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Chuntao Liu Department of Atmospheric sciences, University of Utah Contributors:

Correlations between LIS lightning and characteristics of convective “cells” in tropical thunderstorms. Chuntao Liu Department of Atmospheric sciences, University of Utah Contributors: Edward Zipser 1 , Daniel Cecil 2 , Michael Peterson 1 1. University of Utah

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Chuntao Liu Department of Atmospheric sciences, University of Utah Contributors:

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  1. Correlations between LIS lightning and characteristics of convective “cells” in tropical thunderstorms Chuntao Liu Department of Atmospheric sciences, University of Utah Contributors: Edward Zipser1 , Daniel Cecil2, Michael Peterson1 1. University of Utah 2. University of Alabama at Huntsville

  2. Questions to address • How often does lightning flash occur in anvil and stratiform region of storms? • What properties of precipitation systems observed from radar and microwave radiometers have the best correlations with the flash rate? • And the most intriguing one: why lightning flashes are so rare over ocean?

  3. Q1: How often does lightning flash occur in anvil and stratiform region of storms? Lightning flashes (ICs, CGs) happen both inside and outside convective regions (“cells”), sometimes in stratiform regions, or anvil regions

  4. Find convective “cells” (regions) in precipitation systems • Two “cell” definitions: • Convective pixels • (red color fill) • 30 dBZ pixels at 6 km (white line)

  5. Simple statistics of convective regions From 12 year TRMM observations (1998-2009 )

  6. Lightning flashes in anvil and stratiform regions Anvil flash: No surface rainfall Stratiform flash: In stratiform area

  7. Simple statistics of flashes in anvil and stratiform regions 1998-2010 within TRMM PR swath

  8. Global distribution of flashes in anvil and stratiform regions Stratiform/convective separation problem over high terrains Artifacts due to the Southern Anomaly

  9. Diurnal variation of flashes in anvil and stratiform regions See detail in Peterson and Liu (2011) submitted to JGR

  10. Q2: What properties of precipitation systems observed from radar and microwave radiometers have the best correlations with the flash rate? Flash rate vs. properties of precipitation systems More ice in the charging zone from -10oC to -20oC  more charge separation  higher flash rate From radar and radiometers: Higher reflectivity at altitudes Lower microwave brightness temperature (Williams et al., 1987 JGR, Lang et al 2000 MWR, Toracinta et al. 2002 MWR Cecil et al. 2005 MWR … ) Updraft volume  flash rate Mass flux of ice in mixed-phase region  flash rate (Deierling et al. 2008, Deierling and Petersen, 2008 JGR)

  11. Past studies on Flash rate vs. properties of precipitation systems

  12. First look at Microwave Radiometer (TMI) TPFs are defined by grouping area with TRMM 2A12 rain from TMI Note: the minimum flash rate LIS can measure is ~ 1 flash/minute

  13. Population of TPFs and those with flashes

  14. Population of TPFs and those with flashes

  15. Correlations to flash rate from 85 and 37 GHz PCTs 85 GHz PCT ≈ Ice Water Path 37 GHz PCT ≈ amount of large ice particles

  16. Flash rate vs. properties of 85 GHz PCTs and 37 GHz PCTs

  17. Correlations to flash rate Better with cold TB area Better over land

  18. A short Summary • It is not the maximum amount of ice at one location, but the total amount of ice through the charging zone that lead to higher flash rate. Therefore, areas of cold microwave TB are better correlated to the flash rate than the minimum TB. • Better correlation over land

  19. Now let’s look at Radar Parameters to look at: Maximum height of 20, 30, 40 dBZ Temperature at these echo tops Maximum reflectivity at altitudes Area of 20, 30, 40 dBZ at altitudes Area of 20, 30, 40 dBZ at temperatures Volume of 20, 30 40 dBZ at -5oC - -30oC

  20. RPFs defined by using 2A25 raining area by PR • 1998-2010 With at least 4 contiguous pixels ( ~ 80 km2)

  21. Correlation coefficient to flash rate in precipitation features Echo top height/temperature vs. Flash rate

  22. Correlation coefficient to flash rate in precipitation features maximum reflectivity at altitudes vs. Flash rate

  23. Correlation coefficient to flash rate in precipitation features area of reflectivity at temperatures vs. Flash rate

  24. Volume of reflectivity in charging zone vs. Flash rate Correlation coefficient to flash rate in precipitation features

  25. Better correlation to the area of high reflectivity at charging zone

  26. Better correlation to the volume of high reflectivity in the charging zone

  27. More flash yield per volume of high reflectivity over land

  28. A short Summary • It is neither how deep the convection can reach, nor how much ice in the convection, but the volume with the large ice particles and high reflectivity in the mixed phase region that best correlate to the flash rate. • More flashes generated over land than over ocean given the same volume of 30-35 dBZ in the charging zone.

  29. Q3: why lightning flashes/thunderstorms are so rare over ocean? What kind of systems are we disappointed that they do not have lightning?

  30. Those without flashes share same vertical structure over both land and ocean

  31. Ocean with vs. without flashes

  32. Occurrence of reflectivity at altitudes and temperatures

  33. Occurrence of reflectivity at temperatures land/ocean

  34. 2D histogram of PFs and their probability with lightning 90% 75% 50% 75% 25% 50% 10% 25% 5% 10% 1% 5% 1%

  35. 2D histogram of PFs and their probability with lightning More large ice particle More large ice particle More ice More ice

  36. Conclusions • Flash rate is best correlated with the volume of the high reflectivity (> 30 dBZ) in the mixed phase region, indicating the importance of the presence of large particles in the charging process. • Ocean storms are lack of the high reflectivity (large ice particles) in the mixed phase region. • More flashes are generated over land than over ocean given the same volume of 30-35 dBZ in the charging zone.

  37. Speculations • Land stronger updraft  help lifting large particles stronger updraft + more aerosols  more likely to have super cooled liquid water helping charge separation stronger updraft  wider spectrum of size distribution of ice particles with higher collision efficiency in charge separation • Ocean less total water content due to efficient warm rain process weaker updraft  large particles fall out easier weaker updraft + less aerosols  less super cooler liquid water weaker updraft  narrower spectrum of size distribution of ice particles with lower collision efficiency in charge separation

  38. Thank you!!! • Questions?

  39. Backup slides

  40. Properties of TPFs with flashes

  41. Median properties of TPFs with flashes

  42. Marginal properties of TPFs with flashes

  43. Flash rate vs. properties of 85 GHz PCTs and 37 GHz PCTs

  44. Seasonal variation of correlations from area with low PCTs to flash rate

  45. Seasonal variation of correlations from area with low PCTs to flash rate

  46. Line fit from area with low PCTs to flash rate

  47. Radar

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