Instrument : Microwave Radiometer (MWR)

Instrument Categories
Atmospheric Profiling, Cloud Properties, Radiometric

Picture of the Microwave Radiometer (MWR)

General Overview

The Microwave Radiometer (MWR) provides time-series measurements of column-integrated amounts of water vapor and liquid water. The instrument itself is a sensitive microwave receiver that detects the microwave emissions of the vapor and liquid water molecules in the atmosphere at two frequencies: 23.8 and 31.4 GHz.

Integrated water vapor and liquid water path are derived from radiance measurements with a statistical retrieval algorithm that uses monthly derived and location-dependent linear regression coefficients.

More details on the calibration algorithm can be found in:

Liljegren, JC. 1999. "Automatic self-calibration of ARM microwave radiometers." In Microwave Radiometry and Remote Sensing of the Earth’s Surface and Atmosphere. Ed. P. Pampaloni and S. Paloscia, pp. 433-443.

Available Retrievals and Uncertainty

Statistical retrievals of precipitable water vapor and liquid water path are available. The retrievals use monthly derived linear regression coefficients. The monthly rms errors of the retrievals depend on season and location and can be found in the netcdf files global variables. A rough estimate of the retrieval uncertainty is:

  • Precipitable water vapor: ~ 0.5 mm
  • Liquid water path: ~ 0.025 mm

Summary Table:

Name of Variable in the Datastream Physical Quantity Approximate Uncertainty Datastream Uncertainty Variable in the Datastream
Tbsky23 23.8 GHz brightness temperature 0.3 K mwrlos.b1 N/A
Tbsky31 31.4 GHz brightness temperature 0.3 K mwrlos.b1 N/A
vap Retrieved integrated water vapor ~0.5 mm mwrlos.b1 vapor_retrieval_rms_accuracy
liq Retrieved integrated cloud liquid water 0.025 mm mwrlos.b1 liquid_retrieval_rms_accuracy

Output Value-Added Products

This instrument is an input to the following value-added products, which provide improved measurements or derived quantities.

  • 1mwravg : Microwave Radiometer (MWR): brightness temps and water amounts, 1-minute avg
  • 5mwravg : Microwave Radiometer (MWR): 5-minute average integrated vapor and liquid water
  • mwrret1liljclou : Microwave Radiometer Retrievals (MWRRET) of Cloud Liquid Water and Precipitable Water Vapor

Output Datastreams

  • mwrlos : Microwave Water Radiometer (MWR): water liq. & vapor along line of sight (LOS) path

Primary Measurements

The following measurements are those considered scientifically relevant.


North Slope Alaska
NSAC1Browse DataCentral Facility, Barrow AK
NSAC2Browse DataCentral Facility, Atqasuk AK
Southern Great Plains
SGPB1Browse DataHillsboro, KS (Boundary)
SGPB4Browse DataVici, OK (Boundary)
SGPB5Browse DataMorris, OK (Boundary)
SGPB6Browse DataPurcell, OK
SGPC1Browse DataCentral Facility, Lamont, OK
SGPE14Browse DataLamont, OK (Extended, secondary)
SGPS02Browse DataSupplemental 2, Lamont, OK
Tropical Western Pacific
TWPC1Browse DataCentral Facility, Manus I., PNG
TWPC2Browse DataCentral Facility, Nauru Island
TWPC3Browse DataCentral Facility, Darwin, Australia
ARM Mobile Facility
FKBM1Browse DataBlack Forest, Germany
GANM1Browse DataGan Airport, Gan Island, Maldives
GRWM1Browse DataGraciosa Island, Azores, Portugal
HFEM1Browse DataShouxian, Anhui, China
MAGM1Browse DataLos Angeles, CA to Honolulu, HI - container ship Horizon Spirit
MAOM1Browse DataManacapuru, Amazonas, Brazil; AMF1
NIMM1Browse DataNiamey, Niger
PGHM1Browse DataARIES Observatory, Nainital, Uttarkhand, India
PVCM1Browse DataHighland Center, Cape Cod MA; AMF 1
PYEM1Browse DataPoint Reyes, CA
SBSM1Browse DataSteamboat Springs CO, Valley Site
TMPM1Browse DataU. of Helsinki Research Station (SMEAR II), Hyytiala, Finland; AMF2


Maria Cadeddu
(630) 252-7408