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Cavalieri D.J.,NASA | Markus T.,NASA | Hall D.K.,NASA | Ivanoff A.,ADNET Systems Inc. | Glick E.,Bryn Mawr College
IEEE Transactions on Geoscience and Remote Sensing | Year: 2010

An assessment of the standard Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) sea-ice concentrations for the Antarctic winter is made from a comparison of nearly 40000 AMSR-E sea-ice concentration values with geolocated sea-ice concentrations derived from ten Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) scenes acquired on October 1st and 2nd of 2005 and 2006. The standard AMSR-E sea-ice concentration products are produced using the National Aeronautics and Space Administration Team 2 sea-ice algorithm. The ten MODIS scenes cover portions of almost all the sea-ice regions surrounding the Antarctic continent. The AMSR-E averaged ice concentration biases relative to MODIS (AMSR-E minus MODIS) ranged from less than $-$0.5% to $-$ 18%, and the corresponding averaged root-mean-square (rms) errors ranged from 2% to 24%. One scene [October 1, 2006 (0550 UT)] had both the largest bias ($-$18%) and rms error (24%), whereas the other nine scenes had an average bias of $-$ 1.5% and an average rms error of 4.9%. The biases and rms errors are correlated with the fractions of new ice and open water. This is consistent with the findings that the largest errors in ice concentration derived from the AMSR-E occur in the marginal ice zone (MIZ) and along the ice edge and are likely caused by sea-ice flooding in the MIZ and new-ice production at the ice edge. © 2006 IEEE. Source


Thomason L.W.,NASA | Moore J.R.,Science Systems And Applications Inc. | Pitts M.C.,NASA | Zawodny J.M.,NASA | Chiou E.W.,ADNET Systems Inc.
Atmospheric Chemistry and Physics | Year: 2010

Herein, we provide an assessment of the data quality of Stratospheric Aerosol and Gas Experiment (SAGE∼III) Version 4 aerosol extinction coefficient and water vapor data products. The evaluation is based on comparisons with data from four instruments: SAGE II, the Polar Ozone and Aerosol Measurement (POAM III), the Halogen Occultation Experiment (HALOE), and the Microwave Limb Sounder (MLS). Since only about half of the SAGE III channels have a direct comparison with measurements by other instruments, we have employed some empirical techniques to evaluate measurements at some wavelengths. We find that the aerosol extinction coefficient measurements at 449, 520, 755, 869, and 1021 nm are reliable with accuracies and precisions on the order of 10% in the mission's primary aerosol target range of 15 to 25 km. We also believe this to be true of the aerosol measurements at 1545 nm though we cannot exclude some positive bias below 15 km. We recommend use of the 385 nm measurements above 16 km where the accuracy is on par with other aerosol channels. The 601 nm measurement is much noisier (∼20%) than other channels and we suggest caution in the use of these data. We believe that the 676 nm data are clearly defective particularly above 20 km (accuracy as poor as 50%) and the precision is also low (∼30%). We suggest excluding this channel under most circumstances. The SAGE III Version 4 water vapor data product appears to be high quality and is recommended for science applications in the stratosphere below 45 km. In this altitude range, the mean differences with all four corroborative data sets are no bigger than 15% and often less than 10% with exceptional agreement with POAM III and MLS. Above 45 km, it seems likely that SAGE III water vapor values are increasingly too large and should be used cautiously or avoided. We believe that SAGE III meets its preflight goal of 15% accuracy and 10% precision between 15 and 45 km. SAGE III water vapor data does not appear to be affected by aerosol loading in the stratosphere. Source


Thompson W.T.,ADNET Systems Inc.
Solar Physics | Year: 2013

Triangulation measurements using observations from the two Solar Terrestrial Relations Observatory (STEREO) spacecraft, combined with observations from the Solar Dynamics Observatory (SDO), are used to characterize the behavior of a prominence involved in two successive coronal mass ejections 6 - 7 December 2010. The STEREO separation at the time was 171. 6{ring operator}, which was functionally equivalent to a separation of 8. 4{ring operator}, and thus very favorable for feature co-identification above the limb. The first eruption at ≈ 14:16 UT on 6 December of the middle branch of the prominence starts off a series of magnetic reconfigurations in the right branch, which itself erupts at ≈ 2:06 UT the next day, about 12 hours after the first eruption. The cool prominence material seen at 304 Å drains back down to the surface, but a flux-rope-like magnetic structure is seen to erupt in both 195 Å by the STEREO/Extreme Ultraviolet Imager (EUVI), and in white light by the STEREO/COR1 inner coronagraph. In between the two eruptions, two different signs of helicity are seen in the measured twist of the right branch. This is interpreted to be caused by the overall prominence channel being composed of different segments with alternating helicity signs. The erupting parts on 6 and 7 December both show positive twist, but negative twist is seen in between these positive sections. Negative twist is consistent with the dextral chirality signs seen in the He ii line at 304 Å prior to both eruptions. However, during the period between the eruptions, a region of positive twist grows and replaces the region of negative twist, and finally erupts. We interpret these observations in the light of models that predict that helicity cancellation can be an important factor in the triggering of flares and coronal mass ejections. © 2013 Springer Science+Business Media Dordrecht. Source


Vourlidas A.,U.S. Navy | Howard R.A.,U.S. Navy | Esfandiari E.,ADNET Systems Inc. | Patsourakos S.,University of Ioannina | And 2 more authors.
Astrophysical Journal | Year: 2010

The LASCO coronagraphs, in continuous operation since 1995, have observed the evolution of the solar corona and coronal mass ejections (CMEs) over a full solar cycle with high-quality images and regular cadence. This is the first time that such a data set becomes available and constitutes a unique resource for the study of CMEs. In this paper, we present a comprehensive investigation of the solar cycle dependence on the CME mass and energy over a full solar cycle (1996-2009) including the first in-depth discussion of the mass and energy analysis methods and their associated errors. Our analysis provides several results worthy of further studies. It demonstrates the possible existence of two event classes: "normal" CMEs reaching constant mass for > 10 R⊙ and "pseudo"-CMEs which disappear in the C3 field of view. It shows that the mass and energy properties of CME reach constant levels and therefore should be measured only above ∼10 R⊙. The mass density (g/R⊙ 2) of CMEs varies relatively little (< order of magnitude) suggesting that the majority of the mass originates from a small range in coronal heights. We find a sudden reduction in the CME mass in mid-2003 which may be related to a change in the electron content of the large-scale corona and we uncover the presence of a 6 month periodicity in the ejected mass from 2003 onward. © 2010. The American Astronomical Society. All rights reserved. Printed in the U.S.A. Source


Moran T.G.,Catholic University of America | Moran T.G.,NASA | Davila J.M.,NASA | Thompson W.T.,ADNET Systems Inc.
Astrophysical Journal | Year: 2010

We have tested the validity of the coronal mass ejection (CME) polarimetric reconstruction technique for the first time using triangulation and demonstrated that it can provide the angle and distance of CMEs to the plane of the sky. In this study, we determined the three-dimensional orientation of the CMEs that occurred on 2007 August 21 and 2007 December 31 using polarimetric observations obtained simultaneously with the Solar Terrestrial Relations Observatory/Sun Earth Connection Coronal and Heliospheric Investigation spacecraft COR1-A and COR1-B coronagraphs. We obtained the CME orientations using both the triangulation and polarimetric techniques and found that angles to the sky plane yielded by the two methods agree to within ≈ 5°, validating the polarimetric reconstruction technique used to analyze CMEs observed with the Solar and Heliospheric Observatory/Large Angle Spectrometric Coronagraph. In addition, we located the CME source regions using EUV and magnetic field measurements and found that the corresponding mean angles to the sky plane of those regions agreed with those yielded by the geometric and polarimetric methods within uncertainties. Furthermore, we compared the locations provided by polarimetric COR1 analysis with those determined from other analyses using COR2 observations combined with geometric techniques and forward modeling. We found good agreement with those studies relying on geometric techniques but obtained results contradictory to those provided by forward modeling. © 2010. The American Astronomical Society. All rights reserved. Source

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