Related Manuals for Droplet CAS-DPOL
Summary of Contents for Droplet CAS-DPOL
- Page 1 Cloud Aerosol Spectrometer Depolarization Option (CAS-DPOL) Operator Manual DOC-0167 Revision E-3 2400 Trade Centre Avenue Longmont, CO 80503 USA A L L R I G H T S R E S E R V E D...
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Page 2: Software License
General Information In no event will Droplet Measurement Technologies, LLC (DMT) be liable for direct, indirect, special, incidental or consequential damages resulting from any defect or omissions in this manual. DMT reserves the right to make changes to this manual and the products it describes at any time, without notice or obligation. -
Page 3: Table Of Contents
Cloud Aerosol Spectrometer-Depolarization Option (CAS-DPOL) Manual C O N T E N T S Software License ......................2 Warranty ........................2 Overview ........................5 Theory and Implementation ................... 5 CAS Design ..........................5 Early Evolution of the Instrument ..................7 Addition of Polarization Feature ................... - Page 4 Figure 6: Theoretical Forward-to-Depolarized-Backscatter Ratios for the Configuration of the CAS ......................... 11 Figure 7: Primary Components of the CAS-DPOL’s Optical Block ........11 Figure 8: Theoretical Cross-Sections as a Function of Size for the Refractive Indices of Water and Glass Calibration Beads ................13 Figure 9: Representative Frequency Distributions for Calibration of the CAS-DPOL Detectors with 15-μm Glass Beads .................
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Page 5: Overview
(CAS) that is part of the cloud aerosol and precipitation spectrometer (CAPS) developed in 2000 (Baumgardner et al., 2001). The primary difference between the CAS-DPOL and the CAS is the addition of a method to measure the amount of depolarization caused by aspherical particles so that the instrument can more sharply differentiate water from ice in clouds or dust and biological particles from other aerosol particles. -
Page 6: Figure 1: The Primary Components Of The Cas Optical Block
This is based on the fact the angular pattern of light from a particle is a function of the wavelength of light, diameter, shape and refractive index. Figure 2 illustrates this for two sizes and two refractive indices. DOC-0167 Rev E-3 © 2018 DROPLET MEASUREMENT TECHNOLOGIES... -
Page 7: Early Evolution Of The Instrument
Cloud Aerosol Spectrometer-Depolarization Option (CAS-DPOL) Manual 1.2 Early Evolution of the Instrument The relationship between a particle’s light pattern, diameter, shape and refractive index was first utilized in an airborne instrument with the multiangle aerosol spectrometer (MASP) that was designed to measure aerosol particles in the stratosphere and derive their composition from estimates of the refractive index (Baumgardner et al., 1996). -
Page 8: Figure 3: Scattering Cross-Sections As A Function Of Diameter And Refractive Index
For the example of 5 μm particles, forward to back ratios less than 60 are only for spherical particles and greater than 80 are only for aspherical ice particle. DOC-0167 Rev E-3 © 2018 DROPLET MEASUREMENT TECHNOLOGIES... -
Page 9: Addition Of Polarization Feature
Cloud Aerosol Spectrometer-Depolarization Option (CAS-DPOL) Manual Figure 4: The Ratio of Forward to Backscattering for the CAS as a Function of Refractive Index (for Spherical Particles) or of the Aspect Ratio 1.3 Addition of Polarization Feature Whereas the forward to backscattering has now been established as useful for both refractive index and shape determination, it is somewhat limited in the number of sizes where unique information can be extracted. -
Page 10: Figure 5: Theoretical Estimates Of Light Scattering And Depolarization For Various Ice Crystal Habits
The new design adds a detector and a beam splitter in the backscattering optical path and a polarization filter, rotated 90º from the polarization of the laser, is placed in front of the second backscattering detector. DOC-0167 Rev E-3 © 2018 DROPLET MEASUREMENT TECHNOLOGIES... -
Page 11: Figure 6: Theoretical Forward-To-Depolarized-Backscatter Ratios For The Configuration Of The Cas
4000 Very rough aggregate 3000 2000 1000 Maximimum Length ( m) Figure 6: Theoretical Forward-to-Depolarized-Backscatter Ratios for the Configuration of the CAS Figure 7: Primary Components of the CAS-DPOL’s Optical Block DOC-0167 Rev E-3 © 2018 DROPLET MEASUREMENT TECHNOLOGIES... -
Page 12: Calibration
Also, as in the regular CAS, due to the wide range of scattering signals over the nominal size range of the CAS and CAS-DPOL, the conditioning and digitization of the detector signals requires three stages of amplification, designated high, medium and low. -
Page 13: Figure 8: Theoretical Cross-Sections As A Function Of Size For The Refractive Indices Of
15 - 19 m. If we believe the Mie scattering theory, and we do since it has been verified experimentally in many laboratory studies, we can convert the signal voltage of the CAS with only a single point measurement. -
Page 14: Figure 9: Representative Frequency Distributions For Calibration Of The Cas-Dpol Detectors With 15-Μm Glass Beads
0.4 1000 1050 1100 1150 1200 1250 1300 1350 1400 1450 1500 Backward-NonPol Scattering Counts 1800 1850 1900 1950 2000 2050 2100 2150 2200 Forward Scattering Counts Figure 9: Representative Frequency Distributions for Calibration of the CAS-DPOL Detectors with 15-μm Glass Beads DOC-0167 Rev E-3 © 2018 DROPLET MEASUREMENT TECHNOLOGIES... -
Page 15: Processing And Analyzing The Particle By Particle Information
Cloud Aerosol Spectrometer-Depolarization Option (CAS-DPOL) Manual Processing and Analyzing the Particle by Particle Information 1.4 Derivation of Refractive Index The refractive index is derived using a look-up table that has the theoretical values for the forward and backward scattering cross sections as a function of refractive index. As shown for three refractive indices, in Fig. -
Page 16: Figure 10: Forward And Backscattering Cross-Sections As A Function Of Refractive Index
3.81E- 7.00E-09 7.49E-09 6.75E-09 4.67E-09 2.24E- 4.02E- 4.72E- 1.23E- 2.01 1.65E-08 9.11E-09 3.90E-08 2.87E-08 1.22E- 1.67E- 1.46E- 2.88E- 3.01 8.07E-08 6.16E-08 4.24E-08 6.20E-08 2.16E- 1.48E- 4.10E- 5.88E- 4.01 5.03E-08 8.06E-08 4.30E-08 7.80E-08 DOC-0167 Rev E-3 © 2018 DROPLET MEASUREMENT TECHNOLOGIES... - Page 17 Cloud Aerosol Spectrometer-Depolarization Option (CAS-DPOL) Manual Size fwdrf1.3 bckrf1.3 fwdrf1.4 bckrf1.4 fwdrf1.5 bckrf1.5 fwdrf1.6 bckrf1.6 (um) 7.40E- 9.50E- 1.15E- 1.10E- 8.96E-12 1.35E-11 2.31E-11 3.38E-11 5.69E- 8.11E- 9.49E- 8.22E- 1.93E-10 2.76E-10 4.37E-10 6.13E-10 3.01E- 2.85E- 1.62E- 3.81E- 7.00E-09 7.49E-09 6.75E-09 4.67E-09 2.24E-...
- Page 18 34.01 1.85E-06 1.53E-06 1.18E-06 9.93E-07 2.10E- 5.51E- 1.59E- 3.45E- 36.01 1.94E-06 1.68E-06 1.27E-06 1.11E-06 2.83E- 6.10E- 1.88E- 3.85E- 38.01 2.17E-06 1.88E-06 1.38E-06 1.25E-06 2.70E- 6.76E- 1.93E- 4.33E- 40.01 2.36E-06 1.97E-06 1.65E-06 1.34E-06 DOC-0167 Rev E-3 © 2018 DROPLET MEASUREMENT TECHNOLOGIES...
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Page 19: Derivation Of Asphericity
Cloud Aerosol Spectrometer-Depolarization Option (CAS-DPOL) Manual Size fwdrf1.3 bckrf1.3 fwdrf1.4 bckrf1.4 fwdrf1.5 bckrf1.5 fwdrf1.6 bckrf1.6 (um) 7.40E- 9.50E- 1.15E- 1.10E- 8.96E-12 1.35E-11 2.31E-11 3.38E-11 5.69E- 8.11E- 9.49E- 8.22E- 1.93E-10 2.76E-10 4.37E-10 6.13E-10 3.01E- 2.85E- 1.62E- 3.81E- 7.00E-09 7.49E-09 6.75E-09 4.67E-09 2.24E-... - Page 20 (F2Bpol) and 3) nonpolarized to polarized backscatter ratio (noPOL2POL). Given that the prototype CAS-DPOL generates the two sets of files for the two pairs of forward and back detectors, these two files need to be merged into a single file before calculating the ratio of nonpolarized to polarized backscatter.
- Page 21 Cloud Aerosol Spectrometer-Depolarization Option (CAS-DPOL) Manual DOC-0167 Rev E-3 © 2018 DROPLET MEASUREMENT TECHNOLOGIES...
- Page 22 The vertical bars show the standard deviation around the mean. DOC-0167 Rev E-3 © 2018 DROPLET MEASUREMENT TECHNOLOGIES...
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Page 23: Appendix A: References
Cloud Aerosol Spectrometer-Depolarization Option (CAS-DPOL) Manual Appendix A: References Baumgardner, D., J.E. Dye, B. Gandrud, K. Barr, K. Kelly, K.R. Chan, 1996: Refractive indices of aerosols in the upper troposphere and lower stratosphere, Geophys. Res. Lett, 23, 749-752. Baumgardner, D., H. Jonsson, W. Dawson, D. O’Connor and R. Newton, 2001: The cloud, aerosol and precipitation spectrometer (CAPS): A new instrument for cloud investigations, Atmos. -
Page 24: Appendix B: Revisions To Manual
Removed schematics in accordance with new policy Appendix C Added information on the DMT Instrument Locator Appendix C 5/1/12 Corrected units for IAT (milliseconds, not 20-nsec increments) 5/22/14 Removed incorrect reference to Appendix B DOC-0167 Rev E-3 © 2018 DROPLET MEASUREMENT TECHNOLOGIES... -
Page 25: Appendix C: Dmt Instrument Locator-Operator Guide
Guide Purpose The Droplet Measurement Technologies (DMT) Instrument Locator tests whether a DMT instrument is responsive to an initialization command. This can be useful in determining if an instrument is powered on and has functional communications lines, or in verifying the serial port number that each instrument is connected to. -
Page 26: Figure 11: Instrument Locator
COM port is actually of the correct type. Thus, if you have multiple instruments in your system, it is important to specify the correct COM port for the instrument you wish to test. DOC-0167 Rev E-3 © 2018 DROPLET MEASUREMENT TECHNOLOGIES...
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