HR: 10:50h
AN: H52A-03    [Abstracts]
TI: Properties of Small-Scale Rainfall Spatial Correlation in Central Oklahoma
AU: * Ciach, G J
EM: g-ciach@uiowa.edu
AF: IIHR-Hydroscience & Engineering, The University of Iowa, , 100 Stanley Hydraulics Lab, Iowa City, IA 52242, United States
AU: Krajewski, W F
EM: witold-krajewski@uiowa.edu
AF: IIHR-Hydroscience & Engineering, The University of Iowa, , 100 Stanley Hydraulics Lab, Iowa City, IA 52242, United States
AB: Spatial variability of rainfall in the range of small scales between the size of a single raingauge (of the order of 0.1 m) and a few kilometers is an important problem from practical and as well as scientific points of view. For example, it is a source of fundamental difficulties in meaningful evaluation of radar rainfall estimates. Mathematical models of rainfall morphology have the capability to describe a broad span of spatiotemporal scales, however, their development and validation require adequate empirical evidence. Most of the experimental studies on spatial rainfall structure are based on the weather radar observations that are inherently averaged over areas ranging from about 4 km2 to 25 km2, and cannot provide information on finer scales. Therefore, spatial rainfall variability at the scales below a few kilometers is still a poorly explored research area. In this study, we present an extensive analysis of the small-scale variability in rainfall fields that is focused on their spatial correlation structure at the distances below 3-4 km. The correlation functions are well established, normalized and commonly used measures of spatial dependences that are required by many applications. In contrast to the multi-fractal measures, they can be estimated based on a network of point rainfall measurements. The correlation estimates presented here are based on a large data sample from a unique local cluster of 25 stations, called the EVAC PicoNet, covering an area of about 9 km2 in Central Oklahoma. High density of the network and relatively large size of the sample allowed us to look at the small-scale rainfield correlations from three different perspectives. First, we examined the dependences of the spatial correlation function on the time- scale for the averaging intervals spanning the range from 1 minute to 1 day. Second, we present and analyze the differences between the correlation estimates in the individual rainfall events. Finally, we demonstrate and discuss ambiguities associated with the conditioning of the correlation estimates on rainfall intensities.
DE: 1840 Hydrometeorology
DE: 1854 Precipitation (3354)
SC: Hydrology [H]
MN: 2007 Joint Assembly