Walker Branch Watershed Daily Climate: 1993-2008

As part of the long-term Walker Branch project, daily climate data was collected from instruments associated with a meteorological tower located in an upper slope location within the watershed. These measurements were begun in 1993 as part of the Throughfall Displacement Experiment (TDE) in the control (ambient) plot. Measurements include daily integrated or averaged values for incident photosynthetically active radiation, incident total radiation, air temperature, relative humidity, rainfall, and soil temperature at 10-15 cm. Measurements of incoming rainfall, irradiance (Pyranometer sensor, LiCor Inc.) and photosynthetic photon flux density (Quantum sensor, LiCor Inc.) were obtained in a nearby clearing until 1998 when above canopy observations were added to the ambient plot tower. Clearing data were used to represent above-canopy conditions for the experimental site for the years 1993-1997. Sub-canopy air temperature is measured at approximately 1 m of height in a location shielded from direct solar radiation. Soil temperatures are measured at 15 cm depth and 4 locations per plot. All temperatures are measured with thermistors. Climate data are collected as hourly means and logged on data loggers (Li-1000, LiCor Inc.). Variables included and their units are: Column 1=Year Column 2 = Day of year Day of the year (1-365 or 366) Column 3 = Quan Integrated incident photosynthetically active radiation in mol m-2 Column 4 = Pyran Integrated incident total radiation in MW m-2 Column 5 = Radmean Mean daily radiation in W m-2. Column 6 = Rain Rain in mm. Hourly values summed over each day. Column 7 = AirTmin Daily 1 hour minimum air temperature in degrees C Column 8 = AirTmean Daily mean 1 hour air temperature in degrees C Column 9 = AirTmax Daily 1 hour maximum air temperature in degrees C Column 10 = RHmin Daily 1 hour minimum relative humidity in percent Column 11 = RHmean Daily mean 1 hour value Column 12 = RHmax Daily 1 hour maximum relative humidity in percent Column 13 = SoilTmin Daily 1 hour minimum soil temperature (15 cm) in degrees C Column 14 = SoilTmean Daily mean 1 hour soil temperature (15 cm) in degrees C Column 15 = SoilTmax Daily 1 hour maximum soil temperature (15 cm) in degrees C Column 16 = Wind (data not available for years prior to 1997) Wind in m s-1. Hourly values averaged over the day. Column 17 = LitterTmean (available for some years) Daily 1 hour mean litter layer (Oi) temperature in degrees C Publications: Hanson, P. J., D. E. Todd, M. A. Huston. 2003. Walker Branch Throughfall Displacement Experiment (TDE), In: Hanson, P. J. and S. D. Wullschleger, eds., North American Temperate Deciduous Forest Responses to Changing Precipitation Regimes. Springer, New York, pp. 8-31. Hanson, P.J. , D.E.Todd and J.S. Amthor. 2001. A six year study of sapling and large-tree growth and mortality responses to natural and induced variability in precipitation and throughfall. Tree Physiology 21: 345-358.作为沃克分支长期项目的组成部分，研究人员从位于流域内上坡位置的气象塔关联仪器中采集每日气候数据。该观测工作始于1993年，作为穿透雨位移实验（Throughfall Displacement Experiment, TDE）中对照（自然状态）样地的一部分。 本次测量涵盖入射光合有效辐射、入射总辐射、空气温度、相对湿度、降雨量以及10~15cm深度土壤温度的日积分值或日平均值。其中，降雨、辐照度（采用LiCor公司总辐射传感器（Pyranometer））与光合光子通量密度（采用LiCor公司量子传感器（Quantum））的观测均在附近空旷区域开展，直至1998年，此时对照样地的气象塔新增了冠层上方观测项目。1993年至1997年，空旷区域的观测数据被用于代表试验样地的冠层上方环境条件。冠层下方的空气温度在约1米高度、避开直接太阳辐射的位置进行测量；土壤温度在15cm深度处布设测点，每个样地设置4个测点。所有温度参数均采用热敏电阻采集。气候数据以小时均值的形式存储，并通过LiCor公司Li-1000型数据记录仪进行记录。 包含的变量及其单位如下： 1. 第1列：Year（年份） 2. 第2列：Day of year（年积日，取值范围为1~365或1~366） 3. 第3列：Quan：入射光合有效辐射的日积分值，单位为mol·m⁻² 4. 第4列：Pyran：入射总辐射的日积分值，单位为MW·m⁻² 5. 第5列：Radmean：日平均辐射，单位为W·m⁻² 6. 第6列：Rain：降雨量，单位为mm，为当日逐小时降雨量的累加值 7. 第7列：AirTmin：日最低1小时平均气温，单位为℃ 8. 第8列：AirTmean：日平均1小时气温，单位为℃ 9. 第9列：AirTmax：日最高1小时平均气温，单位为℃ 10. 第10列：RHmin：日最低1小时平均相对湿度，单位为% 11. 第11列：RHmean：日平均1小时相对湿度，单位为% 12. 第12列：RHmax：日最高1小时平均相对湿度，单位为% 13. 第13列：SoilTmin：日最低1小时平均土壤温度（15cm深度），单位为℃ 14. 第14列：SoilTmean：日平均1小时土壤温度（15cm深度），单位为℃ 15. 第15列：SoilTmax：日最高1小时平均土壤温度（15cm深度），单位为℃ 16. 第16列：Wind（1997年之前无有效数据）：日平均风速，单位为m·s⁻¹，为当日逐小时风速的平均值 17. 第17列：LitterTmean（部分年份有数据）：日平均1小时枯落物层（Oi层）温度，单位为℃ 相关文献： 1. Hanson P J, Todd D E, Huston M A. 2003. 沃克分支穿透雨位移实验（TDE）// Hanson P J, Wullschleger S D, eds. 北美温带落叶林对降水格局变化的响应. 纽约：施普林格出版社，第8-31页。 2. Hanson P J, Todd D E, Amthor J S. 2001. 降水与穿透雨自然及人为变异下幼树与大树生长和存活响应的六年研究. 树木生理学, 21: 345-358。