Abstract
Imagery from the GOES series has been a key element of U.S. operational
weather forecasting for four decades. While GOES observations are used
extensively by human forecasters for situational awareness, there has
been limited usage of GOES imager data in numerical weather prediction
(NWP), and operational data assimilation (DA) has ignored cloud and
precipitating pixels. The motivation of this project is to bring the
benefits of GOES-R Series enhanced capabilities to advance
convective-scale DA for improving convective-scale forecasts. We have
developed a convolutional neural network (CNN) prototype, dubbed “GOES
Radar Estimation via Machine Learning to Inform NWP (GREMLIN)” that
fuses GOES-R Advanced Baseline Imager (ABI) and Geostationary Lightning
Mapper (GLM) information to produce maps of synthetic composite radar
reflectivity. We find that the ability of CNNs to utilize spatial
context is essential for this application and offers breakthrough
improvement in skill compared to traditional pixel-by-pixel based
approaches. Making use of ABI spatial information potentially provides
benefits over radiance assimilation approaches that are limited by
saturation of radiances in pixels with precipitation. This presentation
will briefly describe the GREMLIN model and characterize its performance
across meteorological regimes. We are developing a dense neural network
(DNN) to produce vertical profiles of radar reflectivity and latent
heating based on the two-dimensional fields output from GREMLIN. The
resulting three-dimensional fields of latent heating will be used to
initialize NWP simulations of convective-scale phenomena. Another DNN
will be developed to produce uncertainty estimates of latent heating for
each pixel. Our approach for data assimilation will be described and is
innovative in being the first-time machine learning (ML) will be used
for the nonlinear latent heating observation operator in the NOAA hybrid
Gridpoint Statistical Interpolation (GSI) and/or JEDI systems. The
approach will provide all the elements of the Jacobian needed for GSI DA
and has the advantage of automatically maintaining the tangent linear
and adjoint models through finite difference mathematics.