Abstract
Microwave radiometry is a suitable technique to measure atmospheric
temperature profiles with high temporal resolution during clear sky and
cloudy conditions. In this study, we included cloud models in the inversion
algorithm of the microwave radiometer TEMPERA (TEMPErature RAdiometer) to
determine the effect of cloud liquid water on the temperature retrievals. The
cloud models were built based on measurements of cloud base altitude and
integrated liquid water (ILW), all performed at the aerological station
(MeteoSwiss) in Payerne (Switzerland). Cloud base altitudes were detected
using ceilometer measurements while the ILW was measured by a HATPRO
(Humidity And Temperature PROfiler) radiometer. To assess the quality of the
TEMPERA retrieval when clouds were considered, the resulting temperature
profiles were compared to 2 years of radiosonde measurements. The TEMPERA
instrument measures radiation at 12 channels in the frequency range from 51
to 57 GHz, corresponding to the left wing of the oxygen emission line
complex. When the full spectral information with all the 12 frequency
channels was used, we found a marked improvement in the temperature
retrievals after including a cloud model. The chosen cloud model influenced
the resulting temperature profile, especially for high clouds and clouds with
a large amount of liquid water. Using all 12 channels, however, presented
large deviations between different cases, suggesting that additional
uncertainties exist in the lower, more transparent channels. Using less
spectral information with the higher, more opaque channels only also improved
the temperature profiles when clouds where included, but the influence of the
chosen cloud model was less important. We conclude that tropospheric
temperature profiles can be optimized by considering clouds in the microwave
retrieval, and that the choice of the cloud model has a direct impact on the
resulting temperature profile.
Citation
ID:
182166
Ref Key:
bernet2017atmosphericthe