fPar derived from MODIS for the Sydney Basin

## **Abstract** \n\nThe dataset was derived by the Bioregional Assessment Programme. This dataset was derived from the fPar derived from MODIS for BA subregions dataset. You can find a link to the parent dataset in the Lineage Field in this metadata statement. The History Field in this metadata statement describes how this dataset was derived.\n\n\n\nFraction of photosynthetically active radiation derived from MODIS for the Sydney Basin. Used to generate a landcover maps for selected regions.\n\n\n\nFile geodatabase contains the following rasters\n\nlta_persistent_SYD: long term annual average persistent veg cover\n\nlta_ recurrent_SYD: long term annual average recurrent veg cover.\n\nlta_total_SYD: long term annual average total cover (ie the sum of persistent + recurrent)\n\n\n\n12 grids\n\nltm_recurrent_xx_SYD: long term monthly average recurrent veg cover. xx = 01, 02..12 ie month.\n\n\n\nDonohue, R.J., McVicar, T.R. and Roderick, M.L. (2009) Climate-related changes in Australian vegetation cover as inferred from satellite observations for 1981-2006. Global Change Biology. 15(4), 1025-1039. doi:10.1111/j.1365-2486.2008.01746.x\n\n\n\nDonohue, R.J., Roderick, M.L. and McVicar, T.R. (2008) Deriving consistent long-term vegetation information from AVHRR reflectance data using a cover-triangle-based framework. Remote Sensing of Environment. 112(6), 2938-2949. doi:10.1016/j.rse.2008.02.008\n\n## **Dataset History** \n\nUsing time series (Normalised Differential Vegetation Index (NDVI) imagery (ranges from -1 to +1, only negative for water bodies, with non-water surfaces ranging from near 0 for bare soil / no vegetation to near 1 for high vegetation amounts) from the MODIS sensor, specifically the MOD13Q1.005 product, which has a spatial resolution of 250m and is a composite of 16-days. The NDVI was scaled NDVI to total fPAR (fraction of Photosynthetic Active Radiation \\[i.e., 400nm to 700nm\\] absorbed by plants, which ranges from 0 to 1) using the approach of Donohue et al (2008). At each grid-cell the time series of total fPAR estimates are then temporally decomposed using the algorithm of Donohue et al (2009). This partitions the per-pixel and per time-step total fPAR estimate into the recurrent and persistent fPAR components. In general the recurrent component is related to crops / grasses with a strong annual cycle of greenness, and the persistent component is related to evergreen trees and shrubs. There are however vegetation types which do not accord to this "one-to-one" classification, for example evergreen / improved pastures (these are typically regarded as being persistent) and deciduous trees (these are typically regarded as being recurrent). The fPAR values (total, recurrent and persistent) where then converted to percentage green vegetation cover (ranging from 0% to 100%), this was performed assuming a 0.01 fPAR change represented a 1% change in vegetation cover. The digital numbers (DNs) of the fPAR data range between 0 to 1000, and so green percentage cover was calculated as fPAR value / 10. As examples, an fPAR DN of 500 = 50% and 350 = 35% etc.\n\n## **Dataset Citation** \n\nBioregional Assessment Programme (2014) fPar derived from MODIS for the Sydney Basin. Bioregional Assessment Derived Dataset. Viewed 07 February 2017, http://data.bioregionalassessments.gov.au/dataset/5d80eb34-895c-4fba-a582-7a6380d55d40.\n\n## **Dataset Ancestors** \n\n* **Derived From** [fPar derived from MODIS for BA subregions](https://data.gov.au/data/dataset/299ec634-2919-4838-a163-a6804b95438c)\n\n

**摘要**

本数据集由生物区域评估计划（Bioregional Assessment Programme）衍生而来，其源头为针对BA子区域的MODIS衍生光合有效辐射分数（fPar）数据集。您可在本元数据声明的谱系字段（Lineage Field）中找到父数据集的链接，而元数据声明的历史字段（History Field）则详述了本数据集的衍生流程。

本数据集为针对悉尼盆地的MODIS衍生光合有效辐射分数（fPar）数据，可用于生成选定区域的土地覆盖图。

本文件地理数据库（File Geodatabase）包含以下栅格数据：

lta_persistent_SYD：长期年平均持续性植被覆盖度

lta_recurrent_SYD：长期年平均周期性植被覆盖度

lta_total_SYD：长期年平均总覆盖度（即持续性与周期性覆盖度之和）

共12个月度栅格：

ltm_recurrent_xx_SYD：长期月平均周期性植被覆盖度，其中xx代表月份（01、02……12）。

Donohue, R.J.、McVicar, T.R. 与 Roderick, M.L.（2009）：《基于1981-2006年卫星观测数据推断的澳大利亚植被覆盖气候相关变化》，《全球变化生物学》（Global Change Biology），15(4)，1025-1039。DOI: 10.1111/j.1365-2486.2008.01746.x

Donohue, R.J.、Roderick, M.L. 与 McVicar, T.R.（2008）：《基于覆盖三角框架从AVHRR反射率数据中提取一致的长期植被信息》，《环境遥感》（Remote Sensing of Environment），112(6)，2938-2949。DOI: 10.1016/j.rse.2008.02.008

**数据集历史**

本数据集基于MODIS传感器的时序归一化差分植被指数（Normalized Differential Vegetation Index，简称NDVI）影像构建：NDVI取值范围为-1至+1，仅水体区域为负值，非水体区域取值接近0代表裸土/无植被，接近1代表植被覆盖度极高。本数据集采用MOD13Q1.005产品，其空间分辨率为250米，为16天合成影像。

依据Donohue等人（2008）提出的方法，将NDVI转换为总光合有效辐射分数（fraction of Photosynthetic Active Radiation，简称fPAR，即植物吸收的400nm至700nm波段辐射的占比，取值范围为0至1）。随后依据Donohue等人（2009）的算法，对每个栅格单元的总fPAR时序估计值进行时间分解，将每个像元每个时次的总fPAR估计值划分为周期性与持续性fPAR分量。通常而言，周期性分量与具有显著年度青绿周期的作物/草本植被相关，而持续性分量则与常绿乔木和灌木相关。但存在部分植被类型无法归为此类“一一对应”分类，例如常绿/改良牧场（通常被归为持续性覆盖）与落叶乔木（通常被归为周期性覆盖）。

随后将总、周期性及持续性fPAR值转换为绿色植被覆盖百分比（取值范围为0%至100%），转换假设为0.01的fPAR变化对应1%的植被覆盖变化。fPAR数据的数字值（DN）取值范围为0至1000，因此绿色植被覆盖百分比可通过fPAR数值除以10计算得到。例如，fPAR DN值为500对应50%覆盖度，350对应35%覆盖度，以此类推。

**数据集引用**

生物区域评估计划（2014）：《针对悉尼盆地的MODIS衍生光合有效辐射分数（fPar）》，生物区域评估衍生数据集。2017年2月7日查阅，链接：http://data.bioregionalassessments.gov.au/dataset/5d80eb34-895c-4fba-a582-7a6380d55d40.

**数据集祖先**

* **衍生自** [针对BA子区域的MODIS衍生光合有效辐射分数（fPar）](https://data.gov.au/data/dataset/299ec634-2919-4838-a163-a6804b95438c)