Overview: Recent advances in the understanding of the northern Eurasian environments and of the urban air quality in China – a Pan-Eurasian Experiment (PEEX) programme perspective
Authors: Lappalainen Hanna K. , Petäjä Tuukka , Vihma Timo , Räisänen Jouni , Baklanov Alexander , Chalov Sergey , Esau Igor , Ezhova Ekaterina , Leppäranta Matti , Pozdnyakov Dmitry , Pumpanen Jukka , Andreae Meinrat O. , Arshinov Mikhail , Asmi Eija , Bai Jianhui , Bashmachnikov Igor , Belan Boris , Bianchi Federico , Biskaborn Boris , Boy Michael , Bäck Jaana , Cheng Bin , Chubarova Natalia , Duplissy Jonathan , Dyukarev Egor , Eleftheriadis Konstantinos , Forsius Martin , Heimann Martin , Juhola Sirkku , Konovalov Vladimir , Konovalov Igor , Konstantinov Pavel , Köster Kajar , Lapshina Elena , Lintunen Anna , Mahura Alexander , Makkonen Risto , Malkhazova Svetlana , Mammarella Ivan , Mammola Stefano , Buenrostro Mazon Stephany , Meinander Outi , Mikhailov Eugene , Miles Victoria , Myslenkov Stanislav , Orlov Dmitry , Paris Jean-Daniel , Pirazzini Roberta , Popovicheva Olga , Pulliainen Jouni , Rautiainen Kimmo , Sachs Torsten , Shevchenko Vladimir , Skorokhod Andrey , Stohl Andreas , Suhonen Elli , Thomson Erik S. , Tsidilina Marina , Tynkkynen Veli-Pekka , Uotila Petteri , Virkkula Aki , Voropay Nadezhda , Wolf Tobias , Yasunaka Sayaka , Zhang Jiahua , Qiu Yubao , Ding Aijun , Guo Huadong , Bondur Valery , Kasimov Nikolay , Zilitinkevich Sergej , Kerminen Veli-Matti , Kulmala Markku 
Published: April 2022

Abstract. The Pan-Eurasian Experiment (PEEX) Science Plan, released in 2015, addressed
a need for a holistic system understanding and outlined the most urgent
research needs for the rapidly changing Arctic-boreal region. Air quality in China, together with the long-range transport of atmospheric pollutants, was
also indicated as one of the most crucial topics of the research agenda.
These two geographical regions, the northern Eurasian Arctic-boreal region and China, especially the megacities in China, were identified as a “PEEX region”. It is also important to recognize that the PEEX geographical
region is an area where science-based policy actions would have significant
impacts on the global climate. This paper summarizes results obtained during
the last 5 years in the northern Eurasian region, together with recent observations of the air quality in the urban environments in China, in the context of the PEEX programme. The main regions of interest are the Russian
Arctic, northern Eurasian boreal forests (Siberia) and peatlands, and the megacities in China. We frame our analysis against research themes
introduced in the PEEX Science Plan in 2015. We summarize recent progress towards an enhanced holistic understanding of the land–atmosphere–ocean systems feedbacks. We conclude that although the scientific knowledge
in these regions has increased, the new results are in many cases
insufficient, and there are still gaps in our understanding of large-scale climate–Earth surface interactions and feedbacks. This arises from limitations in research infrastructures, especially the lack of coordinated,
continuous and comprehensive in situ observations of the study region as
well as integrative data analyses, hindering a comprehensive system
analysis. The fast-changing environment and ecosystem changes driven by
climate change, socio-economic activities like the China Silk Road
Initiative, and the global trends like urbanization further complicate such
analyses. We recognize new topics with an increasing importance in the near
future, especially “the enhancing biological sequestration capacity of
greenhouse gases into forests and soils to mitigate climate change” and the “socio-economic development to tackle air quality issues”.