The Microwave Limb Sounder on EOS-CHEM for Atmospheric Chemistry
The Microwave Limb Sounder for NASA's Earth Observing System.
microwave limb sounder Earth observation satellite↗
Engineering topics
Waters, J. W.
Publications and source records attributed to Waters, J. W..
UARS MLS Observations of Constitutent Variations (O3, ClO, HNO3) in the Extra-Vortical Lower Stratosphere
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Extra-Vortical Lower Stratosphere↗
UARS MLS observations of lower stratospheric ClO in the 1992-93 and 1993-94 Arctic winter vortices
Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS) measurements of lower stratospheric ClO during 1992-93 and 1993-94 Arctic winters are presented. Enhanced ClO in the 1992-93 winter was first observed in early December, and extensively during February when temperatures were continually low enough for polar stratospheric cloud (PSCs). Sporadic episodes of enhanced ClO were observed for most of the 1993-94 winter as minimum temperatures hovered near the PSC threshold, with largest ClO amounts occurring in early March after a sudden deep cooling in late February.
Waters, J. W.↗
UARS MLS Observations of Lower Stratospheric ClO in the 1992-93 and 1993-94 Arctic Winter Vortices
UARS (Upper Atmosphere Research Satellite) MLS (Microwave Limb Sounder) measurements of lower stratospheric ClO during the 1992-93 and 1993-94 Arctic winters are presented. Enhanced ClO in the 1992-93 winter was first observed in early December, and extensively during February when temperatures were continually low enough for PSCs. Sporadic episodes of enhanced ClO were observed for most of the 1993-94 winter as minimum temperatures hovered near the PSC threshold, with largest ClO amounts occurring in early March after a sudden deep cooling in late February.
Waters, J. W.↗
Evolution of microwave limb sounder ozone and the polar vortex during winter
The evolution of polar ozone observed by the Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS) is described for the northern hemisphere (NH) winters of 1991/1992, 1992/1993, and 1993/1994 and the southern hemisphere (SH) winters of 1992 and 1993. Imterannual and interhemispheric variability in polar ozone evolution are closely related to differences in the polar vortex and to the frequency, duration and strength of stratospheric sudden warmings. Ozone in the midstratospheric vortices increases during the winter, with largest increases associated with stratospheric warmings and a much larger increase in the NH than in the SH. A smaller NH increase was observed in 1993/1994, when the middle stratospheric vortex was stronger. During strong stratospheric warmings in the NH, the upper stratospheric vortex may be so much eroded that it presents little barrier to poleward transport; in contrast, the SH vortex remains strong throughout the stratosphere during wintertime warmings, and ozone increases only below the mixing ratio peak, due to enhanced diabatic descent. Ozone mixing ratios decrease rapidly in the lower stratosphere in both SH late winters, as expected from chemical destruction due to enhanced reactive chlorine. The interplay between dynamics and chemistry is more complex in the NH lower stratosphere and interannual variability is greater. Evidence has previously been shown for chemical ozone destruction in the 1991/1992 and 1992/1993 winters. We show here evidence suggesting some chemical destruction in late February and early March 1994. In the NH late winter lower stratosphere the pattern of high-ozone values (typical of the vortex) seen in mid-latitudes is related to the strength of the lower-stratospheric vortex, with the largest areal extent of high ozone outside the vortex in 1994, when the lower stratospheric vortex is relatively weak, and the least extent in 1993 when the lower stratospheric vortex is strongest.
Manney, G. L.↗
Interhemispheric differences in polar stratospheric HNO3, H2O, ClO, and O3
Simultaneous global measurements of nitric acid (HNO3), water (H2O), chlorine monoxide (ClO), and ozone (O3) in the stratosphere have been obtained over complete annual cycles in both hemispheres by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite. A sizeable decrease in gas-phase HNO3 was evident in the lower stratospheric vortex over Antarctica by early June 1992, followed by a significant reduction in gas-phase H2O after mid-July. By mid-August, near the time of peak ClO, abundances of gas-phase HNO3 and H2O were extremely low. The concentrations of HNO3 and H2O over Antarctica remained depressed into November, well after temperatures in the lower stratosphere had risen above the evaporation threshold for polar stratospheric clouds, implying that denitrification and dehydration had occurred. No large decreases in either gas-phase HNO3 or H2O were observed in the 1992-1993 Arctic winter vortex. Although ClO was enhanced over the Arctic as it was over the Antarctic, Arctic O3 depletion was substantially smaller than that over Antarctica. A major factor currently limiting the formation of an Arctic ozone 'hole' is the lack of denitrification in the northern polar vortex, but future cooling of the lower stratosphere could lead to more intense denitrification and consequently larger losses of Arctic ozone.
Santee, M. L.↗
Satellite Observations of Atmospheric Gravity Waves
The Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite produced the first global maps of small-scale gravity wave variances in the middle atmosphere. Observations at 30-88 km altitudes show that the variances of 30-100 km horizontal scales are strongly correlated with surface topography and stratospheric jet streams. The several years of MLS data will provide a climatology of global gravity wave activity needed for modeling atmospheric circulations and mixing processes.
atmospheric gravity waves middle atmosphere Microw↗
Arctic Ozone Depletion Observed by UARS MLS during the 1994-95 Winter
The Arctic lower stratosphere was unusually cold and the polar vortex
ozone↗
Evidence for Arctic Ozone Depletion in Late February and Early March 1994
Comparison of simulations of ozone transport using three-dimensional
ozone↗
Arctic Ozone Depletion Observed by UARS MLS During the 1994-95 Winter
The Earth's northern hemisphere lower stratosphere was unusually cold in December 1995 and January 1995. Temperatures low enough for polar stratospheric cloud formation persisted until mid-March 1995, and the polar vortex was exceptionally strong throughout the winter. Previous and current Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS) measurements indicating ozone depletion are given.
arctic↗
Three-dimensional evolution of water vapor distributions in the Northern Hemisphere stratosphere as observed by the MLS
The three-dimensional evolution of stratospheric water vapor distributions observed by the Microwave Limb Sounder (MLS) during the period October 1991 - July 1992 is documented. The transport features inferred from the MLS water vapor distributions are corroborated using other dynamical fields, namely, nitrous oxide from the Cryogenic Limb Array Etalon Spectrometer instrument, analyzed winds from the U.K. Meteorological Office (UKMO), UKMO-derived potential vorticity, and the diabatic heating field. By taking a vortex-centered view and an along-track view, the authors observe in great detail the vertical and horizontal structure of the northern winter stratosphere. It is demonstrated that the water vapor distributions show clear signatures of the effects of diabatic descent through isentropic surfaces and quasi-horizontal transport along isentropic surfaces, and that the large-scale winter flow is organized by the interaction between the westerly polar vortex and the Aleutian high.
Lahoz, W. A.↗
Spectral signatures of polar stratospheric clouds and sulfate aerosol
Multiwavelength observations of Antarctic and midlatitude aerosol by the Cryogenic Limb Array Etalon Spectrometer (CLAES) experiment on the Upper Atmosphere Research Satellite (UARS) are used to demonstrate a technique that identifies the location of polar stratospheric clouds. The technique discussed uses the normalized area of the triangle formed by the aerosol extinctions at 925, 1257, and 1605/cm (10.8, 8.0, and 6.2 micrometers) to derive a spectral aerosol measure M of the aerosol spectrum. Mie calculations for spherical particles and T-matrix calculations for spheriodal particles are used to generate theoretical spectral extinction curves for sulfate and polar stratospheric cloud particles. The values of the spectral aerosol measure M for the sulfate and polar stratospheric cloud particles are shown to be different. Aerosol extinction data, corresponding to temperatures between 180 and 220 K at a pressure of 46 hPa (near 21-km altitude) for 18 August 1992, are used to demonstrate the technique. Thermodynamic calculations, based upon frost-point calculations and laboratory phase-equilibrium studies of nitric acid trihydrate, are used to predict the location of nitric acid trihydrate cloud particles.
Massie, S. T.↗
The tropical semiannual oscillations in temperature and ozone as observed my the MLS
The first two years of Microwave Limb Sounder (MLS) temperature and ozone data are used to examine the tropical upper-stratospheric semiannual oscillation (SAO). Time series analysis revealed that the strongest amplitudes of the SAO occurred near the equator at 2 mb for temperature and 5 mb for ozone, consistent with previous observations. The first cycle of each calendar year was observed to have a much higher amplitude than the second cycle except for the warm phase in late 1991. Interannual variability in the strength of the SAO, such as the much stronger warm phase of late 1991 as compared to late 1992, was significant and could be partly attributed to the Quasi-Biennial Oscillation (QBO) in zonal wind.
Ray, Eric A.↗
UARS MILS O3 soundings compared with lidar measurements using the conservative coordinates reconstruction technique
A technique based on conservative properties of certain meteorological fields is used to compare ozone measurements from the Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite (UARS) with soundings from a lidar system operated at midlatitudes by the University of L'Aquila, Italy. A few typical cases are analyzed in connection with the position of the vortex relative to the observing station, and it is shown that in general lidar observations taken within the vortex compare well with the UARS data, regardless of whether they are coincident with a satellite overpass. It is shown that such analysis may be useful for comparing measurements of the same quantity taken at different sites using different measurement techniques.
Redaelli, G.↗
Column measurements of stratospheric trace species over Are, Sweden in the winter of 1991-1992
Total vertical column amounts of stratospheric HCl, HF, ClONO2 and HNO3 are reported from high resolution infrared solar absorption spectra taken during the European Arctic Stratospheric Ozone Experiment (EASOE) in the winter of 1991-1992. These ground based measurements were made near Are in North Sweden (63.4 deg N, 13.1 deg E) at an altitude of 800 m using a Fourier transform spectrometer and tunable diode laser heterodyne spectrometer. On 9th January 1992 the HCl vertical column dropped to 1.2 x 10(exp 15) molecules/sq cm from a November average of 3.6 x 10(exp 15) molecules/sq cm. The HCl drop occurred at a time when Are was below the polar vortex and the lower stratospheric ClO column above Are was elevated to approximately 2 x 10(exp 15) molecules/sq cm as measured by the Microwave Limb Sounder experiment on the Upper Atmosphere Research Satellite. These measurements indicate conversion of lower stratospheric chlorine from reservoir to chemically active forms.
Bell, W.↗
Low Ozone Anomalies in the Winter Middle Stratosphere
Microwave Limb Sounder observations of mid-stratospheric ozone during stratospheric warmings show tongues of high ozone drawn up from low latitudes into the developing anticyclone.
Microwave Limb Sounder ozone ozone anomalies middl↗
UARS MLS Observations of lower Stratospheric CIO n the 1992-93 and 1993-94 Arctic Winter Vortex
UARS MLS measurements of lower stratospheric CIO during the 1992-93 and 1993-94 Arctic winters are presented.
atmospheric research satellite↗
Chemical Depletion of Lower Stratospheric Ozone in the 1992-1993 Northern Winter Vortex
Satellite observations of ozone and chlorine monoxide in the Arctic lower stratosphere during winter 1992-1993 are compared with observations during other winters, observations of long-lived tracers and the evolution of the polar vortex. Chlorine in the lower stratospheric vortex during February 1993 was mostly in chemically reactive forms.
Arctic polar vortex↗