Formation and Attributes of Cumulus Clouds

First uploaded on 2026/01/28
Last updated on 2026/01/31
Copyright(C)2026 jos <jos@kaleidoscheme.com> All rights reserved.

We have explained the RDC scheme, which is a transport process from cumulus domains to their surroundings. However, the current version of the RDC scheme does not address how cumulus clouds themselves would form and what attributes they would have, instead leaving it entirely to existing models. For an ideal research development, it seems we implicitly assumed analyses in cumulus-resolving models for the RDC scheme use, similar to our original study using a simple 2D radiation-convection model DCM. This is because the formation and attributes of cumulus clouds are most reliable whey they are obtained from these models with least ambiguities and external assumptions.

Within a cumulus-resolving model, cumulus clouds form and all their internal physical attributes are determined, according to the model's equations of motion. Therefore, when applying the RDC scheme, these can be used as-is. Furthermore, outflow from cumulus domains to their surroundings is actually computed within the model itself. This allows comparison with the outflow when the RDC scheme is applied, enabling us to ultimately verify the correctness of the RDC scheme.

On the other hand, users of models that do not explicitly compute cumulus formation may find the RDC scheme incomplete. This is because formation and attributes of the cumulus clouds are determined by the model's assumptions which are not related to the RDC scheme. In this case, the physical processes assumed by the model and the RDC scheme may not be fully consistent. However, even then, as explained in the latter part of the explanation page, it is possible to balance the mass flux throughout the entire atmosphere by connecting the two calculations via the net upward mass flux at the cloud base, for example. And at the very least, it should be possible to compare the cumulus detrainment flows between the conventional model calculation and the RDC scheme calculation, presenting the differences.

As stated above, we are currently proposing the RDC scheme as a transport process from cumulus clouds to their surroundings. We consider verifying this process to be the top priority. This is because this process determines the distribution of water vapor in the atmosphere and is climatologically significant.

Our next task is to predict the formation and attributes of cumulus clouds from the RDC perspective. Ideally again, this task will hopefully performed using the cumulus-resolving model. This new analysis should enable us to determine conditions from not only the convergence of large-scale dynamical fields, but also the thermodynamic balance considering RDC within each RDC-partition and the local convective instability. This is neither a matter of trial and error nor parameter tuning, but rather an inevitable process guaranteed by basic thermodynamic relationships. Those with a rich imagination will understand that, when based on the thermodynamic principles underlying this RDC scheme, we have a great potential to describe the radiative-convective system completely, or at least with the precision required for climate prediction, using fundamental physical laws, not reproducing phenomena as has been done previously. Due to the bounding of flows and energy by thermodynamic relationships, physically impossible flows or runaway energy balances do not occur, even when used for long-term climate predictions. This is highly exciting work, and we are eager to participate with strong interest.

[NOTE]
Although the tropical region is a convergence zone on a global scale, the formation of individual cumulus clouds in this region is thought to be directly related to local convective instability and thermodynamic balance rather than large-scale dynamic convergence. These relationships are more likely to be established based on the RDC scheme than based on any other physics.

[NOTE]
Research on RDC and cumulus formation does not require expensive, realistic global atmospheric models. Rather, as in our original studies, using a simple radiative-convective model with a box-like domain makes it easier to extract the relationship between the two. When we are provided with an environment where we can focus on the research, this analysis using our DCM as an extension of our previous work will be the first subject of our own. We will be able to discuss the differences in atmospheric geometries between 2D and 3D as well.

Once we can predict cumulus formation, the RDC scheme will be perfected. Thereafter, it will be possible to perform climate projections by integrating the coarse-resolution atmospheric model with the RDC scheme built in over long periods, rendering costly high-resolution cumulus-resolving models unnecessary. We do not believe that detailed computations of fine turbulent vortices within cumulus clouds in order to calculate Dynamical Detrainment are necessary for climate prediction.

Thus, demonstrating that cumulus detrainment flow can be represented by the RDC scheme within an atmospheric model is our current goal and the starting point for everything. Even if you don't have an atmospheric model to verify the RDC scheme, we will build a simple 3D radiative-convective model, with explicit treatment of cumulus convection, from scratch, if we are given the development environment. We hope many researchers will take an interest in the RDC scheme and join this project.