Engineering topics
Publications and source records attributed to Waters, J. W..
The first two years of MLS temperature and ozone data are used to examine the tropical upper stratospheric SAO. Time series analysis revealed the strongest amplitudes of the SAO to occur near the equator at 2 mb for temperature and 5 mb for ozone, consistent with previous observations.
This paper describes the validation of ozone data from the Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS). The MLS ozone retrievals are obtained from the calibrated microwave radiances (emission spectra) in two separate bands, at frequencies near 205 and 183 GHz.
The transport of passive tracers observed by UARS has been simulated using computed trajectories of thousands of air parcels initialized on a three-dimensional stratospheric grid. These trajectories are calculated in isentropic coordinates using horizontal winds provided by the United Kingdom Meteorological Office data assimilation system and vertical (cross-isentropic) velocities computed using a fast radiation code.
The severe depletion of stratospheric ozone over Antarctica in late winter and early spring is caused by enhanced CLO abundances arising from heterogeneous reactions on polar stratospheric clouds (PSCs). CLO abundances comparable to those over Antarctica have also been observed throughout the Arctic Vortex, but the accompanying loss of Arctic ozone has been much less severe.
The effect of early winter stratospheric minor warmings on the development of the polar vortex is discussed, for winters since the launch of the Upper Atmosphere Research Satellite (UARS).
The evolution of polar ozone observed by the Upper Atmosphere Research Satellite Microwave Limb Sounder 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. Ozone in the mid-stratospheric vortex increases over the winter, with largest increases associated with stratospheric warmings, and a much larger increase in the NH than in the SH.
Global ozone observations from the Microwave Limb Sounder (MLS) aboard the Upper Atmosphere Research Satellite (UARS) are presented, in both vertically resolved and column abundance formats.
Analysis of Upper Altmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS) observations in early January 1992 shows a clear relationship between predicted polar stratospheric cloud formation along the back trajectory and elevated ClO amounts. These findings are in good agreement with aircraft observations. The MLS observed variation of ClO amounts within the vortex also fits the pattern of ClO change as a result of air parcel solar exposure and nitric acid photolysis. Outside the polar vortex, the occasional highly elevated ClO appear statistically consistent with MLS measurement noise.
Variations in ozone and chlorine monoxide observed by the Microwave Limb Sounder (MLS) abroad the Upper Atmosphere Research Satellite (UARS) during the first two years of operation are presented. We focus on mid-latitudes, where significant ozone decreases are observed in the lower stratosphere, and we offer some comparisons with other data sets. We will attempt to place the mid-latitude changes in context with changes observed at other latitudes. Possible correlations between the MLS ozone and CIO observations will be discussed.
UARS MLS measurements of ClO in the 1992 Southern Hemisphere winter are described. Lower stratospheric ClO abundances greater than 1 ppbv were observed in the vortex beginning 1 June. The enhanced ClO reached largest areal extent in mid-August, then retreated poleward. ClO abundances at 22 hPa decreased in early September while those at 46 hPa remained high. O3 decrease within the vortex was observed by mid-August, and was coincident with the enhanced ClO.
The Microwave Limb Sounder observed waves in stratospheric temperature and O3 during the 1992 southern winter. Wave 1 intensifies three times from mid August through mid September, when a 9 day eastward traveling wave becomes in phase with the stationary wave 1. During the periods of wave intensification, minor sudden warmings and increased zonal mean O3 are observed. The waves have a westward phase tilt which results in an intensified baroclinic zone when the waves are in phase. Waves in T and O3 are positively correlated near 5 - 10 hPa, implying transport by planetary waves; this is supported by larger O3 wave amplitudes than expected from photochemistry alone.
The evolution of ozone (O3) observed by the Microwave Limb Sounder on board the Upper Atmosphere Research Satellite is described for 14 Aug through 20 Sep 1992, in relation to the polar vortex. The development of an ozone hole is observed in column O3, and a corresponding decrease is seen in O3 mixing ratio in the polar lower stratosphere, consistent with chemical destruction. The observations also suggest that poleward transport associated with episodes of strong planetary wave activity is important in increasing O3 in the mid-stratosphere.
The Microwave Limb Sounder (MLS) experiment on the Upper Atmosphere Research Satellite (UARS) began atmospheric measurements on September 19, 1991. Residual SO2 from the Pinatubo eruption was detected immediately after instrument activation. The SO2 was 1ocated in a tropical band with peak mixing ratios of about 15 ppbv near 26 km altitude. The observed decay of SO2 has provided an estimate of the OH concentration in the plume.
Concentrations of atmospheric ozone and of ClO (the predominant form of reactive chlorine responsible for stratospheric ozone depletion) are reported for both the Arctic and Antarctic winters of the past 18 months. Chlorine in the lower stratosphere was almost completely converted to chemically reactive forms in both the northern and southern polar winter vortices. This occurred in the south long before the development of the Antarctic ozone hole, suggesting that ozone loss can be masked by influx of ozone-rich air.
The Microwave Limb Sounder observed waves in stratospheric temperature and 03 during the 1992 southern winter.
A new remote sensing instrument, the Submillimeterwave Limb Sounder, has been developed to simultaneously measure ClO, HCl, O3 and HO2 from high altitude balloon and aircraft platforms. The instrument is a double sideband heterodyne radiometer measuring atmospheric thermal emission spectra near 640 GHz from the Earth's limb. The instrument was flown in April and October, 1991 and in February, 1992 on high altitude balloon platforms over the southwestern United States.
The vertical profiles of ClO, HCl, HO2, and O3 were determined from thermal emission measurements by a balloon-borne spectrometer operating near 640 GHz. Results are in broad agreement with previous measurements and models, but differ significantly with model photochemistry for the ratio of ClO to HCl.
Submillimeter-wavelength heterodyne spectroscopy by microwave limb sounding (MLS) from orbiting satellite is a measurement technique for studying Earth's stratosphere, mesosphere and lowerr thermosphere on a global scale. Development and deployment of such tools are timely, as stratospheric ozone shileds life from solar ultraviolet radiation but is depleted by pollution from industrial activities. MLS experiments on NASA's Upper Atmosphere Research Satellite (UARS) and Earth Observing System (EOS) are now being developed and implementend for global monitoring. Atmospheric thermal-emission spectra at millimeter and submillimeter wave-lengths are measured as the instrument field of view (FOV) is scanned through the limb from above. Atmospheric profiles of molecular abundances, temperature, pressure, wind and magnetic field can be determined from the measured emission spectra. Intensity of the emission can provide abundance and temperature. Measured linewidths, and emission from temperature-insensitive O2 lines, can provide pressure. Differentitaion of measured pressure with repsect ot measured height differential (obtaiend from the instrument FOV scan encoder) can also provide temperature through atmospheric hydrostatic equilibrium (which relates temperature to pressure and height differential). Doppler shifts of spectral lines can provide wind, and Zeeman splitting of the magnetic-dipole lines of O2 can provide magnetic field.