TEMIS user workshop, Frascati, 8-9 October 2007

Report on the AT2 NO2 workshop

• NO2 workshop held on 10-12 September 2007 as part of ACCENT (EU) activities, attended by many scientists working on NO2 and a few data users.

• Use of NO2 data :– Kenneth Pickering (NASA): OMI Tropospheric NO2 from Lightning in

Observed Convective Events.

– Louisa Kramer (Univ. Leicester): Monitoring air quality in an urban area using remote sensing techniques and in situ measurements.

– Ronald Cohen (UC Berkeley):Urban and Agricultural NOx Emissions.

– Wayne Robinson (NASA): The generation of a temporally consistent NO2 data record for ocean color work.

TEMIS user workshop, Frascati, 8-9 October 2007

Ken Pickering – NASA Goddard

Cloud Cover

Level 2 OMI Tropospheric NO2

This analysis uses OMI tropospheric NO2 to obtain estimates of LNOx production in specific convective events over the Central USA.

Retrieval with AMF for anvil outflow andbackground subtraction

1.64 +/- 0.617 x 106 moles NO2

TEMIS user workshop, Frascati, 8-9 October 2007

In situ

Ground based remote sensing

Satellites

Louisa Kramer (University of Leicester)

TEMIS user workshop, Frascati, 8-9 October 2007

Ron Cohen (UC Berkeley)

• NO/NO2 photostationary state is likely a more accurate way to calculate surface NO2 from the monitoring network than using a model of NOz .

• OH and NO2 are strongly coupled on spatial scales of a single OMI/SCIA/GOME-II pixel.

• Day of week can teach us a lot about sources and the quality of retrievals—since some factors are not strongly correlated with day of week; AMFs, stratosphere, etc.

• Seasonal variations provide strong hints about soil emissions.

TEMIS user workshop, Frascati, 8-9 October 2007

Wayne Robinson (NASA-GSFC):NO2 Effects on Ocean retrievals

Stratospheric NO2

Tropospheric NO2

NO2 absorption

412

443

488

530550

670

Chlorophyll

400 500 600 700Wavelength (nm)

-5

0

5

10

15%

Ch

ang

e (f

or

5 X

10

15

mo

lec

ule

NO

2 c

ha

ng

e)

Sensitivity of Water-leaving radiance

and Chlorophyll retrievals to NO2

Water-leaving radiance

Recent work has shown importance of NO2 in ocean color retrievals (Ahmad et. al., 2007, Robinson et. al., 2007)

TEMIS user workshop, Frascati, 8-9 October 2007

Wayne Robinson (NASA-GSFC): Temporal trend results: before correction

TEMIS user workshop, Frascati, 8-9 October 2007

Wayne Robinson (NASA-GSFC): Temporal trend results: after correction

TEMIS user workshop, Frascati, 8-9 October 2007

Summary

• Modifications to the NO2 data are possible to create more consistent NO2 record for ocean work

– Latitudinal modification

– Non-linear fit

• Some differences remain and seasonal changes not examined

TEMIS user workshop, Frascati, 8-9 October 2007

Tropospheric NO2 measured by satellites— closing remarks —

• Retrieval of trop NO2 has evolved considerably over the past eleven years

• Large differences remain

• In spite of that, trop NO2 is used successfully in many applications

• Much more data is available with OMI and now also GOME-2

• We want to understand the differences, in order to:

– improve the retrieval

– know how we can use the data in applications

– Estimate uncertainties and their characteristics

– optimise future satellite missions

TEMIS user workshop, Frascati, 8-9 October 2007

Tropospheric NO2 measured by satellites— Main recommendations and follow-up activities —

• Intercomparison of different retrieval methods. Objective: to understand and quantify the effect of the different retrieval choices on trop NO2 values and

accuracies. Organisation:

– Slant columns: retrieval groups

– Final product, incl AMFs: Ron Cohen

• Need for high spatial resolution input of surface albedo, aerosol, clouds, surface pressure/terrain height into the retrieval

• Validation campaign to assess the accuracy of (mini-) MAXDOAS and NO2 lidar. This

should include accurate in-situ tropospheric profiles, which we don't have yet! (Folkard Wittrock / Ankie Piters)

TEMIS user workshop, Frascati, 8-9 October 2007

Tropospheric NO2 measured by satellites— Main recommendations and follow-up activities —

• Make all validation data easily accessible

• Provide harmonized NO2 data sets based on existing networks (GEOMON)

• Recommend use of remote sensing instruments (e.g. MAXDOAS) in existing airquality networks.

• Provide Averaging Kernel in satellite products and make use of it

• Better assess uncertainty in top-down emission estimates(uncertainties both due to model and retrieval errors).Investigate implications of limited model resolution, e.g. onNO2-OH coupling relevant for NO2 lifetime

• Exploiting the higher spatial resolution possible with OMI (down to 5km)