Atmospheric Tidal Variations within the ERICA Drifting-Buoy Data

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  • 1 Department of Physics and Atmospheric Science, Drexel University, Philadelphia, Pennsylvania
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The impact of atmospheric tides on surface pressure is studied by analyzing observations from the drifting-buoy network in the northwest Atlantic Ocean in winter 1988/89. These small, relatively inexpensive buoys, deployed for the Experiment on Rapidly Intensifying Cyclones over the Atlantic (ERICA), reported 10-min averages of air pressure, temperature, and sea surface temperature through satellites. Tidal oscillations are evident within the pressure variations and these tidal variations can be extracted and analyzed because they have a known constant period. The analyzed tides are compared with past observations and the similarities and differences are discussed. Many of the differences are attributed to the absence of local forcing in the homogeneous ocean environment, suggesting that the global-scale tide is being represented well. In this context, the observed variations agree well with what is expected, which demonstrates that the ability of the buoys to measure temporal changes is, on average, quite good. In addition, though the spatial gradients of tidal surface pressure variations at sea are negligible for most purposes, the magnitude of the temporal pressure variations are as large as 1 mb (3 h)−1, which is significant compared to the 3 mb (3 h)−1 indicative of rapid storm development. The different treatment of tide-producing mechanisms in different numerical prediction models may also complicate inter-comparison of pressure changes over a few hours in global models versus regional models.

Corresponding author address: Robert A. Cohen, Department of Physics and Atmospheric Science, Drexel University, Philadelphia, PA 19104.

The impact of atmospheric tides on surface pressure is studied by analyzing observations from the drifting-buoy network in the northwest Atlantic Ocean in winter 1988/89. These small, relatively inexpensive buoys, deployed for the Experiment on Rapidly Intensifying Cyclones over the Atlantic (ERICA), reported 10-min averages of air pressure, temperature, and sea surface temperature through satellites. Tidal oscillations are evident within the pressure variations and these tidal variations can be extracted and analyzed because they have a known constant period. The analyzed tides are compared with past observations and the similarities and differences are discussed. Many of the differences are attributed to the absence of local forcing in the homogeneous ocean environment, suggesting that the global-scale tide is being represented well. In this context, the observed variations agree well with what is expected, which demonstrates that the ability of the buoys to measure temporal changes is, on average, quite good. In addition, though the spatial gradients of tidal surface pressure variations at sea are negligible for most purposes, the magnitude of the temporal pressure variations are as large as 1 mb (3 h)−1, which is significant compared to the 3 mb (3 h)−1 indicative of rapid storm development. The different treatment of tide-producing mechanisms in different numerical prediction models may also complicate inter-comparison of pressure changes over a few hours in global models versus regional models.

Corresponding author address: Robert A. Cohen, Department of Physics and Atmospheric Science, Drexel University, Philadelphia, PA 19104.
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