New capabilities with high resolution cloud micro-structure facilitated by MTG 2.3 um channel

Transcription

1 Slide 19 November 2016, V1.0 New capabilities with high resolution cloud micro-structure facilitated by MTG 2.3 um channel Author: Daniel Rosenfeld The Hebrew University of Jerusalem (HUJ)

2 Prof. Daniel Rosenfeld The Hebrew University of Jerusalem, Israel Areas of specialty: Cloud-aerosol interactions, precipitation and climate. Severe convective storms. Remote sensing of clouds.

3 ABSORPTION Imaginary Refraction Index How can we detect from space the phase and size of microscopic cloud particles? water ice Slide 3 Wave Length [mm] Channel 4, 3.9 mm, absorbs even more solar radiation than Channel 3, 1.6 mm. Ice absorbs more strongly than water at 3.9 mm

4 Scattering occurs on the drop surface, ~ radius 2 Infra-Red Absorption occurs inside The drop volume, ~ radius 3 Definition of Effective Radius (r eff ) of cloud droplets: Sum of volumes / sum of surface areas of the droplets in the measured cloud volume Net reflectance ~Scattering / Absorption ~ radius 2 / radius 3 = 1/radius Reflectance ~ Radius -1

5 Ship Track Formation N ~ 40 cm -3 W ~ 0.30 g m -3 r e ~ 11.2 µm N ~ 100 cm -3 W ~ 0.75 g m -3 r e ~ 10.5 µm

6 Ship Track Formation Red: Visible reflectance Green: 3.7 mm reflectance Blue: 11 mm temperature N ~ 40 cm -3 W ~ 0.30 g m -3 r e ~ 11.2 µm N ~ 100 cm -3 W ~ 0.75 g m -3 r e ~ 10.5 µm

7 Red: Visible reflectance Green: 3.7 mm reflectance Blue: 11 mm temperature Ship tracks over the North Pacific

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9 Q: Are cloud drops in A larger than in B? B A

10 Answers: A: The cloud drops are small, no rain. B: The cloud drops are large, probably raining. B A

11 How can we distinguish between water and ice cloud?

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13 Large ice crystal collects small supercooled cloud drops

14 Problem: Ice cloud looks like water cloud with large drops!

15 Cold cloud with small supercooled drops: Low T +Visibly Bright +Small Drops = AC St Fog Snow -32C Ci Cb 0.8 mm 3.9r mm 10.8 mm

16 Cold cloud with small supercooled drops: Low T +Visibly Bright +Small Drops = Cold cloud with large ice crystals: Low T +Visibly Bright +Large Ice = St Fog AC Snow -32C Ci 0.8 mm 3.9r mm 10.8 mm Cb

17 Animation 1/9 0.8 mm 3.9r mm 10.8 mm

18 0.8 mm 3.9r mm 10.8 mm Animation 2/9

19 0.8 mm 3.9r mm 10.8 mm Animation 3/9

20 0.8 mm 3.9r mm 10.8 mm Animation 4/9

21 0.8 mm 3.9r mm 10.8 mm Animation 5/9

22 0.8 mm 3.9r mm 10.8 mm Animation 6/9

23 0.8 mm 3.9r mm 10.8 mm Animation 7/9

24 0.8 mm 3.9r mm 10.8 mm Animation 8/9

25 0.8 mm 3.9r mm 10.8 mm Animation 9/9

26 But, Cloud drops over pristine ocean can be large, thus ambiguous with ice

27 But, Cloud drops over pristine ocean can be large, thus ambiguous with ice Can you point at the water clouds? Red: Visible reflectance Green: 3.7 mm reflectance Blue: 11 mm temperature

28 T T 1 3 r e r e 2 T r Red: Visible reflectance Green: 3.7 mm reflectance Blue: 11 mm temperature

29 ABSORPTION Imaginary Refraction Index How can we detect from space the phase and size of microscopic cloud particles? MSG water ice Slide 29 Wave Length [mm] Channel 4, 3.9 mm, absorbs even more solar radiation than Channel 3, 1.6 mm. Ice absorbs more strongly than water at 3.9 mm

30 ABSORPTION Imaginary Refraction Index How can we detect from space the phase and size of microscopic cloud particles? MTG water ice Slide 30 Wave Length [mm] Channel 4, 3.9 mm, absorbs even more solar radiation than Channel 3, 1.6 mm. Ice absorbs more strongly than water at 3.9 mm

31 The spectral dependence of the imaginary component of the refractive indices of ice and water between 2.0 and 2.3 μm, showing the crossing point around 2.15 μm.

32 ABSORPTION Imaginary Refraction Index How can we detect from space the phase and size of microscopic cloud particles? water ice Slide 32 Wave Length [mm] Channel 4, 3.9 mm, absorbs even more solar radiation than Channel 3, 1.6 mm. Ice absorbs more strongly than water at 3.9 mm

33 Imaginary Refraction Index ABSORPTION Water Ice Wave Length [mm]

34 Imaginary Refraction Index ABSORPTION Water Ice Wave Length [mm]

35 MTG

36 MTG

37 MTG

38 Himawari

39 Red: Visible reflectance Green: 3.7 mm reflectance Blue: 11 mm temperature

40 Can you point at the water clouds? Red: 1.6 mm reflectance Green: 2.3 mm reflectance Blue: Visible reflectance

41 Red: T mm Green: T mm Blue: mm

42 Small ice crystals Large ice crystals mm 2.3 mm 0.4 mm Large water drops Red: NIR1.6, 0-40 % Green: NIR2.3, 0-40% Blue: VIS0.4, 0-100% Small water drops

43 Red: 1.6 mm reflectance Green: 2.3 mm reflectance Blue: Visible reflectance

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46 -7 C -4 C

47 -7 C -4 C

48 Red: Visible reflectance Green: 3.7 mm reflectance Blue: 11 mm temperature

49 Are the coldest clouds water (yes) or ice (no)? Red: Visible reflectance Green: 2.3 mm reflectance Blue: 11 mm temperature

50 Are the coldest clouds water (yes) or ice (no)? Red: NIR1.6, Range 0 to 40 % Green: NIR2.3, Range 0 to 40% Blue: VIS0.4, Range 0 to 100%

51 Small ice crystals Large ice crystals mm 2.3 mm 0.4 mm Large water drops Red: NIR1.6, 0-40 % Green: NIR2.3, 0-40% Blue: VIS0.4, 0-100% Small water drops

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54 Red: T12.3-T11.2 Green: T11.2-T8.6 Blue: T11.2

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57 Are there clouds over the mountains?

58 Are there clouds over the mountains?

59 Are there clouds over the mountains?

60 Pointer at the frozen lakes

61 Pointer at the frozen lakes

62 Pointer at the frozen lakes

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64 Pointer at the Antarctic sea ice

65 Pointer at the Antarctic sea ice

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68 Solar radiation Satellite High spatial resolution is required to resolve the vertical structure of convective clouds. Lower resolution misses all but largest and deepest clouds. Coarse Fine R1 R2 T, r e, Phase Measurement concept for T-r e based CCN retrievals

69 2-km image

70 1-km image

71 2-km image

72 MODIS microphysical resolution: 1000 m NPP/VIIRS products resolution: 750 m NPP/VIIRS Imager resolution: 375 m

73 VIIRS :59 Red: Visible reflectance Green: 3.7 mm reflectance Blue: 11 mm temperature km

74 MODIS :00

75 1 VIIRS :15 UT km

76 Temperature ( C) 1 VIIRS :15 UT 3-60 VIIRS npp re50-1 re50-2 re50-3 re Effective Radius (mm) km

77 MODIS :20 UT

78 Temperature ( C) Temperature ( C) npp modis -60 VIIRS -60 MODIS re50-1 re50-2 re50-3 re Effective Radius (mm) r30-1 r30-2 r30-3 r Effective Radius (mm)

79 Summary Until now ice cloud was differentiated from supercooled water cloud mainly based on assumption that ice crystals are typically much larger that cloud drops. However, supercooled clouds can have very large drops Using a combination that cause ambiguity with ice. Because ice absorbs more strongly at 1.6 mm while water absorbs more strongly at 2.3 mm, the combination these channels allows an unambiguous separation between water and ice clouds. Slide 79