James Wilson (ATD) and Roger Wakimoto (University of California, Los Angeles)

Andrew Crook (MMM/RAL). Co-authors, Mitchell Moncrieff (MMM), Richard Carbone ( ATD), and John Conway (University of Oklahoma)

For his leading role in the two papers.

Andrew Crook (MMM/RAL); cowriters, Terry Clark and Mitchell Moncrieff

This paper summarizes research conducted as part of a three-year project on extreme events and climate change, demonstrating how thes tatistical theory of extremes can be exploited in climate applications.

Jothiram Vivekanandan (Research Applications Program), Joseph Turk (Colorado State University), and V. N. Bringi (CSU)

The problem of measuring precipitation from space is examined through use of NASA's AMPR instrument and NCAR's CP-2 multiparameter radar during the Convection and Precipitation/Electrification Experiment in central Florida. Vast regions of the globe have inadequate ground-based measurements of precipitation. The CP-2 data are used in this paper to infer particle size, shape, and composition within convection; these variables are then compared to radiometer-derived brightness temperature. This, the first paper to show AMPR's potential to study microphysics within convective storms, is a pioneering effort toward classifying and measuring global precipitation using satellite-based instruments.

This paper combines observations from Doppler radars, aircraft, atmospheric soundings, and a mesonetwork with cloud photographs and numerical simulations to describe how various scales of meteorological phenomena interact to produce thunderstorms. The findings are important for the short-term forecasting of thunderstorm activity. Other researchers have since applied these results to the formation of thunderstorms at the intersections of sea-breeze fronts and boundary-layer rolls.

Larry Cornman, Gary Cunning, and Corinne Morse

This paper presents a new concept for automated, quantitative measurements of atmospheric turbulence: the use of commercial aircraft as turbulence-sensing platforms whose data can be assembled and processed in real time at a ground site. The vertical accelerations of an aircraft, routinely measured in flight, can be used to infer the turbulent forces producing up-and-down motions. By adopting simplifications to this highly complex mathematical and physical problem, the authors produced an algorithm that can be easily implemented on any aircraft. The technique is being deployed on over 200 United Airlines aircraft in the next few months. Along with its potential for real-time detection and warning, the algorithm also promises to give scientists a wealth of data for research on the structure of atmospheric turbulence.

Roy Rasmussen, Ben Bernstein, and Greg Stossmeister. Co-nominees and co-authors included Masataka Murakami (Meteorological Research Institute, Tsukuba, Japan), Jon Reisner (Los Alamos National Laboratory) and Boba Stankov (NOAA).

Shallow upslope storms, which develop along the Front Range two to six times per year and last from three to four days each, are of great interest to atmospheric scientists as well as to pilots. The storms' relatively warm cloud tops allow droplets to remain unfrozen for long periods, posing a significant aviation hazard. This study examines a 1990 storm in detail, showing the dynamical and microphysical mechanisms that led to long-lived regions of supercooled liquid water and freezing drizzle aloft. These mechanisms include upper-level jet streaks, which can help suppress vertical development of the precipitation, and sequential surges of cold air, which at first hasten but eventually diminish the production of supercooled liquid water. Insights from this and later work have led to improved pilot training, better algorithms of in-flight icing, and improved paramaterization of supercooled liquid water in mesoscale models.

James Wilson and Daniel Megenhardt 

Using 32 days of data from the Convection and Precipitation/Electrification (CaPE) field project in Florida, this paper shows how the area's longer-lived multicellular storms - those more likely to cause serious damage - are sustained. Analysis shows that the formation and duration of these storms is related to the vertical wind shear and storm motion relative to two recurring boundaries, the East Coast Sea Breeze Front and the West Coast Front. By calculating the boundary-relative cell motion, forecasters can use these findings to improve storm forecasts, including those issued by automated systems. This represents a fundamental advance in short-term storm forecasting, with the findings already being applied in New Mexico, Alabama, Virginia, and Australia.

Roy Rasmussen, Jothiram Vivekanandan, and Jeff Cole. Co-authors included: M. Kuperman (United Airlines, San Francisco, CA), Barry Myers (Transport Canada, Montreal, Quebec), and Charles Masters (FAA, Atlantic City, NJ). 

A combination of five years of fundamental research and practical application went into these papers, which analyze a series of aircraft accidents that involved inadequate deicing. The authors found that the standard relationship between snowfall intensity and visibility that is used by many weather services can be misleading because of variations in snow type and differences in how visibility is affected by snowfall during the day versus the night. Because of this work, airlines have improved the procedures they use to estimate snowfall rates.