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Cloud Condensation Nuclei _CCN_water-soluble particles that cloud

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Cloud Condensation Nuclei _CCN_water-soluble particles that cloud Powered By Docstoc
					Cloud Condensation Nuclei (CCN)—water-soluble
 particles that cloud droplets condense upon.
10-1000 nm or 0.01-1 µm or 10-6-10-4 cm.
                      ( ),
CCN concentrations vary from 1-105 cm-3
CCN determine cloud droplet (5-50 µm) concentrations,
which vary from 1-104 cm-3
CCN are amplified by cloud condensation from 10 to
10,000 nm (0.01 to 10 µm). Thousand in size, million in
surface area, billion in volume!
DRI Cloud condensation nuclei (CCN) spectrometers.

Produce a field of supersaturations (S) by thermal diffusion
of temperature and water vapor between two parallel plates,
where cloud droplets grow on hygroscopic sample
particles.
More hygroscopic (e.g., larger) particles produce larger
cloud droplets.
Continuous flow through the cloud chamber (~30s) then
into an optical particle counter (OPC). CCN spectrum is
deduced from the OPC droplet spectrum. A calibration
curve relates OPC droplet size to particle hygroscopicity
(critical supersaturation—Sc).
Calibration is done with nuclei of known composition (e.g.,
NaCl) and size (differential mobility analyzer—DMA—
electrostatic classifier--EC).

Assumes that all CCN with the same Sc regardless of
composition (or size) produce the same droplet sizes.
Calibration holds only if all chamber parameters (i.e., flows
and temperatures) remain constant.
    Sc inversely proportional to number of soluble ions.
Traditionally CCN plots are cumulative because clouds act
cumulatively on the aerosol— all nuclei with Sc < cloud S
produce “activated” cloud droplets.

     Also previous CCN instruments had too few data
points to produce a differential spectrum.
DRI CCN spectrometers have enough data points to
produce differential spectra.
1%     Sc -- 25 nm NaCl

0.1% Sc -- 110 nm NaCl

0.02% Sc – 310 nm NaCl

other compositions must have larger sizes for the
same Sc.
             Dec 10, 2004 1226:00-1228:00 AST (1626:00-1628:00)
             C-130 RICO, Antigua 946 mb
                       -3                 -3
             CN 194 cm CCN @ 1% 47 cm


                         new spec
            100          old spec
dn/dlogSc




            10




              1
                  0.01               0.1               1

                                    Sc(%)
1. Simultaneous high time resolution CCN spectra

2. Differential CCN spectra

3. Supersaturation (S) range extended below 0.1%.
Extension the traditional CCN (Aitken) range below
0.1% to Large Nuclei, is necessary because a large
proportion of CCN have S < 0.1%. This is needed
because:
• Many clouds have S< 0.1%
• Static closure—aerosol and CCN
• Dynamic closure—CCN and cloud droplets.
• Large nuclei are embryos for precipitation.
• Droplet spectral width.
• Interface with giant nuclei.
• CCN sizes.
                                    July 19, 2005, 1205-1227 PDT MASE,
                                    CCN @ 0.3% S old spectrometer
                         900

                         910

                         920                                         ascent
                                                                     descent
pressure altitude (mb)




                         930

                         940

                         950

                         960

                         970

                         980

                         990

                         1000
                                0     500      1000         1500       2000    2500

                                             concentration (cm -3)
                                    July 15-23, 2005, MASE, CA average within pressure bins
                                    CCN 1% for research area
                          130
                                                                                   15th
                          120                                                      16th
                          110                                                      17th
                          100                                                      18th
                          90                                                       19th
altitude from cloud top




                          80                                                       20th
                          70                                                       22nd
                          60                                                       23rd
                          50                                                        cloud top
                          40
                          30
                          20
                          10
                            0
                          -10
                          -20
                          -30
                          -40
                                0          500         1000         1500         2000           2500
                                                     concentration (cm-3)
                                         Average spectra below and
                                         just above cloud for the
                                         eight flights with unbroken
                                         polluted low stratus
                                         July 15, 16, 17, 18,
                                         19, 20, 22, and 25
                                         and maritime July 6
                                             below
cumulative concentration (cm-3)


                                  1000       above
                                             July 6 below




                                   100




                                    10

                                     0.01            0.1         1
                                                    S(%)
                July 15-23 research area; average
                cumulative spectra just above cloud




      1000
N(Sc<S)




                                            15th
                                            16th
          100                               17th
                                            18th
                                            19th
                                            20th
                                            22nd
                                            23rd
           10
             0.01             0.1            1
                                S (%)
                July 15-23 research area; average
                cumulative spectra below cloud




      1000
N(Sc<S)




                                           15th
                                           16th
          100                              17th
                                           18th
                                           19th
                                           20th
                                           22nd
                                           23rd
           10
             0.01            0.1            1
                               S (%)
                                          July 23, 2005
                            800


                            700
cumulative concen. (cm-3)



                            600


                            500


                            400


                            300


                            200


                            100


                             0

                                  10:22                   10:23
                                           Time (PDT)
                       August 28, 2007 Christmas Island, PASE
                       1527-1543 XST

           700


           750


           800


           850
pres alt




           900

                                                        CN
           950                                          CCN



           1000



                  0   200         400            600       800   1000
                                  mean channel number
                    August 28, 2007, new spec C-130
                    PASE Christmas Island
      400


      350


      300


      250
CCN




      200


      150


      100


       50


        0
            11.75       12.00          12.25          12.50   12.75
                                 XST
            120
                      Nc=0.60CCN-9                    1
            100                                 14
                      R = 0.85
                                                            Figure 1. Average total (>2.4 µm)
                                                            FSSP droplet concentrations (Nc)
                                                            measured during each flight within
            80                              2               the 600-900m altitude range and
Nc (cm-3)




                                                            FSSP LWC > 0.1 gm-3 against the
                               12
                              11            6               average 100m altitude CCN
            60                           13                 concentrations at 1% S for each
                                       15
                                       10 18                flight. Data points are plotted as
                              8                             the flight number (Table 1). All of
                                                            the 17 flights considered here except
            40                    93                        RF17 (J19) had clouds within this
                                  4     Nc=0.61CCN-10       altitude range. The linear regression
                                  5
                          7             R = 0.88            line, equation and correlation coefficient
            20                                              (R) is shown as well as the linear
                                        for 14 flights      regression and R for only the same 14
                                                            flights considered by HM7 (excluding
                                                            RF4 and 11 [D10 and J7]).
              0
                  0      50       100           150   200
                              CCN (cm-3)
                                    January 16, 2005, RICO, Antigua
                                     at 1621-1635 GMT initial full descent
                  500




                  600
pres. alt. (mb)




                  700




                  800                                          CN
                                                               CCN @ ~1% S
                  900




                  1000
                         0    200    400    600   800   1000     1200   1400   1600   1800

                             particles per cm-3 normalized to sea level pres.
                                     January 11, 2005, RICO, Antigua
                                      at 2115-2128 GMT final ascent
                  500




                  600
pres. alt. (mb)




                  700




                  800



                                                                  CN
                  900
                                                                  CCN @ ~1% S

                  1000
                         0    100   200   300   400   500   600   700   800   900   1000

                             particles per cm-3 normalized to sea level pres.
                       4
                                        N = 2.7-0.01CCN
                                          R = -0.49
concentration (cm-3)


                       3            8
                                7                                 Figure 7. As Fig. 4 but for
                                        5                         1500-1800m altitude and 35
                                            10                    µm diameter. If only RF1, 5,
                                                                  7, 8, 10 and 18 are
                       2                                          considered R is -0.97. R
                                                 18               for the other seven flights in
                                                                  this figure is -0.93.

                               17
                       1
                                         9
                                        12 15
                                          3                 1
                                             13
                                                      14
                       0
                           0   50        100          150   200
                                    CCN (cm-3)
               2500



               2000                                   2.4µm
                                                      5µm
altitude (m)




                                                      10µm
               1500                                   15µm
                                                      20µm
                                                      25µm
                                                      30µm
               1000                                   35µm
                                                      40µm


                500
                      -1.0   -0.5   0.0   0.5   1.0
                                    R
                 3000
                                                                             45µm
                                                                             55µm
                 2500                                                        65µm
                                                                             75µm
  altitude (m)
                                                                             85µm
                 2000                                                        95µm
                                                                             105µm
                                                                             115µm
                 1500                                                        125µm


                 1000


                  500
                        -0.8    -0.6        -0.4         -0.2          0.0         0.2          0.4
                                                       R
Figure 11. As Fig. 5A but for drizzle drops measured by the 260X probe. This includes all flights with data
in each altitude band. This mean different numbers of flights and different flights at the various altitudes.
600-900m—16 flights (no RF17; same flights as the cloud data at this altitude noted in Fig. 5A caption);
900-1200m—15 flights (no RF13 or 17; same as cloud data noted in Fig. 5A caption); 1200-1500m—15 flights
 (no RF6 or 17; there was one more data point for the cloud data for this altitude as there was cloud data for
RF17); 1500-1800m—13 flights (no RF2, 4, 6 or 17; this differs from the cloud data, which did have RF17
data but not RF11); 1800-2400m—12 flights (no RF2, 4, 6, 9, or 15; this is one more than the cloud data
because there is drizzle data at this altitude for RF12); 2400-3000m—6 flights (no RF2, 4, 5, 6, 8, 9, 10, 12,
14, 17 or 18; the same flights as the cloud data at this altitude).
    1.0

    0.8                                                 600-900m 16 flights
                                                        900-1200m 15 flights
    0.6                                                 1200-1500m 13 flights
                                                        1500-1800m 11 flights
    0.4                                                 1800-2400m 10 flights
                                                        2400-3000m 6 flights
    0.2
R



    0.0

    -0.2

    -0.4

    -0.6

    -0.8

    -1.0
           0           50            100            150            200            250            300
                                   threshold diameter (µm)
Figure 12. Correlation coefficients (R) for 1% S CCN at 100m altitude versus cumulative drop(let)
concentrations above various size thresholds within the specified altitude ranges. This is the same
data displayed in Figs. 5A and 11 but here displayed for each altitude band as a function of drop(let)
sizes. As in those other figures the flights considered varied with altitude range and this may cause
biases. The number of flights in each altitude range is shown in the legend.
        1.0

        0.8                                                              0.50-0.55 2.1%
                                                                         0.45-0.50 2.7%
        0.6                                                              0.40-0.45 3.4%
                                                                         0.35-0.40 4.5%
        0.4                                                              0.30-0.35 4.2%
                                                                         0.25-0.30 6.3%
        0.2
                                                                         0.20-0.25 6.3%
                                                                         0.15-0.20 8.3%
 R




        0.0
                                                                         0.10-0.15 11.4%
       -0.2                                                              0.05-0.10 16.8%
                                                                         0.01-0.05 26.9%
       -0.4

       -0.6
       -0.8
       -1.0

               0                  10                  20                 30                  40                  50
                                        threshold diameter (µm)
Figure 16. As Fig. 14, but for 900-1200m altitude range. There are also eleven flights with data in these LWC
intervals. But the flights are different from the flights in Fig. 14. Here RF2, 3, 11, 13, 14 and 17 (D8, D9, J7, J12,
J14 and J19) are excluded. With the higher altitude more LWC intervals are available; 7.1% have LWC > 0.55 gm-3.
    1.0

    0.8

    0.6
                                                                                     2µm
    0.4                                                                              5µm
                                                                                     10µm
    0.2                                                                              15µm
                                                                                     20µm
R



    0.0
                                                                                     25µm
    -0.2                                                                             30µm
                                                                                     35µm
    -0.4                                                                             40µm
    -0.6

    -0.8

    -1.0
           0.0    0.1        0.2       0.3       0.4       0.5        0.6
                                                -3
                             LWC(gm )
     Figure 17. As Fig. 15 except that the data are from the 900-1200m altitude range.
     This is the same data shown in Fig. 16.
       1.0

       0.8           A
                                                                                         0.75-0.80     4.2%
       0.6
                                                                                         0.70-0.75     2.8%
       0.4                                                                               0.65-0.70     3.9%
                                                                                         0.60-0.65     2.8%
       0.2                                                                               0.55-0.60     3.6%
                                                                                         0.50-0.55     4.2%
 R




       0.0
                                                                                         0.45-0.50     4.2%
      -0.2                                                                               0.40-0.45     4.1%
      -0.4
      -0.6

      -0.8

      -1.0

              0                 10                 20                 30                40                 50
                                      threshold diameter (µm)
Figure 20. As Fig. 18 but for 2400-3000m altitude. Only four flights; RF1, 11, 13 and 15; 16% exceeded 0.80gm-3.
The 0.25-0.30 gm-3 interval with 5.8% of the data is not shown because it did not have data from all four flights.
    1.0

    0.8        B                                  0.35-0.40 5.2%
                                                  0.30-0.35 5.9%
    0.6
                                                  0.20-0.25 4.9%
    0.4                                           0.15-0.20 6.4%
                                                  0.10-0.15 5.5%
    0.2                                           0.05-0.10 6.3%
                                                  0.01-0.05 14.2%
R




    0.0

    -0.2

    -0.4
    -0.6

    -0.8

    -1.0

           0       10         20      30          40          50
                        threshold diameter (µm)
Figure 20B.
      1.0

      0.8

      0.6

      0.4
                                                                          2.4µm
      0.2                                                                 5µm
                                                                          10µm
R



      0.0
                                                                          15µm
     -0.2
                                                                          20µm
     -0.4

     -0.6

     -0.8         A
     -1.0
            0.0   0.1   0.2     0.3    0.4    0.5     0.6    0.7    0.8
                                                      -3
                        mean LWC(gm )
    Figure 21. As Fig. 19 but for 2400-3000m. Same data as in Fig. 20.
    1.0

    0.8

    0.6
                                                         B
    0.4

    0.2                                                              25µm
                                                                     30µm
R


    0.0
                                                                     35µm
    -0.2                                                             40µm
    -0.4

    -0.6

    -0.8

    -1.0
           0.0      0.1    0.2   0.3   0.4   0.5   0.6   0.7   0.8
                                                   -3
                          mean LWC(gm )
                 Figure 21B.
                                                                               Adiabaticity


                Mean          Mean          Mean         total     Adiab.    Mn/Ad
 Altitude      altitude       LWC           LWC         LWC        LWC       LWC
 range          (m)           FSSP          260X        (gm-3)     (gm-3)
  (m)                        (gm-3)         (gm-3)



 2400-3000    2660±150      0.34±0.18     0.22±0.10      0.56      2.69      0.21
 1800-2400    2010± 70      0.33±0.16     0.09±0.05      0.42      1.80      0.23
 1500-1800    1612± 87      0.29±0.10     0.04±0.03      0.33      1.25      0.26
 1200-1500    1358± 74      0.25±0.08     0.02±0.02      0.27      0.96      0.28
  900-1200    1049± 77      0.18±0.05     0.01±0.01      0.19      0.57      0.33
  600- 900     798± 33      0.10±0.02     0.01±0.01      0.11      0.24      0.46




Table 3. Altitude ranges, means and standard deviations of, measured mean
flight-averaged altitudes for LWC > 0.01 gm-3 for flights considered for correlations
within the various LWC bins in Figs. 14-21 and text, mean LWC for these flights,
adiabatic LWC at the mean altitudes, ratio of mean LWC to adiabatic LWC.
1. Regular ambient measurements. Change integration time (1s)
    and sample flow rate for better statistics but spectra may suffer
1. CCN measurements invalid in cloud so need to separate data.
     A. Splashing artifact
     B. Interstitial measurement—CCN not within droplets, but
        where is the cutoff?
3. Calibrations—usually done in flight (in cloud) because instrument
is very sensitive to changes. Confidence in data. Can be done on
ground before or after flight but conditions can be different—esp. Temp.
    Can bring cal particles in conductive plastic bags.
4. Volatility measurements--~chemistry—NaCl for sure 600-800C.
     CN/CCN comparison for clean or polluted air—less volatile
     substances are usually less soluble—ammonium sulfate is
     both soluble and volatile 200C.
5. Size/Sc measurements—CCN size. Larger CCN are less soluble
    usually polluted air mass. But PASE measurements may
    contradict this.
6. May do surface measurements with other instruments.
      Continuous, comparisons, Size/Sc, students.
                                                   July 22, 2005, 1042-1303
                                                   High Temperature Processor
                                                   @ 955-976 mb
                                         1.0


concentration ratio for HTP to ambient
                                         0.8




                                         0.6

                                                                        CN
                                                                        CCN @ 1% S
                                         0.4




                                         0.2




                                         0.0
                                               0   100   200     300    400   500    600

                                                               temp C
                             Particle critical Supersaturation (Sc)
                             versus dry particle diameter
                             January 19 and 24, 2005
                             RICO Eastern Caribbean near Antigua
                             low altitude



                   1
          Sc(%)




                  0.1
                                  NaCl
                                  Amon. Sul.
                                  J19
                                  J24a
                                  J24b
                                  J24c
              0.01
                        10                     100                1000


From Hudson 2007                      diameter(nm)
                          Particle critical supersaturation (Sc)
                          versus dry diameter
                          July 25, 2005
                          MASE off the Central California Coast
                          below and above stratus cloud layer



          Sc(%)    1




                  0.1
                                  NaCl
                                  Amon. Sul.
                                  below
                                  above
                                  below
              0.01
                        101                102                     103
From Hudson 2007                  diameter(nm)
                   Particle critical Supersaturation (Sc)
                   versus dry particle diameter
                   Nov. 24 and 25 and Dec. 4, 2003
                   AIRS2 Northeast US




         1
Sc(%)




        0.1         NaCl
                    Amon. Sul.
                    N24 urban
                    N24 above
                    N25 Lake Huron
                    D4a Lake Huron
                    D4b Lake Huron
                    D4c Lake Huron

   0.01
              10                     100               1000
                             diameter(nm)
                Particle critical Supersaturation (Sc)
                versus dry diameter
                September 2, 2007 1417-1637 local time
                PASE near Christmas Island
                low altitude



          1
Sc(%)




         0.1


                        NaCl
                        Amon. Sul.
                        ambient

        0.01
               10                100                1000
                            diameter (nm)
                    Particle critical Supersaturation (Sc)
                    versus dry diameter
                    Sep 7, 2007 0913-1507 local time
                    PASE near Christmas Island
                    low altitude



          1
Sc(%)




         0.1


                           NaCl
                           Amon. Sul.
                           ambient

        0.01
               10                    100                     1000
                               diameter (nm)
     1.6
     1.4
     1.2
     1.0
     0.8
B
     0.6
     0.4
     0.2
     0.0

       102                       103                         104
                        CN conc (cm-3)

    Figure 4. Average and standard deviation of the solubility

    parameter, B, plotted against the simultaneous average CN

    concentration during each set of size-Sc measurements.
1. Vertical differences in concentrations—layers above cloud.
2. Is there a low concentration layer right above cloud?
3. Do higher concentrations above get into cloud?
4. Will there be day-to-day variations as in RICO or
   not as in MASE?
5. CCN-droplet correlations—related to entrainment?
6. Drizzle inverse relationship?
7. Determine cloud S—related inversely to concentration?
      How related to entrainment? Causes underestimate of S.
8. FSSP missing small cloud droplets when S is low? Haze
      versus activated droplets?
9. CCN conc. related to cloudiness—cloud scavenging?
10.Volatility
11.Size-Sc, B related to concentration?

				
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