scholarly journals Altitude registration of limb-scattered radiation

2017 ◽  
Vol 10 (1) ◽  
pp. 167-178 ◽  
Author(s):  
Leslie Moy ◽  
Pawan K. Bhartia ◽  
Glen Jaross ◽  
Robert Loughman ◽  
Natalya Kramarova ◽  
...  
Keyword(s):  
Rayleigh Scattering ◽  
Polar Regions ◽  
Absolute Accuracy ◽  
Model Calculations ◽  
Ozone Monitoring ◽  
Time Periods ◽  
A New Technique ◽  
Tracking Devices ◽  
Absolute Altitude

Abstract. One of the largest constraints to the retrieval of accurate ozone profiles from UV backscatter limb sounding sensors is altitude registration. Two methods, the Rayleigh scattering attitude sensing (RSAS) and absolute radiance residual method (ARRM), are able to determine altitude registration to the accuracy necessary for long-term ozone monitoring. The methods compare model calculations of radiances to measured radiances and are independent of onboard tracking devices. RSAS determines absolute altitude errors, but, because the method is susceptible to aerosol interference, it is limited to latitudes and time periods with minimal aerosol contamination. ARRM, a new technique introduced in this paper, can be applied across all seasons and altitudes. However, it is only appropriate for relative altitude error estimates. The application of RSAS to Limb Profiler (LP) measurements from the Ozone Mapping and Profiler Suite (OMPS) on board the Suomi NPP (SNPP) satellite indicates tangent height (TH) errors greater than 1 km with an absolute accuracy of ±200 m. Results using ARRM indicate a ∼ 300 to 400 m intra-orbital TH change varying seasonally ±100 m, likely due to either errors in the spacecraft pointing or in the geopotential height (GPH) data that we use in our analysis. ARRM shows a change of ∼ 200 m over ∼ 5 years with a relative accuracy (a long-term accuracy) of ±100 m outside the polar regions.

scholarly journals Altitude Registration of Limb-Scattered Radiation

2016 ◽  
Author(s):  
Leslie Moy ◽  
P. K. Bhartia ◽  
Glen Jaross ◽  
Robert Loughman ◽  
Natalya Kramarova ◽  
...  
Keyword(s):  
Scattered Radiation ◽  
Focal Plane ◽  
Rayleigh Scattering ◽  
Model Calculations ◽  
Registration Error ◽  
Ozone Monitoring ◽  
Time Periods ◽  
Tracking Devices ◽  
Absolute Altitude

Abstract. One of the largest constraints to the retrieval of accurate ozone profiles from UV backscatter limb sounding sensors is altitude registration. Two methods, the Rayleigh Scattering Attitude Sensing (RSAS) and Absolute Radiance Residual Method (ARRM), have been developed to determine the altitude registration to the accuracy necessary for long-term ozone monitoring. The methods compare model calculations of radiances to measured radiances, and are independent of onboard tracking devices. RSAS determines absolute altitude errors, but because the method is susceptible to aerosol interference, it is limited to latitudes and time periods with minimal aerosols. ARRM can be applied across all seasons and altitudes. However, it is only appropriate for relative altitude error estimates. The application of these methods to Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (LP) measurements showed that, at launch, the OMPS LP instrument had a 1–2 km altitude registration error, resulting in a 50 % error in the derived ozone density at some altitudes. Though some of the error has been attributed to thermal shifts in the focal plane of the instrument, most of it appears to be due to misalignment of the spacecraft star trackers or the OMPS LP focal plane with respect to the spacecraft axes. In addition, there are ±200 m seasonally varying errors that could either be due to errors in the spacecraft pointing information or in the geopotential height (GPH) data that we use in our analysis.

scholarly journals The use of QBO, ENSO, and NAO perturbations in the evaluation of GOME-2 MetOp A total ozone measurements

2019 ◽  
Vol 12 (2) ◽  
pp. 987-1011
Author(s):  
Kostas Eleftheratos ◽  
Christos S. Zerefos ◽  
Dimitris S. Balis ◽  
Maria-Elissavet Koukouli ◽  
John Kapsomenakis ◽  
...  
Keyword(s):  
Satellite Data ◽  
Total Ozone ◽  
Southern Oscillation ◽  
Model Calculations ◽  
Ozone Data ◽  
Ozone Monitoring ◽  
Mean Differences ◽  
The Tropics ◽  
The Impact

Abstract. In this work we present evidence that quasi-cyclical perturbations in total ozone (quasi-biennial oscillation – QBO, El Niño–Southern Oscillation – ENSO, and North Atlantic Oscillation – NAO) can be used as independent proxies in evaluating Global Ozone Monitoring Experiment (GOME) 2 aboard MetOp A (GOME-2A) satellite total ozone data, using ground-based (GB) measurements, other satellite data, and chemical transport model calculations. The analysis is performed in the frame of the validation strategy on longer time scales within the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Satellite Application Facility on Atmospheric Composition Monitoring (AC SAF) project, covering the period 2007–2016. Comparison of GOME-2A total ozone with ground observations shows mean differences of about -0.7±1.4 % in the tropics (0–30∘), about +0.1±2.1 % in the mid-latitudes (30–60∘), and about +2.5±3.2 % and 0.0±4.3 % over the northern and southern high latitudes (60–80∘), respectively. In general, we find that GOME-2A total ozone data depict the QBO–ENSO–NAO natural fluctuations in concurrence with the co-located solar backscatter ultraviolet radiometer (SBUV), GOME-type Total Ozone Essential Climate Variable (GTO-ECV; composed of total ozone observations from GOME, SCIAMACHY – SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY, GOME-2A, and OMI – ozone monitoring instrument, combined into one homogeneous time series), and ground-based observations. Total ozone from GOME-2A is well correlated with the QBO (highest correlation in the tropics of +0.8) in agreement with SBUV, GTO-ECV, and GB data which also give the highest correlation in the tropics. The differences between deseazonalized GOME-2A and GB total ozone in the tropics are within ±1 %. These differences were tested further as to their correlations with the QBO. The differences had practically no QBO signal, providing an independent test of the stability of the long-term variability of the satellite data. Correlations between GOME-2A total ozone and the Southern Oscillation Index (SOI) were studied over the tropical Pacific Ocean after removing seasonal, QBO, and solar-cycle-related variability. Correlations between ozone and the SOI are on the order of +0.5, consistent with SBUV and GB observations. Differences between GOME-2A and GB measurements at the station of Samoa (American Samoa; 14.25∘ S, 170.6∘ W) are within ±1.9 %. We also studied the impact of the NAO on total ozone in the northern mid-latitudes in winter. We find very good agreement between GOME-2A and GB observations over Canada and Europe as to their NAO-related variability, with mean differences reaching the ±1 % levels. The agreement and small differences which were found between the independently produced total ozone datasets as to the influence of the QBO, ENSO, and NAO show the importance of these climatological proxies as additional tool for monitoring the long-term stability of satellite–ground-truth biases.

scholarly journals Ice processes and growth history on Arctic and sub-Arctic lakes using ERS-1 SAR data

Polar Record ◽  
1995 ◽  
Vol 31 (177) ◽  
pp. 115-128 ◽  
Author(s):  
K. Morris ◽  
M. O. Jeffries ◽  
W. F. Weeks
Keyword(s):  
Arctic Lakes ◽  
Polar Regions ◽  
Lake Ice ◽  
Sar Images ◽  
The North ◽  
Growth History ◽  
North Slope Of Alaska ◽  
Term Monitoring ◽  
Selection Of

AbstractA survey of ice growth and decay processes on a selection of shallow and deep sub-Arctic and Arctic lakes was conducted using radiometrically calibrated ERS-1 SAR images. Time series of radar backscatter data were compiled for selected sites on the lakes during the period of ice cover (September to June) for the years 1991–92 and 1992–93. A variety of lake-ice processes could be observed, and significant changes in backscatter occurred from the time of initial ice formation in autumn until the onset of the spring thaw. Backscatter also varied according to the location and depth of the lakes. The spatial and temporal changes in backscatter were most constant and predictable at the shallow lakes on the North Slope of Alaska. As a consequence, they represent the most promising sites for long-term monitoring and the detection of changes related to global warming and its effects on the polar regions.

A new technique for long-term recording of eye movements in infants

1976 ◽  
Vol 40 (1) ◽  
pp. 109-112 ◽  
Author(s):  
Ronald M Harper ◽  
Toke Hoppenbrouwers ◽  
S.A Ross
Keyword(s):  
Eye Movements ◽  
New Technique ◽  
A New Technique

Exercise and Osteoarthritis: Are We Stopping Too Early? Findings from the Clearwater Exercise Study

2006 ◽  
Vol 14 (2) ◽  
pp. 169-180 ◽  
Author(s):  
Frances V. Wilder ◽  
John P. Barrett ◽  
Edward J. Farina
Keyword(s):  
Clinical Trials ◽  
Knee Pain ◽  
Exercise Intervention ◽  
Pain Reduction ◽  
Optimal Length ◽  
Knee Oa ◽  
Pain Scores ◽  
Time Periods

The value of exercise for people with knee osteoarthritis (OA) receives continuing consideration. The optimal length of study follow-up time remains unclear. A group of individuals with knee OA participating in an exercise intervention was followed for 2 years. The authors quantified the change in knee-pain scores during Months 1–12 and during Months 13–24. Eleven individuals with radiographic knee OA and knee-pain scores of 2+ were evaluated. Pain scores were collected weekly from participants who exercised three times a week. Participants demonstrated pain reduction during both time periods. Pain reduction during Months 13–24, –10.7%, was slightly higher than pain reduction during Months 1–12, –7.8%. Among people with knee OA who exercise, these findings suggest that knee-pain amelioration continues beyond 12 months. Clinicians should consider encouraging long-term exercise programs for knee-OA patients. To best characterize the effect of exercise on knee pain, researchers designing clinical trials might want to lengthen the studies’ duration.

scholarly journals The GOME-2 instrument on the Metop series of satellites: instrument design, calibration, and level 1 data processing – an overview

2016 ◽  
Vol 9 (3) ◽  
pp. 1279-1301 ◽  
Author(s):  
Rosemary Munro ◽  
Rüdiger Lang ◽  
Dieter Klaes ◽  
Gabriele Poli ◽  
Christian Retscher ◽  
...  
Keyword(s):  
Data Processing ◽  
Instrument Design ◽  
Data Consistency ◽  
Current Status ◽  
Web Pages ◽  
Ozone Monitoring ◽  
Level 1 ◽  
Future Work ◽  
Ground Calibration

Abstract. The Global Ozone Monitoring Experiment-2 (GOME-2) flies on the Metop series of satellites, the space component of the EUMETSAT Polar System. In this paper we will provide an overview of the instrument design, the on-ground calibration and characterization activities, in-flight calibration, and level 0 to 1 data processing. The current status of the level 1 data is presented and points of specific relevance to users are highlighted. Long-term level 1 data consistency is also discussed and plans for future work are outlined. The information contained in this paper summarizes a large number of technical reports and related documents containing information that is not currently available in the published literature. These reports and documents are however made available on the EUMETSAT web pages and readers requiring more details than can be provided in this overview paper will find appropriate references at relevant points in the text.

scholarly journals Long-term accumulation and improvements in seismic event data for the polar regions by the International Seismological Centre

Polar Science ◽  
2015 ◽  
Vol 9 (1) ◽  
pp. 5-16 ◽  
Author(s):  
Dmitry A. Storchak ◽  
Masaki Kanao ◽  
Emily Delahaye ◽  
James Harris
Keyword(s):  
Seismic Event ◽  
Polar Regions ◽  
Event Data ◽  
International Seismological Centre

scholarly journals Investigations of long-term trends in the ionosphere with world-wide ionosonde observations*

2005 ◽  
Vol 2 ◽  
pp. 253-258 ◽  
Author(s):  
J. Bremer
Keyword(s):  
Data Series ◽  
Model Calculations ◽  
Maximum Electron Density ◽  
Model Predictions ◽  
Density Values ◽  
Long Term Trends ◽  
Experimental Values ◽  
The Individual ◽  
Global Mean

Abstract. Basing on model calculations by Roble and Dickinson (1989) for an increasing content of atmospheric greenhouse gases in the Earth’s atmosphere Rishbeth (1990) predicted a lowering of the ionospheric F2- and E-regions. Later Rishbeth and Roble (1992) also predicted characteristic longterm changes of the maximum electron density values of the ionospheric E-, F1-, and F2-layers. Long-term observations at more than 100 ionosonde stations have been analyzed to test these model predictions. In the E- and F1-layers the derived experimental results agree reasonably with the model trends (lowering of h'E and increase of ƒoE and ƒoF1, in the E-layer the experimental values are however markedly stronger than the model data). In the ionospheric F2-region the variability of the trends derived at the different individual stations for hmF2 as well as ƒoF2 values is too large to estimate reasonable global mean trends. The reason of the large differences between the individual trends is not quite clear. Strong dynamical effects may play an important role in the F2-region. But also inhomogeneous data series due to technical changes as well as changes in the evaluation algorithms used during the long observation periods may influence the trend analyses.

scholarly journals Ozone Monitoring Instrument spectral UV irradiance products: comparison with ground based measurements at an urban environment

2008 ◽  
Vol 8 (5) ◽  
pp. 17467-17493 ◽  
Author(s):  
S. Kazadzis ◽  
A. Bais ◽  
A. Arola ◽  
N. Krotkov ◽  
N. Kouremeti ◽  
...  
Keyword(s):  
Global Scale ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Ozone Monitoring Instrument ◽  
Model Calculations ◽  
Aerosol Absorption ◽  
Theoretical Approaches ◽  
Uv Irradiance ◽  
Ozone Monitoring ◽  
Comparison Period

Abstract. We have compared spectral ultraviolet overpass irradiances from the Ozone Monitoring Instruments (OMI) against ground-based Brewer measurements at Thessaloniki, Greece from September 2004 to December 2007. It is demonstrated that OMI overestimates UV irradiances by 30%, 17% and 13% for 305 nm, 324 nm, and 380 nm respectively and 20% for erythemally weighted irradiance. The bias between OMI and Brewer increases with increasing aerosol absorption optical thickness. We present methodologies that can be applied for correcting this bias based on experimental results derived from the comparison period and also theoretical approaches using radiative transfer model calculations. All correction approaches minimize the bias and the standard deviation of the ratio OMI versus Brewer ratio. According to the results, the best correction approach suggests that the OMI UV product has to be multiplied by a correction factor CA(λ) are in the order of 0.8, 0.88 and 0.9 for 305 nm, 324 nm and 380 nm respectively. Limitations and possibilities for applying such methodologies in a global scale are also discussed.

scholarly journals Mysteriously high Δ<sup>14</sup>C of the glacial atmosphere: Influence of <sup>14</sup>C production and carbon cycle changes

2020 ◽  
Author(s):  
Ashley Dinauer ◽  
Florian Adolphi ◽  
Fortunat Joos
Keyword(s):  
Carbon Cycle ◽  
Production Rate ◽  
Polar Regions ◽  
Computationally Efficient ◽  
Drastic Reduction ◽  
Qualitative And Quantitative ◽  
Time Period ◽  
Climate Simulations ◽  
The Last Glacial

Abstract. Despite intense focus on the ~ 190 permil drop in atmospheric Δ14C across the deglacial “mystery interval”, the specific mechanisms responsible for the apparent Δ14C excess in the glacial atmosphere have received considerably less attention. The computationally efficient Bern3D earth system model of intermediate complexity, designed for long-term climate simulations, allows us to address a very fundamental but still elusive question concerning the atmospheric Δ14C record: How can we explain the persistence of relatively high Δ14C values during the millennia after the Laschamp event? Large uncertainties in the pre-Holocene 14C production rate, as well as in the older portion of the Δ14C record, complicate our qualitative and quantitative interpretation of the glacial Δ14C elevation. Here we begin with sensitivity experiments that investigate the controls on atmospheric Δ14C in more idealized settings. We show that the long-term process of sedimentation may be much more important to the simulation of Δ14C than had been previously thought. In order to provide a bounded estimate of glacial Δ14C change, the Bern3D model was integrated with five available estimates of the 14C production rate as well as reconstructed and hypothesized paleoclimate forcing. Model results demonstrate that none of the available reconstructions of past changes in 14C production can reproduce the elevated Δ14C levels during the last glacial. In order to increase atmospheric Δ14C to glacial levels, a drastic reduction of air-sea exchange efficiency in the polar regions must be assumed, though discrepancies remain for the portion of the record younger than ~ 33 kyr BP. We end with an illustration of how the 14C production rate would have had to evolve to be consistent with the Δ14C record, by combining an atmospheric radiocarbon budget with the Bern3D model. The overall conclusion is that the remaining discrepancies with respect to glacial Δ14C may be linked to an underestimation of 14C production and/or a biased-high reconstruction of Δ14C over the time period of interest. Alternatively, we appear to still be missing an important carbon cycle process for atmospheric Δ14C.

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