Cloud droplet characterization instrument for small aerial platforms

Stratus and stratocumulus clouds with low drop concentration and large drop diameter are scientifically very important, because this is the regime in which drizzle drops are formed. The formation of drizzle can lead to a rapid modification of the cloud droplet size distribution, which in turn has a strong influence on the cloud's radiative properties. Because stratus and stratocumulus clouds cover a large portion of the Earth, this process has a strong impact on the global radiative budget. New inexpensive, fast and lightweight technologies for cloud droplet/drizzle measurement in the size range of 10–1000 micrometers suitable for deployment on small aerial platforms, such as unmanned aerial systems (UAS), balloons, blimps and kites, are needed. This SBIR project will develop an innovative, compact, lightweight and inexpensive optical imaging technology for fast in situ cloud droplet/drizzle characterization, including measurement of droplet size distribution functions and droplet number concentration. The target droplet size range is 10–1000 micrometers. The instrument will be specifically designed to meet the stringent requirement for deployment on small aerial platforms. An innovative optical layout will enhance the sensitivity and improve the accuracy of the measurements. In addition, the proposed technology is expected to provide self-calibration capabilities, which will be indispensable during field airborne measurement campaigns. The Phase I study will focus on: (1) implementation and optimization of the novel optical illumination/imaging configuration in order to maximize the performance and minimize the instrument footprint and power draw, (2) exploration of self-calibrating capabilities of the system, (3) outlining and initial development of fast and efficient image frame processing algorithms, and (4) identifying the engineering challenges of adapting the technology to small aerial platforms and designing a flight-ready prototype system in Phase II. The successful completion of this Phase I/II program will lead to development of a cloud droplet measurement instrument primarily designed for use on small unmanned aerial platforms. When carried over into Phase III and beyond, this project will be of great benefit to the public and the Federal Government. Precise and extensive cloud characterization data will lead to better understanding of the contribution of atmospheric clouds to Earth’s radiative budget and climate change. Flexibility and low cost of the proposed technology will make it compatible with a variety of airborne- and ground-based platforms and suitable for other applications such as characterization of atmospheric aerosols, volcanic ash plumes and industrial/agricultural sprays. Cloud droplet number density and size distribution function strongly affect the cloud's radiative properties. This project will develop a novel technology of cloud droplet characterization, primarily designed for small unmanned aerial platforms, which will help understanding the role of clouds in Earth’s radiative budget and hence the climate change.