The Use of In Situ Ice Nucleus Measurements in Cloud Seeding Research

The notion that cloud seeding could modify precipitation by jump-starting the cold cloud process created interest in ice nuclei—both natural and anthropogenic—in the middle of the previous century. The discovery of AgI and other materials that function as ice nuclei (IN) subsequently generated the desire to measure IN, to better understand nature, and to produce effective “artificial” materials for cloud seeding. Interest waxed, instruments and methodologies were developed, and conferences on the subject began (Langer 1973a). One of the early instruments was the acoustical ice nucleus counter, then called the “NCAR Counter” (Langer 1973b). Other instruments have followed. DeMott et al. (2011) summarizes the more recent instrumentation. Here, the focus is on the history of the “NCAR Counter”, presently known as the acoustical ice nucleus counter, or AINC. The AINC has been effectively used in airborne and ground-based applications since the 1970s, and use, though limited continues today. Recent deployments in the Wyoming Weather Modification Pilot Project (WWMPP, Breed et al. 2014) and the Seeded and Natural Orographic Wintertime Storms: the Idaho Experiment (SNOWIE, Tessendorf et al. 2019) are reviewed, and implications for future uses discussed.

Breed, D., R. Rasmussen, C. Weeks, B. Boe, and T. Deshler, 2014: Evaluating winter orographic cloud seeding: Design of the Wyoming Weather Modification Pilot Project (WWMPP), J. Appl. Meteor. Climatol., 53, 282-299.

DeMott, P.J. and others, 2011: Resurgence in Ice Nucleus Measurement Research. Bull. Amer. Meteor. Soc., 92, 1623-1635.

Langer, G., 1973a: Analysis of results from the second international ice nucleus workshop with emphasis on expansion chambers, NCAR counters, and membrane filters. J. Appl. Meteor, 12, 991-999.

Langer, G., 1973b: Evaluation of the NCAR ice nucleus counter, Part I, Basic operation. J. Appl. Meteor, 12, 1000-1011.

Tessendorf, S. et al., 2019: A transformational approach to winter orographic weather modification research: the SNOWIE Project. Bull. Amer. Meteor. Soc., 100, 71-92.