Inverse Barometer Coefficients Obtained at Short Time-scales from ERS Tandem Mission Altimeter Data

Abstract

Altimeter data from the tandem mission of tile European Remote sensing Satellites, ERS-1 and ERS-2, are used to study the validity of the Inverse Barometer (113) correction oil a near-global spatial-scale, and at time-scales as short as 2 days (Nyquist period). 113 regression coefficients calculated from differences between corresponding pairs of Sea Surface Height (SSH) anomalies and calculated Air Pressures (AP) from the two satellites yield departures up to -0.6 cm/mbar in the tropics. This magnitude of departure has previously been shown in an analysis of tide gauge data. In the tropics a clear trend is apparent, from the largest departures at short time-scales, to IB-like results at periods around 20-30 days. Outside the tropics the response behaves largely like an inverted barometer. Use was also made of a next pass analysis technique performed separately for ERS-1 and ERS-2, using data only during the tandem mission phase. The approximate sampling interval is 16 days (32 days Nyquist period) for the ERS 35-day repeat cycle. Results also compare well to previous studies using tide gauge and numerical model data at these time-scales. Departures in the Southern Ocean are apparent in the ERS analyses though are not as large as results from TOPEX data.