UNDERSTANDING CONVECTIVE CLOUDS THROUGH THE EYES

OF (MSG)

Cloud Particle Size

Jochen KerkmannSatellite Meteorologist, Training Officerjochen.kerkmann@eumetsat.intwww.eumetsat.intContributors: D. Rosenfeld (HUJ), I. Lensky (HUJ)

J. Prieto (EUM), D. Lindsey (CIRA) K. Kollath & M. Putsay (HMS) P. Watts & M. Koenig (EUM)

Observing Cloud Particle Size

MFG: not possible ( only cloud thickness and cloud top temperature)

MSG: possible ( 2 window channels)

• NIR1.6 and IR3.9r channels (day)• IR3.9 - IR10.8 BTD (day & night (warm clouds))

• IR8.7 – IR10.8

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)

Difference IR3.9 - IR10.8: Cloud Particle Size

Maputo

MSG-1, 6 November 2004, 12:00 UTC, Difference IR3.9 - IR10.8Range: -5 K (black) to +70 K (white), Gamma = 0.5

Large Ice Particles(+26/+35 K)

Small Ice Particles(+65/+73 K)

Observed IR3.9 - IR10.8 BTD for Opaque Ice Clouds

78 68 56 72 62 50 65 55 43 58 47 35 47 37 25 0 0 0

IR3.9 - IR10.8 brightness temperature difference depends on both:cloud particle size and cloud top temperature

(and sun/satellite viewing angles)

IR3.9Refl.

10 8 6 4 2 0

Cloud Top Temperature -70°C -60°C -50°C

Where do small ice particles form ?

in Cb clouds with strong updrafts in Cb clouds with cold (high) cloud base (short

time from cloud base to spontaneous freezing level)

in mountain wave and Pileus clouds in highly “polluted” clouds generally: in ice clouds that form rapidly

“Updraft” Effect

This idea follows from results from multiple papers by D. Rosenfeld, and Heymsfield et al. (2005)

Updraft Effect

„Cloud Depth“ Effect

This idea follows from results from multiple papers by D. Rosenfeld, and Heymsfield et al. (2005)

Maputo

MSG-1, 6 November 2004, 12:00 UTC

Thick Ice Cloud(small ice)

Thick Ice Cloud(large ice)

Particle Size seen in Day Convective Storms RGB

Recommended Range and Enhancement:Recommended Range and Enhancement:

Beam Channel Range Gamma

Red WV6.2 - WV7.3 -35 … +5 K 1.0Green IR3.9 - IR10.8 -5 … +60 K 0.5Blue NIR1.6 - VIS0.6 -75 … +25 % 1.0

RGB 05-06, 04-09, 03-01 ("Day Convective Storms")

devised by: J. Kerkmann

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 strongupdrafts and severeweather)*

- high-level cloud- small ice particles

*or thick, high-level lee cloudiness with small ice particles

Colour Interpretation

MSG-1, 29 June 2006, 12:00 UTC

1

2

1. Large ice (dissipating storm)2. Small ice (strong updrafts, large hail)

RGB Convection RGB Nat. Colours

Comparison RGB Convection vs RGB Nat. Colours

12:00 UTC(animation 1/7)

12:15 UTC(animation 2/7)

• Small ice (high IR3.9r of 6-7%)

• Long-living storm system• Convective outflow boundary• Overshooting tops• Gravity waves• Radial Ci

12:30 UTC(animation 3/7)

12:45 UTC(animation 4/7)

13:00 UTC(animation 5/7)

13:15 UTC(animation 6/7)

13:30 UTC(animation 7/7)

IR10.8 IR3.9refl

HRV +radar Convective Storms RGB: G=IR3.9-IR10.8

IR3.9-IR10.8 depends on both

IR10.8 IR3.9refl

HRV +radar Convective Storms RGB: G=IR3.9-IR10.8

IR3.9-IR10.8 depends on both

MSG-1, 13 June 2003, 12:00 UTC

RGB 02, 04r ,09 RGB 05-06, 04-09, 03-01 better identification of young, severe storms

Comparison RGB 02,04r,09 vs RGB 05-06,04-09,03-01

MSG-2, 3 April 2008, 12:30 UTC

Cb Cloud(small ice,

IR3.9r=16%)

Small Ice Particles in Clouds with Cold Base

MSG-1, 22 February 2007, 12:00 UTC

Thick Ice Cloud(small ice)

dust outbreak

Small Ice Particles in “Polluted” Clouds

Small Ice Particles in High-level Lee Cloudiness

MSG-1, 19 March 2007, 08:00 UTCRGB WV6.2-WV7.3, IR3.9-IR10.8, NIR1.6-VIS0.6

(RGB Convection)

Very cold clouds(lee cloudiness) with

small ice particles

Small Ice Particles in isolated High-level Wave Cloud

MSG-2, 11 April 2008, 11:00 UTC Metop-A, AVHRR, 8:49 UTC

Mountain wave cloud withsmall ice particles

Balatonalmádi

Pileus cloud15:27 UTC

André Simon, Mária Putsay, Ákos Horváth:

Is the appearance of this Is the appearance of this yellow spot connected to the yellow spot connected to the

Pileus?Pileus?

Small Ice Particles in Pileus Clouds

SmallSmall LargeLarge

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)

Day Microphys. RGB

Convection RGB

Summary (for thick, cold ice clouds, day)