Raman and elastic lidar techniques for aerosol observation at CIAO F. Madonna, A. Amodeo, I. Binietoglou, G. D Amico, A. Giunta, L. Mona, G. Pappalardo Consiglio Nazionale delle Ricerche, Istituto di Metodologie per l Analisi Ambientale (CNR-IMAA) madonna@imaa.cnr.it
Raman vs Elastic: background Raman: α+β with no assumption on the lidar ratio S (only angstrom coefficient assumed χ, with low errors) Advanced lidar technique (multi-wavelength) Elastic: β using Klett or Fernald methods, assumption of S, constant throughout the profile (layer). Basic lidar tecnique (including ceilometers)
Potenza EArlinet Raman Lidar (PEARL) LASER: ND:YAG (Continuum Powerlite Precision II 9050) Max. pulse energy : 1200mJ @1064nm 600mJ @532nm 350mJ @355nm Max. repetition rate 50Hz Beam divergence 0.25 mrad (beam expander 2X with remixing) RECEIVER: Cassegrain Telescope Diameter of the primary mirror 0.5 m Combined focal length Nighttime field of view Achromatic lens Ø=2, f=50cm 5m 1 mrad CHANNEL SELECTION Interference filters (FI), bandwidth 0.5 nm Polarizer beam splitter (BK7) a 532 nm (POL) Dichroic mirrors (DM e HT) Selection of high and low altitude channels PMT ACQUISITION Fotomultipliers (PMT) THORN EMI 9202QA 532, 532^, 532, 607 nm 9893/350B 355, 386 nm EG&G MCS PCI (100ns min dwell time, 150MHz photon counting) APD 1064 nm Licel Transient recorder (12bit 20 MHz analogic, 250 MHz photoncounting) Operational since 2000 (upgrade in 2005 of a pre-existing lidar system) FI1064 HT APD DM FI407 FI355 DM DM FI532 FI607 POL DM FI386 PMT PMT BS PMT PMT PMT Madonna et al., Atmos. Meas. Tech. Discuss., 2010 PMT M CNR-IMAA, Tito (PZ), 14 September 2009
MUSA: MUltiwavelenght System for Aerosol LASER: ND:YAG (Continuum Surelite II-20) Max. pulse energy : 550mJ @1064nm 250mJ @532nm 120mJ @355nm Max. repetition rate 20Hz Beam divergence 0.6 mrad RECEIVER: Cassegrain Telescope Diameter of the primary mirror Combined focal length Nighttime field of view Achromatic lens 0.3 m 950 mm 1 mrad Ø=9mm, f=100mm CHANNEL SELECTION Interference filters (FI), bandwidth 0.5 nm Polarizer beam splitter (BK7) at 532 nm (POL) Dichroic mirrors (DM e HT) ACQUISITION Fotomultipliers (PMT), Hamamatsu R7400P-06 355, 387, 532, 532 nm R7400U-20 607nm APD 1064nm Licel Transient recorder (12bit 40 MHz analogic, 250 MHz photoncounting) Operational since April 2009 EARLINET Mobile Reference System CNR-IMAA, Tito (PZ), 14 September 2009
3β+2α+δ analysis from Raman lidar 10 8 355 532 1064 PEARL - Potenza, Italy, (40.60 N, 15.73 E), 20 April 2010, 21:00-23:05 UTC b 5 32 +b b 5 32 +b a 3 55 +a 1 064 3 55 5 32 Altitude a.s.l. (km) 6 4 2 0 0.000 0.002 0.004 0.006 Back. Coeff. (sr -1 km -1 ) 0.00 0.05 0.10 0.15 0.20 Ext. Coeff. (km -1 ) 0 60 120 Lidar Ratio (sr) -2 0 2 4 Angström exponent 0.0 0.2 0.4 Particle Linear Depolarization ratio Mona et al., 2011, Atmos. Chem. Phys., submitted CNR-IMAA, Tito (PZ), 14 September 2009
Ceilometers CT25K 905 nm ceilometer Operational since August 2004 CHM15K 1064 nm ceilometer Operational since July 2009 CNR-IMAA, Tito (PZ), 14 September 2009
Sensitivity: 10/10/2010 PEARL RCS@1064 nm u.a. CHM15k RCS@1064 nm u.a. 7.5 6.0 Height (m a.g.l.) 4.5 3.0 1.5 AOD 532nm = 0.12 0.0 20 21 22 UTC 20 21 22 UTC
Ceilometer calibration CT25K unattenuated backscattering only (Mona et al. 2009) CHM15k signal 1064 nm 12000 10000 CIAO - Tito Scalo 10102010 19:15-20:15 UTC CHM15k PEARL 12000 10000 CIAO - Tito Scalo 10102010 19:15-21:15 UTC CHM15k PEARL 8000 8000 Height (m a.g.l.) 6000 4000 Height (m a.g.l.) 6000 4000 2000 2000 0 0 0.01 0.1 1 10 100 1000 1E-3 0.01 0.1 1 10 100 1000 1064 nm signal (u.a) 1064 nm signal (u.a)
Influence of the lidar-ratio assumption on backscatter retrievals: 27/05/2008 5000 Raman S30 S50 S80 Raman S30 S50 S80 Height (m a.g.l.) 4000 3000 2000 355 nm 532 nm 1000 0.000000 0.000002 0.000004 Backscattering coefficient (m -1 sr -1 ) Böckmann et al., 2004; Pappalardo et al., 2004 0.000000 0.000001 0.000002
Aerosol mask Mona et al. ACP special issue, submitted. Minimum and maximum investigated altitudes PBL top height PBL Aerosol Mixed aerosol Volcanic aerosol b1064>2 e-6 m-1 sr-1 5e-8<b1064<2 e-6 m-1 sr-1 b1064<5 e-8 m-1 sr-1 Cloud/cirrus Desert dust Forest Fires Aerosol UnknownAerosol
Lidar Radar synergy 19 April 2010 Lidar start time: 19:47 UT Radar: 24h operational
Observation of ultragiant aerosol CIAO, Tito Scalo, 19042010 2020 UTC 10 min 60 min 0 60 120 Lidar Ratio (sr) Integration time: 10 minutes Lidar vertical resolution: 30-300 m Ultragiant aerosol layer detected by the radar, characterised by high LDR values, is located between about 1.4 and 2.1 km above the ground. This layer is completely included in the lower volcanic aerosol layer observed by the lidar and characterized by a maximum value of the 355 nm volume backscattering coefficient of 2.3 Mm-1 sr-1. Madonna et al., (2010), Geophys. Res. Lett., 37, L21814, doi:10.1029/2010gl044999.
Summary Aerosol layering in the low tropopshere Elastic (sensitivity assessment for ceilometers) Alerting system Elastic + backtraj ok in a preliminary phase, Aerosol masking using advanced Raman lidars Aerosol typing, optical and microphysical properties Raman (+depolarization) Integrated products Raman
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