task group 3 achievements and prospects ankie piters, knmi

AT2 workshop, 30 Sept – 1 Oct 2008

Task Task Group 3Group 3

Task Group 3 Task Group 3 Achievements and Achievements and

ProspectsProspectsAnkie Piters, KNMI



Activities

2005/6: Participation in Dandelions campaigns

2006: CO session during AT2 Recommendations

2007: Tropospheric NO2 workshop (inter-TG)

Recommendations

2007/8: Investigate what is needed to assess accuracy of MAX-DOAS trop. NO2 profiles

campaign in GEOMON/CEOS framework



Trop. NO2 validation, latest results within TG3

(also: Brunner et al, Masieri et al talks today)



Comparison with MAXDOAS

OMI and SCIAMACHY tropospheric NO2 have good

agreement with MAXDOAS Dandelions data set (3 instruments)

Brinksma et al, JGR, 2008

Schönhardt et al, 2007

Estimated uncertainty: 30-50%



Spatial representativity

high spatial inhomogeneity

Brinksma et al, JGR, 2008

Ratio of maximum and minimum SCD versus time when looking in different directions



MAXDOAS/in-situ/NO2lidar intercomparisons

What is the accuracy of the different correlative instruments?

Wittrock et al, NO2 workshop, 2007



Recommendations from NO2 workshop

• Determine accuracy of (mini-)MAXDOAS and NO2 lidar in campaign

• Have mobile campaigns through China (distance to source)

• Validate input data used in the retrievals (surface albedo and trop. profile)

• Small campaigns for special situations: e.g. snow/ice + pollution

• Establish (mini-)MAXDOAS network for long-term satellite validation

• Combine models, in-situ surface and RS measurements for validation

• Make better use of available (validation) campaign data bases

• Join planned campaigns with additional tropospheric NO2 measurements



GEOMON/CEOS campaign

• Objective: intercomparison of NO2 measuring instruments,

characterisation of uncertainties

• Including a blind intercomparison with referee

• Sponsored by ESA, NASA, GEOMON, …

• 6-10 (mini-)MAXDOAS, NO2 lidar, in-situ instruments (0-

200m), UV-Vis RS instruments

• Groups from Europe, USA, (Asia)

• Probably in Cabauw/NL (other options still open)

• June(/July) 2009



CO validation, latest results within TG3

(also: Dils et al talk today)



CO validation achievements

• FTIR Paramaribo (Surinam): 7 campaigns in the dry seasons

• Comparison of CO to MOPITT (red circles) shows general good agreement

• CO plumes from forest fires detected in both data sets, not in model (green dots)

Notholt et al, 2008



• MOPITT CO is generally larger than SCIAMACHY CO, which is again larger than modeled values, notably in the NH

• Consistent with the Northern Hemisphere bias demonstrated in many CTMs (Shindell et al, 2006)

de Laat et al, 2008



CO recommendations (2006)

• Exploit the use of aircraft data (e.g. MOZAIC, limited to polluted areas?) for validation

• Exploit the synergetic use of in-situ surface with models

• Use mobile FTS for measurements near source areas

• Have instruments or campaigns at high-albedo places

Did any of these have a follow-up yet??

• FTIR data sparse, often at high altitude or near sea



Other results within TG3



Acetylene: C2H2 (7-15km)

Mahieu et al, 2008

• ACE-FTS C2H2 (7-15km) agrees reasonably well with FTIR partial columns

• ACE-FTS seems to be slightly high biased in summer



Some results outside TG3



First HCHO validation

• Phase of seasonal variations roughly consistent

• FTIR observations report much larger HCHO columns especially in summer

• Effect of local emissions in a coastal site, not captured at the resolution of the satellite measurements?

De Smedt, Van Roozendael, et al, DOAS workshop, 2008

FTIR data from N. Jones



Validation needs for HCHODe Smedt, Van Roozendael, et al,

DOAS Workshop 2008

• Current status: in-depth validation of GOME HCHO only available for Northern US, based on aircraft data from INTEX-A campaign (Millet et al., 2006)

• What is needed:large scale (global) validation based on independent HCHO column measurements sampling the time/space variability of both biogenic and biomass burning emissions

• How can this be achieved?

– Conduct more aircraft campaigns

– Extend network of ground-based remote-sensing instruments (FTIR and MAXDOAS)

– Use GMES/GEOSS to develop network capacities, improve data accessibility and QA/QC (cf. FP6 GeoMON)

– Use model to link columns with in-situ measurements



Conclusions / Prospects

Validation strategies and requirements for tropospheric NO2 are well underway

More can be done for validation of CO (combined campaign for IASI, MOPITT, AIRS, SCIAMACHY)

Validation of cloud properties, aerosol, HCHO, trop. O3,

……(?), could use more attention

We have to move towards quantification of uncertainties and bias for tropospheric satellite products

task group 3 achievements and prospects ankie piters, knmi

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