28 research outputs found
Quantum Communication in 6G Satellite Networks: Entanglement Distribution Across Changing Topologies
As LEO/VLEO satellites offer many attractive features, such as low
transmission delay, they are expected to be an integral part of 6G. Global
entanglement distribution over LEO and VLEO satellites network must reckon with
satellite movement over time. Current studies do not fully capture the dynamic
nature of satellite constellations. We model a dynamic LEO/VLEO satellite
network as a time-varying graph and construct a sequence of static graphs to
represent a dynamic network. We study the entanglement distribution problem
between a set of source-destination node pairs in this dynamic network
utilizing Multi-commodity Flow (MCF). Solving MCF over a sequence of graphs
independently for each graph may produce a completely different set of paths.
Changing the set of paths every time the graph topology changes may involve a
significant amount of overhead, as an established set of paths must be taken
down and a new set of paths established. We propose a technique that will avoid
this overhead by computing only one set of paths P to be used over all the
graphs in the sequence. The degraded performance offered by P may be viewed as
the cost of using P. The benefit of using P is the overhead cost of path
switching that can be avoided. We provide a cost-benefit analysis in a LEO/VLEO
constellation for entanglement distribution between multiple source-destination
pairs. Our extensive experimentation shows that a significant amount of savings
in overhead can be achieved if one is willing to accept a slightly degraded
performance
STROZ Lidar Results at the MOHAVE III Campaign, October, 2009, Table Mountain, CA
During October, 2009 the GSFC STROZ Lidar participated in a campaign at the JPL Table Mountain Facility (Wrightwood, CA, 2285 m Elevation) to measure vertical profiles of water vapor from near the ground to the lower stratosphere. On eleven nights, water vapor, aerosol, temperature and ozone profiles were measured by the STROZ lidar, two other similar lidars, frost-point hygrometer sondes, and ground-based microwave instruments made measurements. Results from these measurements and an evaluation of the performance of the STROZ lidar during the campaign will be presented in this paper. The STROZ lidar was able to measure water vapor up to 13-14 km ASL during the campaign. We will present results from all the STROZ data products and comparisons with other instruments made. Implications for instrumental changes will be discussed
A New Differential Absorption Lidar to Measure Sub-Hourly Fluctuation of Tropospheric Ozone Profiles in the Baltimore - Washington D.C. Region
Tropospheric ozone profiles have been retrieved from the new ground based National Aeronautics and Space Administration (NASA) Goddard Space Flight Center TROPospheric OZone DIfferential Absorption Lidar (GSFC TROPOZ DIAL) in Greenbelt, MD (38.99 N, 76.84 W, 57 meters ASL) from 400 m to 12 km AGL. Current atmospheric satellite instruments cannot peer through the optically thick stratospheric ozone layer to remotely sense boundary layer tropospheric ozone. In order to monitor this lower ozone more effectively, the Tropospheric Ozone Lidar Network (TOLNet) has been developed, which currently consists of five stations across the US. The GSFC TROPOZ DIAL is based on the Differential Absorption Lidar (DIAL) technique, which currently detects two wavelengths, 289 and 299 nm. Ozone is absorbed more strongly at 289 nm than at 299 nm. The DIAL technique exploits this difference between the returned backscatter signals to obtain the ozone number density as a function of altitude. The transmitted wavelengths are generated by focusing the output of a quadrupled Nd:YAG laser beam (266 nm) into a pair of Raman cells, filled with high pressure hydrogen and deuterium. Stimulated Raman Scattering (SRS) within the focus generates a significant fraction of the pump energy at the first Stokes shift. With the knowledge of the ozone absorption coefficient at these two wavelengths, the range resolved number density can be derived. An interesting atmospheric case study involving the Stratospheric-Tropospheric Exchange (STE) of ozone is shown to emphasize the regional importance of this instrument as well as assessing the validation and calibration of data. The retrieval yields an uncertainty of 16-19 percent from 0-1.5 km, 10-18 percent from 1.5-3 km, and 11-25 percent from 3 km to 12 km. There are currently surface ozone measurements hourly and ozonesonde launches occasionally, but this system will be the first to make routine tropospheric ozone profile measurements in the Baltimore-Washington DC area
Measurements of Humidity in the Atmosphere and Validation Experiments (MOHAVE)-2009: overview of campaign operations and results
International audienceThe Measurements of Humidity in the Atmosphere and Validation Experiment (MOHAVE) 2009 campaign took place on 11-27 October 2009 at the JPL Table Mountain Facility in California (TMF). The main objectives of the campaign were to (1) validate the water vapor measurements of several instruments, including, three Raman lidars, two microwave radiometers, two Fourier-Transform spectrometers, and two GPS receivers (column water), (2) cover water vapor measurements from the ground to the mesopause without gaps, and (3) study upper tropospheric humidity variability at timescales varying from a few minutes to several days. A total of 58 radiosondes and 20 Frost-Point hygrometer sondes were launched. Two types of radiosondes were used during the campaign. Non negligible differences in the readings between the two radiosonde types used (Vaisala RS92 and InterMet iMet-1) made a small, but measurable impact on the derivation of water vapor mixing ratio by the Frost-Point hygrometers. As observed in previous campaigns, the RS92 humidity measurements remained within 5 % of the Frost-point in the lower and mid-troposphere, but were too dry in the upper troposphere. Over 270 h of water vapor measurements from three Raman lidars (JPL and GSFC) were compared to RS92, CFH, and NOAA-FPH. The JPL lidar profiles reached 20 km when integrated all night, and 15 km when integrated for 1 h. Excellent agreement between this lidar and the frost-point hygrometers was found throughout the measurement range, with only a 3 % (0.3 ppmv) mean wet bias for the lidar in the upper troposphere and lower stratosphere (UTLS). The other two lidars provided satisfactory results in the lower and mid-troposphere (2-5 % wet bias over the range 3-10 km), but suffered from contamination by fluorescence (wet bias ranging from 5 to 50 % between 10 km and 15 km), preventing their use as an independent measurement in the UTLS. The comparison between all available stratospheric sounders allowed to identify only the largest biases, in particular a 10 % dry bias of the Water Vapor Millimeter-wave Spectrometer compared to the Aura-Microwave Limb Sounder. No other large, or at least statistically significant, biases could be observed. Total Precipitable Water (TPW) measurements from six different co-located instruments were available. Several retrieval groups provided their own TPW retrievals, resulting in the comparison of 10 different datasets. Agreement within 7 % (0.7 mm) was found between all datasets. Such good agreement illustrates the maturity of these measurements and raises confidence levels for their use as an alternate or complementary source of calibration for the Raman lidars. Tropospheric and stratospheric ozone and temperature measurements were also available during the campaign. The water vapor and ozone lidar measurements, together with the advected potential vorticity results from the high-resolution transport model MIMOSA, allowed the identification and study of a deep stratospheric intrusion over TMF. These observations demonstrated the lidar strong potential for future long-term monitoring of water vapor in the UTLS
Taehwa Research Forest: a receptor site for severe domestic pollution events in Korea during 2016
During the May–June 2016 International
Cooperative Air Quality Field Study in Korea (KORUS-AQ), light synoptic
meteorological forcing facilitated Seoul metropolitan pollution outflow to
reach the remote Taehwa Research Forest (TRF) site and cause regulatory
exceedances of ozone on 24 days. Two of these severe pollution events are
thoroughly examined. The first, occurring on 17 May 2016, tracks
transboundary pollution transport exiting eastern China and the Yellow Sea,
traversing the Seoul Metropolitan Area (SMA), and then reaching TRF in the
afternoon hours with severely polluted conditions. This case study indicates
that although outflow from China and the Yellow Sea were elevated with
respect to chemically unperturbed conditions, the regulatory exceedance at
TRF was directly linked in time, space, and altitude to urban Seoul
emissions. The second case studied, which occurred on 9 June 2016, reveals that
increased levels of biogenic emissions, in combination with amplified urban
emissions, were associated with severe levels of pollution and a regulatory
exceedance at TRF. In summary, domestic emissions may be causing more
pollution than by transboundary pathways, which have been historically
believed to be the major source of air pollution in South Korea. The case
studies are assessed with multiple aircraft, model (photochemical and
meteorological) simulations, in situ chemical sampling, and extensive
ground-based profiling at TRF. These observations clearly identify TRF and
the surrounding rural communities as receptor sites for severe pollution
events associated with Seoul outflow, which will result in long-term
negative effects to both human health and agriculture in the affected areas.</p
Validation of the TOLNet lidars: the Southern California Ozone Observation Project (SCOOP)
The North America-based Tropospheric Ozone Lidar Network (TOLNet)
was recently established to provide high spatiotemporal vertical profiles of
ozone, to better understand physical processes driving tropospheric ozone
variability and to validate the tropospheric ozone measurements of upcoming
spaceborne missions such as Tropospheric Emissions: Monitoring Pollution
(TEMPO). The network currently comprises six tropospheric ozone lidars, four
of which are mobile instruments deploying to the field a few times per year,
based on campaign and science needs. In August 2016, all four mobile TOLNet
lidars were brought to the fixed TOLNet site of JPL Table Mountain Facility
for the 1-week-long Southern California Ozone Observation Project (SCOOP).
This intercomparison campaign, which included 400 h of lidar measurements
and 18 ozonesonde launches, allowed for the unprecedented simultaneous
validation of five of the six TOLNet lidars. For measurements between 3 and
10 km a.s.l., a mean difference of 0.7 ppbv (1.7 %), with a
root-mean-square deviation of 1.6 ppbv or 2.4 %, was found between the
lidars and ozonesondes, which is well within the combined uncertainties of
the two measurement techniques. The few minor differences identified were
typically associated with the known limitations of the lidars at the profile
altitude extremes (i.e., first 1 km above ground and at the instruments'
highest retrievable altitude). As part of a large homogenization and quality
control effort within the network, many aspects of the TOLNet in-house data
processing algorithms were also standardized and validated. This thorough
validation of both the measurements and retrievals builds confidence as to the
high quality and reliability of the TOLNet ozone lidar profiles for many
years to come, making TOLNet a valuable ground-based reference network for
tropospheric ozone profiling.</p
Myocyte membrane and microdomain modifications in diabetes: determinants of ischemic tolerance and cardioprotection
THE ORANGE BANDS OF SrO: PARTIAL ANALYSIS OF THE TRIPLET SYSTEM
Author Institution: Department of Physics, Penn State UniversityLaser induced flourescence studies of stontium monoxid in a Broida-type oven yield an analysis of several excited triplet states. SrO molecules are excited from the a state into two different states about above the ground state. Successive fluorescence into the ground state, the a state as well as the b state is observed. Using a least squares fit program, spectroscopic constants for these states were obtained. The parameters for the a state are in good agreement with those published by Field [1]. Beyond , the g state appears to be strongly perturbed. The main constants of the assigned states are (in ):[FIGURE] [1] R.W. Field, J. Chem. Phys., Vol. 60, 2400 (1974
Lidar Measurements of Stratospheric Ozone, Aerosols and Temperature during the SAUNA Campaign at Sodankyla, Finland
The Sodankyla Total Column Ozone Intercomparison (SAUNA) campaign took place at the Finnish Meteorological Institute Arctic Research Center (FMI-ARC) at Sodankyla, Finland (67.37 N) in two separate phases during early spring 2006, and winter 2007. These campaigns has several goals: to determine and improve the accuracy of total column ozone measurements during periods of low solar zenith angle and high total column ozone; to determine the effect of ozone profile shape on the total column retrieval; and to make validate satellite ozone measurements under these same conditions. The GSFC Stratospheric Ozone Lidar (STROZ), which makes profile measurements of ozone temperature, aerosols and water vapor participated in both phases of the campaign. During the deployments, more than 30 profile measurements were made by the lidar instrument, along with Dobson, Brewer, DOAS, ozonesonde, and satellite measurements. The presentation will concentrate on STROZ lidar results from the second phase of the campaign and comparisons with other instruments will be discussed. This will include both ground-based and satellite comparisons
Optimization of the GSFC TROPOZ DIAL retrieval using synthetic lidar returns and ozonesondes – Part 1: Algorithm validation
The main purpose of the NASA Goddard Space Flight Center TROPospheric OZone
DIfferential Absorption Lidar (GSFC TROPOZ DIAL) is to measure the vertical
distribution of tropospheric ozone for science investigations. Because of the
important health and climate impacts of tropospheric ozone, it is imperative
to quantify background photochemical ozone concentrations and ozone layers
aloft, especially during air quality episodes. For these reasons, this paper
addresses the necessary procedures to validate the TROPOZ retrieval algorithm
and confirm that it is properly representing ozone concentrations. This paper
is focused on ensuring the TROPOZ algorithm is properly quantifying ozone
concentrations, and a following paper will focus on a systematic uncertainty
analysis.
<br><br>
This methodology begins by simulating synthetic lidar returns from actual
TROPOZ lidar return signals in combination with a known ozone profile. From
these synthetic signals, it is possible to explicitly determine retrieval
algorithm biases from the known profile. This was then systematically
performed to identify any areas that need refinement for a new operational
version of the TROPOZ retrieval algorithm. One immediate outcome of this
exercise was that a bin registration error in the correction for detector
saturation within the original retrieval was discovered and was subsequently
corrected for. Another noticeable outcome was that the vertical smoothing in
the retrieval algorithm was upgraded from a constant vertical resolution to a
variable vertical resolution to yield a statistical uncertainty of
<10 %. This new and optimized vertical-resolution scheme retains the
ability to resolve fluctuations in the known ozone profile, but it now allows
near-field signals to be more appropriately smoothed. With these revisions to
the previous TROPOZ retrieval, the optimized TROPOZ retrieval algorithm
(TROPOZ<sub>opt</sub>) has been effective in retrieving nearly 200 m lower to
the surface. Also, as compared to the previous version of the retrieval, the
TROPOZ<sub>opt</sub> had an overall mean improvement of 3.5 %, and large
improvements (upwards of 10–15 % as compared to the previous algorithm)
were apparent between 4.5 and 9 km. Finally, to ensure the
TROPOZ<sub>opt</sub> retrieval algorithm is robust enough to handle actual
lidar return signals, a comparison is shown between four nearby ozonesonde
measurements. The ozonesondes are mostly within the TROPOZ<sub>opt</sub>
retrieval uncertainty bars, which implies that this exercise was quite
successful