Interannual variability of the vertical descent rate in the Antarctic polar vortex

To investigate a descent rate in the Antarctic polar vortex, we analyzed the long-lived trace gas data derived from the Halogen Occultation Experiment on board the Upper Atmosphere Research Satellite during the 6-year period from 1992 to 1997. By comparing the Antarctic fall (February and March) and spring (September and October) methane profiles, we estimated the middle stratospheric descent for each of the six winters. Large year-to-year variations are seen (1.2–1.8 km month−1 at 0.6 ppmv), which consist of a biennial oscillation and a decreasing trend for the period analyzed. The descent rate is larger in the even years (1992, 1994, and 1996) than in the odd years (1993, 1995, and 1997). Dynamical fields for the 6 years are also analyzed using the United Kingdom Meteorological Office assimilation data. The differences between the even and odd years are clear in the midwinter. In the even years the downward and poleward movement of the westerly jet occurs earlier. The thermal wind relation infers that this event is associated with the development of a "warm pool" around the Antarctic stratopause, resulting from adiabatic heating due to the downward motion of air. Planetary wave activity over the winter season is more vigorous in the even years than in the odd years, suggesting a close relationship between the mean flow and planetary waves

Observational evidence and dynamical interpretation of the total ozone variations in the equatorial region

The total ozone amount is sensitive to the general circulation changes in the lower stratosphere due to the photochemically inactive nature of ozone there. In the equatorial region, such circulation changes arise from the quasi-biennial oscillation (QBO) of the stratospheric zonal wind and the El Nino/Southern Oscillation (ENSO). In the first half of this study we present observational results of the long-term variations in the equatorial ozone field using the 11 year Total Ozone Mapping Spectrometer (TOMS) data, by paying special attention to the longitudinal structure. In the latter half we try to understand quantitatively these variations by using a simple mechanistic relationship. We hypothesis that the ozone modulating processes are attributable to two dynamical effects, the advection effect and tropopause effect, owing to the strong vertical stratification of ozone existing just above the tropopause. The advection effect comes from the vertical motion which maintains the temperature structure, compensating for the radiative damping. The tropopause effect is associated with the altitude change of the tropopause. The total ozone variations in the tropics is discussed in terms of these two dynamical processes with the aid of mechanistic equations combined with the wind and sea surface temperature (SST) observations. The interactions between tropical and extratropical latitudes are beyond the scope of this study. Photochemical effects are also neglected. Details of this study are given by Shiotani (1992) and Hasebe (1992)

MIPAS observations of ozone in the middle atmosphere

This work is distributed under the Creative Commons Attribution 4.0 License.In this paper we describe the stratospheric and mesospheric ozone (version V5r-O3-m22) distributions retrieved from MIPAS observations in the three middle atmosphere modes (MA, NLC, and UA) taken with an unapodized spectral resolution of 0.0625 cm from 2005 until April 2012. O is retrieved from microwindows in the 14.8 and 10 μm spectral regions and requires non-local thermodynamic equilibrium (non-LTE) modelling of the O and vibrational levels. Ozone is reliably retrieved from 20 km in the MA mode (40 km for UA and NLC) up to ∼105 km during dark conditions and up to ∼95 km during illuminated conditions. Daytime MIPAS O has an average vertical resolution of 3-4 km below 70 km, 6-8 km at 70-80 km, 8-10 km at 80-90, and 5-7 km at the secondary maximum (90-100 km). For nighttime conditions, the vertical resolution is similar below 70 km and better in the upper mesosphere and lower thermosphere: 4-6 km at 70-100 km, 4-5 km at the secondary maximum, and 6-8 km at 100-105 km. The noise error for daytime conditions is typically smaller than 2% below 50 km, 2-10% between 50 and 70 km, 10-20% at 70-90 km, and ∼30% above 95 km. For nighttime, the noise errors are very similar below around 70 km but significantly smaller above, being 10-20% at 75-95 km, 20-30% at 95-100 km, and larger than 30% above 100 km. The additional major O errors are the spectroscopic data uncertainties below 50 km (10-12 %) and the non-LTE and temperature errors above 70 km. The validation performed suggests that the spectroscopic errors below 50 km, mainly caused by the O air-broadened half-widths of the band, are overestimated. The non-LTE error (including the uncertainty of atomic oxygen in nighttime) is relevant only above ∼85 km with values of 15-20 %. The temperature error varies from ∼3% up to 80 km to 15-20% near 100 km. Between 50 and 70 km, the pointing and spectroscopic errors are the dominant uncertainties. The validation performed in comparisons with SABER, GOMOS, MLS, SMILES, and ACE-FTS shows that MIPAS O has an accuracy better than 5% at and below 50 km, with a positive bias of a few percent. In the 50-75 km region, MIPAS O has a positive bias of ∼10 %, which is possibly caused in part by O spectroscopic errors in the 10 μm region. Between 75 and 90 km, MIPAS nighttime O is in agreement with other instruments by 10 %, but for daytime the agreement is slightly larger, ∼10-20 %. Above 90 km, MIPAS daytime O is in agreement with other instruments by 10 %. At night, however, it shows a positive bias increasing from 10% at 90 km to 20% at 95-100 km, the latter of which is attributed to the large atomic oxygen abundance used. We also present MIPAS O distributions as function of altitude, latitude, and time, showing the major O features in the middle and upper mesosphere. In addition to the rapid diurnal variation due to photochemistry, the data also show apparent signatures of the diurnal migrating tide during both day-and nighttime, as well as the effects of the semi-Annual oscillation above ∼70 km in the tropics and mid-latitudes. The tropical. daytime O at 90 km shows a solar signature in phase with the solar cycle. © Author(s) 2018.The IAA team was supported by the Spanish MICINN under the project ESP2014-54362-P and EC FEDER funds. The IAA and IMK teams were partially supported by ESA O3-CCI and MesosphEO projects. Maya Garcia-Comas was financially supported by MINECO through its >Ramon y Cajal> subprogram. Funding for the Atmospheric Chemistry Experiment comes primarily from the Canadian Space Agency. Work at the Jet Propulsion Laboratory was performed under contract with the National Aeronautics and Space Administration

Validation of ozone data from the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES)

The Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) onboard the International Space Station provided global measurements of ozone profiles in the middle atmosphere from 12 October 2009 to 21 April 2010. We present validation studies of the SMILES version 2.1 ozone product based on coincidence statistics with satellite observations and outputs of chemistry and transport models (CTMs). Comparisons of the stratospheric ozone with correlative data show agreements that are generally within 10%. In the mesosphere, the agreement is also good and better than 30% even at a high altitude of 73km, and the SMILES measurements with their local time coverage also capture the diurnal variability very well. The recommended altitude range for scientific use is from 16 to 73km. We note that the SMILES ozone values for altitude above 26km are smaller than some of the correlative satellite datasets; conversely the SMILES values in the lower stratosphere tend to be larger than correlative data, particularly in the tropics, with less than 8% difference below similar to 24km. The larger values in the lower stratosphere are probably due to departure of retrieval results between two detection bands at altitudes below 28km; it is similar to 3% at 24km and is increasing rapidly down below

Ozone in the Pacific tropical troposphere from ozonesonde observations

Ozone vertical profile measurements obtained from ozonesondes flown at Fiji, Samoa, Tahiti, and the Galapagos are used to characterize ozone in the troposphere over the tropical Pacific. There is a significant seasonal variation at each of these sites. At sites in both the eastern and western Pacific, ozone mixing ratios are greatest at almost all levels in the troposphere during the September‐November season and smallest during March‐May. The vertical profile has a relative maximum at all of the sites in the midtroposphere throughout the year (the largest amounts are usually found near the tropopause). This maximum is particularly pronounced during the September‐November season. On average, throughout the troposphere, the Galapagos has larger ozone amounts than the western Pacific sites. A trajectory climatology is used to identify the major flow regimes that are associated with the characteristic ozone behavior at various altitudes and seasons. The enhanced ozone seen in the midtroposphere during September‐November is associated with flow from the continents. In the western Pacific this flow is usually from southern Africa (although 10‐day trajectories do not always reach the continent) but also may come from Australia and Indonesia. In the Galapagos the ozone peak in the midtroposphere is seen in flow from the South American continent and particularly from northern Brazil. High ozone concentrations within potential source regions and flow characteristics associated with the ozone mixing ratio peaks seen in both the western and eastern Pacific suggest that these enhanced ozone mixing ratios result from biomass burning. In the upper troposphere, low ozone amounts are seen with flow that originates in the convective western Pacific

Annual, quasi-biennial, and El Niño-Southern Oscillation (ENSO)time-scale variations in equatorial total ozone

Equatorial total ozone variations with time scales of annual, quasi-biennial, and about 4-year periodicities are described by paying attention to their longitudinal structure. Analyses are made for 11 years from 1979 to 1989, using the global total ozone data derived from the total ozone mapping spectrometer on board the Nimbus 7 satellite. Over the equator an annual cycle in total ozone is conspicuous. Zonal mean values are maximum around September and minimum around January. The longitudinal structure shows a zonal wavenumber 1 pattern with minimum values around 140°E to the date line all year-round, indicating a close relationship to a region where the convective cloud activity is vigorous. By removing the climatological annual cycle from the original data, there appears the quasi-biennial oscillation in total ozone. This variation is characterized by zonally uniform phase changes and is strongly coupled with the quasi-biennial oscillation of the equatorial zonal wind in the lower stratosphere. Moreover, subtracting zonal mean values from the anomaly data mentioned above, we see an east-west seesaw variation with a nodal longitude around the date line. This east-west variation, having a characteristic time scale of about 4 years, is clearly related to the El Niño and the Southern Oscillation cycle. During El Niño events the longitudinal anomaly field in total ozone is positive in the western Pacific and negative in the eastern Pacific; the anomaly pattern is reversed during anti-El Niño events. Because the active region of convective clouds is located relatively in the eastern Pacific sector during El Niño events, it is suggested that the stronger upwelling and the higher tropopause associated with the convective cloud activity bring about less total ozone

Seasonal and interannual variability in the temperature structure around the tropical tropopause and its relationship with convective activities

Seasonal and interannual variability in the tropical tropopause temperatures and its relationship with convective activities are examined by using the ECMWF 40 year reanalysis data and NOAA/OLR data. Low temperatures generally occur over the equator in the eastern hemisphere and extend northwestward and southwestward in the subtropics to form a horseshoe-shaped structure. Because this structure resembles a stationary wave response known as the Matsuno-Gill pattern, which is a superposition of the Rossby and Kelvin responses, the two preliminary indices are defined to represent the two responses. The horseshoe-shaped structure index is then calculated from the two indices. The seasonal cycle in the horseshoe-shaped structure index is significantly related to that observed in convective activities adjacent to three monsoon regions: the South Asian monsoon (SoAM) and the North Pacific monsoon (NPM) areas during the northern summer and the Australian monsoon (AUM) area during the southern summer. The convective activities in the SoAM and NPM areas individually influence the horseshoe-shaped structure. During the northern summer, interannual variation in the horseshoe-shaped structure index in the NPM area is related to that observed in convective activities associated with the El Niño–Southern Oscillation (ENSO) cycle with about a half-year time lag. In the SoAM area, the variation is mainly controlled by isolated high temperatures, which are surrounded by the horseshoe-shaped temperature structures and are not related to convective activities. During the southern summer, the horseshoe-shaped structure index is related to convective anomalies associated with the ENSO cycle, shifting eastward in El Niño years

Stratospheric ozone variations in the equatorial region as seen in Stratospheric Aerosol and Gas Experiment data

An analysis is made of equatorial ozone variations for 5 years, 1984–1989, using the ozone profile data derived from the Stratospheric Aerosol and Gas Experiment II (SAGE II) instrument. Attention is focused on the annual cycle and also on interannual variability, particularly the quasi-biennial oscillation (QBO) and El Niño-Southern Oscillation (ENSO) variations in the lower stratosphere, where the largest contribution to total column ozone takes place. The annual variation in zonal mean total ozone around the equator is composed of symmetric and asymmetric modes with respect to the equator, with maximum contributions being around 19 km for the symmetric mode and around 25 km for the asymmetric mode. The persistent zonal wavenumber 1 structure observed by the total ozone mapping spectrometer over the equator is almost missing in the SAGE-derived column amounts integrated in the stratosphere, suggesting a significant contribution from tropospheric ozone. Interannual variations in the equatorial ozone are dominated by the QBO above 20 km and the ENSO-related variation below 20 km. The ozone QBO is characterized by zonally uniform phase changes in association with the zonal wind QBO in the equatorial lower stratosphere. The ENSO-related ozone variation consists of both the east-west vacillation and the zonally uniform phase variation. During the El Niño event, the east-west contrast with positive (negative) deviations in the eastern (western) hemisphere is conspicuous, while the decreasing tendency of the zonal mean values is maximum at the same time