Methodology Exists, But No Principle

First uploaded on 2023/02/07
Last updated on 2025/04/01
Copyright(C)2022-2025 jos <jos@kaleidoscheme.com> All rights reserved.

[NOTE]
This article is based on our interpretation for the Dynamical Detrainment (DD). The interpretation might be old, since we have not updated our understanding on DD due to lack of research environment. However, unless there have been very drastic changes in the DD constitution, the following statement would be still correct.

Dynamical Detrainment (DD) attempts to explain transport from within the cumulus to the clear-sky outside by an ensemble of chimney-type convection models. And people are looking for how this ensemble should be made. In other words, DD has a methodology, but has no principle yet. This is a very rare case in science where methodology precedes principle. However, there is only one such field of science, which makes heavy use of methodology over principle. That is weather forecast.

In weather forecasting, the goal is not to understand the principle, but to predict the state of the atmosphere in the near future. Therefore, for example, if one can predict a weather phenomenon by considering an appropriate polynomial and tuning the coefficient values that appear in the polynomial, it is a right approach in weather forecasting, even without understanding the physical meanings of the polynomial and the coefficient values. The polynomial and the coefficient values themselves can be the final product.

However, this is possible because the weather is repeating and can be experienced and observed many times. Both of the parameter tuning and the prediction application assume that the phenomenon appears many times repeatedly. On the other hand, climate change is at least not repeatable like weather change. It might not be wrong to look to past events for clues, looking for much longer cycles in which the climatic states vary. But there is no guarantee that the same thing will happen in the case of the current global warming caused by human activity, which must be the first event on the Earth.

Therefore, just because one could reproduce the current climate condition based on a certain methodology is no guarantee that it will correctly predict future climate conditions. Only when the reproduction is based on logically correct physical principles can it be credible. What we should seek first for climate prediction is not a methodology but a physical principle. It is a mistake to apply weather forecasting methods directly to climate prediction. It will lead to still better weather forecasting and to nothing for climate predictions.

Before starting with the methodology for representing motion, we must first examine whether the motion is physically permissible. The DD method assumes upward mass flux supplied from the cloud base distributed into horizontal mass fluxes at some altitudes. This is a kind of linear theory, assuming laminar flows. Cumulus convection occurs, however, to resolve convective instability in the atmosphere. The convective instability is resolved by the entrainment of the rising hygrothermal (water-vapor and heat) plume with the surrounding atmosphere. This is essentially a mixing process, which is NONLINEAR. i.e., dynamically speaking, the upward mass flux supplied from the cloud base is immediately converted into USELESS mixing turbulence, which cannot rise constantly or branch arithmetically into horizontal mass flux at any altitude. As far as DD is concerned, it is a mistake to think that the second law of thermodynamics allows small physical-scale mixing turbulent flows within the cumulus to be integrated into large flows moving outward from the cumulus. In the cumulus convection, dynamical entrainment, namely mixing, certainly occurs, but dynamical detrainment, which is just a play on words opposite to entrainment, never does. Although the DD method seems to provide answers as you work, there is no physical basis for this methodology.

RDC contrasts with DD in the relationship of principle and methodology. RDC can be derived in an equilibrated atmosphere from local thermal balance and local mass continuity which are rigid physical bases of thermodynamics and fluid dynamics. Furthermore, the RDC has a broad clear-sky spatial scale outside the cumulus and a long time scale of radiative cooling, which does not violate the second law of thermodynamics. We believe RDC is one of the physical principles that describes global warming, because we have not found by ourselves any logical failure in it. Now we are presenting the way next, the RDC scheme, the methodology to incorporate RDC into the climate prediction models. We hope that RDC will be of interest to those working with 3D atmospheric climate models.

[NOTE]
You might question RDC because the atmosphere is not always in equilibrium. It is sufficient to treat the model atmosphere separately into mean components (actually the equilibrium components) and disturbance components, and apply the RDC scheme only to the mean components. The disturbance components can be correctly treated in the conventional way by the existing equations of motion in the model.