Ice supersaturation as seen from TOVS

[摘要] We have analysed the upper tropospheric humidity with respect to ice(UTHi) data product obtained from the Television Infrared Observation Satellite(TIROS) Operational Vertical Sounder (TOVS)instrument onboard the National Oceanic and Atmospheric AdministrationNOAA-14 polar orbiting satellite. While in the production of theofficial UTHi product values in excess of 100% are ignored,we do not so - in view of many recentresults obtained from a variety of other in-situ and remote sensinginstruments showing that ice supersaturation frequently occurs in theupper troposphere. We show that TOVS is able to detect icesupersaturation at the correct locations (however, only in less thanone percent of its soundings, presumably because of TOVS's lowvertical resolution), and that the supersaturation follows the wellknown exponential behaviour. We conclude that values of UTHi in excessof saturation should not be considered a measurement erroranymore. The similar re-analysis of TOVS data back to 1979 could giveimportant insights into trends of upper tropospheric humidity.

[学科分类] 大气科学