Geomagnetic secular variation at Ebro Observatory during the past 70 years

The annual mean values of the geomagnetic field components observed at Ebro during 67 years from 1905 to 1972 are examined on the basis of a decrease of the geomagnetic dipole moment, a westward drift of the nondipole geomagnetic field and a northward shift of the geomagnetic dipole. A monotonous increase of X and Y and an early decrease and a recent very small secular change of Z at Ebro are mostly attributable to the westward drift of nondipole magnetic field of 0.3 deg/yr in the drift speed. It seems that increase of F since 1930 at Ebro can be attributed to both the westward drift of the nondipole field and the northward shift of the dipole.