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W. J. SPILLMAN, H. R. TOLLEY, and W. G. REED

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

It is just over 15 years since the first major expedition was organized to investigate the “morning glory” phenomenon of northeastern Australia. The authors review briefly what has been learned about the generation and evolution of morning glory disturbances during this time and present data for a particularly interesting event that occurred on 3 October 1991, a day on which two morning glory wave formations, one from the northeast and one from the south, were detected. The morning glories were seen to interact over the Gulf of Carpentaria. Spectacular National Oceanic and Atmospheric Administration/Advanced Very High Resolution Radiometer satellite imagery together with comparatively good surface data are presented for this event. Aspects of the interaction between the northeasterly and southerly morning glories are shown to be consistent with theoretical predictions concerning solitary wave interactions.

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

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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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J. A. Curry, C. A. Clayson, W. B. Rossow, R. Reeder, Y.-C. Zhang, P. J. Webster, G. Liu, and R.-S. Sheu

An integrated approach is presented for determining from several different satellite datasets all of the components of the tropical sea surface fluxes of heat, freshwater, and momentum. The methodology for obtaining the surface turbulent and radiative fluxes uses physical properties of the atmosphere and surface retrieved from satellite observations as inputs into models of the surface turbulent and radiative flux processes. The precipitation retrieval combines analysis of satellite microwave brightness temperatures with a statistical model employing satellite observations of visible/infrared radiances. A high-resolution dataset has been prepared for the Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE) intensive observation period (IOP), with a spatial resolution of 50 km and temporal resolution of 3 h. The high spatial resolution is needed to resolve the diurnal and mesoscale storm-related variations of the fluxes. The fidelity of the satellite-derived surface fluxes is examined by comparing them with in situ measurements obtained from ships and aircraft during the TOGA COARE IOP and from vertically integrated budgets of heat and freshwater for the atmosphere and ocean. The root-mean-square differences between the satellite-derived and in situ fluxes are dominated by limitations in the satellite sampling; these are reduced when some averaging is done, particularly for the precipitation (which is from a statistical algorithm) and the surface solar radiation (which uses spatially sampled satellite pixels). Nevertheless, the fluxes are determined with a useful accuracy, even at the highest temporal and spatial resolution. By compiling the fluxes at such high resolution, users of the dataset can decide whether and how to average for particular purposes. For example, over time, space, or similar weather events.

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B. M. Isom, R. D. Palmer, G. S. Secrest, R. D. Rhoton, D. Saxion, T. L. Allmon, J. Reed, T. Crum, and R. Vogt

Abstract

The wind power industry has seen tremendous growth over the past decade and with it has come the need for clutter mitigation techniques for nearby radar systems. Wind turbines can impart upon these radars a unique type of interference that is not removed with conventional clutter-filtering methods. Time series data from Weather Surveillance Radar-1988 Doppler (WSR-88D) stations near wind farms were collected and spectral analysis was used to investigate the detailed characteristics of wind turbine clutter. Techniques to mask wind turbine clutter were developed that utilize multiquadric interpolation in two and three dimensions and can be applied to both the spectral moments and spectral components. In an effort to improve performance, a nowcasting algorithm was incorporated into the interpolation scheme via a least mean squares criterion. The masking techniques described in this paper will be shown to reduce the impact of wind turbine clutter on weather radar systems at the expense of spatial resolution.

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Janet Sprintall, Victoria J. Coles, Kevin A. Reed, Amy H. Butler, Gregory R. Foltz, Stephen G. Penny, and Hyodae Seo

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Process studies are designed to improve our understanding of poorly described physical processes that are central to the behavior of the climate system. They typically include coordinated efforts of intensive field campaigns in the atmosphere and/or ocean to collect a carefully planned set of in situ observations. Ideally the observational portion of a process study is paired with numerical modeling efforts that lead to better representation of a poorly simulated or previously neglected physical process in operational and research models. This article provides a framework of best practices to help guide scientists in carrying out more productive, collaborative, and successful process studies. Topics include the planning and implementation of a process study and the associated web of logistical challenges; the development of focused science goals and testable hypotheses; and the importance of assembling an integrated and compatible team with a diversity of social identity, gender, career stage, and scientific background. Guidelines are also provided for scientific data management, dissemination, and stewardship. Above all, developing trust and continual communication within the science team during the field campaign and analysis phase are key for process studies. We consider a successful process study as one that ultimately will improve our quantitative understanding of the mechanisms responsible for climate variability and enhance our ability to represent them in climate models.

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

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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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EXECUTIVE COMMITTEE, W. W. Kellogg, D. S. Johnson, R. J. Reed, C. L. Hosier, W. J. Kotsch, P. D. McTaggart-Cowan, K. C. Spengler, and D. F. Landrigan
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EXECUTIVE COMMITTEE, R. J. Reed, W. W. Kellogg, A. K. Blackadar, G. P. Cressman, C. L. Hosler, W. J. Kotsch, K. C. Spengler, and D. F. Landrigan
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