What is lapse rate?

Hint:Lapse rate, in the sense of a gradual decline, derives from the word lapse.
It corresponds to the vertical portion of the temperature spatial gradient. While this term is most commonly applied to the troposphere of the Planet, it can be generalized to any parcel of gas that is gravitationally assisted.

Complete answer:
Definition –
The Lapse Rate is the rate at which the temperature in the atmosphere varies with height. The nomenclature of the lapse rate is inversely related to the shift itself; the temperature decreases with height if the lapse rate is positive; conversely, if negative, the temperature increases with height.
Mathematically,
The decrease, unless otherwise specified, of the atmospheric variable with height, the variable being temperature.
The lapse rate is usually the negative of the temperature change rate with altitude change:-



Types of lapse rate -
There are three kinds of lapse rates used to express the rate of altitude shifts, namely the rate of dry adiabatic lapse, the rate of wet adiabatic lapse and the rate of environmental lapse.
Dry Adiabatic lapse rate
The rate at which the air parcel temperature changes in response to a rise and/or compression of the altitude, assuming that the mechanism is adiabatic, is an adiabatic lapse rate (meaning that no heat is added or lost during the process).
The dry adiabatic lapse rate refers to the unsaturated air lapse rate (i.e., air with a relative humidity of less than 100 percent ). It is worth noting that the term 'dry' only means, in this sense, that no fluid water (i.e. moisture) can and is normally present in the air vapor.
Wet adiabatic lapse rate
An unsaturated portion of air will rise from the surface of Earth and cool at a dry adiabatic speeds of 9,8 K/km to the temperature of the atmosphere dew point where the vapor in it starts to condense (i.e. vapor to fluid transition phase) and release latent vaporization thermal fluid. The air parcel is saturated at that temperature and the rate of refreshment would drop to so-called wet adiabatic lapse rate due to the release of the heat from vaporization.
Environmental lapse rate
The lapse rate for the atmosphere (ELR) is the decline in heat at a certain place and time at the altitude in the stationary air. Both theoretical rates are the dry adiabatic discharge rate and the wet adiabatic wisdom rate. The actual real-world temperature-altitude profile at any given time and place is called the environmental lapse rate, also called the ELR. The predominant lapse rate or environmental lapse rate.

Note:Air stability is a name used to characterize the amount of vertical air movement in the lower atmosphere qualitatively (the troposphere). The atmospheric equilibrium can generally be distinguished by these four categories:-
1. The environment is very calm, with very little, if any, vertical air movement.
2. A stable environment discourages vertical movement but has some air movement.
3. An unstable environment facilitates constant vertical air movement up and down.
4. A neutral environment does not discourage or facilitate vertical air movement and is often called conditionally stable.