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J. Blaha and R. Reed

Abstract

Monthly sea-level elevations at Naze and Aburatsu, sites on either side of the Tokara Strait through which the Kuroshio flows, were analyzed for the period 1963–74. The sea-level elevations were adjusted to uniform atmospheric pressure using a barometric factor of 1 cm mb−1. The adjusted elevations are presented as 1) long-term mean seasonal values and 2) deviations from the long-term means. Differences in the elevations between the two sites were then used as indices of the transport of the Kuroshio.

The seasonal amplitude of the elevation differences across the Kuroshio, Naze minus Aburatsu, is ∼13% of the mean surface geopotential anomaly difference of 0.6 dyn m (0/1000 db). The phase of this difference signal indicates maximum northward flow in summer. Zonally integrated wind-stress curl at this latitude in the Pacific interior, however, is most anticyclonic during winter. Instead, the seasonal fluctuations of the Kuroshio are more nearly in phase with the fluctuations in the latitudinal gradients of Ekman pumping in the western North Pacific. The seasonal winds between 7 and 15°N drive a westward interior flow to the western boundary, and winds north of 15°N drive flow away from the western boundary. We speculate that this mechanism effects the seasonal fluctuations of the Kuroshio. The seasonal cycle of Ekman pumping, particularly between 11 and 19°N, is not constant across the Pacific, which helps to reconcile seasonal differences in the fluctuations of the Kuroshio and the North Equatorial Current.

Significant interannual variations are observed in the Kuroshio and at sea-level stations within the North Equatorial Current, e.g., at Guam and Legaspi (Philippines). However, there are fluctuations clearly associated with El Niño at Legaspi, Guam and San Diego which do not appear in the Kuroshio during the 12-year period we examined.

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R. Wexler, R. J. Reed, and J. Honig
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R. K. Reed and J. D. Schumacher

Abstract

Long-term records from four current meters in the Alaskan Stream off Kodiak Island are presented. The net flows decreases with depth and appeared to be in approximate geostrophic equilibrium. Large fluctuations were not common, and the flow was dominated by low-frequency energy. This behavior, which is also supported by temperature and salinity data, suggests a vertically coherent flow with occasional lateral meanders.

The eddy kinetic-energy levels in this region of the Alaskan Stream were quite low, especially in comparison with those in the Kuroshio and Gulf Stream. The flux of momentum across the inshore edge of the Stream appeared to be onshore and to represent a transfer of energy fron3 the mean flow to smaller scales; an eddy viscosity of not more than 106 cm2 s−1 was indicated. The impact on shelf waters of the small, onshore eddy heat flux is unclear.

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Richard J. Reed and Kenneth R. Hardy

Abstract

Widespread and persistent clear air turbulence (CAT) occurred over the Eastern Seaboard of the United States between New York and South Carolina on 18 March 1969. The major synoptic features and a qualitative discussion of the factors contributing to the development of the large vertical wind shears associated with the turbulence are presented. The turbulent region in the vicinity of Wallops Island, Va., was probed with a NASA T-33 research aircraft and with sensitive radars. The clear air radar echoes and the most intense turbulence occurred principally within an upper level frontal zone of about 2 km depth which was produced by the confluence of two currents of widely different origin. The smoothed Richardson number was less than 1.0 throughout the zone and reached its lowest value of ∼0.25 in the region of strongest turbulence. Three distinct types of wave structures were evident in the clear air radar echoes. These were: 1) long sinusoidal arches moving at approximately the wind speed which were oriented in the direction of the wind and wind shear and which had wavelengths of 15–30 km and crest-to-trough amplitudes of nearly 2 km; 2) unstable waves or billows of about 1.6 km wavelength which were superposed on a portion of the long arches and were also oriented in the shear direction; and 3) braided wave-like patterns having a wave-length of ∼5 km and a crest-to-trough amplitude of more than 1 km which were oriented in the cross-wind (and cross-shear) direction.

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N. J. Beyers, B. T. Miers, and R. J. Reed

Abstract

Wind and temperature soundings from a series of 16 meteorological rocket firings over a period of 51 hours between 30 June and 2 July 1965 are presented. Harmonic analysis revealed large diurnal oscillations in the zonal and meridional winds. Both components displayed amplitudes of about 12 m sec−1 near the stratopause (52–56 km) with the phase of the meridional (v) component leading the zonal (u) component by about 5–7 hours at that level. The v component was generally more uniform in both phase and amplitude over the two-day period. Harmonic analysis of the temperatures also revealed a diurnal oscillation with an amplitude of 8.2C at 52 km with the maximum occurring near 1330 hours local time. An attempt to arrive at an independent estimate of the temperature cycle, based essentially on a generalized thermal wind equation, yielded inconclusive results. When this series was combined with previous data, it was concluded that an unmistakable, dominant, diurnal tidal oscillation exists in the stratopause region over White Sands Missile Range (32N) during most or all seasons, particularly in the meridional component.

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R. J. Reed, A. Hollingsworth, W. A. Heckley, and F. Delsol

Abstract

Substantial changes were made to the ECMWF model in May 1985. The extensive revisions to the physical parameterizations were designed to improve the treatment of the large-scale flow in the tropics. In addition, the resolution was increased substantially to a triangular truncation at T106. The purpose of this paper is to evaluate the performance of the new forecasting system on the analysis and forecasting of easterly waves and their associated tropical storms over Africa and the tropical Atlantic.

A wave history generated for the months of August and September 1985 with use of operational analyses and METEOSAT imagery provides the framework for evaluating the performance of the analysis system. The difficulties caused by lack of data are discussed. Shortcomings of the analysis system are illustrated using an example of a short-scale disturbance with a marked convergence line. On the other hand, examples are also presented demonstrating the ability of the analysis system to make sense of widely scattered observations.

The maxima in the vorticity field provide a set of useful markers to track the easterly waves, both in the analyses and in the forecasts. The 48-h forecasts of the positions and intensities of the vorticity maxima are verified those cases for which there is sufficient observational data to have confidence in the low-level wind analysis. The verification results are quite encouraging.

A particular feature of the paper is the series of synoptic studies of the four waves which gave rise to named storms (Danny, Elena, and Gloria) during the period.

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Mark D. Albright, Donald R. Mock, Ernest E. Recker, and Richard J. Reed

Abstract

Heat and moisture budgets are used to compute net condensation rates in the GATE B-scale network for four hours of the day: 0000, 0600, 1200 and 1800 GMT. Budgets are presented for all phases combined, for selected periods of enhanced convection and for selected periods of suppressed convection. Computations are based on fitted values of the meteorological sounding data for the center of the B-scale ship array, on surface heat flux and evaporation measurements for seven ships in the array and on Cox and Griffith's (1979) radiation measurements for Phase III. Results are also presented for the diurnal variation of the basic variables.

Main findings are as follows:

  1. 1) Temperature variations are small, of the order of a few tenths of a degree, with a daytime maximum and nighttime minimum. There is evidence of possible radiation error above 400 mb where the amplitude is largest.
  2. 2) The atmosphere appears to be relatively dry during the day, when convection is most active, and relatively moist at night. It is suggested that this behavior may be caused by instrumental error.
  3. 3) The divergence and vertical velocity undergo characteristic cycles that were repeated in all three phases. It is hypothesized from their behavior that the convection evolves in three distinct stages: a stage of shallow convection during the early night, a stage of vigorously growing, primarily moderate-depth convection in the late night and morning and a stage of predominantly deep convection in the afternoon.
  4. 4) The vertical advection terms dominated both budgets. Variations of heat and moisture storage and of radiation were also important. Surface evaporation and sensible heat flux were essentially constant throughout the day.
  5. 5) Rainfall diagnosed from the heat budget was less than the observed precipitation and rainfall diagnosed from the moisture budget was greater than the observed precipitation in all three phases.
  6. 6) Maximum diagnosed condensation preceded maximum observed precipitation by ∼6 h. Differences between condensation and precipitation rates are attributed in part to storage of condensed water, though errors of measurement undoubtedly contributed to them as well.
  7. 7) The diurnal cycles of precipitation and low-level vertical motion were much larger in the disturbed (trough) region of easterly waves than in the suppressed (ridge) region. During highly suppressed periods the precipitation was uniformly distributed throughout the day while the vertical motion still appeared to show a variation.

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Anita Menhofer, Roger K. Smith, Michael J. Reeder, and Douglas R. Christie

Abstract

Results of a field experiment carried out in 1991 to gather upper-air data on the morning-glory environment are presented. The data include daily early morning radiosonde soundings from Burketown in north Queensland, Australia, for a 28-day period during the late dry season, together with pressure, wind, temperature, and humidity data from a number of surface stations in the region. During the experiment, 16 morning glories were recorded. On all but one day, radiosonde soundings were carried out in the pre-morning-glory environment. On 7 days, additional soundings were carried out within an hour or two of the passage of a morning glory.

Soundings made on days on which morning glories were generated over Cape York Peninsula but failed to reach Burketown are compared with those on days when morning glories were recorded at Burketown. The comparison shows that the depth and strength of the surface-based inversion did not differ significantly and that the stratification of the almost neutral layer above the stable layer was similar on days with and without morning glories. An examination of the wind profiles is unrevealing and leads the authors to reject the hypothesis that the trapping of wave energy is the key factor that determines the longevity of the disturbances. That the leakiness of the wave-guide is not the only factor in the ability of disturbances to cover large distances from their place of origin is consistent with a numerical study by Noonan and Smith, which suggests that the morning-glory bore-wave system is formed and maintained by mesoscale circulations associated with the sea breezes over Cape York Peninsula.

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Guenter Warnecke, Edith I. Reed, Walter B. Fowler, Earl R. Kreins, Lewis J. Allison, and Jaques E. Blamont

Abstract

The presence or absence of clouds, their characteristics, and variations of surface albedo have been correlated with observations made at several different wavelengths in the visible spectrum. These were made at high and low nighttime light levels by an airglow photometer aboard the OGO-4 satellite during August 1967 through January 1968. The wavelength regions studied were approximately 50 Å bands centered at 3914, 5577, 5893, 6225 and 6300 Å, in the energy range of 10−7 to 10−3 erg cm−2 sec−1−1 ster−1 with a field of view of ˜10 degrees. It was found that at the longer wavelengths (6225 and 6300 Å) the observations were strongly influenced by the variations of surface albedo. At the shorter wavelengths, the surface albedo variations were partly masked by the light returned through Rayleigh and Mie scattering. Preliminary analysis is made of surface and clouds by study of reflective radiance under moonlight and other nocturnal illuminations. Possibilities of further analysis are examined including methods of deducing cloud height information.

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Steven J. Goodman, James Gurka, Mark DeMaria, Timothy J. Schmit, Anthony Mostek, Gary Jedlovec, Chris Siewert, Wayne Feltz, Jordan Gerth, Renate Brummer, Steven Miller, Bonnie Reed, and Richard R. Reynolds

The Geostationary Operational Environmental Satellite R series (GOES-R) Proving Ground engages the National Weather Service (NWS) forecast, watch, and warning community and other agency users in preoperational demonstrations of the new and advanced capabilities to be available from GOES-R compared to the current GOES constellation. GOES-R will provide significant advances in observing capabilities but will also offer a significant challenge to ensure that users are ready to exploit the new 16-channel imager that will provide 3 times more spectral information, 4 times the spatial coverage, and 5 times the temporal resolution compared to the current imager. In addition, a geostationary lightning mapper will provide continuous and near-uniform real-time surveillance of total lightning activity throughout the Americas and adjacent oceans encompassing much of the Western Hemisphere. To ensure user readiness, forecasters and other users must have access to prototype advanced products within their operational environment well before launch. Examples of the advanced products include improved volcanic ash detection, lightning detection, 1-min-interval rapid-scan imagery, dust and aerosol detection, and synthetic cloud and moisture imagery. A key component of the GOES-R Proving Ground is the two-way interaction between the researchers who introduce new products and techniques and the forecasters who then provide feedback and ideas for improvements that can best be incorporated into NOAA's integrated observing and analysis operations. In 2012 and beyond, the GOES-R Proving Ground will test and validate display and visualization techniques, decision aids, future capabilities, training materials, and the data processing and product distribution systems to enable greater use of these products in operational settings.

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