Micro-scale orographic precipitation and land feedback in a case study: Microscale precipitation variations and importance to climate adaptation

Abstract Submission: That land feedback affects local precipitation intensity, duration, and frequency (IDF) is well known. Orographic precipitation in rain shadows affecting regional IDF variations were reported on the western slope of Sierra Nevada Mountains, coastal plains of Blue Ridge Mountains, around the Great Lakes, and in the Chesapeake Bay coastal region. At local micros-scales, however, land feedback and orographic precipitation affecting IDF curves and hydrological designs have not been examined. Yet they are important to the effectiveness of hydraulic and environmental systems such as those for combined sewer overflow (CSO) controls. In this study, we examined the spatial IDF variations using 12 years of high-resolution gage-adjusted radar precipitation data in the Cincinnati area and compared the results against NOAA’s Atlas-14 design precipitations that are spatially interpolated from observations of limited climate stations. Our IDF curves from radar data, aggregated at 5-min temporal resolution, show large spatial variations of high-frequency design precipitation (e.g., 5-min and 30-min 2-year and 5-year storms) throughout stormwater sewersheds. Compared to the Atlas-14 design values, higher design precipitations are found along the segments of Ohio River channels, along the western hill side of Milk Creek valley, and large and sloped forest areas in western Hills, Mt Airy, and Indian Hills along the Little Miami River. Smaller design precipitations are found in the highly urbanized areas of man-made surfaces. The spatial correlations revealed in GIS spatial analysis suggest orographic precipitation and land feedback as important climate forcers affecting hydrologic design and operation of the CSO control systems.

Disclaimer: The views expressed in this abstract are those of the authors and do not necessarily represent the views or the policies of the U.S. Environmental Protection Agency; therefore, no official endorsement should be inferred.

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