| 501. |
- Sheese, Patrick E., et al.
(författare)
-
Assessment of the quality of ACE-FTS stratospheric ozone data
- 2022
-
Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 15:5, s. 1233-1249
-
Tidskriftsartikel (refereegranskat)abstract
- For the past 17 years, the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) instrument on the Canadian SCISAT satellite has been measuring profiles of atmospheric ozone. The latest operational versions of the level 2 ozone data are versions 3.6 and 4.1. This study characterizes how both products compare with correlative data from other limb-sounding satellite instruments, namely MAESTRO, MLS, OSIRIS, SABER, and SMR. In general, v3.6, with respect to the other instruments, exhibits a smaller bias (which is on the order of similar to 3 %) in the middle stratosphere than v4.1 (similar to 2 %-9 %); however, the bias exhibited in the v4.1 data tends to be more stable, i.e. not changing significantly over time in any altitude region. In the lower stratosphere, v3.6 has a positive bias of about 3 %-5 % that is stable to within +/- 1 % per decade, and v4.1 has a bias on the order of -1 % to +5 % and is also stable to within +/- 1 % per decade. In the middle stratosphere, v3.6 has a positive bias of similar to 3 % with a significant negative drift on the order of 0.5 %-2.5 % per decade, and v4.1 has a positive bias of 2 %-9 % that is stable to within +/- 0.5 % per decade. In the upper stratosphere, v3.6 has a positive bias that increases with altitude up to similar to 16 % and a significant negative drift on the order of 2 %-3 % per decade, and v4.1 has a positive bias that increases with altitude up to similar to 15 % and is stable to within +/- 1 % per decade. Estimates indicate that both versions 3.6 and 4.1 have precision values on the order of 0.1-0.2 ppmv below 20 km and above 45 km (similar to 5 %-10 %, depending on altitude). Between 20 and 45 km, the estimated v3.6 precision of similar to 4 %-6 % is better than the estimated v4.1 precision of similar to 6 %-10 %.
|
|
| 502. |
- Toohey, M., et al.
(författare)
-
Characterizing sampling biases in the trace gas climatologies of the SPARC Data Initiative
- 2013
-
Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202 .- 2169-897X .- 2169-8996. ; 118:20, s. 11847-11862
-
Tidskriftsartikel (refereegranskat)abstract
- Monthly zonal mean climatologies of atmospheric measurements from satellite instruments can have biases due to the nonuniform sampling of the atmosphere by the instruments. We characterize potential sampling biases in stratospheric trace gas climatologies of the Stratospheric Processes and Their Role in Climate (SPARC) Data Initiative using chemical fields from a chemistry climate model simulation and sampling patterns from 16 satellite-borne instruments. The exercise is performed for the long-lived stratospheric trace gases O3 and H2O. Monthly sampling biases for O3 exceed 10% for many instruments in the high-latitude stratosphere and in the upper troposphere/lower stratosphere, while annual mean sampling biases reach values of up to 20% in the same regions for some instruments. Sampling biases for H2O are generally smaller than for O3, although still notable in the upper troposphere/lower stratosphere and Southern Hemisphere high latitudes. The most important mechanism leading to monthly sampling bias is nonuniform temporal sampling, i.e., the fact that for many instruments, monthly means are produced from measurements which span less than the full month in question. Similarly, annual mean sampling biases are well explained by nonuniformity in the month-to-month sampling by different instruments. Nonuniform sampling in latitude and longitude are shown to also lead to nonnegligible sampling biases, which are most relevant for climatologies which are otherwise free of biases due to nonuniform temporal sampling.
|
|
| 503. |
- Åkesson, Torsten, et al.
(författare)
-
Aging studies for the ATLAS Transition Radiation Tracker (TRT)
- 2003
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 515:1-2, s. 166-179
-
Konferensbidrag (refereegranskat)abstract
- A summary of the aging and material validation studies carried out for the ATLAS Transition Radiation Tracker (TRT) is presented. Particular emphasis is put on the different phenomena observed in straw tubes operating with the chosen Xe/CF4/CO2 mixture. The most serious effects observed are silicon deposition on the anode wire and damage of the anode wire gold plating. Etching phenomena and active radical effects are also discussed. With a careful choice of all materials and components, and with good control of the water contamination in the active gas, the ATLAS TRT will operate reliably for 10 years at the LHC design luminosity. To demonstrate this fully, more work is still needed on the gas system purification elements, in particular to understand their interplay with the active species containing fluorine created in the avalanche process under irradiation.
|
|
| 504. |
- Åkesson, Torsten, et al.
(författare)
-
Tracking performance of the transition radiation tracker prototype for the ATLAS experiment
- 2002
-
Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 485:3, s. 298-310
-
Tidskriftsartikel (refereegranskat)abstract
- A prototype of the Transition Radiation Tracker (TRT) for the ATLAS experiment at the CERN LHC has been built and tested at the CERN SPS. Detailed studies of the drift-time measurements, alignment technique, hit registration efficiency, track and momentum accuracy were performed. A coordinate measurement accuracy of 150 Pin for a single TRT drift tube and momentum resolution of 0.8% for 20 GeV pions in a 1.56 T magnetic field were achieved. The results obtained are in agreement with the expected tracking performance of the ATLAS TRT. (C) 2001 Published by Elsevier Science B.V.
|
|
