Mar 13 – 15, 2017
Université Pierre et Marie Curie, Paris
Europe/Paris timezone

Long-term stability of the SOMORA microwave radiometer ozone data record

Mar 13, 2017, 5:30 PM
1h 30m



Eliane Maillard Barras (MeteoSwiss)


The microwave radiometer (MWR) SOMORA, operated continuously since 2000 in the framework of the NDACC, is measuring ozone profiles from the stratosphere up to the lower mesosphere with a temporal resolution of 30 min to 1h, providing a dataset which suits to the investigation of the annual and seasonal fluctuations as well as of the diurnal variations of the stratospheric ozone profiles. The ozone volume mixing ratio profiles are retrieved by optimal estimation and a complete error characterization can be obtained on a profile per profile basis in the frame of the retrieval. Multi-instrument comparison analyses are essential to assess the long-term stability of data records by estimating the drift and the bias of instruments. The SOMORA ozone profile dataset has been compared to the profiles measured by the GROMOS MWR in Bern, and by satellites (MLS, MIPAS, HALOE, SCHIAMACHY, GOMOS). The long-term stability of the timeserie and the mean biases in function of time have been estimated. The data set has been homogenized accounting for system modifications in 2005 and 2009 and ensuring a constant measurement contribution to the retrieved ozone profiles up to 60 km. Comparisons of the most recent data revealed a positive anomaly of the SOMORA ozone measurements in 2015 and 2016. A calibration hot load issue in 2015 has been discovered, and the dataset has been reprocessed. Timeseries of ozone anomalies will be presented showing a clear improvement of the 2015 to 2016 consistency with the other ground-based instruments and with the satellites. Impact of the sampling on ozone trends has been investigated by deriving annual trends of hourly profiles. In the high stratosphere, diurnal trends and nocturnal trends show a significant difference while in the middle stratosphere, smaller differences between morning and afternoon trends are noticed.

Primary author

Eliane Maillard Barras (MeteoSwiss)


Alexander Haefele (MeteoSwiss) Dominique Ruffieux (MeteoSwiss)

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