Conference Agenda

The Northern China was hit by a severe dust storm on March 15, 2021, covering a large area and bring devastating impact to a degree that was unprecedented in more than a decade. In the study, we carried out a day-and-night continuous monitoring to the dust moving path, using multi-spectral data from the Chinese FY-4A satellite combined with the Japanese Himawary-8 from visible to near-infrared, mid-infrared and far-infrared bands. We monitored the whole process of the dust weather from the occurrence, development, transportation and extinction. The HYSPLIT backward tracking results showed two main sources of dust affecting Beijing during the north China dust storm: one is from western Mongolia; the other is from arid and semi-arid region of northwest of China. Along with the dust storm, the upper air mass, mainly from Siberia, brought a significant decrease in temperature. The transport path of the dust shown by the HYSPLIT backward tracking is consistent with that revealed by the satellite monitoring. The dust weather, which originated in western Mongolia, developed into the “3.15 dust storm” in north China, lasting more than 40 hours with a transport distance of 3900km andcaused severe decline in air qualityin northern China, Korean peninsula and other regions. It is the most severe dust weather in past 20 years in east Asia.

Arctic region has experienced the most rapid climate change impacts in the entire globe during the recent decades. Sea level is a key climate change indicator is which integrates the response of different components of the earth’s system to natural and anthropogenic forcings. Moreover, monitoring sea level change in the Arctic, of high importance since it has a wide range of economic and social consequences. Sea level changes in regional systems such as the Arctic Ocean can differ from Global Mean Sea Level (GMSL) both in terms of magnitude as well as governing forcing and mechanisms. For instance, while changes in salinity can have significant distinct impact on regional sea level change, such as in the Arctic Ocean, it has minor effect on GMSL.

Quantifying the natural variability in the regional sea level change is also urgent in order to distinguish it from a potentially forced (anthropogenic) signal. Furthermore, the role of remote impact of climate variability from one region to another needs to be well-understood. Natural climate variability in the Pacific Ocean can, for instance, impact the Arctic Amplification and thus the sea ice conditions (Li et al., 2015; Svendsen et al., 2018; Yang et al., 2020). The way in which this translates into sea level change, on the other hand, remains unclear. The aim of this study is to examine and relate the sea level variability of the Arctic fresh water reservoir, the Beaufort Gyre (BG), to natural climate variability of the Pacific Ocean.

First, we present the recent advancements in the Arctic Sea level research from space. In particular, the focus is on the results obtained from the analysis of the recent ESA CryoTEMPO data and CNES AltiDoppler data. One of the findings is that the continuous westward extension of the BG observed during the time-period 2003-2014 (Regan et al., 2019) is no longer evident after 2016. In fact, the spatial extent of the gyre during the past decade is the lowest in 2020. Our analysis reiterates the role of large-scale atmospheric circulation on BG sea level variability. Next, we present that the boreal autumn Eurasian snow cover can influence the following winter Arctic sea ice, which further modulates the Rossby wave propagating from troposphere to stratosphere and finally impacts on stratosphere polar vortex. The stratosphere signals further propagate downward to the troposphere, leading to Arctic Oscillation-type circulation anomalies, consequently induce co-variability of climate between Pacific and Arctic. Finally, we present preliminary results of a study analysing the role of Pacific Ocean on the sea level variability of the Beaufort Sea using satellite altimetry, CMIP6 models (20+) and a 10 km resolution NEMO-NAA10km model (dynamical downscaling of NorESM climate model).

In the past two years, based on in-situ observations, reanalysis data, satellite remote sensing, and numerical model, we have made the following research progress in the energy and water cycles of the Tibetan Plateau:
1. Field observation: a) A three-dimensional comprehensive observation and research platform for water and heat exchange between ground and air on the Tibetan Plateau has been established. It has built 27 integrated observation stations for the interaction of the land and the atmosphere (atmospheric boundary layer tower system, eddy correlation observation system), 10 microwave radiometers and 5 radiosonde systems, 3 soil temperature and humidity observation networks, The "Three-dimensional Comprehensive Observation and Research Platform of Water and Heat Exchange between Land and Air on the Tibetan Plateau" consists of 11 observation points of land-atmosphere interaction and 10 sets of wind blowing snow instruments. The platform can realize multi-element, weather comprehensive integrated observation of the near-surface layer and troposphere of the Tibetan Plateau, and provide comprehensive observation data, research basis and decision-making basis for weather monitoring and forecasting, severe weather warning and climate environment prediction in the region and its surrounding areas. b) The monthly average evapotranspiration (ET) of the Tibetan Plateau was obtained by precise calculation. Based on the long-term continuous observation data of the three-dimensional comprehensive observation network system of multi-layer ground-atmosphere interaction in the third pole region built by scientific research, using the improved SEBS model, combined with the MODIS satellite remote sensing data and reanalysis data, the calculation results of the 2001-2018 period were obtained. The monthly average ET of the Tibetan Plateau was verified using the observation data of 6 turbulent flux stations. The new research results show that the average annual total ET (2001-2018) of the Tibetan Plateau is 1.238 ± 0.058 trillion tons, but there are large spatial differences in its annual trend. At the same time, it was found that the evapotranspiration of the plateau increased in the east and decreased in the west, but the overall trend was decreasing.
2. Remote sensing: Using the domestic FY-4A/AGRI satellite data, a set of inversion methods for surface characteristic parameters of the Tibetan Plateau and a surface flux estimation scheme were developed, and hourly resolution ground gas flux data was established, revealing surface temperature and Spatiotemporal characteristics of surface turbulent fluxes.
3. Reanalysis data: revealed the interdecadal variation characteristics of atmospheric heat sources over the Tibetan Plateau in summer. Based on five reanalysis datasets from 1979 to 2019, the characteristics of interdecadal variability of atmospheric heat sources in the Tibetan Plateau region in summer and their relationship with the teleconnection of the Eurasian Silk Road were analyzed. The development of this research work has revealed the interdecadal variation characteristics of the Tibetan Plateau's atmospheric heat source in summer, and deepened the understanding of the influence of the Tibetan Plateau's dynamic and thermodynamic effects on the summer's atmospheric heat source.
4. Numerical simulation: understanding of the development and evolution mechanism of the heavy snowfall process on the Tibetan Plateau. The circulation background, water vapor conditions, thermal conditions and dynamic conditions of a large-scale heavy snowfall process on the Tibetan Plateau were systematically analyzed by using a comprehensive analysis method combining quantitative diagnosis of physical quantities with WRF simulation. This research not only deepens the understanding of the development and evolution mechanism of the heavy snowfall process on the Tibetan Plateau, but also provides a theoretical reference and scientific basis for accurately forecasting short-term heavy snowfall in the Tibetan Plateau and developing sustainable animal husbandry, so as to improve the ability of disaster prevention and mitigation.
5. Cultivate young scientists in the field of climate and environment. A doctoral student went to the University of Twente for the Dragon Program joint training. 5 graduate students (including 2 doctors and 3 masters).