2012 Annual Report
1a.Objectives (from AD-416):
Develop an inexpensive method for real-time, remotely-accessible measurement of vineyard-scale evapotranspiration and vine water use.
1b.Approach (from AD-416):
A field based surface renewal system will be used to estimate vine and whole vineyard water use. The work will involve developing a self-calibrated, inexpensive, user-friendly surface renewal system for use in vineyards.
This agreement was established in support of objective 3 of the in-house project, which is to develop sustainable water management practices for vineyards. The goal of this project is to develop an inexpensive method for real-time, remotely-accessible measurements of vineyard-scale evapotranspiration and vine water use. Micrometeorological methods and ecosystem-scale energy and gas flux measurements have become increasingly important in soil, crop, and environmental sciences. For many scientists without formal training in atmospheric science, these techniques are relatively inaccessible. Eddy covariance, surface renewal, and other flux measurement methods require an understanding of boundary layer meteorology and extensive training in instrumentation and multiple data management programs.
Significant progress has also been made on revisiting the theoretical calculations (i.e. Van Atta equations) that drive Surface Renewal estimates of water flux from agricultural surfaces. Until now, surface renewal relied on Eddy Co-Variance for calibration and our updated theoretical calculations have all but eliminated the need for this calibration. We recently published two invited manuscripts in a special issue of Boundary Layer Meteorology (Shapland et al. 2012a &2012b). Two additional manuscripts are nearing completion and will be submitted to the journals by October 2012.
Over the past few months, we made excellent progress in calibrating SR for the use of more sturdy (thicker gauge) thermocouples under field conditions. The fine gauge thermocouples, originally used in for SR, are highly responsive and work well for tracking the air temperature fluctuations at high frequency, however, they are fragile and required much maintenance. We successfully calibrated fine gauge thermocouples against heavier gauge (more sturdy) ones. The surface renewal sensible heat flux estimates from the heavier thermocouples (76 micron diameter wire) are strongly correlated with those of the 13 micron diameter (fine gauge) thermocouples. We established SR fields stations at two weighing lysimeter sites (Wheat in Davis and Thompson Seedless grapevines in Parlier) to compare results against the water loss estimates from the weighing lysimeters.