Microclimate at Harvard Forest HEM, LPH and EMS Towers since 2005

Microclimatic data are collected continuously within footprint areas of the flux
towers in order to (1) understand relationships between climatic and microclimatic
conditions and carbon dioxide and water vapor exchange between forest and atmosphere, (2)
to develop predictive models for the exchange rates of these gases, based on microclimate
data, (3) detect long-term trends in climate and microclimate at the sites and (4)
determine whether the response of carbon dioxide and water vapor exchange processes to
climate or microclimate is changing over time. The primary climatic and microclimatic
variables measured at these sites include: above-canopy photosynthetically active
radiation (PAR), forest understory PAR at 1 m height, total net radiation exchange
measured above the forest canopy, air temperature and relative humidity above the forest
canopy, forest understory air temperature at 20 cm and 1 m above ground level (shielded
but not ventilated thermocouple sensors, used only to estimate nighttime understory air
temperature), soil temperature at 10 cm depth, and soil moisture.

本数据集持续采集通量塔足迹区内的微气候数据，旨在实现以下四项研究目标：（1）厘清气候与微气候条件，以及森林与大气间二氧化碳、水汽交换过程之间的内在关联；（2）基于微气候数据构建上述气体交换速率的预测模型；（3）探测各观测站点气候与微气候的长期变化趋势；（4）明确二氧化碳与水汽交换过程对气候或微气候的响应是否随时间发生演变。本研究在各站点实测的核心气候与微气候变量包括：林冠层上方的光合有效辐射（photosynthetically active radiation，简称PAR）、高度1米处的林下光合有效辐射、林冠层上方测得的总净辐射交换量、林冠层上方的气温与相对湿度、距地面20厘米及1米处的林下气温（采用屏蔽未通风的热电偶传感器监测，仅用于估算夜间林下气温）、10厘米深度的土壤温度，以及土壤含水量。