A semi-Lagrangian perspective of the lifecycle and interactions of deep convective clouds in geostationary satellite observations

The disparity in the increase in atmospheric water vapour and in the global energy budget with global warming is expected to lead to a greater contribution of precipitation from deep convective clouds (DCCs) to total precipitation. How this increase occurs is uncertain however; while many climate models predict that the intensity of precipitation in individual storms will increase while occurring at the same frequency, satellite observations of tropical cloud clusters have shown that the frequency of organised deep convective precipitation events is increasing. By studying the interactions between deep convective precipitation and the energy and water budgets, we aim to achieve a better understanding of how these budgets affect the intensity, frequency and organisation of deep convective clouds and the cloud feedbacks on subsequent convection.

 

The new generation of geostationary imaging satellites provides greatly improved observations of dynamic processes. Using optical-flow techniques, we show how a semi-Lagrangian perspective can be applied to GOES advanced baseline imager observations in the thermal IR spectrum, and how this perspective can improve our observations of the dynamics of DCCs. In this new perspective we are able to robustly track DCCs over their entire lifecycle. As a result, the interactions between energy budgets, organisation and growing convection can be linked to subsequent precipitation and radiative feedbacks over the entire lifetime of the DCC.

 

In a case study over the continental US, we observe a suppression of convective strength in the days following large, organised convective storms. Compared to similar DCCs prior to the large organised events, the subsequent DCCs develop more slowly and, despite having a similar maximum anvil cloud extent, have a shorter overall lifetime. Furthermore, the later anvil clouds and convective cores have warmer cloud top brightness temperatures by 10 K and up to 20 K respectively. We hope to gain a greater understanding of whether these changes are due to large scale dynamics associated with the large, organised convection or can instead be attributed to local cloud and thermodynamic feedbacks.