monitoring of eyjafjallajökull ash layer evolution over payerne- switzerland with a raman lidar
DESCRIPTION
Monitoring of Eyjafjallajökull Ash Layer Evolution over Payerne- Switzerland with a Raman Lidar. Todor Dinoev, Valentin Simeonov*, and Mark Parlange Swiss Federal Institute of Technology –Lausanne (EPFL), Switzerland Bertrand Calpini MeteoSwiss – Payerne, Switzerland. Outlook. - PowerPoint PPT PresentationTRANSCRIPT
Monitoring of Eyjafjallajökull Ash Layer Evolution over Payerne-
Switzerland with a Raman Lidar
Todor Dinoev, Valentin Simeonov*, and Mark ParlangeSwiss Federal Institute of Technology –Lausanne (EPFL),
SwitzerlandBertrand Calpini
MeteoSwiss – Payerne, Switzerland
Outlook
• General lidar principle• Raman lidar for water vapor, temperature and
aerosol measurements• MeteoSwiss-EPFL lidar (RALMO –Raman Lidar for
Meteorological Observation)• Eyjafjallajöekull ash layer observation• Conclusion
Lidar principle
1
0
)(2exp)()(20
z
z
drzzz
AkPzI
PI(z)
z
R
A
Laser
Telesccope
Spectral unit
Raman lidar
265 270 275 280 285 290 295 300Wavelength [nm]
Skteched spectroscopic principle
Inte
nsity
[a.
u.]
260 265 270 275 280 285 290 295 3000
5
10
15
20
25
30
laser pump wavelengths
Pure Rotational Raman O2 & N
2
Ro-vibrational O2
Ro-vibrational N2
Ro-vibrational Water vapor
)(.)( zNzR
)(
)()(
2
2
zI
zIczw
N
OH
Water vapor
H2ON2O2
Laser
1
0
),(),(exp)()(20
z
z
RLR dzzzzz
AkPzI
.)( mzaer
Temperature and aerosol measurements by the PRR
SEl
)(
)(ln)(
)(
zI
zIzA
BzT
Hj
Lj
1)(
)(
)(
)(
zI
zIc
z
z
PRR
La
mol
aer
Laser
Laser Power Supply
Water Vapor Polychromator
Aerosol / Temperature Polychromator
Lidar Windows
Laser Beam
Telescope array Beam Expander
2005 mm
Laser -400 mJ/pulse at 355 nm 30 Hz rep. rateTelescope-array of four 30 cm F#3 mirrorsPolychromators- Grating based for water vapor and temperature Telescope / polychromators fiber coupled
RALMO design
Inside view
Fibers
Fibers Output lens of theBeam Expander
Mirrors
Telescope
Telescope
Laser
H2O Polychromator
T° Polychromator
RALMO specifications•Distance range 150 m-up to 5 km day/ 12km night•Temporal resolution 30 min (optional 10 min)• Spatial resolution - variable 15-300 m•Detection limit water vapor 0.05 g/kg•Temperature resolution 0.5 K•Aerosol extinction and backscatter coefficients at 355 nm•Statistical error < 10 %•Automatic operation and data treatment•Eye safe
Operation•Water vapor channel -Experimental operation since 2007-Fully operational since 2008•Temperature/aerosol channel operational since 2009
Eyjafjallajöekull ash layer observations
Backscatter/water vapor MR
16 April 17 April 18 April
Backscatter/Relative humidity
0 20 40 60 80 1000
1000
2000
3000
4000
5000
6000
7000
8000
9000
1000022h00 UTC 16/04/2010
z, m
(A
GL)
Backscatter Ratio *100
Relative Humidity, %
0 20 40 60 80 1000
1000
2000
3000
4000
5000
6000
7000
8000
9000
1000000h00 UTC 18/04/2010
z,
m (
AG
L)
Backscatter Ratio *100
Relative Humidity, %
Backtrajectories
Ash layer over Zurich
Observation by ETHZ lidar (Thomas Peter)
Mass concentration
Conclusion
• Automated water vapor lidar for meteorological applications developed
• The lidar is in continuous operation from November 2007 at the aerological station of MeteoSwiss in Payerne.
• The data is regularly intercompared with SnowWhite and RS 92 sondes microwave radiometer, and GPS measurements.
• The lidar was upgraded with PRR channels for temperature, aerosol extinction and backscatter profiling
• Appearance and evolution of volcanic ash layer observed• Optical properties measured and mass concentration
estimated• Anti correlation between aerosol load and water vapor mixing
ratio observed
Transciever RALMO
TransmitterNd:YAG laser400 mJ & 355 nm30 Hz rep. rateBeam expander 15 X
ReceiverMatrix telescope offour mirrors30 cm in diameter0.2 mrad FOV
Time resolution - 10 min, Vertical resolution - 30 m up to 4 kmNo smooth or interpolation
High pressure – Anticyclone
‘Rain stop’Clouds/Fog < 500 m
Clouds, Rain