Browse

You are looking at 131 - 140 of 186 items for :

  • Meteorological Monographs x
  • Refine by Access: Content accessible to me x
Clear All
Steven A. Rutledge and V. Chandrasekar

Abstract

Great strides have been made over the past decades in educating radar meteorologists. These advances appear to be loosely associated with the arrival of new hardware in the field, for example, Doppler radars followed by polarimetric radars. Many radar meteorologists received a substantial portion of their early training through participation in field programs utilizing this new hardware. In this study, a brief look at the evolution of radar education will first be offered, followed by an assessment of the current state of this field. Finally, a view of the future will be offered. Future educational thrusts in radar meteorology will take full advantage of Internet technology, allowing radar systems to be brought into remote classrooms in a “virtual” sense. This study is purposely limited to meteorological radar and is focused on graduate-level education.

Full access
Frank D. Marks Jr.

Abstract

Radar played an important role in studies of tropical cyclones since it was developed in the 1940s. In the last 15 years, technological improvements such as the U.S. National Oceanic and Atmospheric Administration (NOAA) WP-3D tail airborne Doppler radar, the operational Weather Service Radar 1988-Doppler (WSR-88D) radar network, portable Doppler radars, and the first spaceborne radar system on the National Aeronautics and Space Administration Tropical Rainfall Measuring Mission (NASA TRMM) satellite have produced a new generation of tropical cyclone data whose analysis has given scientists an unprecedented opportunity to document the dynamics and rainfall of tropical cyclones, and has led to improved understanding of these devastating storms.

The NOAA WP-3D airborne Doppler datasets led to improved understanding of the symmetric vortex and the major asymmetries. The addition of a second airborne Doppler radar on the other WP-3D enabled true dual-Doppler analyses and the ability to study the temporal evolution of the Kinematic structure over 3–6 h. The advent of the WSR-88D Doppler radar network, and the construction of portable Doppler radars that can be moved to a location near tropical cyclone landfall, has also generated new and unique datasets enabling improved understanding of 1) severe weather events associated with landfalling tropical cyclones, 2) boundary layer wind structure as the storm moves from over the sea to over land, and 3) spatial and temporal changes in the storm rain distribution. The WP-3D airborne Doppler and WSR-88D data have also been instrumental in developing a suite of operational single Doppler radar algorithms to objectively analyze a tropical cyclone's wind field by determining the storm location and defining the primary, secondary, and major asymmetric circulations. These algorithms are used operationally on the WP-3D aircraft and on the ground at NOAA's Tropical Prediction Center/National Hurricane Center.

The WSR-88D rainfall data, together with new satellite microwave passive and active sensors on the NASA TRMM satellite, are proving useful in studies of the temporal and spatial variability of rain in tropical cyclones. The instantaneous satellite snapshots provide rain estimates to improve our understanding of tropical cyclone rain distributions globally, providing estimates from one instrument and common algorithms in each basin, while the WSR-88D provides high-temporal-resolution rain estimates (1 h), to improve our understanding of the temporal variability of the rain as the storm makes landfall.

While these new datasets have led to improved understanding, they have also led to a number of new challenges that the radar meteorology community must face by transferring the understanding gained into new applications and improved numerical weather prediction. These challenges will drive our science well into the next century.

Full access
William R. Cotton

Abstract

A review of convective cloud modeling spanning the period from the days of the NOAA Experimental Meteorology Laboratory (EML) in the late 1960s to 2000 is presented. The intent is to illustrate the evolution of cloud models from the one-dimensional parcel-type models to the current generation of three-dimensional convective storm models and cloud ensemble models. Moreover, it is shown that Dr. Joanne Simpson played a pivotal role in the evolution of cloud models from the very first models to current generation cloud ensemble models. It is also shown that the first concept of the Regional Atmospheric Modeling System (RAMS) began while Drs. Cotton and Pielke worked under Dr. Simpson's supervision at EML. It is then illustrated how far cloud modeling has come with recent applications of RAMS to atmospheric research and numerical weather prediction. The chapter concludes with an outline of the major limitations of current generation convective cloud models.

Full access
Tom Keating

Abstract

The beginnings of the Tropical Rainfall Measuring Mission (TRMM) project are outlined, in particular the role of Joanne Simpson as TRMM study scientist and then TRMM project scientist. Her important work in developing the TRMM science rationale and interacting with our Japanese partners, along with her skill in finding solutions to project problems, is described.

Full access
Robert A. Houze Jr.

Abstract

Joanne Simpson began contributing to advances in tropical convection about half a century ago. The hot tower hypothesis jointly put forth by Joanne Simpson and Herbert Riehl postulated that deep convective clouds populating the “equatorial trough zone” were responsible for transporting heat from the boundary layer to the upper troposphere. This hypothesis was the beginning of a 50-year quest to describe and understand near-equatorial deep convection. Tropical field experiments in the 1970s [Global Atmospheric Research Program Atlantic Tropical Experiment (GATE) and the Monsoon Experiment (MONEX)] in which Joanne participated documented the mesoscale structure of the convective systems, in particular the deep, stratiform, dynamically active mesoscale clouds that are connected with the hot towers. In the 1980s these new data led to better understanding of how tropical mesoscale convective systems vertically transport heat and momentum. The role of the mesoscale stratiform circulation in this transport was quantified. Tropical field work in the 1990s [especially the Coupled Ocean–Atmosphere Response Experiment (COARE), in which Joanne again participated] showed the importance of a still larger scale of convective organization, the “supercluster.” This larger scale of organization has a middle-level inflow circulation that appears to be an important transporter of momentum. The mesoscale and supercluster scale of organization in tropical convective systems are associated with the stratiform components of the cloud systems. Joint analysis of satellite and radar data from COARE show a complex, possibly chaotic relationship between cloud-top temperature and the size of a stratiform precipitation area. The Tropical Rainfall Measuring Mission (TRMM) satellite, for which Joanne served as project scientist for nearly a decade, is now providing a global census of mesoscale and supercluster-scale organization of tropical convection. The TRMM dataset should therefore provide some closure to the question of the nature of deep convection in the equatorial trough zone.

Full access
Gerald R. North

Abstract

It is natural that a book chapter honoring Joanne Simpson draw the connection between the two most important tropical meteorological observing programs in the history of meteorology: the Global Atmospheric Research Program Atlantic Tropical Experiment (GATE) and the Tropical Rainfal Measuring Mission (TRMM). Both programs were dominated by the influences of Joanne Simpson. When TRMM data are all in, these two grand experiments will have given us more information about the behavior of tropical convection and precipitation over the tropical oceans than all other tropical field campaigns combined. But some may not know how GATE data played a key role in demonstrating the feasibility of a mission like TRMM. This chapter will present a review of a number of studies that connect GATE precipitation data with TRMM, especially in the early planning stages.

Full access
Wei-Kuo Tao

Abstract

One of the most promising methods to test the representation of cloud processes used in climate models is to use observations together with cloud resolving models (CRMs). The CRMs use more sophisticated and realistic representations of cloud microphysical processes, and they can reasonably well resolve the time evolution, structure, and life cycles of clouds and cloud systems (size about 2–200 km). The CRMs also allow explicit interaction between outgoing longwave (cooling) and incoming solar (heating) radiation with clouds. Observations can provide the initial conditions and validation for CRM results.

The Goddard Cumulus Ensemble (GCE) model, a cloud-resolving model, has been developed and improved at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center over the past two decades. Dr. Joanne Simpson played a central role in GCE modeling developments and applications. She was the lead author or coauthor on more than 40 GCE modeling papers. In this paper, a brief discussion and review of the application of the GCE model to 1) cloud interactions and mergers, 2) convective and stratiform interaction, 3) mechanisms of cloud–radiation interaction, 4) latent heating profiles and TRMM, and 5) responses of cloud systems to large-scale processes are provided. Comparisons between the GCE model's results, other cloud resolving model results, and observations are also examined.

Full access
Richard A. Anthes

Abstract

This paper describes the exciting period of discovery in the 1950s and 1960s in tropical meteorology, and the important role played by Joanne Malkus (Simpson) in her studies of cumulus convection and tropical cyclones. A key concept developed by Joanne, with Herbert Riehl, was that of the “hot tower.” Hot towers were deep tropical cumulonimbus clouds whose cores were undiluted by entrainment and thus carried heat and water vapor from the boundary layer to high in the troposphere. Joanne's observational work led to a major effort by a number of theoreticians and modelers in the 1960s and 1970s to incorporate the effects of the relatively small-scale but energetically important cumulus clouds in numerical models of tropical cyclones.

The important theory of conditional instability of the second kind, or CISK, and its contribution to tropical cyclone theory and modeling, is summarized. The CISK theory envisioned a cooperation between the tropical cyclone–scale circulation and the much smaller-scale convective clouds, including hot towers, that caused tropical cyclones to form and intensify. Although the CISK and hot tower theories were misunderstood and misused by some, they both contributed much to the development of tropical cyclone models and scientific understanding of these violent storms, and their general concepts and importance remain valid today.

Full access
Isabella Angelini, Michael Garstang, Stephen Macko, Robert Swap, Derek Stewart, and Hillândia B. Cunha

Abstract

Rainwater samples taken every 10 min, protected from fractionation by a hydrocarbon layer and collected every 12 h, are subjected to isotopic analyses to obtain a time series of oxygen and deuterium values through successive rain events in the eastern and central Amazon basin. Satellite imagery is used to characterize the rain events, and rain rates from recording rain gauges are used to delineate changes in internal rain production within each storm.

Three clear isotopic signals are seen in the storm systems examined. These three responses consist of depletion of heavy isotopes by as much as −6.7% in a single storm, depletion followed by enrichment, and little change in the isotopic signal. Each of these changes in isotopic content of the rainwater can be related to the internal rain-rate production, evaporation/condensation processes together with the implied convective/stratiform circulations of the storm. The storm-related isotopic results suggest, in addition to illuminating the internal dynamics of these storm systems, that sampling of rain from any given rain-producing system can yield significantly different isotopic values. Conclusions about the large-scale hydrologic cycle and the sources and pathways followed by water contained within rain must take these internal storm variations in isotopic values into account.

Full access
Roger A. Pielke Jr

Abstract

The role of cumulus clouds in local, regional, and global weather and climate that is understood today is based to a large extent on the pioneering work of Joanne Simpson. Her involvement in this work is illustrated through the experiences as my career developed. She also was, and is, an ideal model of mentorship. This paper illustrates this model using my interactions during the 1970s and early 1980s, and how they have influenced research articles up to the present.

Full access