Instrument : G-band (183 GHz) Vapor Radiometer (GVR)

Instrument Categories
Radiometric

Picture of the G-band (183 GHz) Vapor Radiometer (GVR)

General Overview

The G-Band Vapor Radiometer (GVR) provides time-series measurements of brightness temperatures from four double sideband channels centered at ±1, ±3, ±7, and ±14 GHz around the 183.31-GHz water vapor line. Atmospheric emission in this spectral region is primarily due to water vapor, with some influence from liquid water. The 183.31 ±14-GHz channel is particularly sensitive to the presence of liquid water. The sensitivity to water vapor of the 183.31-GHz line is approximately 30 times higher than at the frequencies of the two-channel microwave radiometer (MWR) for a precipitable water vapor (PWV) amount of less than 2.5 mm. Measurements from this instrument are, therefore, especially useful during low-humidity conditions (PWV < 5 mm).

A detailed description of the calibration algorithm can be found in the instrument handbook. For additional details on the instrument’s design and operations the following references are available:

Pazmany, AL. 2007. “A compact 183 GHz radiometer for water vapor and liquid sensing.” IEEE Transactions on Geoscience and Remote Sensing 45(7): 2202–2207.

Cadeddu, MP, JC Liljegren, and AL Pazmany. 2007. “Measurements and retrievals from a new 183-GHz water-vapor radiometer in the arctic.” IEEE Transactions on Geoscience and Remote Sensing 45(7): 2207–2215.

Available Retrievals and Uncertainty

Neural network retrievals of precipitable water vapor are available from this instrument as value-added product in the datastream nsagvrC1.c1. The retrievals use seasonal neural network coefficients. Uncertainties in the retrieval are expressed as 1-sigma individual error bars. Details of the retrieval algorithm and uncertainty estimation can be found in the following reference:

Cadeddu, MP, DD Turner, and JC Liljegren. 2009. “A neural network for real-time retrievals of
PWV and LWP From Arctic millimeter-wave ground-based observations.” IEEE Transactions on
Geoscience and Remote Sensing 47(7): 1887–1900. A rough estimate of the retrieval uncertainty is:

Precipitable water vapor: varies between 3-4% when PWV is less than 10 mm to ~10% when PWV > 10 mm

Summary Table:

Name Physical Quantity Approximate Uncertainty Datastream Uncertainty Variable in the Datastream
Tbsky1 183.3±1 GHz brightness temperature

1.5-2 K

gvr.b1 N/A
Tbsky2 183.3±3 GHz brightness temperature

1.5-2 K

gvr.b1 N/A
Tbsky3 183.3±7 GHz brightness temperature

1.5-2 K

gvr.b1 N/A
Tbsky4 183.3±14 GHz brightness temperature 1.5-2 K gvr.b1 N/A
pwv Precipitable water vapor between 3-4% (PWV < 10 mm) to ~10% (PWV > 10 mm) gvr.c1 pwv_error

Output Value-Added Products

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

  • gvr : G-band (183 GHz) Vapor Radiometer

Output Datastreams

  • gvr : G-band (183 GHz) Vapor Radiometer

Primary Measurements

The following measurements are those considered scientifically relevant.

Locations

North Slope Alaska
NSAC1 Browse DataCentral Facility, Barrow AK

Contact(s)

Maria Cadeddu
Argonne National Laboratory
(630) 252-7408
mcadeddu@anl.gov