Hurricane Maria Puerto Rico Landsat Analysis

Hurricane Maria made landfall as a strong Category 4 storm in southeast Puerto Rico on September 20th, 2018. The powerful storm traversed the island in a northwesterly direction causing widespread destruction. This study focused on a rapid assessment of Hurricane Marias impact to Puerto Ricos forests. Calibrated and corrected Landsat 8 image composites for the entire island were generated using Google Earth Engine for a comparable pre-Maria and post-Maria time period that accounted for phenology. Spectral mixture analysis (SMA) using image-derived end members was carried out on both composites to calculate the change in the non-photosynthetic vegetation (Delta-NPV) spectral response, a metric that quantifies the increased fraction of exposed wood and surface litter associated with tree mortality and crown damage from the storm. Hurricane simulations were also conducted using the Weather Research and Forecasting (WRF) regional climate model to estimate wind speeds associated with forest disturbance. Dramatic changes in forest structure across the entire island were evident from pre- and post-Maria composited Landsat 8 images. A Delta-NPV map for only the forested pixels illustrated significant spatial variability in disturbance, with patterns that associated with factors such as slope, aspect and elevation. An initial order-of-magnitude impact estimate based on previous work indicated that Hurricane Maria may have caused mortality and severe damage to 23-31 million trees. Additional field work and image analyses are required to further detail the impact of Hurricane Maria to Puerto Rico forests. A minor update to this dataset was posted on April 20, 2018. The previous version is being retired. If you need access to the prior version of the data, email [e-mail].

玛丽亚飓风于2018年9月20日以强四级风暴的强度在波多黎各东南部登陆。这场强风暴向西北方向横扫全岛，造成了大范围破坏。本研究旨在快速评估玛丽亚飓风对波多黎各森林的影响。研究利用谷歌地球引擎（Google Earth Engine）生成了全岛范围的校准及校正后Landsat 8影像合成产品，覆盖了考虑物候因素的玛丽亚飓风前、后可比时间段。对两组合成影像均进行了基于影像端元的光谱混合分析（SMA），以计算非光合植被（Delta-NPV）光谱响应的变化；该指标可量化风暴导致的树木死亡和树冠损伤相关的裸露木材及地表凋落物比例的增加。研究还利用天气研究与预报（WRF）区域气候模型进行了飓风模拟，以估算与森林扰动相关的风速。从玛丽亚飓风前、后合成的Landsat 8影像中可明显看出全岛森林结构的显著变化。仅针对森林像素的Delta-NPV地图显示了扰动的显著空间变异性，其模式与坡度、坡向和海拔等因素相关。基于先前研究的初步量级影响估算表明，玛丽亚飓风可能导致了2300万至3100万棵树木死亡或严重受损。需要进一步的野外工作和影像分析以更详细地阐明玛丽亚飓风对波多黎各森林的影响。本数据集的一次小幅更新于2018年4月20日发布。旧版本已停用。如需获取该数据的旧版本，请发送邮件至[e-mail]。