Evaluation of the Accuracy of Downward Radiative Flux Observations at the Sea Surface
Evaluation of the Accuracy of Downward Radiative Flux Observations at the Sea Surface
复制标题
海面向下辐射通量观测精度评估
DOI：
10.1007/s10872-015-0345-x
复制
发表时间：
2016
影响因子：
2.3
通讯作者：
T. Hayasaka
中科院分区：
文献类型：
--
作者：
K. Yamada;T. Hayasaka
由于观测次数有限和辅助设备的限制，对海面向下辐射通量的观测通常含有不确定性。缺乏太阳直接辐射和通风系统的遮阳会造成偏差或随机误差。为了评估浮标辐射测量的误差，将向下的短波和长波辐射通量与国际卫星云气候学计划(ISCCP)、日本55年再分析(JRA55)和中分辨率成像光谱仪(MODIS)反演的3小时和白天平均的模式计算进行了比较。云遮蔽通过MTSAT-1R和现场观测相结合的方式进行评估。将位于浮标观测站附近的地面观测站的一致观测结果与卫星和再分析产品进行了比较。与反演值相比，浮标处的偏差对长波和短波通量的估计分别大致偏高和偏低。在晴空条件下，利用3小时平均，长波和短波辐射的浮标偏差分别比陆地大23-34W/m−2和13-51W/m−2。当对长波使用白天平均时，偏差的差异减小，而对短波的偏差随着白天平均的增加而增大。为了评估环境因素对浮标观测的影响，我们比较了降雨量、风速和太阳天顶角与偏差。我们发现，降雨和风速影响浮标测温仪，使其高估了长波通量。太阳天顶角的余弦不会导致对长波通量的高估，穹顶加热的影响很小。由于倾斜，大风导致对短波辐射通量的低估。当使用日平均值时，风的影响就会减小。
Observations of downward radiative flux at the sea surface generally contain uncertainty due to limited numbers of observations and limitations of auxiliary equipment. The lack of shading from direct solar radiation and ventilation systems causes bias or random errors. To evaluate the error of radiation measurements at buoys, downward shortwave and longwave radiative fluxes are compared with International Satellite Cloud Climatology Project (ISCCP), Japanese 55-year Reanalysis (JRA55), and Moderate Resolution Imaging Spectroradiometer (MODIS) retrieved model calculations of 3-h and daytime averages. Cloud masking is evaluated by a combination of MTSAT-1R and in situ observations. Coincident observations from a land-surface station located near the buoy observatories are compared with satellite and reanalysis products. The bias at buoys, compared with retrievals, approximately over- and under-estimate for longwave and shortwave fluxes, respectively. The bias at buoys is larger and smaller than the land by 23–34 W m−2for longwave and 13–51 W m−2for shortwave radiation using 3-h averages under clear-sky conditions. The differences in bias decrease when using daytime averages for longwave, but the difference for shortwave increases with daytime averages. To evaluate the effect of environmental factors on buoy observations, we compared rainfall, wind speed, and solar zenith angle with the biases. We found that rainfall and wind speed affect buoy pyrgeometers such that they overestimate the longwave flux. The cosine of solar zenith angle does not cause overestimation for longwave flux, and the effect of dome heating is small. The strong wind causes underestimation of the shortwave radiative flux due to tilting. The effect of wind is reduced when daily averages are used.