Search NASA⌕ Search

SEARCH · Search NASA

Results for “QBO”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Studies of dynamical processes affecting the distribution of stratospheric ozone

The purpose of the research was to understand large-scale tracer transport processes in the stratosphere. Two approaches were taken. The first is analysis of tracer observations, especially satellite observations of ozone concentration and total column ozone. The second is numerical simulation of tracer transport processes. Topics researched include: quasi-biennial oscillation (QBO) and stratospheric ozone; mixing in the polar vortices; polar stratospheric clouds (PSC) properties from Antarctic lidar data; and statistical methods for numerical experiments.

Bowman, Kenneth P.↗
NASA NTRS1994

Trend analysis of the long-term Swiss ozone measurements

Trend analyses, assuming a linear trend which started at 1970, were performed from total ozone measurements from Arosa (Switzerland, 1926-1991). Decreases in monthly mean values were statistically significant for October through April showing decreases of about 2.0-4 percent per decade. For the period 1947-91, total ozone trends were further investigated using a multiple regression model. Temperature of a mountain peak in Switzerland (Mt. Santis), the F10.7 solar flux series, the QBO series (quasi biennial oscillation), and the southern oscillation index (SOI) were included as explanatory variables. Trends in the monthly mean values were statistically significant for December through April. The same multiple regression model was applied to investigate the ozone trends at various altitudes using the ozone balloon soundings from Payerne (1967-1989) and the Umkehr measurements from Arosa (1947-1989). The results show four different vertical trend regimes: On a relative scale changes were largest in the troposphere (increase of about 10 percent per decade). On an absolute scale the largest trends were obtained in the lower stratosphere (decrease of approximately 6 per decade at an altitude of about 18 to 22 km). No significant trends were observed at approximately 30 km, whereas stratospheric ozone decreased in the upper stratosphere.

Staehelin, Johannes↗
NASA NTRS1994

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).

Shiotani, Masato↗
NASA NTRS1994

Kelvin waves in total column ozone

Tropical Kelvin waves have been observed previously in ozone mixing ratio data from the SBUV (Solar Backscatter Ultraviolet) and LIMS (Limb Infrared Monitor of the Stratosphere) instruments on board the Nimbus-7 satellite. The present study investigates Kelvin wave features in total column ozone, using version 6 data from the Total Ozone Mapping Spectrometer (TOMS) instrument (also on Nimbus-7). Results show eastward-propagating zonal waves 1-2 with periods approx. 5-15 days, amplitudes approx. 3-5 Dobson Units (1-2% of the time mean), and latitudinal symmetry typical of Kelvin waves. The analyses and a linear model in this study suggest that the primary source of the perturbations is slow Kelvin waves in the lower-to-middle stratosphere. Maximum Kelvin wave signatures occur in conjunction with westward lower-to-middle stratospheric equatorial zonal winds (a quasi-biennial oscillation (QBO) wind modulation effect). The significance of these results is that the TOMS data are shown to be useful for investigations with global coverage of a major component of tropical stratospheric dynamics, Kelvin waves. The TOMS data set with its excellent coverage and high quality should be useful in validating model studies in the relatively data sparse and dynamically difficult tropical region.

Ziemke, J. R.↗
NASA NTRS1994

Coupling between middle atmosphere trend estimates and solar effects in ozone vertical structure

Studies are performed on both the Stratospheric Aerosol and Gas Experiment (SAGE) II (1985-1989) and Solar Backscatter Ultraviolet Spectrometer (SBUV)-Version 6 (1979-1986) global ozone vertical structure satellite data sets to determine the long-term trends in ozone as a function of altitude (pressure) and latitude. SAGE II data are only available during the period of increasing solar activity and show increases in ozone with time in the upper stratosphere which are attributed largely to rising solar activity. Looking at this data set independently, the solar effects and trends are highly coupled and cannot be clearly separated. However, a study of combined SBUV and SAGE II data over the 11-year solar cycle shows a clear response of ozone to 11-year solar variations and allows a decoupling of solar effects, quasibiennial oscillations (QBO), and trends. The detailed pattern of long-term ozone trends become clear using this approach. In the upper stratosphere, ozone depletion increases sharply with latitude. Global trends are fairly symmetric about the equator but are somewhat stronger in the Southern Hemisphere. Near the equator, some layers of ozone are decreasing with time while others appear to be increasing. Near 30 mb, there is evidence of intrusion to mid latitudes of high latitude negative trends. Near 15 mb, trends appear to be very weak. Near the tropopause there appears to be strong ozone depletion on a global scale. Two regions of unexpectedly strong ozone response to 11-year solar variations were detected: the first near 2 mb and the second near 30 mb at low latitudes and near 15 mb at mid latitudes.

Keating, G. M.↗
NASA NTRS1994

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.↗
NASA NTRS1993

Observation of 3-6 day meridional wind oscillations over the tropical Pacific, 1973-1992: Vertical structure and interannual variability

Rawinsonde data from tropical Pacific stations were examined for westward-propagating 3-6-day meridional wind oscillations in the troposphere and lower stratosphere, 1973-1992. Four types were identified from cross-spectrum and principal component analysis. (1) The dominant oscillation, near 250 mb, had a period slightly greater than 5 days, zonal wavenumber 4-6, and modified Rossby-gravity structure near the date line. (2) In the western Pacific lower troposphere there was broadband activity with short zonal scale, coupled to upper-tropospheric waves in NH summer. (3) In the central Pacific, during NH autumn, there was a well-defined approximately 4 1/2-day oscillation with maximum amplitude in the lower troposphere and baroclinic phase tilt above. The vertical structure suggested coupling to deep tropical convection; this interpretation was supported by correlation of meridional wind with antisymmetric outgoing longwave radiation. (4) In the stratosphere, Rossby-gravity waves had periods less than or equal to 4 days and zonal wavenumber 3-4. Unlike tropospheric waves, these disturbances were coherent in a shallow layer, largest in west phase of quasi-biennial oscillation (QBO) and annual cycle (NH winter-spring).

Dunkerton, Timothy J.↗
NASA NTRS1994

Angular momentum exchange among the solid Earth, atmosphere, and oceans: A case study of the 1982-1983 El Nino event

The 1982-1983 El Nino/Southern Oscillation (ENSO) event was accompanied by the largest interannual variation in the Earth's rotation rate on record. In this study we demonstrate that atmospheric forcing was the dominant cause for this rotational anomaly, with atmospheric angular momentum (AAM) integrated from 1000 to 1 mbar (troposphere plus stratosphere) accounting for up to 92% of the interannual variance in the length of day (LOD). Winds between 100 and 1 mbar contributed nearly 20% of the variance explained, indicating that the stratosphere can play a significant role in the Earth's angular momentum budget on interannual time scales. Examination of LOD, AAM, and Southern Oscillation Index (SOI) data for a 15-year span surrounding the 1982-1983 event suggests that the strong rotational response resulted from constructive interference between the low-frequency (approximately 4-6 year) and quasi-biennial (approximately 2-3 year) components of the ENSO phenomenon, as well as the stratospheric Quasi-Biennial Oscillation (QBO). Sources of the remaining LOD discrepancy (approximately 55 and 64 microseconds rms residual for the European Centre for Medium-Range Forecasting (EC) and U.S. National Meteorological Center (NMC) analyses) are explored; noise and systematic errors in the AAM data are estimated to contribute 18 and 33 microseconds, respectively, leaving a residual (rms) of 40 (52) microseconds unaccounted for by the EC (NMC) analysis. Oceanic angular momentum contributions (both moment of inertia changes associated with baroclinic waves and motion terms) are shown to be candidates in closing the interannual axial angular momentum budget.

Dickey, J. O.↗
NASA NTRS1993

Generation of pseudo-waves in the middle atmosphere by flow accelerations due to breaking gravity waves?

Low frequency, large amplitude waves are often observed at mesospheric heights in radar and lidar wind measurements. A series of individual profiles of 1-hr averages of velocity data that were taken in October 1981 using the MST radar at Poker Flat, Alaska are presented. The vertical wavelength of this wave-like event is about 15 km and has a period close to 10 hours. A clear downward phase propagation can be seen, and so these oscillations are usually, and probably correctly, interpreted as being gravity wave flow perturbations. We investigate an alternative explanation that may also be possible; specifically, we investigate the possibility that the perturbed flow is a pseudo-wave structure produced by mean flow acceleration due to gravity waves propagating upward from below and breaking in the mesosphere. The question is whether effects similar to those that produce the much longer period Quasi-Biennial Oscillation (QBO) in the equatorial stratosphere can produce mesospheric pseudo-waves (MPW) at much shorter periods.

Jacobson, Raymond A.↗
NASA NTRS1997

Observational and Model Studies of Large-Scale Mixing Processes in the Stratosphere

The following is the final technical report for grant NAGW-3442, 'Observational and Model Studies of Large-Scale Mixing Processes in the Stratosphere'. Research efforts in the first year concentrated on transport and mixing processes in the polar vortices. Three papers on mixing in the Antarctic were published. The first was a numerical modeling study of wavebreaking and mixing and their relationship to the period of observed stratospheric waves (Bowman). The second paper presented evidence from TOMS for wavebreaking in the Antarctic (Bowman and Mangus 1993). The third paper used Lagrangian trajectory calculations from analyzed winds to show that there is very little transport into the Antarctic polar vortex prior to the vortex breakdown (Bowman). Mixing is significantly greater at lower levels. This research helped to confirm theoretical arguments for vortex isolation and data from the Antarctic field experiments that were interpreted as indicating isolation. A Ph.D. student, Steve Dahlberg, used the trajectory approach to investigate mixing and transport in the Arctic. While the Arctic vortex is much more disturbed than the Antarctic, there still appears to be relatively little transport across the vortex boundary at 450 K prior to the vortex breakdown. The primary reason for the absence of an ozone hole in the Arctic is the earlier warming and breakdown of the vortex compared to the Antarctic, not replenishment of ozone by greater transport. Two papers describing these results have appeared (Dahlberg and Bowman; Dahlberg and Bowman). Steve Dahlberg completed his Ph.D. thesis (Dahlberg and Bowman) and is now teaching in the Physics Department at Concordia College. We also prepared an analysis of the QBO in SBUV ozone data (Hollandsworth et al.). A numerical study in collaboration with Dr. Ping Chen investigated mixing by barotropic instability, which is the probable origin of the 4-day wave in the upper stratosphere (Bowman and Chen). The important result from this paper is that even in the presence of growing, unstable waves, the mixing barriers around

Bowman, Kenneth P.↗
NASA NTRS1999

The Tropical Upper Troposphere and Lower Stratosphere in the GEOS-2 GCM

The structure of the tropical upper troposphere and lower stratosphere in the GEOS-2 General Circulation Model (GCM) is discussed. The emphasis of this study is on the reality of monthly-mean temperature and water vapor distributions in the model, compared to reasonable observational estimates. It is shown that although the zonal-mean temperature is in good agreement with observations, the GCM supports an excessive zonal asymmetry near the tropopause compared to the ECMWF Reanalyses. In reality there is a QBO-related variability in the zonally averaged lower stratospheric temperature which is not captured by the model. The observed upper tropospheric temperature and humidity fields show variations related to those in the sea surface temperature, which are not incorporated in the GCM; nevertheless, there is some interannual variability in the GCM, indicating a component arising from internal processes. The model is too moist in the middle troposphere (500 hPa) but too dry in the upper troposphere, suggesting that there is too little vertical transport or too much drying in the GCM. Transport into the stratosphere shows a pronounced annual cycle, with drier air entering the tropical stratosphere when the tropopause is coldest in northern winter; while the alternating dry and moist air masses can be traced ascending through the tropical lower stratosphere, the progression of the anomalies is too rapid.

Pawson, S.↗
NASA NTRS1999

The Seasonal and Interannual Variability of the Budgets of N2O and CCl3F

The 6-year wind archives from the Goddard Institute for Space Studies/Global Climate-Middle Atmosphere Model (GISS/GCMAM) were in- put to the GISS/Harvard/Irvine Chemical Transport Model (G/H/I CTM) to study the seasonal and interannual variability of the budgets and distributions of nitrous oxide (N2O) and trichlorofluoromethane (CCl3F), with the corresponding chemical loss frequencies recycled and boundary conditions kept unchanged from year to year. The effects of ozone feedback and quasi-biennial oscillation (QBO) were not included. However, the role of circulation variation in driving the lifetime variability is investigated. It was found that the global loss rates of these tracers are related to the extratropical planetary wave activity, which drives the tropical upward mass flux. For N2O, a semiannual signal in the loss rate variation is associated with the interhemispheric asymmetry in the upper stratospheric wave activity. For CCl3F, the semiannual signal is weaker, associated with the comparatively uniform wave episodes in the lower stratosphere. The loss rates lag behind the wave activity by about 1-2 months. The interannual variation of the GCM generated winds drives the interannual variation of the annually averaged lifetime. The year-to-year variations of the annually averaged lifetimes can be about 3% for N2O and 4% for CCl3F.

Wong, Sun↗
NASA NTRS1999

A Simple Stratosphere-Mesosphere Extension of the Held-Suarez Forcing for Dynamical Cores

A simple extension of the Held-Suarez (H-S) forcing that is capable of producing a realistic general circulation not only in the troposphere but also the stratosphere and the mesosphere will be presented. Similar to the original H-S forcing, an annual-mean like radiative equilibrium temperature is used. This extension is an ideal test bed for gravity wave drag parameterizations. It is also an inexpensive test bed for studying the mechanism of the Quasi-Biannual oscillations (QBO) and the "age spectrum" of the dynamical core formulation. The "mean climate" as well as the natural variability of the middle atmosphere as simulated by the NASA Data Assimilation Office finite-volume dynamical core under this forcing will be shown.

Lin, S.-J.↗
NASA NTRS2000

Significant Features Found in Simulated Tropical Climates Using a Cloud Resolving Model

Cloud resolving model (CRM) has widely been used in recent years for simulations involving studies of radiative-convective systems and their role in determining the tropical regional climate. The growing popularity of CRMs usage can be credited for their inclusion of crucial and realistic features such like explicit cloud-scale dynamics, sophisticated microphysical processes, and explicit radiative-convective interaction. For example, by using a two-dimensional cloud model with radiative-convective interaction process, found a QBO-like (quasibiennial oscillation) oscillation of mean zonal wind that affected the convective system. Accordingly, the model-generated rain band corresponding to convective activity propagated in the direction of the low-level zonal mean winds; however, the precipitation became "localized" (limited within a small portion of the domain) as zonal mean winds were removed. Two other CRM simulations by S94 and Grabowski et al. (1996, hereafter G96), respectively that produced distinctive quasi-equilibrium ("climate") states on both tropical water and energy, i.e., a cold/dry state in S94 and a warm/wet state in G96, have later been investigated by T99. They found that the pattern of the imposed large-scale horizontal wind and the magnitude of the imposed surface fluxes were the two crucial mechanisms in determining the tropical climate states. The warm/wet climate was found associated with prescribed strong surface winds, or with maintained strong vertical wind shears that well-organized convective systems prevailed. On the other hand, the cold/dry climate was produced due to imposed weak surface winds and weak wind shears throughout a vertically mixing process by convection. In this study, considered as a sequel of T99, the model simulations to be presented are generally similar to those of T99 (where a detailed model setup can be found), except for a more detailed discussion along with few more simulated experiments. There are twelve major experiments chosen for presentations that are introduced in section two. Several significant feature analyses regarding the rainfall properties, CAPE (Convective Available Potential Energy), cloud-scale eddies, the stability issue, the convective system propagation, relative humidity, and the effect on the quasi-equilibrium state by the imposed constant. radiation or constant surface fluxes, and etc. will be presented in the meeting. However, only three of the subjects are discussed in section three. A brief summary is concluded in the end section.

Shie, C.-L.↗
NASA NTRS2000

Recent Changes in Tropospheric Ozone in the Tropics

This paper presents a detailed characterization of tropical tropospheric column ozone variability on time scales varying from a few days to a solar cycle. The study is based on more than 20 years (1979 to the present) of tropospheric column ozone time series derived from the convective cloud differential (CCD) method using total ozone mapping spectrometer (TOMS) data. Results indicate three distinct regions in the tropics with distinctly three different zonal characteristics related to seasonal, interannual and solar variabilities. These three regions are the eastern Pacific, Atlantic, and western Pacific. Tropospheric column ozone in the Atlantic region peaks at about the same time (September-October) from 20 N to 20 S. The amplitude of the annual cycle, however, varies from about 3 to 6 Dobson unit (DU) from north to south of the equator. In comparison, the annual cycle in both the eastern and western Pacific is generally week and the phase varies from peak values in March and April in the northern hemisphere to September and October in the southern hemisphere. The interannual pattern in the three regions are also very different. The Atlantic region indicates a quasi biennial oscillation in the tropospheric column ozone which is out of phase with the stratospheric ozone. This is consistent with the photochemical control of this region caused by high pollution and high concentration of ozone producing precursors. The observed pattern, however, does not seem to be related to the interannual variability in ozone precursors related to biomass burning. Instead, it appears to be a manifestation of the UV modulation of upper tropospheric chemistry on a QBO time scale caused by stratospheric ozone. During El Nino events, there is anomalously low ozone in the eastern Pacific and high values in the western Pacific indicating the effects of convectively driven transport. The observed increase of 10-20 DU in tropospheric column ozone in the Indonesian region in the western Pacific during the recent 1997-1998 El Nino was associated with large-scale forest fires which may have contributed 5-10 DU of the total increase.

Chandra, S.↗
NASA NTRS2000

Modeling Planetary Waves in the Middle Atmosphere

In our 3D Numerical Spectral Model (NSM) that incorporates the Doppler Spread Parameterization of Hines, planetary waves are generated with zonal wavenumbers 1-4 that have amplitudes as large as 25 m/s and periods between 50 and 2 days. The waves are generated spontaneously, i.e., without external source, and presumably represent normal modes. Numerical experiments are discussed to shed light on the generation mechanisms. For the wavenumbers 1 and 2 with periods primarily between 4 and 15 days, both eastward and westward propagating waves are generated and their amplitudes are affected significantly by the gravity wave source. For the wavenumbers, 3 and 4 in the upper mesosphere, the waves are virtually monochromatic, with periods around 2.5 days and they propagate westward. These waves behave like Rossby gravity waves; their amplitudes are largest during solstice where the baroclinic instability is playing an important role, but the waves decay when the gravity wave momentum source is turned off. The planetary waves generated in the model produce large amplitude modulations of the diurnal tides at altitudes above 80 km, but contrary to expectations they are not playing an important role for the seasonal variations of the tides. Preliminary results show that such Rossby gravity waves are also generated near the tropopause and are influencing significantly the QBO that is generated in the model.

Mengel, J. G.↗
NASA NTRS2000

Modeling the Dynamics of the Middle Atmosphere and Lower Thermosphere Under the Influence of Gravity Waves

Our Numerical Spectral Model (NSM), which extends from the ground up into the thermosphere, is non-linear, time-dependent and has been employed for 2D and 3D applications. The standard version of the NSM incorporates Hines' Doppler Spread Parameterization for small scale gravity waves (GW), but planetary waves generated in the troposphere have also been incorporated. The NSM has been applied to describe: (1) the anomalous seasonal variations of the zonal circulation and temperature in the upper mesosphere, (2) the equatorial oscillations (quasi-biennial and semi-annual oscillations (QBO and SAO)) extending from the stratosphere into the upper mesosphere, (3) the diurnal and semi-diurnal tides, and (4) the planetary waves that are excited in the mesosphere. With the emphasis to provide understanding, we present here results from numerical experiments with the NSM that shed light on the GW processes that are of central importance in the mesosphere and lower thermosphere. These are our conclusions: (1) The large semiannual variations in the diurnal tide (DT), with peak amplitudes observed around equinox, are produced primarily by GW interactions that involve, in part, planetary waves. The DT, like planetary waves, tends to be amplified by GW momentum deposition, which reduces also the vertical wavelength, but variations in eddy viscosity associated with GW interactions are also important. (2) The semidiurnal tide (SDT) and its phase in particular, is strongly influenced by the mean zonal circulation. The SDT, individually, is also amplified by GW. But the DT filters out GW such that the GW interaction effectively reduces the amplitude of the SDT, producing a strong nonlinear interaction between the DT and SDT. (3) Without external time dependent energy or momentum sources, planetary waves (PW) are generated in the model for zonal wavenumbers 1 to 4, which have amplitudes in the mesosphere above 50 km as large as 40 m/s and periods between 50 and 2 days. The waves are generated primarily during solstice conditions, which indicates that the baroclinic instability (associated with the GW induced reversal in the latitudinal temperature gradient) is playing an important role. Numerical experiment show that GW, directly, also greatly amplify the PW. A common feature of the PW generated in summer and winter is that their vertical wavelengths throughout the mesosphere are large, which indicates that the waves are not propagating freely but are generated throughout the region. Another common feature is that the PW propagate preferentially westward in summer and eastward in winter, being launched from the westward and eastward zonal winds that prevail respectively in summer and winter at altitudes below 80 km. (4) Planetary waves generated internally by baroclinic instability and GW interaction produce large amplitude modulations of the DT and SDT. In summary we conclude that GW play major roles in generating and amplifying the dynamical components in the MLT region and, acting principally through wave filtering, produce important non-linear interactions between the components.

Mayr, H. G.↗
NASA NTRS2000

Evaluating the Information Content of Newly Retrieved SAGEII NO2 Measurements in the Lower Stratosphere

The objective of this research project is: to calculate ozone trends in the stratosphere from Dobson Umkehr measurements, to determine the vertical profile of trends at Arosa by using a sophisticated statistical model (MARCH) to separate solar, aerosol, and QBO effects on Dobson Umkehr measurements, and to compare Umkehr trends with SBUV and SAGE I/II trends in the stratosphere.

Newchurch, Michael J.↗