NOAA 0.25-degree Daily Optimum Interpolation Sea Surface Temperature (OISST), Version 2.1, 1981 - Present

This high-resolution sea surface temperature (SST) analysis product was developed using an optimum interpolation (OI) technique. The OISST analysis has a spatial grid resolution of 0.25 degree and temporal resolution of 1 day, spanning from September 1981 to present. The analysis was constructed by combining observations from different platforms on a regular global grid, including Advanced Very High Resolution Radiometer (AVHRR) satellite data, ships, buoys and Argo floats. A spatially complete SST map was produced by interpolating to fill in spatial gaps. The methodology includes bias adjustment of satellite and ship observations (referenced to buoys) to compensate for platform differences and sensor biases. This proved critical during the Mt. Pinatubo eruption in 1991, when the widespread presence of volcanic aerosols resulted in infrared satellite temperatures that were much cooler than actual ocean temperatures, and other degradation of satellite observations. Released in March 2020, Version 2.1 supersedes the previous Version 2. For the January 2016 to present time period, changes include: 1) In-Situ ship and buoy data changed from the NCEP Traditional Alphanumeric Codes (TAC) to the NCEI merged TAC + Binary Universal Form for the Representation (BUFR) data; 2) Addition of Argo float observed SST data; 3) Satellite input changed from METOP-A and NOAA-19 to METOP-A and METOP-B; 4) Revised ship-buoy SST corrections and revised sea-ice-concentration to SST conversion. The data before January 1, 2016 remain the same as Version 2.0. Preliminary product files are produced daily in near real-time (1-day latency) and can be updated in the first few days if critical input data become available after the initial production time. After two weeks, a complete or final product is generated and archived with no additional changes expected. The product is available in netCDF-4 with metadata attributes.本高分辨率海表温度（Sea Surface Temperature, SST）分析产品采用最优插值（Optimum Interpolation, OI）技术开发而成。本次OISST分析的空间网格分辨率为0.25°，时间分辨率为1日，时间跨度为1981年9月至今。该分析基于全球规则网格，融合了多平台观测数据，包括先进甚高分辨率辐射计（Advanced Very High Resolution Radiometer, AVHRR）卫星数据、船舶观测、浮标数据以及Argo浮标数据。通过插值填补空间空白，生成空间完整的海表温度图。该方法包含以浮标数据为基准的卫星与船舶观测偏差校正流程，用以抵消平台差异与传感器偏差带来的影响。这一点在1991年皮纳图博火山喷发期间显得尤为关键：当时大范围火山气溶胶的存在导致红外卫星观测的温度远低于实际海温，同时卫星观测出现了其他性能退化问题。该产品2.1版于2020年3月发布，取代了此前的2.0版。针对2016年1月至今的时段，本次更新内容如下：1）将原位船舶与浮标数据来源从美国国家环境预报中心（NCEP）传统字母数字编码（TAC）数据，更换为美国国家环境信息中心（NCEI）融合的TAC+二进制通用表示格式（BUFR）数据；2）新增Argo浮标观测的海表温度数据；3）卫星输入数据源从METOP-A与NOAA-19变更为METOP-A与METOP-B；4）修正了船舶-浮标海表温度校正方法，以及海冰浓度转海表温度的转换流程。2016年1月1日之前的数据集内容与2.0版保持一致。产品初步文件以准实时方式每日生成（延迟1日），若初始生产后获取到关键输入数据，可在生成后的前几日进行更新。生成两周后，将生成并归档最终完整产品，此后不再进行额外修改。该产品以netCDF-4格式提供，附带元数据属性。