Motivation Experimental Description Results Summary Aerosol Removal and Cloud Collapse Accelerated by Supersaturation Fluctuations with a Positive Feedback in Turbulent Cloud: a Cloud-Chamber Study Kamal Kant Chandrakar Dr. Will Cantrell, Dr. Raymond A. Shaw Michigan Technological University Acknowledgment : NSF, NASA Earth and Space Science Fellowship [1 / 18] Kamal Kant Chandrakar Turbulence Induced Aerosol Feedback and Π -Chamber Group
Motivation Experimental Description Results Summary Aerosol Feedback Source: NASA Visible Earth-MODIS image [2 / 18] Kamal Kant Chandrakar Turbulence Induced Aerosol Feedback
Motivation Experimental Description Results Summary Aerosol Feedback Goren and Rosenfeld JGR 2015 [3 / 18] Kamal Kant Chandrakar Turbulence Induced Aerosol Feedback
Motivation Experimental Description Kamal Kant Chandrakar [4 / 18] Chang et al. BAMS 2016 Turbulence Induced Aerosol Feedback Steady-State Turbulent Cloud Summary Results The Π - Chamber Volume 97 Number 12 December 2016 TARGETED OBSERVATIONS TROPICAL SST BIASES DECADAL PREDICTION CLOUD LAB CLOUD LAB Understanding Cloud–Turbulence Interactions Understanding Cloud–Turbulence Interactions
Motivation Experimental Description Results Summary Steady-State Turbulent Cloud [5 / 18] Kamal Kant Chandrakar Turbulence Induced Aerosol Feedback The Π - Chamber Wet Boundaries
Motivation Experimental Description Kamal Kant Chandrakar [6 / 18] Chandrakar et al. PNAS 2016 Turbulence Induced Aerosol Feedback Results Summary Steady-State Turbulent Cloud Turbulent Mixing Cloud Formation in the Π -Chamber cool, humid a) b) steady aerosol injection Bottom 30 cloud droplet 25 activation p v [mbar] p v,mix turbulent 20 Equilibrium Vapor Pressure, p s (T) droplet growth p s (T mix ) convection in turbulent environment 15 T mix 10 Top droplet low high 5 10 15 20 25 sedimentation aerosol aerosol T [ o C] injection injection warm, humid
Motivation with a saturated side wall at mean temperature Kamal Kant Chandrakar [7 / 18] Experimental Description Turbulence Induced Aerosol Feedback Water vapor fmux to the side wall is signifjcant: nearly 1/3 reduction in s Results Summary Supersaturation in the chamber: Idealized vs Reality Steady-State Turbulent Cloud 1 Bottom 30 0.8 25 p v [mbar] 0.6 p v,mix Equilibrium Vapor Pressure, p s (T) 20 Z * p s (T mix ) 0.4 15 T mix 0.2 10 Top 0 5 10 15 20 25 0 0.2 0.4 0.6 0.8 1 T [ o C] T *
Motivation area under the PDFs is a result of Kamal Kant Chandrakar [8 / 18] Chandrakar et al. GRL 2017 Experimental Description semilog plot. linear size binning displayed in a Turbulence Induced Aerosol Feedback Note: The apparent difgerence in Residual: Results Summary Steady-State Turbulent Cloud Supersaturation in the Chamber: Idealized vs Reality 0.018 Interstitial 0.016 Residual 0.014 0.012 D mode ≈ 110 nm → 0.01 s c = 0 . 1 % PDF 0.008 0.006 0.004 0.002 0 10 1 10 2 D p [nm]
Motivation Experimental Description Kamal Kant Chandrakar [9 / 18] Chandrakar et al. PNAS 2016 Turbulence Induced Aerosol Feedback Droplet Size Distribution at Steady-State Results Turbulence Induced Broadening Summary Turbulence Induced Cloud Cleansing 600 0.15 n a = 1515 /cm 3 /min ˙ n a = 12 /cm 3 /min ˙ ˙ n a = 4 /cm 3 /min 500 ˙ n a = 2 /cm 3 /min n a = 1 /cm 3 /min ˙ 400 0.1 PDF 300 200 0.05 100 0 0 0 2 4 6 8 10 12 0 10 20 30 40 d [ µ m]
Motivation mixing to s o Kamal Kant Chandrakar [10 / 18] Chandrakar et al. PNAS 2016, JAS 2018 dt Condensation Growth: fmuctuation Experimental Description droplet growth s Turbulence Induced Aerosol Feedback Stochastic Condensation Growth Summary Turbulence Induced Cloud Cleansing Results Turbulence Induced Broadening ) 1/2 ( 2 σ 2 s o − s ds ( t ) = dt + s 0 dt η ( t ) − τ t τ c τ t � �� � ���� � �� � d σ 2 dr 2 r 2 = 4 ξ s ′ r 2 ′ dt = 2 ξ s ,
Motivation (fjxed) Kamal Kant Chandrakar [11 / 18] Chandrakar et al. PNAS 2016 Experimental Description (controlled by aerosol injection) r Turbulence Induced Aerosol Feedback Turbulence Induced Cloud Cleansing Turbulence Induced Broadening Summary Results Turbulent Induced Broadening s = σ 2 s 0 τ s s = s o τ s σ 2 ¯ ; 70 τ t τ t 80 60 σ r 2 ∝ s ′ r 2 ′ → σ s 0 τ s 2 [ µ m 2 ] 60 t 1/2 40 50 τ t σ r 20 0 0 50 100 40 2 [ µ m 2 ] τ s = 1 1 τ t + 1 τ c [s] τ s : τ c σ r 30 τ t : Turbulence correlation time 20 10 1 τ c : Phase relaxation time, ∝ ¯ n ¯ 0 0.6 0.8 1 1.2 1.4 1.6 1.8 2 τ s [s]
Motivation Experimental Description Kamal Kant Chandrakar [12 / 18] Turbulence Induced Aerosol Feedback Turbulence Induced Cloud Cleansing Results Summary Turbulence Induced Broadening High Low Aerosol Aerosol C Activation Activation l Rate Rate o u Slow Faster d Aerosol Aerosol Continental Decay Decay Polluted and Cloud and C Cloud Droplet Cloud o Growth Growth l l Suppressed Faster a Droplet Droplet Loss p Loss s e Stage-I : Suppressed Stage-II : Faster Supersaturation Mean and Supersaturation Mean and Fluctuation Fluctuation Recovery
Motivation Experimental Description Kamal Kant Chandrakar [13 / 18] Chandrakar et al. GRL 2017 Turbulence Induced Aerosol Feedback Summary Results Turbulence Induced Broadening Turbulence Induced Cloud Cleansing 10 4 20 n d [cm -3 ] d [ m] 10 10 2 0 4 r [ m] 2 0 10 5 n a [cm -3 ] 10 0 15 c [s] 10 5 0 0 50 100 150 t [min]
Motivation Experimental Description Kamal Kant Chandrakar [14 / 18] Chandrakar et al. GRL 2017 Turbulence Induced Aerosol Feedback Turbulence Induced Cloud Cleansing Results Summary Turbulence Induced Broadening 28 8 26 6 24 4 22 ln(dN bin ) a [min] 2 20 0 18 -2 16 -4 14 12 -6 0 50 100 150 200 250 0 50 100 150 D a [nm] t [min]
Motivation Experimental Description Kamal Kant Chandrakar [15 / 18] Chandrakar et al. GRL 2017 Turbulence Induced Aerosol Feedback Results Summary Turbulence Induced Broadening Turbulence Induced Cloud Cleansing 10 -3 1.25 20 18 1.2 16 15 1.15 10 2 14 1.1 n d [cm -3 ] S-S(t=0) s [%] 10 d [ m] 1.05 12 1 5 10 0.95 8 0.9 0 0.85 6 0 50 100 150 200 250 300 0 50 100 150 200 250 300 t [min] t [min]
Motivation Experimental Description Kamal Kant Chandrakar [16 / 18] Turbulence Induced Aerosol Feedback Turbulence Induced Cloud Cleansing Results Summary Turbulence Induced Broadening High Low Aerosol Aerosol C Activation Activation l Rate Rate o u Slow Faster d Aerosol Aerosol Continental Decay Decay Polluted and Cloud and C Cloud Droplet Cloud o Growth Growth l l Suppressed Faster a Droplet Droplet Loss p Loss s e Stage-I : Suppressed Stage-II : Faster Supersaturation Mean and Supersaturation Mean and Fluctuation Fluctuation Recovery
Motivation Experimental Description Kamal Kant Chandrakar [17 / 18] uration fmuctuations: a positive feedback. Cloud cleansing enhanced through supersat- Stochastic theory and experiments suggest: moist Rayleigh-Bénard convection. Cloud form via isobaric mixing in a turbulent Turbulence Induced Aerosol Feedback Summary Summary Summary Results cool, humid a) steady b) aerosol injection cloud droplet activation turbulent droplet growth convection in turbulent environment droplet low high sedimentation aerosol aerosol injection injection warm, humid 0.15 70 ˙ n a = 1515 /cm 3 /min n a = 12 /cm 3 /min ˙ ˙ n a = 4 /cm 3 /min 60 80 ˙ n a = 2 /cm 3 /min 2 [ µ m 2 ] 60 n a = 1 /cm 3 /min ˙ 40 50 σ r 20 0.1 0 σ 2 0 50 100 2 [ µ m 2 ] 40 and σ r 2 ∝ s ′ r 2 ′ → σ s 0 τ s σ 2 so τ s τ t t 1/2 . PDF τ c [s] s = σ r 30 τ t 0.05 20 10 0 0 0 10 20 30 40 0.6 0.8 1 1.2 1.4 1.6 1.8 2 τ s [s] d [ µ m] 30 10 4 25 n d [cm -3 ] 20 d [ m] a [min] 20 10 10 2 0 4 15 r [ m] 2 10 0 50 100 150 200 250 D p [nm] 0 10 5 8 6 n a [cm -3 ] 4 ln(dN bin ) 2 10 0 0 15 c [s] 10 -2 -4 5 0 -6 0 50 100 150 0 50 100 150 t [min] t [min]
Motivation Experimental Description Results Summary Summary Thank You [18 / 18] Kamal Kant Chandrakar Turbulence Induced Aerosol Feedback
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