Derivation of a 10-Year Radar-Based Climatology of Rainfall

Abstract

Weather radars give quantitative precipitation estimates over large areas with high spatial and temporal resolutions not achieved by conventional rain gauge networks. Therefore, the derivation and analysis of a radar-based precipitation ''climatology'' are highly relevant. For that purpose, radar reflectivity data were obtained from two C-band Doppler weather radars covering the land surface of the Netherlands ('3.55 3 10 4 km 2 ). From these reflectivities, 10 yr of radar rainfall depths were constructed for durations D of 1, 2, 4, 8, 12, and 24 h with a spatial resolution of 2.4 km and a data availability of approximately 80%. Different methods are compared for adjusting the bias in the radar precipitation depths. Using a dense manual gauge network, a vertical profile of reflectivity (VPR) and a spatial adjustment are applied separately to 24-h (0800-0800 UTC) unadjusted radar-based precipitation depths. Further, an automatic rain gauge network is employed to perform a mean-field bias adjustment to unadjusted 1-h rainfall depths. A new adjustment method is developed (referred to as MFBS) that combines the hourly mean-field bias adjustment and the daily spatial adjustment methods. The record of VPR gradients, obtained from the VPR adjustment, reveals a seasonal cycle that can be related to the type of precipitation. A verification with automatic (D # 24 h) and manual (D 5 24 h) rain gauge networks demonstrates that the adjustments remove the systematic underestimation of precipitation by radar. The MFBS adjustment gives the best verification results and reduces the residual (radar minus rain gauge depth) standard deviation considerably. The adjusted radar dataset is used to obtain exceedance probabilities, maximum rainfall depths, mean annual rainfall frequencies, and spatial correlations. Such a radar rainfall climatology is potentially valuable for the improvement of rainfall parameterization in weather and climate models and the design of hydraulic structures.

Country-wide rainfall maps from cellular communication networks

“…The quality of a similar radar dataset for another period was found to be high, enabling to derive extreme areal rainfall statistics (31)(32)(33). For the calibration, a radar dataset of path-averaged rainfall intensities over each link was constructed (8).…”

Opportunities for multivariate analysis of open spatial datasets to characterize urban flooding risks

“…Rainfall depths, observed at 1.5 km above the ground, are provided with a temporal resolution of 5 min, on a grid of 1 km 2 spatial resolution with a custom geographic projection (Overeem et al, 2009). Information is available through a FTP server.…”

Decision-tree analysis of factors influencing rainfall-related building structure and content damage

“…A database of C-band weather radar images was used, provided by the Royal Netherlands Meteorological Institute (Table 1). The images are composites based on two C-band Doppler radars, which have been adjusted for various biases using data from manual and automatic rain gauges (Overeem et al, 2009). The rainfall-related variables were obtained using the following steps, as is also described in Spekkers et al (2013b).…”