Effects of polar stratospheric clouds in the Nimbus-7 LIMS version 6 data set Journal Article uri icon

Overview

abstract

  • Abstract. The historic Limb Infrared Monitor of the Stratosphere (LIMS) measurements of 1978–1979 from the Nimbus 7 satellite were re-processed with Version 6 (V6) algorithms and archived in 2002. The V6 dataset employs updated radiance registration methods, improved spectroscopic line parameters, and a common vertical resolution for all retrieved parameters. Retrieved profiles are spaced about every 1.6° of latitude along orbits and include the additional parameter of geopotential height. Profiles of O3 are sensitive to perturbations from emissions of polar stratospheric clouds (PSCs). This work presents results of implementing a first-order screening for effects of PSCs using simple algorithms based on vertical gradients of the O3 mixing ratio. Their occurrences are compared with the co-located, retrieved temperatures and related to the temperature thresholds needed for saturation of H2O and/or HNO3 vapor onto PSC particles. Observed daily locations where the major PSC screening criteria are satisfied are validated against PSCs observed with the Stratospheric Aerosol Monitor (SAM) II experiment also on Nimbus 7. Remnants of emissions from PSCs are characterized for O3 and HNO3 following the screening. PSCs may also impart a warm bias in the co-located LIMS temperatures, but by no more than 1–2 K at the altitudes of where effects of PSCs are a maximum in the ozone; thus, no PSC screening was applied to the V6 temperatures. Minimum temperatures vary between 187 K and 194 K and occur at or just above where the PSC effects are first identified in the ozone (most often between about 21 hPa to 28 hPa). Those temperature-pressure values are consistent with conditions for saturation and formation of supercooled ternary solution (STS) droplets and/or nitric acid trihydrate (NAT) aerosols. A temporary uptake of HNO3 vapor by about 2–3 ppbv is indicated in mid-January downwind of and at pressure-altitudes where effects of PSCs are found. Seven-month, time series of the distributions of LIMS O3 and HNO3 are shown based on their gridded Level 3 data following the screening. The zonal coefficients of both O3 and HNO3 are essentially free of effects from PSCs on the 550 K surface as averaged at equivalent latitudes. Remnants of PSCs are still present in O3 during mid-January on the 450 K surface. It is judged that the LIMS Level 3 data are of good quality for analyzing the larger-scale, stratospheric chemistry and transport processes during the Arctic winter of 1978–1979.;

publication date

  • April 7, 2016

has restriction

  • green

Date in CU Experts

  • January 7, 2021 6:07 AM

Full Author List

  • Remsberg E; Harvey VL

author count

  • 2

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