Distribution of Liquid Water in Orographic Mixed-Phase Clouds

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

2. Outline • Introduction • Experiment • Important Instruments • 1st Area of Interest • 2nd 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 Instruments2-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 19th and 20th, 2011 • Area over Muddy Mountain, Wyoming • High amounts of snowfall

14. Flight Path 6 levels • 3 legs each

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

16. Radar and Lidar

17. Vertical Wind Velocity

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

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. 2nd 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