John Proni 1 John Wilkerson 2 1 NOAA-AOML (Emeritus). Currently at Applied Research Center, Florida International University, Miami, Florida 2 NOAA-NESDIS (retired)

Introduction The possibility of using underwater sound for the measurement of rainfall over the open ocean is receiving considerable attention today. In this presentation underwater sound and radar data recorded during the passage of three mesoscale convective systems over the area of Andros Island, Bahamas, in October of 1999 is discussed. The three systems are influenced by the passage of Hurricane Irene and appear to be entrained in the general wind flow pattern of the hurricane.

Raindrop Ocean Surface Bubble Sound Pressure Wave Time

Hurricane Irene storm track, through

H7 H12

Lag (Minutes) Correlation Coefficient

The underwater sound spectra recorded at the AUTEC range during the passage of hurricane Irene fell primarily into three categories: a) wind dominated, b) convective rainfall and c) stratiform rainfall. Scatter diagrams of the spectral amplitudes at 4kHz and 15kHz show the existence of a "closed loop" or observation cycle in the underwater sound measurements during the passage of three air-sea interaction/precipitation events over the measurement site (If the wind field changes over the site during the occurrence of the event the loop is not closed and the starting and end points are displaced by an amount proportional to the change in wind speed). The observation cycle of the underwater sound measurements can be interpreted in terms of the "life-cycle" put forward by Houze (1993) for mesoscale convective system complexes. Using the Houze life-cycle concept an estimate of the degree of maturity of the passing MCS can be made from the state of the underwater sound cycle. The same underwater sound life cycle has been observed at various sites including water depths as shallow as one meter to depths greater than one kilometer. Summary and Conclusions