Microwave radiometer for cloud carthography: A 22-channel ground-based microwave radiometer for atmospheric research

A 22-channel Microwave Radiometer for Cloud Carthography (MICCY) for the profiling of tropospheric temperature, humidity, and cloud liquid water has been developed. The radiometer has 10 channels along the high-frequency wing of the 22.235 GHz water vapor line, 10 channels along the low-frequency side of the 60 GHz oxygen complex, and 2 channels at 90 GHz. Two features make the radiometer a unique tool for the observation of small-scale structures related to cloud processes: (1) Atmospheric brightness temperatures are measured simultaneously at all channels with an integration time of 1 s. (2) A Cassegrain system including a 90 cm off-axis parabolic mirror leads to a spatial resolution better than 1° full width at half maximum for all frequencies. The necessity of these features for cloud observations is demonstrated. Algorithms for the retrieval of integrated water vapor, integrated cloud liquid water, and the profiles of temperature and humidity were developed on the basis of artificial neural networks. Measurement examples, including comparisons with radiosondes, demonstrate the systems capabilities for high-resolution atmospheric monitoring.