Do detrained cirrus clouds have memory of the deep convection they came from?

The large cirrus outflows that arise from deep convection play a vital role in modulating the energy balance of the Earth’s atmosphere. One important question is how much do the initial conditions of the deep convection influence the subsequent evolution of the detrained cirrus, and if these initial conditions are important, over what timescales do they matter? Characterising how these cirrus outflows evolve over their entire lifetime, and how they might change in response to anthropogenic emissions is important in order to understand their role in the climate system and to constrain past and future climate change.

Building on the ‘Time Since Convection’ product used in Horner & Gryspeerdt (2023), this work investigates how the initial conditions of the deep convection influence the subsequent evolution of the detrained cirrus- in particular, how does the timing, location, and meteorological environment of the deep convection alter the detrained cirrus, and for how long are these initial conditions important for the cirrus properties- is there a ‘memory’ of the initial conditions of the deep convection imprinted on the properties of the cirrus hours or days after the initial deep convection has dissipated? To answer this question, data from the DARDAR, ISCCP, and CERES products are used to build a composite picture of the radiative and microphysical properties of the clouds, which is investigated under varying initial conditions.

The initial state of the convection is found to have a considerable impact on cirrus development under a variety of conditions. The diurnal cycle, particularly the timing of the convection, is a strong control on the cloud radiative effect, particularly in regions of strong convective activity. The initial aerosol perturbation is also shown to play a role in cirrus development, both in the large scale properties of the cirrus and the microphysical properties.

This demonstrates a potential time dependent impact of aerosol and convection on cloud properties and provides a template for future studies of cloud development incorporating diverse sets of measurements.