One of the greatest obstacles in the exploitation of wind and solar energy is their intermittency and fluctuation. Long-term dataset of wind energy resource, which is built on basis of atmospheric numerical models, has been proved to be the most effective approach for wind energy resource assessment in wide area, on grid level and in fine resolution, as well as renewable energy electric energy capability forecast, site planning and dispatch/ operation schedule making of power system. To improve the accuracy of wind energy resource dataset by numerical models, the Weather Research and Forecasting model (WRF) and the Climate Four-Dimensional Data Assimilation (CFDDA) are adopted to conduct a sensitivity experiment, in 9 km spatial resolution, to distinguish a reliable model configuration in this study. Based on the statistics between WRF-CFDDA model output in hub-height wind speed and in-situ observations (sited on typical wind farms in Gansu, Xinjiang and Jilin province, 2010-2013), it has been confirmed that the model configuration with MERRA2 background field, Topowind topographic correction method and smoothed VASSO (VAriance of Sub-grid Scale Orography) terrain data is the most reasonable one, with a correlation coefficient 0.79 and RMSE 1.62 for 10-m height wind speed. Following this configuration, with assimilating all 30-year (1987-2016) ground-based meteorological observation from Chinese international exchange sites, the wind energy resource from 1987 to 2016 around China has been hindcasted and assessed in a resolution of 9 km, 15 min. The hindcast is capable to reproduce the characteristics in temporal and spatial distribution. This model system can be a reliable tool for reproducing decades of reanalyzed climatology and finer resolution assessment on hub-height wind energy, moreover, for reconstruction of typical wind power output curve.
How to exclude the irrelevant information (background points) from the roadside LiDAR data and keep the objects of interest (e.g., vehicles and pedestrians) under congestions and occlusions is a challenge for LiDAR data processing. This paper developed a computation-effective point-based method for the roadside LiDAR data background filtering. The proposed method can provide a dynamic matrix to store the locations of the background points. The background points were identified based on the number of the neighbors, and the distance between the points in the current frame and the aggregated frames. Performance of the proposed method was evaluated using the LiDAR data collected at different scenarios. The results showed that the proposed method could effectively filter the background points under different situations (roads with different speed limits, congested traffic, and package loss, etc.). Compared to the state-of-the-art of filtering, the proposed method could reduce the computation load and improve the accuracy of background filtering.
Image formation of synthetic aperture radar, which virtually observes the scenes and identifies targets along the predetermined trajectory, can be applied to ice-sounding data in the time domain, to map subglacial topographic structures with less sidelobe clutters. However, complex signal transmission path within stratified media limits the efficiency and accuracy of focusing. Here, we present the method to analyze the wavenumber support region by decomposing in the spectrum domain the combined vector formed from multi-paths in stratified media. This assists to determine the lowest Nyquist sampling rate, which essentially accelerates the reconstruction of aliased-free images and can be inherently inserted into the fast factorized back projection algorithm framework, based on divide-and-conquer scheme, recursively yielding low-to-high quality images. With this technique, along-track motion perturbations of flights and unknown tomography variations, can be accommodated at the additional but neglectable computational expenses. Results from real ice-sounding data in Antarctica are presented to validate the promising performance of the proposed method.
Rate coefficients at ambient temperature and atmospheric pressure for the reaction of ozone with 2-methoxypropene (2-MPE) and 2-ethoxypropene (2-EPE) were determined in an evacuable 100 L Teflon reaction chamber using absolute and relative rate methods. The product experiments were carried out using a 50 L Teflon reaction chamber in conjunction with FTIR as the detection technique. The rate coefficients (k in units of cm3 molecule−1 s−1) obtained are 1.18 ± 0.13 × 10−17 and 1.89 ± 0.23 × 10−17 for reactions with 2-MPE and 2-EPE, respectively. The effects of the alkoxy group on the gas-phase reactivity of alkyl vinyl ethers toward ozone are compared and discussed. The major ozonolysis products are methyl acetate, formaldehyde and CO2 for 2-MPE, and ethyl acetate, formaldehyde and CO2 for 2-EPE. Possible mechanisms for the two vinyl ethers are proposed based on the observed reaction products. Additionally, atmospheric lifetimes of 32 h and 21 h for 2-MPE and 2-EPE were estimated based on the measured rate constants and the ambient tropospheric concentration of ozone, respectively. The obtained values of the lifetimes indicate that the reaction with ozone is an important loss process for these vinyl ethers in the atmosphere, especially in polluted areas.
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