What are the climb rates during the different phases of flight of an A320? I have read about common climb rates for an A320. It is said that the initial climb rate for an A320 is between 15-20° and it differs depending on the weight and also the altitude.

I therefore have the following questions:


Do climb rates for a given flight mission stay constant in one phase of flight (e.g. until reaching 1500ft altitude) and then change at a specific flight level or are they continuously adjusted?
Do given climb rates exist for (one arbitrary) given flight mission?
Is there a method to calculate the change of climb rates depending on altitude and weight?
Are there sources like papers, reports, manuals that will work for genuine citation?
According to the EUROCONTROL Performance Database, the usual climb rates and speeds for an A320, for ATM purposes, are those depicted on the image below:



Source: https://contentzone.eurocontrol.int/aircraftperformance/details.aspx?ICAO=A320&amp;ICAOFilter=a320

Note that rate of climb (ROC) is given in feet per minute, not degrees. If measuring degrees, you are talking about the climb gradient, not climb rate.