Abstract
Abstract. This report describes the quality of the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) water vapor (H2O) profiles of 1978/79 that were processed with a Version 6 (V6) algorithm and archived in 2002. The V6 profiles incorporate a better knowledge of the instrument attitude for the LIMS measurements along its orbits, leading to improvements for its temperature profiles and for the registration of its water vapor radiances with pressure. As a result, the LIMS V6 zonal-mean distributions of H2O exhibit better hemispheric symmetry than was the case from the original Version 5 (V5) dataset that was archived in 1982. Estimates of the precision and accuracy of the V6 H2O profiles are developed and provided. Individual profiles have a precision of order 5% and an estimated accuracy of about 19% at 3 hPa, 14% at 10 hPa, and 26% at 50 hPa. Profile segments within about 2 km of the tropopause are often affected by emissions from clouds that appear in the finite field-of-view of the detector for the LIMS H2O channel. Zonally-averaged distributions of the LIMS V6 H2O are compared with those from the more recent Microwave Limb Sounder (MLS) satellite experiment for November, February, and May of 2004/05. The patterns and values of their respective distributions are similar in many respects. Effects of a strengthened Brewer-Dobson circulation are indicated in the MLS distributions of the recent decade versus those of LIMS from 1978/79. A tropical tape recorder signal is present in the 7-month time series of LIMS V6 H2O with lowest values in February 1979, and the estimated, annually-averaged "entry-level" H2O is 3.5 to 3.8 ppmv. It is judged that this historic LIMS water vapor dataset is of good quality for studies of the near global-scale chemistry and transport for pressure levels from 3 hPa to about 70 to 100 hPa.
Highlights
The Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) experiment operated successfully from 25 October 1978 through 28 May 1979, the planned lifetime of the onboard cryogen gases used to cool its detectors (Gille and Russell, 1984)
A major reason for the update of the overall LIMS algorithm to Version 6 (V6) is the incorporation of more recent spectroscopic line parameters for the retrievals of the LIMS profiles of temperature and each of its species, so that they are more compatible with the corresponding profile quantities obtained with the follow-on sensor systems of the Upper Atmosphere Research Satellite (UARS), of EOS Aura, and of the Environmental Satellite (ENVISAT) of the European Space Agency
The radiances of the Nimbus 7 LIMS experiment were reconditioned and new retrievals of them were conducted with a V6 algorithm to make its products more compatible with those of follow-on satellite experiments
Summary
The Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) experiment operated successfully from 25 October 1978 through 28 May 1979, the planned lifetime of the onboard cryogen gases used to cool its detectors (Gille and Russell, 1984). Chiou et al (1993, 1996) compared the LIMS V5 distributions with those from the Stratospheric Aerosol and Gas Experiment (SAGE II) of the Earth Radiation Budget Satellite (ERBS) and from the Stratospheric and Mesospheric Sounder (SAMS) instrument of Nimbus 7 They found general agreement among those three data sets, at least within their combined error bars. The precisions and accuracies for the LIMS V5 H2O profiles were reported in Russell et al (1984), Remsberg et al (1984a), and Remsberg and Russell (1987) Their combined errors are no greater than 17% in the middle stratosphere (3 to 30 hPa), due primarily to the effects of profile registration and temperature biases for their retrievals.
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