Investigations of optical environment changes in the dunhuang gobi site of the chinese radiometric calibration sites
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摘要: 中国遥感卫星辐射校正场敦煌戈壁场区在国内外遥感卫星在轨辐射定标与定量化应用领域具有不可替代的作用。随着2016年敦煌场区外围南侧熔盐塔式光热发电项目的建成并投入使用,集热塔散射辐射对场区光环境的影响程度有待开展详细的分析评估。本文开发了使用Monte Carlo三维辐射传输模型模拟与CE318多通道光度计等高线实测分析相结合的定量分析方法,解决了散射辐射交融于背景辐射中难以定量评估的问题。通过使用新型的ASC200云量自动观测仪,提高了晴空判识精度。通过开发CE318四象限定位修正算法,有效提高了观测数据质量。2020年1−3月收集到的有效数据显示除了550 nm通道,集热塔未对天空漫射辐射带来明显影响。对于500 nm通道,在有效数据对应的观测几何下(距离0.87−3.07 km,观测天顶角77.30−51.32°),集热塔吸热器对天空漫射辐射的影响不超过0.93%。与模型模拟的结果结合起来分析后,可以得出当距离电站2公里时大电站散射辐射带来的天空漫射辐射相对变化<1.62%,大于等于3公里时相对变化<0.93%的结论。本项研究成果对利用敦煌场开展遥感定量化应用,准确评估发电站引进的不确定度因素具有积极意义。Abstract: The Dunhuang Gobi Site of the Chinese Radiometric Calibration Sites (CRCS) has an irreplaceable role in the field radiometric calibrations and quantitative applications in remote sensing satellites. In 2016, the molten salt tower concentrating solar power (CSP) project in the south side of the Dunhuang Site completed and began operation. The scattered radiation of the heat collection tower has an impact on diffused sky radiation. The influence on the optical environment of the calibration site needs to be analyzed and evaluated in detail. This paper focuses on the scattered radiation of the heat absorber on the top of the heat collection tower. The influence of the heat absorber was analyzed quantitatively based on the Monte Carlo three-dimensional radiation transmission model simulation and in situ CE318 multi-channel photometer almucantar measurements. By measuring the data with a new cloud cover automatic observing instrument ASC200, the accuracy of clear sky measurements improved, and the development of the CE318 four-quadrant location correction algorithm effectively increased the amount of valid data that meets our threshold requirements. The effective data collected from January to March 2020 shows that the molten salt tower CSP project has no significant impact on the sky diffuse radiation outside the 550 nm channel. In the 500 nm channel, under the geometric parameters corresponding to the valid data (distance 0.87−3.07 km, observation zenith angle 77.30−51.32°), the impact of the molten salt tower heat absorber on diffuse sky radiation does not exceed 0.93%. Combined with the analysis of the model simulation results, it can be concluded that the relative change of the sky diffuse radiation caused by the scattered radiation of the large power station is less than 1.62% at 2 km away, and the relative change is less than 0.93% when it is at least 3 km away. The research results have positive significance for the use of Dunhuang Site to conduct quantitative applications in remote sensing and the accurate evaluation of the uncertainties introduced by power stations.
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表 1 模拟的相关参数定义
Table 1. Definitions of parameters in the simulation
相关参数 取值范围 模拟区域范围 11 km*11 km
(设定集热塔位于模拟区域中心像元的中央)水平空间分辨率 1 km 反射光源性质 离地面高度260米;向上各角度随机发射 计算波段 0.55微米 大气背景 中纬夏季大气考虑H2O、O2、O3气体吸收和
大气分子瑞利散射气溶胶特性 光学厚度0.1;单次散射反照率0.938;
不对称因子0.764地表特性 地表反照率0.2 表 2 CE318通道设置
Table 2. CE318 channel specifications
编号 中心波长 带宽 观测模式 1 1020 nm 10 nm S、A、K 2 1640 nm 25 nm S、A、K 3 870 nm 10 nm S、A、K 4 675 nm 10 nm S、A、K 5 440 nm 10 nm S、A、K 6 500 nm 10 nm S、A、K 7 1020i nm 10 nm S 8 936 nm 10 nm S 9 380 nm 2 nm S 10 340 nm 2 nm S 表 3 CE318性能参数
Table 3. CE318 performance parameters
项目 内容 视场 1.2° 探测器 铟镓砷(InGasn)探测器:1020i nm,1640 nm硅探测器:其它 工作温度 −30至+ 60 °C 太阳追踪方法 四象限探测器主动跟踪 跟踪精度 优于0.1° 天空漫射辐射
观测频率固定时刻与大气质量数 动态范围 增益可调 量化等级 15 表 4 ASC200性能参数
Table 4. ASC200 performance parameters
项目 内容 观测指标 可见光云量、红外云量、综合云量 红外波长 8−14微米 视场角 可见光180°,红外160° 采样周期 10分钟 工作温度 −45 °C至55 °C 表 5 HIM性能参数
Table 5. HIM performance parameters
项目 内容 观察内容 总天空辐照度,天空漫射辐照度,漫射/总漫射比 波长 400−2400 nm 半高宽 4 nm @ 400−950 nm,15 nm @ 950−1700 nm,
20 nm @ 1700−2400 nm采样期 6分钟 工作温度 −30 °C至60 °C 信噪比 ≥600@ 400−1000 nm,≥300@ 1000−1700 nm,
≥200@ 1700−2400 nm(M = 2,非吸收通道)表 6 观测数据的质量控制阈值
Table 6. Observation data quality control threshold
项目 数值 云量 0 光学厚度 <0.2 ALL与ALR相对偏差的标准差 <1% 相对偏差计算点与大小电站的投影距离 >5 km 太阳与大小电站的投影距离 >2.5 km ALL与ALR观测时间差异 <1 min 表 7 卫星观测到的集热塔反射光的辐射能量相对分布情况
Table 7. The relative distribution of the radiant energy of the light reflected by the heat collection tower observed by the satellite
距离 0度 10度 20度 30度 40度 50度 0 km 1.000 0.780 0.549 0.381 0.277 0.202 1 km 0.434 0.369 0.285 0.194 0.179 0.162 2 km 0.035 0.033 0.033 0.032 0.037 0.047 3 km 0.020 0.019 0.020 0.021 0.023 0.027 4 km 0.016 0.016 0.016 0.017 0.020 0.023 5 km 0.015 0.015 0.015 0.016 0.018 0.021 表 8 各级筛选后有效观测数据量值统计(组)
Table 8. Statistics of effective observation data after being selected at different levels (group)
筛选项目 1020 nm 1640 nm 870 nm 576 nm 440 nm 500 nm 合计 a) 804 778 611 466 787 565 4011 b) 135 132 81 54 135 70 607 c) 45 77 47 44 43 44 300 d) 0 3 1 6 27 22 59 e) 0 2 1 2 22 16 43 f) 0 2 0 1 14 9 26 g) 0 2 0 1 14 9 26 h) 0 2 0 1 14 9 26 表 9 吸热器散射辐射带来的相对偏差(440 nm)
Table 9. Relative deviation due to scattered radiation from the heat absorber (440 nm)
UTC Time AOD Sz (°) Sa (°) Beta (°) HB (km) on DegB (°) DdegB (°) RdevB (%) RdevBr (%) HS (km) on DegS (°) DdegS (°) RdevS (%) RdevSr (%) 03-10 08:59 0.15 61.83 235.34 0.07 2.06 1 85.37 4.63 −1.18 −1.08 1.54 0 124.87 4.87 −0.29 −0.31 03-10 07:59 0.14 53.28 220.75 0.11 2.86 1 70.77 0.77 −1.14 −0.92 2.14 0 110.27 9.73 −1.57 −1.49 03-10 06:59 0.15 47.20 202.90 0.13 3.55 1 52.92 2.92 −0.04 0.31 2.65 0 92.42 2.42 −1.37 −1.18 03-09 10:27 0.17 77.14 252.07 0.09 0.88 1 102.09 2.09 −0.70 −0.72 0.66 0 141.59 1.59 0.24 0.14 03-09 09:59 0.15 72.12 247.04 0.12 1.24 1 97.06 2.94 −2.11 −2.07 0.93 0 136.56 3.44 −0.63 −0.74 03-02 09:02 0.15 64.41 233.46 0.06 1.84 1 83.48 3.48 −0.51 −0.42 1.38 1 122.98 2.98 −1.23 −1.24 03-02 07:02 0.18 50.22 202.09 0.13 3.19 1 52.12 2.12 −0.20 0.19 2.39 0 91.62 1.62 −1.47 −1.28 02-27 10:14 0.14 77.10 246.64 0.09 0.88 1 96.66 3.34 −0.89 −0.87 0.66 0 136.16 3.84 −0.75 −0.84 02-27 09:02 0.16 65.23 232.61 0.16 1.77 1 82.63 2.63 −1.47 −1.23 1.33 0 122.13 2.13 0.47 0.39 02-27 08:02 0.19 57.00 218.41 0.09 2.49 1 68.43 1.57 0.09 0.30 1.86 0 107.93 7.93 1.33 1.38 02-27 07:02 0.18 51.24 201.49 0.08 3.08 1 51.51 1.51 −0.51 −0.29 2.30 0 91.02 1.02 −0.61 −0.50 01-25 09:24 0.16 76.61 230.44 0.11 0.92 1 80.46 0.46 −0.18 0.00 0.69 0 119.97 0.03 −0.81 −0.91 01-25 09:03 0.17 73.56 226.29 0.06 1.13 1 76.32 3.68 −0.14 −0.03 0.85 0 115.82 4.18 −0.60 −0.64 01-10 07:56 0.19 68.63 211.65 0.04 1.50 0 61.67 1.67 −1.02 −0.89 1.12 1 101.17 1.17 −0.44 −0.43 表 10 吸热器散射辐射带来的相对偏差(500 nm)
Table 10. Relative deviation due to scattered radiation from the heat absorber (500 nm)
UTC Time AOD Sz (°) Sa (°) Beta (°) HB (km) on DegB (°) DdegB (°) RdevB (%) RdevBr (%) HS (km) on DegS (°) DdegS (°) RdevS (%) RdevSr (%) 03-10 09:00 0.14 62.01 235.59 0.12 2.04 1 85.61 4.39 −0.85 −0.63 1.53 0 125.11 5.11 0.88 0.87 03-10 08:00 0.14 53.42 221.04 0.25 2.85 1 71.06 1.06 −0.74 −0.14 2.13 0 110.56 9.44 −1.19 −0.97 03-03 08:03 0.15 55.92 219.77 0.14 2.60 1 69.80 0.20 −4.01 −3.65 1.94 0 109.30 9.30 −1.21 −1.10 02-27 10:16 0.14 77.30 246.84 0.08 0.87 1 96.86 3.14 0.29 0.32 0.65 0 136.36 3.64 −0.10 −0.18 02-27 07:03 0.16 51.32 201.84 0.14 3.07 1 51.86 1.86 −2.24 −1.81 2.29 0 91.36 1.36 −0.46 −0.22 01-25 09:25 0.15 76.80 230.69 0.17 0.90 1 80.71 0.71 0.57 0.88 0.68 0 120.21 0.21 −0.09 −0.21 01-25 09:04 0.16 73.72 226.51 0.11 1.12 1 76.54 3.46 0.68 0.93 0.84 0 116.04 3.96 −0.20 −0.25 01-10 08:58 0.17 75.87 224.52 0.08 0.97 0 74.54 4.54 0.49 0.71 0.72 1 114.04 5.96 0.31 0.28 01-10 07:57 0.17 68.75 211.92 0.07 1.49 0 61.94 1.94 −0.50 −0.25 1.12 1 101.44 1.44 −0.02 0.01 表 11 大电站散射辐射带来的天空漫射辐射相对变化随距离与观测角度变化(%)
Table 11. The relative change of the sky diffuse radiation caused by the scattered radiation from the large power station changes with distance and the observation angle (%)
距离 0度 10度 20度 30度 40度 50度 0 km 34.44 26.87 18.91 13.12 9.54 6.96 1 km 14.95 12.71 9.82 6.68 6.17 5.58 2 km 1.21 1.14 1.14 1.10 1.27 1.62 3 km 0.69 0.65 0.69 0.72 0.79 0.93 4 km 0.55 0.55 0.55 0.59 0.69 0.79 5 km 0.52 0.52 0.52 0.55 0.62 0.72 -
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