Surface UV from TOMS/OMI measurements N. Krotkov 1, J. Herman 2, P.K. Bhartia 2, A. Tanskanen 3, A....
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Transcript of Surface UV from TOMS/OMI measurements N. Krotkov 1, J. Herman 2, P.K. Bhartia 2, A. Tanskanen 3, A....
Surface UV from TOMS/OMI Surface UV from TOMS/OMI measurementsmeasurements
N. Krotkov1, J. Herman2, P.K. Bhartia2 , A. Tanskanen3 , A. Arola4
1. Goddard Earth Sciences and Technology (GEST) Center, UMBC, Baltimore, MD
2. Laboratory for Atmospheres, NASA GSFC, Greenbelt, MD
3. Finnish Meteorological Institute , Helsinki, Finland
4. Finnish Meteorological Institute , Kuopio, Finland
OMI Science questions
• Is the ozone layer recovering ?
• What are sources and distributions of aerosols and trace gases that affect global air quality?
• What are the roles of tropospheric ozone and aerosols in climate change?
• What are the causes of surface UV-B change ?
Levelt et al “ Science objectives of Ozone Monitoring Instrument “ in IEEE- TGRS AURA special issue
UV products: noon irradiance + Daily CIE dose (305nm, 310nm, 324nm, 380nm, CIE - UV index)
305nm 324nm
380nmErythemal – UV index
Current Applications of TOMS/OMI UV data
1. Sun burn and skin cancer PHS, NIH, WHO2. Eye cataracts PHS, NIH, WHO3. Plant damage - Crop yields USDA4. Food chain - Land – Oceans USDA, NOAA5. Effect on insect population NIH, PHS, WHO
TOMS/OMI UV algorithm
OMI Ozone
Clouds
Aerosols
Fc ~ FO3(1 – R)
ASeFF OG 210/
3
ROeFF oO 3
3
Absorbing aerosols are still a major problem
Clouds and non-absorbing aerosols are well corrected
Sun: Fo ( ~ 3% uncertainty )
Cloud correction algorithm (CT)
TOMSISCCP
Ground CT measurement
Sat
elli
te C
T e
stim
ate
daily
10 day
monthly
(1:1)UV- Williams et al GRL 2004 (1:1)
PAR - Dye et al GRL 1995
Clouds over snow correction
• Surface albedo is a crucial parameter for estimation of the surface UV in regions with temporary snow or ice.
• OMI UV algorithm applies an albedo climatology derived from the N7/TOMS reflectivity data using the moving time window method.
• The accuracy of the surface UV estimates for high latitudes has improved.However, the estimates for albedo transient periods are still uncertain.
http://promote.fmi.fi/MTW_www/MTW.html
The TOMS-Brewer difference for erythemally weighted UV irradiance and for UV irradiance at 305, 310, and 324 nm.
Summer noon values for mostly clear sky conditions (TOMS reflectivity <0.2)
-10
0
10
20
30
She
nand
oah
The
odor
eS
atur
naB
ig B
end
Can
yonl
ands
Alb
uque
rque
Mon
treal
G. S
mok
ey M
tG
laci
er
Oly
mpi
cA
cadi
a
Den
ali
Atla
nta
Goo
se B
ay
Chi
cago
Chu
rchi
ll
Gai
ther
sbur
gH
alifa
xE
dmon
ton
Win
nipe
gS
aska
toon
Reg
ina
Toro
nto
Roc
ky M
t
Bou
lder
Res
.Tri.
Par
k
Virg
in Is
land
sS
equo
iaR
iver
side
Eve
rgla
des
TOM
S-B
rew
er d
iffer
ence
(%
)
UV 324 nm
UV 310 nm
UV 305 nm
CIE
-10
0
10
20
30
40
Riverside Canyonlands Res.Tri.Park Shenandoah Gaithersburg Saturna Toronto
TO
MS
-Bre
we
r d
iffe
ren
ce
(%
)
1989
1990
1991
1992
1996
1997
1998
1999
2000
2001
The TOMS-Brewer difference for erythemally weighted summer noon UV irradiance for mostly clear sky conditions (TOMS reflectivity <0.2)
Urban locations
TOMS AI examples of high-density smoke aerosols that affect various coastal regions in the US, India, and Southeast Asia. Lesser amounts of smoke, dust, and carbonaceous aerosols frequently cause overestimations of UV irradiance if ignored.
US
India
Southeast Asia
Long-range ABSORBING aerosol transport in free troposphere is uniquely tracked by OMI/TOMS Aerosol Index (AI)
AI cannot detect boundary layer UV absorbing aerosols resulting in overestimates of UV irradiance that are frequently 10% and sometimes 20%.
UV reduction due to absorbing aerosols in free troposphere (dust, smoke) is corrected using positive AI >0.5 data
Industrial aerosols close to the ground are not seen in AI data (AI <0), so they are treated as thin clouds, which leads to positive UV bias
Since 2002, the NASA TOMS, AERONET and USDA UVB programs have shared equipment, personnel and analysis tools to quantify aerosol UV-VIS absorption using a combination of ground based radiation measurements.
Ground AEROSOL absorption measurements
Brewer spectrometer ozone, SO2, NO2 [Cede and Herman]
UV Multifilter Rotating Shadowband Radiometer
AERONET CIMEL sun-sky radiometers
Time series of aerosol absorption optical thickness tabs at 368nm, derived from 17 months UV-MFRSR operation at NASA GSFC site in Maryland, US. The data are for cloud-free and snow-free conditions and tabs(440)>0.1. Individual tabs(368) values were averaged over 1-hour period of time within ±60min of the AERONET inversion.
The ratio between satellite estimated (by TOMS UV algorithm7-10) and measured (by UVMFRSR) total (direct plus diffuse) surface UV irradiance at 325nm versus aerosol absorption optical thickness at 325nm inferred from combined UV-MFRSR and AERONET measurements at NASA/GSFC site. The line shows theoretical relationship derived from radiative transfer modeling10.
1Krotkov et al. Opt. Engineering 2005
TOMS UV Correction for Absorbing Aerosols in Greenbelt, USA 1
TO
MS
/Gro
und
UV
AB
S a
t 325
nm
ABS at 325nm
The ratio of TOMS to Brewer irradiance at 324nm against aerosol absorption optical thickness in Thessaloniki, Greece
1Arola et al. accepted JGR 2005
TOMS UV Correction for Absorbing Aerosols in 2 urban sites 1
The ratio of TOMS to Brewer irradiance at 324nm against aerosol absorption optical thickness at Ispra, Italy
SZA=20-30
SZA=40-50
SZA=60-70
Future Applications of OMI data
1. Global mapping of PAR (400-700nm) 2. Actinic flux profile and J-rates for photochemistry models3. UV irradiance on tilted surfaces4. Global mapping of underwater UV-PAR irradiance5. Global primary production estimates6. Global carbon cycle models
Erythemal Irradiance Trend 1980 to 2002
O3R360
305 nm Irradiance Trend 1980 to 2002
R360O3