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

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

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)

RGB VIS0.8, IR3.9r, IR10.8: Colour Inputs RedGreen BlueRGBRGB

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

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 Thin Cirrus cloud (large ice particles) Thin Cirrus cloud (small ice particles) Ocean Veg. Land Fires / Desert Snow Colour Interpretation

Maputo MSG-1, 6 November 2004, 12:00 UTC, RGB 05-06, 04-09, Thin Ice Cloud (small ice) Thick Ice Cloud (small ice) Thick Ice Cloud (large ice) Thin Ice Cloud (large ice) Particle Size seen in Convection RGB

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

Comparison RGB 02,04r,09 vs RGB 05-06,04-09,03-01 MSG-1, 6 November 2004, 12:00 UTC RGB 02, 04r,09 RGB 05-06, 04-09, better identification of young, severe storms

MSG-1, 3 February 2004, 11:30 UTC RGB 02, 04r,09 RGB 05-06, 04-09, better identification of young, severe storms Comparison RGB 02,04r,09 vs RGB 05-06,04-09,03-01

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

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

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

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

Severe Convection Central African Republic Chad Dem. Republic of the Congo Sudan Cameroon MSG-1 20 May :00 UTC RGB Composite R = NIR1.6 G = VIS0.8 B = VIS0.6 Squall Line / Convection Northern Cameroon Squall Line

12:30 UTC 13:00 UTC 13:30 UTC 14:00 UTC Convection Northern Cameroon Met-7, 20 May 2003, IR Channel

12:30 UTC 12:45 UTC 13:00 UTC 13:15 UTC 13:30 UTC 13:45 UTC New Convective Developments Top Temp. -78°C Small Ice Particles Top Temp. -83°C Large Ice Particles Convection Northern Cameroon MSG-1, 20 May 2003, RGB Composite 01, 04, 10i

MSG :00 02_04r_09

MSG : _09-04_09

MSG : _09-07_09

MSG : _09-04_09

Estimation of Cloud Drop Effective Radius (Re) Reflectance at 3.9  m decreases with increasing Re, and saturates at about Re > 40  m (depending on instrument noise) ! 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 IR IR12.0 < 1.5 K  -1.0 K < IR IR8.7 < 5.0 K

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

The T versus Re Scatterplot (Rosenfeld, Lensky, 1998) 1)Define a window containing a convective cloud cluster with elements representing all growing stages typically containing several thousand pixels 2)Calculate T (top temperature from IR12.0 channel) and Re (from IR3.9 channel) MSG-1, 20 May 2003, 13:30 UTC

The T versus Re Scatterplot (Rosenfeld, Lensky, 1998) 1)Define a window containing a convective cloud cluster with elements representing all growing stages typically containing several thousand pixels 2)Calculate T (top temperature from IR12.0 channel) and Re (from IR3.9 channel) 3)Calculate the median and other percentiles of the Re for each 1°C interval of cloud top temperature

The T versus Re Scatterplot (Rosenfeld, Lensky, 1998) 1)Define a window containing a convective cloud cluster with elements representing all growing stages typically containing several thousand pixels 2)Calculate T (top temperature from IR12.0 channel) and Re (from IR3.9 channel) 3)Calculate the median and other percentiles of the Re for each 1°C interval of cloud-top temperature 4)Display graphically the T versus Re curves of the 5th, 10th, 25th, 50th, 75th, 90th and 95th percentiles

The T versus Re Scatterplot (Rosenfeld, Lensky, 1998) 1)Define a window containing a convective cloud cluster with elements representing all growing stages typically containing several thousand pixels 2)Calculate T (top temperature from IR12.0 channel) and Re (from IR3.9 channel) 3)Calculate the median and other percentiles of the Re for each 1°C interval of cloud-top temperature 4)Display graphically the T versus Re curves of the 5th, 10th, 25th, 50th, 75th, 90th and 95th percentiles 5)Analyse the shape of the median (50th percentile, in green colour) to find the microphysical zones (see next slide)

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

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

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

Typical T-Re Scatterplots for different Updraft Velocities weak to normal strongvery strong

MSG :42 2_4r(g=2)_9

MSG :57 2_4r(g=2)_

MSG :42 2_4r(g=2)_9

Hailstorm Potchefstroom: 27 Oct 2004

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

SmallLarge NIR1.6N/AN/A IR3.9rN/AN/A IR3.9 - IR10.8strongly influenced by IR3.9 noise Microphys. RGBN/AN/A Convection RGBN/AN/A Summary (for thick, cold ice clouds, night)