Global Hawk dropsonde observations of the Arctic atmosphere obtained during the Winter Storms and Pacific Atmospheric Rivers (WISPAR) field campaign

Atmos. Meas. Tech., 7, 3917–3926, 2014 www.atmos-meas-tech.net/7/3917/2014/ doi:10.5194/amt-7-3917-2014 © Author(s) 2014. CC Attribution 3.0 License. Global Hawk dropsonde observations of the Arctic atmosphere obtained during the Winter Storms and Pacific Atmospheric Rivers (WISPAR) field campaign J. M. Intrieri1 , G. de Boer1,2 , M. D. Shupe1,2 , J. R. Spackman1,3 , J. Wang4,6 , P. J. Neiman1 , G. A. Wick1 , T. F. Hock4 , and R. E. Hood5 1 NOAA, Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305, USA 2 Cooperative Institute for Research in the Environmental Sciences, University of Colorado at Boulder, Box 216 UCB, Boulder, CO 80309, USA 3 Science and Technology Corporation, Boulder, CO 80305, USA 4 National Center for Atmospheric Research, 1850 Table Mesa Dr., Boulder, CO 80305, USA 5 NOAA, Unmanned Aircraft Systems Program, 1200 East West Highway, Silver Spring, MD 20910, USA 6 University at Albany, SUNY, Department of Atmospheric & Environmental Sciences, Albany, NY 12222, USA Correspondence to: J. M. Intrieri () Received: 20 February 2014 – Published in Atmos. Meas. Tech. Discuss.: 23 April 2014 Revised: 15 September 2014 – Accepted: 20 October 2014 – Published: 25 November 2014 Abstract. In February and March of 2011, the Global Hawk unmanned aircraft system (UAS) was deployed over the Pacific Ocean and the Arctic during the Winter Storms and Pacific Atmospheric Rivers (WISPAR) field campaign. The WISPAR science missions were designed to (1) improve our understanding of Pacific weather systems and the polar atmosphere; (2) evaluate operational use of unmanned aircraft for investigating these atmospheric events; and (3) demonstrate operational and research applications of a UAS dropsonde system at high latitudes. Dropsondes deployed from the Global Hawk successfully obtained high-resolution profiles of temperature, pressure, humidity, and wind information between the stratosphere and surface. The 35 m wingspan Global Hawk, which can soar for ∼ 31 h at altitudes up to ∼ 20 km, was remotely operated from NASA’s Dryden Flight Research Center at Edwards Air Force Base (AFB) in California. During the 25 h polar flight on 9–10 March 2011, the Global Hawk released 35 sondes between the North Slope of Alaska and 85◦ N latitude, marking the first UAS Arctic dropsonde mission of its kind. The polar flight transected an unusually cold polar vortex, notable for an associated record-level Arctic ozone loss, and documented polar boundary layer variations over a sizable ocean–ice lead feature. Comparison of dropsonde observations with atmospheric reanalyses reveal that, for this day, large-scale structures such as the polar vortex and air masses are captured by the reanalyses, while smaller-scale features, including low-level jets and inversion depths, are mischaracterized. The successful Arctic dropsonde deployment demonstrates the capability of the Global Hawk to conduct operations in harsh, remote regions. The limited comparison with other measurements and reanalyses highlights the potential value of Arctic atmospheric dropsonde observations where routine in situ measurements are practically nonexistent. 1 Introduction Recently observed changes in the Arctic environment, most notably the diminishing summer sea ice and the expansion of open-water regions (Stroeve et al., 2012), are facilitating increased access to high-latitude ocean areas. This increased activity elevates the need for observations and information to support ecosystem, environmental, social, and economic decision-making. The most recent projections show that the Arctic Ocean could be nearly ice-free in summer near mid-century (Wang and Overland, 2012), affecting Published by Copernicus Publications on behalf of the European Geosciences Union. 3918 J. M. Intrieri et al.: Global Hawk dropsonde observations marinetransportation, regional weather, fisheries and ecosystem structures, energy and natural resource management, and coastal communities. In addition to sea ice loss being a major driver of significant Arctic system-wide changes, there exists the potential for impacts on midlatitude weather systems and long-term climate (e.g., Cohen et al., 2014). Understanding the changing Arctic system and its impacts on weather and climate requires routine observation of the Arctic atmosphere, ocean, and sea ice; process-level understanding and improved coupled atmosphere–ice–ocean forecast models; and the development of services and information products needed by stakeholders and decision-makers. The Arctic environment is remote, expansive, challenging to operate in, lacking in atmospheric observations, and changing regionally at a rapid pace. For these reasons, the use of unmanned aircraft systems (UASs) can be of great benefit toward improving our understanding of Arctic weather and climate. In particular, the range, altitude, and endurance capabilities of larger UASs can fill a critical gap in the Arctic regions where profiles of the atmospheric state are extremely limited. Ultimately, routine UAS observations can result in improvements in understanding and predicting key interactions between the ocean, atmosphere, and sea ice systems by (1) providing evaluation data sets for atmospheric reanalysis products; (2) validating model simulation results and satellite data products; and (3) obtaining measurements that can be assimilated into numerical weather prediction models to improve polar weather, marine, and sea ice forecasts. In this paper, we present measurements obtained in the Arctic during the Winter Storms and Pacific Atmospheric Rivers (WISPAR) field campaign. In February and March of 2011, the Global Hawk (GH) UAS was deployed over the Pacific Ocean and the Arctic in science missions that were designed to (1) improve our scientific understanding of Pacific weather systems and the polar atmosphere; (2) evaluate the operational use of unmanned aircraft for investigating atmospheric events over remote data-sparse regions; and (3) demonstrate and test the newly developed Global Hawk dropsonde system. The Global Hawk is classified as a highaltitude, long-endurance (HALE) UAS platform which distinguishes it from other UASs that are smaller, fly at lower altitudes, carry less weight in payload, and have vastly limited ranges in comparison. Here, we present details of the WISPAR Arctic mission (one of three Global Hawk flights obtained during WISPAR), which was the first successful high-altitude and high-latitude UAS mission with dropsonde capability. This high-Arctic flight allows us to provide examples of the benefits of UAS dropsonde measurements for evaluating concurrent ground-based observations, comparing results of reanalyses data sets, and understanding the Arctic atmospheric features from the polar vortex to boundary layer structures. 2 Atmos. Meas. Tech., 7, 3917–3926, 2014 The Global Hawk UAS and dropsonde measurement system The National Oceanic and Atmospheric Administration (...truncated)