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ELMAR R. REITER

Abstract

A review is given of mathematical expressions for total and mean specific kinetic energies in the longitudinal, time, and mixed longitudinal-time domains. These coordinate domains differ from those defined earlier by Oort. Mathematical developments are extended into the vertical coordinate domain. A new symbolism is introduced for describing mean and eddy motions.

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Elmar R. Reiter

Abstract

Following the perturbation theory, the aircraft measurements of “Project Jet Stream” Flight No. 29 (4 April 1957) have been analyzed, applying a double-smoothing technique, thus treating the basic fields of flow and temperature separately from the superimposed mesoscale disturbances. Analyses of wind velocity and potential temperature lead to estimates of the distributions of vorticity, potential vorticity and divergence in a vertical cross-section. Several inferences are made as to the meso-structure of the atmosphere near the jet-stream core.

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Elmar R. Reiter

Abstract

During September 1961 a series of balloon ascents made from Flin Flon, Canada, carrying scintillation counters sensitive to gamma radiation, revealed the existence of shallow stable atmospheric layers carrying radioactive debris, presumably from the Russian test series during the same month.

The debris layers encountered on 14 and 15 September have been studied in particular. The debris detected over Flin Flon on 14 September, 2221 GCT, at 650 mb had undergone strong sinking motion. One may conclude that it came from the region immediately underneath the tropopause shortly prior to 13 September, 12 GCT, entering the middle troposphere through the stable layer underneath the jet core, sometimes referred to as a “jet-stream front.”

Beginning with 17 September a distinct area of radioactive fallout begins to appear at the surface over the eastern United States. Some of this debris seems to be identical with the one detected over Flin Flon, and it apparently was transported by the same jet stream. Part of the fallout seems to be associated with a small collapsing cold dome travelling ahead of this jet stream.

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Elmar R. Reiter

Abstract

It is shown that long-term trends in the meridional components of the trade wind circulations in both hemisphere over the Pacific are highly correlated with the precipitation falling in the intertropical convergence zone (ITCZ) over that region. The trends in the trade wind regime, on the one hand, seem to be caused by extratropical sea surface temperature (SST) anomalies in the North Pacific which influence atmospheric meridional temperature and pressure gradients. On the other hand, the release of latent heat in the ITCZ provides a self-enforcing feedback for the trade winds.

A study of the recurrence frequency of precipitation surges over the Line Islands suggests the presence of three epoch (1911–28, 1929–62, 1963 to present) during which the Hadley cell circulation and attendant meteorological and oceanographic features showed different characteristics.

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Elmar R. Reiter

Abstract

Precipitation surges in the equatorial Pacific “dry zone” (as delineated in a study by Doberitz) reveal statistically significant teleconnections with midlatitude tropospheric flow patterns during all seasons. These connections are strongest, however, during winter and agree with linear numerical model results. There is evidence that deep troughs in the central North Pacific antecede precipitation surges in the equatorial dry zone during that season, suggesting the possibility of triggering of such surges by middle latitude planetary-wave perturbations. Nonlinear numerical model results also indicate that the midlatitude planetary-wave response is strongest when North Pacific cold sea-surface temperature anomalies and equatorial East Pacific warm anomalies are present simultaneously.

The planetary-wave pattern associated with equatorial Pacific precipitation surges appears to be in phase with orographically generated wave patterns, whereas an anomalous low-latitude heat source over the extreme equatorial west Pacific, the Bay of Bengal and India, corresponding to rainfall during an active phase of the Indian monsoon, tends to be associated with wave perturbations out-of-phase with orographic forcing.

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Elmar R. Reiter

Abstract

Evidence is derived from observational data that the trade wind circulations in both hemispheres over the Pacific are related to the sea surface temperature (SST) anomalies in the North Pacific. The equatorward component of the surface trade winds leads the North Pacific SST anomalies by approximately 20 months, equivalent to the half-rotation time of the Pacific gyre.

Long-term trends in the Pacific trade wind regime appear to have an influence on hemispheric and global mean temperatures. The trade wind anomalies also seem to be tied to meridional atmospheric pressure- and temperature-gradient anomalies which, in turn, appear to respond to anomalies in the meridional SST gradients. Thus a closed feedback loop is demonstrated, in which SST anomalies in the North Pacific generate trade wind anomalies which promote the development of North Pacific SST anomalies of opposite sign. The trade wind surges also are related to El Niño through a feedback involving the hydrological cycle and upwelling of cold water forced by Ekman pumping.

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Elmar R. Reiter

Abstract

The three-dimensional wind field in the vicinity of the jet stream is defined with the aid of four parameters: mean wind speed and direction, thickness, and mean altitude of the Layer of Maximum Wind (LMW). Routine methods of analysis of these quantities are discussed in view of the reliability of available wind data, and a statistical treatment of these quantities reveals the mean horizontal and vertical structure of the LMW. Forecasts of the LMW are attempted by means of a grid or “box” method, and a control-line method.

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Elmar R. Reiter and Maocang Tang

Abstract

The diurnal variation of 850 mb heights, the detailed distribution of which could be assessed by the inclusion of surface data, and of resultant winds over, and in the vicinity of, the Great Basin reveals clearly a plateau-wind circulation during summer. This circulation reverses between day and night and appears to include the low-level jet stream over Texas and Oklahoma, as well as the time of occurrence of thunderstorms. This plateau circulation system interacts with local mountain-valley breeze systems. The thickness of the daytime inflow and nighttime outflow layer over the plateau is approximately 2 km.

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Maocang Tang and Elmar R. Reiter

Abstract

Detailed analyses are presented of the temperature and pressure fields of the planetary boundary layer (PBL) and their seasonal variability over the western United States and over the Plateau of Tibet (Qinghai-Xizang Plateau). Over the United States these analyses rely on 850 mb data, augmented by surface data. Over Tibet the 600 mb surface adequately describes the PBL.

The effects of a “plateau monsoon” appear prominently during winter and summer over both plateaus. Together with continental monsoon effects they help to shape prominent circulation features, such as the low-level jet stream (LLJ) over Texas and Oklahoma. The complex, seasonal characteristics of precipitation regimes over the North American continent can be explained, to a large extent, by considering these monsoonal changes in the PBL, especially over the mountains.

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Elmar R. Reiter and Daniel Westhoff

Abstract

Ultralong and long planetary waves are analyzed at the 500 mb level in terms of their amplitudes, phases and stationarity characteristics, the latter described in terms of a stationarity index SIn. This index consists of the ratio between planetary-wave amplitudes computed from time-averaged 500 mb height patterns, and the wave amplitudes computed on a daily basis and averaged for the same time interval irrespective of their phase angles. The index assumes the value 1 for completely stationary waves and 0 for randomly variable waves.

Mean 500 mb height and planetary wave characteristics have been developed by calendar day. using NMC data between the years 1946 and 1979. Various significant singularities (i.e., departures from a low-order harmonic seasonal trend) in planetary-wave behavior are described. An index, SIn (d), computed by calendar day, was developed as a measure of probability that a certain planetary wave with number n would achieve its long-term mean phase angle on a certain date. This index, too, shows significant patterns with latitude and season, suggesting the presence of relatively short periods within the seasonal cycles of planetary-wave behavior, during which these waves may be extra sensitive to anomalies in their forcing parameters.

It is suggested that perturbation statistics derived from numerical general circulation models should be compared with the results presented in this study to permit an improved judgement on the veracity of such models.

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