PI/Institution: Nystuen / UW Proposal No: OCE-0241245 PI/Institution: Anagnostou / UConn Proposal No: OCE-0241552 PI/Institution: Amitai / UMBC Proposal No: OCE-0241186
The inherent spatial and temporal variability of rainfall makes rain one of the most difficult geophysical quantities to measure anywhere, and yet it is one of the most important. Acoustic rain gauges (ARGs), which detect and measure rainfall rate by listening for the underwater sound signal generated by rain striking the ocean surface, can provide these data in oceanic regions. However, there are several features of the acoustic rainfall measurement that have not been fully explored. These include the inherent spatial averaging of the rainfall signal with depth of deployment, the ability to measure drop size distribution in the oceanic environment, and the high temporal resolution of the measurement. We propose to examine the inherent spatial averaging associated with ARGs by deploying several vertically separated ARGs on a mooring placed in deep water (2 km), but within range of a high-resolution X-band polarimetric (X-POL) coastal weather radar (less than 40 km). A dense (~20 gauges) rain gauge network will also be installed within a 40 km range of the radar to provide a comparison validation of the radar data. A two-dimensional video disdrometer will be installed at closer range (~5 km) to be used for polarimetric algorithm development and evaluation of the X-POL measurements. The X-POL rain estimates will be used to validate the acoustic measurement of drop size distribution and the subsequent classification of rainfall type. The spatial distribution of rainfall over the hydrophones will be used to predict the received acoustic signal as a function of depth. The proposed field experiment will permit for the first time a comprehensive investigation of underwater acoustic rainfall measurements with a high-resolution radar, thus allowing an examination of the deep-water (open sea and oceans) validation potential of acoustic measurements for remote sensing (radar and satellite) rainfall estimates. Validation of oceanic rainfall measurements is an important component of climate research and the predictability of climate change with its subsequent impact on human societies. This will be a collaborative effort between 3 universities and the National Observatory of Athens (Greece), thus building global science and engineering infrastructure. Human resource development will include student participation in both field measurements and associated research.
