Final Report Summary - EXCATRO (In-situ experiments on the chemical composition of high altitude aerosols and clouds in the tropical upper troposphere and lower stratosphere)
Chemical composition of fine aerosol particles in the at high altitude region of the Asian Monsoon:
The Asian Tropopause Aerosol Layer (ATAL) extends over the Middle East and Asia at an altitude of 12 to 18 kilometers. This accumulation of fine particulate matter was observed from the satellite for the first time during the Asian monsoon of 2008. However, its composition and effect have not been studied yet. Within the EXCATRO project the novel aerosol mass spectrometer ERICA (ERC Instrument for Chemical composition of Aerosols) was developed as worldwide unique scientific instrument. It was implemented in a specialized high altitude research aircraft and performed in-situ online measurements of the aerosol chemical composition from the ground to altitudes of 20 km during the summer monsoon 2017 in Nepal. By means of ERICA it was possible to directly probe the Asian Tropopause Aerosol Layer (ATAL) for the first time. A long standing and highly controversial open scientific question concerning the chemical nature of the dust particles in the ATAL during the monsoon period could be solved this way. The results obtained from ERICA show that most of the small dust particles consist of ammonium-nitrate. Such particulate ammonium-nitrate is produced from gaseous ammonia, which is mainly found in agricultural processes and is primarily released into the atmosphere through livestock farming and crop fertilization. The highest levels of ammonia emissions are currently to be found in Asia. During the monsoon the polluted air masses are transported from the Earth’s surface to altitudes as high as 18 kilometers. On its way the ammonia chemically reacts to form the ammonium-nitrate, an aerosol that affects both the formation and properties of clouds. Thus it became evident that anthropogenic agricultural activities directly influence the atmosphere and the climate at high altitudes. The chemical analyses carried out by means of the ERICA instrument during the research flights from Nepal also demonstrated the presence of traces of sulfurous material in individual fine aerosol particles. Small amounts of particulate sulfate turn the liquid ammonium nitrate solution droplets into solid particles, which is crucial for cloud formation. After the monsoon period these ATAL aerosols enter global atmospheric transport and become distributed worldwide. Thus these processes are of significance for the global climate.
The ERICA instrument for the first time combines two fundamentally different mass spectrometric techniques in a single, autonomous apparatus. One instrumental component of ERICA is a laser ablation mass spectrometer (ERICA-LAMS) the second being a flash vaporization / electron impact ionization mass spectrometer (ERICA-AMS). While ERICA-LAMS can detect qualitatively the chemical composition of single individual sub-micrometer sized aerosol particles, the ERICA-AMS component provides quantitative information on different chemical species (i.e. particulate sulfate, nitrate, ammonia, and organics). Although ERICA is a newly built prototype with a novel design, it operated reliably and fully automated on the Russian M-55 “Geophysica” high altitude research aircraft during all of the scientific flights from Kathmandu (Nepal) and in Kalamata (Greece). This constitutes a significant experimental and scientific success. Further in-situ measurements performed on board the Geophysica by the Mainz-based scientists within the EXCATRO project provided hitherto unavailable, important data on the sizes and quantities of aerosol particles in the ATAL. By using this information, satellite observations can be analyzed and validated, and the numerical simulations of the global climate can be improved. The findings concerning the ATAL layer of the Asian monsoon were published in Nature Geoscience in July 2019.
The Asian Tropopause Aerosol Layer (ATAL) extends over the Middle East and Asia at an altitude of 12 to 18 kilometers. This accumulation of fine particulate matter was observed from the satellite for the first time during the Asian monsoon of 2008. However, its composition and effect have not been studied yet. Within the EXCATRO project the novel aerosol mass spectrometer ERICA (ERC Instrument for Chemical composition of Aerosols) was developed as worldwide unique scientific instrument. It was implemented in a specialized high altitude research aircraft and performed in-situ online measurements of the aerosol chemical composition from the ground to altitudes of 20 km during the summer monsoon 2017 in Nepal. By means of ERICA it was possible to directly probe the Asian Tropopause Aerosol Layer (ATAL) for the first time. A long standing and highly controversial open scientific question concerning the chemical nature of the dust particles in the ATAL during the monsoon period could be solved this way. The results obtained from ERICA show that most of the small dust particles consist of ammonium-nitrate. Such particulate ammonium-nitrate is produced from gaseous ammonia, which is mainly found in agricultural processes and is primarily released into the atmosphere through livestock farming and crop fertilization. The highest levels of ammonia emissions are currently to be found in Asia. During the monsoon the polluted air masses are transported from the Earth’s surface to altitudes as high as 18 kilometers. On its way the ammonia chemically reacts to form the ammonium-nitrate, an aerosol that affects both the formation and properties of clouds. Thus it became evident that anthropogenic agricultural activities directly influence the atmosphere and the climate at high altitudes. The chemical analyses carried out by means of the ERICA instrument during the research flights from Nepal also demonstrated the presence of traces of sulfurous material in individual fine aerosol particles. Small amounts of particulate sulfate turn the liquid ammonium nitrate solution droplets into solid particles, which is crucial for cloud formation. After the monsoon period these ATAL aerosols enter global atmospheric transport and become distributed worldwide. Thus these processes are of significance for the global climate.
The ERICA instrument for the first time combines two fundamentally different mass spectrometric techniques in a single, autonomous apparatus. One instrumental component of ERICA is a laser ablation mass spectrometer (ERICA-LAMS) the second being a flash vaporization / electron impact ionization mass spectrometer (ERICA-AMS). While ERICA-LAMS can detect qualitatively the chemical composition of single individual sub-micrometer sized aerosol particles, the ERICA-AMS component provides quantitative information on different chemical species (i.e. particulate sulfate, nitrate, ammonia, and organics). Although ERICA is a newly built prototype with a novel design, it operated reliably and fully automated on the Russian M-55 “Geophysica” high altitude research aircraft during all of the scientific flights from Kathmandu (Nepal) and in Kalamata (Greece). This constitutes a significant experimental and scientific success. Further in-situ measurements performed on board the Geophysica by the Mainz-based scientists within the EXCATRO project provided hitherto unavailable, important data on the sizes and quantities of aerosol particles in the ATAL. By using this information, satellite observations can be analyzed and validated, and the numerical simulations of the global climate can be improved. The findings concerning the ATAL layer of the Asian monsoon were published in Nature Geoscience in July 2019.