Idaho Power’s Cloud Seeding Case Studies April 2, 2021 Derek Blestrud Senior Atmospheric Scientist Presentation Outline • What is cloud seeding • How cloud seeding is conducted • SNOWIE Research project What is cloud seeding? • Cloud seeding of cold clouds depends upon an abundance of supercooled liquid water (SLW) • Cloud seeding of warm clouds depends upon Collision‐ Coalescence • Cloud seeding provides a mechanism to promote the growth of either a raindrop (warm cloud) or snowflake (cold cloud) • The term cloud seeding has been used to describe: – Fog suppression (airports) – Hail suppression (reduce crop and property damage) – Rainfall enhancement (water supply augmentation) – Snowpack enhancement (snowpack augmentation) Supercooled Liquid Water (SLW) • Water that is cold enough to freeze, but remains in the liquid state – Water can freeze at 32°F – Water requires a nucleation process to freeze • Impurities in nature such as dust – Water in the liquid state can be present in clouds much colder than 32°F • Often down to 0°F or even colder How does a snowflake/raindrop develop? (Cold Cloud) Cold Cloud Seeding Method • Glaciogenic Seeding – Conducted in clouds cold enough to promote growth of ice. – Seeding Agents • Silver Iodide • Dry Ice • Liquid Propane (expands into gas form) Winter Orographic Cloud Seeding • Cloud seeding provides additional efficient ice nuclei that function at warmer temperatures, allowing ice formation to begin sooner • This occurs at temperatures as warm as 23°F, though more effectively at 17oF or colder • Natural ice nuclei become effective below 5oF . First Ice, not seeded Image Courtesy of the Weather Modification International Winter Orographic Cloud Seeding • Cloud seeding provides additional efficient ice nuclei that function at warmer temperatures, allowing ice formation to begin sooner • This occurs at temperatures as warm as 23°F, though more effectively at 17oF or colder • Natural ice nuclei become effective below 5oF . First Ice, seeding First Ice, not seeded Image Courtesy of the Weather Modification International Seeding Mechanisms Burn Head Temperature Probe Ignition Coil Valve Box Satellite Communication Tower Solar Panel Computer Box Nitrogen Solution Tanks Work Platform Batteries Propane Remote Cloud Seeding Generator Seeding Mechanisms Modified Aircraft SNOWIE Seeded & Natural Orographic Wintertime clouds: the Idaho Experiment • National Science Foundation funded SNOWIE to study winter precipitation processes ($2.1M) • Field campaign early 2017 (Jan. – March), focus on Payette Basin • Goal: – further understand natural and dynamic winter precipitation processes – determine physical processes by which cloud seeding effects winter precipitation • Field Effort: – Over 75 additional instruments (research aircraft, ground based instruments) – 4 PI’s, 11 scientists operating instruments and analyzing data • Results will directly benefit weather modeling over complex terrain SNOWIE Seeded & Natural Orographic Wintertime clouds: the Idaho Experiment • Collaborative effort between: – National Center for Atmospheric Research (NCAR) – University of Wyoming – University of Colorado, Boulder – University of Illinois – Idaho Power Company • Additional Efforts – BSU – silver sampling – WMI ‐ Research seeding aircraft – WMI ‐ Ice nuclei counter UW King Air with profiling radar and lidar time UTC Snow Bank DOW 2º elevation 19 Jan 2017 1641 1648 1653 1700 1705 1712 1718 1724 1730 1736 1741 1748 1753 1800 1806 1812 seeding aircraft flies King Air flight track two seeding legs seeding flight track (burn-in-place flares) Packer John DOW7 RHIs along UWKA track (downwind) 19 Jan 2017 1707 1727 1749 terrain clutter 1709 1731 1751 1713 1733 1755 1715 1737 1757 1719 1739 1801 1721 1743 1803 1725 1745 snow cloud liquid cloud tops (~-16ºC) snow cloud snow cloud liquid cloud tops (~-16ºC) snow cloud blue: total water black: liquid water flight-level data (liquid + frozen) snow snow liquid total water ( g m- 3) snow liquid ) 3 water ( g m g ( water liquid - liquid water ( g m- 3) snow liquid ) 3 water ( g m g ( water total - liquid water ( g m- 3) snow snow liquid ) 3 water ( g m g ( water total - liquid water ( g m- 3) snow snow liquid ) 3 water ( g m g ( water total - total water ( g m- 3) snow snow ~30 km ) 3 water ( g m g ( water liquid - total water ( g m- 3) ) 3 water ( g m g ( water liquid - Original Cloud Seeding Racetrack Experiment Photo Courtesy of Dr. Vincent Schaefer NCAR airborne seeding simulator flight track SNOWIE IOP Seeded and Natural Orographic Wintertime clouds ‐ the Idaho Experiment Intensive Observation Period 19 Jan 2017 Questions?.