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Cloud microphysics and precipitation through the eyes of METEOSAT SECOND GENERATION (MSG)

Thomas Heinemann Meteorological Products Expert Thomas.Heinemann@eumetsat.int www.eumetsat.int Contributors: J. Kerkmann(EUM), D. Rosenfeld (HUJ), J. Prieto (EUM). Cloud microphysics and precipitation through the eyes of METEOSAT SECOND GENERATION (MSG). 7. Cloud Particle Size.

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Cloud microphysics and precipitation through the eyes of METEOSAT SECOND GENERATION (MSG)

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  1. Thomas Heinemann Meteorological Products Expert Thomas.Heinemann@eumetsat.int www.eumetsat.int Contributors: J. Kerkmann(EUM), D. Rosenfeld (HUJ), J. Prieto (EUM) Cloud microphysics and precipitation through the eyes ofMETEOSAT SECOND GENERATION (MSG)

  2. 7. Cloud Particle Size Picture from Bob White

  3. Observing Cloud Particle Size MFG: not possible ( only cloud thickness and cloud top temperature) • MSG: possible ( 2 NIR window channels) • NIR1.6 and IR3.9 channels (day) • IR3.9 - IR10.8 BTD (day & night (warm clouds)) • IR8.7 – IR10.8

  4. Reflection of Solar Radiation • Reflection at NIR1.6 and IR3.9 is sensitive to cloud phase and very sensitive to particle size • Higher reflection from water droplets than from ice particles • During daytime, clouds with small water droplets (St, Sc) are much brighter than ice clouds(non-inverted image)

  5. Channel 03 (NIR1.6): Cloud Particle Size Water clouds(50-70%) MSG-1 5 June 2003 14:45 UTC Channel 03 (1.6 m) Small ice particles(40-50%) Large ice particles (30%)

  6. Channel 04 (IR3.9): Cloud Particle Size IR3.9 shows much more cloud top structures than IR10.8 (very sensitive to particle size) 3 1 3 1 1 1 1 1 3 3 1 1 3 3 2 2 1= ice clouds with very small particles 2= ice clouds with small particles 3= ice clouds with large ice particles Channel 04 (IR3.9) Channel 09 (IR10.8) MSG-1, 20 May 2003, 13:30 UTC

  7. Estimation of IR3.9r REFL = 100 * (R_tot - R_therm) / (TOARAD - R_therm) with: REFL Reflectance [in %] for channel IR3.9 R_tot measured total Radiance [in mW m-2 ster-1 (cm-1)-1] for channel IR3.9 R_therm CO2-corrected, thermal component of Radiance [in mW m-2 ster-1 (cm-1)-1] for channel IR3.9 TOARAD CO2-corrected, solar constant at Top of the Atmosphere [in mW m-2 ster-1 (cm-1)-1] for channel IR3.9 R_therm = R(IR3.9, BT(IR10.8)) * R3.9_corr

  8. Channel 04r (IR3.9r): Cloud Particle Size Water Clouds (20/25%) Maputo Water Clouds (16/20%) Large Ice Particles (1/2%) Small Ice Particles (8/11%) MSG-1, 6 November 2004, 12:00 UTC, Channel 04r (IR3.9r) Range: 0 % (black) to +60 % (white), Gamma = 2.5

  9. Difference IR3.9 - IR10.8: Cloud Particle Size Maputo Large Ice Particles (+26/+35 K) Small Ice Particles (+65/+73 K) MSG-1, 6 November 2004, 12:00 UTC, Difference IR3.9 - IR10.8 Range: -5 K (black) to +70 K (white), Gamma = 0.5

  10. RGB VIS0.8, IR3.9r, IR10.8: Colour Inputs Red Green Blue RGB

  11. Particle Size seen in Microphysical RGB Thin Ice Cloud (small ice) Maputo Thin Ice Cloud (large ice) Thick Ice Cloud (large ice) Thick Ice Cloud (small ice) MSG-1, 6 November 2004, 12:00 UTC, RGB VIS0.8, IR3.9r, IR10.8

  12. Colour Interpretation Thin Cirrus cloud (large ice particles) Thin Cirrus cloud (small ice particles) Ocean Veg. Land Fires / Desert Snow Deep precipitating cloud (precip. not necessarily reaching the ground) - bright, thick - large ice particles - cold cloud Deep precipitating cloud (Cb cloud with strong updrafts and severe weather)* - bright, thick - small ice particles - cold cloud *or thick, high-level lee cloudiness with small ice particles

  13. Comparison RGB 02,04r,09 vs Channel IR10.8 1. Large thin ice (dissipating storm) 2. Large thick ice 3. Small thick ice (developing storm) 1 2 3 RGB 02, 04r ,09 Channel 09 (IR10.8) MSG-1 7 September 2003, 11:45 UTC

  14. Animation (1/3) MSG-1 7 September 2003 11:45 UTC RGB Composite Red = VIS0.8 Green = IR3.9r Blue = IR10.8

  15. Animation (2/3) MSG-1 7 September 2003 12:00 UTC RGB Composite Red = VIS0.8 Green = IR3.9r Blue = IR10.8

  16. Animation (3/3) MSG-1 7 September 2003 12:15 UTC RGB Composite Red = VIS0.8 Green = IR3.9r Blue = IR10.8

  17. Estimation of Cloud Drop Effective Radius (Re) • Re is calculated from IR3.9r, using look-up table with viewing geometry as inputs • only for thick clouds that pass the following criteria: • Refl. VIS0.6 > 0.5 • BT(IR10.8) < 290 K • -0.5 K < BTD IR10.8 - IR12.0 < 1.5 K • -1.0 K < IR10.8 - IR8.7 < 5.0 K Reflectance at 3.9 m decreases with increasing Re, and saturates at about Re> 40 m (depending on instrument noise) !

  18. The T versus Re Scatterplot (Rosenfeld, Lensky, 1998) • Define a window containing a convective cloud cluster with elements representing all growing stages typically containing several thousand pixels MSG-1, 20 May 2003, 13:30 UTC

  19. The T versus Re Scatterplot (Rosenfeld, Lensky, 1998) • Define a window containing a convective cloud cluster with elements representing all growing stages typically containing several thousand pixels • Calculate T (top temperature from IR12.0 channel) and Re (from IR3.9 channel) MSG-1, 20 May 2003, 13:30 UTC

  20. The T versus Re Scatterplot (Rosenfeld, Lensky, 1998) • Define a window containing a convective cloud cluster with elements representing all growing stages typically containing several thousand pixels • Calculate T (top temperature from IR12.0 channel) and Re (from IR3.9 channel) • Calculate the median and other percentiles of the Refor each 1°C interval of cloud top temperature

  21. The T versus Re Scatterplot (Rosenfeld, Lensky, 1998) • Define a window containing a convective cloud cluster with elements representing all growing stages typically containing several thousand pixels • Calculate T (top temperature from IR12.0 channel) and Re (from IR3.9 channel) • Calculate the median and other percentiles of the Refor each 1°C interval of cloud-top temperature • Display graphically the Tversus Recurves of the 5th, 10th, 25th, 50th, 75th, 90th and 95th percentiles

  22. The T versus Re Scatterplot (Rosenfeld, Lensky, 1998) • Define a window containing a convective cloud cluster with elements representing all growing stages typically containing several thousand pixels • Calculate T (top temperature from IR12.0 channel) and Re (from IR3.9 channel) • Calculate the median and other percentiles of the Refor each 1°C interval of cloud-top temperature • Display graphically the Tversus Recurves of the 5th, 10th, 25th, 50th, 75th, 90th and 95th percentiles • Analyse the shape of the median (50th percentile, in green colour) to find the microphysical zones (see next slide)

  23. The Microphysical Zones Glaciated Zone Mixed Phase Zone Droplet Coalescence Growth Zone (Diffusional Droplet Growth Zone)

  24. The Microphysical Zones Glaciated Zone Mixed Phase Zone Rainout Zone Droplet Coalescence Growth Zone NOAA, AVHRR composite image 14 December 1997, 06:23 UTC Source: Rosenfeld & Lensky (1998)

  25. Some Important Properties of the T - Re Relation 1. The Time Space Exchangeability (Ergodicity) Lensky & Rosenfeld (2005): “The T-Rerelations of a convective cloud field is stable over time, and depends mainly on the thermodynamic and aerosol properties of the air mass”!

  26. Some Important Properties of the T - Re Relation 2. The Increase of Re with Height Lensky & Rosenfeld (2005): “The effective radius of convective clouds increases with height:” - Slower with in more polluted air mass - Slower with faster updraft velocities

  27. Some Important Properties of the T - Re Relation 3. Re for Severe Convective Storms Lensky & Rosenfeld (2005): “Severe convective storms are characterized by small effective radius reaching very cold temperatures!”

  28. Typical T-Re Scatterplots for different Updraft Velocities weak to normal strong very strong

  29. 1 6 2 5 4 3 MSG 2003 05 20 12:42 2_4r(g=2)_9

  30. 2 4 3 1 5 MSG 2003 06 05 14:57 2_4r(g=2)_9

  31. MSG 2003 05 20 13:42 2_4r(g=2)_9

  32. Hailstorm Potchefstroom: 27 Oct 2004

  33. Summary (for thick, cold ice clouds, day) Small Large NIR1.6 high Refl. (40-50%) low Refl. (30%) IR3.9r high Refl. (5-10%) low Refl. (1-2%) IR3.9 - IR10.8 large pos. (40-75 K) pos. (20-30 K) Microphys. RGB Convection RGB

  34. Summary (for thick, cold ice clouds, night) Small Large NIR1.6 N/A N/A IR3.9r N/A N/A IR3.9 - IR10.8 strongly influenced by IR3.9 noise Microphys. RGB N/A N/A Convection RGB N/A N/A

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