H2O Antarctica Microwave Stratospheric and Tropospheric Radiometers

The HAMSTRAD (H2O Antarctica Microwave Stratospheric and Tropospheric Radiometers) radiometer is a genuine microwave instrument developed in 2007 by the German Company RPG under the name LHATPRO. It is dedicated for the detection of 1) the 60-GHz oxygen line to measure tropospheric temperature profile, and 2) the 183-GHz water vapour line to get tropospheric H2O profiles, together with the integrated liquid water path (LWP) and integrated water vapour (IWV). The radiometer spent 6 months at the Pic du Midi (France) in 2008 for validation before being sent to Antarctica. HAMSTRAD was deployed at the Concordia station, Dome C, Antarctica (75°06′ S, 123°21′ E, 3233 m above mean sea level, amsl) in January 2009 and is automatically operating since then. The instrument is fully automated and the data are sent to France on a monthly basis.

By considering the HAMSTRAD measurements performed from 2009 to date and other data sets e.g. in situ, radiosondes, satellite, lidar, drone, backtrajectories, mesoscale models, meteorological analyses/reanalyses, we have highlighted i) the strengths and weaknesses of this instrument by calculating biases and correlations, and ii) the different processes occurring in the Antarctic troposphere:
1. diurnal variability of temperature and H2O in the planetary boundary layer,
2. seasonal variability of temperature and H2O in the planetary boundary layer and in the free troposphere,
3. trends in H2O and temperature,
4. temperature vs. H2O correlation along the vertical from the lowermost to the middle troposphere,
5. episodes of ice and supercooled liquid water (SLW) clouds and of diamond dusts above the station
6. SLW cloud radiative forcing and its link with LWP and in-cloud temperature

Validation and scientific studies performed with the HAMSTRAD measurements are listed in the section “References”.

For both absolute humidity and temperature profiles, the retrieval grid is set to 39 levels, namely, at: 0, 10, 30, 50, 75, 100, 125, 150, 200, 250, 325, 400, 475, 550, 625, 700, 800, 900, 1000, 1150, 1300, 1450, 1600, 1800, 2000, 2200, 2500, 2800, 3100, 3500, 3900, 4400, 5000, 5600, 6200, 7000, 8000, 9000, and 10 000 m.

Units are: Kelvin (Temperature), g/m3 (Absolute Humidity), kg/m2 (Integrated Water Vapor, IWV) and g/m2 (Liquid Water Path, LWP).