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E. T. Pierce

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E. T. Pierce

Trends in atmospheric electricity are illustrated by means of four themes. These are that there is a constant and healthy change in the emphasis of research investigations; that practical applications of any research need to be kept in mind; that—even so—research of no obvious utility at its commencement can still suddenly become of immense importance; and that it is perhaps time for a new Thunderstorm Project. A plea is made for a greater emphasis on “national” rather than “international” research.

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E. T. Pierce and A. L. Whitson

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E. T. Pierce and A. L. Whitson

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Measurements of the electric field on the floor of Yosemite Valley show that the field is usually small in size and negative in sign. As individual waterfalls are approached the field can become several hundreds of volts per meter negative. Traverses up the steep sides of the valley showed a steady trend to increasingly positive fields with increasing height; on the plateau above the valley the field was of the order of +100 v m−1, a conventional fair weather value. Characteristic diurnal variations in field were noted at the valley floor. A maximum of about +10 v m−1 was reached near local noon with a minimum of some −60 v m−1 at midnight. The field fluctuated violently at night, but the variations were slow by day.

The results can be interpreted in terms of a convective exchange layer the development of which is in phase with solar heating, with negative space charge produced at the waterfalls being entrained into the exchange layer.

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N. Cianos, G. N. Oetzel, and E. T. Pierce

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N. Cianos, G. N. Oetzel, and E. T. Pierce

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A VHF lightning direction-finding technique, that can be applied to locate close lightning accurately, has been built and successfully tested. The technique, originally proposed by Oetzel and Pierce (Radio Sci., 4, 199–202, 1969), measures the direction of arrival of the received VHF impulses emitted by a lightning discharge. The direction of arrival is calculated from time-of-arrival measurements between spaced receivers having a separation of the order of 100 m. The shortness of this baseline avoids pulse-identification ambiguities and simplifies the equipment and display requirements. The time-of-arrival measurements are made with high-resolution (10 nsec) digital time-interval counters along with an on-line digital computer to process, store and display the data. The direction-finder has a very fast data acquisition rate and can establish the direction of at least 5000 impulses per second. It is thus feasible to locate, with a high degree of spatial and temporal resolution, the origins of the successive VHF impulses radiated during a lightning flash. Hence the development of lightning discharges within a thundercloud can be traced. A description of the instrumentation techniques and of the results from a successful test conducted in Albuquerque, N.M., is presented.

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R. B. Pierce, W. T. Blackshear, W. L. Grose, R. E. Turner, and T. D. Fairlie

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An analysis of a spontaneous sudden stratospheric warming that occurred during a 2-year integration of the Langley Research Center Atmospheric Simulation Model is presented. The simulated warming resembles observed “wave 1&rdquo warmings in the Northern Hemisphere stratosphere and provides an opportunity to investigate the radiative and dynamical processes occurring during the warming event. Isentropic analysis of potential vorticity sources and sinks indicates that dynamically induced departures from radiative equilibrium play an important role in the warming event. Enhanced radiative cooling associated with a series of upper stratospheric warm pools leads to radiative dampening within the polar vortex. Within the “surf zone” large-scale radiative cooling leads to diabatic advection of high potential vorticity air from aloft. Lagrangian area diagnostics of the simulated warming agree well with LIMS analyses. Dynamical mixing is shown to account for the majority of the decrease in the size of the polar vortex during the simulated warming. An investigation of the nonlinear deformation of material lines that are initially coincident with diagnosed potential vorticity isopleths is conducted to clarify the relationship between the Lagrangian area diagnostics and potential vorticity advection during wave breaking events.

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T. Keenan, P. Joe, J. Wilson, C. Collier, B. Golding, D. Burgess, P. May, C. Pierce, J. Bally, A. Crook, A. Seed, D. Sills, L. Berry, R. Potts, I. Bell, N. Fox, E. Ebert, M. Eilts, K. O'Loughlin, R. Webb, R. Carbone, K. Browning, R. Roberts, and C. Mueller

The first World Weather Research Programme (WWRP) Forecast Demonstration Project (FDP), with a focus on nowcasting, was conducted in Sydney, Australia, from 4 September to 21 November 2000 during a period associated with the Sydney 2000 Olympic Games. Through international collaboration, nine nowcasting systems from the United States, United Kingdom, Canada, and Australia were deployed at the Sydney Office of the Bureau of Meteorology (BOM) to demonstrate the capability of modern forecast systems and to quantify the associated benefits in the delivery of a real-time nowcast service. On-going verification and impact studies supported by international committees assisted by the WWRP formed an integral part of this project. A description is given of the project, including component systems, the weather, and initial outcomes. Initial results show that the nowcasting systems tested were transferable and able to provide valuable information enhancing BOM nowcasts. The project provided for unprecedented interchange of concepts and ideas between forecasters, researchers, and end users in an operational framework where they all faced common issues relevant to real time nowcast decision making. A training workshop sponsored by the World Meteorological Organization (WMO) was also held in conjunction with the project so that other member nations could benefit from the FDP.

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S. Pawson, K. Kodera, K. Hamilton, T. G. Shepherd, S. R. Beagley, B. A. Boville, J. D. Farrara, T. D. A. Fairlie, A. Kitoh, W. A. Lahoz, U. Langematz, E. Manzini, D. H. Rind, A. A. Scaife, K. Shibata, P. Simon, R. Swinbank, L. Takacs, R. J. Wilson, J. A. Al-Saadi, M. Amodei, M. Chiba, L. Coy, J. de Grandpré, R. S. Eckman, M. Fiorino, W. L. Grose, H. Koide, J. N. Koshyk, D. Li, J. Lerner, J. D. Mahlman, N. A. McFarlane, C. R. Mechoso, A. Molod, A. O'Neill, R. B. Pierce, W. J. Randel, R. B. Rood, and F. Wu

To investigate the effects of the middle atmosphere on climate, the World Climate Research Programme is supporting the project “Stratospheric Processes and their Role in Climate” (SPARC). A central theme of SPARC, to examine model simulations of the coupled troposphere–middle atmosphere system, is being performed through the initiative called GRIPS (GCM-Reality Intercomparison Project for SPARC). In this paper, an overview of the objectives of GRIPS is given. Initial activities include an assessment of the performance of middle atmosphere climate models, and preliminary results from this evaluation are presented here. It is shown that although all 13 models evaluated represent most major features of the mean atmospheric state, there are deficiencies in the magnitude and location of the features, which cannot easily be traced to the formulation (resolution or the parameterizations included) of the models. Most models show a cold bias in all locations, apart from the tropical tropopause region where they can be either too warm or too cold. The strengths and locations of the major jets are often misrepresented in the models. Looking at three-dimensional fields reveals, for some models, more severe deficiencies in the magnitude and positioning of the dominant structures (such as the Aleutian high in the stratosphere), although undersampling might explain some of these differences from observations. All the models have shortcomings in their simulations of the present-day climate, which might limit the accuracy of predictions of the climate response to ozone change and other anomalous forcing.

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L. L. Pan, E. L. Atlas, R. J. Salawitch, S. B. Honomichl, J. F. Bresch, W. J. Randel, E. C. Apel, R. S. Hornbrook, A. J. Weinheimer, D. C. Anderson, S. J. Andrews, S. Baidar, S. P. Beaton, T. L. Campos, L. J. Carpenter, D. Chen, B. Dix, V. Donets, S. R. Hall, T. F. Hanisco, C. R. Homeyer, L. G. Huey, J. B. Jensen, L. Kaser, D. E. Kinnison, T. K. Koenig, J.-F. Lamarque, C. Liu, J. Luo, Z. J. Luo, D. D. Montzka, J. M. Nicely, R. B. Pierce, D. D. Riemer, T. Robinson, P. Romashkin, A. Saiz-Lopez, S. Schauffler, O. Shieh, M. H. Stell, K. Ullmann, G. Vaughan, R. Volkamer, and G. Wolfe

Abstract

The Convective Transport of Active Species in the Tropics (CONTRAST) experiment was conducted from Guam (13.5°N, 144.8°E) during January–February 2014. Using the NSF/NCAR Gulfstream V research aircraft, the experiment investigated the photochemical environment over the tropical western Pacific (TWP) warm pool, a region of massive deep convection and the major pathway for air to enter the stratosphere during Northern Hemisphere (NH) winter. The new observations provide a wealth of information for quantifying the influence of convection on the vertical distributions of active species. The airborne in situ measurements up to 15-km altitude fill a significant gap by characterizing the abundance and altitude variation of a wide suite of trace gases. These measurements, together with observations of dynamical and microphysical parameters, provide significant new data for constraining and evaluating global chemistry–climate models. Measurements include precursor and product gas species of reactive halogen compounds that impact ozone in the upper troposphere/lower stratosphere. High-accuracy, in situ measurements of ozone obtained during CONTRAST quantify ozone concentration profiles in the upper troposphere, where previous observations from balloonborne ozonesondes were often near or below the limit of detection. CONTRAST was one of the three coordinated experiments to observe the TWP during January–February 2014. Together, CONTRAST, Airborne Tropical Tropopause Experiment (ATTREX), and Coordinated Airborne Studies in the Tropics (CAST), using complementary capabilities of the three aircraft platforms as well as ground-based instrumentation, provide a comprehensive quantification of the regional distribution and vertical structure of natural and pollutant trace gases in the TWP during NH winter, from the oceanic boundary to the lower stratosphere.

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