First Odin sub-mm retrievals in the tropical upper troposphere: humidity and cloud ice signals

Ekström, Mattias; Eriksson, Patrick; Rydberg, Bengt; Murtagh, Donal

doi:10.5194/acp-7-459-2007

Cited by 34 publications

(66 citation statements)

References 27 publications

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“…Most of the comparison has been performed on decadal averages of UTH data such that the impact of the wet bias is of minor influence on the results because the variability of UTH is very large in that region. Ekström et al (2007Ekström et al ( , 2008 compared RH ice values from ODIN (ODIN-SMR is a limb-sounder operating in the 500 GHz region) at 200 hPa with MOZAIC RH ice at 200 hPa for the period 2001-2004 over tropical regions. The agreement of the PDF for RH ice from ODIN and MOZAIC sensors is better than 5 % RH ice , which is within the retrieval error of ODIN.…”

Section: Discussionmentioning

confidence: 99%

“…In consequence, using re-analysed MOZAIC data for the intercomparison would suggest that ODIN-SMR shows a wet bias of about 10 % on a relative scale; see the PDF shown in Fig. 7 of Ekström et al (2007). In their consecutive study Ekström et al (2008) compared PDFs of RH ice measured by ODIN, AURA-MLS and UARS-MLS with MOZAIC UTH data optimised at 205 hPa; see Fig.…”

Section: Discussionmentioning

confidence: 99%

“…MOZAIC RH data were also used for the validation of satellite instruments (e.g. Offermann et al, 2002;Ekström et al, 2007Ekström et al, , 2008Heise et al, 2008), global chemistry transport models (e.g. Law et al, 2000;Crowther et al, 2002) and ECMWF models (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Technical Note: Reanalysis of upper troposphere humidity data from the MOZAIC programme for the period 1994 to 2009

et al. 2014

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Abstract. In situ observational data on the relative humidity (RH) in the upper troposphere and lowermost stratosphere (UT/LS), or tropopause region, collected aboard civil passenger aircraft in the MOZAIC (Measurements of OZone, water vapour, carbon monoxide and nitrogen oxides by in-service AIrbus airCraft) programme were reanalysed for the period 2000 to 2009. Previous analyses of probability distribution functions (PDFs) of upper troposphere humidity (UTH) data from MOZAIC observations from year 2000 and later indicated a bias of UTH data towards higher RH values compared to data of the period 1994 to 1999. As a result, the PDF of UTH data show a substantial fraction of observations above 100 % relative humidity with respect to liquid water. Such supersaturations, however, do not occur in the atmosphere because there is always a sufficient number of condensation nuclei available, that trigger condensation as soon as liquid saturation is slightly exceeded. An in-depth reanalysis of the data set identified a coding error in the calibration procedure from year 2000 on. The error did not affect earlier data from 1994 to 1999. The full data set for 2000-2009 was reanalysed applying the corrected calibration procedure. Applied correction schemes and a revised error analysis are presented along with the reanalysed PDF of relative humidity with respect to liquid water (RH liquid ) and ice (RH ice ).

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Technical Note: Reanalysis of upper troposphere humidity data from the MOZAIC programme for the period 1994 to 2009

et al. 2014

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“…Murtagh et al (2002) give an overview of Odin's atmospheric mission, and the performance of the SMR instrument regarding its standard stratospheric and mesospheric retrievals is summarised by Merino et al (2002). The measurements used for these retrievals and the most relevant technical details are presented in Ekström et al (2007) and Eriksson et al (2007). These two articles describe version 1 of the retrievals.…”

Section: Odin-smrmentioning

confidence: 99%

“…The errors of SMR relative humidity data are estimated and discussed in Ekström et al (2007) and Rydberg et al (2009). This is repeated for SMILES in Kasai et al (2014).…”

Section: Relative Humiditymentioning

confidence: 99%

Overview and sample applications of SMILES and Odin-SMR retrievals of upper tropospheric humidity and cloud ice mass

Eriksson

Rydberg²,

Sagawa

et al. 2014

Atmos. Chem. Phys.

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Abstract. Retrievals of cloud ice mass and humidity from the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) and the Odin-SMR (Sub-Millimetre Radiometer) limb sounder are presented and example applications of the data are given. SMILES data give an unprecedented view of the diurnal variation of cloud ice mass. Mean regional diurnal cycles are reported and compared to some global climate models. Some improvements in the models regarding diurnal timing and relative amplitude were noted, but the models' mean ice mass around 250 hPa is still low compared to the observations. The influence of the ENSO (El Niño-Southern Oscillation) state on the upper troposphere is demonstrated using 12 years of Odin-SMR data.The same retrieval scheme is applied for both sensors, and gives low systematic differences between the two data sets. A special feature of this Bayesian retrieval scheme, of Monte Carlo integration type, is that values are produced for all measurements but for some atmospheric states retrieved values only reflect a priori assumptions. However, this "allweather" capability allows a direct statistical comparison to model data, in contrast to many other satellite data sets. Another strength of the retrievals is the detailed treatment of "beam filling" that otherwise would cause large systematic biases for these passive cloud ice mass retrievals.The main retrieval inputs are spectra around 635/525 GHz from tangent altitudes below 8/9 km for SMILES/Odin-SMR, respectively. For both sensors, the data cover the upper troposphere between 30 • S and 30 • N. Humidity is reported as both relative humidity and volume mixing ratio. The vertical coverage of SMILES is restricted to a single layer, while Odin-SMR gives some profiling capability between 300 and 150 hPa. Ice mass is given as the partial ice water path above 260 hPa, but for Odin-SMR ice water content, estimates are also provided. Besides a smaller contrast between most dry and wet cases, the agreement with Aura MLS (Microwave Limb Sounder) humidity data is good. In terms of tropical mean humidity, all three data sets agree within 3.5 %RHi. Mean ice mass is about a factor of 2 lower compared to CloudSat. This deviation is caused by the fact that different particle size distributions are assumed, combined with saturation and a priori influences in the SMILES and Odin-SMR data.

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Retrieval of minor constituents in a cloudy atmosphere with remote-sensing millimetre-wave measurements

Bianco

Carli

Cecchi‐Pestellini

et al. 2007

Q.J.R. Meteorol. Soc.

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ABSTRACT:The presence of clouds in remote-sensing measurements is often the cause of information loss about the minor atmospheric constituent profiles that are the goal of the measurement. Millimetre-and submillimetre-wave sounding can be used to abate the problems of cloud contamination. A quantitative assessment of this possibility is provided with the systematic simulation of the retrieval of minor atmospheric constituents in the presence of ice cirrus clouds of different density and particle size. The simulations are made for the particular case of the MARSCHALS instrument which is a heterodyne limb-sounding spectrometer that measures the atmospheric thermal emission in the millimetre-and submillimetre-wave regions operating on board a stratospheric aircraft. Four types of measuring conditions are identified: clouds that do not modify the observation, clouds that are adequately described with an atmospheric continuum absorption model, clouds for which an error is introduced when the limited vertical resolution of the sounding does not resolve the sharp discontinuity of the cloud, and clouds which require the modelling of scattering effects for a correct retrieval. When a rigorous modelling of the cloud is performed, the retrieval of minor atmospheric constituent is marginally affected by the presence of the cloud. We find that in the worst case the cloud causes a loss, with respect to clear-sky conditions, of two degrees of freedom from about 90 and of 7% of information content relative to climatological information.

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First Odin sub-mm retrievals in the tropical upper troposphere: humidity and cloud ice signals

Cited by 34 publications

References 27 publications

Technical Note: Reanalysis of upper troposphere humidity data from the MOZAIC programme for the period 1994 to 2009

Technical Note: Reanalysis of upper troposphere humidity data from the MOZAIC programme for the period 1994 to 2009

Overview and sample applications of SMILES and Odin-SMR retrievals of upper tropospheric humidity and cloud ice mass

Retrieval of minor constituents in a cloudy atmosphere with remote-sensing millimetre-wave measurements

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