Liquid water path (LWP) and precipitable water vapor (PWV) are geophysical variables used by a large number of ARM data users. These variables are typically retrieved from microwave radiometers (MWRs). Historically, the standard ARM radiometers were 2-channel systems (MWR2) at 23 and 31 GHz, which give uncertainty in LWP of about 25 g/m2. With ARRA funding, new 3-channel systems (MWR3C) at 23, 31, and 90 GHz have been installed at the ENA, SGP, Manus Island, and Darwin sites and as part of both Arm Mobile Facilities (AMFs). The 90-GHz channel has approximately three times the sensitivity to liquid water of the 31-GHz channel, and will therefore markedly improve the accuracy of the LWP when LWP is less than 100 g/m2. Since the median LWP at all the fixed ARM sites is less than 100 g/m2, this improvement is greatly desired.
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Dorsey KS, R Jundt, CB Ireland, MR Wasem, RA Stafford, and A Hunzinger. 2021. 2020 Atmospheric Radiation Measurement (ARM) Annual Report. Ed. by Kathryn Dorsey, U.S. Department of Energy. DOE/SC-ARM-20-020.
Geerts B, G McFarquhar, L Xue, M Jensen, P Kollias, M Ovchinnikov, M Shupe, P DeMott, Y Wang, M Tjernstrom, P Field, S Abel, T Spengler, R Neggers, S Crewell, M Wendisch, and C Lupkes. 2021. Cold-Air Outbreaks in the Marine Boundary Layer Experiment (COMBLE) Field Campaign Report. Ed. by Robert Stafford, ARM user facility. DOE/SC-ARM-21-001. 10.2172/1763013.
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