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NASA NTRS2014

Northern Winter Climate Change: Assessment of Uncertainty in CMIP5 Projections Related to Stratosphere-Troposphere Coupling

Future changes in the stratospheric circulation could have an important impact on northern winter tropospheric climate change, given that sea level pressure (SLP) responds not only to tropospheric circulation variations but also to vertically coherent variations in troposphere-stratosphere circulation. Here we assess northern winter stratospheric change and its potential to influence surface climate change in the Coupled Model Intercomparison Project-Phase 5 (CMIP5) multimodel ensemble. In the stratosphere at high latitudes, an easterly change in zonally averaged zonal wind is found for the majority of the CMIP5 models, under the Representative Concentration Pathway 8.5 scenario. Comparable results are also found in the 1% CO2 increase per year projections, indicating that the stratospheric easterly change is common feature in future climate projections. This stratospheric wind change, however, shows a significant spread among the models. By using linear regression, we quantify the impact of tropical upper troposphere warming, polar amplification, and the stratospheric wind change on SLP. We find that the intermodel spread in stratospheric wind change contributes substantially to the intermodel spread in Arctic SLP change. The role of the stratosphere in determining part of the spread in SLP change is supported by the fact that the SLP change lags the stratospheric zonally averaged wind change. Taken together, these findings provide further support for the importance of simulating the coupling between the stratosphere and the troposphere, to narrow the uncertainty in the future projection of tropospheric circulation changes.

climate change↗
DOE OSTI2026

Towards retrieving cloud top entrainment velocities from MISR cloud motion vectors

Although important, direct retrievals of entrainment rates in cloud-topped planetary boundary layer (PBL) remain elusive. Here we present a novel technique for retrieving cloud-top entrainment velocities using only Multi-angle Imaging Spectro-Radiometer (MISR) stereoscopic retrievals of cloud-motion vectors (CMVs) and cloud-top heights (CTHs). Mesoscale vertical air velocity at CTH is diagnosed from the continuity equation and then used to derive entrainment velocities from the PBL mass-budget equation. The algorithm is demonstrated through a case of marine stratocumulus deck off the California coast, with comparisons made against data from the European Centre for Medium-range Weather Forecasts (ECMWF) reanalysis (ERA5) and the data from other satellites. MISR low-cloud CTH for this case were lower than the ERA5 reported PBL depth by 189 ± 87 m. These differences in cloud top heights partly modulate the differences in the ERA5 and MISR horizontal winds, with larger differences in meridional over zonal wind components. Average difference between ERA5 and MISR derived mesoscale vertical air motion at cloud top was 0.14 ± 0.73 cm s −1 , while the same for entrainment rate was −0.09 ± 0.46 cm s −1 . The uncertainties in the utilized CTHs and CMVs are propagated to derive systematic and random retrieval uncertainties. Fractional uncertainty is lower than 25 % when the retrieved mesoscale vertical air motion is stronger than ±0.04 cm s −1 and entrainment velocities are stronger than ±0.03 cm s −1 . These results showcase the ability to derive mesoscale vertical air motion and entrainment rates from MISR observations and motivate its extension to generate a global climatology leveraging its full 23-year record (2000–2022). Nonetheless comprehensive validation of the retrievals is warranted through comparisons with estimates from an independent dataset across diverse weather conditions.

Mitra, Arka [Argonne National Laboratory (ANL), Ar↗
NASA NTRS1985

Mesospheric Winds and Tides at Arecibo/puerto Rico (18 Deg N, 67 Deg W) November 20-23, 1981

The SOUSY-VHF-Radar was operated in the period November 20 to 23, 1981 during a continuous run at the Arecibo Observatory. The data used for this analysis were recorded from 06 AST on November 20 until 06 AST on November 23. Meridional winds were measured at odd hours and zonal winds at even hours. The occurrence of mesospheric VHF radar echoes was limited as usual to the daylight hours between 06 and 18 AST. The height limits, were variable from day to day, they were roughly 62 to 90 km. The intermittency of echoes in time and height, as well as radio interference, made it fairly difficult to deduce tidal information for this time period. About 10 to 45 single velocity estimates could be used to calculate an hourly mean. The variance of the displayed resulting in data, obtained by weighted averaging over the 3 day period, is about similar to the mean. The winds were extremely low during the observation period. Velocities of the prevailing wind, observed during an earlier campaign were 5 to 10 times larger than in the period of November 20 to 23, 1981. The amplitudes of the diurnal tide are comparable.

Rottger, J.↗
NASA NTRS1988

Distribution of major stratospheric warmings in relation to the quasi-biennial oscillation

Data from 1953 to the present indicate that major warmings in the Northern Hemisphere winter have not occurred when the equatorial monthly mean zonal winds are deep westerly (i.e., westerly over more than about 5/8 of the 10-85 mb layer). Sixteen winters have had a major warming in the last 35 years. Six January-February periods had deep equatorial westerlies but did not experience a major warming. Major warmings do not require deep equatorial easterlies, nor is the occurrence of a major warming significantly correlated with the sign of the zonal mean wind at any particular level between 10 and 50 mb, although more than half of the observed major warmings have occurred when the equatorial flow is easterly at a given level between 10 and 50 mb. A more relevant quasi-biennial oscillation (QBO) statistic may be found in the depth of QBO wind regimes. The previously proposed connection between the equatorial QBO and the major warmings of the Northern Hemisphere winter (Holton and Tan, 1980 and 1982) is supported by these observations.

Dunkerton, Timothy J.↗
NASA NTRS1987

Tidal influences on vertical diffusion and diurnal variability of ozone in the mesosphere

Possible dynamical influences on the diurnal behavior of ozone are investigated. A time dependent one-dimensional photochemical model is developed for this purpose; all model calculations are made at 70 deg N during summer. It is shown that the vertical diffusion can vary as much as 1 order of magnitude within a day as a result of large changes in the zonal wind induced by atmospheric thermal tides. It is found that by introducing a dissipation time scale for turbulence produced by breaking gravity waves, the agreement with Poker Flat echo data is improved. Comparisons of results from photochemical model calculations, where the vertical diffusion is a function of height only, with those in which the vertical diffusion coefficient is changing in time show large differences in the diurnal behavior of ozone between 70 and 90 km. By including the dynamical effect, much better agreement with the Solar Mesosphere Explorers data is obtained. The results are, however, sensitive to the background zonally averaged wind. The influence of including time-varying vertical diffusion coefficient on the OH densities is also large, especially between 80 and 90 km. This suggests that dynamical effects are important in determining the diurnal behavior of the airglow emission from the Meinel bands.

Bjarnason, Gudmundur G.↗
NASA NTRS1985

Middle atmosphere (60-110 km) tidal oscillations at Saskatoon, Canada (52 deg N, 107 deg W) during 1983/84

Since mid-1978, the medium frequency (2.2 MHz; M.F.) radar at Saskatoon has run continuously, measuring winds by the spaced antenna method in the upper middle atmosphere. As there is so much dynamics activity during the years of MAP it seems very important to establish the features of the tidal field at Saskatoon during 1983 to 1984, and compare these with the climatology from the four years 1978 to 1979 and 1981 to 1982. Wind profiles with 60 to 110 km (80 to 110 km at night) with 3 km resolution are obtained every 5 minutes by means of a full-correlation analysis. Hourly means are formed and harmonic analysis applied to sets of data to obtain the mean winds and tidal oscillation amplitudes and phases. The zonal wind field at Saskatoon is structurally similar to CIRA-72; however, the wind eastward cell is weaker and much more structured, and the summer eastward cell above 85 km is also weaker. For the semidiurnal tide, a strong seasonal change exists, with larger amplitudes and shorter wavelengths, in winter-like months and the reverse in summer-like months. A summary of the tidal parameters at 90 km is given, where mean values from 1978 to 1982 are also shown. This seasonal variation of tides is a midlatitude climatology, as comparisons with Monpazier, France and Christchurch, New Zealand show very similar behavior, as does Durham; and requires antisymmetric tidal modes such as 2,3 and 2,5. Considering the diurnal tide, for most months centered on summer there are long wavelength modes, or superposition of several models. However, some winter months show a short wavelength mode. A summary of the 90 km characteristics is presented.

Manson, A. H.↗
NASA NTRS1998

Surface-Wind Anomalies in North-Atlantic and North Pacific from SSM/I Observations: Influence on Temperature of Adjoining Land Regions

Surface winds over the oceans are derived from Special Sensor Microwave Imager (SSM/I) measurements, assigning direction by Variational Analysis Method (VAM). Validations by comparison with other measurements indicate highly-satisfactory data quality. Providing global coverage from 1988, the dataset is a convenient source for surface-wind climatology. In this study, the interannual variability of zonal winds is analyzed concentrating on the westerlies in North Atlantic and North Pacific, above 30 N. Interannual differences in the westerlies exceeding 10 m sec (exp -1) are observed over large regions, often accompanied by changes of the same magnitude in the easterlies below 30 N. We concentrate on February/March, since elevated temperatures, by advancing snow-melt, can produce early spring. The extremely strong westerlies in 1997 observed in these months over North Atlantic (and also North Pacific) apparently contributed to large surface-temperature anomalies in western Europe, on the order of +3 C above the climatic monthly average for England and France. At these latitudes strong positive anomalies extended in a ring around the globe. We formulated an Index of South westerlies for the North Atlantic, which can serve as an indicator for day-by-day advection effects into Europe. In comparing 1997 and 1998 with the previous years, we establish significant correlations with the temperature anomalies (one to five days later, depending on the region, and on the season). This variability of the ocean-surface winds and of the temperature anomalies on land may be related to the El Nino/La Nina oscillations. Such large temperature fluctuations over large areas, whatever the cause, can be regarded as noise in attempts to assess long-term trends in global temperature.

Otterman, Joseph↗
NASA NTRS1981

Titan's atmosphere - Temperature and dynamics

In the lower atmosphere of Titan IR brightness temperatures exhibit meridional contrast less than approximately 3 K. Seasonal variations are absent because of the large radiative time constant. In the upper stratosphere meridional contrasts are approximately 20 K, consistent with 100 m/s cyclostrophic zonal winds, and the radiative time constant is short, implying a large seasonal variation in the temperature and wind field. The absence of longitudinal thermal structure implies that zonally symmetric flows effect the meridional transport of heat. A simple model yields meridional velocities approximately 0.04 cm/s and vertical eddy viscosities approximately 1,000 sq cm/s in the lower troposphere, and meridional velocities approximately 5 cm/s in the upper stratosphere.

Flasar, F. M.↗
NASA NTRS1992

A thermosphere/ionosphere general circulation model with coupled electrodynamics

A new simulation model of upper atmospheric dynamics is presented that includes self-consistent electrodynamic interactions between the thermosphere and ionosphere. This model calculates the dynamo effects of thermospheric winds, and uses the resultant electric fields and currents in calculating the neutral and plasma dynamics. A realistic geomagnetic field geometry is used. Sample simulations for solar maximum equinox conditions illustrate two previously predicted effects of the feedback. Near the magnetic equator, the afternoon uplift of the ionosphere by an eastward electric field reduces ion drag on the neutral wind, so that relatively strong eastward winds can occur in the evening. In addition, a vertical electric field is generated by the low-latitude wind, which produces east-west plasma drifts in the same direction as the wind, further reducing the ion drag and resulting in stronger zonal winds.

Richmond, A. D.↗
NASA NTRS1984

Structure and dynamics of Saturn's atmosphere

The large-scale structure and dynamics of Saturn's atmosphere, as revealed in the visible markings, wind patterns, and horizontal variation of temperature, are discussed. The large-scale thermal structure is addressed, including the mean vertical structure and the seasons and jets of the horizontal temperature structure. Earth-based and Voyager wind observations are used to discuss the internal rate of rotation, the zonal wind profile, the eddies, and the eddy transport. Dynamic models of the atmospheric circulation are reviewed, discussing the depth of the zonal flow, upwelling and downwelling, deep convection, eddy-mean flow interactions, long-lived ovals, and the zonal velocity profile.

Ingersoll, A. P.↗
NASA NTRS2007

Mesospheric Dynamical Changes Induced by the Solar Proton Events in October-November 2003

The very large solar storms in October-November 2003 caused solar proton events (SPEs) at the Earth that impacted the upper atmospheric polar cap regions. The Thermosphere Ionosphere Mesosphere Electrodynamic General Circulation Model (TIME-GCM) was used to study the atmospheric dynamical influence of the solar protons that occurred in Oct-Nov 2003, the fourth largest period of SPEs measured in the past 40 years. The highly energetic solar protons caused ionization, as well as dissociation processes, and ultimately produced odd hydrogen (HOx) and odd nitrogen (NOy). Significant short-lived ozone decreases (10-70%) followed these enhancements of HOx and NOy and led to a cooling of most of the lower mesosphere. This cooling caused an atmospheric circulation change that led to adiabatic heating of the upper mesosphere. Temperature changes up to plus or minus 2.6 K were computed as well as wind (zonal, meridional, vertical) perturbations up to 20-25% of the background winds as a result of 22 the solar protons. The solar proton-induced mesospheric temperature and wind perturbations diminished over a period of 4-6 weeks after the SPEs. The Joule heating in the mesosphere, induced by the solar protons, was computed to be relatively insignificant for these solar storms with most of the temperature and circulation perturbations caused by ozone depletion in the sunlit hemisphere.

Jackman, Charles H.↗
NASA NTRS1992

Remote sensing of mesospheric winds with the High-Resolution Doppler Imager

Observations of the winds in the upper atmosphere obtained with the High-Resolution Doppler Imager (HRDI) on the Upper Atmosphere Research Satellite (UARS) are discussed. This instrument is a very stable high-resolution triple-etalon Fabry-Perot interferometer, which is used to observe the slight Doppler shifts of absorption and emission lines in the O2 Atmospheric bands induced by atmospheric motions. Preliminary observations indicate that the winds in the mesosphere and lower thermosphere are a mixture of migrating and non-migrating tides, and planetary-scale waves. The mean meridional winds are dominated by the 1,1 diurnal tide which is easily extracted from the daily zonal means of the satellite observations. The daily mean zonal winds are a mixture of the diurnal tide and a zonal flow which is consistent with theoretical expectations.

Hays, Paul B.↗
NASA NTRS1984

Troposphere-stratosphere (surface-55 km) monthly general circulation statistics for the Northern Hemisphere-four year averages

This report presents four year averages of monthly mean Northern Hemisphere general circulation statistics for the period from 1 December 1978 through 30 November 1982. Computations start with daily maps of temperature for 18 pressure levels between 1000 and 0.4 mb that were supplied by NOAA/NMC. Geopotential height and geostrophic wind are constructed using the hydrostatic and geostrophic formulae. Fields presented in this report are zonally averaged temperature, mean zonal wind, and amplitude and phase of the planetary waves in geopotential height with zonal wavenumbers 1-3. The northward fluxes of heat and eastward momentum by the standing and transient eddies along with their wavenumber decomposition and Eliassen-Palm flux propagation vectors and divergences by the standing and transient eddies along with their wavenumber decomposition are also given. Large annual and interannual variations are found in each quantity especially in the stratosphere in accordance with the changes in the planetary wave activity. The results are shown both in graphic and tabular form.

Wu, M. F.↗
NASA NTRS1995

A composite study of the quasi-periodic subtropical wind maxima over the South Pacific during November 1984-April 1985

A composite of 10 cases of zonal wind maxima at 200 hPa over the subtropical region stretching from Australia to the central Pacific is examined for the six-month period, November 1984-April 1985. This region is unique in that distinct westerly jets frequently form and propagate eastward at latitudes between 20 deg and 35 deg S in the summer season. Some statistical tests were applied and suggest that the flow patterns are quasi periodic, consisting of a tendency for new jet streaks to develop over the eastern Australian region approximately every one to two weeks. These jets then take about 10 days to propagate across the western Pacific before dissipating or, perhaps, moving toward higher latitudes. Their average propagation speed is approximately 4 m/s. An examination of the case-to-case variability of the jets provides additional evidence that they are significant features. A diagnosis of the trough/ridge systems at 200 and 850 hPa, together with calculations of the vertically integrated mean and shear kinetic energies suggests that baroclinic processes dominate in the entrance and center regions of the jet, whereas barotropic processes dominate in the exit and downstream regions.

Ko, Ken-Chung↗
NASA NTRS1983

Southern ocean mean monthly waves and surface winds for winter 1978 by Seasat radar altimeter

Data acquired by the SEASAT radar altimeter during the 3 month satellite lifetime are analyzed in a study of the sea state of the southern hemisphere oceans. The lifetime of the SEASAT satellite, July 7 to October 10, 1978, corresponds to the Antarctic winter. Mean monthly maps of wind speed, significant wave height, and swell have been generated from the altimeter measurements along the satellite tracks. These maps delineate spatial and temporal differences of these parameters in the Atlantic, Indian, and Pacific oceans. Several features of the Southern Ocean wind and wave fields agree with conventional descriptions. For example, the principle zonal wind regimes established by the Southeast Trades and Westerlies are clearly evident in the monthly averages. Significant wave height and swell also exhibit minima near the Doldrums at low latitudes with steady increases southward to the latitudes of the Westerlies. However, superimposed on these general patterns is significant variability with horizontal scales as small as 1000 km. The maps also document a gradual migration of the region of absolute maximum wind and wave from the Atlantic eastward to the Indian Ocean and finally into the Pacific.

Mognard, N. M.↗
NASA NTRS2008

Differences and Similarities between Summer and Winter Temperatures and Winds during MaCWAVE

The Mountain and Convective Waves Ascending Vertically Experiment (MaCWAVE) was carried out in two sequences: one during the summer from the Andoya Rocket Range (69N) during July 2002 to examine convective initiation of gravity waves. The second was a winter sequence from ESRANGE (68N) during January 2003 to examine mountain-initiated waves. Inflatable falling spheres released from small meteorological rockets provided significant information about the variation of temperature and wind from 50 km and higher. The small rocket launch activity was restricted to 12-hour periods that inhibited observing a full diurnal cycle, nonetheless, the time-history of the measurements have provided information about tidal motion. During summer, temperature variation was smaller than observed during winter when peak differences reached 15-20 K at 80-85 km. variation in zonal winds varied up to more than 100 mps in summer and winter. Times of wind vs. altitude showed that the peak zonal component occurred approximately two hours ahead of the peak meridional wind. Measurement details and the observed variations are discussed.

Schmidlin, F. J.↗
NASA NTRS1994

Quasi-biennial oscillation and tropical waves in total ozone

Westward and eastward propagating tropical waves in total ozone are investigated in 13 years (1979-1991) of version 6 total column ozone data from the Nimbus 7 total ozone mapping spectrometer (TOMS) satellite instrument. A clear synchronization between the stratospheric quasi-biennial osciallation (QBO) zonal winds and the fast (periods less than 15 days) propagating waves in tropical TOMS data is detailed. Largest total ozone wave amplitudes (about 3-6 Dobson units) occur when their phase propagation direction is primarily opposite the Singapore QBO lower-stratospheric winds. This effect is most apparent in meridionally symmetric components. Examination of specific episodes, including cross-spectral calculations with Singapore rawinsonde wind data (10-70 hPa), reveals signatures of tropically confined eastward propagating Kelvin waves of zonal wavenumbers 1-2 during the descending eastward QBO phase, consistent with acceleration of that QBO phase by Kelvin waves. The TOMS results are also consistent with possible forcing of the westward QBO wind phase by episodes of both meridionally symmetric and asymmetric westward waves. However, in contrast to the case of eastward (Kelvin) waves the strongest westward events appear to be filtered by, rather than forcing, the westward phase of the stratospheric QBO wind. These dominant westward episodes are interpreted as meridionally symmetric westward global normal modes and tropically confined equatorial-Rossby waves 2-6. The events exhibit phase and group speeds characteristic of wave dynamics rather than simple wind advection. These results underscore the utility of the long time series and excellent horizontal coverage of TOMS data for dynamical investigations in the relatively observation-poor tropical stratosphere.

Ziemke, J. R.↗
NASA NTRS1982

Stable and unstable near-resonant states in multilevel, severely truncated, quasi-geostrophic models

Multilevel, severely truncated, quasi-geostrophic models with damping that extend from the surface to 100 km, are used to study the stationary-wave response to orography and the concomitant feedbacks on the zonal flow. For a typical winter zonal-wind profile, it is shown that large amplitude or resonant planetary waves of intermediate zonal wavenumbers of about 4 or 5 occur with an equivalent barotropic structure. It is also shown that wave-zonal flow interaction with a mountain torque and temperature transport is stable to small perturbations on the low side of resonance and unstable on the high side of resonance. Resonant zonal wavenumbers of lower wave wavenumber also occur for the same zonal profile and have a node in the vertical with a small amplitude maximum near the surface and a larger amplitude maximum in the stratosphere. Instability depends on the presence of the orography and the basic asymmetric state as Newtonian damping and surface friction are sufficient to damp the baroclinic instability associated with a linear inviscid model.

Roads, J. O.↗