Improving prediction of marine low clouds using cloud droplet number
concentration in a convolutional neural network
Abstract
Marine low clouds significantly cool the climate, but predicting these
clouds remains challenging: the response of these clouds to various
factors is highly non-linear. Previous studies usually overlook the
effects of cloud droplet number concentration (Nd) and the non-local
information of the target grids. To address these challenges, we
introduce a convolutional neural network model (CNNMet-Nd) that uses
both local and non-local information and includes Nd as a
cloud-controlling factor to enhance the predictive ability of cloud
cover, albedo, and cloud radiative effects (CRE) for global marine low
clouds. CNNMet-Nd demonstrates superior performance, explaining over
70% of the variance in these three cloud variables for instantaneous
scenes of 1°×1°, a notable improvement over past efforts. CNNMet-Nd also
accurately replicates geographical patterns of trends in marine low
clouds from 2003 to 2022. In contrast, a similar convolutional neural
network model without Nd input (CNNMet) fails to predict global mean
cloud properties effectively, underscoring the critical role of Nd.
Further comparisons with an artificial neural network (ANNMet-Nd) model,
which uses the same inputs but without considering spatial dependence,
show CNNMet-Nd’s superior performance with R2 values for cloud cover,
albedo, and CRE being 0.16, 0.11, and 0.18 higher, respectively. This
highlights the importance of incorporating non-local information into
low cloud predictions to enhance climate model parameterizations.