The Arctic Winter Millimeter-Wave Radiometric Experiment 2004

Long-term, high resolution measurements of atmospheric properties in the Arctic are critical to efforts to observe and predict changes in the global climate. Measurement of water vapor during the cold arctic winter is very difficult because of the lack of sensitivity of conventional water vapor radiometers to low amounts of water vapor and because of the uncertainties of radiosondes during these conditions as well. There is a concern that instruments currently used for climate observations may be inadequate to measure low amounts of total-column precipitable water vapor (PWV) in the Arctic.

An Intensive Operating Period (IOP) was conducted at U. S. Department of Energy's Atmospheric Radiation Measurement (ARM) Program's field site near Barrow, Alaska, during March 9 to April 9 2004. Instruments deployed include the Ground-based Scanning Radiometer of NOAA's Environmental Technology Laboratory (with frequencies ranging from 50 to 380 GHz), the Microwave Radiometer and the Radiometric Profiler of the Atmospheric Radiation Measurement (ARM) Program (frequencies from 22.235 to 60 GHz), and the Infrared Cloud Imager operated by Montana State University. These instruments were supplemented by 4-times-a-day Vaisala RS90 radiosonde observations and other in situ observations, including several "Snow White" Chilled Mirror radiosondes. In addition, all of the ARM active cloud sensors (radar and lidar) were operating.

The major goals were to demonstrate that millimeter wavelength radiometers can substantially improve water vapor observations during the Arctic winter. Secondary goals included forward model studies over a broad frequency range, demonstration of recently developed calibration techniques, the comparison of several types of in situ water vapor sensors, and the application of infrared imaging techniques.

Goals

  • Compare microwave vs. millimeterwave radiometric response to low amounts of water vapor and arctic clouds

  • Obtain data for forward model radiative transfer studies at frequencies ranging from 18 to 340 GHz

  • Demonstrate new radiometric receiver and calibration technology

  • Inter-comparison with ARM instruments: Water Vapor Radiometer (MWR), Microwave Profiler (MWRP), Atmospheric Emitted Radiance Interferometer (AERI), Micropulse Lidar (MPL), Millimeter-Wavelength Cloud Radar (MMCR)

Instruments Deployed

Platform Frequencies (GHz) Parameters Derived
ARM Radiometrics WVR (MWR) 23.8, 31.4 Precipitable Water Vapor (PWV), Integrated Cloud Liquid (ICL)
Ground-based Scanning Radiometer (GSR) 50-56 (11 channels) Temperature (T) profile, ICL
89H, 89V ICL
183.31 ± ( 0.5, ± 1, ± 3, ± 5, ± 7, ± 12, ± 15) PWV
340H, 340V PWV, ICL
380.2 + (±4, ±9, ±17) PWV
10 microns Cloud presence
ARM Microwave Profiler (MWRP) {Radiomerics Site} 22.235, 23.035 ,23.835, 26.235, 30.000, 51.250, 52.280, 53.850, 54.940, 56.660, 57.290, 58.800 T profile, PWV, ICL
Infrared Cloud Imager (ICI) 8-14 microns Spatial cloud coverage
Global Positioning System (GPS)   PWV
Radiosonde Number of Launches Parameters Derived
Vaisala RS90 sondes 4-times a day at ARM duplex T, Pressure (P) and Humidity (RH) profiles
1-time a day at Great White site T, P and RH profiles
Snow White (with chilled mirror) sondes 10 total T, P and RH profiles
National Weather Service sondes 2-times a day T, P and RH profiles