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Rapid & Continuous Measurement of Supersaturation spectra

Why SFCA? Scanning Flow CCN Analysis Cerina, Staffan, Göran & Birgitta Original developers: Rich Moore & Nenes. Rapid & Continuous Measurement of Supersaturation spectra Express Timescales (Airborne measurements, chamber - ageing) Small Samples for Analysis As good as Stepping-ΔT-Mode?

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Rapid & Continuous Measurement of Supersaturation spectra

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  1. Why SFCA?Scanning Flow CCN AnalysisCerina, Staffan, Göran & BirgittaOriginal developers: Rich Moore & Nenes Rapid & Continuous Measurement of Supersaturation spectra Express Timescales (Airborne measurements, chamber - ageing) Small Samples for Analysis As good as Stepping-ΔT-Mode? Colder than usually (no heating of aerosol required) – less volatility losses

  2. Why? How? • How does the traditional Stepping-ΔT-Mode (CFSTGC) work…? • …compared with how the SFCA works? Results? • Calibration, Brockenlongterm Saving time – before it took a while to stabilize the temperature, with SFCA the flow is changed fast

  3. This is how the CFSTGC works… • Diffusion of heat in air (N2 O2) is slower than diffusion of water vapor • The partial pressure of water vapor at center (C) is equal to pointB. However, the temperature is equal to point A – hencethere is more water vaporthanthermodynamicallyallowed and supersaturation is generated

  4. …and the SFCA Higher flow will increase the difference between the partial pressure of water vapor & temperature, and thereby increase the supersaturation

  5. Results - Calibration

  6. Results - Calibration

  7. Comparison with data from Rich(similartestruns 6K/120s/20s)

  8. Doublecharged FIG. 6c. Zoom-in on double charged particles for 120 sflowscan for laboratory-generated, 70 nm ammoniumsulfate aerosol at P ∼ 1010 mb and ∆Tnom= 6 K.

  9. Results – Brocken 1142 m

  10. Results – Cloud on Brocken 1142 mSteamtrain time table arrival 12:51 departure 13:14

  11. Following the aerosol particle through the column (10-20 s)(using CFTGC vs. SFCA) SFCA Axial Distance From Inlet 0.0 SS [%] Temp [oC] Flow [cm3min-1] 0.5 CFSTGC 0.0 Axial Distance From Inlet 0.5 SS [%] Temp [oC] Flow [cm3min-1]

  12. Problems encountered? Downscan – lowSS - the dropscan be toofew and too small for the OPC detection limit Water level to low? Nenes: ”…is somechanneling in the ceramicbisquelining (perhapssomecracking from prolongeduse). Also, double-check that the OPC is clean.”

  13. Outlook Cooperation with Rich Moore and Nenes? – fast scansarticle Brocken data Chamber measurements Vavihill or new ICOS site

  14. Conclusion Better time resolution, moreappropriate for atmosphericconditions Reliable, butmaybemore service (pump)? Not fullyunderstood

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