A better understanding of the many interacting processes governing the
evaluation of ice in natural clouds is required to improve the
representation of ice clouds in global circulation models. Recent
studies suggest a dominant role of vapor growth processes in determining
the temperature dependence of cloud top ice sizes and shapes. Using
airborne cloud remote sensing along with reanalysis data, here we show
that observed cloud top ice effective radii and estimated normalized
growth rates at cloud top highly correlate with an approximately linear
relationship, which is consistent with a conceptual model also
presented. Furthermore, significant differences in crystal shape
characteristics and scattering asymmetry parameters are found between
sub- and super-saturated cloud tops over ocean, although not over land.
These results provide valuable observational targets for studying ice
formation and evolution processes using models, while also helping
interpretation of satellite observations of ice microphysical properties
at cloud tops.