Assessment of International GNSS Service Global Ionosphere Map products over China region based on measurements from the Crustal Movement Observation Network of China

The global ionosphere maps(GIM)provided by the International GNSS Service(IGS)are extensively utilized for ionospheric morphology monitoring,scientific research,and practical application.Assessing the credibility of GIM products in data-sparse regions is of paramount importance.In this study,measurements from the Crustal Movement Observation Network of China(CMONOC)are leveraged to evaluate the suitability of IGS-GIM products over China region in 2013-2014.The indices of mean error(ME),root mean square error(RMSE),and normalized RMSE(NRMSE)are then utilized to quantify the accuracy of IGS-GIM products.Results revealed distinct local time and latitudinal dependencies in IGS-GIM errors,with substantially high errors at nighttime(NRMSE:39%)and above 40°latitude(NRMSE:49%).Seasonal differences also emerged,with larger equinoctial deviations(NRMSE:33.5%)compared with summer(20%).A preliminary analysis implied that the irregular assimilation of sparse IGS observations,compounded by China’s distinct geomagnetic topology,may manifest as error variations.These results suggest that modeling based solely on IGS-GIM observations engenders inadequate representations across China and that a thorough examination would proffer the necessary foundation for advancing regional total electron content(TEC)constructions.

Current situation and trend of marine data buoy and monitoring network technology of China

Marine data buoy can provide a long-term, continuous, real-time, reliable data of ocean observation in a variety of complex marine environment. It is one of the most reliable, most effective and important means of ocean monitoring technology. In this paper, the classification, main theory and technology system of marine data buoy are summarized. The typical technological breakthrough of the development of marine data buoy in recent years is summarized. The composition and application of marine monitoring network in China was introduced, and the gap between the technology of China＇s marine data buoy and the international advanced countries is compared.Combined on the situation and demand of China＇s current situation and needs, the development trend of marine data buoy and buoy monitoring network are expected.

Earthquake Electromagnetic Precursor Anomalies Detected by a New Ground-based Observation Network

It is a debated topic if there are any observable precursor anomalies prior to the earthquake(EQ hereafter)and if the stronger EQ can be successfully predicted.During last few decades quite a lot of observable electromagnetic(EM)precursors were published by using techniques equipped in either satellites or on ground-based stations.But there are only a few cases that the shortterm precursor anomalies of EM field before earthquakes were observed by using alternate EM fields on ground.This paper will present a new EM observation network built in recent years and show a new finding of EM field with the variation of a one-year cycle observed using the network.As an example,the short-term precursor anomalies of apparent resistivity before the Yangbi EQ(Ms 5.1)occurred on March 27,2017 in Yunnan Province will be studied.The observed anomalous phenomena indicate that the anomaly before the EQ can be captured only if reasonable effective methods including sophisticated analytical techniques are used,and it is believed that continuously observed data on the fixed observation network for a long time is an effective means for studying anomalies that appeared before earthquakes.This network can also play an important role in studying the EM environment from space.

Establishing a Ultraviolet Radiation Observational Network and Enhancing the Study on Ultraviolet Radiation

On the basis of analyzing observational data on solar radiation, meteorological parameters, and total ozone amount for the period of January 1990 to December 1991 in the Beijing area, an empirical calculation method for ultraviolet radiation (UV) in clear sky is obtained. The results show that the calculated values agree well with the observed, with maximum relative bias of 6.2% and mean relative bias for 24 months of 1.9%. Good results are also obtained when this method is applied in Guangzhou and Mohe districts. The long-term variation of UV radiation in clear sky over the Beijing area from 1979 to 1998 is calculated, and the UV variation trends and causes are discussed: direct and indirect UV energy absorption by increasing pollutants in the troposphere may have caused the UV decrease in clear sky in the last 20 years. With the enhancement of people's quality of life and awareness of health, it will be valuable and practical to provid UV forecasts for typical cities and rural areas. So, we should develop and enhance UV study in systematic monitoring, forecasting, and developing a good and feasible method for UV radiation reporting in China, especially for big cities.

Russian section of GGOS： Network status and progress

Establishment of the Russian section in the framework of Global Geodetic Observing System （GGOS） is under progress. New components of ＂Quasar＂ network observatories, which are included into GGOS global network as core stations, are presented. Recent developments include： two new generation radio telescopes with 13 m antennas at Badary and Zelenchukskaya observatories, water vapor radiometers installed at all observatories and software correlator at the Institute of Applied Astronomy. New and potential developments within other networks belonging to different agencies are also considered in the context of widening of Russian section activity in GGOS project, The paper gives a short overview of status, new components and plans, concerning 5 sub-networks of Federal Agency of Scientific Organi- zations, Roskosmos, Rosstandard, and Rosreestr. Short overview of the plans on creating Data and Analysis Distributed Center is also ~iven.

China's Observation Network For Earth's Crust Movement Now Operational

An observation network focusing on earthquakes wascompleted one year aheadof schedule and put into operationrecently. According to scientists, this135-million-yuan (U.S.$16.3million) project could also be usedfor geodetic surveying, ionosphereand sea-level observations,

Fences and hydropower:Important but overlooked Human Footprint

Human activities have impacted 77%of the terrestrial ecosystems(excluding Antarctica),and the remaining areas are becoming increasingly endangered.Mapping spatiotemporal dynamics of Human Footprint has been used to evaluate the cumulative interference on terrestrial environments globally.However,fences and hydropower,two widespread and rapidly expanding infrastructures,have not been considered regarding Human Footprint,despite their complicated and extensive effects on ecosystem functioning and species survival.Previous work has proved that fences increase habitat fragmentation,disrupt migratory routes,inadvertently trap and kill wildlife,and hinder genetic exchange.Hydropower construction also caused habitat loss,fragmentation,and degradation.These impacts have received global concern,but fences around the world are difficult to be detected due to the limitations of current cartographic technologies.Furthermore,the effect of hydropower on the terrestrial environment has been underestimated,making the research on this topic at a global scale still in its infancy.Therefore,building an observation network of global fences and hydropower is a necessary step to move forward in the assessment of the impact of human activities on our planet,but also to better provide scientific support for policy-making regarding global biodiversity conservation,the identification of protected areas,and the prioritization of ecological restoration areas.

Networking Observation and Applications of Chinese Ocean Satellites

This paper presents the networking observation capabilities of Chinese ocean satellites and their diverse applications in ocean disaster prevention,ecological monitoring,and resource development.Since the inaugural launch in 2002,China has achieved substantial advancements in ocean satellite technology,forming an observation system composed of the HY-1,HY-2,and HY-3 series satellites.These satellites are integral to global ocean environmental monitoring due to their high resolution,extensive coverage,and frequent observations.Looking forward,China aims to further enhance and expand its ocean satellite capabilities through ongoing projects to support global environmental protection and sustainable development.

Strong motion observations and recordings from the great Wenchuan Earthquake

The National Strong Motion Observation Network System （NSMONS） of China is briefly introduced in this paper. The NSMONS consists of permanent free-field stations, special observation arrays, mobile observatories and a network management system. During the Wenchuan Earthquake, over 1,400 components of acceleration records were obtained from 460 permanent free-field stations and three arrays for topographical effect and structural response observation in the network system from the main shock, and over 20,000 components of acceleration records from strong aftershocks occurred before August 1, 2008 were also obtained by permanent free-field stations of the NSMONS and 59 mobile instruments quickly deployed after the main shock. The strong motion recordings from the main shock and strong aftershocks are summarized in this paper. In the ground motion recordings, there are over 560 components with peak ground acceleration （PGA） over 10 Gal, the largest being 957.7 Gal. The largest PGA recorded during the aftershock exceeds 300 Gal.

Gravity anomaly before the Leshan M5.0 earthquake?

The North-South Seismic Belt was analyzed using gravity observation data from 2011 to 2015, and the nontidal analysis results show that there was a nonlinear gravity change at both the Chengdu and Guza seismostations one month before the Leshan M5.0 earthquake.

Construction Progress of Chinese Meridian Project PhaseⅡ

The Chinese Meridian Project(CMP)is the Space Environment Ground Based Comprehensive Monitoring Network of China,a national major science and technology infrastructure project.The CMP consists of the Space Environment Monitoring System,Data Communication System,and Science Application System.Its construction has been divided into two steps:the PhaseⅠwas from 2008 to 2012;the PhaseⅡstarted at the end of 2019,expected to be completed at the end of 2023.Beyond 2023,the CMP as a whole will be in operation to make observations.This report introduces the construction progress of CMP PhaseⅡin the past two years,covering the construction progress of both the Data Communication System and the Science Application System.As for the Space Environment Monitoring System,this report mainly gives an introduction to the construction progress of large-scale advanced monitoring equipment,such as,the solar radio telescope,interplanetary scintillation telescope,incoherent scatter radar,high frequency radar,MST radar,and large-aperture Helium Lidar.In addition,this paper presents the construction plan for the next two years and the future outlook as well.

Adaptive neural network observer for proton-exchange membrane fuel cell system

This paper develops an adaptive neural network(NN)observer for proton-exchange membrane fuel cells(PEMFCs).Indeed,information on the oxygen excess ratio(OER)value is crucial to ensure optimal management of the durability and reliability of the PEMFC.The OER indicator is computed from the mass of oxygen and nitrogen inside the PEMFC cathode.Unfortunately,the measurement process of both these masses is difficult and costly.To solve this problem,the design of a PEMFC state observer is attractive.However,the behaviour of the fuel cell system is highly non-linear and its modelling is complex.Due to this constraint,a multilayer perceptron neural network(MLPNN)-based observer is proposed in this paper to estimate the oxygen and nitrogen masses.One notable advantage of the suggested MLPNN observer is that it does not require a database to train the NN.Indeed,the weights of the NN are updated in real time using the output error.In addition,the observer parameters,namely the learning rate and the damping factor,are online adapted using the optimization tools of extremum seeking.Moreover,the proposed observer stability analysis is performed using the Lyapunov theory.The observer performances are validated by simulation under MATLAB®/Simulink®.The supremacy of the proposed adaptive MLPNN observer is highlighted by comparison with a fixed-parameter MLPNN observer and a classical high-gain observer(HGO).The mean rela-tive error value of the excess oxygen rate is considered the performance index,which is equal to 1.01%for an adaptive MLPNN and 3.95%and 9.95%for a fixed MLPNN and HGO,respectively.Finally,a robustness test of the proposed observer with respect to measurement noise is performed.

Representativeness of Four Precipitation Observational Networks of China

Four precipitation observational networks with varied station densities are maintained in China. They are： the Global Climate Observation System （GCOS） Surface Network （GSN）, the national Reference Climate Network （RCN）, the national-Basic Meteorological Network （BMN）, and the national Ordinary Meteorolog- ical Network （OMN）. The GSN, RCN, BMN, and the merged network of RCN and BMN （R＆B） have been widely used in climatology and climate change studies. In this paper, the impact of the usage of different networks on the precipitation climatology of China is evaluated by using the merged dataset of All Station Network （ASN） as a benchmark. The results show that all networks can capture the main features of the country average precipitation and its changing trends. The differences of average annual precipitation of the various networks from that of the ASN are less than 50 mm （≤ 10%）. All networks can successfully detect the rising trend of the average annual precipitation during 1961-2009, with the R＆B exhibiting the best representativeness （only 2.90% relative difference） and the GSN the poorest （39.77%）. As to the change trends of country average monthly precipitation, the networks can be ranked in descending order as R＆B （1.27%）, RCN （2.35%）, BMN （4.17%）, and GSN （7.46%）, and larger relative differences appear from August to November. The networks produce quite consistent spatial patterns of annual precipitation change trends, and all show an increasing trend of precipitation in Northwest and Southeast China, and a decreasing trend in North China, Northeast China, and parts of central China. However, the representativeness of the BMN and R＆B are better in annual and seasonal precipitation trends, in spite of the fact that they are still far from satisfactory. The relative differences of trends in some months and regions even reach more than 50%. The results also show that the representativeness of the RCN for country average precipitation is higher than that of the BMN because the RCN has a more homogeneous distribution of stations .

Coverage Optimization of Field Observation Instrument Networking Based on an Improved ABC Algorithm

The severe conditions of cold and arid areas seriously affect the progress of data collection and analysis for field observation instruments.Therefore,this study adopted the modified artificial bee colony(ABC)algorithm to optimize the coverage of nodes and designed an energy-efficient node coverage optimization method.In the coverage optimization,the coverage rate and the number of working nodes are considered comprehensively,and the fitness value calculation is improved.The experimental results reveal that the modified ABC algorithm has better coverage optimization performance than the original ABC algorithm,genetic algorithm(GA),and particle swarm optimization(PSO)algorithm.

Contribution of the Chinese Meridian Project to space environment research:Highlights and perspectives

The Chinese Meridian Project(CMP)is devoted to establishing a comprehensive ground-based monitoring network for China’s space weather research.CMP is a major national science and technology infrastructure project with the participation of more than 10 research institutions and universities led by the National Space Science Center of the Chinese Academy of Sciences.CMP is planned to be constructed in two phases:CMP phasesⅠandⅡ.The first phase(CMP-Ⅰ)started construction in2008 and completed in 2012,after which it entered the operation stage.The 10-year observation of CMP-Ⅰhas made significant scientific discoveries and achievements in the research fields of the middle and upper atmospheric fluctuations,metal layers in the mesosphere and lower thermosphere,ionospheric disturbances and irregularities,geomagnetic disturbances,and influences of solar activity.The review summarizes the main observations and research achievements,space weather forecast modeling and methods based on CMP-Ⅰover the past 10 years,and presents a future extension perspective along with the construction of CMP-Ⅱ.

Robust Load Frequency Control for Isolated Microgrids Based on Double-loop Compensation

Frequency is an important indicator for the oper-ation of microgrids.However,the randomness and uncertainty of renewable energy and load variability may lead to frequency undulation.So,a robust load frequency control(LFC)is pro-posed for isolated wind-diesel microgrids considering time delay and parameter uncertainty.The control strategy can suppress frequency fuctuation and optimize frequency dynamic response.First,the double compensation loop,including feedforward control and integral sliding mode control(SMC),is devised to provide anti-disturbance compensation for the diesel generator system and ameliorate the frequency stability of independent microgrids.Secondly,a dynamic fuzzy controller,composed of wind speed and load demand,is designed to provide real-time response reference power for doubly fed induction generator systems(DFIGs),which can promote the effective participation of a wind turbine system for frequency regulation.Then,the proportional differential(PD)parameters of a dynamic fuzzy controller and the frequency adjustment compensation of DFIGs can be obtained by using a particle swarm optimization(PSO)algorithm.Thirdly,load demand is an important index of the robust dynamic load frequency control method;the radial basis function(RBF)neural network observer(NNO)based on the LFC model is presented to obtain more accurate load deviations and improve the control precision of LFC.The performance of the proposed LFC method is tested under different operation cases.Index Terms-Load frequency control,microgrid,neural network observer,sliding mode,time delay and parameter uncertainty.