BSRN 2002 Regina 28.-31. May Aerosol Optical Depth with PFR instruments in GAW Trial Network...
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Transcript of BSRN 2002 Regina 28.-31. May Aerosol Optical Depth with PFR instruments in GAW Trial Network...
BSRN 2002 Regina 28.-31. MayAerosol Optical Depth
with PFR instruments in
GAW Trial NetworkChristoph Wehrli
Physikalisch-Meteorologisches ObservatoriumDorfstrasse 33, 7260 Davos Dorf, Switzerland
•Goals of trial network•State of the network•Calibration scheme•Data processing approach•Results from selected stations•Comparison with other data
BSRN 2002 Regina 28.-31. May
GAW/WORCC trial network
Subsequent to the AOD fiasco in BAPMon, WORCC was proposed and established in 1996 at Davos, sponsored by Switzerland.
Goals• Implement AOD measurements at 12 global
observatories with new instrumentation, sound calibration, data quality control and protocols.
• Test and verify new instruments and methods under operational network conditions.
• Train station operators in AOD measurements.
WORCC is assisted by a international group of experts and works in cooperation with GAW QA/SAC SAG/Aerosols assumes these roles.
WMO initiated contacts between potential stations and WORCC for placement of instruments donated by MeteoSwiss. Host stations are to provide tracking facility and limited manpower.
BSRN 2002 Regina 28.-31. May
State of trial network
1. Hohenpeissenberg, Germany, Jun.19992. Mace Head, Ireland, Jul. 19993. Boulder, USA, Aug. – Oct. 1999
Mauna Loa, Ha, USA, Nov. 1999 (Aeronet)4. Bratt‘s Lake, Canada, Apr.2001 (BSRN, Aeronet)5. Izaña, Spain, Jun. 20016. Ryori, Japan, Jun. 20017. Alice Springs, Australia, Jul. 2001 (BSRN)8. Ny Ålesund, Norway, Apr. 2002 (BSRN)9. Irkutsk, Russia
10. Bukit Koto Tobang, Indonesia
11. Brazil ? (Acre | Manaos)
12. Africa ? (Lamto)
Jungfraujoch, Switzerland, Mar. since 1999 (CHARM)Davos, Switzerland, Nov. 1998 – Nov. 2000
BSRN 2002 Regina 28.-31. May
Precision Filter Radiometer
PFR specifications• Automated, solar spectral radiometer• 4 WMO channels at 862, 500, 412, 368nm
using IAD interference filters• Field of View: ±2.5° , slope angle 0.7°• Dimensions: Ø90 x L300mm, Mass 3 kg• Sensor at 20±0.1°C in range –25 ÷ 35°C
internal shutter; N2 purged, airtight housing• High cadence (2 or 1 min.) measurements• Data logger with 30 day storage capacity, built-
in pressure and pointing sensors
PFR N21 at Ryori, Japan.
BSRN 2002 Regina 28.-31. May
WORCC Calibration Hierarchy
• Standard instruments are calibrated at high altitude stations (Jungfraujoch, Mauna Loa) by atmospheric extrapolation methods.
• Working standards are calibrated by com-parison with WORCC standards at Davos or Jungfraujoch.
• Stability of standard instruments is moni-tored by spectral comparison with a metro-logically traceable absolute detector.
• Station instruments are linked to WORCC reference by travelling standards or ex-change of sensors.
• Performance is tested through intercom-parison of field instruments with other co-located networks.
BSRN 2002 Regina 28.-31. May
Stratospheric Balloon Flight
• Verification of Langley method by in situ measurements from SIMBA balloon flight in Oct.98
• PFR N01 measurements at 40 km height. Atmospheric transmission corrected by MODTRAN calculation
• PFR N02 mean of 19 refined Langley calibrations, obtained in Dec. 98 and Jan.99 at Jungfraujoch (3580m)
• Comparison between N01 and N02 found agreement to < 1%
• Langley calibration V0 are con-sistently higher than balloon.
BSRN 2002 Regina 28.-31. May
High Altitude Calibration
Sphinx Research Station at Jungfraujoch
Altitude 3580mLatitude 46°32’55” NLongitude 7°59’11” EFully automated domeOperation of 4 PFRs
Jan00 Jan013.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4.0
4.1
4.2Langley history N24
Date
V0 [
V]
Wavelength : 368 412 500 862 [nm]Langley Vo : 4.009 3.651 3.802 3.505 [V]Stdev Vo : 0.004 0.007 0.007 0.009 [V]Slope/year : -0.00 -0.39 -0.88 -0.52 [%]±Slope : 0.18 0.14 0.14 0.09 [%]
BSRN 2002 Regina 28.-31. May
Radiometric Calibration
Spectral irradiance scale based on cryogenic radiometer of PTB (Berlin) transferred via calibrated trap detector (uncertainty <5•10-4)
400 500 600 700 800 90010
-2
100
102
104
Wavelength / nm
Re
sp
on
siv
ity
/ (
V/W
)
PFR radiometric response
Trap Calibration History PFR-N01
0.98
0.99
1.00
1.01
1.02
Jul-98 Jan-99 Aug-99 Feb-00 Sep-00 Mrz-01 Okt-01 Mai-02
Rat
io to
Mea
n(ca
l 3..8
)
Stdeviation <0.33% (0.5%)Annual drift <(0.6±3)•10-3
Bandpass integral deter-mined every 6 months.
Instrument N01 is assumed to be radiometrically stable to <±0.5%
Solar calibration V0 could be determined if an accurate extraterrestrial spectrum was available.
BSRN 2002 Regina 28.-31. May
Operations & data processing
• At GAW stations– Periodic download from logger to local PC– Periodic maintenance (cleaning, pointing, clock)– External provision of ancillary data (O3, meteo)– Production of Level2 data, quality control– Upload to WORCC by mail or ftp
• At WORCC– Monthly archive updates– Monthly overview summaries and tests– Production of AOD files
• At WDCA undefined yet
BSRN 2002 Regina 28.-31. May
Data Products, Quality control and
ArchivesProducts
• Level1: bulk raw measurements, 1m cadence.
• Level2: daily files in standardized format.• Level3: daily files of derived AOD, 2
releases.
Quality control• Quality flags added to Level2 data on-site
with warning/error messages during processing.
• Preliminary Level3.1 data generated assuming constant calibration.
• Final Level3.2 after assessment of calibration by travelling standard and evtl. re-processing.
Archives and data volume• Level1: GAW-GO, WORCC
~3.5MB/month• Level2: GAW-GO, WORCC <128kB/day• Level3: WORCC WDCA <20kB/day
GAW-GO WDCA (final network)
BSRN 2002 Regina 28.-31. May
Level2 Data format• Self-contained daily ASCII files
• Header with keyword = parameter set
• Generated by standardized software
%STATION =MaunaLoa %LATITUDE = 19.5330 %North%LONGITUDE =155.5780 %West%ALTITUDE = 3397.0 %above sea level%ZONE = 0 %UTC=logger time - Zone%STATIDENT = 11%DATE =2000 8 10 %date containing solar noon%AIRPRESS = 666.7 %average Sun above horizon%AIRTEMP = 23.8 %instrument body%OZONE = 277.3 %climatological or actual DU%INSTRUMENT=PFR-N27 %INSTIDENT = 27%NCHANNELS = 4%NREADINGS =1439 %actual number of records%WAVELENGTH= 862.4 501.2 412.0 367.6 %nominal or measured%CALDATE =1999 12 27 %recalibrated at MLO%CALIBRAT = 3.4640 3.8140 3.8070 4.1030 %Extraterrestrial signal%SLOPE = +0.072 +0.050 -0.151 +0.117 %mV per day since CALDATE%O3ABS = 0.0024 0.0340 0.0002 0.0000 %Gueymard, filter averaged%RAYLSCATT = 0.0157 0.1420 0.3186 0.5128 %Bodhain at WAVELENGTH%SUNEARTH = 1.013466 %%DECLINAT = 15.11215%EQOFTIME = 6.882%NOON = 22.487%LOGFILE =H:\WORCC\PFR\MaunaLoa\mlo_n27.LOG%VERSION = 2.80%COMMENT =for column description, see PFRLEV2.HLP%END % UTC SunElv Barom 862 500 412 368 Tsens Tbody PntgV PntgH Flg 17.0000 12.513 666.2 3.2552 2.2998 1.3813 0.8234 20.49 16.11 -5.71 -7.62 0 17.0167 12.744 666.2 3.2598 2.3206 1.4054 0.8460 20.49 16.16 -5.66 -7.59 0 17.0333 12.974 666.1 3.2614 2.3376 1.4279 0.8682 20.49 16.24 -5.73 -7.57 0 17.0500 13.205 666.0 3.2687 2.3592 1.4522 0.8913 20.49 16.29 -5.73 -7.59 0 17.0667 13.435 666.1 3.2739 2.3792 1.4753 0.9146 20.49 16.37 -5.72 -7.55 0 17.0833 13.666 666.2 3.2768 2.3970 1.4984 0.9365 20.49 16.42 -5.77 -7.54 0 17.1000 13.897 666.2 3.2794 2.4140 1.5202 0.9578 20.49 16.50 -5.79 -7.54 0 17.1167 14.128 666.3 3.2809 2.4301 1.5411 0.9794 20.49 16.55 -5.84 -7.54 0 17.1333 14.358 666.2 3.2832 2.4457 1.5626 1.0002 20.49 16.62 -5.88 -7.51 0 17.1500 14.589 666.3 3.2859 2.4614 1.5819 1.0208 20.49 16.68 -5.87 -7.49 0 17.1667 14.820 666.3 3.2911 2.4806 1.6041 1.0432 20.49 16.75 -5.92 -7.46 0 17.1833 15.051 666.3 3.2933 2.4956 1.6246 1.0639 20.49 16.81 -5.93 -7.47 0 17.2000 15.282 666.2 3.2960 2.5105 1.6429 1.0842 20.49 16.86 -5.99 -7.47 0 17.2167 15.514 666.2 3.2971 2.5246 1.6628 1.1044 20.49 16.94 -6.02 -7.40 0 17.2333 15.745 666.3 3.3008 2.5399 1.6827 1.1256 20.49 17.01 -5.98 -7.42 0 17.2500 15.976 666.3 3.3044 2.5541 1.7018 1.1454 20.49 17.07 -6.06 -7.38 0 17.2667 16.207 666.1 3.3050 2.5667 1.7193 1.1645 20.49 17.15 -6.07 -7.38 0 17.2833 16.439 666.3 3.3062 2.5807 1.7371 1.1842 20.49 17.20 -6.05 -7.34 0 17.3000 16.670 666.3 3.3105 2.5960 1.7562 1.2041 20.49 17.27 -6.11 -7.36 0
BSRN 2002 Regina 28.-31. May
Cloud Filtering
Cloud flags for individual high cadence samples1. Harrison & Michalsky algorithm, modified for air
masses <22. Aeronet algorithm applied as moving filter on
continuous samples3. Optically thick (OD>3) clouds
6 8 10 12 14 160.0
0.5
1.0
1.5
2.0
2.5
3.0
Time [GMT]
Sig
na
l [V
]
Eithe r H a rris onSm irnovC le a rs ky
BSRN 2002 Regina 28.-31. May
Instrument health control
-30 -20 -10 0 10 20 30-30
-20
-10
0
10
20
30Pointing
arcminutes -30 -20 -10 0 10 20-15
-10
-5
0
5
10
15
T(body-head)
Pe
ltie
r p
ow
er
0 10 20 30
870
880
890
900
910
920
930
940
Day
atm
. p
res
su
re [
hP
a]
HK-Overview HPB N06 for APR02
Date: 23-May-2002 ChWFile: monthlyHK2.m
Mean pointing : 12.2± 8.5 [arcmin]
Peltier cntrl :-0.505*dT -0.37 [W] Mean pressure : 902.2± 7.9 [hPa] Temperature :Thd= 20.5±0.0; Tbd= 10.2± 3.8; Tlg= 34.0± 0.6; [°C]
0 10 20 30
-20
-10
0
10
20
30
40
Day
Te
mp
era
ture
s [
°C]
BSRN 2002 Regina 28.-31. May
Bratt’s Lake
Apr01 Jul01 Oct01 Jan02 Apr02 Jul020.00
0.10
0.20
0.30
Date
AO
D 5
00
nm
0 0.05 0.1 0.15 0.2 0.250
10
20
30
40
50
60
70
AOD 500nm
Nu
mb
er
of
ca
se
s
AOD summary REG-N23
Date: 24-May-2002 ChWfile: AODstat2.m
272 selected clear days
Avg( ) =0.089±0.055; Median( )=0.072 Avg( ) =1.24 ±0.368; Median( )= 1.31
Gmean( )=0.075*1.8± 1
Filter: >0 & <0.3 & 0.00< <0.29
0 0.1 0.2 0.30
0.5
1
1.5
2
2.5
3
AOD 500nm
Ån
gs
trö
m
BSRN 2002 Regina 28.-31. May
Hohenpeissenberg
Jan99 Jan00 Jan01 Jan020.00
0.05
0.10
0.15
0.20
0.25
0.30
Date
AO
D 5
00
nm
0 0.1 0.2 0.30
10
20
30
40
50
60
AOD 500nm
Nu
mb
er
of
ca
se
s
AOD summary HPB-N06
Date: 24-May-2002 ChWfile: AODstat2.m
286 selected clear days
Avg( ) =0.103±0.062; Median( )=0.092 Avg( ) =1.50 ±0.337; Median( )= 1.57
Gmean( )=0.084*2.0± 1
Filter: >0 & <0.3 & 0.00< <0.31
0 0.1 0.2 0.30
0.5
1
1.5
2
2.5
3
AOD 500nm
Ån
gs
trö
m
BSRN 2002 Regina 28.-31. May
Sahara Dust event
6 8 10 12 14 160.00
0.20
0.40
0.60
0.80
AO
D &
Ån
gs
trö
m
VBGR: 367.6 412.1 501.0 863.1 nm
HOHENPEISSENBERG PFR-N06 06-Jul-2001
Date: 24-May-2002 ChWFile: AerosolOD2.m; opt=2
Wl: 368 412 501 863 nm
V0: 4.218 3.825 3.837 3.370 V
<AOD>: 0.498 0.460 0.399 0.284 < >= 0.970, < >=0.2600press: 902.9 hPa; Ozone: 327.9 DU
6 8 10 12 14 16
0.5
1
1.5
2
2.5
Ån
gs
trö
m
Time [GMT]
BSRN 2002 Regina 28.-31. May
Mace Head
Jan01 Apr01 Jul01 Oct01 Jan02 Apr020.00
0.05
0.10
0.15
0.20
0.25
0.30
Date
AO
D 5
00
nm
0 0.1 0.2 0.30
10
20
30
40
50
60
AOD 500nm
Nu
mb
er
of
ca
se
s
AOD summary MHD-N02
Date: 24-May-2002 ChWfile: AODstat2.m
123 selected clear days
Avg( ) =0.123±0.060; Median( )=0.110 Avg( ) =0.63 ±0.441; Median( )= 0.57
Gmean( )=0.110*1.6± 1
Filter: >0 & <0.3 & 0.00< <0.31
0 0.1 0.2 0.30
0.5
1
1.5
2
2.5
3
AOD 500nm
Ån
gs
trö
m
BSRN 2002 Regina 28.-31. May
MLO Comparison 2000
Methodology
• AERONET/CIMEL and WORCC/PFR data compared at individual samples level
• Aeronet Level2 data†as published on web• WORCC/PFR with interpolated calibration
• CIMEL channels are interpolated to WMO wavelengths of PFR by Ångström’s law
• PFR one minute samples are interpolated in time to CIMEL observation scheme
• Data gap in PFR from late May to early July
† with kind permission of Dr. Brent Holben, Aeronet PI, NASA/GSFC
BSRN 2002 Regina 28.-31. MayMLO Comparison 2000
Aerosol Optical Depths
0 0.05 0.1 0.150
0.05
0.1
CIM
EL
0 0.02 0.04 0.06 0.08 0.10
0.02
0.04
0.06
0.08
0.1
0 0.02 0.04 0.06 0.08 0.10
0.02
0.04
0.06
0.08
0.1
CIM
EL
PFR
Date: 23-May-2002 ChWuse of Aeronet data kindly permitted by Brent Holben, NASA/GSFC
Wavelength : 367.6 412.0 501.2 862.4
Mean slope : 1.0941 1.1056 1.0678 1.0531Mean bias : -0.0002 0.0001 -0.0005 0.0002RMS diff. : 0.0055 0.0043 0.0030 0.0026N = 4705
0 0.02 0.04 0.06 0.08 0.10
0.02
0.04
0.06
0.08
0.1
PFR
BSRN 2002 Regina 28.-31. May
MLO Comparison 2000 Ångström α
Q1-00 Q2-00 Q3-00 Q4-00 Q1-010.0
1.0
2.0
3.0
4.0
5.0
Ån
gs
trö
m
green: Aeronet; black: GAWnet
0 1 2 3 40
0.5
1
1.5
2
2.5
3
3.5
4Ångström
PFR
Cim
el
Date: 23-May-2002 ChWuse of Aeronet data kindly permitted by Brent Holben, NASA/GSFC
Alpha PFR :1.63±0.26
Alpha Cimel :1.69±0.46; Aeronet 1.83±0.30(2000)Aeronet :1.66±0.24; (climatological)
0 0.05 0.1 0.15 0.20
0.5
1
1.5
2
2.5
3
3.5
4
AOD500
Ån
gs
trö
m