Ultracompact laser ceilometer for boundary layer and cloud height retrievals

The advent of sensor networks to gather atmospheric data for weather and climate prediction on large spatial and temporal scales is crucial to the advancement of our understanding of many important processes that make up such predictive models. The height of the atmospheric boundary layer, for example, is used to parameterize boundary layer transport in numerical weather prediction models and boundary layer effects related to fluxes and concentrations of trace gases in inversion models. Increased knowledge of boundary layer structure drives the desire to add the capability to monitor this height to networks. General statement of how this problem is being addressed. The overall objective of the Phase I and II projects is to demonstrate a highly compact, automated, low power ceilometer to make retrievals of cloud base and boundary layer heights from remote unattended sites. The proposed ceilometer incorporates a fiber laser and uses state-of-the-art techniques for environmental stability. The objective will be reached through signal modeling, engineering design, basic laboratory experiments, and field testing of prototypes.What was done in Phase I? In the Phase I program, a design was developed for a compact, automated laser ceilometer that can retrieve both cloud base heights and the height of the atmospheric boundary layer and that will be deployable year round at AmeriFlux network tower sites. A brassboard prototype of the desired size and weight successfully retrieved cloud ceilings with the desired spatial and temporal resolution, thus demonstrating the feasibility of the design. AmeriFlux network site endusers reviewed the ceilometer design, suggested improvements to be incorporated in the Phase II prototype, and performed a mock installation of the brassboard. What is planned for the Phase II project? Several engineering prototypes of the compact ceilometer will be fabricated and then intercompared for performance with a commercial ceilometer. Several prototypes will be deployed at two different AmeriFlux network sites for extended testing, continued intercomparison with commercial ceilometers, and site integration optimization. Commercial Applications and Other Benefits. The proposed compact laser ceilometer will enable measurements of boundary layer and cloud base heights on a wider scale and at higher frequencies than are possible now when deployed at long term measurement sites. Such measurements are fundamental to improving our understanding of the complex couplings between the surface and lower atmosphere and will ultimately help to evolve models used in both weather forecasting and climate change prediction. The sensor is adaptable to deployment in other weather networks, such as the Automated Surface Observing System and other national and state mesonets, where sensor robustness and size are critical to performance.