1. Distribution of Liquid Water in Orographic Mixed-Phase Clouds Diana Thatcher Mentor: Linnea Avallone LASP REU 2011

2. Outline Introduction Experiment Important Instruments 1 st Area of Interest 2 nd Area of Interest Conclusion

3. Orographic Clouds Formed when mountains force moist air upward Variety of interesting structures possible Orographic wave clouds over Long’s Peak

4. Mixed-Phase Clouds Water is present in solid, liquid, and vapor forms Typical temperatures: 0 to –30 ºC –Liquid is supercooled Formed in a variety of situations –Stratiform clouds in polar regions –Frontal systems –Convective cloud systems –Orographic forcing systems

5. Particle Formation Ice particles in areas of supercooled liquid water can undergo: –Riming (growth) –Splintering (multiplication) Affects resulting cloud structure and precipitation Results depend on cloud temperature and saturation

6. Example of a Mixed-Phase Cloud

7. Importance of Study Past studies mainly focus on: – Arctic mixed-phase clouds –Effect of aerosols on mixed phase clouds More knowledge is necessary to create accurate climate models –Complex effects of topography –Microphysics of liquid and solid particle formation Results could aid in the prediction of icing conditions

8. Icing Hazards Supercooled liquid water < 0 ºC Easily freezes to outside of aircrafts –Major difficulties for pilots

9. Colorado Airborne Mixed-Phase Cloud Study (CAMPS) Includes data from instruments on University of Wyoming King Air research aircraft –Numerous sensors –Wyoming Cloud Radar –Wyoming Cloud Lidar Provides in-situ and remote sensing for liquid water, ice crystals, and other microphysical properties

10. Cloud Droplet Spectra - FSSP Forward Scattering Spectrometer Probe Measures particle size distributions Detects how a particle scatters light 2.0 – 47 μm

11. Particle Imaging Instruments 2-D Cloud and Precipitation Probes Measures particle size distribution Image is created from a shadow when particle passes through a laser Pattern recognition algorithms deduce the shape of particle 25 – 800 μm (2-DC) 200 – 6400 μm (2-DP)

12. Icing Indicator Rosemount Icing Detector (Model 871) Detects supercooled liquid water Cylinder vibrates at frequency of 40 Hz –As ice accumulates, the frequency decreases Cylinder is heated to melt ice Process is repeated

13. My Area of Study February 19 th and 20 th, 2011 Area over Muddy Mountain, Wyoming High amounts of snowfall

14. Flight Path 6 levels –3 legs each

15. 1 st Area of Interest Features: Updrafts Small particles Liquid water

16. Radar and Lidar

17. Vertical Wind Velocity

18. Particle Size Distribution Large Particles Small Particles Nearly 100X decrease in mean particle diameter!

19. Liquid Water Content Increase in liquid water content during updrafts, with a slight lag of less than 1 minute Water droplets are much smaller than ice crystals, coinciding with particle size distribution Temperature: -16 °C –Icing conditions

20. 2 nd Area of Interest Over edge of peak Updrafts/Downdrafts Liquid Water Small Particles

21. Radar and Lidar

22. Vertical Wind Velocity

23. Particle Size and Liquid Water Content Increase in small particles Increase in liquid water Again, particle formation processes are at work

24. Conclusion  In mixed-phase clouds, areas of increased liquid water content are likely to occur in areas of strong updrafts, with a slight lag between the peak velocity and peak liquid water content.  Sudden increases in liquid water content are accompanied by a drastic change in the particle size distribution, with a sharp decrease in the concentration of ice crystals and a simultaneous increase in small liquid droplets, indicating the formation of new particles.

25. Future Work Obtain particle image data –Determine ice crystal structures –Determine particle formation processes Expand to a greater variety of cases –Determine limits, such as temperature or vapor saturation –Further analyze the effects of topography

26. Questions?

27. References Hogan, R. J., Field, P. R., Illingworth, A. J., Cotton, R. J. and Choularton, T. W. (2002), Properties of embedded convection in warm-frontal mixed-phase cloud from aircraft and polarimetric radar. Quarterly Journal of the Royal Meteorological Society, 128: 451– 476. doi: 10.1256/003590002321042054 http://www.eol.ucar.edu/raf/Bulletins/B24/fssp100.html http://www.eol.ucar.edu/raf/Bulletins/B24/2dProbes.html http://www.eol.ucar.edu/raf/Bulletins/B24/iceProbe.html

28. Image Sources http://ww2010.atmos.uiuc.edu/%28Gh%29/guides/mtr/cld/dvlp/org.rxml http://www.flickr.com/photos/wxguy_grant/4823374536/ http://www.ucar.edu/news/releases/2006/icing.shtml http://www.askacfi.com/24/review-of-aircraft-icing-procedures.htm http://en.wikipedia.org/wiki/Wikipedia:Picture_of_the_day/September_26,_2006 http://www.cas.manchester.ac.uk/resactivities/cloudphysics/results/riming/ http://www.eol.ucar.edu/raf/Bulletins/B24/fssp100.html http://www.eol.ucar.edu/raf/Bulletins/B24/2dProbes.html http://www.eol.ucar.edu/raf/Bulletins/B24/iceProbe.html