entrainment and microphysics in rico cu

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ENTRAINMENT and MICROPHYSICS in RICO CuHermann Gerber

NASA/GISS WorkshopSept. 2006

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Scorer, R.S., and F.H. Ludlam: 1953: Bubble theory of penetrative convection. Q.J. Roy. Meteor. Soc., 79, 317-341.

Erosion (Detrainment)

Entrainment

Rising Toroidal Thermal

(Blyth, A.M., et al., 1988: J. Atmos. Sci., 45, 3944-3964.) (Baker, B., A., 1992: J. Atmos. Sci., 49, 387-404.)

CLASSICAL ENTRAINMENT CONCEPTCLASSICAL ENTRAINMENT CONCEPT

X

(Damiani, et al, 2006: J. Atmos. Sci., 63, 1432-1450)

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MICROPHYSICS ISSUESMICROPHYSICS ISSUES

2. What about entrained CCN?

1. Homogenous or inhomogeneous mixing?

3. Entrainment scales?

4. Super-Adiabatic Drops?

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(Lasher-Trapp, S., W. Cooper, and A. Blyth, 2005: QJRMS, 195-220)

SUPERADIABATIC

ADIABATIC PEAK

HOMOGENOUS MIXING INHOMOGENEOUS MIXING

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RICO FLIGHTS

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CONDITIONAL SAMPLING FOR ACTIVE TURRETS

VERTICAL VELOCITY IS POSITIVE (~80%) IN AREA WITHVERTICAL VELOCITY IS POSITIVE (~80%) IN AREA WITH LWCLWC

TOP OF CLOUD IS VISIBLE IN FORWARD-LOOKING VIDEO TOP OF CLOUD IS VISIBLE IN FORWARD-LOOKING VIDEO

A SINGLE TURRET IS TRAVERSEDA SINGLE TURRET IS TRAVERSED

CLOUD IS TRAVERSED NEAR CLOUD TOPCLOUD IS TRAVERSED NEAR CLOUD TOP

(Raga, G.B., et al, 1990: J. Atmos. Sci., 47, 338-355.)

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(m)

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PVM

FSSP

Fast FSSP

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LWC N r

rN r

N

r r

LWC N r

T v

v

i ii

T

e v

T e

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3

3 1 3

3

/

PVM

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10-cm RESOLUTION (1000 Hz) LWC DATA

PVM

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(Gerber, H., et al, 2001: J. Atmos. Sci., 58, 497-503)(Burnet,F., and J.-L. Brenguier, 2006: J. Atmos. Sci., in print)

(Schleuter, M.H., 2006: Master’s Thesis, U. of Utah)

HOMOGENEOUS

INHOMOGENEOUS EXTREME

or

(Brenguier, J.-L.,and F. Burnet, 1996: 12 th Int. Conf. Clouds and Precip; Zurich; 67-70)

14(Blyth A.M., and J. Latham, 1991: J.A.S., 48, 2367-2371)

(Gerber, H., et al, 2000: 13th Int.Conf. Clouds and Precip., Reno, NV, 105-108)

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COMPOSITE OF 35 CuCOMPOSITE OF 35 Cu

IN

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RICO, RF12

c zce

fractional entrain.scalar = qT

c = cloude =environment

COMPOSITE FRACTIONAL ENTRAINMENT

.0062

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TKE (diss. rate) = [v’(rms)]3/L

L = penetration length = 40m

v’ = gust velocity

COMPOSITE TKE DISSIPATION

TKE INHOMOGENEOUS

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CLOUD EDGE

(Brenguier, J.-L, 1993: J. Appl. Meteor., 32, 783-793)

-60 -50 -40 -30 -20 -10 0 10 20

1000 Hz

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COMPOSITE OF ENTRAINED PARCEL LENGTH

(Brenguier, J-L, and W.W. Grabowski, 1993: J. Atmos. Sci., 50, 120-136)

(Kreuger, S.K., et al, 1997: J. Atmos. Sci., 54, 2697-2712)

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COMPOSITE OF ENTRAINED PARCEL PENETRATION

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ENTRAINMENT SHEATH

NO HOLES SMALLPARCELS

DILUTIONDILUTIONDOMINATESDOMINATES RH HALO?

NEW CCNACTIVATION

VORTEX RINGS?

SUPER-ADIABATIC DROPS?

ENTRAINMENT CONCEPTENTRAINMENT CONCEPT

X

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TURRET SPECTRATURRET SPECTRA

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THANK YOUTHANK YOU

hgerber6@comcast.nethgerber6@comcast.net

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RF12 MODELING RECOMMENDATION

It is proposed that modelers consider conditionally sampling the Cu in their LES domain for RICOflight RF12 to mimic horizontal aircraft passes through “active” Cu turrets (> than 80% positive w in LWCregions) about 200 m below cloud top at 5 specified heights above cloud base. This sampling would then besimilar to the conditional sampling done using aircraft-pass data on RF12 at the same heights to establish a35-cloud subset of the approximately 200 total number of Cu found in all stages of their life times (see theplot and the tables below; the red bars in the plot indicate the Cu chosen for the “active” Cu datacompilation, and the blue bars indicate other Cu of interest. Note that at the topmost level 5, the Cu havemostly exceeded their levels of neutral buoyancy so that most can no longer be considered “active”.) Therationale of the recommended modeling is as follows:

1) Given earlier radar observations in SCMS Cu, processes of coalescence and collection leading toprecipitation initiation may occur near cloud top and in cloud volumes with maximum LWC. The proposedconditional sampling of the model domain may more closely relate modeling results to these processes thangenerating cloud profiles of the entire model domain which would include Cu in all phases of their lifetimes.

2) Conditionally sampling RF12 Cu as done here with observations is an attempt to describe the verticalevolution of the Cu. Given that “random” horizontal cloud passes are used for this approach does notguarantee that the proper vertical time dependence of the evolution of individual Cu turrets near their cloudtop has been established. The recommended modeling and comparison with the observations wouldaddress this observational uncertainty.

The choice of RF12 for detailed analysis is based on a somewhat higher than average observeddroplet concentration in RICO Cu, and a sufficient number of aircraft cloud passes at 5 levels located over asignificant height. The former may have prevented significant heavy precipitation thus simplifying analysis,but the latter also caused at the higher levels coalescence and some precipitation making this flightconsistent with RICO goals. RF12 vertical profiles of V and qt in and above the Cu are quite similar to atleast one of the flights chosen by the GCSS boundary-layer working group as containing “typical” trade-windCu.

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Table 1 - Sampled Cu on RICO flight RF12; cloud pass No. and time location inarchived data (UTC, hr:min:s).

Cu No. Time Location Cu No. Time Location

1 17:12:10-17:12:12 25 19:21:07-19:21:12 2 19:58:12-19:58:17 26 17:33:57-17:34:03 3 16:48:25-16:48:30 27 19:02:58-19:03:05 4 17:02:16-17:02:19 28 17:59:56-17:59:57 5 16:43:58-16:44:04 29 18:13:29-18:13:34 6 17:03:42-17:03:47 30 19:37:57-19:38:09 7 19:41:56-19:42:01 31 19:12:13-19:12:21 8 17:17:43-17:17:49 32 18:11:18-18:11:26 9 19:51:27-19:51:34 33 18:03:25-18:03:30 10 19:03:13-19:03:18 34 17:59:28-17:59:45 11 18:59:08-18:59:12 35 17:56:34-17:56:45 12 18:54:05-18:54:12 36 18:26:05-18:26:09 13 19:41:17-19:41:20 37 18:29:56-18:30:02 14 18:51:08-18:51:13 38 17:41:24-17:41:30 15 17:33:51-17:33:53 39 18:14:41-18:14:55 16 17:16:59-17:17:15 40 17:05:04-17:05:19 17 19:00:30-19:00:36 41 18:27:09-18:27:13 18 17:22:19-17:22:32 42 18:23:14-18:23:22 19 16:57:08-16:57:17 43 18:04:47-18:04:53 20 19:01:56-19:02:02 44 18:25:10-18:25:26 21 17:35:25-17:35:31 45 18:32:45-18:32:53 22 17:42:07-17:42:11 46 18:25:17-18:25:25 23 19:32:24-19:32:30 47 18:29:17-18:29:22 24 17:49:26-17:49:35

Table 2 - Conditionally sampled Cu turrets for each of the five main levels of aircraftpasses.

Level Cu No.

1 3,4,5,6,7,8,9 2 10,11,12,13,14,17,20 3 18,21,23,24,25,26,30 4 29,32,33,34,35,39,43 5 37,41,42,44,45,46,47

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Table 3 - General characteristics of the cloud turrets listed in Table 2, with mean values of cloud topzt, cloud top minus aircraft level za, aircaft level minus zo = LCL ~ 570 m, width of the turret W,length La of the aircraft pass in the turret, vertical velocity w, maximum vertical velocity wmax (wbased on 4-m resolution data), bulk TKE dissipation = V’(rms)3/L where V’ is the turbulent velocityand L is the “penetration length” chosen as 40 m, and fractional entrainment ~ (qtc /z )/(qtc - qvewhere the total water mixing ratio incloud is qtc and the vapor mixing ratio in the cloud-freeenvironment is given by qve. s(xxx) indicates the mean of the sample standard deviation s for allcloud passes at the given level, and s[xxx] indicates s for the mean of the parameter xxx at the givenlevel.

Level za -zo zt zt -za W s[W] La w s(w) wmax s[] s[] (m) (m) (m) (m) (m) (m) (m/s) (m/s) (m/s) (cm2/s3) (cm2/s3) (1/m) (1/m)

1 252 1009 187 544 162 331 1.18 .791 2.40 14.01 6.75 2.29e-3 1.28e-3 2 439 1205 196 484 261 266 1.25 1.13 3.01 41.34 16.26 1.26e-3 .54e-3 3 615 1398 213 453 168 402 1.92 1.58 4.28 63.24 46.76 .73e-3 .23e-3 4 918 1722 234 612 185 454 1.90 1.67 4.88 74.61 42.37 .91e-3 .13e-3 5 1074 1920 276 631 187 407 -.283 .869 1.29 29.00 32.90 6.12e-3 - - - -

Table 4 - Microphysics of the turrets listed in Table 2, with mean values of liquid water content LWCand its sample standard deviation for three horizontal data resolutions, droplet concentration N, andmean volume radius rv. The latter two parameters correspond to 10-m resolution data. The subscripta indicates expected adiabatic values, and s(xxx) and s[xxx] have the same meaning as in Table 3.

Level LWCa LWC s(10 cm) s(50 cm) s(1000 cm) N s[N] rva rv s(rv) (g/m3) (g/m3) (g/m3) (g/m3) (g/m3) (No/cc) (No/cc) (um) (um) (um)

1 .605 .284 .084 .078 .063 95 12 11.4 9.2 2.0 2 1.00 .427 .142 .136 .128 97 22 13.5 10.6 3.1 3 1.42 .520 .160 .153 .145 112 25 15.2 10.2 1.7 4 2.11 .536 .196 .184 .173 116 11 17.3 10.6 2.4 5 2.46 .331 .142 .135 .125 54 35 18.2 11.9 3.7

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Table 5 - Pressure, temperature, and vapor mixing ratio for the cloud turrets listed in Table 2, with meanvalues of pressure P, potential temperature , virtual potential temperature v, and vapor mixing ratio qv.Subscripts c and e correspond to cloud and environment, and incloud temperatures were obtained byassuming saturation and applying the Clausius-Clapeyron relationship to measured qvc. v =vc - ve. Themeaning of s(xxx) and s[xxx] remains the same.

Level 1 2 3 4 5

P (mb) 923.3 902.9 885.4 854.3 838.4c (K) 298.78 299.24 300.54 301.80 301.56s[c] (K) .33 .59 .47 .32 .31vc (K) 301.41 301.64 302.90 303.98 303.60 s(vc) (K) .36 .66 .53 .36 .34e (K) 299.29 300.20 300.52 301.81 302.79s[e] (K) .38 .24 .29 .32 .18ve (K) 301.64 302.34 302.54 303.74 304.47s(ve) (K) .38 .21 .24 .31 .13v (K) -.24 -.70 .36 .25 -.87s(v) (K) .40 .74 .55 .56 .28qvc (g/Kg) 14.84 13.85 13.80 12.74 11.54 s[qvc] (g/Kg) .31 .52 .41 .26 .22 qve (g/Kg) 12.92 11.68 11.03 10.46 9.10 s[qve] (g/Kg) .62 .67 .57 .32 .48

Table 6 - Geometric description of the entrained parcels averaged for all levels listed in Table 2. Thehorizontal length as determined from 10-cm resolution LWC measurements, and the penetration depth intothe Cu of the entrained parcels are both well described by lognormal distributions. The geometric meanentrained parcel length is Lg , geometric standard deviation of the length is L, geometric mean penetrationdepth is Pg, and geometric standard deviation of the penetration depth is P

LgLPgPm) (m) (m) (m)

1.6 2.6 8.9 2.9

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SPARE SLIDES FOLLOW

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Cu

(Courtesy of Dr. Jim Hudson)

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Turb.(s) = (D2 / TKEdiss.)1/3

Drop(s) = 4r2 / [4x10-10 x (1-S)]

RELAXATION TIME ANALYSISRELAXATION TIME ANALYSIS

D = entrained parcel width (m)r = droplet radius [10--5 (m)]

Drop(s)Turb.(s)

Drop(s)Turb.(s)

R =

R =

>> 1

<< 1 INHOMOGENEOUS MIXING

HOMOGENEOUS MIXING

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S .77 .99drop(s) 5 100 D(m) 2 20 2 20turb(s) 8.5 40 8.5 40 R .59 .12 12 2.5

RELAXATION TIME RATIO, R

CLOUD #21

35(Damiani, R., G. Vali, and S. Haimov, 2006: J.A.S., 1432-1450)