A practical demonstration on AMSU retrieval precision for upper tropospheric humidity by a non-linear multi-channel regression method

Jiménez, Carlos; Eriksson, Patrick; John, Viju O.; Buehler, Stefan

doi:10.5194/acp-5-451-2005

Cited by 8 publications

(4 citation statements)

References 19 publications

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“…The bias is 0.4%RH and the retrieval error 6.1%RH. These values are consistent with the values given by Jimenez et al (2004) and Buehler and John (2005).…”

Section: Egusupporting

confidence: 92%

Retrieval of upper tropospheric water Retrieval of upper tropospheric water Retrieval of upper tropospheric water

Houshangpour¹,

John²,

Buehler³

2005

Preprint

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Abstract. A regression method was developed to retrieve upper tropospheric water vapor (UTWV in kg/m2) and upper tropospheric humidity (UTH in %RH) from radiances measured by the Advanced Microwave Sounding Unit (AMSU). In contrast to other UTH retrieval methods, UTH is defined as the average relative humidity between 500 and 200 hPa, not as a Jacobian weighted average, which has the advantage that the UTH altitude does not depend on the atmospheric conditions. The method uses AMSU channels 6–10, 18, and 19, and should achieve an accuracy of 0.48 kg/m2 for UTWV and 6.3%RH for UTH, according to a test against an independent synthetic data set. This performance was confirmed for northern mid-latitudes by a comparison against radiosonde data from station Lindenberg in Germany, which yielded errors of 0.23 kg/m2 for UTWV and 6.1%RH for UTH.

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“…The bias is 0.4%RH and the retrieval error 6.1%RH. These values are consistent with the values given by Jimenez et al (2004) and Buehler and John (2005).…”

Section: Egusupporting

confidence: 92%

Retrieval of upper tropospheric water Retrieval of upper tropospheric water Retrieval of upper tropospheric water

Houshangpour¹,

John²,

Buehler³

2005

Preprint

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“…In microwave and infrared frequency ranges, the radiative transfer physics is rather similar in clear air. Buehler and John [2005] and Jimenez et al [2005] thus retrieved the upper tropospheric humidity from B3 Tb in clear air. Can we therefore expect that both B3 and B5 be used to describe the humidity variability in our region of interest?…”

Section: Methodsmentioning

confidence: 99%

On the use of Advanced Microwave Sounding Unit‐A and ‐B measurements for studying the monsoon variability over West Africa

Eymard¹,

Karbou²,

Janicot³

et al. 2010

J. Geophys. Res.

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[1] The advanced microwave sounding unit (AMSU) -A and -B sensors provide observations of humidity and temperature that are relevant for meteorological and climate studies. The use of these observations in numerical weather prediction models has increased in the past 10 years because of some improvements in data assimilation. However, an appropriate use of AMSU measurements apart from assimilation context is rather difficult and depends for the most part on how successfully the instrumental characteristics are accounted for. In particular, atmosphere humidity and temperature variations can be completely hidden by features because of the effect of the observation zenith angle. In this paper, 8 years of AMSU-A and -B observations have been corrected from the observations zenith angle effect and have been used to study temperature and humidity variations over West Africa. Comparisons have been made between AMSU observations and selected atmospheric fields from European Centre for Medium-Range Weather Forecasts analyses as well as outgoing longwave radiation estimates. It has been found that observations from AMSU-A channel 5 can be used to monitor the heat low evolution and that AMSU-B observations from channels 3 and 5 are well adapted to study the humidity variations in direct link with the African monsoon from intraseasonal to interannual scales.

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“…Several authors [e.g., Rosenkranz , 2001; Jimenez et al , 2005] have demonstrated the possibility to retrieve humidity from AMSU‐B measurements. However, to our best knowledge there is no published study on the climatology of UTH from AMSU‐B measurements, and no publicly available AMSU based UTH data set.…”

Section: Introductionmentioning

confidence: 99%

An upper tropospheric humidity data set from operational satellite microwave data

et al. 2008

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[1] 183.31 GHz observations from the Advanced Microwave Sounding Unit B (AMSU-B) instruments onboard the NOAA 15, 16, and 17 satellites were used to derive a new data set of Upper Tropospheric Humidity (UTH). The data set consist of monthly median and mean data on a 1.5°latitude-longitude grid between 60°S and 60°N, and covers the time period of January 2000 to February 2007. The data from all three instruments are very consistent, with relative difference biases of less than 4% and relative difference standard deviations of 7%. Radiometric contributions by high ice clouds and by the Earth's surface affect the measurements in certain areas. The uncertainty due to clouds is estimated to be up to approximately 10%RH in areas with deep convection. The uncertainty associated with contamination from surface emission can exceed 10%RH in midlatitude winter, where the data therefore should be regarded with caution. Otherwise the surface influence appears negligible. The paper also discusses the UTH median climatology and seasonal cycle, which are found to be broadly consistent with UTH climatologies from other sensors. Finally, the paper presents an initial validation of the new data set against IR satellite data and radiosonde data. The observed biases of up to 9%RH (wet bias relative to HIRS) were found to be broadly consistent with expectations based on earlier studies. The observed standard deviations against all other data sets were below 6%RH. The UTH data are available to the scientific community on http://www.sat.ltu.se.

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A practical demonstration on AMSU retrieval precision for upper tropospheric humidity by a non-linear multi-channel regression method

Cited by 8 publications

References 19 publications

Retrieval of upper tropospheric water Retrieval of upper tropospheric water Retrieval of upper tropospheric water

Retrieval of upper tropospheric water Retrieval of upper tropospheric water Retrieval of upper tropospheric water

On the use of Advanced Microwave Sounding Unit‐A and ‐B measurements for studying the monsoon variability over West Africa

An upper tropospheric humidity data set from operational satellite microwave data

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