A scheme to detect sand/dust weather applying meteorological radars

Sandy dust weather occur frequently in arid and semi-arid areas. It is important to actually detect the sandy dust grain concentration or the visibility of the sandy dust weather for weather forecasting. In this paper, based on numerical calculation of the effective detection distance of different radar detecting the sandy-dust weather with different strength, a scheme to detect sand/dust weather applying existed meteorological radar stations is proposed in this paper. The scheme can be efficient to detect sandy dust weather, for it makes a good supplement to the current deficiencies in detecting sandy dust weather and it’s a cost-saving detection way by using the existed meteorological radars. In addition, the effect of charges carried by sand/dust grains and the relative humidity on the effective detection distance of radar is also investigated, and it shows that these effects will not change the proposed scheme. It will be promising to detect the sandy dust weather in the way of disastrous weather precaution by using this scheme.

Using Lidar and Historical Similar Meteorological Fields to Evaluate the Impact of Anthropogenic Control on Dust Weather During COVID-19

Asian dust can be transported at least one full circuit around the globe. During the transportation, dust can interact with local air-borne dust and pollutants, and has a profound impact on the environment. A novel coronavirus (COVID-19) has been affecting human activities worldwide since early 2020. The Chinese government has implemented emergency control measures. Since April 2020, control measures to reduce anthropogenic emissions have been gradually reduced. The optical properties of aerosols during the dust transport were affected by meteorological conditions, local environmental conditions and human activities. Therefore, two dust weather processes in March 2018 and March 2020 were screened under similar meteorological fields and transportation paths, which were mainly affected by human activities. Based on lidar data, in East China, compared with 2018, the average aerosol optical depth (AOD) of all types of aerosols at 0–4 km in 2020 decreased by 55.48%, while the AOD of dust aerosols decreased by 43.59%. The average particle depolarization ratio and color ratio decreased by 40.33 and 10.56% respectively. Due to the reduction of anthropogenic emissions in China (detected by lidar), the concentration of surface PM2.5 decreased by 57.47%. This indicated that due to the decrease in human activities caused by COVID-19 control measures, the optical properties of aerosols were significantly reduced during dust weather process in eastern China. However, in the Pacific region, compared with 2018, the AOD values of 0–1 km layer and 1–6 km layer in 2020 increased by 56.4% and decreased by 29.2% respectively. The difference between the two contributions of dust aerosols was very small. Meanwhile, compared with 2018, China’s near surface pollutants decreased significantly in 2020, indicating that the near surface AOD of the Pacific in 2020 was mainly contributed by local pollutants. This study was of great significance to the study of long-range and cross regional transport of pollutants.

ESTIMATION DE LA VISIBILITÉ MÉTÉOROLOGIQUE À L’AIDE DES LIENS MICRO-ONDES COMMERCIAUX DE TÉLÉCOMMUNICATIONS

Several factors can attenuate radio signal between transmitting and receiving antenna. One can cite: vegetation, atmospheric gases, fog, water vapor, transmission instruments, rain, temperature, etc... The sources of attenuation differ according to the climate and the relief of each continent or even each country. In this work we aim to show that there is link between microwave signal attenuation and weather visibility in the presence of dust. Weather visibility is a very important factor for the safety of road, sea, rail and air transportation. In the presence of dust, the visibility is strongly reduced and there is also a strong attenuation of the microwave signal propagating between two antennas. By performing a linear regression on the attenuation-visibility scatter plot, we propose a method for real-time estimation of the visibility knowing the microwave signals attenuation. A correlation measurement between the visibility estimated by our method from the real attenuation data of the mobile phone operator Telecel Faso SA (Burkina Faso) and the visibility measured by the National Meteorological Agency of Burkina Faso (ANAM) gave a correlation coefficient of 0.86.

Performance Investigation of a High Data Rate Mode Division Multiplexed-Free Space Optics Link Under Harsh Weather Conditions

The requirement of high data rate information transmission is rising exponentially for supporting different services including social networking, web streaming, and biomedical sensor data transmission. Such services required high channel bandwidth with secure information transmission and immunity to electromagnetic interference. Radio over free space optics (RoFSO) is witnessed as a promising technological solution to provide high data rate transmission over free space channel. We report on the design of a 2×10 Gb/s-10 GHz RoFSO transmission system using the mode division multiplexing technique and evaluate its transmission performance over varying levels of dust weather conditions. The comparison of non-return to zero (NRZ) and return to zero (RZ) binary digital optical modulation techniques is carried out in the proposed system. It is found that the proposed system using NRZ modulation serves 14.5 km transmission range; however, in the case of RZ modulation, it was restricted to 10 km for a target bit error rate (BER) of 10−6, thus resulting in a noticeable link enhancement of 4.5 km. Also, we demonstrate NRZ-based MDM-RoFSO link performance and availability in dust weather conditions using the BER, maximum reachable link range, and eye diagram as key performance parameters. We obtain a reliable transmission of 20 Gb/s-20 GHz data through HG00 and HG01 channels over a link range of 2500–108 m depending on the external dust weather condition. Furthermore, since this investigation shows the feasibility of RoFSO for small size cells, which is an essential feature of 5G mobile network, the proposed system can thus be implemented as a backhaul/fronthaul link for high-band (above 6 GHz) 5G services and for providing secure transmission of biomedical sensor data.

Radiating Benefit of Windbreak and Sand Fixation in the Baijitan Nature Reserve of Lingwu, Ningxia, China

Many important ecosystem services show spatial flow characteristics, which are crucial for the study of environmental processes, such as the transformation, correlation, coordination, and management of ecosystem services at different scales. As a result, flow characteristics should be taken into account when it comes to the evaluation of ecosystem services. The study area was the Baijitan Nature Reserve, used to assess the radiating benefits of the windbreak and sand fixation from 2000 to 2019, based on wind erosion loss and sand spatial erosion models. The main results are as follows: Firstly, the fractional vegetation coverage (FVC) clearly increased over the last 20 years and the medium coverage, which accounted for 66.13%, became the main vegetation cover. The wind speed in the reserve dropped gradually as well. Secondly, sand only affected the nature reserve and the surrounding communities. When the wind speed was above a strong breeze (10.8–13.8 m/s), coarse silt could affect 26 downwind administrative regions, with an affected area of 2.13 × 106 km2. Thirdly, the benefits of windbreak and sand fixation varied with the beneficial range, including distance from the Baijitan Nature Reserve and the beneficial area. Dust deposition decreased as the beneficial distance increased. For instance, Shaanxi Province saw the greatest benefit of windbreak and sand fixation, with a dust deposition reduction of 6.87 × 107 t (1 t = 103 kg), followed by Hubei and Henan Provinces, with reductions of 5.31 × 107 t and 5.59 × 107 t, respectively. Fourthly, the periodical deposition in administrative regions decreased gradually, as did the different influence ranges. The dust depositions in the five phases of Shaanxi Province were 2.04 × 107, 1.83 × 107, 6.63 × 106, 4.65 × 106, and 3.48 × 106 t. Fifthly, medium silt, fine silt, and clay silt could easily drift long distances under the influence of sand-driving wind, thus affecting the air quality in downwind administrative regions. Sixthly, the sand source in Baijitan Nature Reserve was an important factor that caused sand–dust weather in downwind areas. The frequency of sand–dust weather was significantly higher in cities near the sand source than in other regions in downwind areas, and the correlations between particle concentrations less than 10 microns in diameter (PM10) and the time sequences of sand-driving wind reached significant levels in certain cities. We found that the windbreak and sand fixation in Baijitan Nature Reserve could offer great benefits to the downwind area. Establishing a desert nature reserve could be a great way to promote environmentally sustainable development since it could effectively reduce dust deposition and the frequency of sand–dust weather in downwind areas.

Study on sandstorm in the western section of Hexi Corridor of 2020

A diagnostic analysis of the dust storm weather occurring in the western part of the Hexi Corridor from 27-30 June 2020 was carried out using Jiuquan city’s live data, as well as ECMWF numerical forecasts, and the NCEP reanalysis information was used to draw a theta dust storm model based on the routing principle. The results show that: 1.In the early stage of sandstorm, there was no precipitation in Suzhou and Jinta counties in March and April, which resulted in dry surface and thickened soil layer. These factors created favorable conditions for the occurrence of dust weather. 2.Development of unstable trough eastward in front of the ridge of Mountain Ural at 500 hPa, The cold high pressure is continuously strengthened in the process of moving, which is the large-scale system leading to the sandstorm. Thermal depression in front of ground cold front is the main cause for the outbreak of the severe sandstorm. 3.The beginning and ending time of the sandstorm can be accurately predicted by the simulation chart of sandstorm forecast, which has a good indication significance for the sandstorm forecast in the Hexi area.

Performance Evaluation of FSO Communications under Sand-Dust Conditions

Sand-dust weather conditions are considered the primary challenge to free-space optical (FSO) communications. It may cause severe attenuation that is malignant to FSO link performance. This study investigates the impact of sand-dust particles on a laser signal using the radiation propagation method and the small-angle approximation method. Numerical simulation shows that in sand-dust weather conditions, the multiple scattering effect is dominant and results in signal pulse delay and pulse broadening. Furthermore, the signal attenuation follows a negative exponential distribution to the laser wavelength. Superior performance can be achieved by employing a longer wavelength laser to reduce pulse delay and mutual interference.