| 1. |
- Khosrawi, Farahnaz, et al.
(författare)
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Seasonal cycle of averages of nitrous oxide and ozone in the Northern and Southern Hemisphere polar, midlatitude, and tropical regions derived from ILAS/ILAS-II and Odin/SMR observations
- 2008
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 113:D18, s. D18305-
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Tidskriftsartikel (refereegranskat)abstract
- Northern and Southern Hemispheric monthly averages of ozone (O-3) and nitrous oxide (N2O) have been suggested as a tool for evaluating atmospheric photochemical models. An adequate data set for such an evaluation can be derived from measurements made by satellites which, in general, have a high spatial and temporal coverage. Here, we use measurements made by the Improved Limb Atmospheric Spectrometers (ILAS and ILAS-II) which use the solar occultation technique and by the Odin-Sub-Millimetre Radiometer (Odin/SMR) which passively observes thermal emissions from the Earth's limb. From ILAS/ILAS-II and Odin/SMR observations, 1-year data sets of monthly averaged O-3 and N2O, covering a full seasonal cycle, were derived for the latitude range between 60 - 90 degrees N and 60 - 90 degrees S, respectively, by partitioning the data into equal bins of altitude or potential temperature. A comparison between both data sets in this latitude region shows a good agreement and verifies that limited sampling from satellite occultation experiments does not constitute a problem for deriving such a full seasonal cycle of monthly averaged N2O and O-3. Since Odin/SMR provides measurements globally, a 1-year data set of monthly averaged N2O and O-3 is reported here for both the entire Northern and Southern Hemispheres from these measurements. Further, these hemispheric data sets from Odin/SMR are separated into data sets of monthly averaged N2O and O-3 for the low latitudes, midlatitudes, and high latitudes. The resulting families of curves help to differentiate between O-3 changes due to photochemistry from those due to transport. These 1-year hemispheric data sets of monthly averaged N2O and O-3 from Odin/SMR and ILAS/ILAS-II as well as the data sets of monthly averaged N2O and O-3 for the specific latitude regions from Odin/SMR provide a potentially important tool for the evaluation of atmospheric photochemical models. An example of how such an evaluation can be performed is given using data from two chemical transport models (CTMs), the Chemical Lagrangian Model of the Stratosphere (CLaMS) and the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA). We find a good agreement between Odin/SMR and the CTMs CLaMS and KASIMA with differences generally less than +/- 20%.
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| 2. |
- RÖSEVALL, JOHN, 1977, et al.
(författare)
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A study of ozone depletion in the 2004/2005 Arctic winter based on data from Odin/SMR and Aura/MLS
- 2008
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 113:D13
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Tidskriftsartikel (refereegranskat)abstract
- Ozone depletion in the colder than average 2004/2005 Arctic polar vortex is mapped and quantified using ozone profiles from two limb sounding satellite instruments, the Earth Observing System Microwave Limb Sounder (Aura/MLS) and the Odin Sub-Millimetre Radiometer (Odin/SMR). Profiles of chemically inert nitrous oxide (N(2)O) are used to trace vertical transport during the winter. Two methods are used for estimating the vortex average ozone losses north of 67 degrees equivalent latitude. In a first step, the time evolution of ozone mixing ratios is described on N(2)O isopleths. Maximum ozone depletion is found on the 100 ppbv and 150 ppbv N(2)O isopleths (located in the 430-460 K potential temperature range in mid-March 2005) where vortex average ozone depletion totalled 1.0-1.1 ppmv for Aura/MLS and 0.7-0.9 ppmv for Odin/SMR. Second, ozone profiles from Aura/MLS and Odin/SMR are assimilated into the DIAMOND isentropic transport model. Ozone depletion is estimated by comparing assimilated fields to ozone fields passively transported from 1 January. On the 450 K potential temperature level, the Aura/MLS ozone fields indicate 0.9-1.3 ppmv vortex-averaged ozone depletion while the Odin/SMR fields indicate 0.6-0.9 ppmv depletion. The uncertainty depends mainly on the rates of cross-isentropic transport used in the study. The ozone depletion estimates in this study are lower than previously published estimates. The discrepancies to some studies can be attributed to the more adequate treatment of an ozone poor region that is found in the central polar vortex in the early winter.
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| 3. |
- Santee, M.L., et al.
(författare)
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Validation of the Aura Microwave Limb Sounder ClO Measurements
- 2008
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 113:D15
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Tidskriftsartikel (refereegranskat)abstract
- We assess the quality of the version 2.2 (v2.2) ClO measurements from the Microwave Limb Sounder (MLS) on the Earth Observing System Aura satellite. The MLS v2.2 ClO data are scientifically useful over the range 100 to 1 hPa, with a single- profile precision of similar to 0.1 ppbv throughout most of the vertical domain. Vertical resolution is similar to 3-4 km. Comparisons with climatology and correlative measurements from a variety of different platforms indicate that both the amplitude and the altitude of the peak in the ClO profile in the upper stratosphere are well determined by MLS. The latitudinal and seasonal variations in the ClO distribution in the lower stratosphere are also well determined, but a substantial negative bias is present in both daytime and nighttime mixing ratios at retrieval levels below (i. e., pressures larger than) 22 hPa. Outside of the winter polar vortices, this negative bias can be eliminated by subtracting gridded or zonal mean nighttime values from the individual daytime measurements. In studies for which knowledge of lower stratospheric ClO mixing ratios inside the winter polar vortices to better than a few tenths of a ppbv is needed, however, day - night differences are not recommended and the negative bias must be corrected for by subtracting the estimated value of the bias from the individual measurements at each affected retrieval level.
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