# Presentation: 366550

## OMI Validation with theGround-Based WSU MFDOAS Spectrometer

- George H Mount and Elena Spinei, Washington State University
- PK Bhartia, NASA GSFC
- NO2:  Jay Herman (NASA GSFC), Stanley Sander, Shuhui Wang, Thomas 	Pongetti (NASA JPL)
- HCHO:  Thomas Kurosu and  Kelly Chance (Harvard Smithsonian Center for 	Astrophysics), Michael Newchurch (University of Alabama)
- SO2:  Simon Carn (Michigan Technological University), Nickolay Krotkov 	(GEST/UMBC), Arlin Krueger (JCET/UMBC)
- AURA Science Team Meeting
- Columbia, Maryland
- 27 October 2008

## WSU MFDOAS Spectrometer

- observes direct sun (DS) or scattered skylight (MAXDOAS)
- spectral coverage:  281 - 498 nm
- CCD - 13.5 μm pixel size
- spectral resolution:  0.83 nm
- spectral sampling on FWHM:  7.8 pixels
- DS uses an integrating sphere to eliminate problems with illumination
- FOV:  ~ 1°
- integration time:  sub-second
- NO2 spectral region:  recorded without a filter
- UV spectral region:  UV filter in place
- typical observing cycles:
- direct sun measurements continuously
- MAXDOAS - scattered sky in azimuth/elevation with a DS every azimuth rotation
- depending on science, can change spectral regions quickly and put those into a MAXDOAS cycle
- today will report *only on DS measurements* = simple AMF determination for conversion to vertical columns for comparison with OMI

## Field Campaigns Completed

- Pacific Northwest National Laboratory, Richland, WA - April 2006 in prototype mode
-   NO2
- Goddard Space Flight Center - May 2007, two weeks
-   NO2 in collaboration with GSFC Pandora group
- Jet Propulsion Laboratory - Table Mountain Facility - July 2007, two weeks
- NO2 in collaboration with JPL FTS group collaboration and GSFC Pandora group
- WSU, Pullman, WA - fall/winter 2007
- NO2
- ~ 40 days of high quality data
- PNNL, Richland, WA - spring 2008
- NO2
- ~ 80 days of high quality data
- WSU, Pullman, WA - July 2008
- SO2 from Okmok volcano
- University of Alabama, Huntsville, AL - August 2008, two weeks
- HCHO and NO2

## Criteria for OMI Data

- < 30% cloud cover
- for NO2, used the standard product with tropospheric correction  and required OMI pixel to be within 0.2°
- for SO2, the OMI SO2 group provided a detailed analysis of the OMI data
- for HCHO, the OMI HCHO group provided their standard data product and we used the closest pixel

## Slide 5

## Slide 6

## Okmok Volcanic Plume

- eruption in Aleutian islands, 12 July 2008
- drifted south to Hawaii and then over state of Washington
- plume height 11 - 13 km

## Okmok Volcanic Plume over Washington, 19 July 2008

## WSU MFDOAS SO2

- WSU MFDOAS SO2

- absolute error:  ~ 0.2 DU
- 4 days of data obtained
- before the cloud dissipated

## Slide 10

## HCHO

- measured at U Alabama in Huntsville, August 2008 (Mike Newchurch)
- had a number of good days during two week period
- concentrated on HCHO, but have intermittent NO2 data
- spectral region for reduction:  323 - 341 nm
- required removal of O3, NO2
- errors are large (_+_ 30%) due to cross correlation coefficient of molecular cross sections and lack of uniqueness of the corresponding retrieval
- errors are large in the OMI data:
- s/n of data
- cross correlation coefficient of cross sections
- interaction with BrO spectrum
- pixel size
- pixel co-location
- aerosol loading and “seeing” the PBL where HCHO resides

## OMI HCHO 8 - 20 August 2008 average

## Slide 13

## Huntsville HCHO August 2008

## Slide 15

## Conclusions

- OMI slightly *overpredicts* NO2 relative to the ground measurements
- OMI predicts SO2 columns within the errors  of both measurements
- OMI HCHO and ground based HCHO do not agree but overall time 		variation is similar
- WSU MFDOAS:
- reduction of scattered sky MAXDOAS data is underway for all these campaigns
- spatial inhomogeneities will be determined
- azimuthally dependent vertical columns will be determined
- future field campaigns
- Boise, Idaho  -  December 2008
- Houston, Texas  -  April/May 2009
- Cabauw, The Netherlands  -  June 2009 (maybe)