南极中山站国产地面太阳辐射观测系统运行评估

Performance of Domestically Made Surface Solar Radiation Observation System at Zhongshan Station, Antarctica

  • 摘要: 对2017年国产地面太阳辐射观测系统在南极中山站运行状况进行评估,结果表明:FS-6A日射表夜间热偏移平均绝对值低于3 W·m-2,通风加热器的加热效应在一定程度上影响了该日射表夜间热偏移,表现在夜间热偏移与近地面风速相关关系降低。与二等标准日射表CM22测值相比,全云天FS-6A日射表测值较CM22日射表偏低,辐照度在约500 W·m-2时低6 W·m-2或-1%,太阳天顶角θ≤86°时绝对(相对)差值平均值小于2.6 W·m-2(小于4.0%)。晴天FS-6A总辐射测值与(投射到水平面)直射辐射和散射辐射之和一致性较好,根据本底地面辐射观测站网(BSRN)设定的总辐射与直射和散射之和的差值阈值,θ<80°时满足阈值(小于2%或小于15 W·m-2)比率为80%以上,而θ≥80°时四象限跟踪太阳模式下满足阈值(小于3.5%或小于20 W·m-2)的比率仅为44%。晴天总辐射、直射辐射、散射辐射测值与参数化模式模拟的辐射值可比性和一致性高、相关系数均大于0.95,但随着太阳辐照度增加,总辐射、直射辐射、散射辐射测值均高于模拟值。

     

    Abstract: Solar irradiance is one important element in conventional meteorology observations. Long-term observations of solar radiation by using China-made wide-band pyranometers have been carried out. However, the performance of instrumental systems is not sufficiently evaluated or analyzed, especially in the polar regions where harsh condition and large seasonal variations of solar elevation causes dramatic variation of surface solar irradiance. To fill this gap, the performance of the domestically made solar radiation observation systems at Zhongshan Station, Antarctica in 2017, including global solar radiation (GSR), direct solar radiation (DIR) and the diffuse solar radiation (DIF) measurements, is evaluated. The averaged nighttime thermal offsets of two domestic FS-6A pyranometers, respectively for GSR and DIF observations, are both less than 3 W·m-2, and their temporal variations are highly consistent. Compared with CM21 or CM22 pyranometer that reach the requirement of the second-class standard and are globally deployed, the additional heating effect of the auxiliary ventilation heater of FS-6A pyranometers significantly reduces the inherently physically-based correlation coefficient between the night thermal offset and the net longwave radiation, and the absolute values of FS-6A thermal offset significantly increase but are within 5 W·m-2 under higher wind speeds (noless than 15 m·s-1). The temporal variations of solar DIF irradiances from two FS-6A pyranometers are highly consistent under cloudy overcast condition, and their solar irradiance values are systemically lower (about -6 W·m-2 or -1%) than that of CM22 as the solar DIF irradiance is about 500 W·m-2 from CM22. However, the absolute (relative) difference is respectively lower than 2.6 W·m-2 (4.0%) as the solar zenith angle (θ) is less than 86 °. The GSR close examination suggests that the ratio of FS-6A GSR absolute difference from the sum of horizontally projected DIR and DIF meeting the requirement of threshold value (less than 2% or 15 W·m-2 with θ≤ 80°) proposed by the baseline surface radiation network (BSRN) is more than 80%. But only 44% samples meet the requirement of the BSRN threshold value (less than 3.5% or 20 W·m-2 with θ> 80°) when the four-quadrant tracking solar disk model is applied in operation. Under cloud-free condition, the measurements of GSR, DIR and DIF from the domestically made instruments are well comparable with the simulations from the parameterized solar radiation model that has been extensively applied in middle-low latitudes, and the correlation coefficients between the simulations and observations are more than 0.95. However, the observations are significantly higher than the simulations as the solar irradiance increases. The results suggest that China domestically made solar radiation observation system is fully qualified for the routine observation in polar regions.

     

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