ALBERT

Description: Snow albedo is an essential factor in the land surface energy balance and the water cycle. It is usually parameterized as functions of snow-related variables in land surface models (LSMs). However, comparing with albedo schemes in the CLM and Noah-MP LSMs, the default snow albedo scheme in the widely used Noah LSM shows evident drawbacks in land-atmosphere interactions simulations during an extreme snow process on the complex topographic Tibetan Plateau (TP). We firstly demonstrate that the improved Noah snow albedo scheme includes MODIS albedo products and explicit considers snow depth as an additional factor. It performs well in relation to near-surface meteorological elements estimates during an extreme snow process. Then, we comprehensively evaluate the performance of the improved snow albedo scheme in WRF coupled with Noah LSM in simulating the additional eight heavy snow events on the TP against in-situ observations, MODIS albedo and IMS snow cover products. It reveals that the improved snow albedo scheme significantly outperforms the default Noah scheme in relation to air temperature, albedo and sensible heat flux estimates, by alleviating cold bias estimates, albedo overestimates and sensible heat flux underestimates, respectively. This in turn contributes to more accurate reproductions of snow cover. The averaged RMSE relative reductions (and relative increase in correlation coefficients) for air temperature, albedo, sensible heat flux and snow depth reach 27% (5%), 32% (69%), 13% (17%) and 21% (108%) respectively. These results demonstrate the strong potential of the improved snow albedo parameterization scheme for heavy snow events simulations on the TP.

Description: Groundwater storage anomaly (GWSA) can be estimated at larger scales from Gravity Recovery and Climate Experiment (GRACE), or at small scales from groundwater-level (GWL) observations, but hampered by leakage errors and lacking of reliable aquifer storage coefficient (Sc), respectively. Here, we developed a coordinated forward modeling (CoFM) to reconcile each other by reducing spatial mismatch between GRACE-based and in-situ-based spherical harmonics through iteratively updating the Sc, with a hypothetical experiment and a case study in the North China Plain (NCP). The results demonstrate that CoFM, independent of reliable Sc, can confidently estimate GWSA trend at 0.5° grid scale when GWSA is dominated by GWL in GRACE-like hypothetical experiments. Besides, CoFM can reveal the larger (2.4 times) groundwater depletion rate in the piedmont of NCP relative to that in the east-central sub-plain, with updated Sc comparable to that from 34 pumping test data. This study highlights a practical solution for improved GWSA estimates through reconciling GRACE and in-situ data.

Description: Aims. For decades now, researchers have been looking for a way to tie the kinematic and dynamic reference frames. Certain worldwide organizations have looked to using co-location in space, combining various techniques. Given the long list of possible applications of the Global Navigation Satellite System (GNSS), it is worthwhile investigating the connection between the most accurate and stable International Celestial Reference Frame (ICRF) and the Earth-centered Celestial Inertial reference frame (ECI) used in GNSS data processing. Methods. We simulated phase-referencing observations of GNSS satellites and nearby radio source calibrators to realize the connection between the two celestial reference frames. We designed two schemes for observation plans. One scheme is to select the satellite target when it can be observed by the greatest number of stations in order to obtain high-precision positioning. During each scan, we employ four regional networks to simultaneously track four chosen satellites. The alternative scheme is to observe satellite orbits of as many satellites as possible on different daily observations. In addition, to test the two schemes, we used Monte Carlo methods to generate 1000 groups of random errors in the simulation. Results. Finally, we estimate the right ascension and declination offsets (∆α, ∆δ) of GNSS satellites in the ICRF, and then derive frame tie parameters based on those results: three global rotation angles (A1, A2, A3). The celestial angular offset results assessed from the former scheme show that this scheme leads to high precision of namely 1 mas, while the parameters of the frame tie determined from the second scheme can achieve an improved precision of better than 1.3 µas.

Description: The Tibetan Plateau (TP), the Iranian Plateau (IP), and the Mongolian Plateau (MP) belong to High Asia, their synergy thermal forcing plays a crucial role in Asian monsoon systems and downstream climate. Therefore, to better understand the turbulent heat exchange between land and air and its climatic effects over the three Plateaus, the applicability of the sensible heat flux (SH), the dominant component of the surface heat source and one of the essential factors affecting the Asian monsoon, should be evaluated. In this study, six widely used reanalysis datasets (ERA5, ERA5-Land, CFSR, JRA55, MERRA2, GLDAS) are selected and the monthly reanalyzed SH is assessed against the in-situ observations. The statistical results show that ERA5-Land and JRA55 perform better with low bias and root mean square error as well as a relatively high correlation coefficient, while CFSR has good consistency with the observations under the alpine meadow. In addition, spatial patterns of annual SH among the six datasets are compared. Except for JRA55 and CFSR, other datasets reveal that SH is higher over the northern and western TP than the eastern, a higher SH occurs over the southern MP, and a homogeneous pattern presents over the IP. In general, ERA5-Land has reliable performance, which is suggested to be used in the analysis and simulation of the connection between SH over High Asia and Asian monsoon variability.

Description: Large earthquakes are usually followed by decaying aftershocks. In some cases, a large earthquake is followed by even larger earthquakes. To estimate seismic hazards of earthquake sequence, it’s necessary to make sure whether the mainshock has already happened. There is no effective method yet to distinguish foreshocks from aftershocks. However, statistical analysis may tell us some useful clues. Since 2010, 35 MS ≥ 6.0 earthquakes have occurred in Chinese mainland, of which 6 MS ≥ 6.0 earthquakes have foreshocks with magnitude larger than 5. Based on foreshock traffic light system (Gulia and Wiemer, 2019), b-positive (van der Elst, 2021) and envelope method (Lippiello et al., 2021), we explored the temporal characteristics of b-value in the Gutenberg–Richter law and the envelope of foreshocks with MS ≥ 5.0 by using catalog and waveform of 6 MS ≥ 6.0 earthquake sequences and tried to propose a real-time foreshock classification method. The preliminary studies show that the temporal variation and the envelope may be useful to recognize foreshocks. For example, the evolution of foreshock sequence of 2019 Yangbi MS 6.4 earthquake can be divided into 3 periods. In the first and second period, the foreshock sequence varied like common aftershock sequence, but the seismicity rate unusually accelerated preceding the mainshock. And the study of waveform of MS ≥ 5.0 foreshocks before Yangbi MS 6.4 earthquake shows that the envelope presents an atypical sawtooth profile and the corresponding β-value is smaller than 0.4 which is much lower than the normal value.

Description: A correction to this paper has been published: 10.1140/epjc/s10052-021-09344-w

Description: The results of a search for gluino and squark pair production with the pairs decaying via the lightest charginos into a final state consisting of two W bosons, the lightest neutralinos ($$ilde{chi }^0_1$$ χ ~ 1 0 ), and quarks, are presented: the signal is characterised by the presence of a single charged lepton ($$e^{pm }$$ e ± or $$mu ^{pm }$$ μ ± ) from a W boson decay, jets, and missing transverse momentum. The analysis is performed using 139 fb$$^{-1}$$ - 1 of proton–proton collision data taken at a centre-of-mass energy $$sqrt{s}=13$$ s = 13   delivered by the Large Hadron Collider and recorded by the ATLAS experiment. No statistically significant excess of events above the Standard Model expectation is found. Limits are set on the direct production of squarks and gluinos in simplified models. Masses of gluino (squark) up to 2.2  (1.4 ) are excluded at 95% confidence level for a light $$ilde{chi }^0_1$$ χ ~ 1 0 .