Vertical microphysical profiles and closure calculations

Transcription

1 Presented at the ACRIDICON workshop March 2016, Ilha Bela, Brazil Vertical microphysical profiles and closure calculations Daniel Rosenfeld and Ramon Braga The Hebrew University of Jerusalem, Israel

2 Closure between aerosols and cloud base drop size distribution (DSD): This can be done by combining measured CCN supersaturation (S) activation spectrum below cloud base, with the measured cloud drop number concentrations (Nd) and updrafts measured (Wb) at the non-precipitating base of the same cloud cluster. To be presented by Ramon Braga Cloud DSD and updrafts at cloud base CCN(S) below cloud base Closure of CCN(S) vs. DSD(W)

3 2. Vertical evolution of cloud and hydrometeor DSD, thermodynamics and updrafts. Flying through the developing cloud tops prevents contamination by precipitation falling from above.

4 First time measurements of cloud aerosol interactions in mixed phase and ice convective clouds in the Amazon.

5 Rosenfeld et al., Science Growing Mature Dissipating Hail

6 Hyderabad Bay of Bengal Bareilly No Rain Bay of Bengal This shallow deep polluted cloud cloud does starts not raining only because after its top is reaching not reaching height the of 6.5 height km. where cloud drops are large enough to form rain. This shallow clean pristine marine Rain cloud starts raining already at a height of < 1 km. 2 km. 6 6 The relation between r e and depth cloud depth above its base (D) is uniquely related to CCN. Rosenfeld and Woodley, CAIPEEX-2 Final report to IITM.

7 How sensitive is the threshold value? Rain initiates at m, but accelerates strongly above 14 m. re c 14 m R is rain water content in drops with diameters of mm, as measured by the Cloud Imaging Probe (CIP). R> g/m 3 R> g/m 3 raises the precipitation flag. 7 Freud and Rosenfeld, JGR

8 Height, m Temp, C 7,073 m, C 6,793 m, C 6,124 m, -8.7 C 5,816 m, -6.8 C 4,406 m, +1.3 C 8 8 Aircraft measured images of vertical development of cloud and rain drops in the cloud

9 Why do we need the vertical profiles of cloud drop size distributions? Aerosol composition + size distribution CCN(S) CCN(S) + Updrafts Cloud base drop concentrations (Nd b ) Nd b adiabatic drop concentrations (Nd a ) Re a Re, due to nearly inhomogeneous cloud mixing. LWC a a Re a3 Nd a LWC a a Cloud depth above its base (D) D for a given Re a a Nd a D for a given Re a Nd b Coalescence rate a Re 5 Rain initiates at Re m D for Re= 14 m a Nd b The critical D for rain initiation (Dc) is D where Re reaches 14 m Dc a Nd b

10 Why do we need the vertical profiles of cloud drop size distributions? Aerosol composition + size distribution CCN(S) CCN(S) + Updrafts Cloud base drop concentrations (Nd b ) Nd b adiabatic drop concentrations (Nd a ) Re a Re, due to nearly inhomogeneous cloud mixing. LWC a a Re a3 Nd a LWC a a Cloud depth above its base (D) D for a given Re a a Nd a D for a given Re a Nd b Coalescence rate a Re 5 Rain initiates at Re m D for Re= 14 m a Nd b The critical D for rain initiation (Dc) is D where Re reaches 14 m Dc a Nd b

11 CAIPEEX flights, India Konwar et al., JGR 2012 ACRIDICON, Amazon 9/2014

12 NIXE-CAS NIXE-CAS CAS-POL CCP-CDP

13 NIXE CDP Cloud drop diameter [ m]

14 NIXE CAS-DPOL CDP Cloud drop diameter [ m]

15 CDP

16 CAS-DPOL

17 NIXE-CAS

18 CDP

19 CAS-DPOL

20 NIXE-CAS

21 Which cloud probe to believe? CDP appears to have double Nd and LWC with respect to both CAS probes. CAS DSD is distorted badly at sizes < 10 m, and has a poor size resolution above 10 m. While CAS LWC looks unrealistically low, CDP Nd looks unrealistically high. Conclusion: additional calibration and QC required

22 HUCM

23 Water cloud only Mixed phase Ice

24 HUCM

25 HUCM

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27 Water cloud Mixed phase Ice

28 Water cloud Mixed phase Ice

29 From Wendish et al., BAMS 2016

30 First rain

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43 CDP

44 CAS-NIXE

45 From Wendish et al., BAMS 2016

46 First rain

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59 CDP

60 CAS-NIXE

61 From Wendish et al., BAMS 2016

62 First rain

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76 CDP

77 CAS-NIXE

78 Technical Summary Further scientific advancements require to: Calibrate and reconcile the cloud drop probes Obtain images of the CIP (PHIPS is not a replacement), as was done in India, Israel, California and most other cloud physics campaigns. Classify the hydrometeors to rain and ice. Unmask and QC the BAHAMAS updrafts within the clouds.

79 , 10:14 UT, 6720 m, -8.1ºC. Max HWLWC=1.66 gm-3. N of Bareilly. The cloud has supercooled rain drops. 79

80 , 10:03 UT, 7350 m, -11.8ºC. Max HWLWC=0.87 gm-3. N of Bareilly. The cloud has small raindrops and larger freezing rain drops. 80

81 , 10:00 UT, 7700 m, -14.7ºC. Max HWLWC=1.45 gm-3. N of Bareilly. The cloud has small rain drops, large freezing rain drops and small graupel. 81

82 , 9:57 UT, 8130 m, -17.1ºC. Max HWLWC=0.49 gm-3. N of Bareilly. The cloud is glaciating, with frozen rain drops, small graupel and ice crystals. 82

83 Scientific Summary Height for rain initiation (Dc) increases linearly with cloud base drop concentrations (Nd) Increasing Dc from 50 to ~500 cm -3 incurs warm cloud invigoration due to reducing the large S at low Nd and advanced coalescence. Further increase of Nd incurs mixed phase cloud invigoration due to less rainout and thus more latent heat release of freezing. Rain initiates at Re > 12 to 13 m and is fully developed for Re > 14 m, as in other studies. Supercooled cloud water extend to colder temperatures with more Nd and smaller Re.

84 Thank you for flying with us!

85 Thank you for flying with us!

86 Scientific Summary Height for rain initiation (Dc) increases linearly with cloud base drop concentrations (Nd) Increasing Dc from 50 to ~500 cm -3 incurs warm cloud invigoration due to reducing the large S at low Nd and advanced coalescence. Further increase of Nd incurs mixed phase cloud invigoration due to less rainout and thus more latent heat release of freezing. Rain initiates at Re > 12 to 13 m and is fully developed for Re > 14 m, as in other studies. Supercooled cloud water extend to colder temperatures with more Nd and smaller Re.