Second AT2 Workshop
Steps towards collaboration

Held at the Hotel Munthe, Bremen from the 31st January to 2nd February, 2005

Workshop Report

2-1.   E-learning Group. The workshop was preceded by a meeting of the e-learning group from 09.30 to 13.00.
                 See the separate report for an account and the decisions


2-2    Workshop opening. The coordinator, John Burrows, opened the workshop by welcoming the group of some 60 people attending.

The workshop had been organised so as to give the task groups more time together in order to foster and plan collaborative work between the participating groups. He hoped the outcome would be a set of practical proposals from the task groups on future collaboration.

2-3    Task group Leaders. Brief presentations were then given by the three task group leaders.

          Martin Dameris, TG2

          Anki Piters, TG3

          Thomas Wagner, TG1

Each outlined the programme and expectations for the respective groups.

2-4    Task group Sessions. At 16.00 the workshop then split into three groups for the task group meetings.


Tuesday 1st February 2005


2-5    Plenary Talks. The meeting reconvened as a whole at 14.00 to hear four plenary talks.

Peter Borrell,
          P&PMB Consultants

The IGACO vision of the future of atmospheric observations

Jim Drummond,
          University of Toronto,

Carbon Monoxide: Measurements in Space, Height and Time; results from MOPPITT

Pieternel Leevelt,
          KNMI, Netherlands

The OMI instrument: First Results

Gerrit de Leeuw,
          TNO, Netherlands

Recent satellite results on aerosol optical depths.

2-6.   AT2 Business Session. See the separate report for an account and information.  


Wednesday 2nd February 2005


2-7.   Task Group Reports. The task group leaders gave reports and presentations on the actual and proposed activities of the groups.

Ankie Piters: TG3                      see report appended.

Martin Dameris: TG2                see report appended.

Thomas Wagner: TG1                see report appended.

2-7.   Conclusions: where do we go from here? John Burrows, the coordinator, wound up the meeting by thanking the principal investigators for their work and  task group coordinators for drawing the work together and for their suggestions for future joint activities.

As always, what we require is some vision of the future to work towards; two areas which require attention are the UT/LS which is still tricky with satellite measurements and the remote troposphere, for which satellites provide almost the only long-term way of observing and understanding.

He looked forward to seeing everyone again at the next workshop and to seeing a host of posters produced for Urbino.


The full workshop closed at 11.30 with thanks to Susanne Themm, for making all the arrangements, and to Heiko Schröter for providing the technical support.


2-8.   AT2 Steering Group meeting. The third meeting of the AT2 steering committee took place after the conclusion of the workshop.

Peter Borrell
P&PMB Consultants
Newcastle-under-Lyme, UK
11th February 2005


Task group 1 Report, Prepared by Thomas Wagner

AT2 Task Group 1

The development and improvement of algorithms for the retrieval of tropospheric data.


Report from the task group meeting

During the 2nd AT-2 workshop in Bremen (January 31 to February 2, 2005)

 1) Overview

 The aim of the workshop was to have an intense exchange of new results between all task group 1 participants and to agree on clear and reachable aims for the near future. A summary of the progress made by the participants is given below. Some highlights will be also presented at the AT2 website.

Near future activities will focus on two main aspects:

a) to collect relevant information on all available products analysed by the members of task group 1 and provide it to all members.

b) to have small specific workshops on selected common questions.

The intention of both activities is to intensify the cooperation between the participants. More details on the activities are given in section 2.

The workshop was attended by most of the members of task group 1; in total 25 presentations were given by the PI’s or representatives (see section 3). In many projects substantial progress has been made during the last months and several exciting results have been presented. Selected highlights are presented in a more detailed overview on the AT2 web-page.

The progress within the three sub groups should be shortly summarised:

A) UV/vis retrievals

In this sub group algorithms for tropospheric species exist already for a relative long period of time. During the recent months further refinement was applied to these algorithms and measurement results were also successfully used for scientific studies like e.g. trend analysis (NO2, H2O), comparison to emission inventories or lifetime estimation (both for NO2). Very first results of OMI were presented that demonstrate the potential of daily coverage and high spatial resolution.

B) Aerosol retrievals

In this sub group the improvement of algorithms was a main task. It was e.g. possible to derive detailed information on the size distribution of different aerosol compositions for selected case studies. Another achievement was the retrieval of monthly mean maps of aerosol optical depth over Europe on a routine basis.

C) IR retrievals

Especially for the analysis of the near IR observations of SCIAMACHY the last half year brought a major breakthrough. Besides the global distribution of CO in particular high quality global maps of CH4 could be extracted and showed excellent agreement with model data. Also recent CO2 data showed very interesting results.

In the thermal IR detailed CO maps over Europe were presented. After the successful launch of Aura retrievals are under development for TES.

 2) Future activities

It was decided to create short summaries for the various tropospheric products retrieved from satellites. These summaries should provide a quick overview and will be put on the AT2 web page. They should in particular serve as contact information to initiate and assist bi-lateral co-operations.

The content should address the following points:

- Who is providing the product?

- which instrument / retrieval?

- coverage / length of data set?

- known limitations / shortcomings

- validation results?

- comparison with models?

- near future progress, recommendations

-something more / less?

The following persons agreed to coordinate the creation of the short summaries. The summaries should be sent to Thomas Wagner ( and Peter Borrell by mid of March 2005.

CO                              Michael Buchwitz, IUP Bremen


CH4                             Christian Frankenberg, IUP Heidelberg


Trop. NO2                   Andreas Richter, IUP Bremen


Trop. O3                      Roland von der A, KNMI, DeBilt


Aerosols                      Wolfgang von Hoyningen-Hühne, IUP Bremen (

HCHO                         Thierry Marbach, IUP Heidelberg


 Future activities include also the organisation of various small workshops dedicated to specific and well defined questions. For some topics already locations (hosts) and times could be identified. For others hosts have still to be found. 

Workshop                                           Location / time                                   Interest (votes)

 RTM                                        Heidelberg / June 2005                                     14

CO NIR                                   ? / April 2005

Cloud effects                            ? / ? (OMI validation WS/ Garmisch?)              20

Aerosol /trace gas interact.        ? / ?                                                                              9

Surface reflection                      ? / ?                                                                              7

CO IR / NIR                            ? / Fall 2005                

International DOAS WS           ? / February 2006                                

 3) List of PIs who gave a presentation (or were represented)

 Steffen Beirle                              

Heinrich Bovensmann                      

Michael Buchwitz                                  

Pierre-François Coheur                             

Cathy Clerbaux                              

Jim Drummond                        

Henk Eskes                                

Christian Frankenberg     

Annemieke Gloudemans                                  

Thomas Holzer-Popp                 

Wolfgang von Hoyningen-Huene                           

Anton K. Kaifel                                

Johannes Keller                                    

Gerrit de Leeuw                             

Diego Loyola                              

Thierry Marbach                               

Mathias Milz                               

Stefan Noel                                

Johannes Orphal                               

Roeland van Oss                             

John J. Remedios                          

Andreas Richter                           

Michel Van Roozendael                                 

Pieter Valks                                

Pepijn Veefkind                                 

Thomas Wagner                                


Additional presentations were given from Co-workers:

Alexander A. Kokhanovsky        

Ronald von der A                       



AT-2 Task Group 2 Report, prepared by Martin Dameris

AT2 Task Group 2 Report

The synergistic use of models and observations” 

During the 2nd AT-2 workshop in Bremen (January 31 to February 2, 2005)

 Martin Dameris reported that 21 partner and associated PIs and their groups are joined within this TG. During the breakout sessions, 13 oral presentations were given discussing the scientific aims and achieved progress since the last workshop in June 2004. 3 PIs sent a short message via email and have apologised for being absent.

 The overall aims of TG 2 are: 

 A lot of interesting new results have been presented which impressively show the potential of this TG and that the TG is on a good way to achieve the goals of AT-2, in particular those of TG2. Several models, in particular Chemical-Transport Models (CTMs) and coupled Chemistry-Climate Models (CCMs) have been employed to evaluate their results with data products derived from satellite measurements. To get a complete overview about current activities, a matrix (see below) has been created during the meeting which puts together all models and data products which have been used in the first year of AT-2. Obviously, at present NO2 tropospheric columns derived from GOME/ERS-2 and SCIAMACHY/ENVISAT, CO columns derived from MOPITT, formaldehyde (HCHO) columns derived from GOME, and H2O columns and profiles derived from MIPAS/ENVISAT and GOME are mostly used. It is worth mentioning, that new climatologies of water vapour (e.g., monthly and seasonal mean values) are now available: (a) derived from GOME (“the GOME Water Vapour Climatology (GWC)”, total column amounts from 1995 to 2002); contact: Rüdiger Lang (, (b) derived from MIPAS/ENVISAT (latitude-altitude cross sections, from mid 2002 to 2003), contact: Mathias Milz (

 Two main areas of common interest have been identified which should be the basis for possible collaboration within the next 18 months: 

 In addition there will be other ongoing and new activities within TG2, for example, data assimilation with different techniques (for example, it has been shown that assimilation can significantly improve forecasts), so-called “inverse” modelling to get more reliable information about location and strength of emissions, or to develop and distribute techniques (to give recommendations) how to compare model results and measurements, or rather evaluate models.






Model (name)


Tropo. column



Strato./ Tropo. GOME/














Lighted Area






































































































































 The following persons were present at the TG2 breakout session of the 2nd AT-2 workshop:

 (1)               Attie, J.-L. (Uni Toulouse, France)

(2)               Beekmann, M. (CNRS, France)

(3)               Dameris, M. (DLR-IPA, Germany)

(4)               Erbertseder, T. (DLR-DFD, Germany)

(5)               Hvidberg, M. (NERI, Denmark)  

(6)               Kaminski, J.W. (Uni Toronto, Canada)

(7)               Kanakidou, M. (ECPL, Greece) 

(8)               Lang, R. (MPIC, Germany)

(9)               Milz, M. (FZK, Germany)

(10)           Stein, O. for Rohrer, F. (FZJ, Germany)

(11)           Savage, N.H. and Cook, P. (UCAM, U.K.)

(12)           Curci, G. for Visconti, G. (CETEMPS, Italy)

(13)           Schaub, D. for Weiss, A.K. (EMPA, Switzerland)


Short notes have been received from

 Elbern, H. (RIU, Germany)

Lawrence, M.G. (MPIC, Germany)

Smit, H.G.J. (FZJ, Germany)


AT2 - Task group 3 Report, prepared by Ankie Piters

 AT2 Task group 3 report;

During the 2nd AT-2 workshop in Bremen (January 31 to February 2, 2005)

 The development of validation strategies for tropospheric satellite data products using existing data.

 Report from the task group meeting

During the 2nd AT-2 workshop in Bremen (January 31 to February 2, 2005) 

1) Objective

The aim of this meeting was to discuss how cooperation within the Task Group and with the other Task groups can be organised, based on the objectives formulated during the first AT2 workshop in June 2004.

2) Progress of the individual teams

The PIs of the Task Group reported on their activities. Some highlights of the


-        First comparisons of OMI ozone columns with those measured with 22 Northern Hemisphere Brewers between 1 and 16 November show an average difference of only 1.8%, and an average standard deviation of 1.4% (Brinksma et al).


-        A SCIAMACHY validation workshop was hosted by ACCENT (Piters et al). One of the highlights from this workshop was that SCIAMACHY limb profiles of BrO and NO2, retrieved by IFE and SAO, are now succesfully compared with measurements performed during dedicated balloon campaigns, which are combined with chemical models and trajectory information (Stroh et al, Butz et al)

-        A mobile UV-VIS/IR system measures the decreasing CO column while driving out of Mexico city (Mellqvist et al).

-        Comparisons of CO from SCIAMACHY and MOPITT already shows average differences of typically less than 10% (van den Broek et al).

-        First combined measurements of the ground-truthing facility Zugspitze/Garmisch, with the same instrumentation (FTIR, lidar, GPS, UV, in-situ) at different altitudes are expected in fall 2005 (Sussmann et al).

-        An ultra-light airplane, measuring aerosol properties, radiation, albedo, meteoroligal parameters, ozone, and HCHO, is well suited for vertical and horizontal sampling of the local atmosphere, and therefore very usefull for detailed analysis of satellite measurements (Junkermann et al).

-        The horizontal and vertical distribution of NO2 can be partially resolved with MAXDOAS (Kramer et al).

-        Definition of a 'well-mixed' parameter and selection of well-mixed situations is a good tool for the validation of tropospheric NO2 from satellites (Petritoli et al).

3) SCIAMACHY CO column validation

There was a discussion on the difficulties in the comparison of CO with ground-based measurements and what we can organise to overcome these difficulties. CO retrieval scientists from TG1 joined this discussion.

There are 3 different retrieval algorithms developed (at IFE, Heidelberg, and SRON), which should be validated and intercompared. First validation should concentrate on the 'easy cases', where the retrieval is expected to work best.

This is for situations with high albedo, no clouds, not over ocean, flat surface, high sun (low sza), near CO sources, like fires or industrial areas, and shortly after SCIAMACHY decontamination. The current network of correlative

data used for SCIAMACHY CO validation consists of a dozen FTIRs, globally distributed, but often located on an island or on a mountain, and measurements from a ship, again a difficult situation for the retrieval of SCIAMACHY CO.

MOPITT is also used for the validation of SCIAMACHY CO, but MOPITT is less sensitive for boundary layer CO. The conclusion is that the current correlative measurements are not particularly suited for validation of the 'easy' cases.

The actions proposed during this meeting are:

  1. to extend the network of correlative measurements with the mobile uv-vis/ir system from Chalmers, the CMDL network (GAW stations), and with the validation networks of TES and MOPITT,

  2. to try and join existing or planned campaigns, e.g. the first AMMA campaign in Western Africa (winter 05/06) with a mobile FTS, and

  3. to investigate the use of models to convert in-situ (CMDL) measurements to representative measurements for comparison with SCIAMACHY CO columns. For the last action we should cooperate with Task Group 2. Furthermore we will send all above stations the SCIAMACHY  overpass information, involve the SCIAMACHY validation product coordinator and the already existing validation teams, and make a mailing list. A splinter meeting on CO validation will be held during the AT2 Workshop in June 2005.

4.    Tropospheric NO2 validation

There are 3-5 different retrieval methods for tropospheric NO2, differing with respect to the treatment of clouds, albedo, aerosol, stratosphere component, and the NO2 profile. Tropospheric NO2 is retrieved from GOME, SCIAMACHY, and OMI. Tropospheric NO2 from satellites should be validated with representative correlative measurements. The ground-based measurements should therefore be transformed in "satellite" measurements. To do this, one would need the actual tropospheric NO2 profile and the horizontal distribution on ground pixel scale. In addition, the assumptions used in the retrieval should be verified, with respect to clouds, aerosol, stratopsheric NO2 and albedo. Validation measurements therefore idealy should be done with several independent NO2 measuring devices (in-situ vs remote, column

vs profile) and withadditional instrumentation to measure relevant atmospheric conditions. The use of high resolution models should complete our knowledge on stratospheric and

tropospheric profiles, temporal variations due to transport and (photo-)chemistry, and should aid with the conversion from point to pixel measurement.

The actions proposed during this meeting are

  1. to exploit the already planned campaign in Cabauw (NL), in May 2005, by having additional in-situ and remote NO2 instruments available, optimising the SCIAMACHY operations for NO2 retrieval above Cabauw in that period, and measuring during SCIAMACHY overpasses;

  2. to investigate the possibility to set up a small campaign in the Po-Valley in 2005 or 2006, including the RIVM NO2 lidar;

  3. to organise a dedicated meeting on SCIAMACHY tropospheric NO2 (end 2005 or 2006).

Present at this meeting were:

Ellen Brinksma, KNMI (PI: Mark Kroon)

Miranda van den Broek, SRON

Louisa Kramer, University of Leicester (PI: Paul Monks)

Johan Mellqvist, Chalmers University (PI: Bo Galle)

Andrea Petritoli, ISAC

Ankie Piters, KNMI

Ralf Sussmann and Wolfgang Junkermann, IMK-IFU

Arnolds Ubelis, University of Latvia


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