ALBERT

Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 125(4), (2020): e2019JC015470, doi:10.1029/2019JC015470.

Description: This study is to quantify the effects of mesoscale eddies on air‐sea heat fluxes and related air‐sea variables in the South China Sea. Using satellite observations of sea surface temperature (SST) and sea surface height anomaly and a high‐resolution air‐sea heat flux product for the 16‐year period from 2000 to 2015, we conducted the composite patterns of air‐sea fluxes and variables associated with anticyclonic eddies (AEs) and cyclonic eddies (CEs). It is found that the SST‐sea surface height correlations over eddies are not always positive. Only 56% of AEs are corresponded with positive SST anomalies (SSTA), that is, SST+ AEs, and 58% of CEs with negative SSTA, that is, SST− CEs. The percentage of these eddies increases with eddy amplitude and shows slight seasonal variations, higher in winter and lower in summer. Composites of SSTA, air‐sea variables, and fluxes are constructed over all eddies, including both SST+ eddies and SST− eddies. All composites show asymmetric patterns, showing that the centers (where the extrema are located) of the fluxes and variables shift westward and poleward (equatorward) relative to the AEs (CEs) cores. Besides, composites of latent heat flux (LHF), sensible heat flux (SHF), and air temperature show monopole patterns, while composites of wind speed and specific humidity show dipole patterns. For SST+ AEs, the coupling strength is 39.6 ± 6.5 W/m2 (7.2 ± 1.7 W/m2) per degree increase of SSTA for LHF (SHF). For SST− CEs, the coupling strength is 39.0 ± 2.0 W/m2 (9.0 ± 0.96 W/m2) per degree decrease of SSTA for LHF (SHF).

Description: This research was conducted while Y. Liu was a visiting graduate student at Woods Hole Oceanographic Institution (WHOI). She sincerely thanks the WHOI Academic Programs Office for hosting her visit and is grateful to the support from China Scholarship Council (CSC). This study was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant XDA19060101), the Key R & D project of Shandong Province (Grant 2019JZZY010102), the Key deployment project of Center for Ocean Mega‐Science, CAS (Grant COMS2019R02), the CAS Program (Grant Y9KY04101L), and the National Natural Science Foundation of China (Grant 41776183 and 41906157). Dr. Xiangze Jin is acknowledged for providing the OAFluxHR analysis and for his programming support and guidance to this study. Heat flux data used in this paper can be downloaded (from https://figshare.com/articles/Eddy‐induced_heat_flux_in_the_South_China_Sea/11949735). AVISO SSH data are downloaded from the website (http://www.aviso.altimetry.fr), OISST from the ftp://eclipse.ncdc.noaa.gov/ site, and OAFluxHR analysis will be available from the project website (http://oaflux.whoi.edu).

Description: 2020-09-16

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hofig, D., Zhang, Y. G., Giosan, L., Leng, Q., Liang, J., Wu, M., Miller, B., & Yang, H. Annually resolved sediments in the classic Clarkia lacustrine deposits (Idaho, USA) during the middle Miocene Climate Optimum. Geology, 49(8), (2021): 916–920, https://doi.org/10.1130/G48901.1.

Description: The world-renowned Miocene Clarkia paleolake in northern Idaho (USA) is closely associated with Columbia River Basalt Group volcanism. The flood basalt dammed a local drainage system to form the paleolake, which preserved a plant fossil Lagerstätte in its deposits. However, the precise age and temporal duration of the lake remain unsettled. We present the first unequivocal U-Pb zircon ages from interbedded volcanic ashes at the P-33 type location, constraining the deposition to 15.78 ± 0.039 Ma. Using micro–X-ray fluorescence and petrographic and spectral analyses, we establish the annual characteristics of laminations throughout the stratigraphic profile using the distribution of elemental ratios, mineral assemblages, and grain-size structures, as well as organic and fossil contents. Consequently, the ~7.5-m-thick varved deposit at the type location P-33 represents ~840 yr of deposition, coincident with the end of the main phase of Columbia River Basalt Group eruptions during the Miocene Climate Optimum. The timing and temporal resolution of the deposit offer a unique opportunity to study climate change in unprecedented detail during global warming associated with carbon-cycle perturbations.

Description: This research was supported by U.S. National Science Foundation (NSF) grants EAR-1806015 to Zhang and EAR-1804511 to Yang and Leng. Zircon U-Pb analyses were made possible by the NSF-Major Research Instrumentation grant OCE-1626244 and the Texas A&M Research Development Fund award to Miller. We are grateful to the Kienbaum family for providing access to their private property to sample the P-33 site, and to Kunguang Yang from China University of Geosciences at Wuhan for the LA-ICP-MS analysis.

Description: With the completion of Chinese BeiDou Navigation Satellite System (BDS), the world has begun to enjoy the Positioning, Navigation, and Timing (PNT) services of four Global Navigation Satellite Systems (GNSS). In order to improve the GNSS performance and expand its applications, Low Earth Orbit (LEO) Enhanced Global Navigation Satellite System (LeGNSS) is being vigorously advocated. Combined with high-, medium-, and low- earth orbit satellites, it can improve GNSS performance in terms of orbit determination, Precise Point Positioning (PPP) convergence time, etc. This paper comprehensively reviews the current status of LeGNSS, focusing on analyzing its advantages and challenges for precise orbit and clock determination, PPP convergence, earth rotation parameter estimation, and global ionosphere modeling. Thanks to the fast geometric change brought by LEO satellites, LeGNSS is expected to fundamentally solve the problem of the long convergence time of PPP without any augmentation. The convergence time can be shortened within 1 minute if appropriate LEO constellations are deployed. However, there are still some issues to overcome, such as the optimization of LEO constellation as well as the real time LEO precise orbit and clock determination.

Description: To solve the problem that integer ambiguity between middle-range reference stations in BDS is difficult to be fixed correctly due to the influence of ionospheric delay error and tropospheric delay error, an algorithm of triple-frequency integer ambiguity resolution between middle-range BDS reference stations was proposed. Firstly, the frequency observations of B2 and B3 were used to determine B2-B3 extra-wide-lane integer ambiguity. Then, B1-B3 wide-lane integer ambiguity was solved by using the closer characteristic of ionospheric delay error between B2-B3 extra-wide-lane and B1-B3 wide-lane combination observation, and B1-B2 wide-lane integer ambiguity can be fixed according to the linear relationship of triple-frequency integer ambiguity. Furthermore, B1-B3 and B1-B2 ionosphere-free combination observation and the decomposable characteristic of the corresponding integer ambiguity were used to estimate narrow-lane integer ambiguity and relative zenith tropospheric delay error, and then narrow-lane integer ambiguity can be finally fixed by search mode. This algorithm is tested by the measured triple-frequency data of BDS CORS network. The results show that triple-frequency carrier phase integer ambiguity between middle-range BDS reference stations can be fixed accurately and effectively with the method. © 2021, Editorial Board of Journal of CUMT. All right reserved. Search Sources Lists SciVal ALBERT Telegrafenberg Holdings (Opens new window) Alerts Document details - The algorithm of triple-frequency integer ambiguity resolution between middle-range BDS reference stations Back to results Previous 3of20 Next SFX Get it!(opens in a new window)|Entitled full text| Zhongguo Kuangye Daxue Xuebao/Journal of China University of Mining and TechnologyVolume 50, Issue 2, Pages 396 - 403March 2021 Document type Article Source type Journal ISSN 10001964 The algorithm of triple-frequency integer ambiguity resolution between middle-range BDS reference stations[BDS中距离参考站三频整周模糊度确定方法] a , a, a, b, a To solve the problem that integer ambiguity between middle-range reference stations in BDS is difficult to be fixed correctly due to the influence of ionospheric delay error and tropospheric delay error, an algorithm of triple-frequency integer ambiguity resolution between middle-range BDS reference stations was proposed. Firstly, the frequency observations of B2 and B3 were used to determine B2-B3 extra-wide-lane integer ambiguity. Then, B1-B3 wide-lane integer ambiguity was solved by using the closer characteristic of ionospheric delay error between B2-B3 extra-wide-lane and B1-B3 wide-lane combination observation, and B1-B2 wide-lane integer ambiguity can be fixed according to the linear relationship of triple-frequency integer ambiguity. Furthermore, B1-B3 and B1-B2 ionosphere-free combination observation and the decomposable characteristic of the corresponding integer ambiguity were used to estimate narrow-lane integer ambiguity and relative zenith tropospheric delay error, and then narrow-lane integer ambiguity can be finally fixed by search mode. This algorithm is tested by the measured triple-frequency data of BDS CORS network. The results show that triple-frequency carrier phase integer ambiguity between middle-range BDS reference stations can be fixed accurately and effectively with the method. © 2021, Editorial Board of Journal of CUMT. All right reserved.

Description: The terrestrial and celestial reference frames (TRF and CRF) linked by the Earth Orientation Parameters (EOP) serve as the foundation in geodesy. The reference frames and EOP are determined by combining four space geodetic techniques, including Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), Global Navigation Satellite Systems (GNSS), and DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite). Currently the combination is performed either on the parameter or on the normal equation level. In contrast, a combination on the observation level allows fully consistent modeling and parameterization, and thus provides the TRF, CRF, and EOP with the highest consistency, precision, and reliability. In this study, we present preliminary results of the multi-technique integrated processing, including GNSS, VLBI, and SLR, using the upgraded Positioning And Navigation Data Analyst (PANDA) software which can process the three techniques in combination on the observation level. We investigate the impact of global ties, that is, EOP, local ties, and tropospheric ties, with the focus on handling the systematic tie biases automatically. We demonstrate the contributions of the different techniques on the reference frames and EOP. The integrated solution is dominated by the huge number of globally distributed GNSS observations. The VLBI observations contribute to the determination of the full set of EOP and the TRF network scale parameter, whereas the SLR observations contribute to the determination of the network scale and the geocenter. By combining the three techniques, the results outperform any single-technique solution in terms of precision and reliability.

Description: Spectroscopic measurements of soil samples are reliable because they are highly repeatable and reproducible. They characterise the samples' mineral–organic composition. Estimates of concentrations of soil constituents are inevitably less precise than estimates obtained conventionally by chemical analysis. But the cost of each spectroscopic estimate is at most one-tenth of the cost of a chemical determination. Spectroscopy is cost-effective when we need many data, despite the costs and errors of calibration. Soil spectroscopists understand the risks of over-fitting models to highly dimensional multivariate spectra and have command of the mathematical and statistical methods to avoid them. Machine learning has fast become an algorithmic alternative to statistical analysis for estimating concentrations of soil constituents from reflectance spectra. As with any modelling, we need judicious implementation of machine learning as it also carries the risk of over-fitting predictions to irrelevant elements of the spectra. To use the methods confidently, we need to validate the outcomes with appropriately sampled, independent data sets. Not all machine learning should be considered ‘black boxes’. Their interpretability depends on the algorithm, and some are highly interpretable and explainable. Some are difficult to interpret because of complex transformations or their huge and complicated network of parameters. But there is rapidly advancing research on explainable machine learning, and these methods are finding applications in soil science and spectroscopy. In many parts of the world, soil and environmental scientists recognise the merits of soil spectroscopy. They are building spectral libraries on which they can draw to localise the modelling and derive soil information for new projects within their domains. We hope our article gives readers a more balanced and optimistic perspective of soil spectroscopy and its future.

Description: Very Long Baseline Interferometry (VLBI) intensive (INT) sessions are critical for the rapid determination and densification of Universal Time 1-Coordinate Universal Time (UT1-UTC), which plays an important role in satellite geodesy and space exploration missions and is not predictable over longer time scales. Due to the limited observation geometry of INT sessions with two to three stations observing about 1 hr, tropospheric gradients cannot be estimated, which degrades the UT1-UTC precision. We investigate the impact of tropospheric ties at Global Navigation Satellite Systems (GNSSs) and VLBI co-located stations in INT sessions from 2001 to 2021. VLBI and GNSS observations are combined on the observation level. The results are evaluated by using both UT1-UTC and Length of Day (LOD) from consecutive sessions. We demonstrate a better agreement of 10%–30% when comparing the derived LOD to GNSS LOD for INT1, INT2, and VGOS-2 sessions; whereas, the agreement is not improved when directly comparing UT1-UTC to the IERS Earth Orientation Parameters (EOPs) product, potentially because INT sessions also contribute to IERS EOP products. The major impact comes from tropospheric gradient ties, whereas applying zenith delay ties does not improve or even deteriorate UT1-UTC agreement. Gradient ties also introduce systematic biases in UT1-UTC by around −3 to −5 μs, except for the Russian INT sessions. Regression analysis shows that the east gradient introduces systematic effects in UT1-UTC for sessions involving Germany and USA (Hawaii), whereas for Germany–Japan and Russian sessions, the north gradient also contributes systematically.