Development and testing of the Active Temperature, Ozone and Moisture Microwave Spectrometer (ATOMMS) cm and mm wavelength occultation instrument

[摘要] We present initial results from testing a new remote sensing system calledthe Active Temperature, Ozone and Moisture Microwave Spectrometer (ATOMMS).ATOMMS is designed as a satellite-to-satellite occultation system formonitoring climate. We are developing the prototype instrument for anaircraft to aircraft occultation demonstration. Here we focus on fieldtesting of the ATOMMS instrument, in particular the remote sensing of waterby measuring the attenuation caused by the 22 GHz and 183 GHz water absorptionlines.

Our measurements of the 183 GHz line spectrum along an 820 m path revealedthat the AM 6.2 spectroscopic model provdes a much better match to theobserved spectrum than the MPM93 model. These comparisons also indicate thaterrors in the ATOMMS amplitude measurements are about 0.3%. Pressuresensitivity bodes well for ATOMMS as a climate instrument. Comparisons with ahygrometer revealed consistency at the 0.05 mb level, which is about 1%of the absolute humidity.

Initial measurements of absorption by the 22 GHz line made along a 5.4 kmpath between two mountaintops captured a large increase in water vaporsimilar to that measured by several nearby hygrometers. A storm passagebetween the two instruments yielded our first measurements of extinction byrain and cloud droplets. Comparisons of ATOMMS 1.5 mm opacity measurementswith measured visible opacity and backscatter from a weather radar revealedfeatures simultaneously evident in all three datasets confirming the ATOMMSmeasurements. The combined ATOMMS, radar and visible information revealed theevolution of rain and cloud amounts along the signal path during the passageof the storm. The derived average cloud water content reached typicalcontinental cloud amounts. These results demonstrated a significant portionof the information content of ATOMMS and its ability to penetrate throughclouds and rain which is critical to its all-weather, climate monitoringcapability.

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