Atmospheric Radiation Measurement Climate Research Facility US Department of Energy

mwrretv2 > MWR Retrievals with MWRRET Version 2VAP Type(s) > Baseline • Evaluation

Liquid water path (LWP) and precipitable water vapor (PWV) are two important geophysical variables for many areas of atmospheric research. These variables are typically retrieved from microwave radiometers.

Historically, standard ARM microwave radiometers have been 2-channel systems (23.8 and 31.4 GHz). These two channels provide sensitivity to liquid water and water vapor in the atmosphere. ARM also uses 3-channel microwave radiometers (MWR3Cs), which provide time-series measurements of brightness temperatures at 23.8, 30, and 89 GHz. The third channel at 89 GHz provides additional sensitivity to liquid water, especially at low LWPs.

MWRRETv2 is an updated version of mwrret1liljclou—documented in Turner et al. 2007—that extends the physical optimal estimation retrieval of LWP and PWV to microwave radiometers beyond ARM’s original standard 2-channel systems. The LWP retrieval from MWRRETv2 is critical to understanding low-liquid clouds.

MWRRETv2 applies the Turner et al. (2007) optimal estimation retrieval of LWP and PWV to MWR3C measurements. This VAP also includes uncertainty estimates.


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.

Primary Derived Measurements


  • Fixed
  • AMF1
  • AMF2
  • AMF3

Data Details

Developed By Laura Riihimaki | Krista Gaustad | David Turner
Contact Laura Riihimaki
Resource(s) Data Directory
Data format netcdf
Site SGP
Content time range 1 October 2011 - 31 December 2020
Attribute accuracy No formal attribute accuracy tests were conducted.
Positional accuracy No formal positional accuracy tests were conducted.
Data Consistency and Completeness Data set is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details.
Access Restriction No access constraints are associated with this data.
Use Restriction No use constraints are associated with this data.
File naming convention follows ARM standards
Citations Turner, D.D., S.A. Clough, J.C. Liljegren, E.E. Clothiaux, K. Cady-Pereira, and K.L. Gaustad, 2007: Retrieving liquid water path and precipitable water vapor from Atmospheric Radiation Measurement (ARM) microwave radiometers. IEEE Trans. Geosci. Remote Sens., 45, 3680-3690, doi:10.1109/TGRS.2007.903703.

Cadeddu, M. P., Liljegren, J. C., and Turner, D. D., 2013: The Atmospheric radiation measurement (ARM) program network of microwave radiometers: instrumentation, data, and retrievals, Atmos. Meas. Tech., 6, 2359-2372, doi:10.5194/amt-6-2359-2013.


Russell LM, D Lubin, I Silber, E Eloranta, J Muelmenstaedt, S Burrows, A Aiken, D Wang, M Petters, M Miller, A Ackerman, A Fridlind, M Witte, M Lebsock, D Painemal, R Chang, J Liggio, and M Wheeler. 2021. Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE) Science Plan. Ed. by Robert Stafford, ARM user facility. DOE/SC-ARM-21-009. 10.2172/1804710.

Fridlind A, C Chiu, S Collis, J Comstock, S Giangrande, N Hickmon, M Jensen, M Kumjian, P Muradyan, R Newsom, A Sockol, M Sturm, and A Theisen. 2021. ARM Cloud and Precipitation Measurements and Science Group (CPMSG) Workshop Report. Ed. by Robert Stafford, ARM user facility. DOE/SC-ARM-21-005.

Cadeddu MP. 2021. Microwave Radiometer – 3-Channel (MWR3C) Instrument Handbook. Ed. by Robert Stafford, ARM user facility. DOE/SC-ARM/TR-108.

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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