Obituary notice for Emeritus Professor Isztar Zawadzki (1939 – 2023)

– By Jacques Derome, Frédéric Fabry, Henry Leighton and Man K. (Peter) Yau –

On February 11th, 2023, Emeritus Professor Isztar Zawadzki, internationally known for his ground-breaking work in radar meteorology and precipitation physics, succumbed to a stroke. With great effort, determination and much help from his life partner, Dominique, he had well recovered from a first stroke three years earlier, but this second one surpassed his resilience.

Dr. Zawadzki was born in Poland on February 9th, 1939. Fearing the mounting ravages of antisemitism and the war, his mother fled with her toddler to Russia and then departed for Argentina. It is there, at the University of Buenos Aires, that he completed a Licenciado en Ciencas Fisicas. Having developed an interest in radar meteorology and in the formation and prevention of hail, he decided to enrol in graduate studies in the Department of Meteorology (now Atmospheric and Oceanic Sciences) at McGill University, obtaining his Ph.D. in 1972 under the supervision of Professor Roddy R. Rogers.

Isztar began his academic career in the Physics Department of the recently created Université du Québec à Montréal where he was a moving force behind the creation of a graduate program in meteorology. In 1992, McGill University recruited him as Director of the Stewart Marshall Radar Observatory within the Department of Atmospheric and Oceanic Sciences, a wise move indeed, as it ushered in a period of rapid expansion of the radar activities in a leading research and operational Observatory worldwide. His warm personality and contagious enthusiasm for science made him a magnet for graduate students and led to a multitude of visitors and post-doctoral fellows to the radar lab from around the world.

Isztar published more than 117 papers. His research spanned a wide range of innovative applications of weather radar data and the study of cloud physics processes. His first research axis was to further our understanding of the complex processes involved in the formation and distribution of winter and summer precipitation: he studied drop growth, riming, secondary-ice formation and melting with vertically pointing radars and in-situ sensors, correctly interpreting results thanks to a great physics intuition, and reproducing them by numerical modeling while gathering new insights. His research on hydrometeor size distributions also led him to experiment with moment normalization. Since the distribution of drop sizes shapes the reflectivity measured by radar, some of his earlier work examined the effects of changing drop size distributions on precipitation estimation accuracy. This work was recently republished at the European Radar conference as an example of foresight, clarity of thinking, and good science. Improving rainfall measurements by radar also found important applications in hydrology. When he joined McGill, after leading the conversion of its radar to have Doppler capabilities, he developed a new line of work, how to best use the information from radar data to improve numerical modelling. He first explored how to retrieve 3D winds and later thermodynamics first from a single Doppler radar and then also using bistatic receivers. Isztar then experimented with the assimilation of radar data using traditional and then novel assimilation techniques. Finally, in parallel, he championed the improved use of radar data for operational and research uses, whether the task was better cleaning radar data, making possible the development of the refractivity measurements by radar, or developing MAPLE (McGill Algorithm for Precipitation Nowcasting by Lagrangian Extrapolation) for radar nowcasts, often using those efforts as leads for new research. His noteworthy work on the scale-dependence of precipitation predictability resulted directly from trying to improve precipitation nowcasts and forecasts. He also led a last upgrade of the McGill radar to make it the first known operational dual-polarization radar in the world. Isztar had a knack for foreseeing interesting research avenues and for how to organize initial efforts to advance research goals. The recent expansion in the infrastructure and the use of radar for operational meteorology in Canada owes much to the work of his group at McGill.

In recognition of his numerous scientific achievements Isztar was awarded the Patterson Medal of the Meteorological Service of Canada (1991) and the CMOS President’s Prize (1998); he was made a Fellow of the Canadian Meteorological and Oceanographic Society (2001) and of the American Meteorological Society (2004). In 2007, he was the first recipient of the AMS Remote Sensing Prize, the recipient of the Luis Federico Leloir Award for International Cooperation in Science, Technology, and Innovation and was inducted into the Academy of Science of the Royal Society of Canada.

Isztar had wide-ranging interests beyond science, including music – he personally crafted wooden flutes and played them in a South-American-type band in the 1970s, as well as horticulture – he devotedly attended to his garden and trees at his mini-farm, and sculpture, an art that he enjoyed as he recovered from his first stroke.

Isztar’s warm personality will be missed by the love of his life, Dominique Robert, his former students, who remained important to him to the end, and a multitude of colleagues and friends worldwide.