Instrument : Microwave Radiometer (MWR)
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
|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
- mwrlos : Microwave Water Radiometer (MWR): water liq. & vapor along line of sight (LOS) path
- mwrtip : Microwave Water Radiometer (MWR): airmasses, brightness temperatures (TIP mode)
The following measurements are those considered scientifically relevant.