On the temperature dependence of the cloud ice particle effective radius - a satellite perspective

Cloud ice particle effective radius in atmospheric models is usually parametrized. A widelyused
parametrization comprises a strong dependence on the temperature. Utilizing available satellite-based
estimates of both cloud ice particle effective radius and cloud-top temperature we evaluate if a similar
temperature-dependence exists in these observations. We find that for very low cloud-top temperatures the
modeled cloud ice particle effective radius generally agrees on average with satellite observations. For high
sub-zero temperatures however, the modeled cloud ice particle effective radius becomes very large, which is not
seen in the satellite observations. We conclude that the investigated parametrization for the cloud ice particle
effective radius, and parametrizations with a similar temperature dependence, likely produce systematic biases
at the cloud top. Supporting previous studies, our findings suggest that the vertical structure of clouds should
be taken into account as factor in potential future updates of the parametrizations for cloud ice particle effective
radius.