tendency_of_atmosphere_mole_concentration_of_nox_expressed_as_nitrogen mol m-3 s-1 [MM3S] The phrase "tendency_of_X" means derivative of X with respect to time. "Mole concentration" means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical species or biological group denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". The phrase "expressed_as" is used in the construction "A_expressed_as_B", where B is a chemical constituent of A. It means that the quantity indicated by the standard name is calculated solely with respect to the B contained in A, neglecting all other chemical constituents of A. "Nox" means a combination of two radical species containing nitrogen and oxygen NO+NO2.