Meteorological Radiation Observation Based on Precision Solar Spectroradiometer
LIU Li-ying1, ZHENG Feng2*, ZHANG Guo-yu1, XU Yi-gang2, YANG Li-yan2, Lü Wen-hua3, BIAN Ze-qiang3, CHONG Wei3, LI Ye1*
1. Changchun University of Science and Technology, Changchun 130022, China
2. Jiangsu Radio Scientific Institute Co., Ltd., Wuxi 214127, China
3. Meteorological Observation Centre of China Meteorological Administration, Beijing 100081, China
Abstract：The wavelength-integral type solar radiation observation instrument currently used in meteorological service observation has met the bottleneck with insufficient detail of solar radiation and large differences of data, so it has been unable to meet the needs of applied scientific research on the fine observation of solar spectral radiation. Observation methods as well as instrumentation research and development of the precision spectroradiometer with high spectral resolution have become the frontier science and technology issues in solar radiation observation of meteorological field. Under aforementioned scientific research background, our research group has been supported by National (Meteorological) Industry Research Special Funds for Public Welfare Projects. In order to solve the problem of fine observation of solar radiation in the meteorological application field, in-depth scientific research and technology development have been carried out. This paper focuses on the discussion about the instrument development achievements and analysis methods of observation data. Firstly, the spectroradiometer system used for ground-based solar spectral irradiance observation is introduced. The optical bench of the spectroradiometer adopts a spectrograph structure based on flat field concave grating, which has the excellent optical characteristics such as low stray light, high light collection efficiency and high reliability, so it is especially suitable for long-term unattended outdoor meteorological observation. The aberration correction characteristic of flat field concave grating used in the spectroradiometer system is more suitable for the wide spectrum range application from 300 to 1 100 nm, and there is almost no change of spectral resolution covering the entire measured spectrum range, that means the bandwidth of different wavelength channels is basically the same. The spectral resolution (FWHM, Full Width at Half Maximum) is approximately 2 nm when 25 μm slit is used, and the sampling wavelength interval is less than 0.5 nm. So, this spectroradiometer is an advanced spectral irradiance measuring instrument for solar radiation observation, and its spectrum range and spectral resolution match the solar observation demand very well. Secondly, on the basis of the observation data, the observation methods of solar spectral irradiance in meteorology application are expounded and analyzed. The spatial-distribution energy of the solar irradiance is collected by a receiving unit with different device parametric models. The movement process and distribution forms of solar spectral radiation in the hemisphere sky are dimensional constrained and made into three different spectral irradiance components. The three spectral irradiance components are Global Horizontal Irradiance (GHI), Direct Normal Irradiance (DNI) and Diffuse Horizontal Irradiance (DHI). Based on data of GHI, DNI and DHI, the data features and application purpose of three observation forms are expounded. GHI is the actual irradiance intensity level on the earth surface, which is suitable for solar resource assessment. DHI reflects the motion of atmosphere and cloud phase state. DNI as a direct transmission energy form can be used to calculate sunshine duration and analyze atmospheric parameters. Furthermore, the calculus function relationships among observation forms, spectral signature and geographical parameters (longitude, latitude, altitude and air mass) and meteorological parameters (cloud amount and atmospheric absorption) are further analyzed. Compared with the traditional wavelength-integral type radiation observation, the solar spectroradiometer increases the dimensions of the wavelength information channels for the radiation energy observation. From the spectral irradiance data of the direct normal irradiance form, it can be seen that the radiation energy varies significantly at different wavelengths, which are closely related to the movement process of the atmosphere. Therefore, solar spectral irradiance data not only provide more detailed information for service observation, but also provide more various information channels of radiation energy. Using the radiation quantity information of the feature wavelength channels, the atmospheric parameters such as Aerosol Optical Depth (AOD), Total Ozone Column (TOC) and Water Vapor Column (WVC) can be calculated by the inversion models. The precision solar spectroradiometer provides the solar spectral irradiance with high resolution grade in the order of nanometer as the basic service data, and the detailed information on the distribution and vary of solar radiation can be used for research on meteorological models and climatic models, the assessment of photovoltaic resources and the ecological environment, etc. And it also provides impactful scientific research data and helpful observation tools, and abundant interested information can be extracted in radiation energy distribution on wavelength for variety of ecosystem flux monitoring and evolution relationship research, especially in the areas of climate, agriculture and ecology.
Key words：Solar spectral irradiance; Spectroradiometer; Direct normal irradiance; Global horizontal irradiance; Diffuse horizontal irradiance
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