University of Bremen IUP DOAS





IUP Bremen DOAS Blog

Retrieving NO2 profiles from MAX-DOAS measurements in the Po valley

Paolo Pettinari, CNR-ISAC, 07.04.2022

In the frame of the IDEAS-QA4EO project “Sviluppo delle Infrastrutture e Programma Biennale degli Interventi del Consiglio Nazionale delle Ricerche Potenziamento Infrastrutturale: progetti di ricerca strategici per l’ente. Progetto 32 – ASSE NORD Pianura Padana Mt. Cimone, Bologna, San Pietro Capofiume”, the Italian research institute CNR-ISAC bought a new MAX-DOAS instrument called SkySpec2D. Since no MAX-DOAS measurements, able to meet the FRM4DOAS standard requirements, were present in the Po Valley, the purpose was to fill this gap in one of the most polluted regions in Europe. After two inter-calibration campaigns, organized to evaluate the SkySpec2D performances, my colleagues, Elisa Castelli and Enzo Papandrea, and I installed the MAX-DOAS instrument at the measurement site located in San Pietro Capofiume, in the middle of the Po Valley, on 1st October 2021 (see image below).

We started our work retrieving the NO2 total Vertical Column Densities (VCDs) from zenith-sky spectra because it didn’t require a complex retrieval algorithm that we had not yet developed. However, I performed a further step during my period abroad. On 10th January, I moved to Bremen, where I spent three months of my PhD and worked with the DOAS group of the Institute of Environmental Physics at the University of Bremen, under the supervision of Dr Andreas Richter. Here, I started to analyze the SkySpec2D off-axis measurements to retrieve NO2 vertical profiles.


Paolo Pettinari in San Pietro Capofiume (Italy) during the installation of a SkySpec2D MAX-DOAS instrument.

In the beginning, I performed a characterization of the MAX-DOAS instrument. Then, I optimized the measurement strategy and checked the instrument’s pointing stability and the best viewing directions. I then applied the BOREAS algorithm, developed by Tim Bösch at IUP Bremen, to the NO2 Slant Columns Densities (SCDs) estimated from the DOAS fit to retrieve NO2 vertical profiles in the Po Valley. An example of the retrieved NO2 profiles is shown in the figure below on the left.

The last step of my stay in Bremen was focused on using the retrieved profiles to validate the NO2 tropospheric columns measured by TROPOMI onboard S5P (results in the figure below on the right).


NO2 vertical profiles in the Po Valley as retrieved by BOREAS from MAX-DOAS elevation scans in the 120° azimuth direction for 14th December 2021 (on the left). Comparison between MAX-DOAS and TROPOMI NO2 tropospheric VCDs for October 202 (on the right).

Even though everything was new for me, it’s been quite easy to achieve the expected results due to both important suggestions, the consequence of a strong DOAS experience at IUP, and the group’s positive mood that made me feel part of them soon.

Maintenance stay at the research station in Ny-Ålesund (14.3.-28.3.2022)

Lisa Behrens and Tim Bösch, 06.04.2022

About the research station

Ny-Ålesund is the northernmost year-round research station in the world. The village is located at 78°55‘N, 11°55‘E in the bay of the Kongsfjorden. Only 30 to 35 people are living permanently at the station. In summer, the population increases up to 114 due to high research activities. Currently, 19 institutions from 11 countries are represented at the station. Ny-Ålesund was established by a private coal mining company called “Kings Bay Kull Compani AS“ in 1917. Between 1917 and 1929, Ny-Ålesund was also a starting point for several expeditions attempting to reach the North Pole. In 1933, the Norwegian state took over the ownership of the company. The main interest was establishing the village as a tourist destination and its usage as a fishing port. The coal mining activities resumed between 1945 and 1962. Several mining accidents occurred, with the worst in 1962 killing 21 miners and leading to the shutdown of the mining activities. In 1967, the transition to a research station was initiated. Kings Bay still provides the research infrastructure for a broad research community.


The village Ny-Ålesund with the Zeppelin Mountain in the background. View from the harbour. (Photo: Lisa Behrens).

How to get to Ny-Ålesund?

Getting to Ny-Ålesund is not that easy. One possibility is a cruise vessel during summer, which tourists typically choose. Another possibility is an aeroplane. We first took an aircraft to Longyearbyen, the capital of Spitsbergen, which included an overnight stay in Oslo. From Longyearbyen, a small plane to Ny-Ålesund is operated by Kings Bay twice per week (usually Monday and Thursday). The plane is a Dornier 228 (Do 228), being a twin-turboprop aircraft with space for 14 passengers + 2 pilots.

The schedule of these small planes depends strongly on the weather conditions. With high wind speeds, the aircraft cannot fly. This was the case for our flight to Ny-Ålesund, and we were delayed by a few hours.

Scientific work

The IUP Bremen operates a DOAS instrument in Ny-Ålesund since 1995. The instrument is installed on the roof of the observatory building. The original focus was on stratospheric measurements in the arctic regions being influenced by the polar vortex, which is especially interesting for ozone chemistry. Another focus is on polar tropospheric halogen chemistry, particularly bromine chemistry. Depending on the meteorological conditions, events of ozone destruction can frequently be observed in relation to high bromine concentrations. Furthermore, pollution by nitrogen dioxide and sulphur dioxide from cruise vessels can be investigated. In April 2011, the current telescope with a pan-tilt-head and a two-channel spectrometer system was installed. This type of telescope allows measurements in various azimuth and elevation angles. Thus, the telescope moves the whole day in harsh weather conditions, leading to the need to replace some parts and cables from time to time. The replacement of the cables and light fibre was part of our activity.

On Tuesday, the 15.3.2022, a new temperature record was measured in Ny-Ålesund with -5.5°C, while temperatures of about -14°C would have been expected. These high temperatures were related to precipitation in terms of rain or freezing rain. After a few days, weather conditions improved a lot, and we had sunny weather with -18°C. Due to these rapidly changing weather conditions, we had to re-schedule our work. We replaced all cables leading through the window from the laboratory to the instrument on the roof, refurbished the telescope, and replaced the CCD of the visible spectrometer. Luckily, we finished our work in time. By the end of the second week, we waited for some clear sky days to let the instrument do some test measurements. This waiting gave us a bit of freedom to enjoy the beautiful environment of Svalbard!


The Observatory of AWIPEV, where the DOAS instrument is located (Photo: Tim Bösch).

Social life

Besides work, social life is essential in such a remote destination. Kings Bay operates a canteen serving food on weekdays at 7:30, 12:00, and 16:30 for one hour. On the weekend, they serve a delicious brunch, and on Saturday evening, there is a special dinner. All people are well-dressed (if possible), and it is the only meal where alcoholic drinks are allowed. Afterwards, the bar opens, and people can enjoy the beautiful view over the tundra with music and good company.

When leaving the village, a rifle is needed due to possible contact with polar bears. However, with such protection, nice trips can be made with skis, snowshoes, ski-doos or simply by hiking. All over Svalbard, there are small huts that can be used for a small rest or an overnight stay.

We did a ski tour to visit one of these huts and see the seals in the Kongsfjorden, which enjoyed the beautiful sunny weather and -18°C on a small island. Another trip led us to Corbel. This is a French station from 1963, located approximately 5 km away from Ny-Ålesund. You could enjoy the view over the fjord and the glaciers at this place.

On our last day, we could participate in a short round trip to the Engelskbukta, approximately 30 km away from Ny-Ålesund. It was a long trip with ski-doos, where we had to pass some iced rivers. We visited some huts on our way to the bay, saw several reindeers, and enjoyed the beautiful landscape. Close to Engelkbukta, we could see the whole “Prins Karls Forland”, an 80km long island belonging to Svalbard. This was an excellent example of the incredibly clear sky, which one can only experience in remote and unpolluted places like Ny-Ålesund.

Outside the village a rifle is needed (Photo: Lisa Behrens).
Seals in Kongsfjorden (Photo: Tim Bösch).
Corbel, French station, 5km away from Ny-Ålesund (Photo: Lisa Behrens).

SO287-CONNECT cruise onboard RV Sonne from Las Palmas (Gran Canary, Spain) to Guayaquil (Ecuador) (11.12.2021 - 11.01.2022)

Miriam Latsch, 05.04.2022

The SO287-CONNECT cruise of the research vessel (RV) Sonne departed Gran Canary in the western subtropical Atlantic Ocean on 11 December 2021. We sailed along the North Equatorial Current to the Sargasso Sea as the northernmost point of the voyage and crossed the Caribbean Sea. After an exciting transit through the Panama Canal, we entered the tropical Pacific Ocean, finally reaching the port city of Guayaquil in Ecuador on 11 January 2022, after 11,000 km of transit. Onboard the RV Sonne traveled 30 ship’s crew members and 39 scientists with a variety of research interests (e.g., biogeochemical, ecological, atmospheric). For example, the oceanographers investigated nutrients and many different chemicals of natural and anthropogenic origin from the water at various depths, as well as microplastics in the oceans.


Miriam Latsch and Tim Bösch below the two MAX-DOAS telescopes installed on Deck 10, measuring scattered sunlight in the atmosphere to determine concentrations of atmospheric trace gases (Photo: Tim Bösch).

We from the DOAS group at IUP Bremen measured atmospheric trace gases with our instruments on Deck 10, which is about 27 meters above the water surface (see picture above). Observations of scattered sunlight were carried out using an Avantes spectrometer in MAX-DOAS configuration and a MAX-DOAS system to analyze the amount of absorption of trace gases in the atmosphere, such as NO2, Ozone, and SO2. These gases are key parameters for air quality and are emitted by ships, for example. Furthermore, in situ measurements of NOx, SO2, CO, and Black Carbon were conducted to better determine the impact of different sources, e.g., passing ships.

Ship emissions have an impact on the environment and human health, and the aim of measurements of atmospheric pollutants during the SO287-CONNECT cruise was to monitor the contribution of ship emissions and long-range transport of anthropogenic pollution and biogenic emissions on air quality and air chemistry in the marine troposphere over the remote Atlantic and the Eastern Pacific. We are also interested in whether ship emission regulations are being followed. Therefore, trace gas profiles were retrieved in the marine troposphere, and the measurements will be compared with satellite and model data, which enables us to assess the air pollution of ships on a larger scale.

Unfortunately, we did not have permission to measure in the Panama Canal or near the coast, where we expected to find more ship and anthropogenic emissions than, for example, in the middle of the Atlantic Ocean.


RV Sonne (Photo: Miriam Latsch)

Besides the scientific work that had to be done, we experienced a very special and interesting life on board during the cruise. The most exciting days were celebrating Christmas and New Year’s Eve on the ship with people from eleven nations at warm tropical temperatures. We learned some rituals from other countries, sang the most popular national Christmas songs in different languages, danced a Scottish ceilidh dance, and exchanged presents at Secret Santa. Furthermore, it was the first time in our lives, that we toasted the New Year five times on the same day due to the many nationalities. After a long time on board, seeing mainly only water around us, we ended the working part of the cruise in the Pacific with a tour around the RV Sonne in the ship’s boat, seeing the big RV Sonne from an unfamiliar perspective as a small ship in the big ocean (see photo above).

GMAP-2021 campaign in South Korea

Kezia Lange, 01.04.2022

In October and November 2021, four members of the DOAS group participated in the GEMS Map of Air Pollution (GMAP-2021) campaign in South Korea. This campaign brought together instruments from South Korea, the US, Belgium, the Netherlands, and Germany to collect data on air pollution in South Korea for the validation of the GEMS (Geostationary Environment Monitoring Spectrometer) satellite instrument. We installed a MAX-DOAS instrument on the rooftop of the NIER (National Institute of Environmental Research) building at Incheon, close to Seoul. Similar instruments were deployed by other groups in the Seoul Metropolitan Area and other parts of South Korea. In addition, we performed car DOAS measurements coordinated with two other car DOAS instruments operated by the Max-Planck Institute for Chemistry and the Belgian Institute for Space Aeronomy, airborne DOAS and the GEMS measurements. All these instruments provide data on the abundance of NO2, HCHO and SO2, which is valuable for validating GEMS retrievals.


Group picture of some participants on the NIER rooftop. The IUP MAX-DOAS telescope is operating in the left background. (Photo: Steffen Dörner)


Car DOAS instrument measuring pollution distribution in Gangnam, Seoul, crossing the Han River. (Photo: Kezia Lange)

Besides the scientific work, we had several opportunities to have delicious Korean food for dinner with our European and Korean colleagues. We had traditional Korean barbecue, Tteokbokki, Buchimgae and a lot of Kimchi together with Korean beer and Soju.

On days without measurements, we had the chance to explore Seoul, the area of our measurements, from a different perspective. We visited the traditional palaces Gyeongbokgung and Changdeokgung in the middle of the modern, busy city, the historical mountain fortress Namhansanseong and Namsan tower, the second-highest point in Seoul from which one has a great view over the city with its population of 9.7 million people. Thanks to various efforts, air quality has improved over the last years, but air pollution remains a significant problem with high amounts of NO2 we could measure on several days. High aerosol load also continues to be a problem, as can be seen in the photo showing the view from the fortress to the city of Seoul.


Two Korean women in the traditional hanbok in front of the Gyeongbokgung palace entrance gate. (Photo: Andreas Richter)


View from the Namhansanseong fortress to the city of Seoul with the 555.7 m high Lotte World Tower, the sixth tallest building in the world, on a hazy day. (Photo: Kezia Lange)

web master:      Last Update: 20-04-2022      Data Privacy