Real-time monitoring of evapotranspiration dynamics through snapshot hyperspectral imaging at near-infrared

Monitoring atmospheric water vapor dynamics is important for many atmospheric and hydrologic applications, ranging from weather forecasting and agricultural practices to climate impacts and flood preparedness. To improve the spatiotemporal resolution of conventional methods for monitoring water vapor dynamics, we have developed a snapshot spectral imager operating in the near-infrared range, spanning 1100 nm to 1300 nm. This imager utilizes a custom-designed fiber bundle remapping and prism dispersion technique. By covering the vapor-sensitive band at 1140 nm and the water vapor-insensitive shoulder at 1260 nm, our system holds promise for tracking water vapor dynamics across many heterogeneous environments that challenge traditional measurement techniques. Through meticulous optomechanical design, the current ruggedized configuration remains portable while maintaining an adaptive spatial sampling of approximately 35,000 locations and over 20 adaptive spectral sampling channels. Laboratory tests have validated its sensitivity, capable of detecting changes as small as 70 micrometers of precipitable water vapor. Field experiments conducted across various vegetation types have showcased the imager's efficacy and demonstrated the imager's ability to monitor temporal and spatial fluctuations in water vapor across different landscapes. Real-time mapping of water index variations holds promise for diverse applications, including atmospheric, environmental, agricultural, and solar energy research. The real-time measurements enabled by the instrument described here provide new capabilities to monitor water vapor.