1. Lidar remote sensing for the characterization of the atmospheric aerosol on local and large spatial scale

2. Atmospheric aerosol What are THEY and why are THEY so important? Minute particles suspended in the atmosphere Aerosols interact both directly and indirectly with the Earth’s radiation budget and climate Aerosols reflect or absorb sunlight Aerosols modify the size of cloud particles, changing how the clouds reflect and absorb sunlight WHAT ABOUT THE ESTIMATION OF THEIR EFFECTS? MOTIVATION

5. from Intergovernmental Panel Climate Change

6. INTERACTION LIGHT - ATMOSPHERE Elastic scattering Anelastic scattering   Mie scattering Rayleigh scattering x << 1 molecules Rayleigh scatteringMie scattering Mie scattering, larger particles Direction of incident light  A    E Raman scattering Information on the species concentration

7. LIDAR remote sensing

8. THE REMOTE SENSING LIDAR TECHNIQUE Sorgente laser Nd-Yag Laser Receiver LIght Detection And Ranging Signal processing

9. ELASTIC LIDAR EQUATION (SINGLE SCATTERING) z: altitude : wavelength 1 equation 2 unknown parameters + a priori hypothesis Lidar Ratio (LR) P L : laser power Standard Atmosphere vertical resolution  : efficiency β = β m + β a backscatter coefficient  m  a  extinction coefficient acceptance angle

10. RAMAN LIDAR EQUATION (SINGLE SCATTERING) No a priori hypothesis 1 Elastic lidar equation + 1 Raman lidar equation 2 unknown parameters

11. RCS - RANGE CORRECTED SIGNAL = P(z)*z 2 PBL height Planetary Boundary Layer Directly influenced by the presence of the Earth's surface Aerosol as tracers Time (UT) 18:00 20:00 22:00 24:00 02:00 04:00 06:00 Height above lidar station (m) 7000 6000 5000 4000 3000 2000 1000 RCS @ 532 nm (a.u.) Naples, 9-10 May 2005

12. EARLINET (European Aerosol Research LIdar NETwork) Since May 2000 ARPAC Naples station (40.833°N, 14.183°E, 118 m. asl) regular measurements twice a week special measurements (Saharan dust, forest fires, volcanic eruption, etc…) intercomparison both for hardware and software 25 stations

13. THE NAPLES LIDAR SYSTEM Diaphragm Collimating Lens 407 387 387 High 387 Low 407 387 407 355 532 355 High 355 Low 355 > 532 532 532 High 532 Low 607

14. CLOUD SCREENINGSharp variation cloud RCS (a.u.) Height (m) 0 5000 10000 15000 20000 10 8 10 9 10 10 11 PRE - PROCESSING DATA

15. PILE UP CORRECTION Measure the same signal: - D 1 at low acquisition rate (< 500kHz) - D 2 at working condition Polinomial fit Rate D 2 (MHz) Rate D 1 (MHz)

16. PRE - PROCESSING DATA MERGE Height (m) 0 5000 10000 15000 20000 10 8 10 9 10 10 11 Analog – low height Photocounting – high height RCS (a.u.)

17. CALIBRATION Height (m) 0 5000 10000 15000 20000 10 8 10 9 10 10 11 RCS (a.u.) PRE - PROCESSING DATA Molecular signal “Clean” air

18. Depolarization measurement Why? Function of the particles’ morphology Identification of solid and liquid phases of the particles

19. How do we perform linear depolarization measurements? 1.Use a linearly polarized laser source 2.Align a detecting channel (P channel) in the same direction of the initial polarization of the laser 3.Align another detecting channel (S channel) orthogonal with respect to the laser initial direction of polarization 4.Calibration of the system

20. Total Depolarization coefficient Defined as: Is the backscattering coefficient S(z) and P(z) are the ortoghonal and parallel signals H is the calibration constant k takes into account the instrumental effects

21. Aerosol Depolarization coefficient Molecular depolarization (0.00376) R Backscatter ratio Total depolarization coefficient

22. How do we calibrate depolarization channels? The calibration constant measures the relative efficiency of the polarization channels. There were studied and evaluated 4 techniques: 1.Rayleigh method 2.90° rotation of the polarization of the laser 3.45° rotation 4.Depolarization

23. Eyjafjallajökull

24. Depolarization by ETNA volcanic particles