*2.1. Radar MPE Dataset*

NEXRAD (Next-Generation Radar) is a network of more than 160 high-resolution S-band Doppler weather radars operated by the US National Weather Service (NWS). The NEXRAD system provides high-quality, high-resolution precipitation estimates for a wide range of hydro-meteorological applications [19]. Starting in 2002, the NWS implemented a processing algorithm called the Multisensor Precipitation Estimator (MPE) [1], which is currently used at the NWS River Forecast Centers (RFC) to produce a set of regional rainfall products using single- or multi-sensor analysis techniques. However, radar-based estimates can be highly uncertain due to a number of sampling and algorithm factors e.g., [20–22]. Therefore, the MPE algorithm applies bias-correction and co-Kriging optimal merging techniques using gauge reports [1,23].

The specific radar product used in this study is the operational product produced at the NWS Lower Mississippi River Forecast Center (LMRFC). This product is developed using the MPE algorithm, but also benefits from manual adjustments by human forecasters [22,24,25]. The MPE product has an hourly resolution and projected spatially using the Hydrologic Rainfall Analysis Project (HRAP) grid [26], with an approximate pixel size of 4-km x 4-km. The domain of the current study covers the entire state of Louisiana in the south-central US. With proximity to the Gulf of Mexico, different synoptic weather patterns are responsible for extreme events over Louisiana, including tropical storms, fronts, and convective air mass thunderstorms [27]. For the purposes of this study, the radar pixels covering Louisiana were extracted from the full LMRFC MPE product, resulting in a matrix with a total number of pixels of (180 × 140). The dataset comprises a total of 11 years covering the period of 2002–2012. To perform a precipitation frequency analysis, the annual maximum series (AMS) were extracted over each of the (180 × 140) radar pixels, resulting in a sample composed of a spatial field of 11 maxima representing the maximum hourly rainfall during 2002–2012 at each 4-km × 4-km pixel within the study domain.
