The winners of the 18th Professor Vilho Vaisala Award at WMO are three scientists of the Paul Scherrer Institute, Switzerland, for their paper entitled “Hygroscopicity of Aerosol Particles at Low Temperatures. New Low-Temperature H-TDMA Instrument: Setup and First Applications ”. The award ceremony was held in October, 2003 at the WMO headquarters in Geneva. Prof. G. O. P. Obasi, Secretary-General of the WMO, presented the award to Dr. Urs Baltensperger, Dr. Martin Gysel and Dr. Ernest Weingartner.
At the ceremony, Prof. Obasi underlined in his statement the importance of the newly developed instrument for the Global Atmosphere Watch (GAW) of WMO, a program that monitors the chemical composition of the atmosphere with the aim of providing a database of the changes caused by natural and anthropogenic influences. Such information is essential for studies on climate change, the ozone layer, and pollutants. In this context atmospheric aerosols also play an important role.
The new instrument investigates how aerosol particles change their size when they are transferred from dry conditions to a well-defined higher relative humidity. The instrument introduces the ability to perform measurements in sub-zero conditions, which will provide new insights into aerosol behavior and cloud formation under sub-zero temperatures in the atmosphere. Moreover, Prof. Obasi also stressed in his statement the contribution of the Paul Scherrer Institute (PSI), which is a multi-disciplinary research center for natural sciences and technology, and the largest national research institute in Switzerland.
The winning paper “Hygroscopicity of Aerosol Particles at Low Temperatures. New Low-Temperature H-TDMA Instrument: Setup and First Applications” was published in Environmental Science & Technology, Vol. 36, 55 -62, 2002. In this paper Dr. Urs Baltensperger, Dr. Martin Gysel and Dr. Ernest Weingartner present a new instrument, the Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA), that allows the water uptake of submicrometer aerosol particles to be determined at temperatures below 0°C. The instrument can be used for determining the hygroscopic growth of aerosol particles at sub-zero temperatures. In addition to describing the instrument’s development, operation principle and characteristics, the paper also discusses field tests and applications of the method, as well as comparing the theory with laboratory measurements.