High-resolution (1 km) satellite rainfall estimation from SM2RAIN applied to Sentinel-1: Po River basin as a case study

[摘要] The use of satellite sensors to infer rainfallmeasurements has become a widely used practice in recent years, but theirspatial resolution usually exceeds 10 km, due to technologicallimitations. This poses an important constraint on its use for applicationssuch as water resource management, index insurance evaluation orhydrological models, which require more and more detailed information. In this work, the algorithm SM2RAIN (Soil Moisture to Rain) for rainfallestimation is applied to two soil moisture products over the Po River basin: ahigh-resolution soil moisture product derived from Sentinel-1, named S1-RT1,characterized by 1 km spatial resolution (500 m spacing), and a 25(12.5 km spacing) product derived from ASCAT, resampled to the same grid asS1-RT1. In order to overcome the need for calibration and to allow for itsglobal application, a parameterized version of SM2RAIN algorithm was adoptedalong with the standard one. The capabilities in estimating rainfall of eachobtained product were then compared, to assess both the parameterizedSM2RAIN performances and the added value of Sentinel-1 high spatialresolution. The results show that good estimates of rainfall are obtainable fromSentinel-1 when considering aggregation time steps greater than 1 d, sincethe low temporal resolution of this sensor (from 1.5 to 4 d over Europe)prevents its application for infer daily rainfall. On average, the ASCAT-derived rainfall product performs better than S1-RT1, even if theperformances are equally good when 30 d accumulated rainfall isconsidered (resulting in a mean Pearson correlation for the parameterizedSM2RAIN product of 0.74 and 0.73, respectively). Notwithstanding this, theproducts obtained from Sentinel-1 outperform those from ASCAT in specificareas, like in valleys inside mountain regions and most of the plains,confirming the added value of the high-spatial-resolution information inobtaining spatially detailed rainfall. Finally, the performances of theparameterized products are similar to those obtained with the calibratedSM2RAIN algorithm, confirming the reliability of the parameterized algorithmfor rainfall estimation in this area and fostering the possibility to applySM2RAIN worldwide, even without the availability of a rainfall benchmarkproduct.

[学科分类] 妇产科学