A case study of precipitation along the winter storm track in the North Pacific based on the GPM and ERA5 data

The North Pacific storm path has an important impact on the global climate. Studying the structure of regional precipitation along the North Pacific storm path will help better understand the role of the storm path in transporting water vapor and heat to the global atmosphere. Base on the GPM data and the fifth generation reanalysis data (ERA5) from European center for medium range weather forecasts (ECWMF), taking an extratropical cyclone event that occurred in the storm track area of the North Pacificfrom December 20 to 24 in 2014 as an example, we analyzed the characteristics of precipitation and cloud parameter structures for three precipitation segments brought by thiscyclone. The results show that the synoptic conditions of the three precipitation segments are similar, and their water vapor distributions are different from the north to the south, resulting in different distributions of water vapor flux divergence, which makes the precipitation intensities in the three segments different. The precipitation is concentrated in the southeast side of cyclone center. By comparing the relationship between precipitation intensity and water vapor content in extratropical cyclones, it is found that more precipitable water does not necessarily lead to greater precipitation intensity, but the column integrated water vapor content determines the upper limit of precipitation intensity. There are evident conversion layers of ice water in the vertical cross-sections of the reflectivity in the three precipitation segments, and the distribution of ice water conversion layers in each segment is different. According to the particle spectra of three precipitation segments obtained by dual frequency rain radar (DPR), the intensity distribution of effective particle radius of each segment is in good agreement with that of the reflectivity, while the distribution of particle number concentration is not consistent with the former two. The mechanism remains to be studied in future. The fusion of the GPM and ERA5 data can better reflect the synoptic conditions before and after the precipitation event on the North Pacific storm path, so as to explain its precipitation distribution, which can provide a reference for precipitation study in the areas of lacking ground observation data.