The optimal estimation retrieval of liquid water path (LWP) and precipitable water vapor (PWV) have now been applied to the new 3-channel microwave radiometer at Southern Great Plains (SGP). Data for 2015 are now available as an evaluation product, called the Microwave Radiometer Retrieval version 2 (MWRRETv2), with plans to be an operational VAP within the next year.

The evaluation product includes uncertainty estimates. Standard ARM radiometers were historically 2-channel systems at 23 and 31 GHz, which give uncertainty in LWP of about 25 g/m2. New 3-channel systems (MWR3C) with measurements at 23, 31, and 90 GHz have been installed at various sites. The 90 GHz channel has approximately three times the sensitivity to liquid water compared to the 31 GHz channel and will markedly improve the accuracy of the LWP when LWP is less than 100 g/m2. Since the median LWP at all the long-term ARM sites is less than 100 g/m2, this improvement is greatly desired. This evaluation product is an updated version of mwrret1liljclou (documented in Turner et al. 2007) that extends the physical optimal estimation retrieval of PWV and LWP to microwave radiometers (MWR) beyond ARM’s original standard 2-channel MWRs.

Feedback on data formats and quality of these data are requested and can be sent to Laura Riihimaki. To access the data set, please browse the ARM Data Archive. (Go here to create an account to download the data.)

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The ARM Climate Research Facility is a national scientific user facility funded through the U.S. Department of Energy’s Office of Science. The ARM Facility is operated by nine Department of Energy national laboratories.