Opportunistic constant target matching is a new method for satellite intercalibration. It solves a long‐standing issue with the traditional simultaneous nadir overpass (SNO) method, namely, that it typically provides only data points with cold brightness temperatures for humidity sounding instruments on sun‐synchronous satellites. In the new method, a geostationary infrared sensor (SEVIRI) is used to select constant target matches for two different microwave sensors (MHS on NOAA 18 and Metop A). We discuss the main assumptions and limitations of the method and explore its statistical properties with a simple Monte Carlo simulation. The method was tested in a simple case study with real observations for this combination of satellites for MHS Channel 3 at 183 ± 1 GHz, the upper tropospheric humidity channel. For the studied 3‐month test period, real observations are found to behave consistently with the simulations, increasing our confidence that the method can be a valuable tool for intercalibration efforts. For the selected case study, the new method confirms that the bias between NOAA 18 and Metop A MHS Channel 3 is very small, with absolute value below 0.05 K.

中文翻译：

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机会常数目标匹配-一种新的卫星互标方法

机会常数目标匹配是卫星互标的一种新方法。它解决了传统的同时最低点立交（SNO）方法的一个长期问题，即它通常只为太阳同步卫星上的湿度探测仪器提供具有冷亮温度的数据点。在新方法中，对地静止红外传感器（SEVIRI）用于为两个不同的微波传感器（NOAA 18上的MHS和Metop A）选择恒定的目标匹配。我们讨论了该方法的主要假设和局限性，并通过简单的蒙特卡洛模拟研究了其统计性质。在一个简单的案例研究中，对该方法的组合进行了实际观察，对MHS频道3（183±1 GHz）（对流层上方的湿度频道）的卫星进行了实际观察。在研究的3个月的测试期间，发现真实的观察结果与模拟一致，从而增加了我们对该方法可以作为相互校准工作的宝贵工具的信心。对于选定的案例研究，新方法证实了NOAA 18和Metop A MHS通道3之间的偏差非常小，绝对值低于0.05K。