OceanRAIN Release 2.0: the second release of the in-situ shipboard global ocean surface-reference dataset of all water cycle components

OceanRAIN Release 2.0 (Ocean Rainfall And Ice-phase precipitation measurement Network) provides in-situ along-track shipboard data of precipitation, evaporation and the resulting freshwater flux at 1-min resolution over the global oceans from 10 June 2010 to 31 December 2018. More than 11.6 million minutes with 82 parameters from 8 ships cover all routinely measured atmospheric and oceanographic state variables along with those required to derive the turbulent heat fluxes. The precipitation parameter is based on measurements of the optical disdrometer ODM470 specifically designed for all-weather shipboard operations. The rain, snow and mixed-phase precipitation occurrence, intensity and accumulation are derived from particle size distributions. Additionally, microphysical parameters and radar-related parameters are provided. Addressing the need for high-quality in-situ precipitation data over the global oceans, OceanRAIN-2.0 and -1.0 are the first comprehensive along-track in-situ water cycle surface reference datasets for satellite product validation and retrieval calibration of the GPM (Global Precipitation Measurement) era, to improve the representation of precipitation and air-sea interactions in re-analyses and models, and to improve understanding of water cycle processes over the global oceans. The OceanRAIN-2.0 dataset extends the precursor version OceanRAIN Release 1.0 (Klepp et al., 2018) by increasing the data volume by a factor of 1.7. Seven new radar-related parameters are added to the OceanRAIN-2.0 database including a complete reprocessing of the OceanRAIN-1.0 data. The S-Band radar data and the inclusion of the one-way attenuation for all four radar bands was highly demanded by the international science community working with the OceanRAIN data and thus triggered the reprocessing. The OceanRAIN-2.0 dataset comprises more than 9,100,000 valid minutes of observations of which 88% are true-zero minutes that are minutes with measured precipitation absence. 12% of the total minutes with precipitation split into 63% with rain, 31% with snow and 6% with mixed-phase precipitation.

OceanRAIN Release 2.0（海洋降水与冰相降水测量网络，Ocean Rainfall And Ice-phase precipitation measurement Network）提供了2010年6月10日至2018年12月31日期间全球海洋范围内1分钟分辨率的船载原位（in-situ）沿轨（along-track）观测数据，内容涵盖降水、蒸发及由此产生的淡水通量。该数据集包含8艘科考船采集的超1160万分钟观测数据，共82项参数，覆盖所有常规测量的大气与海洋状态变量，以及推导湍流通量（turbulent heat fluxes）所需的全部相关参数。其降水参数基于专为全天候船载作业设计的光学雨滴谱仪（optical disdrometer）ODM470的实测数据。雨、雪及混合相降水的发生情况、强度与累积量均由粒子粒径分布（particle size distributions）推导得到。此外，数据集还提供微物理参数与雷达相关参数。针对全球海洋领域高质量原位降水数据的迫切需求，OceanRAIN-2.0与初代版本OceanRAIN-1.0均为全球降水测量（Global Precipitation Measurement, GPM）时代首个全面的沿轨原位水循环地表参考数据集，可用于卫星产品验证与反演校准，助力提升再分析资料与数值模式中降水及海气相互作用的表征精度，加深对全球海洋水循环过程的科学认知。OceanRAIN-2.0相较于前身版本OceanRAIN Release 1.0（Klepp等，2018），数据量提升了1.7倍。该数据集新增了7项雷达相关参数，并对OceanRAIN-1.0的全部数据进行了系统性重新处理。长期以来，使用OceanRAIN数据集的国际科研团队一直亟需S波段雷达数据以及所有四个雷达波段的单程衰减（one-way attenuation）校正参数，这一需求直接推动了本次数据重处理工作。OceanRAIN-2.0数据集包含超910万分钟有效观测数据，其中88%为真零时刻（true-zero minutes）——即未观测到降水的时刻。含降水的观测时刻占总时长的12%，其中63%为降雨时段、31%为降雪时段，剩余6%为混合相降水时段。