Estimation of UT1 Variations from Atmospheric Pressure Data

We have made an attempt to link Universal time 1 (UT1) variation with the pressure gradient in the upper atmosphere. These two regimes are linked via the geostrophic relation. We also introduce an index for the pressure gradient and check its feasibility for describing length-of-day (LOD) variation. Since we can easily obtain a rough picture of the atmospheric pressure field from daily weather charts, this method enables us to interpret the UT1 events in terms of the pressure field of the atmosphere. The obtained index shows a strong correlation with the AAM functions; this index can be used to estimate the UT1 variation. This method may be used to monitor the atmospheric conditions from geodetic observations.