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Retrieving the coseismic displacement in real time is essential when the high-rate Global Navigation Satellite System (GNSS) is used for the real-time earthquake source description. In 2020, the third generation of the BeiDou Global Navigation Satellite System (BDS-3) initiated a real-time precise point positioning service through the B2b signal (PPP-B2b), which provides a new possibility for real-time earthquake source description. In this study, the performance of the PPP-B2b on the real-time retrieval of coseismic displacement was first validated with GNSS observations collected during the 2021 Mw 7.4 Maduo earthquake. Then, the warning magnitude, focal mechanism and fault slip distribution were inverted with the derived PPP-B2b displacement in a simulated real-time model. Our results indicate that the accuracies of the coseismic displacements in the north, east and up components are 0.8 cm, 0.5 cm, and 1.4 cm for the single GPS PPP-B2b, 0.5 cm, 0.6 cm, and 0.9 cm for the single BDS-3 PPP-B2b and 0.4 cm, 0.3 cm, and 0.4 cm for the combined GPS/BDS-3 PPP-B2b, respectively, when compared with the coseismic displacements of the post-processing precise point positioning (PPP). Moreover, the warning magnitude, focal mechanism and fault slip distribution inverted with the PPP-B2b displacements are all in good agreement with those inverted with the PPP displacements. This study highlights the great possibility of the PPP-B2b to be used for earthquake early warning and rapid emergency responses. [ABSTRACT FROM AUTHOR]

The weighted mean temperature (Tm) is a function of atmospheric temperature and vertical humidity profiles. It plays a crucial role in the progress of retrieving water vapor information from the tropospheric delay of GNSS signals. The Tm estimated by the empirical models is always used to convert the zenith wet delay (ZWD) to precipitable water vapor (PWV) in GNSS meteorology. However, these empirical Tm models used trigonometric functions, making it difficult to describe Tm in detail and leading to an obvious accuracy difference with latitude changes. Thus, a global latitude zone augmentation mode was adopted for the empirical Tm models; the augmentation coefficients for each latitude zone were obtained by introducing the measured surface temperature and using the least-squares method. Using the Tm data of 2011–2015 derived from radiosonde, the GPT3 model, UNB3m model, and GWTMD model were augmented and analyzed. The results show that all augmentation models can improve the accuracy of the estimated Tm compared with their corresponding original models, and their levels of improvement are different. The three augmentation models achieved an average RMSE of 2.79 K, 3.47 K, and 3.22 K, which correspond to 22%, 49%, and 8% improvement against the GPT3 model, UNB3m model, and GWTMD model. In addition, the comparisons with the Tm linear formula were carried out and showed the superiority of the augmentation models. [ABSTRACT FROM AUTHOR]

On May 21, 2021, a Mw 7.4 earthquake struck the Maduo County in Qinghai province of China. The earthquake was well recorded by the surrounding high-rate Global Navigation Satellite System (GNSS) stations. In addition to GPS, GLONASS and BDS2 observations, these stations also recorded the latest BDS3 and Galileo observations. The performance of high-rate single-GNSS and fusion of multi-GNSS on warning magnitude calculation, rapid centroid moment tensor inversion and static fault slip inversion are well investigated in this study. The results demonstrate that within a short period of time (5 min), Precise Point Positioning (PPP) displacements of BDS3 alone are better than those of BDS2 alone, while the individual displacement accuracies of BDS3, GPS and Galileo are comparable. When BDS3 and BDS2 data are combined, the combined BDS accuracy is slightly better than that of GPS or Galileo alone. Compared with the single-GNSS displacements, the fusion of GPS + GLONASS + Galileo + BDS3/2 (GREC) can achieve the highest accuracy with standard deviation values of 0.25 cm, 0.22 cm and 0.53 cm in north, east and up components, respectively. For the warning magnitude estimation, BDS3 alone, BDS2 alone, combined BDS3/2, combined GPS + BDS3/2, Galileo alone and GREC all show comparable performance. The results of centroid moment tensor inversion and static fault slip inversion are related to the station distribution. When the same stations are used, the inverted centroid moment tensors and static fault slips of a single GNSS are very similar to the multi-GNSS inversion results, but the multi-GNSS centroid moment tensor series and fault slips appear to be more stable when the observation quality of a single GNSS such as GLONASS, is relatively low. The results obtained in this study imply that GPS, BDS3, Galileo and combined multi-GNSS have the potential to be used for the earthquake early warning and rapid earthquake source modeling. [ABSTRACT FROM AUTHOR]

The impact of solar activity on climate system is spatiotemporally selective and usually more significant on the regional scale. Using statistical methods and solar radio flux (SRF) data, this paper investigates the impact of the solar 11-yr cycle on regional climate of Northeast Asia in recent decades. Significant differences in winter temperature, precipitation, and the atmospheric circulation over Northeast Asia are found between peak and valley solar activity years. In peak years, temperature is higher over vast areas of the Eurasian continent in middle and high latitudes, and prone to producing anomalous high pressure there. Northeast Asia is located to the south of the anomalous high pressure, where the easterlies prevail and transport moisture from the western Pacific Ocean to the inland of East Asia and intensify precipitation there. In valley years, temperature is lower over the Eurasian continent and northern Pacific Ocean in middle and high latitudes, and there maintain anomalous low pressure systems in the two regions. Over the Northeast Asian continent, north winds prevail, which transport cold and dry air mass from the high latitude to Northeast Asia and reduce precipitation there. The correlation coefficient of winter precipitation in Northeast China and SRF reaches 0.4, and is statistically significant at the 99% confidence level based on the Student's t-test. The latent heat flux anomalies over the Pacific Ocean caused by solar cycle could explain the spatial pattern of abnormal winter precipitation of China, suggesting that the solar activity may change the climate of Northeast Asia through air-sea interaction. [ABSTRACT FROM AUTHOR]

We hypothesized that ramie, Boehmeria nivea (a nettle native to Asia), can be used as a high-quality forage to replace alfalfa hay in diets of dairy cows. Accordingly, we aimed to examine the effects of substituting fresh forage ramie for alfalfa (Medicago sativa) hay on production performance, milk composition, and serum parameters of dairy cows. Thirty-two Holstein cows (body weight (BW) = 590 ± 50.6 kg) were randomly divided into four groups of eight cows. The experimental period lasted 10 weeks. The dietary treatments consisted of four proportions of fresh forage ramie (0, 33, 67, and 100%) as a substitute for alfalfa hay (designated as CON, FR33, FR67, and FR100, respectively). On days 69 and 70 of the experimental period, milk and blood samples were collected for analysis. We found no significant differences in the milk yield and milk quality (milk protein percentage, milk fat percentage, and milk lactose percentage) between the treatments. We did find that forage ramie significantly reduced dry matter intake (DMI) and 4% fat-corrected milk (FCM) yield. Meanwhile, no significant differences were detected in serum parameters between the treatments, with the exception of triglyceride (TG) and alanine aminotransferase (ALT). In conclusion, our data indicate that alfalfa hay can be replaced with forage ramie in the diet of Holstein cows in the milk lactation stage, with no negative effects on milk quality and blood parameters. [ABSTRACT FROM AUTHOR]

Over the past three decades, radar altimetry has made a significant contribution to marine gravity field modeling. To improve the accuracy and resolution, we propose a new twin-satellite altimetry. Such a system has several advantages. Among others, it provides (i) twice the number of samples per time epoch, and (ii) information about the cross-track surface gradient with high accuracy because most of the environmental and tidal errors will be common to the simultaneous measurements and therefore cancel out when computing the cross-track gradient computation. We describe a rigorous procedure for the deduction of the sea surface gradient at each altimeter observation point (i.e., not only at the crossovers), from the twin-satellite altimetry system. The precision of the gradient will be slightly affected by orbit errors, instrument drift, and inaccuracies in the geophysical corrections to be applied. We also demonstrate that a 1 mGal accuracy and 1 min resolution marine altimetry gravity field can be obtained if certain conditions are met. To achieve the expected goal, we recommend an orbital configuration, phasing two satellites in 4-s time delay such that the Earth rotation creates a natural baseline between the two satellites, and a 18 kHz SAR altimeter. [ABSTRACT FROM AUTHOR]