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The long-term global distribution study of Aerosol Optical Depth (AOD) has great significance for air pollution control, forest fire prevention and climate studies. The global spatial-temporal distribution and variation of the AOD at 550 nm are analyzed using AOD 550 product of Modis/Aqua during 2003–2021. The AOD 550 is also studied by Empirical Orthogonal Function (EOF) analysis method. The results show that the distribution of AOD 550 has obvious regional and seasonal characteristics, and the interannual variation is distinct. The AOD 550 distribution with latitude/longitude is closely related to the distribution of population and aerosol natural source. The high-AOD 550 areas are mainly distributed in eastern Asia, southeast Asia, south Asia, the Middle East, northwestern Africa, central and western Africa, western waters of Africa and the Amazon region of South America; The AOD 550 seasonal distribution results are JJA > MAM > DJF > SON over globe, SON > DJF > (MAM ≈ JJA) over the southern hemisphere, and MAM > JJA > DJF > SON over the northern hemisphere, respectively. Moreover, the seasonal distribution characteristics varies in different regions especially over ocean and land. The results of interannual variation show an upward trend during 2005–2011, and fluctuates during 2012–2020. The annual mean AOD 550 over the northern hemisphere (0.187–0.207) is significantly higher than that of southern hemisphere (0.110–0.135), while the latter shows an increasing trend (0.0009/year). The EOF analysis results demonstrate the complexity of the AOD 550 global distribution. The annual mean results show the change trends of aerosols in different regions and find some special aerosol events. While the monthly mean results show that aerosols over ocean are mostly dominated by land sources (dust and biomass burning sources), and the ocean transport pattern presents an annual cycle. • The global distribution of Aerosol Optical Depth is studied using MODIS level 3 data from 2003 to 2021. • The seasonal and interannual variations of Aerosol Optical Depth are reported with the global perspective. • The Empirical Orthogonal Function analysis of Aerosol Optical Depth is performed. [ABSTRACT FROM AUTHOR]

The variation trends of the cold-point tropopause (CPT) are presented using radiosonde observations from 77 stations over China during 1979–2014. The latitude regions over China from 18°N to 53°N are divided into 7 latitude zones with every 5° intervals, and the spatial areas of 18°N–53°N, 75°E–135°E are divided into 27 lattices with 5° × 10° grids. The annual-mean values of height-of-CPT (H-CPT) and temperature-of-CPT (T-CPT) are then calculated by all the available samples within each latitude and longitude bin. By using the least squares regression method, it is found that the H-CPT increases with the rate of 273 m/decade, and overall the significant cooling rate of − 0.70 K/decade for the T-CPT over the whole of China. Then, the trends and latitude distribution of H-CPT and T-CPT for each latitude zone are analyzed. The difference of H-CPT among latitude distribution characteristic is reducing year by year, and the difference of T-CPT is enlarging. The H-CPT displays a rising trend between 28°N–53°N latitude region with the positive change rates, and it has decline trend between 18°N–28°N latitude region with the negative change rates. The change rates of T-CPT are negative values for all latitude zones. At last, the nonuniform latitudinal and longitudinal distribution of long-term trends of H-CPT and T-CPT are first presented for each spatial cell. [ABSTRACT FROM AUTHOR]

Existing wireless coal mine environmental monitoring system has large transmissions of redundancy data. Monitoring and treatment of multiple environmental parameters are mutually independent, with low instantaneity and reliability. To solve the above problems, this paper designs the coal mine environmental monitoring system based on multi-agent, taking advantages of the harmony and intelligence of the multi-agent technology. This system designs the environmental monitoring agent from both hardware and software aspects which can cooperate mutually and work harmoniously between each other. Thus, the quantity of transmission of data can be reduced, which optimizes the structure of the coal mine environmental monitoring system. Results of simulation experiments prove that the multi-agent-based coal mine environmental monitoring system can reduce the transmission delay and packet loss probability of data and enhance the instantaneity and reliability of data transmission in the system. Therefore, the new system is more applicable and advanced in the field of coal mine environmental monitoring. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) is a pivotal region for investigating climate change and the emission of greenhouse gases in terrestrial ecosystems. In this study, atmospheric methane columnar concentration (XCH 4) data obtained from GOSAT products were used from March 2010 to February 2022. The comparative study between GOSAT XCH 4 and Waliguan (WLG) ground-based methane measurements in annual terms demonstrated a high consistency, with a correlation coefficient of 0.996, indicating similar trends and amplitudes. Subsequently, a comprehensive investigation was carried out to explore the long-term trends and spatial differences of XCH 4 on the TP, along with its association with climate variables. The findings revealed an east-west gradient in the spatial distribution of XCH 4 , characterized by higher concentrations in the southeast and lower concentrations in the northwest. During the 12-year study period, a consistent upward trend of XCH 4 was exhibited across the whole plateau, ranging from 7.53 to 10.15 ppb/yr, and the areas of exceeding 9 ppb/yr accounted for 80.4% of the study area. The seasonal variation of XCH 4 displayed a typical unimodal distribution, with the highest XCH 4 occurring in late August to early September. The interannual growth rate of XCH 4 was the highest in summer, followed by autumn, winter, and the lowest in spring. To better understand the climate variables influencing XCH 4 on the TP, a Principal Component Analysis (PCA) was performed with a biplot. The results indicated that temperature (TEM), precipitation (PER), soil temperature (Soil_TEM), and soil humidity (Soil_HUM) were positively correlated with XCH 4. However, wind speed (WSPD) and wind direction (WDIR) demonstrated negative correlations with XCH 4. • XCH 4 exhibits a pronounced increasing trend in Tibetan Plateau during 2010–2022. • The spatial distribution of XCH 4 and its interannual growth rates indicate strong regional signals and seasonal cycle. • Principal Component Analysis (PCA) reveals different correlations between XCH 4 and climate factors. [ABSTRACT FROM AUTHOR]

With the introduction of the extended method in Hadamard transform ion mobility spectrometry (HT-IMS), the modulation defects and the false peaks inherently located in conventional HT techniques could be well suppressed. However, a few false peaks are still located in the demultiplexed data of the extended HT-IMS, which is hard to be explained and seriously degrades the performance of the extended HT techniques. In this research, in order to discover the origin of the false peaks in the extended HT-IMS, the measurements of double and multiple ion peaks with IMS have been implemented and the effects of the peak-peak repulsion on the multiplexed data of HT-IMS have been explored. Results show that in multiplexing IMS, the space charge effect existed between two adjacent ion packets would lead to the shifts (deviations) of the ion signal peaks. Simulation results prove that this tiny shifting in the multiplexed data is another critical reason for the false peaks in the demultiplexed data of extend HT-IMS. This is of positive significance for revealing those unknown false peaks in extended HT-IMS and other similar techniques. Simulation results of extended multiplexing HTIMS: (a) simulation spectrum of the signal averaging method; b) Multiplexed data of extended HT-IMS, S-matrix order is 255, number of the extended symbol is 4; c) The simulation demultiplexed data of EHT-IMS, in the inset of frame c, parts of the multiplexed data are demonstrated. Image 1 • The peak-peak repulsion effect on Hadamard multiplexing technique has been evaluated firstly. • A feasible explanation for the unknown false peaks in extended HT-IMS is given. [ABSTRACT FROM AUTHOR]

In order to reduce the energy consumption in wireless sensor networks (WSNs), this paper proposes a distributed event-triggered communication for time synchronization. The clock feature of each node is modeled as the discrete-time second-order dynamics. Each node in the network determines whether and when to broadcast its states to its neighbors based on an event trigger mechanism. For each node in the network, the trigger function is designed based on the disagreement between its current states and those estimated from last transmitted, which thus is independent of the states of its in-neighbors. Then the condition about the updating period and the control gain is presented to guarantee the time synchronization of the network. It is shown that the proposed event-triggered communication can play a good tradeoff between the convergence rate and the communication rate of the time synchronization algorithm, and it also outperforms the corresponding time-triggered communication in the case that the same communication rate is used. Finally, simulation results are given to verify the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]