NSSL Hot Item

NSSL scientists receive NOAA and OAR awards

2010 NOAA Distinguished Career Award

For Sustained Career Excellence

Robert Davies-Jones

For scientific achievements in the application of observations and theory to the understanding of the dynamics of severe convective storms and tornado genesis mechanisms.

Davies-Jones (retired) has had an impactful 38-year career with the lab, sharing his tornado expertise with the world.

Davies-Jones emigrated to the U.S. from England in 1964, started his career with NSSL in 1970, and obtained U.S. citizenship in 1983. He is a world-renowned expert on tornadogenesis, tornado flows, thunderstorm updrafts, short-term mesocyclone prediction, estimation of maximum tornado parameters, and vorticity dynamics of larger-scale meteorological flows. Davies-Jones’ has contributed to the profession as a meteorological journal editor, co-chair of conferences, student advisor, expert consultant, Principal Investigator on projects, and has served on scientific committees. He has the rare ability to simplify research results communicated in newspaper interviews, magazines, encyclopedias, popular articles, and on TV.

Davies-Jones’ colleagues have this to say:

“He came in as a gifted theoretician and continued to make important contributions to our understanding of tornadogenesis, in particular, from a theoretical perspective. On top of that, he became really good at the technical aspect of collecting data in field projects. DJ wasn’t a storm chaser who became theoretically gifted; he was a gifted theoretician who became a storm chaser to collect data to help him and others in their theoretical work. “(Harold Brooks)

“Bob has been an important member of the Lab in many ways (theoretician, storm intercept leader, solid citizen, and friend to student and scientist alike) for many years. I greatly respect Bob for his scientific/mathematical understanding and his ability to communicate complicated dynamic/mathematical concepts to those with lesser understanding. Bob’s expenditure of effort, his calm-amid-chaos leadership, and his patience and understanding have been huge components in NSSL’s Storm Intercept Program over the many years. The level of respect he enjoys within the severe storm community has long been a part of NSSL’s position as leader in scientific research.” (Don Burgess)

“I am especially impressed that, as a theoretician, Bob wants to find out about the phenomena that he models. Consequently, he has taken a very active role in storm intercept field programs so he can see first-hand how nature behaves. He will be missed because he is NSSL’s primary resource person for explaining the theoretical underpinnings of severe storm phenomena, especially tornadoes.” (Rodger Brown).

“Bob is a complete scientist in that he contributes to the advancement of science in multiple ways. He develops new theory, enhances understanding through observations he participates in collecting, and provides the scientific underpinning for applications that improve operational meteorology. His article on tornadoes in Scientific American was a masterpiece in helping the non- meteorologist understand the complexity of tornado genesis. We at NSSL are grateful for the 38 years he has spent among us.” (Jeff Kimpel, former NSSL Director)

2011 Outstanding Scientific Paper

Mr. M.R. Kumjian and Dr. A. V. Ryzhkov

Storm-Relative Helicity Revealed from Polarimetric Radar Measurements. Journal of the Atmospheric Sciences, 66, 667-685

The dual-polarization radar variables are especially sensitive to the microphysical processes of melting and size sorting of precipitation particles. In deep convective storms, polarimetric measurements of such processes can provide information about the airflow in and around the storm that may be used to elucidate storm behavior and evolution. Size sorting mechanisms include differential sedimentation, vertical transport, strong rotation, and wind shear. In particular, winds that veer with increasing height typical of supercell environments cause size sorting that is manifested as an enhancement of differential reflectivity (ZDR) along the right or inflow edge of the forward-flank downdraft precipitation echo, which has been called the ZDR arc signature. In some cases, this shear profile can be augmented by the storm inflow. It is argued that the magnitude of this enhancement is related to the low-level storm-relative environmental helicity (SRH) in the storm inflow.

To test this hypothesis, a simple numerical model is constructed that calculates trajectories for raindrops based on their individual sizes, which allows size sorting to occur. The modeling results indicate a strong positive correlation between the maximum ZDR in the arc signature and the low-level SRH, regardless of the initial drop size distribution aloft. Additional observational evidence in support of the conceptual model is presented. Potential changes in the ZDR arc signature as the supercell evolves and the low-level mesocyclone occludes are described.