Ellis E. Remsberg

The Area of the Stratospheric Polar Vortex as a Diagnostic for Tracer Transport on an Isentropic Surface

Abstract Data retrieved from the LIMS (Limb lnfrared Monitor of the Stratosphere) experiment are used 10 calculate daily isentropic distributions of Ertels potential vorticity, ozone, water vapor and nitric acid at the 850 K level in the Northern Hemisphere stratosphere for the period 25 October 1978 through 2 April 1979. Systematic redistributions of the quasi-conservative tracers are investigated by following the evolutions of the horizontal projection of the areas enclosed by isopleths of tracer on the isentropic surface. If the horizontal velocity is nondivergent on an isentropic surface, the areas change in response to nonconservative processes and /or irreversible mixing to unresolvable scales and so provide a diagnostic for quantifying the net cited of these two processes. The effects of the seasonal variation of the solar heating on the areas are identified from the evolutions of the hemispheric means and, for the potential vorticity, from a comparison with an annual Mile integration of a zonally...

Stratospheric water vapor increases over the past half‐century

Ten data sets covering the period 1954–2000 are analyzed to show a 1%/yr increase in stratospheric water vapor. The trend has persisted for at least 45 years, hence is unlikely the result of a single event, but rather indicative of long-term climate change. A long-term change in the transport of water vapor into the stratosphere is the most probable cause.

The evolution of the stratopause during the 2006 major warming: Satellite data and assimilated meteorological analyses

Microwave Limb Sounder and Sounding of the Atmosphere with Broadband Emission Radiometry data provide the first opportunity to characterize the four-dimensional stratopause evolution throughout the life-cycle of a major stratospheric sudden warming (SSW). The polar stratopause, usually higher than that at midlatitudes, dropped by ∼30 km and warmed during development of a major “wave 1” SSW in January 2006, with accompanying mesospheric cooling. When the polar vortex broke down, the stratopause cooled and became ill-defined, with a nearly isothermal stratosphere. After the polar vortex started to recover in the upper stratosphere/lower mesosphere (USLM), a cool stratopause reformed above 75 km, then dropped and warmed; both the mesosphere above and the stratosphere below cooled at this time. The polar stratopause remained separated from that at midlatitudes across the core of the polar night jet. In the early stages of the SSW, the strongly tilted (westward with increasing altitude) polar vortex extended into the mesosphere, and enclosed a secondary temperature maximum extending westward and slightly equatorward from the highest altitude part of the polar stratopause over the cool stratopause near the vortex edge. The temperature evolution in the USLM resulted in strongly enhanced radiative cooling in the mesosphere during the recovery from the SSW, but significantly reduced radiative cooling in the upper stratosphere. Assimilated meteorological analyses from the European Centre for Medium-Range weather Forecasts (ECMWF) and Goddard Earth Observing System Version 5.0.1 (GEOS-5), which are not constrained by data at polar stratopause altitudes and have model tops near 80 km, could not capture the secondary temperature maximum or the high stratopause after the SSW; they also misrepresent polar temperature structure during and after the stratopause breakdown, leading to large biases in their radiative heating rates. ECMWF analyses represent the stratospheric temperature structure more accurately, suggesting a better representation of vertical motion; GEOS-5 analyses more faithfully describe stratopause level wind and wave amplitudes. The high-quality satellite temperature data used here provide the first daily, global, multiannual data sets suitable for assessing and, eventually, improving representation of the USLM in models and assimilation systems.

Transport of Ozone in the Middle Stratosphere: Evidence for Planetary Wave Breaking

Abstract Data from the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) for the period 25 October 1978–28 May 1979 are used in a descriptive study of ozone variations in the middle stratosphere. It is shown that the ozone distribution is strongly influenced by irreversible deformation associated with large amplitude planetary-scale waves. This process, which has been described by McIntyre and Palmer as planetary wave breaking, takes place throughout the 3–30 mb layer, and poleward transport of ozone within this layer occurs in narrow tongues drawn out of the tropics and subtropics in association with major and minor warming events. Thew events complement the zonal mean diabatic circulation in producing significant changes in the total column amount of ozone.

Ground‐based microwave observations of ozone in the upper stratosphere and mesosphere

A 9-month-long series of mesurements of ozone in the upper stratosphere and mesosphere is reported. The measurements are presented as monthly averages of profiles in blocks of roughly 20 min local time and as night-to-day ratios. An error analysis predicts accuracies of 5-26% for the monthly profiles and 2.5-9% for the ratios. The data are compared to historical data from Solar Mesosphere Explorer (SME) and limb infrared monitor of the stratosphere (LIMS), and it is shown how to remove the effect of different vertical resolution from the comparisons. The microwave data typically agree to better than 10% with SMF and nighttime LIMS ozone at all altitudes below the 0.1-mbar surface. Comparison of the microwave night-to-day ratio with the corresponding ratio from LIMS suggests that nonlocal thermodynamic equilibrium effects in the LIMS daytime data exceed 10% at all pressures less than or equal to 1 mbar.

Implications of the Stratospheric Water Vapor Distribution as Determined from the Nimbus 7 LIMS Experiment

Abstract The LIMS experiment on Nimbus 7 has provided new results on the stratospheric water vapor distribution. The data show 1) a latitudinal gradient with mixing ratios that increase by a factor of 2 from equator to ±60 degrees at 50 mb, 2) most of the time there is a fairly uniform mixing ratio of 5 ppmv at high latitudes, but more variation exists during winter, 3) a well-developed hygropause at low to midlatitudes of the lower stratosphere 4) a source region of water vapor in the upper stratosphere to lower mesosphere that is consistent with methane oxidation chemistry, at least within the uncertainties of the data, 5) an apparent zonal mean H2O distribution that is consistent with the circulation proposed by Brewer in 1949, and 6) a zonal mean distribution in the lower stratosphere that is consistent with the idea of quasi-isentropic transport by eddies in the meridional direction. Limits to the use of the data in the refinement of our understanding of the stratospheric water vapor budget are noted.

Observations of infrared radiative cooling in the thermosphere on daily to multiyear timescales from the TIMED/SABER instrument

16 17 Abstract. We present observations of the infrared radiative cooling by carbon dioxide (CO2) and 18 nitric oxide (NO) in Earths thermosphere. These data have been taken over a period of 7 years 19 by the SABER instrument on the NASA TIMED satellite and are the dominant radiative cooling 20 mechanisms for the thermosphere. From the SABER observations we derive vertical profiles of 21 radiative cooling rates (W m -3 ), radiative fluxes (W m -2 ), and radiated power (W). In the period 22 from January 2002 through January 2009 we observe a large decrease in the cooling rates, 23 fluxes, and power consistent with the declining phase of solar cycle 23. The power radiated by 24 NO during 2008 when the Sun exhibited few sunspots was nearly one order of magnitude 25 smaller than the peak power observed shortly after the mission began. Substantial short-term 26 variability in the infrared emissions is also observed throughout the entire mission duration. 27 Radiative cooling rates and radiative fluxes from NO exhibit fundamentally different latitude 28 dependence than do those from CO2, with the NO fluxes and cooling rates being largest at high 29 latitudes and polar regions. The cooling rates are shown to be derived relatively independent of 30 the collisional and radiative processes that drive the departure from local thermodynamic 31 equilibrium (LTE) in the CO2 15 μm and the NO 5.3 μm vibration-rotation bands. The observed 32

Ozone and temperature trends in the upper stratosphere at five stations of the Network for the Detection of Atmospheric Composition Change

Upper stratospheric ozone anomalies from the satellite-borne Solar Backscatter Ultra-Violet (SBUV), Stratospheric Aerosol and Gas Experiment II (SAGE II), Halogen Occultation Experiment (HALOE), Global Ozone Monitoring by Occultation of Stars (GOMOS), and Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instruments agree within 5% or better with ground-based data from lidars and microwave radiometers at five stations of the Network for the Detection of Atmospheric Composition Change (NDACC), from 45°S to 48°N. From 1979 until the late 1990s, all available data show a clear decline of ozone near 40 km, by 10%–15%. This decline has not continued in the last 10 years. At some sites, ozone at 40 km appears to have increased since 2000, consistent with the beginning decline of stratospheric chlorine. The phaseout of chlorofluorocarbons after the International Montreal Protocol in 1987 has been successful, and is now showing positive effects on ozone in the upper stratosphere. Temperature anomalies near 40 km altitude from European Centre for Medium Range Weather Forecast reanalyses (ERA-40), from National Centers for Environmental Prediction (NCEP) operational analyses, and from HALOE and lidar measurements show good consistency at the five stations, within about 3 K. Since about 1985, upper stratospheric temperatures have been fluctuating around a constant level at all five NDACC stations. This non-decline of upper stratospheric temperatures is a significant change from the more or less linear cooling of the upper stratosphere up until the mid-1990s, reported in previous trend assessments. It is also at odds with the almost linear 1 K per decade cooling simulated over the entire 1979–2010 period by chemistry–climate models (CCMs). The same CCM simulations, however, track the historical ozone anomalies quite well, including the change of ozone tendency in the late 1990s.

An intercomparison of model ozone deficits in the upper stratosphere and mesosphere from two data sets

We have compared a diurnal photochemical model of ozone with nighttime data from the limb infrared monitor of the stratosphere (LIMS) and ground-based microwave observations. Consistent with previous studies, the model underpredicts the observations by about 10–30%. This agreement is strong confirmation that the model ozone deficit is not simply an artifact of observational error since it is unlikely to occur for two completely different ozone data sets. We have also examined the seasonal, altitudinal, and diurnal morphology of the ozone deficit. Both comparisons show a deficit that peaks in the upper stratosphere (2–3 mbar) and goes through a minimum in the lower mesosphere from 1.0 to 0.4 mbar. At lower pressures (<0.2 mbar) the deficit appears to increase again. The seasonal variation of the deficit is less consistent. The deficit with respect to the LIMS data is least in winter while with respect to the microwave data, the deficit shows little seasonal variation. Finally, the night-to-day ratio in our model is in generally good agreement with that seen in the microwave experiment. Increasing the rate coefficient for the reaction O + O2 + M → O3 + M improves the fit, while a very large (50%) decrease in the HOx catalytic cycle is not consistent with our observations. Increasing the atomic oxygen recombination rate also improves the overall agreement with both data sets; however, a residual discrepancy still remains. There appears to be no single chemical parameter which, when modified, can simultaneously resolve both the stratospheric and mesospheric ozone deficits.

Analysis of differential absorption lidar from the Space Shuttle

A parametric analysis of the Shuttle-borne differential absorption lidar concept for the measurement of atmospheric trace constituent profiles in the nadir viewing mode is presented. The criterion of an optimum constituent optical depth is developed and applied to generate estimates of range resolved measurement errors. These errors emphasize the fundamental limitations for establishing the feasibility of range-resolved differential absorption lidar measurements from Shuttle. With current lidar system technology, atmospheric backscatter density profiles may be adequately determined up to about 60-km altitude at the doubled-ruby wavelength, 3472 A, for a 1-J/pulse laser and a 1-m(2) receiver. Potential range-resolved measurements of stratospheric and mesospheric trace constituents by differential absorption from Shuttle altitudes are limited to H(2)O, CH(4), N(2)O, O(3), and CO, species which can be more easily measured by passive limb viewing techniques. Range-resolved water vapor data for the lower troposphere may be obtained with accuracies which would be competitive with those from passive sensors. Technology advances in laser power and efficiency and in heterodyne detectors may allow other tropospheric species measurements from Shuttle in the future.