What is atmospheric heat ?

The heat energy of a gas is proportional to the temperature of the gas and the amount (moles, mass, whatever) of the gas. That would be the "U" term in Climate Realist's equation. For the atmosphere you can think of temperature as being proportional to the average molecular kinetic energy of the gas.

Unless you're talking about a plasma, then the "speed of the electron", and its orbital angular momentum are not really relevant to the heat energy of the gas, except at high temperatures. At high temperatures then electrons may start being ionized. The Saha equation will tell you the degree of ionization, but at temperatures in the troposphere the amount of ionization is VERY small.

Temperature is NOT the accumulation of heat--you can have very little "heat" while having a very high temperature. That would be the case for example in the Earth's thermosphere.

Heat Transfer The Source of heat for our planet is the sun. The Sun's energy moves through space, then through the earth's atmosphere and finally reaches the earth's surface. The sun's radiation warms the earth's atmosphere and surface and becomes heat energy. This heat energy is transferred through the atmosphere by one of the three mechanisms:

1. Radiation

2. Conduction

3. Convection

Enthalpy is the correct term.

H = U + P * V

Heat is energy in flux, driven by a difference in temperature.