A Cloud Physics Facility for DUSEL

1. A Cloud Physics Facilityfor DUSEL John Helsdon South Dakota School of Mines & Technology & Patrick Chuang Univ. of California – Santa Cruz

2. Big Question 2001 National Research Council Report • Examined Key Questions in Climate Science • 60% of Climate Sensitivity Due to Feedbacks Involving: • Water vapor • CLOUDS Conclusion: • Climate Uncertainty Will Remain Until a More Fundamental Understanding of Clouds is Achieved

3. Clouds and Climate Key Component of Climate System. Clouds Affect: • Incoming Sunlight • Outgoing Longwave IR • Vertical Transport of Energy, Moisture, Trace Gases • Precipitation in All Forms (Including Cleansing) • Atmospheric Chemistry • SO2 oxidation to SO4 in cloud droplets • Nitrogen fixation by lightning

4. Laboratory Studies Well-controlled Unrealistic length scales and residence times Field Studies Realistic conditions Poorly-controlled Difficult sampling conditions (aircraft) Expensive Model Studies Well-controlled, detailed results Need to be tested and validated against observations Vertical Shaft Studies Reasonably well-controlled Reasonably realistic length scales and residence times Easier sampling conditions Particles at terminal velocity Environments for Studying Clouds

6. Precipitation Formation • How Does Precipitation Form in Clouds? • Initiation of precipitation in warm clouds is a longstanding problem in cloud physics • Ice phase interactions are primary path to precipitation, but poorly understood • Vertical shaft cloud would permit testing of central hypotheses, such as the role of aerosol distributions, turbulence, electrical effects, temperature, etc.

7. Aerosol-Cloud Interactions • What are Properties of Clouds Formed From Aerosols Composed of Mixture of Organic and Inorganic Compounds? • Activation behavior of organic aerosols poorly understood • Vertical shaft cloud permits controlled experiments with complex aerosol (e.g., biomass burning, combustion aerosol) in realistic cloud conditions

8. Cloud Electrification Studies • Ice Particle Interactions in Supercooled Cloud Environment Thought to Cause Charge Separation up to Lightning • Many types of ice particles in natural cloud • Interaction coefficients poorly defined • Vertical shaft cloud with mixed-phase water environment and detailed observations will help resolve interaction matrix

9. Cloud-Turbulence Interactions • How Does Turbulence Affect the Evolution of Cloud Properties? • Microscale turbulence (~ mm to cm length scales) hypothesized to affect cloud processes such as condensation, collision-coalescence/aggregation, radiative transfer, but experimental data lacking • Vertical shaft cloud exhibits higher Reynolds numbers than achieved in laboratory conditions, permitting better experimental data to address questions

10. Cloud Chemistry • How do Models of Aqueous Phase Chemistry in Clouds Compare with Measurements? • Conversion of S(IV) to S(VI) well known to be important for atmospheric chemistry • Reactions involving other species also believed to be significant • Vertical shaft cloud would provide real cloud conditions on timescales sufficiently long to study such reactions

11. Other Studies • Cloud Remote Sensing • Cloud Radiative Transfer • Instrument Inter-comparison • Adiabatic Parcel Models • Multi-Dimensional Simulation Models

12. It is Fitting that a Cloud Physics Facility Should be Associated with a Particle Physics Facility.One of the Original Particle Physics Detectors was the Wilson Cloud Chamber.