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The Ground-Based Millimeter-wave Spectrometer (GBMS)

 

Stratospheric trace gases vertical profiles (see below for details).
Contact: giovanni.muscari@ingv.it

Period O3 CO N2O HNO3
13 Jan - 4 Mar, 2009
18 Jan 18 Feb, 2010
28 Jan - 7 Mar, 2011
27 Jan - 7 Mar, 2012
2 Feb - 12 Mar, 2014

Precipitable water vapor (PWV; see below for details).
Contact: giovanni.muscari@ingv.it

Period PWV
13 Jan - 4 Mar, 2009
18 Jan - 18 Feb, 2010
28 Jan - 7 Mar, 2011
27 Jan - 7 Mar, 2012
2 Feb - 12 Mar, 2014

Datasets Specifications.
The GBMS observes the pure rotational transition lines of O3 at 276.923 GHz, N2O at 276.328 GHz, CO at 230.538 GHz, and a compact cluster of HNO3 lines centered at 269.240 GHz. Ozone and CO spectra are measured with a 1.5-hour integration. About 3-4 hours of integration are needed for HNO3 and N2O lines, which are weaker than those of O3 and CO. Line deconvolutions for the retreval of concentration vertical profiles are performed by means of an Optimal Estimation algorithm. The uncertainties in the retrieved GBMS profiles are due to different sources: instrument calibration, data scaling, forward model parameters, measurements noise and smoothing errors.

GBMS O3
Retrievals show good sensitivity (> 80 %) to atmospheric variations (and can therefore be used for scientific purposes) between 17 and 80 km, where their 1σ uncertainty is estimated to be the larger of 11% or 0.2 ppmv [Muscari et al., 2012].

GBMS CO
Retrievals can be used for scientific purposes between 30 and 80 km, where their 1σ uncertainty is estimated to be the larger of 16% or 0.1 ppmv [de Zafra and Muscari, 2004; Di Biagio et al., 2010].

GBMS HNO3
Retrievals can be considered for scientific use between 17 and 45 km altitude, with a 1σ uncertainty that amounts to the larger of 15% or 0.2 ppbv. According to the Averaging Kernels the HNO3 retrieved profiles are most accurate and have the best resolution between 18 and 35 km. In this altitude range the retrieved profile vertical resolution (FWHM of the Averaging kernels) is about 12 km.

GBMS N2O
Retrievals can be used for scientific purposes between 18 and 35 km, where their 1σ uncertainty is estimated to be the larger of 16% or 0.1 ppmv [Di Biagio et al., 2010].

GBMS PWV
In the 230280 GHz spectral region the atmospheric emission arises almost entirely from water vapor continuum in cloud-free skies. The conversion from the atmospheric opacity TAUz (measured at the various frequencies where the GBMS is operated) to water vapor column content can hence be obtained by means of a linear relation: PWV = alpha (λ)*[TAUz(λ)-TAUdry(λ)].
At polar latitudes during winter, clear-sky conditions imply PWV < 4 mm, and this is the largest amount of water vapor that the GBMS can accurately measure. Uncertainties on GBMS PWV values are estimated by propagating the uncertainties on TAUz, on TAUdry, and the 1.9% error on alpha. This results in PWV uncertainties range from about 5% (for PWV = 4%) to about 10% (for the smallest PWVobserved, i.e., 0.5 mm) [Fiorucci et al., 2008].