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UNDERSTANDING CONVECTIVE CLOUDS THROUGH THE EYES OF METEOSAT SECOND GENERATION (MSG)

Jochen Kerkmann Satellite Meteorologist, Training Officer jochen.kerkmann@eumetsat.int www.eumetsat.int Contributors: D. Rosenfeld (HUJ), I. Lensky (HUJ) J. Prieto (EUM), K. Kollath (HMS). UNDERSTANDING CONVECTIVE CLOUDS THROUGH THE EYES OF METEOSAT SECOND GENERATION (MSG).

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UNDERSTANDING CONVECTIVE CLOUDS THROUGH THE EYES OF METEOSAT SECOND GENERATION (MSG)

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  1. Jochen Kerkmann Satellite Meteorologist, Training Officer jochen.kerkmann@eumetsat.int www.eumetsat.int Contributors: D. Rosenfeld (HUJ), I. Lensky (HUJ) J. Prieto (EUM), K. Kollath (HMS) UNDERSTANDING CONVECTIVE CLOUDS 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. 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 darker than ice clouds(inverted image) Figure by COMET

  6. 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%)

  7. 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

  8. 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

  9. 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

  10. 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

  11. For cold clouds, the IR3.9 - IR10.8 BTD is very sensitive to albedo(i.e. cloud particle size) IR3.9 - IR10.8 BTD for Opaque Clouds IR3.9 cloud at cloud at cloud at Refl. 200 K 250 K 300 K 5 90 43 12 4 85 38 10 3 78 33 8 2 70 26 5 1 57 16 3 0 0 0 0 IR3.9 - IR10.8 brightness temperature difference (in K) for different temperatures of the cloud assuming little humidity above the cloud.

  12. Formation of Small / Large Ice Particles ? • The problem of how to explain the formation and growth of ice particles in clouds, particularly in cumulus clouds, remains one of the major problems in cloud physics • Ice particles affect all important characteristics of clouds such as precipitation formation, thunderstorm electrification, interaction with radiation and latent heat release Alan Blyth and Alan Gadian School of Earth & Environment, Leeds

  13. Where do small ice particles form ? • in Cb clouds with strong updrafts • in mountain wave clouds • in highly “polluted” clouds

  14. Small / Large Ice Particles in Cb Clouds picture form Charles Pfeil picture form Brian A. Morganti strong updraft weak updraft  small ice particles  large ice particles

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