Abstract
Radiosonde observations are the gold-standard for quantifying vertical
profiles of atmospheric state variables. Knowledge of which is critical
for quantifying moisture and instability, two main ingredients for
severe weather. Unfortunately, radiosondes are very sparse, averaging
just one observation per 500 x 500 km area over CONUS, and most
locations have only two observations per day. This creates uncertainty
in the representation of short wavelength and rapidly evolving synoptic
and mesoscale features in numerical weather prediction (NWP) and
provides few points of comparison for human forecasters to interpret NWP
in making forecasts. To fill this gap in our knowledge of the
atmospheric state, human forecasters make use of satellite imagery to
estimate airmass properties for incrementing NWP outputs. Data from
geostationary satellites have been especially useful because of its high
temporal resolution (5-minutes) and high spatial resolution (2 km).
While the Advanced Baseline Imager (ABI) was not designed as a sounding
sensor, the three water vapor bands and three infrared window bands do
provide some sounding capabilities. Satellite data are particularly
useful in assessing position and timing errors, the representation of
short waves, and humidity. The key question addressed by this work is
can the mental process used by human forecasters be translated into a
machine learning (ML) algorithm to provide automated and objective
estimates of airmass properties from ABI? Experiments with convolutional
neural networks (CNNs) show that ML can indeed be used. Related research
efforts, such as NOAA Unique Combined Atmospheric Processing System
(NUCAPS) has explored use of dense neural networks (DNNs), which are
essentially replacing a radiative transfer model with a ML model.
However, we find more skill can be achieved by making use of the spatial
information captured with CNNs. This more closely mimics the human
imagery interpretation process: it is the spatial patterns in the
features (as much as the pixel-wise values themselves) that carry the
useful information content. We will present our latest results, focusing
especially on relative humidity, compare against radiosondes, and
discuss whether skill is enough to potentially make a positive impact on
NWP analyses.