Ultra-compact Laser Ceilometer for Boundary Layer and Cloud Height Retrievals; 20c

The advent of sensor networks to gather atmospheric data for weather and climate predictions on large spatial and temporal scales is crucial to the advancement of our understanding of many important processes that make up 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 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. The overall objective of the Phase I and II/IIA projects is to demonstrate a compact ceilometer for operation at remote unattended sites. The proposed ceilometer incorporates a fiber laser and uses state-of-the-art techniques for ruggedization and stability in environmental extremes. The objective will be reached through modeling, engineering design, laboratory experiments, and field testing of prototypes. In the Phase I program, an initial design was developed for a compact ceilometer that will be deployable year-round at unattended network sites. A brassboard prototype successfully retrieved cloud ceilings, thus demonstrating the feasibility of the design. AmeriFlux network endusers reviewed the design. In the Phase II program, a full engineering design was completed. Two engineering prototypes were fabricated. One is currently deployed locally and is being intercompared successfully with a commercial ceilometer. It will also undergo accelerated environmental testing. A second prototype will be deployed at an AmeriFlux network site. The Phase IIA program will fully mature this technology and create an advanced pre-production prototype. The retrieval algorithms will be matured through continued intercomparison with commercial ceilometers and analysis of data recorded for a wide variety of sky conditions. An engineering prototype will undergo compliance testing for safety certifications. A low-cost variant of the existing design will be fabricated and tested to demonstrate feasibility for deployment at nontowered airports. The compact ceilometer will enable measurements of boundary layer heights and cloud ceilings 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 evolve models used in both weather forecasting and climate change prediction. The sensor is adaptable to deployment at untowered airports to provide improved weather data to general aviation pilots.