Search Results

You are looking at 51 - 55 of 55 items for

  • Author or Editor: Peter T. May x
  • All content x
Clear All Modify Search
Peter T. May, James H. Mather, Geraint Vaughan, Keith N. Bower, Christian Jakob, Greg M. McFarquhar, and Gerald G. Mace
Full access
Peter T. May, James H. Mather, Geraint Vaughan, Christian Jakob, Greg M. McFarquhar, Keith N. Bower, and Gerald G. Mace

A comprehensive dataset describing tropical cloud systems and their environmental setting and impacts has been collected during the Tropical Warm Pool International Cloud Experiment (TWPICE) and Aerosol and Chemical Transport in Tropical Convection (ACTIVE) campaign in the area around Darwin, Northern Australia, in January and February 2006. The aim of the experiment was to observe the evolution of tropical cloud systems and their interaction with the environment within an observational framework optimized for a range of modeling activities with the goal of improving the representation of cloud and aerosol process in a range of models. The experiment design utilized permanent observational facilities in Darwin, including a polarimetric weather radar and a suite of cloud remote-sensing instruments. This was augmented by a dense network of soundings, together with radiation, flux, lightning, and remote-sensing measurements, as well as oceanographic observations. A fleet of five research aircraft, including two high-altitude aircraft, were taking measurements of fluxes, cloud microphysics, and chemistry; cloud radar and lidar were carried on a third aircraft. Highlights of the experiment include an intense mesoscale convective system (MCS) developed within the network, observations used to analyze the impacts of aerosol on convective systems, and observations used to relate cirrus properties to the parent storm properties.

Full access
Deepak K. Rajopadhyaya, Peter T. May, Robert C. Cifelli, Susan K. Avery, Christopher R. Willams, Warner L. Ecklund, and Kenneth S. Gage

Abstract

Two different frequency radar wind profilers (920 and 50 MHz) were used to retrieve rain rates from a long-lasting rainfall event observed near Darwin, Northern Territory, Australia, during the 1993–94 wet season. In this technique, 50-MHz data are used to derive the vertical air motion parameters (vertical velocity and spectral width); the 920-MHz data are then used to obtain the precipitation characteristics with the vertical air motion corrections. A comparison of the retrieved rain rates with rain gauge measurements shows excellent agreement. A detailed examination of the mean vertical velocity and spectral width corrections in the rain retrieval shows that the error due to an uncorrected mean vertical velocity can be as large as 100%, and the error for an uncorrected spectral width was about 10% for the range of mean vertical velocity and spectral width considered. There was a strong functional dependence between the retrieved mean vertical velocity and percentage difference between observed and retrieved rain rates with and without vertical air motion corrections. The corresponding functional dependence with and without the spectral width corrections was small but significant. An uncorrected upward mean vertical velocity overestimates rain rates, whereas an uncorrected downward mean vertical velocity underestimates rain rates. Uncorrected spectral width estimates have a tendency to overestimate rain rates. There are additional errors in the width correction because of antenna beam mismatching. A method is discussed to quantitatively evaluate this effect, and it is shown to be relatively small compared to the first-order mean vertical velocity correction.

Full access
Peter T. May, Thomas D. Keenan, Rod Potts, James W. Wilson, Rob Webb, Andrew Treloar, Elly Spark, Sue Lawrence, Elizabeth Ebert, John Bally, and Paul Joe

Abstract

The Sydney 2000 Olympic Games World Weather Research Programme Forecast Demonstration Project (WWRP FDP) aimed to demonstrate the utility and impact of modern nowcast systems. The project focused on the use of radar processing systems and products for nowcasting, including severe weather. The forecast problems facing the Australian Bureau of Meteorology (BoM) on these short timescales during the FDP are briefly described. The observing system is then discussed and enhancements to the network that supported the Olympic Games forecast requirements and the WWRP FDP project are outlined. In particular, issues related to radar calibration and quality control are discussed in some detail. The paper concludes with a brief discussion on the observing system requirements to meet such modern nowcast systems, areas of further development, and impacts that the FDP had on BoM nowcasting systems. The need for end-to-end design of systems from data gathering, to analysis and product generation is emphasized.

Full access
Sarah A. Tessendorf, Roelof T. Bruintjes, Courtney Weeks, James W. Wilson, Charles A. Knight, Rita D. Roberts, Justin R. Peter, Scott Collis, Peter R. Buseck, Evelyn Freney, Michael Dixon, Matthew Pocernich, Kyoko Ikeda, Duncan Axisa, Eric Nelson, Peter T. May, Harald Richter, Stuart Piketh, Roelof P. Burger, Louise Wilson, Steven T. Siems, Michael Manton, Roger C. Stone, Acacia Pepler, Don R. Collins, V. N. Bringi, M. Thurai, Lynne Turner, and David McRae

As a response to extreme water shortages in southeast Queensland, Australia, brought about by reduced rainfall and increasing population, the Queensland government decided to explore the potential for cloud seeding to enhance rainfall. The Queensland Cloud Seeding Research Program (QCSRP) was conducted in the southeast Queensland region near Brisbane during the 2008/09 wet seasons. In addition to conducting an initial exploratory, randomized (statistical) cloud seeding study, multiparameter radar measurements and in situ aircraft microphysical data were collected. This comprehensive set of observational platforms was designed to improve the physical understanding of the effects of both ambient aerosols and seeding material on precipitation formation in southeast Queensland clouds. This focus on gaining physical understanding, along with the unique combination of modern observational platforms utilized in the program, set it apart from previous cloud seeding research programs. The overarching goals of the QCSRP were to 1) determine the characteristics of local cloud systems (i.e., weather and climate), 2) document the properties of atmospheric aerosol and their microphysical effects on precipitation formation, and 3) assess the impact of cloud seeding on cloud microphysical and dynamical processes to enhance rainfall. During the course of the program, it became clear that there is great variability in the natural cloud systems in the southeast Queensland region, and understanding that variability would be necessary before any conclusions could be made regarding the impact of cloud seeding. This article presents research highlights and progress toward achieving the goals of the program, along with the challenges associated with conducting cloud seeding research experiments

Full access