Surface solar irradiance (SSI) nowcasting (0–3 h) is an effective way to overcome the intermittency of solar energy and to ensure the safe operation of grid-connected solar power plants. In this study, an SSI estimate and nowcasting system was established using the near-infrared channel of Fengyun-4A (FY-4A) geostationary satellite. The system is composed of two key components: The first is a hybrid SSI estimation method combining a physical clear-sky model and an empirical cloudy-sky model. The second component is the SSI nowcasting model, the core of which is the derivation of the cloud motion vector (CMV) using the block-matching method. The goal of simultaneous estimation and nowcasting of global horizontal irradiance (GHI) and direct normal irradiance (DNI) is fulfilled. The system was evaluated under different sky conditions using SSI measurements at Xianghe, a radiation station in the North China Plain. The results show that the accuracy of GHI estimation is higher than that of DNI estimation, with a normalized root-mean-square error (nRMSE) of 22.4% relative to 45.4%. The nRMSE of forecasting GHI and DNI at 30–180 min ahead varied within 25.1%–30.8% and 48.1%–53.4%, respectively. The discrepancy of SSI estimation depends on cloud occurrence frequency and shows a seasonal pattern, being lower in spring–summer and higher in autumn–winter. The FY-4A has great potential in supporting SSI nowcasting, which promotes the development of photovoltaic energy and the reduction of carbon emissions in China. The system can be improved further if calibration of the empirical method is improved. 相似文献
The paper analyzes the radon data of nearly two decades on the Jiayuguan fault zone,discusses the main influencing factors,and puts forward the relationship between radon and air temperature,ground temperature and rainfall.We summarized the earthquake reflecting effect for ML≥5.0 about 400km within the Jiayuguan station,and reached the conclusion that it has better earthquake-reflecting ability before an earthquake,usually appearing as abnormal changes in sustained low value.By extracting the annual trend of radon in Jiayuguan station over many years,we discovered that the annual trend of radon has a close relationship with the seismic activity in surrounding areas,namely,if the annual variation of radon is larger,the seismic activity in surrounding areas is stronger;Otherwise,if the annual variation of radon is relatively stable,the seismic activity in the vicinity is weak. 相似文献
This paper proposes a new method of integrated system calibration that uses the transmitting and receiving signals from the impulse ground penetrating radar itself. In order to eliminate the influence from each subsystem or part including antenna, transmitter, receiver, signal processing circuits and transmission cables, two new calibration parameters that are different from the conventional S-parameters are introduced. The characteristic and influence of all parts in the transmitting and receiving channels are incorporated into the calibration equation through the new parameters. The calibration results of the radar detection data show that the new integrated system calibration can improve the quality of the data greatly in many aspects. It removes direct coupled waves, suppresses wave distortion and tail oscillation, and improves the quality of waveform and signal-clutter-ratios. It also compresses the pulse width and enhances resolution. 相似文献
The Dinghushan flux observation site, as one of the four forest sites of ChinaFLUX, aims to acquire long-term measurements of CO2 flux over a typical southern subtropical evergreen coniferous and broad-leaved mixed forest ecosystem using the open path eddy covariance method. Based on two years of data from 2003 to 2004, the characteristics of temporal variation in CO2 flux and its response to environmental factors in the forest ecosystem are analyzed. Provided two-dimensional coordinate rotation, WPL correction and quality control, poor energy-balance and underestimation of ecosystem respiration during nighttime implied that there could be a CO2 leak during the nighttime at the site. Using daytime (PAR > 1.0 μmol−1·m−2·s−1) flux data during windy conditions (u* > 0.2 m·s−1), monthly ecosystem respiration (Reco) was derived through the Michaelis-Menten equation modeling the relationship between net ecosystem C02 exchange (NEE) and photosynthetically active radiation (PAR). Exponential function was employed to describe the relationship between Reco and soil temperature at 5 cm depth (Ts05), then Reco of both daytime and nighttime was calculated respectively by the function. The major results are: (i) Derived from the Michaelis-Menten equation, the apparent quantum yield (α) was 0.0027±0.0011 mgCO2·μmol−1 photons, and the maximum photosynthetic assimilation rate (Amax) was 1.102±0.288 mgCO2·m−2·s−1. Indistinctive seasonal variation of α or Amax was consistent with weak seasonal dynamics of leaf area index (LAf) in such a lower subtropical evergreen mixed forest, (ii) Monthly accumulated Reco was estimated as 95.3±21.1 gC·m−2mon−1, accounting for about 68% of the gross primary product (GPP). Monthly accumulated WEE was estimated as −43.2±29.6 gC·m−2·mon−1. The forest ecosystem acted as carbon sink all year round without any seasonal carbon efflux period. Annual NEE of 2003 and 2004 was estimated as −563.0 and −441.2 gC·m−2·a−1 respectively, accounting for about 32% of GPP.
