Transcript Document 7213585

sun- (/sky-) photometer
ground-networks
GAW - aod
AERONET
…
complementing LIDAR
SKYnet
MAN - aod
Stefan Kinne
MPI-Met, Hamburg
sun- (/sky-) photometers
• can do
– aerosol column properties
• AOD at several wavel.
• fine mode AOD fraction
• water vapor
• size distribution (sky)
• absorption AOD (sky)
• cloud opt.depth (sky)
– consistency through calibr.
networks operation
• cannot do
• applications
– calibration and reference for
lidar remote sensing
– reference in evaluations of
aerosol global modeling
– complementary nature to
lidar (at MPL-NET and most
EARLINET sites)
• AOD = integrated ext.
• limitation
– night time (need the sun)
– local nature of sample
– when clouds are present
– day-time nature of sample
– vertical stratification
– abso. less acc at low AOD
outline
• what major sun-photometer networks exist
and are recent data accessible ?
• why are aerosol properties of sun-photometry
more accurate than satellite retrievals?
• data-samples in the global context
• application sample in aerosol assimilations
• why lidar-sites should upgrade to sunphotometers (and radiometers and cloud- and
precipitation radars)  complementary nature
AERONET
Laengeren
9/20/2010 data !
 successful recent data access
Skynet
associations
are offered !
here for Hedo
April 2010
September 2010
data on the web !
successful recent
data access
GAW - AOD
no data access on the nice Swiss web-site
http://www.pmodwrc.ch/worcc (C.Wehrli)
error message on the NILU/EBAS site
MAN - AOD
sun-photo
vs. sat-retrieval
• AOD data based on solar
radiation attenuation
data … function of
• AOD based on reflected
radiances … function of
– trace-gas absorption
– trace-gas absorption
– molecular scattering
– molecular scattering
– amount matters
– amount matters
– size matters (pre-selected)
– shape matters (spheres)
• sky-radiance data of
additional info on
– size-distribution (.1-10um)
– absorption if AOD is large
(suff. signal / noise ratio)
– absorption mat. (assumed)
– surface properties need to
be known:
D 1% alb ~ D 0.1 AOD
global … data / applications
• seasonal multi-annual averages for
– ‘amount’
AOD
– ‘size’
Angstrom / fine-mode fraction
(aerosol optical depth)
– ‘absorption’ absorption-AOD
(= AOD * (1-ssa))
– ‘water-vapor’
• combining with modeling  climatology
which is superior to modeling
• evaluation (of assimilations)
sun-photo & modeling = climatology
annual maps of an aerosol climatology
evaluating assimilations
2003 AOD
2004 AOD
AOD diff. to AERONET
2003 Angstr 2004 Angstr
Angstr diff. to AERONET
2004 AOD … is this good ?
AOD diff. to AERONET
 underestimate
overestimate 
scoring AOD performance
score - 0.56
(error = 0.44)
BIAS-sign
positive negative
temp correlation
error
strength
spatial correlat.
error
bias strength
error
increasing error 
complementary nature
even though lidar and sun-/sky-photometer have
different viewing geometries …
• lidar needs (or can use)
– the complementary constraint on column integrated
extinction (=AOD) and other column aero properties
– the more continuous temporal day-time coverage
• sun-/sky photometry are extended by lidar
– via vertical stratification of properties
– via night-time coverage
extra slides
AERONET