Introduction
The Ocean Rainfall And Ice-phase precipitation measurement Network (OceanRAIN) provides in-situ along-track shipboard data of precipitation, evaporation and the resulting freshwater flux in 1-min resolution over the global oceans. All routinely measured atmospheric and oceanographic state variables along with those required to derive the turbulent heat fluxes are included.
The precipitation parameter is based on measurements from the optical disdrometer ODM470 that is specifically designed for all-weather shipboard operation. The rain, snow and mixed-phase precipitation occurrence, intensity and accumulation are derived from particle size distributions (PSD). Additionally, microphysical parameters and radar-related parameters are provided.
OceanRAIN-1.0 contains 73 parameters plus number concentration and raw count PSD data in 128 size bins. The time period from 06/2010 to 04/2017 comprises more than 6.83 million minutes of data from eight ships with precipitation observed in about 10% of the time. The research vessels sail the global oceans during all seasons, avoiding the fair-weather bias and thus covering the entire spectrum of weather events. OceanRAIN provides users with three dataset versions for each of the eight ships in the OceanRAIN fleet. The aim is that users can choose the dataset version that best meets their research needs. The along-track point data covers the global oceans from -90° to 90°N latitude and -180° to 180°E longitude from 10 June 2010 to 10 April 2017. The files are named following the convention OceanRAIN-id_RV-ship-name_ship-identifier_UHAM-ICDC_startdate-enddate_v1_0 with .nc or .ascii as file extension.
OceanRAIN provides in-situ water cycle surface reference data for satellite product validation and retrieval calibration of the GPM (Global Precipitation Measurement) era, to analyze the point-to-area representativeness of precipitation and to improve our understanding of water cycle processes over the global oceans. Moreover, the data can be applied to evaluate re-analysis and climate model data.
Available OceanRAIN-1.0 data products are:
OceanRAIN-W: The OceanRAIN-W contains the 1-minute resolution water cycle components of evaporation, precipitation and the freshwater flux along with all meteorological and oceanographic state variables required to derive these fluxes. The dataset is continuous in time and contains 73 parameters and 6.830365 million minutes of data. Typical applications for OceanRAIN-W comprise process studies and statistical analysis as well as satellite validation and re-analysis or model evaluation. OceanRAIN point data can serve as the surface reference and can be collocated with satellite or model data to analyse and improve their error characteristics. Therefore, it is important to highlight that the RVs sampled on the global oceans during all seasons including the cold-season Southern Oceans.
OceanRAIN-M and OceanRAIN-R: OceanRAIN-M and OceanRAIN-R focus on minutes containing precipitation and are therefore discontinuous in time. Both datasets comprise 37 precipitation-relevant parameters plus the 128 size bin number concentration PSDs (OceanRAIN-M) and raw number count PSDs (OceanRAIN-R) for 696,740 minutes in total with rain, snow or mixed-phase precipitation. The precipitation-related parameters are identical in the three versions of the dataset. Applications for these datasets especially comprise satellite retrieval performance evaluation for liquid and solid precipitation. For this purpose, OceanRAIN-M and OceanRAIN-R supply the user with a convective versus stratiform precipitation classification and contain the main PSD characteristics and the radar reflectivities at important frequencies for radar rainfall studies. This is of special importance for users aiming at TRMM, CloudSat and GPM product and retrieval validation because these satellite missions carry spaceborne radars.
The OceanRAIN version 1.0 datasets are freely available as netCDF and ascii files from the repositories of the World Data Center for Climate (WDCC) at the German Climate Computing Center (DKRZ).
For further information about accessing OceanRAIN-1.0 data at WDCC, please refer to the ››Data Access page.