GHRSST Level 2P Global 1m Sea Surface Temperature from the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA-18 satellite produced by NAVO for 2017-05-21 (NCEI Accession 0164104)

A global Group for High Resolution Sea Surface Temperature (GHRSST) Level 2P dataset based on multi-channel sea surface temperature (SST) retrievals generated in real-time from the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA-18 platform (launched 20 May 2005) produced and used operationally in oceanographic analyses and forecasts by the US Naval Oceanographic Office (NAVO). The AVHRR is a space-borne scanning sensor on the National Oceanic and Atmospheric Administration (NOAA) family of Polar Orbiting Environmental Satellites (POES) having a operational legacy that traces back to the Television Infrared Observation Satellite-N (TIROS-N) launched in 1978. AVHRR instruments measure the radiance of the Earth in 5 (or 6) relatively wide spectral bands. The first two are centered around the red (0.6 micrometer) and near-infrared (0.9 micrometer) regions, the third one is located around 3.5 micrometer, and the last two sample the emitted thermal radiation, around 11 and 12 micrometers, respectively. The legacy 5 band instrument is known as AVHRR/2 while the more recent version, the AVHRR/3 (first carried on the NOAA-15 platform), acquires data in a 6th channel located at 1.6 micrometer. Typically the 11 and 12 micron channels are used to derive SST sometimes in combination with the 3.5 micron channel. The NOAA platforms are sun synchronous generally viewing the same earth location twice a day (latitude dependent) due to the relatively large AVHRR swath of approximately 2400 km. The highest ground resolution that can be obtained from the current AVHRR instruments is 1.1 km at nadir. AVHRR data are acquired in three formats: High Resolution Picture Transmission (HRPT), Local Area Coverage (LAC), and Global Area Coverage (GAC). HRPT data are full resolution image data transmitted to a ground stations as they are collected. LAC are also full resolution data, but the acquisition is prescheduled and recorded with an on-board tape recorder for subsequent transmission during a station overpass. This particular dataset is produced from GAC data that are derived from an on-board sample averaging of the full resolution global AVHRR data. Four out of every five samples along the scan line are used to compute on average value and the data from only every third scan line are processed, yielding an effective 4 km resolution at nadir. Further binning and averaging of these pixels results in a final dataset resolution of 8.8 km.全球高精度海表温度（Group for High Resolution Sea Surface Temperature, GHRSST）2P级数据集，基于多通道海表温度（Sea Surface Temperature, SST）反演结果生成，由搭载于2005年5月20日发射的NOAA-18平台的先进甚高分辨率辐射计（Advanced Very High Resolution Radiometer, AVHRR）实时反演得到，并由美国海军海洋学办公室（US Naval Oceanographic Office, NAVO）投入业务化应用，用于海洋学分析与预报。AVHRR是美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration, NOAA）极轨环境卫星（Polar Orbiting Environmental Satellites, POES）系列搭载的星载扫描传感器，其业务化应用历史可追溯至1978年发射的电视红外观测卫星-N（Television Infrared Observation Satellite-N, TIROS-N）。AVHRR仪器可测量地球在5（或6）个相对较宽的光谱波段内的辐射亮度，前两个波段的中心波长分别位于红光（0.6微米）与近红外（0.9微米）区域，第三个波段中心约为3.5微米，最后两个波段分别采样11微米与12微米波段的地球发射热辐射。传统的5波段仪器被称为AVHRR/2，而最新版本AVHRR/3（首次搭载于NOAA-15平台）新增了1.6微米的第6通道以获取观测数据。通常可利用11微米与12微米波段反演海表温度，有时也会结合3.5微米波段一同进行反演。NOAA卫星平台均为太阳同步轨道，由于AVHRR的刈幅宽度约为2400千米，因此通常可每日（依纬度不同）对同一地球位置进行两次观测。当前AVHRR仪器在星下点处可获得的最高地面分辨率为1.1千米。AVHRR数据存在三种采集格式：高分辨率图像传输（High Resolution Picture Transmission, HRPT）、局地区域覆盖（Local Area Coverage, LAC）以及全球区域覆盖（Global Area Coverage, GAC）。HRPT数据为全分辨率图像数据，在采集完成后直接传输至地面站。LAC同样为全分辨率数据，但采集需预先规划，并通过星载磁带记录仪进行录制，待飞越地面站时再行传输。本数据集由GAC数据生成，而GAC数据是对全分辨率全球AVHRR数据进行星上采样平均后得到的产物：扫描线上每5个采样点中选取4个计算平均值，且仅处理每第三条扫描线的数据，最终在星下点处的有效分辨率为4千米。对上述像素进一步进行分箱与平均处理后，最终得到的数据集分辨率为8.8千米。