Initial evaluation of profiles of temperature, water vapor, and cloud liquid water from a new microwave profiling radiometer.

To measure the vertical profiles of temperature and water vapor that are essential for modeling atmospheric processes, the Atmospheric Radiation Measurement (ARM) Program of the U. S. Department of Energy launches approximately 2600 radiosondes each year from its Southern Great Plains (SGP) facilities in Oklahoma and Kansas, USA. The annual cost of this effort exceeds $500,000 in materials and labor. Despite the expense, these soundings have a coarse temporal resolution and reporting interval compared with model time steps. In contrast, the radiation measurements used for model evaluations have temporal resolutions and reporting intervals of a few minutes at most. Conversely, radiosondes have a much higher vertical spatial resolution than most models can use. Modelers generally reduce the vertical resolution of the soundings by averaging over the vertical layers of the model. Recently, Radiometries Corporation (Boulder, Colorado, USA) developed a 12-channel, ground-based microwave radiometer capable of providing continuous, real-time vertical profiles of temperature, water vapor, and limited-resolution cloud liquid water from the surface to 10 km in nearly all weather conditions. The microwave radiometer profiler (MWRP) offers a much finer temporal resolution and reporting interval (about 10 minutes) than the radiosonde but a coarser vertical resolution that may be more appropriate for models. Profiles of temperature, water vapor, and cloud liquid water are obtained at 47 levels: from 0 to 1 km above ground level at 100-m intervals and from 1 to 10 km at 250-m intervals. The profiles are derived from the measured brightness temperatures with neural network retrieval. In Figure 1, profiles of temperature, water vapor, and cloud liquid water for 10 May 2000 are presented as time-height plots. MWRP profiles coincident with the 11:31 UTC (05:31 local) and 23:47 UTC (17:47 local) soundings for 10 May are presented in Figures 2 and 3, respectively. These profiles illustrate typical performance for temperature inversion and lapse conditions.