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Carl E. Hane, Jill D. Watts, David L. Andra Jr., John A. Haynes, Edward Berry, Robert M. Rabin, and Frederick H. Carr

Abstract

The factors that influence the evolution of convective systems during the late morning over much of the Great Plains are not understood well. It is known that in this region the majority of such systems dissipate or decrease in intensity during this period. With this fact in mind, a summary is given of comments made during the occurrence of morning convective systems by forecasters at two National Weather Service (NWS) offices relating to factors that were most important in determining their forecasts of system evolution. In addition, results of a preliminary climatological study covering eight summer months for 181 summer precipitation systems affecting the county warning areas of the two NWS offices during late morning are presented. Revealed among the significant system characteristics is that approximately two-thirds of the included systems either decreased in intensity or dissipated during the late morning.

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Thorwald H. M. Stein, Robin J. Hogan, Kirsty E. Hanley, John C. Nicol, Humphrey W. Lean, Robert S. Plant, Peter A. Clark, and Carol E. Halliwell

Abstract

A set of high-resolution radar observations of convective storms has been collected to evaluate such storms in the Met Office Unified Model during the Dynamical and Microphysical Evolution of Convective Storms (DYMECS) project. The 3-GHz Chilbolton Advanced Meteorological Radar was set up with a scan-scheduling algorithm to automatically track convective storms identified in real time from the operational rainfall radar network. More than 1000 storm observations gathered over 15 days in 2011 and 2012 are used to evaluate the model under various synoptic conditions supporting convection. In terms of the detailed three-dimensional morphology, storms in the 1500-m grid length simulations are shown to produce horizontal structures a factor of 1.5–2 wider compared to radar observations. A set of nested model runs at grid lengths down to 100 m show that the models converge in terms of storm width, but the storm structures in the simulations with the smallest grid lengths are too narrow and too intense compared to the radar observations. The modeled storms were surrounded by a region of drizzle without ice reflectivities above 0 dBZ aloft, which was related to the dominance of ice crystals and was improved by allowing only aggregates as an ice particle habit. Simulations with graupel outperformed the standard configuration for heavy-rain profiles, but the storm structures were a factor of 2 too wide and the convective cores 2 km too deep.

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Burkely T. Gallo, Christina P. Kalb, John Halley Gotway, Henry H. Fisher, Brett Roberts, Israel L. Jirak, Adam J. Clark, Curtis Alexander, and Tara L. Jensen
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Joannes J. Westerink, Richard A. Luettich, Jesse C. Feyen, John H. Atkinson, Clint Dawson, Hugh J. Roberts, Mark D. Powell, Jason P. Dunion, Ethan J. Kubatko, and Hasan Pourtaheri

Abstract

Southern Louisiana is characterized by low-lying topography and an extensive network of sounds, bays, marshes, lakes, rivers, and inlets that permit widespread inundation during hurricanes. A basin- to channel-scale implementation of the Advanced Circulation (ADCIRC) unstructured grid hydrodynamic model has been developed that accurately simulates hurricane storm surge, tides, and river flow in this complex region. This is accomplished by defining a domain and computational resolution appropriate for the relevant processes, specifying realistic boundary conditions, and implementing accurate, robust, and highly parallel unstructured grid numerical algorithms.

The model domain incorporates the western North Atlantic, the Gulf of Mexico, and the Caribbean Sea so that interactions between basins and the shelf are explicitly modeled and the boundary condition specification of tidal and hurricane processes can be readily defined at the deep water open boundary. The unstructured grid enables highly refined resolution of the complex overland region for modeling localized scales of flow while minimizing computational cost. Kinematic data assimilative or validated dynamic-modeled wind fields provide the hurricane wind and pressure field forcing. Wind fields are modified to incorporate directional boundary layer changes due to overland increases in surface roughness, reduction in effective land roughness due to inundation, and sheltering due to forested canopies. Validation of the model is achieved through hindcasts of Hurricanes Betsy and Andrew. A model skill assessment indicates that the computed peak storm surge height has a mean absolute error of 0.30 m.

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James L. Partain Jr., Sharon Alden, Heidi Strader, Uma S. Bhatt, Peter A. Bieniek, Brian R. Brettschneider, John E. Walsh, Rick T. Lader, Peter Q. Olsson, T. Scott Rupp, Richard L. Thoman Jr., Alison D. York, and Robert H. Ziel
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Robert W. Burpee, Sim D. Aberson, Peter G. Black, Mark DeMaria, James L. Franklin, Joseph S. Griffin, Samuel H. Houston, John Kaplan, Stephen J. Lord, Frank D. Marks Jr., Mark D. Powell, and Hugh E. Willoughby

The Hurricane Research Division (HRD) is NOAA's primary component for research on tropical cyclones. In accomplishing research goals, many staff members have developed analysis procedures and forecast models that not only help improve the understanding of hurricane structure, motion, and intensity change, but also provide operational support for forecasters at the National Hurricane Center (NHC). During the 1993 hurricane season, HRD demonstrated three important real-time capabilities for the first time. These achievements included the successful transmission of a series of color radar reflectivity images from the NOAA research aircraft to NHC, the operational availability of objective mesoscale streamline and isotach analyses of a hurricane surface wind field, and the transition of the experimental dropwindsonde program on the periphery of hurricanes to a technology capable of supporting operational requirements. Examples of these and other real-time capabilities are presented for Hurricane Emily.

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David J. Diner, Thomas P. Ackerman, Theodore L. Anderson, Jens Bösenberg, Amy J. Braverman, Robert J. Charlson, William D. Collins, Roger Davies, Brent N. Holben, Chris A . Hostetler, Ralph A. Kahn, John V. Martonchik, Robert T. Menzies, Mark A. Miller, John A. Ogren, Joyce E. Penner, Philip J. Rasch, Stephen E. Schwartz, John H. Seinfeld, Graeme L. Stephens, Omar Torres, Larry D. Travis, Bruce A . Wielicki, and Bin Yu

Aerosols exert myriad influences on the earth's environment and climate, and on human health. The complexity of aerosol-related processes requires that information gathered to improve our understanding of climate change must originate from multiple sources, and that effective strategies for data integration need to be established. While a vast array of observed and modeled data are becoming available, the aerosol research community currently lacks the necessary tools and infrastructure to reap maximum scientific benefit from these data. Spatial and temporal sampling differences among a diverse set of sensors, nonuniform data qualities, aerosol mesoscale variabilities, and difficulties in separating cloud effects are some of the challenges that need to be addressed. Maximizing the longterm benefit from these data also requires maintaining consistently well-understood accuracies as measurement approaches evolve and improve. Achieving a comprehensive understanding of how aerosol physical, chemical, and radiative processes impact the earth system can be achieved only through a multidisciplinary, interagency, and international initiative capable of dealing with these issues. A systematic approach, capitalizing on modern measurement and modeling techniques, geospatial statistics methodologies, and high-performance information technologies, can provide the necessary machinery to support this objective. We outline a framework for integrating and interpreting observations and models, and establishing an accurate, consistent, and cohesive long-term record, following a strategy whereby information and tools of progressively greater sophistication are incorporated as problems of increasing complexity are tackled. This concept is named the Progressive Aerosol Retrieval and Assimilation Global Observing Network (PARAGON). To encompass the breadth of the effort required, we present a set of recommendations dealing with data interoperability; measurement and model integration; multisensor synergy; data summarization and mining; model evaluation; calibration and validation; augmentation of surface and in situ measurements; advances in passive and active remote sensing; and design of satellite missions. Without an initiative of this nature, the scientific and policy communities will continue to struggle with understanding the quantitative impact of complex aerosol processes on regional and global climate change and air quality.

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Steven V. Vasiloff, Dong-Jun Seo, Kenneth W. Howard, Jian Zhang, David H. Kitzmiller, Mary G. Mullusky, Witold F. Krajewski, Edward A. Brandes, Robert M. Rabin, Daniel S. Berkowitz, Harold E. Brooks, John A. McGinley, Robert J. Kuligowski, and Barbara G. Brown

Accurate quantitative precipitation estimates (QPE) and very short term quantitative precipitation forecasts (VSTQPF) are critical to accurate monitoring and prediction of water-related hazards and water resources. While tremendous progress has been made in the last quarter-century in many areas of QPE and VSTQPF, significant gaps continue to exist in both knowledge and capabilities that are necessary to produce accurate high-resolution precipitation estimates at the national scale for a wide spectrum of users. Toward this goal, a national next-generation QPE and VSTQPF (Q2) workshop was held in Norman, Oklahoma, on 28–30 June 2005. Scientists, operational forecasters, water managers, and stakeholders from public and private sectors, including academia, presented and discussed a broad range of precipitation and forecasting topics and issues, and developed a list of science focus areas. To meet the nation's needs for the precipitation information effectively, the authors herein propose a community-wide integrated approach for precipitation information that fully capitalizes on recent advances in science and technology, and leverages the wide range of expertise and experience that exists in the research and operational communities. The concepts and recommendations from the workshop form the Q2 science plan and a suggested path to operations. Implementation of these concepts is expected to improve river forecasts and flood and flash flood watches and warnings, and to enhance various hydrologic and hydrometeorological services for a wide range of users and customers. In support of this initiative, the National Mosaic and Q2 (NMQ) system is being developed at the National Severe Storms Laboratory to serve as a community test bed for QPE and VSTQPF research and to facilitate the transition to operations of research applications. The NMQ system provides a real-time, around-the-clock data infusion and applications development and evaluation environment, and thus offers a community-wide platform for development and testing of advances in the focus areas.

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Kevin J. Noone, Doug W. Johnson, Jonathan P. Taylor, Ronald J. Ferek, Tim Garrett, Peter V. Hobbs, Philip A. Durkee, Kurt Nielsen, Elisabeth Öström, Colin O’Dowd, Michael H. Smith, Lynn M. Russell, Richard C. Flagan, John H. Seinfeld, Lieve De Bock, René E. Van Grieken, James G. Hudson, Ian Brooks, Richard F. Gasparovic, and Robert A. Pockalny

Abstract

A case study of the effects of ship emissions on the microphysical, radiative, and chemical properties of polluted marine boundary layer clouds is presented. Two ship tracks are discussed in detail. In situ measurements of cloud drop size distributions, liquid water content, and cloud radiative properties, as well as aerosol size distributions (outside-cloud, interstitial, and cloud droplet residual particles) and aerosol chemistry, are presented. These are related to remotely sensed measurements of cloud radiative properties.

The authors examine the processes behind ship track formation in a polluted marine boundary layer as an example of the effects of anthropogenic particulate pollution on the albedo of marine stratiform clouds.

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Kevin J. Noone, Elisabeth Öström, Ronald J. Ferek, Tim Garrett, Peter V. Hobbs, Doug W. Johnson, Jonathan P. Taylor, Lynn M. Russell, Richard C. Flagan, John H. Seinfeld, Colin D. O’Dowd, Michael H. Smith, Philip A. Durkee, Kurt Nielsen, James G. Hudson, Robert A. Pockalny, Lieve De Bock, René E. Van Grieken, Richard F. Gasparovic, and Ian Brooks

Abstract

The effects of anthropogenic particulate emissions from ships on the radiative, microphysical, and chemical properties of moderately polluted marine stratiform clouds are examined. A case study of two ships in the same air mass is presented where one of the vessels caused a discernible ship track while the other did not. In situ measurements of cloud droplet size distributions, liquid water content, and cloud radiative properties, as well as aerosol size distributions (outside cloud, interstitial, and cloud droplet residual particles) and aerosol chemistry, are presented. These are related to measurements of cloud radiative properties. The differences between the aerosol in the two ship plumes are discussed;these indicate that combustion-derived particles in the size range of about 0.03–0.3-μm radius were those that caused the microphysical changes in the clouds that were responsible for the ship track.

The authors examine the processes behind ship track formation in a moderately polluted marine boundary layer as an example of the effects that anthropogenic particulate pollution can have in the albedo of marine stratiform clouds.

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