs. This study used 1 year of Rs measurements to examine the effect of localized basal area on Rs in the growing and dormant seasons, as well as during moisture-limited times, in a temperate, coastal, deciduous forest in eastern Maryland, USA. In a linear mixed-effects model, tree basal area within a 5 m radius (BA5) exerted a significant positive effect on the temperature sensitivity of soil respiration. Soil moisture was the dominant control on Rs during the dry portions of the year, while soil moisture, temperature, and BA5 all exerted significant effects on Rs in wetter periods. Our results suggest that autotrophic respiration is more sensitive to temperature than heterotrophic respiration at these sites, although we did not measure these source fluxes directly, and that soil respiration is highly moisture sensitive, even in a record-rainfall year. The Rs flux magnitudes (0.46–15.0 µmol m−2 s−1) and variability (coefficient of variability 10 %–23 % across plots) observed in this study were comparable to values observed in similar forests. Six Rs observations would be required in order to estimate the mean across all study sites to within 50 %, and 518 would be required in order to estimate it to within 5 %, with 95 % confidence. A better understanding of the spatial interactions between plants and microbes, as well as the strength and speed of above- and belowground coupling, is necessary to link these processes with large-scale soil-to-atmosphere C fluxes.

scholarly journals Reconstructing drought variability for Mongolia based on a large-scale tree ring network: 1520–1993

2010 ◽  
Vol 115 (D22) ◽  
Author(s):  
N. Davi ◽  
G. Jacoby ◽  
K. Fang ◽  
J. Li ◽  
R. D'Arrigo ◽  
...  
Keyword(s):  
Tree Ring ◽  
Large Scale ◽  
Ring Network ◽  
Drought Variability

scholarly journals Crisis Standards of Care Implementation at the State Level in the United States

2020 ◽  
Vol 35 (6) ◽  
pp. 599-603 ◽  
Author(s):  
Colton Margus ◽  
Ritu R. Sarin ◽  
Michael Molloy ◽  
Gregory R. Ciottone
Keyword(s):  
United States ◽  
Large Scale ◽  
State Level ◽  
The United States ◽  
The State ◽  
Pediatric Care ◽  
Standards Of Care ◽  
Institute Of Medicine ◽  
Full Spectrum ◽  
The Us

AbstractIntroduction:In 2009, the Institute of Medicine published guidelines for implementation of Crisis Standards of Care (CSC) at the state level in the United States (US). Based in part on the then concern for H1N1 pandemic, there was a recognized need for additional planning at the state level to maintain health system preparedness and conventional care standards when available resources become scarce. Despite the availability of this framework, in the years since and despite repeated large-scale domestic events, implementation remains mixed.Problem:Coronavirus disease 2019 (COVID-19) rejuvenates concern for how health systems can maintain quality care when faced with unrelenting burden. This study seeks to outline which states in the US have developed CSC and which areas of care have thus far been addressed.Methods:An online search was conducted for all 50 states in 2015 and again in 2020. For states without CSC plans online, state officials were contacted by email and phone. Public protocols were reviewed to assess for operational implementation capabilities, specifically highlighting guidance on ventilator use, burn management, sequential organ failure assessment (SOFA) score, pediatric standards, and reliance on influenza planning.Results:Thirty-six states in the US were actively developing (17) or had already developed (19) official CSC guidance. Fourteen states had no publicly acknowledged effort. Eleven of the 17 public plans had updated within five years, with a majority addressing ventilator usage (16/17), influenza planning (14/17), and pediatric care (15/17), but substantially fewer addressing care for burn patients (9/17).Conclusion:Many states lacked publicly available guidance on maintaining standards of care during disasters, and many states with specific care guidelines had not sufficiently addressed the full spectrum of hazard to which their health care systems remain vulnerable.

Sign in / Sign up

Export Citation Format

Share Document