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ALVIN J. MILLER

Abstract

The modulation of the vertical flux of kinetic energy to the stratosphere by the pressure-work effect at 100 mb is compared with variations in the hemispheric kinetic energy, the horizontal momentum and heat transports at “low” latitudes, and the tropical zonal wind and temperature for the lower stratosphere. It is deduced that the variation of the vertical flux of geopotential is in phase with the kinetic energy in the lower stratosphere and is statistically related to the time rate of change of the horizontal transports of heat and momentum at 30°N. The association of these results to the general circulation of the lower stratosphere is considered.

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Alvin J. Miller

Abstract

The vertical flux of geopotential at 100 mb in the wavenumber domain is examined for the 5-year period January 1964-December 1968. It is deduced that a significant correlation exists between this term and the circulation pattern at 10 mb as measured by an appropriate circulation index. A maximum correlation is found when the vertical flux precedes the circulation index by several days. In line with this result the existence of a wave 1 pattern above ∼30 mb as a semi-permanent feature during the winter is associated with generally increased tropospheric forcing at this same wavenumber.

In addition, year-to-year variations of the energy flux are examined. The best correlation between the upward flux of kinetic energy and the quasi-biennial oscillation of the tropical zonal wind at 10 mb is found in wavenumber 1 with maximum flux occurring 4–6 months previous to the maximum easterly winds. The amplitude of this variation in energy flux is the same order of magnitude as current estimates of the yearly energy convergence between 100 and 30 mb.

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Alvin J. Miller

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ALVIN J. MILLER

Abstract

Geostrophic computations in the wave number domain have been made of the “eddy” kinetic energy, the transfer of kinetic energy between the zonal flow and the eddies, and the internal redistribution of kinetic energy among the eddies at 500 mb. An 11-yr record has been inspected for year-to-year variations and the results related to the quasi-biennial oscillation in the lower stratosphere.

The individual wave numbers indicate significant year-to-year variations in their energy cycle that must be considered when only short time periods are under study. While no consistent relationship was found between these variations and the quasi-biennial oscillation, our results suggest that a profitable line of inquiry would be to examine the annual variations of the vertical transfer of kinetic energy by the pressure-work term at the interface of the troposphere and stratosphere.

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Alvin J. Miller

Abstract

By means of spectrum analysis of select components of the tropospheric and lower stratospheric energy cycle in the Northern Hemisphere (20N to the pole), we are able to demonstrate the existence of a 14–16 day cycle in the atmosphere. The principal energy transfer of this cycle is the conversion from zonal available to eddy available potential energy in the troposphere. This is accompanied by an energy exchange from eddy available potential to eddy kinetic energy and thence by means of the pressure-work effect at the stratospheric boundary to the eddy kinetic energy in the stratosphere. The possible physical forcing functions of this cycle are discussed.

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ALVIN J. MILLER

Abstract

No Abstract Available.

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Shuntai Zhou and Alvin J. Miller

Abstract

Tropical and extratropical interactions on the intraseasonal time scale are studied in the context of the Arctic Oscillation (AO) and the Madden–Julian oscillation (MJO). To simplify the discussion, a high (low) MJO phase is defined as strong (suppressed) convective activity over the Indian Ocean. In the Northern Hemisphere (NH) winter season, a high (low) AO phase is found more likely coupled with a high (low) MJO phase. Based on the regressed patterns and composites of various dynamical fields and quantities, possible mechanisms linking the AO and the MJO are examined. The analysis indicates that the MJO influence on extratropical circulations seems more evident than the AO influence on tropical circulations. The MJO interacts with the AO through meridional dispersion of Rossby waves in the Pacific sector. The geopotential height anomaly center over the North Pacific associated with the MJO can either reinforce or offset the AO Pacific action center. As a result, the AO pattern can be greatly affected by the MJO. When the AO and the MJO are in the same (opposite) phase, the Pacific action center becomes much stronger (weaker) than the Atlantic action center. The eddy momentum transports associated with the MJO in the Pacific sector are closely related to the retraction and extension of tropical Pacific easterlies and the subtropical Asian–Pacific jet. Because of its large scale, this regional effect is also reflected in the zonal mean state of wave transport and wave forcing on zonal wind, which in turn affects the phase of the AO.

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Alvin J. Miller and Francis J. Schmidlin

Abstract

In an attempt to separate instrument system “noise” from actual stratospheric variability, six pairs of meteorological rocketsondes (Datasonde instruments) were launched on 20 June 1969, with five pairs being released at 1-hr intervals; the two individual rockets comprising a pair were separated by time intervals of no more than 5 min. The average rms difference between paired soundings was 1.08C and ∼3 m sec−1. These rather low rms values contrasted sharply with rather large changes observed in both the temperature and wind fields. Further research is needed into the interpretation of this variability in terms of mesoscale and small-scale phenomena.

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RAYMOND M. McINTURFF and ALVIN J. MILLER

Abstract

Significant temporal variations in the “quasi-biennial” oscillation (QBO) of the equatorial stratosphere raise questions concerning relationships between the various characteristics of the oscillation. A comparison of observations made before 1962 with those made after 1962 suggests the following relationships: β ≈ PU/4 in the 10- to 30-mb layer; PU/8≤β≤PU/4 in the 30- to 50-mb layer; and cUPU ≈ constant from 10 to 50 mb (where β is the phase difference between the zonal wind-QBO and temperature-QBO, PU is the period of the zonal wind-QBO, and cU is the speed of vertical propagation of the zonal wind-QBO).

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Alvin J. Miller and Christopher M. Hayden

Abstract

Standard atmospheric energy budget computations are made for three distinct sets of Northern Hemisphere synoptic analyses prepared from data gathered during the August 1975 Data Systems Test. The first analysis set (System 1) included all data, the second (System 2) all but the satellite temperature retrievals (excepting some retained in the Southern Hemisphere for analysis model stability), and the third (System 3) all but the rawinsondes. Our results indicate that significant differences occur in the energetics of the analyses. In particular, there is a significant loss of longitudinal variance in an analysis based mainly on satellite retrievals as compared to that based mainly on rawinsonde data. In addition, forecasts by the NMC 6-layer numerical model initiated from System 1 and 2 analyses were evaluated for forecast periods from 00 to 72 h. It appears that this forecast model is sensitive to variations supplied by the initial data sets, but only to 12 h. Thereafter the forecast energetics are controlled by the model physics, and energy differences evolving from the different data sets remain constant in time.

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