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Global free tropospheric NO2 AbundancesDerived using a Cloud Slicing Technique
from Aura OMI
S. Choi, J. Joiner, Y. Choi, B. N. Duncan,A. Vasilkov, N. Krotkov and E. J. Bucsela
Aura Science TeamMeeting2014. 9. 16.
https://ntrs.nasa.gov/search.jsp?R=20150000361 2020-06-12T20:59:06+00:00Z
Free Tropospheric NO2
Atmospheric NO2
– Produced by combustion, lightning, and in soil
Indirect radiative impacts in troposphere– Ozone has largest warming effect in upper troposphere– Impacts methane concentrations
A few types of free tropospheric NO2 measurementsavailable– Aircraft in situ measurements, MAX DOAS, NO2 sondes,etc.
12/3/2014 2Aura Science Team Meeting 2014
Cloud Slicing Technique
Utilize above cloud NO2 column (where CRF > 0.9)– Good quality column measurements as clouds providebright surface
– Usually neglected in the view of surface pollution
Data obtained– Free tropospheric NO2 volume mixing ratio (VMR)Independent of prescribed stratospheric columnestimate
12/3/2014 3Aura Science Team Meeting 2014
Cloud Slicing Technique
Ground
Top of Atmosphere (TOA)
Clou
dscen
epressure
(hPa)
NO2 VCD above the clouds
Measurement at Cloudy Scenes Observed Column vs Pressure
Ground
TOA
~1013
0
12/3/2014 4Aura Science Team Meeting 2014
Cloud Slicing Technique
Ground
Top of Atmosphere (TOA)
Clou
dscen
epressure
(hPa)
NO2 VCD above the clouds
Measurement at Cloudy Scenes Observed Column vs Pressure
Ground
TOA
~1013
0
12/3/2014 5Aura Science Team Meeting 2014
Cloud scenepressure
Cloud Slicing Technique
Ground
Top of Atmosphere (TOA)
Clou
dscen
epressure
(hPa)
NO2 VCD above the clouds
Measurement at Cloudy Scenes Observed Column vs Pressure
Ground
TOA
~1013
0
12/3/2014 6Aura Science Team Meeting 2014
Cloud scenepressure
Cloud Slicing Technique
Ground
Top of Atmosphere (TOA)
Clou
dscen
epressure
(hPa)
NO2 VCD above the clouds
Cloud scenepressure
NO2 VMR
= *kB*g/RairdVCDdP
P
VCD
Measurement at Cloudy Scenes Observed Column vs Pressure
Ground
TOA
~1013
0
12/3/2014 7Aura Science Team Meeting 2014
Cloud Slicing Technique
The slope between NO2 VCD and cloud pressure isproportional to NO2 volume mixing ratio (VMR)
Ground
Top of Atmosphere (TOA)
Clou
dscen
epressure
(hPa)
NO2 VCD above the clouds
Cloud scenepressure
NO2 VMR
= *kB*g/RairdVCDdP
P
VCD
Measurement at Cloudy Scenes Observed Column vs Pressure
Ground
TOA
~1013
0
12/3/2014 8Aura Science Team Meeting 2014
Cloud Slicing Technique
Using near Lambertian cloudy AMF instead ofgeometric AMF
Assumptions– Uniform NO2 VMR in the sampling pressure ranges– No stratospheric variation in the samplingspatial/temporal ranges (6ox 8o, calculated per orbit)
Limitations– Represent cloudy conditions only– Magnitudes only as accurate as above cloud NO2 VCD
• Uncertainties in SCD, cloudy AMF
12/3/2014 9Aura Science Team Meeting 2014
Comparison with INTEX B Data
INTEX B VMR standard error < 5 pptvSimilar magnitude but very weak correlationReasonable agreement despite the intrinsic limits:– Poor collocation, small scale features, clear/cloudy conditions
12/3/2014 10Aura Science Team Meeting 2014
Global Seasonal Climatology
Global seasonal free tropospheric NO2 climatology– Take advantage of high spatial/temporal coverage ofsatellite measurements
– Concentrate on spatial and seasonal patterns
Large volume of data required for reasonable results– 3 year OMI data accumulated (2005 2007)– Coarse resolution (6o latitude x 8o longitude)
Distinct patterns in the free tropospheric VMR– Independent source of data to study free troposphere
12/3/2014 11Aura Science Team Meeting 2014
Global Seasonal Climatology
12/3/2014 12Aura Science Team Meeting 2014 OMNO2B
Global Seasonal Climatology
12/3/2014 13Aura Science Team Meeting 2014 OMNO2B
Different spatial patternsfrom tropospheric column
Global Seasonal Climatology
Appears to be anthropogenic contributions(uplifted pollution & outflow)
12/3/2014 14Aura Science Team Meeting 2014 OMNO2B
Global Seasonal Climatology
Appears to be lightning contributions(dominates during summer months)
12/3/2014 15Aura Science Team Meeting 2014 OMNO2B
Global Seasonal Climatology
12/3/2014 16Aura Science Team Meeting 2014 OMNO2B
Global Seasonal Climatology
Appears to be anthropogenic contributions(uplifted pollution & outflow)
12/3/2014 17Aura Science Team Meeting 2014 OMNO2B
Global Seasonal Climatology
Appears to be lightning contributions(dominates during summer months)
12/3/2014 18Aura Science Team Meeting 2014 OMNO2B
Profile Analysis
Coarse profile analysis (~100 hPa resolution)
Requires even more data with significant cloudpressure variability
Example cases– Tropical oceans of NH and SH for lightning NO2
12/3/2014 19Aura Science Team Meeting 2014
Profile Analysis
12/3/2014 20Aura Science Team Meeting 2014
Profile Analysis
12/3/2014 21Aura Science Team Meeting 2014
Profile Analysis
High NO2 above 500 hPain summer
12/3/2014 22Aura Science Team Meeting 2014
Conclusions
Free tropospheric NO2 VMR derived using cloud slicing
Comparison with INTEX B measurements showsreasonable agreement
Global seasonal climatology shows anthropogenic andnatural (lightning) features of free tropospheric NO2,independent of the tropospheric column
Profile analysis shows lightning NO2 in the uppertroposphere
Expect collaborations with various free troposphericNO2 measurements and models
12/3/2014 23Aura Science Team Meeting 2014
Thank you!
S. Choi et al.: Global free tropospheric NO2 AbundancesDerived using a Cloud Slicing Technique from Aura OMI,Atmos. Chem. Phys. Discuss., 2014
Backup slides
12/3/2014 25Aura Science Team Meeting 2014
Detail/Data Screening Criteria
Use slant column density (OMNO2A) and geometricAMF
Cloud radiance fraction > 0.9Aerosol index < 1.0No snow/ice surfaceSolar zenith angle < 80 degreeGradient of NO2 VMR < 0.33 pptv / hpa (profiles fromGMI model or INTEX B measurements)
12/3/2014 26Aura Science Team Meeting 2014
Example of Calculated NO2 Climatology
12/3/2014 27Aura Science Team Meeting 2014
Free Trop. NO2 VMR (OMI vs GMI)OMI GMI
12/3/2014 28Aura Science Team Meeting 2014
Tropospheric Column NO2 (OMI vs GMI)OMI GMI
12/3/2014 29Aura Science Team Meeting 2014
