SBC LTER: Time series of quarterly NetCDF files of kelp biomass in the canopy from Landsat 5, 7 and 8, since 1984 (ongoing)

This data file represents a time series of canopy area of giant
kelp, Macrocystis pyrifera, and bull kelp,
Nereocystis luetkeana, and canopy biomass of
giant kelp derived from Landsat 5 Thematic Mapper (TM), Landsat 7
Enhanced Thematic Mapper Plus (ETM+), Landsat 8 Operational Land
Imager (OLI), and Landsat 9 Operational Land Imager 2 satellite
imagery, along with relevant metadata. The kelp canopy is composed
of the portions of fronds and stipes floating on the surface of
the water. Canopy area (m) data are given for individual 30 x 30
meter pixels for all coastal areas of Baja California, Mexico,
California, Oregon, and the outer coast of Washington (including
offshore islands). Biomass data (wet weight, kg) are given for
individual 30 x 30 meter pixels in the coastal areas extending
from near Ano Nuevo, CA through the southern range limit in Baja
California (including offshore islands), representing the range
where giant kelp is the dominant canopy forming species.

Data were derived from the three Landsat sensors listed above.
Observations are made on a 16 day repeat cycle, for each
instrument, but the temporal coverage is irregular because of
cloud cover, instrument failure, and the mission length of each
sensor (TM: 1984 – 2011, ETM+: 1999 – present, OLI: 2013 –
present). Estimates of canopy area are derived from the fractional
cover of kelp canopy determined from satellite surface
reflectance. Estimates of kelp canopy biomass are derived from the
relationship between giant kelp fractional cover determined from
satellite surface reflectance and empirical measurements of giant
kelp canopy biomass in long-term SBC LTER study plots obtained
using SCUBA. The different Landsat sensors were calibrated to each
other using simulated Landsat data derived from hyperspectral
imagery. Missing data due to the ETM+ scan line corrector error
were filled using a synchrony-based gap filling method.

Data are organized into a single NetCDF file and contain the
quarterly area and biomass means for each Landsat pixel across the
three sensors. Relevant metadata such as number of Landsat
estimates from which the mean was derived, the number of estimates
from each sensor, standard error for each quarterly estimate,
spatial coordinates, and date are all included in the file. For
assistance with the data, please contact [e-mail].

本数据集文件包含基于陆地卫星5号主题制图仪（Thematic Mapper, TM）、陆地卫星7号增强型主题制图仪（Enhanced Thematic Mapper Plus, ETM+）、陆地卫星8号陆地成像仪（Operational Land Imager, OLI）以及陆地卫星9号陆地成像仪2号卫星影像反演得到的巨藻（Macrocystis pyrifera）与公牛海带藻（Nereocystis luetkeana）的冠层面积，以及巨藻冠层生物量时间序列数据，同时附带相关元数据。海带冠层指漂浮于水面的藻叶与藻柄部分。冠层面积（单位：平方米）数据以30米×30米的独立像素为单位，覆盖墨西哥下加利福尼亚州、加利福尼亚州、俄勒冈州以及华盛顿州外海沿岸区域（含近海岛屿）的全部沿海海域。生物量数据以湿重（单位：千克）为单位，以30米×30米独立像素为载体，覆盖从加利福尼亚州阿尼奥新诺（Ano Nuevo）附近至下加利福尼亚州南部分布边界的沿岸海域（含近海岛屿），该区域以巨藻为优势冠层形成物种。

本数据集基于上述四款陆地卫星传感器反演得到。各传感器均以16天为重复观测周期，但受云遮挡、传感器故障及各传感器任务周期影响，时间覆盖范围并不规则（TM传感器任务周期：1984年—2011年；ETM+传感器任务周期：1999年—至今；OLI传感器任务周期：2013年—至今）。冠层面积估算值基于卫星地表反照率反演得到的海带冠层覆盖占比计算得出。海带冠层生物量估算值则基于卫星地表反照率反演得到的巨藻覆盖占比，与通过水肺潜水在长期SBC LTER（圣巴巴拉海岸长期生态研究计划）样地中实测得到的巨藻冠层生物量之间的关联关系推导得出。不同陆地卫星传感器间通过高光谱影像生成的模拟陆地卫星数据完成辐射定标。针对ETM+传感器扫描线校正器故障导致的数据缺失，采用基于同步性的间隙填充方法进行补全。

本数据集整合为单个NetCDF文件，包含三款传感器对应各陆地卫星像素的季度面积与生物量均值。文件中附带完整元数据，包括用于计算均值的陆地卫星估算次数、各传感器的估算次数、各季度估算值的标准误差、空间坐标及观测日期等信息。如需获取数据相关协助，请联系邮箱[e-mail]。