The movements of clouds and moist air are responsible for temporal changes in sky radiation temperatures. Detailed are measurements of the sky radiation temperatures made during periods of cloud movement and light rain. The measurements were made over the frequency bands 26 to 40 GHz (in the ka-band) and 90 to 98 GHz (in the w-band) using a direct detection and heterodyne radiometer. Temporal derivatives and the spectra of the temperature changes are examined. The measurements indicate that the most rapid temperature changes are due to cloud movements. The standard deviations of these temperature changes were measured at 0.030 K/s for the ka-band and 0.072 K/s for the w-band. The spectral analysis indicated that these changes took place at frequencies less than 10 mHz. The higher frequency fluctuations in the sky radiation temperatures were less than 20 mK and less than 30 mK at ka-band and w-band respectively. This level of fluctuation represents an upper limit set by the difficulty of achieving DC coupling over the long measurement periods of /spl sim/1000 s.
展开▼
机译：云和潮湿空气的运动是造成天空辐射温度随时间变化的原因。详细介绍了在云运动和小雨期间进行的天空辐射温度的测量。使用直接检测和外差辐射计在26至40 GHz（在ka频带）和90至98 GHz（在w频带）的频带上进行测量。检查了时间导数和温度变化的光谱。测量结果表明，最快速的温度变化是由于云运动引起的。这些温度变化的标准偏差在ka波段测量为0.030 K / s，在w波段测量为0.072 K / s。频谱分析表明，这些变化发生在小于10 mHz的频率上。在ka波段和w波段，天空辐射温度的较高频率波动分别小于20 mK和小于30 mK。该波动水平表示由在/ spl sim / 1000 s的长测量周期内难以实现DC耦合而设置的上限。
展开▼
