## 1 Introduction
LDA is particularly important for improving the weather forecast over the Mediterranean Sea, considering that the ground-based radar coverage is not enough for monitoring weather systems more than 100-150 km away from the radar position and the evolution of weather systems over the Mediterranean Sea is partially unobserved by the Italian radars. For this reason, the impact of radar data assimilation over the Mediterranean Sea is limited and LDA plays a significant role in improving the weather forecast. Thanks to the advent of the international Global Precipitation Measurement (GPM) mission [67; 68], a new set of global precipitation products has become available for the meteorological scientific community. The GPM satellite constellation is made up of an ever-growing number of low-Earth-orbit (LEO) satellites equipped with cross-track and conical passive microwave (PMW) radiometers. The main satellite of the constellation is the NASA/JAXA (National Aeronautics and Space Administration/Japan Aerospace Exploration Agency) GPM Core Observatory (GPM-CO), which carries the most technologically advanced radiometer, the GPM Microwave Imager (GMI), and the dual-frequency Ku/Ka-band precipitation radar (DPR). The potential of the GPM constellation to analyze precipitation systems over the Mediterranean region (land and sea) has been demonstrated in several studies [69]. For instance, [PERSON] et al. [70] demonstrated the value of using precipitation retrievals from the GPM constellation for monitoring the evolution of different severe weather systems, in particular over sea regions or coastal areas with complex orography. On the other hand, [PERSON] et al. [62] showed the capabilities of a single GPM-CO overpass over a violent hailstorm that developed offshore in front of Naples to capture in fine detail basic characteristics of the exceptional event, which was completely missed by numerical weather forecasting models. Furthermore, making use also of RAMSmodel forecasts, [PERSON] et al. [64] documented how the PMW and DPR data from the GPM constellation can be fruitful to analyze the life cycle of the tropical-like cyclone (TLC) Numa, which developed on the Ionian Sea during 15-19 November 2017. Apart from the insight that the information from these space-borne platforms provides for the study of individual weather events, the combination of the different sensor measurements offers unique and consistent precipitation estimations, which, combined with geosynchronous Earth orbit (GEO) infrared (IR) observations over the globe, provide precipitation products of unprecedented high spatial and temporal resolutions across the globe, such as the Integrated Multi-satellite Retrievals for GPM (IMERG) [71]. In this paper, we focus on the impact of LDA on the short-term (3 h) precipitation forecast over the Mediterranean Sea using the WRF model. The rainfall forecast is verified against the IMERG dataset (Final Run) and by the rain gauge precipitation recorded at six stations located over small islands around the Italian peninsula. The paper is organized as follows: In Section 2, we introduce the WRF model configuration and the IMERG dataset. Section 3 shows the results comparing the WRF precipitation forecast, with or without LDA, with the data from IMERG and from the rain gauges located in small Italian islands in the central Mediterranean Sea. Conclusions are reported in Section 4.