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

7. Cloud Particle Size Picture from Bob White

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

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) Reflection of Solar Radiation

Figure by COMET 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)

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

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

REFL = 100 * (R_tot - R_therm) / (TOARAD - R_therm) with: REFLReflectance [in %] for channel IR3.9 R_totmeasured total Radiance [in mW m -2 ster -1 (cm -1 ) -1 ] for channel IR3.9 R_thermCO2-corrected, thermal component of Radiance [in mW m -2 ster -1 (cm -1 ) -1 ] for channel IR3.9 TOARADCO2-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 Estimation of IR3.9r

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

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

IR3.9 - IR10.8 BTD for Opaque Clouds IR3.9cloud atcloud atcloud at Refl. 200 K 250 K 300 K IR3.9 - IR10.8 brightness temperature difference (in K) for different temperatures of the cloud assuming little humidity above the cloud. For cold clouds, the IR3.9 - IR10.8 BTD is very sensitive to albedo (i.e. cloud particle size)

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

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

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