ALBERT

Description: Tipping elements are components of the Earth system that may shift abruptly and irreversibly from one state to another at specific thresholds. It is not well understood to what degree tipping of one system can influence other regions or tipping elements. Here, we propose a climate network approach to analyse the global impacts of a prominent tipping element, the Amazon Rainforest Area (ARA). We find that the ARA exhibits strong correlations with regions such as the Tibetan Plateau (TP) and West Antarctic ice sheet. Models show that the identified teleconnection propagation path between the ARA and the TP is robust under climate change. In addition, we detect that TP snow cover extent has been losing stability since 2008. We further uncover that various climate extremes between the ARA and the TP are synchronized under climate change. Our framework highlights that tipping elements can be linked and also the potential predictability of cascading tipping dynamics.

Description: Evaluating the embodied environmental impact of solar photovoltaic (PV) technology has been an important topic in addressing the sustainable development of renewable energy. While monetization of environmental externality is a remaining issue, which should be carried out in order to allow for an easy-to-understand comparison between direct economic and external cost. In this study, the environmental impact of solar PV power is monetized through conversion factors between midpoint and endpoint categories of life cycle analysis and the monetization weighting factor. Then, the power generation capacity and generation life of PV and coal-fired power plants are assumed to be consistent in order to compare the total cost of PV and coal-fired power generation. Results show that the cost of PV technology is higher than coal-fired in 2026 to 2030, taking into account environmental external costs and production costs. However, by 2030, the total cost of coal-fired power will be higher than that of solar PV. The life span cost per kWh is $3.55 for solar PV and $116.25 for coal-fired power. Although solar PV power seems more environmentally effective than coal-fired power in the life span, our results reveal the high environmental external cost of producing solar photovoltaic modules, which reminds us to pay more attention to the environmental impact when conducting cost-benefit analysis of renewable technologies. Without incorporating the environmental cost, the real cost of renewable technology will be underestimated.

Description: The second national pollution source survey showed that agricultural non-point source pollution (ANP) has become one of the main causes of water environment deterioration in Guangdong Province. It is important to clarify the ANP status in the province for the prevention and control of water pollution and the construction of rural revitalization. The improved export coefficient method was used to analyze the annual ANP loads and their spatial and temporal variation characteristics in Guangdong Province from 2009 to 2019. The seasonal and monthly pollution loads of ANP were also evaluated with consideration of monthly differences in fertilizer application, precipitation, livestock, and aquaculture. The impact of ANP on the water environment was evaluated by the unit area load coefficient method, and the main sources of ANP were explored. The results indicate that (i) from 2009 to 2019, the total nitrogen load in Guangdong province showed a decreasing trend and the total phosphorus load showed a rising trend with spring and summer being the peak seasons of pollution emissions in a year; (ii) The total nitrogen load trended decreasing in 76.2% of the cities and the total phosphorus load trended increasing in 61.9% of the cities; (iii) in general, the environmental damage caused by agricultural nitrogen and phosphorus loads in western Guangdong was more serious than that in Pearl River Delta, northern and eastern Guangdong; and (iv)the contribution rate of pollution source to nitrogen and phosphorus pollution loads from high to low is livestock and poultry breeding, planting and aquaculture.

Description: On November 23〈sup〉rd〈/sup〉 2022, a M〈sub〉W〈/sub〉 6.0 earthquake occurred in direct vicinity of the M〈sub〉W〈/sub〉 7.1 Düzce earthquake that ruptured a portion of the North Anatolian Fault in 1999. The M〈sub〉w〈/sub〉 6.0 event was attributed to a small fault portion of the Karadere segment that did not rupture during the 1999 sequence. We analyze the spatio-temporal evolution of the M〈sub〉W〈/sub〉 6.0 Gölyaka-Düzce seismic sequence at various scales and resolve the source properties of the mainshock. Modelling the decade-long evolution of background seismicity of the Karadere Fault employing an Epistemic Type Aftershock Sequence model shows that this fault was almost seismically inactive before 1999, while a progressive increase in seismic activity is observed from 2000 onwards. A newly generated high-resolution seismicity catalog from 1 month before the mainshock until six days after created using Artificial Intelligence-aided techniques shows only few events occurring within the rupture area within the previous month, no spatio-temporal localization process and a lack of immediate foreshocks preceding the rupture. The aftershock hypocenter distribution suggests the activation of both the Karadere fault which ruptured in this earthquake as well as the Düzce fault that ruptured in 1999. First results on source parameters and the duration of the first P-wave pulse from the mainshock suggest that the mainshock propagated eastwards in agreement with predictions from a bimaterial interface model. The M〈sub〉W〈/sub〉 6.0 Gölyaka-Düzce represents a good example of an earthquake rupture with damaging potential within a fault zone that is in a relatively early stage of the seismic cycle.

Description: Complex fault geometry can strongly affect earthquake rupture processes and slip sequences. I will first present our recent work on modeling earthquake and slow slip sequences on 3D fault surfaces, with applications to the Yingxiu-Beichuan fault (YBF) which hosted the 2008 Mw 7.9 Wenchuan earthquake in China and the Cascadia subduction zone. In the rate-and-state friction computational framework, earthquake and aseismic slip nucleate and propagate spontaneously under the influence of long-term tectonic loading and heterogeneous frictional properties. In particular, fault dip angle has a primary control on the along-strike segmentation of simulated earthquake and slow slip, in general agreement with observations from YBF and Cascadia. Fault local strike angle on the other hand strongly affects small-scale along-strike variations in the rupture speed and slip rate. Next, I will introduce a newly developed mixed-flux-based discontinuous Galerkin method and its application to simulate fully dynamic ruptures on complex fault geometries. The new method greatly reduces numerical dependence on mesh quality, and can accommodate complex fault properties including geometry, material heterogeneities and multi-physics mechanisms such as off-fault plasticity and thermal pressurization.

Description: The recent Mw 7.4 Madoi, Tibet earthquake provides a valuable opportunity to assess the contribution of the fully operational global BeiDou Navigation Satellite System (BDS-3) and other Global Navigation Satellite Systems (GNSS) in real-time seismic waveform capture. This event was successfully recorded by 111 1-Hz GNSS stations and 16 200-Hz strong motion stations. All GNSS stations are capable of recording BDS, GPS, GLONASS and Galileo observations. The variometric approach has been expanded to process multi-frequency and multi-GNSS data to estimate velocity, and then the coseismic displacements can be obtained by integrating the velocities. The results indicate that the phase-specific inter-frequency clock bias between BDS and GPS has minimal impact on velocity and displacement estimation, and there is no significant accuracy improvement with the help of a third frequency. Although the velocities derived from BDS are more noisy than those from GPS, the accuracy of integrated horizontal displacements for the regional BDS (BDS-2) shows 20% improvement with the RMS value of 0.5 cm. Compared to BDS-2, the seismic waveforms retrieved from BDS-3 shows nearly 50% better accuracy, due to the higher observation quality and stronger satellite geometry, and the performance can be further improved through fusion with multi-GNSS. The GNSS-derived seismic waveforms are consistent with those from accelerometer data. The inversion of the rapid rupture process indicates that BDS can provide a more reliable estimation of the fault slip distribution than GPS, and the performance can be further improved by using the GCRE observations, which will undoubtedly contribute to seismology applications.

Description: The present study classifies regional persistent extreme precipitation events (PEPEs) in North China into two types in accordance with variance contributions of different timescale rainfall variability in boreal summer. For Type 1, PEPEs are dominated by 10-20-day periodicity, and for Type 2 PEPEs are mainly influenced by a 30-60-day mode. Atmospheric circulation anomalies associated with the two types of PEPEs are characterized by a zonal wave train (the EU pattern) in the mid-high latitudes in Type 1 but a meridional wave train (the EAP pattern) in East Asia in Type 2. The common feature of the two types is anomalous southerly on the west edge of the West Pacific Subtropical High (WPSH), which favors anomalous moisture transport into the key region. Additional moisture source for Type 2 is linked to anomalous cross-equatorial flow. Both types of PEPEs result from the combined effect of intraseasonal oscillations in both the mid-high latitudes and the tropics. The impact of ENSO on the two types of PEPEs is investigated. While a La Niña and a neutral SST condition in the preceding winter favor for the occurrence of PEPEs, their subsequent transition in central and eastern equatorial Pacific will determine which of the two types of PEPEs is pronounced.

Description: The effect of tropical precipitation on the inverse change in the entrance and exit of the tropical easterly jet (TEJ) is studied. The TEJ's entrance and exit are over the northwest Pacific Ocean and equatorial Africa, inversely varying from July to September. When the entrance of the TEJ is weaker-than-normal, the exit is stronger-than-normal, and vice versa. Observed data show that a west-east dipole precipitation pattern located in the Maritime Continent (MC) and tropical Pacific (TP) has a distinct influence on such inverse variation of the TEJ. A series of numerical experiments are carried out based on the linear baroclinic model, qualitatively exploring the independent effects of MC and TP precipitation anomalies. The results show that the heat source over the MC can induce a Kelvin wave propagating eastward in the upper troposphere, resulting in the weakening of the TEJ entrance. The heat sink over the TP generates a Rossby wave response, forming a pair of cyclones in the troposphere over the equatorial western Pacific, and the westerly anomaly in the middle weakens the TEJ's entrance; meanwhile, a Kelvin wave propagating eastward in the upper troposphere between 120°W and 70°E, which is caused by the heat sink over the TP strengthens the exit of the TEJ. There is a reverse phase change in the inlet and exit regions of the jet stream as a result. It’s shows that the west-east dipole precipitation pattern in the MC and TP may be related to La Niña-like SST anomalies in synchronous summer.

Description: As is known to all that the North China Plain (NCP) has been plagued by severe water shortages and land subsidence. It is of great practical importance to investigate whether the recharge water provided by the South-North Water Diversion Project (SNWDP) for NCP can effectively alleviate the problems such as land subsidence in the area. In our study, we analyzed the equivalent water height and land deformation of NCP based on GRACE and GRACE-FO data for the past decade and GNSS observations for the same period, and found that water recharge well mitigated the deficiency of land water storage, but the vertical motion images reflected by GNSS data showed that the rate of land subsidence was not slowed down by the increase of water storage. The results imply that the release of water from the weakly permeable layer is delayed due to previous over-exploitation of groundwater, while the short-term supply of surface water has little effect on replenishing groundwater.

Description: For the precise orbit determination (POD) of global navigation satellite systems (GNSS) constellation, it is very difficult to precisely model the solar radiation pressure (SRP) force acting on GNSS satellites. For GPS satellites, the ECOM model developed by the Center for Orbit Determination in Europe has been utilized by most of International GNSS Service (IGS) analysis centers. However, it should be adapted and optimized to the characteristics of satellites of each GNSS system or even individual satellites. It was extended to the ECOM2 model for GLONASS satellites and then for Galileo satellites by employing a box–wing model. Since November 2020, the third generation of the BeiDou satellite system (BDS-3) has been in its full operation and there are about 200 globally distributed IGS ground stations tracking BDS-3 signals, which creates a great potential to evaluate and optimize its SRP modeling. From the POD processing carried out in this study, we found significant fluctuations of up to 20 cm in overlapping orbit differences for satellites over eclipses in the radial direction and of about 20 and 50 cm in the cross and along directions for ECOM2 and ECOM models. Then, based on numerical analyses we demonstrate that the fourth- and sixth-order sine terms in the Sun direction can significantly reduce the overlapping orbit differences of ECOM. Therefore, an adapted SRP model by adding the fourth- and sixth-order sine periodical terms in the Sun direction to the ECOM model is presented. The adapted model is then validated for BDS-3 POD and orbit prediction. Results show that fluctuations in the amplitude of overlapping estimated orbits using ECOM models are reduced from 20 to 〈 10 cm in the radial-track component and satellite laser ranging residuals are reduced to half by the adapted SRP model. For the predicted BDS-3 satellite orbits, the RMS values over deep eclipses can be improved from about 7, 14 and 26 cm to about 3, 5 and 12 cm, in the radial, cross and along directions, respectively, compared to the ECOM model.