MEASUREMENTS AND RETRIEVALS FROM A NEW 183-GHz WATER VAPOR RADIOMETER IN THE ARCTIC
| Cadeddu, Maria | Argonne National Laboratory |
Category: Instruments
A new G-band (183 GHz) vapor radiometer (GVR), developed and built by Prosensing Inc. (http://www.prosensing.com), was deployed in Barrow, Alaska, in April 2005. The radiometer was deployed as part of the ongoing Atmospheric Radiation Measurement (ARM) program’s effort to improve water vapor retrievals in the cold, dry Arctic environment. The instrument measures brightness temperatures from four double sideband channels centered at 1, 3, 7, and 14 GHz from 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 GVR will remain in Barrow through the winter and will collect data for several months in a dry and cold environment, when its sensitivity is best. Details of the radiometer hardware and mode of operations are presented in Pazmany’s poster [Pazmany, 2006]. We show the first few months of data collected, and we compare the measurements with model calculations. The models used in the comparison are the modified-Rosenkranz model [Rosenkranz, 1998; Liljegren et al., 2005], and the radiative transfer model MonoRTM based on the Line-by-Line Radiative Transfer Code (LBLRTM) [Clough et al., 1992] widely used in the infrared region. Line parameters in this latter model are based on the HITRAN database. We show that the two models agree well with each other. Biases and standard deviations of the measurement-model differences are smaller than those reported in Racette et al. [2005]. We partially attribute the improved agreement to the use of new radiosondes (Vaisala-RS90) that correct for the dry bias present in previous measurements. We retrieve precipitable water vapor (PWV) and liquid water path (LWP) with a non-linear physical algorithm and compare results with those from the co-located dual-channel microwave radiometer (MWR) and radiosondes. References: Clough, S.A., M.J. Iacono, and J.-L. Moncet, 1992: Line-by-line calculation of atmospheric fluxes and cooling rates: Application to water vapor. J. Geophys. Res., 97, 15761-15785. Liljegren, J.C., S.A. Boukabara, K. Cady-Pereira, and S.A. Clough, 2005: The effect of the half-width of the 22-GHz water vapor line on retrievals of temperature and water vapor profiles with a twelve-channel microwave radiometer. IEEE Trans. Geosci. Remote Sensing, 43 (5), 1102-1108. Racette, P.E., E.R. Westwater, Y. Han, A.J. Gasiewski, M. Klein, D. Cimini, D. Jones, W. Manning, E.J. Kim, J.R. Wang, V. Leuski, and P. Kiedron, 2005: Measurement of low amounts of precipitable water vapor using ground-based millimeter-wave radiometry. J. Atmos. Ocean. Tech., 22 (4), 317-333. Rosenkranz, P.W., 1998: Water vapor microwave continuum absorption: A comparison of measurements and models. Radio Sci., 33, 919-928. Pazmany, A. L., 2006: An operational ground-based and airborne PMS 2-D probe canister-mounted G-band (183 GHz) water vapor radiometer. 2006 ARM Science Team Meeting, Albuquerque, NM.
This poster will be displayed at the ARM Science Team Meeting.
