Sampling the atmospheric boundary layer with small unmanned aircraft is a difficult task requiring informed selection of sensors and algorithms that are suited to the particular platform and mission. Many factors must be considered during the design process to ensure the desired measurement accuracy and resolution is achieved, as is demonstrated through an examination of previous and current efforts. A taxonomy is developed from these approaches and is used to guide a review of the systems that have been employed to make in situ wind and thermodynamic measurements, along with the campaigns that have employed them. Details about the airframe parameters, estimation algorithms, sensors, and calibration methods are given.

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The Bering Glacier–Bagley Icefield system in Alaska is currently surging (2011). Large-scale elevation changes and small-scale elevation-change characteristics are investigated to understand surge progression, especially mass transport from the pre-surge reservoir area to the receiving area and propagation of the kinematic surge wave as manifested in heavy crevassing characteristic of rapid, brittle deformation. This analysis is based on airborne laser altimeter data collected over Bering Glacier in September 2011. Results include the following: (1) Maximal crevasse depth is 60 m, reached in a rift that separates two deformation domains, indicative of two different flow regimes. Otherwise surge crevasse depth reaches 20–30 m. (2) Characteristic parameters of structural provinces are derived by application of geostatistical classification. Parameters include significance and spacing of crevasses, surface roughness and crevasse-edge curvature (indicative of crevasse age). A classification based on these parameters serves to objectively discriminate structural provinces, indicative of surge progression down-glacier and up-glacier. (3) Elevation changes from 2011 and 2010 altimetry show 40–70 m surface lowering in the reservoir area in lower central Bering Glacier and 20–40m thickening near the front in Tashalich arm. Combining elevation changes with results of crevasse profilometry and pattern analysis, the rapid progression of the surge can be mathematically–physically reconstructed.

This paper reports results from field deployments of the Tempest Unmanned Aircraft System, the first of its kind of unmanned aircraft system designed to perform in situ sampling of supercell thunderstorms, including those that produce tornadoes. A description of the critical system components, consisting of the unmanned aircraft, ground support vehicles, communications network, and custom software, is given. The unique concept of operations and regulatory issues for this type of highly nomadic and dynamic system are summarized, including airspace regulatory decisions from the Federal Aviation Administration to accommodate unmanned aircraft system operations for the study of supercell thunderstorms. A review of the system performance and concept of operations effectiveness during flights conducted for the spring 2010 campaign of the VORTEX2 project is provided. These flights resulted in the first-ever sampling of the rear flank gust front and airmass associated with the rear flank downdraft of a supercell thunderstorm by an unmanned aircraft system. A summary of the lessons learned, future work, and next steps is provided. C 2011 Wiley Periodicals, Inc.

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