Uncertainties characterization of tropospheric profile retrieval by
Bayesian inversion as compared to state-of-the-art methods from
ground-based microwave radiometry
Abstract
Ground-based microwave radiometry is a common tool to estimate profiles
of the atmosphere. With a high temporal resolution radiometers have
became an alternative to atmospheric sounding like radiosondes. However
remote sensing radiometry requires the use of inversion algorithms,
where methods like linear-, quadratic-regression or Artificial Neural
Network are commonly used. The present study implements a Bayesian
inversion technique as alternative to the state-of-the-art retrieval
algorithms provided by the radiometer’s manufacturer firmware. The
Bayesian inversion provides advantages over other established methods,
namely: the use of a-priori suited for the specific climatology under
observation, the estimation of the most likely profile along with its
uncertainty obtained from the posteriori distribution, and the
feasibility to add synergistic observations from other instruments to
increase retrieval capabilities. To estimate the uncertainties resulting
from the Bayesian and firmware retrieval algorithms, synthetic
radiometer data have been created by means of radiative transfer
simulations using radiosonde profiles as descriptor of atmospheric
states. These synthetic data mimics the instrument’s firmware binary
files letting the radiometer to perform retrievals as real measurements.
By analyzing the differences from retrieval results relative to the
known true profile we assess uncertainty metrics to characterize the
algorithms. It has been found that Bayesian inversion reproduces more
accurately the profile vertical structure as compared to the firmware,
specially for humidity profiles. Absolute errors have been strongly
reduced mainly at the lower atmosphere. The study concludes that
Bayesian inversion for ground-based atmospheric profiling produces
results resembling observations by radiosondes when a suitable a-priori
distribution is used.