scholarly journals Polarimetric Observations of Chaff Using the WSR-88D Network

2018 ◽  
Vol 57 (5) ◽  
pp. 1063-1081 ◽  
Author(s):  
James M. Kurdzo ◽  
Earle R. Williams ◽  
David J. Smalley ◽  
Betty J. Bennett ◽  
David C. Patterson ◽  
...  
Keyword(s):  
United States ◽  
The United States ◽  
Single Event ◽  
Large Database ◽  
Radar Observations ◽  
Automated Algorithms ◽  
Training Exercises ◽  
Differential Reflectivity ◽  
Radar Countermeasure ◽  
Reflectivity Factor

AbstractChaff is a radar countermeasure typically used by military branches in training exercises around the United States. Chaff within view of the S-band WSR-88D beam can appear prominently on radar users’ displays. Knowledge of chaff characteristics is useful for radar users to discriminate between chaff and weather echoes and for automated algorithms to do the same. The WSR-88D network provides dual-polarimetric capabilities across the United States, leading to the collection of a large database of chaff cases. This database is analyzed to determine the characteristics of chaff in terms of the reflectivity factor and polarimetric variables on large scales. Particular focus is given to the dynamics of differential reflectivity ZDR in chaff and its dependence on height. In contrast to radar observations of chaff for a single event, this study is able to reveal a repeatable and new pattern of radar chaff observations. A discussion about the observed characteristics is presented, and hypotheses for the observed ZDR dynamics are put forth.

Remarks by Stephen Pomper

2017 ◽  
Vol 111 ◽  
pp. 123-127
Author(s):  
Stephen Pomper
Keyword(s):  
United States ◽  
International Law ◽  
Security Council ◽  
The United States ◽  
Single Event ◽  
Humanitarian Emergency ◽  
The Third ◽  
The Face ◽  
Legal Justification ◽  
The U.S

We are having this conversation now because of the April 7 strikes on the Shayrat Airfield in Syria, but the question of how one justifies forcible measures in the context of a humanitarian emergency, and in the face of a deadlocked Security Council, is one that deserves urgent attention beyond the context of any single event. Progress toward answering this question has, however, been mired in a long-standing debate between those who believe that there is no credible international law justification for humanitarian intervention—and that the U.S. government should instead justify interventions like those taken at Kosovo and Shayrat as morally “legitimate”—and those who believe a legal justification can and should be put forward. I am very much in the latter camp and will use my time now to explain how I arrived at this position as a policy and as a legal matter by looking at three questions: the first question is whether legal justification is the direction that the United States should go in as a matter of policy. The second question is whether legal justification is credibly available as a matter of international law. The third question (which assumes the answer to the first and second is yes) is how to go about articulating and disseminating such a justification. Let me take these in order.

scholarly journals Investigations of Backscatter Differential Phase in the Melting Layer

2014 ◽  
Vol 53 (10) ◽  
pp. 2344-2359 ◽  
Author(s):  
Silke Trömel ◽  
Alexander V. Ryzhkov ◽  
Pengfei Zhang ◽  
Clemens Simmer
Keyword(s):  
United States ◽  
Cross Correlation ◽  
The United States ◽  
Dual Frequency ◽  
Melting Layer ◽  
Differential Phase ◽  
X Band ◽  
Aggregation Processes ◽  
Differential Reflectivity ◽  
Theoretical Simulations

AbstractBackscatter differential phase δ within the melting layer has been identified as a reliably measurable but still underutilized polarimetric variable. Polarimetric radar observations at X band in Germany and S band in the United States are presented that show maximal observed δ of 8.5° at X band but up to 70° at S band. Dual-frequency observations at X and C band in Germany and dual-frequency observations at C and S band in the United States are compared to explore the regional frequency dependencies of the δ signature. Theoretical simulations based on usual assumptions about the microphysical composition of the melting layer cannot reproduce the observed large values of δ at the lower-frequency bands and also underestimate the enhancements in differential reflectivity ZDR and reductions in the cross-correlation coefficient ρhυ. Simulations using a two-layer T-matrix code and a simple model for the representation of accretion can, however, explain the pronounced δ signatures at S and C bands in conjunction with small δ at X band. The authors conclude that the δ signature bears information about microphysical accretion and aggregation processes in the melting layer and the degree of riming of the snowflakes aloft.

scholarly journals Stratospheric ozone over the United States in summer linked to observations of convection and temperature via chlorine and bromine catalysis

2017 ◽  
Vol 114 (25) ◽  
pp. E4905-E4913 ◽  
Author(s):  
James G. Anderson ◽  
Debra K. Weisenstein ◽  
Kenneth P. Bowman ◽  
Cameron R. Homeyer ◽  
Jessica B. Smith ◽  
...  
Keyword(s):  
United States ◽  
Stratospheric Ozone ◽  
Reaction Network ◽  
The United States ◽  
The Arctic ◽  
Temperature Structure ◽  
Radar Observations ◽  
Ozone Loss ◽  
Heterogeneous Catalytic ◽  
The Impact

We present observations defining (i) the frequency and depth of convective penetration of water into the stratosphere over the United States in summer using the Next-Generation Radar system; (ii) the altitude-dependent distribution of inorganic chlorine established in the same coordinate system as the radar observations; (iii) the high resolution temperature structure in the stratosphere over the United States in summer that resolves spatial and structural variability, including the impact of gravity waves; and (iv) the resulting amplification in the catalytic loss rates of ozone for the dominant halogen, hydrogen, and nitrogen catalytic cycles. The weather radar observations of ∼2,000 storms, on average, each summer that reach the altitude of rapidly increasing available inorganic chlorine, coupled with observed temperatures, portend a risk of initiating rapid heterogeneous catalytic conversion of inorganic chlorine to free radical form on ubiquitous sulfate−water aerosols; this, in turn, engages the element of risk associated with ozone loss in the stratosphere over the central United States in summer based upon the same reaction network that reduces stratospheric ozone over the Arctic. The summertime development of the upper-level anticyclonic flow over the United States, driven by the North American Monsoon, provides a means of retaining convectively injected water, thereby extending the time for catalytic ozone loss over the Great Plains. Trusted decadal forecasts of UV dosage over the United States in summer require understanding the response of this dynamical and photochemical system to increased forcing of the climate by increasing levels of CO2and CH4.

scholarly journals A Simple and Effective Method for Separating Meteorological from Nonmeteorological Targets Using Dual-Polarization Data

2018 ◽  
Vol 35 (7) ◽  
pp. 1415-1424 ◽  
Author(s):  
Alamelu Kilambi ◽  
Frédéric Fabry ◽  
Véronique Meunier
Keyword(s):  
United States ◽  
The United States ◽  
False Alarms ◽  
Correct Identification ◽  
Test Cases ◽  
Depolarization Ratio ◽  
Dual Polarization ◽  
Polarization Data ◽  
Radar Systems ◽  
Differential Reflectivity

AbstractTo satisfy the needs of the meteorological and aeroecological communities wanting a simple but effective way of flagging each other’s unwanted echo for a variety of different operational radar systems, we evaluated the ability of an estimate of depolarization ratio (DR) based on differential reflectivity (ZDR) and copolar correlation coefficient (ρHV) measurements to separate both types of echoes. The method was tested with data collected by S- and C-band radars used in the United States and Canada. The DR-based method that does not require training achieved 96% separation between weather and biological echoes. Since the misclassifications are typically caused by isolated pixels in the melting layer or at the edge of echo patterns, the addition of a despeckling algorithm considerably reduces further these false alarms, resulting in an increase in correct identification approaching 99% on test cases.

scholarly journals Severe Hail Fall and Hailstorm Detection Using Remote Sensing Observations

2019 ◽  
Vol 58 (5) ◽  
pp. 947-970 ◽  
Author(s):  
Elisa M. Murillo ◽  
Cameron R. Homeyer
Keyword(s):  
United States ◽  
Real Time ◽  
Three Dimensional ◽  
The United States ◽  
Severe Weather ◽  
Dual Polarization ◽  
Spatiotemporal Resolution ◽  
Radar Observations ◽  
Radar Echo ◽  
Property Losses

AbstractSevere hail days account for the vast majority of severe weather–induced property losses in the United States each year. In the United States, real-time detection of severe storms is largely conducted using ground-based radar observations, mostly using the operational Next Generation Weather Radar network (NEXRAD), which provides three-dimensional information on the physics and dynamics of storms at ~5-min time intervals. Recent NEXRAD upgrades to higher resolution and to dual-polarization capabilities have provided improved hydrometeor discrimination in real time. New geostationary satellite platforms have also led to significant changes in observing capabilities over the United States beginning in 2016, with spatiotemporal resolution that is comparable to that of NEXRAD. Given these recent improvements, a thorough assessment of their ability to identify hailstorms and hail occurrence and to discriminate between hail sizes is needed. This study provides a comprehensive comparative analysis of existing observational radar and satellite products from more than 10 000 storms objectively identified via radar echo-top tracking and nearly 6000 hail reports during 30 recent severe weather days (2013–present). It is found that radar observations provide the most skillful discrimination between severe and nonsevere hailstorms and identification of individual hail occurrence. Single-polarization and dual-polarization radar observations perform similarly at these tasks, with the greatest skill found from combining both single- and dual-polarization metrics. In addition, revisions to the “maximum expected size of hail” (MESH) metric are proposed and are shown to improve spatiotemporal comparisons between reported hail sizes and radar-based estimates for the cases studied.

The Debate Over Multiple Glaciation in the United States: T.C. Chamberlin and G.F. Wright, 1889-1894

1983 ◽  
Vol 2 (2) ◽  
pp. 122-129
Author(s):  
Susan Schultz
Keyword(s):  
United States ◽  
Long Island ◽  
Ice Sheet ◽  
The United States ◽  
Glacial Period ◽  
Single Event ◽  
Terminal Moraine ◽  
The Public ◽  
The North ◽  
The University

In 1893 James D. Dana remarked that the concept of multiple glaciation had been advanced by midwestern geologists, while geologists who had done most of their fieldwork in the Northeast advocated a unified glacial period. Midwestern geologists interpreted the lobate terminal moraine ranging across much of the United States from Long Island to the Rockies as the boundary of the most recent ice sheet, and more southerly extramorainal drift as evidence of at least one earlier ice incursion, separated in time by a substantial, warmer interglacial interval or intervals, from the ice sheet that had deposited the terminal moraine. Geologists working east of Ohio, where the discrepancy between the terminal moraine and the extramorainal drift was less marked, tended to see the advance and retreat of the ice sheet as a single event, with minor oscillation and pauses of the ice front. The chief disputants in this debate were T. C. Chamberlin, professor of geology at the University of Chicago and head of the USGS Pleistocene Division, and G. Frederick Wright, former field geologist with the USGS and professor of theology at Oberlin College, but other prominent American geologists including Dana, W J McGee, R. D. Salisbury, Warren Upham, and Frank Leverett also took part. The debate was greatly enlivened by underlying motives much more complex than the midwestern versus northeastern division suggested by Dana. Among these less objective factors were personal animosities, Chamberlin's patronal attitude toward science and its presentation to the public, Wright's introduction of man into the North American Pleistocene, and resentment of a perceived arrogance on the part of government science.

Strategic Balance between India and Pakistan with respect to “Balance of Power Theory”

2020 ◽  
Vol 7 (12) ◽  
pp. 236-249
Author(s):  
Jaweriya Nasim ◽  
Khushboo Fatima ◽  
Sajida Noureen
Keyword(s):  
United States ◽  
South Asia ◽  
Nuclear Weapons ◽  
Balance Of Power ◽  
The United States ◽  
The Other ◽  
Single Event ◽  
Nuclear Program ◽  
Power Theory ◽  
Strategic Balance

India and Pakistan have strained relations since their independence because of serious conflicts like the Kashmir issue and major wars of 1965 and 1971. There is a continuous struggle for dominance among both the states through nuclear weapons and alliances with other nuclear weapons states, which have been addressed in this paper. India had made South Asia nuclear; to which Pakistan develop its nuclear program. Moreover, India and the United States growing relationship have further created an imbalance in the region. In return, Pakistan started strengthening its ties with China to counterbalance the Indian threat. This has been discussed in the paper that both states have actually created balance against one another in the context of the balance of power theory. But it is not going to be long lasting as there is a negative peace among them, and a single event can trigger a major conflict and depict dominance of one over the other.

The Attack on the US Capitol: An American Kristallnacht

Protest ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 126-141
Author(s):  
Jorge Heine
Keyword(s):  
United States ◽  
First Responders ◽  
The United States ◽  
War Of 1812 ◽  
Single Event ◽  
Donald Trump ◽  
Us Congress ◽  
The Us ◽  
Western Democracies

Abstract The attack on the US Capitol on 6 January 2021 was the first such attack on the US Congress since the British-American War of 1812. It was also the event leading to the highest number of injured first responders from any single event in the US since 9/11. What led to it? To respond this question, this article places this event within the broader crisis of Western democracies and the rise of populism that has been its hallmark. It explains the attack on the Capitol as a result of the “Big Lie”, that is, the assertion that the November 3, 2020, presidential elction was stolen from Donald Trump. The remarkable resonance this unfounded claim has found among the US population, in turn, can be traced back to the huge division by race, class and geography currently affecting the United States, a division that makes for a highly polarized polity.

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