ALBERT

Description: We will present results of ABRUPT, a project in which we simulate and reconstruct the sea ice conditions, ocean hydrography and climate of the Nordic Seas, over two targeted Dansgaard-Oechger events. Multi-model output from three transient glacial GCM simulations (NorESM, CESM, MPI-ESM) and high-resolution reconstructions from an eastern Nordic Seas transect (from the Faeroe-Shetland Channel to the Fram Strait) show that ocean-atmosphere-sea ice processes and dynamics during the transition from H4 to GI8 are strongly coupled. Both model results and reconstructions suggest subsurface ocean warming and polynya events in the southern- and northernmost Nordic Seas during the cold stadial. For a short time during the stadial to interstadial transition, a corridor of open water and hence sea ice-free conditions existed from the southern Nordic Seas all the way to the Fram Strait. The breakup of the sea ice cover is likely caused by the overshoot of AMOC during the transition and the associated enhanced ocean heat transport into the Nordic Seas. After the transition, winter sea ice grows back in the Fram Strait during the interstadial state, but the Southern Nordic Seas remain ice-free.

Description: The recent July 7-8 2022, Nov 3-4, 2021 events present a good opportunity to examine many aspects of the geomagnetic storm event with new model and available satellite missions. We will focus on the penetrating electric field. Using a new magnetosphere and ionosphere coupled model call MAGE (Multiscale Atmosphere-Geospace Environment), we are able to simulate fast reaction of the ionosphere to the dynamic input from the magnetosphere. We have used this model studied some winter events (Nov 3-4, 2021). The July 7-8, 2022 summer event presents different ionosphere condition in the northern hemisphere. Because of the availability of the COSMIC 2 ionosphere data, we will also examine the negative phase during these events.

Description: Recently low-cost, easily deployable nodal sensors initially developed for the petroleum industry, are widely used by seismologists to sample the seismic wavefield in dense arrays at unprecedented spatial resolution, and push the limits of resolution in microseismic events monitoring and subsurface imaging. With the increasing demand on the nodal sensors in the industry and seismological community, multiple commercial models of nodal sensors appear in the market and it becomes important to know the potential limitations and variabilities among these models. We conduct a number of laboratory and field experiments to better identify their fidelities. First, we carry out the shake-table tests to identify the sensitivities of these units, which enables us to convert sensor output to units of ground motion reliably. Then we estimate the self-noise of these sensors in a huddle test based on the three-sensor method, which defines the lowest signal that the sensor can discern. Finally all the models are deployed at several field sites for about one month, both the earthquake waveforms and green’s function retrieved from ambient noise are compared to show their differences.

Description: Climate change alters surface water availability (precipitation minus evapotranspiration, P–ET) and consequently impacts agricultural production and societal water needs, leading to increasing concerns on the sustainability of water use. Although the direct effects of climate change on water availability have long been recognized and assessed, indirect climate effects occurring through adjustments in terrestrial vegetation are more subtle and not yet fully quantified. To address this knowledge gap, here we investigate the interplay between climate-induced changes in leaf area index (LAI) and ET and quantify its ultimate effect on water availability during the period 1982-2016 at the global scale, using an ensemble of data-driven products and land surface models. We show that ~44% of the global vegetated land has experienced a significant increase in growing-season-averaged LAI and climate change explains 33.5% of this greening signal. Such climate-induced greening has enhanced ET of 0.051±0.067 mm yr〈sup〉-2〈/sup〉 (mean±s.d.), further amplifying the ongoing increase in ET directly driven by variations in climatic factors over 36.8% of the globe, and thus exacerbating the decline in water availability prominently in drylands. These findings highlight the indirect impact of positive feedbacks in the land-climate system on the decline of water availability, and call for an in-depth evaluation of these phenomena in the design of local mitigation and adaptation plans.

Description: The middle atmosphere plays an important role in the research of various dynamical and energy processes. Microwave Limb Sounder (MLS), reanalyses and model simulations with NCAR’s Whole Atmosphere Community Climate Model (WACCM) data in the range between 100 and 0.1 hPa from 2005 to 2020 have been analyzed with a focus on the temperature semi-annual oscillations (SAO). Significant SAO of temperature is prominent in the tropical region around 1–3 hPa, which is consistent with previous studies. We also found significant SAO in the northern hemisphere (NH) high latitudes between 8 and 0.3 hPa and southern hemisphere (SH) high latitudes between 0.5 and 0.1 hPa, which has been of less concern in previous studies. The thermal budget based on MERRA2 and simulations is used to explain the mechanism of SAO in the middle atmosphere. The significant SAO in the northern polar region is mainly related to a combination of dynamical and radiative processes. In the SH high latitudes of the lower mesosphere, the first temperature peak in July is mainly due to dynamical processes while the second temperature peak in December is mainly due to radiative processes. Various features are present in the SH and NH high latitude SAO in the lower mesosphere. Furthermore, we performed model simulations with and without SAO in sea surface temperatures (SST-SAO) to study the connection between SST and temperature SAO. WACCM6 results indicate that the SAO in the middle atmosphere is partially affected by the existence of an SST-SAO.

Description: Mingantu Spectral Radioheliograph (MUSER), is an aperture-synthesis imaging telescope, dedicated to observing the Sun, operating on multiple frequencies in the dm to cm range. MUSER is located in Mingantu Town, Inner Mongolia of China, about 400 km northwest of Beijing. MUSER is composed of two arrays of 40 4.5m antennas covering 400MHz -2 GHz, and 60 2m antennas covering 2 - 15 GHz including outdoor devices with antennas, LNBs, and indoor devices including receivers, correlators, etc. In the period of 2014-2019, about 94 solar radio burst events have been registered by MUSER. During the rising phase of the 25th solar cycle, MUSER also records some new events. The project to extend MUSER to the 40 - 400 MHz frequency regime with 224 log-periodic dipole antennas is under construction. The construction of a new 3-site Interplanetary Scintillation (IPS) telescope with the main site having three 140 m by 40m cylinder antennas at MUSER site and 2 sub-sites having 30 m parabolic antennas about 200 km apart has been approved and is under construction. All these are due to complete within a couple of years. We present the recent progress of the solar radio spectroscopy-imaging results from these facilities, including near-future developments and upgrades, as well as the progress of the IPS telescopes under construction in China. The MUSER and IPS telescopes at Mingantu Observing Station, National Space Science Center of the Chinese Academy of Sciences will play important role in solar and heliospheric physics.

Description: In view of the monitoring of the spatial distribution, linkage and temporal evolution of geophysical hazard risk areas, we proposed to use ground stability change monitoring and numerical prediction methods to carry out relevant research. We took CORS network as the control, integrates multi-source data such as hydrometeorology, obtained the regional geometric and physical deformation field model by inversion, and further constructed the law criterion of ground stability criterion, so as to realize the monitoring and numerical prediction of ground stability changes. By interpreting the occurrence place and time, spatial distribution and temporal evolution of the phenomenon of reduced ground stability, the spatial distribution, linkage and temporal evolution law of geological disaster risk areas were revealed, and an application pilot was carried out in western Yunnan province. It was found that the monitoring and numerical prediction methods of ground stability changes using CORS network could effectively grasp the distribution dynamics, linkage relationship and time evolution law of hazard areas, and could provide scientific basis for geological hazard risk assessment, control of hidden danger points and risk areas, disaster preparation process and disaster formation law cognition.

Description: The impacts of the Arctic stratospheric polar vortex (SPV) changes on wintertime frontogenesis in the northern middle latitudes are analyzed. Both composite analysis and model simulations reveal that the intensity and frequency of frontogenesis over Siberia, the Mediterranean and southern North Atlantic during weak SPV years are significantly larger than those during strong SPV years, while the frontogenesis over the northern parts of the North Atlantic and North Pacific Oceans are weaker and less occur during weak SPV years. These features are more noticeable in middle January and February. The contributions of resultant deformation changes to frontogenesis intensity changes over most regions of the middle latitudes are larger than those of horizontal divergence changes, and the contribution of stretching deformation and shearing deformation is almost the same with each other. The changes in frontogenesis intensity are attributed to changes in tropospheric circulation and temperature gradient associated with SPV changes. Potential vorticity (PV) anomalies in the upper troposphere and lower stratosphere (UTLS) caused by the weakened and shifted SPV towards Siberia lead to tropospheric cyclonic flows, favoring more cold-air mass transport towards mid-latitude Siberia. Meanwhile, more high-PV air towards Siberia results in steeper tropospheric isentropes during weak SPV years. Consequently, both temperature gradient and frontogenesis over Siberia are enhanced. More southward transport of cold-air mass due to the equatorward shift of the polar jet stream induced by weak SPV enhances frontogenesis over the southern North Atlantic.

Description: Based on the data of Mingantu Spectral Radioheliograph (MUSER) at 0.4-2.0GHz, the EUV images of the Atmospheric Imaging Assembly (AIA) and the magnetic field data of Helioseismic Magnetic Imager (HMI), we carried out a detailed study of solar bursts with a fan-spine structure that occurred on December 17, 2014. The results show that during the low active level of the active region, there are usually two radio sources, one is around zero point of the fan-spine structure and the other is related to the spine. However, when the M7.8 flare occurred, the location of the radio sources changed dramatically. The high frequency source became one source and moves to the left side of the fan, but the low frequency sources usually displays two sources. The stronger one of which is located on the left side of the fan whereas the weaker one settled at the far end of the spine. These results might shine light on understanding the morphology of three-dimensional magnetic reconnection as well as the acceleration of electrons and the radio emissions caused by them.

Description: A catastrophic landslide occurred on 21 July 2020, 30 km from Enshi city, in Mazhe County of Hubei province, China. In this paper, we aimed to investigate the kinematic evolution and volumetric change related to this landslide using multi-source remote sensing measurements from synthetic aperture radar (SAR) and optical data. C-band Sentinel-1 and X-band TerraSAR-X SAR data are analyzed using several multi-temporal interferometry (MTI) time-series techniques including Persistent Scatterer Interferometry (PSI), Small Baseline subset (SBAS), and Combined eigenvalue maximum likelihood Phase Linking (CPL). The spatial pattern of surface deformation resulting from the interferometric analysis is then statistically analyzed to retrieve the pre-failure and post-failure displacements. Co-failure motions are analyzed using an image correlation technique applied to both the Planetscope and Sentinel-2 images. Moreover, 4 pairs of bistatic TerraSAR-X/TanDEM-X (TDX) data are utilized to generate high-precision digital elevation models (DEMs) and estimate the volumetric change related to the main slope failure. The pre-failure ground deformation analysis results suggest that the landslide was already active before the July 2020 failure, with the seasonality and hydraulic diffusivity being characteristics of a slow-moving landslide. Among the three different MTI methods applied, the CPL method results in a greater measurement points (MPs) density than the PSI and SBAS method when estimating the pre-failure movement of the Shaziba landslide. The July 2020 Shaziba disaster is divided into three main parts: (1) slightly horizontal deformation of 0.5–1.5 m within the northern part with ground and house cracks, (2) less collapse in the eastern part with horizontal motions reaching 30 m and (3) a highly eroded western part where vegetation was wholly lost in the main event, resulting in an collapse volume of approximately 4.98 million m3, out of which approximately around 3.4 million m3 was deposited and approximately 1.58 million m3 was washed away into the Qing River. After the failure, the marginal scrap of the main failure body, above crown of landslide and eastern part showed instability with rates of 20–30 mm/yr, suggesting that the failure zone may continue to expand.