Land cover and climate informed vapor pressure deficit datasets derived from Daymet

Vapor pressure deficit (VPD) is a critical variable in assessing drought conditions and evaluating plant water stress. Gridded products of global and regional VPD are not freely available from satellite remote sensing, model reanalysis, or ground observation datasets. We present two versions of the first gridded VPD product for the Continental US and parts of Northern Mexico and Southern Canada (CONUS+) at a 1 km spatial resolution and daily time step. We derived VPD from Daymet maximum daily temperature and average daily vapor pressure and scale the estimates based on (1) climate determined by the Köppen-Geiger classifications and (2) land cover determined by the International Geosphere-Biosphere Programme. Ground-based VPD data from 253 AmeriFlux sites representing different climate and land cover classifications were used to improve the Daymet-derived VPD estimates for every pixel in the CONUS+ grid to produce the final datasets. We evaluated the Daymet-derived VPD against independent observations and reanalysis data. The CONUS+ VPD datasets will aid in investigating disturbances including drought and wildfire, and informing land management strategies.

水汽压亏缺（Vapor pressure deficit, VPD）是评估干旱状况与植物水分胁迫的关键变量。当前，全球及区域尺度的VPD格点产品无法通过卫星遥感、模型再分析或地面观测数据集免费获取。本研究首次发布针对美国本土、墨西哥北部部分区域及加拿大南部部分区域（CONUS+）的两款VPD格点产品，空间分辨率为1千米，时间步长为每日。本研究基于Daymet逐日最高气温与日均水汽压计算VPD，并依据（1）柯本-盖格（Köppen-Geiger）气候分类法划定的气候类型、（2）国际地圈生物圈计划（International Geosphere-Biosphere Programme）确定的土地覆被类型，对估算结果进行尺度校正。本研究利用覆盖不同气候与土地覆被类型的253个美洲通量网（AmeriFlux）站点的地面VPD观测数据，对CONUS+格网中每个像元基于Daymet得到的VPD估算结果进行优化，以此生成最终数据集。本研究通过独立观测数据与再分析数据，对基于Daymet得到的VPD估算结果开展了验证评估。CONUS+ VPD数据集将有助于开展干旱、野火等陆地扰动相关研究，并为土地管理策略制定提供科学支撑。