Two decades variation about ionospheric parameters foF2, foE and M3000F2

The rules of ionosphere is important in the study of space weather, here three series of ionospheric vertical sounding stations locating in different latitude are selected, in the comparison of the time variations of Δ foF2, Δ foE, Δ M3000F2 during score years of two stations locating in the nearly same latitude, some rules have been found, some of which are not only attributed to the sun but also attributed to the troposphere.