The atmosphere's electric field strength in volts per meter at any specified point in time and space near the Earth's surface and in fair-weather areas: A typical datum is about 100 and the field is directed vertically in such a way as to drive positive charges downward.

An atmospheric electric field is a quantitative term indicating the electric field strength of the atmosphere at any specified point in space and time.
An atmospheric electric field is also a measure, in volts per meter, of the electrical energy in a given portion of the Earth's atmosphere at a given time.