Ekholm Alexander K.

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Ekholm
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Alexander K.
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  • Article
    The air-launched autonomous micro observer
    (American Meteorological Society, 2022-04-01) Jayne, Steven R. ; Owens, W. Brechner ; Robbins, Pelle E. ; Ekholm, Alexander K. ; Bogue, Neil M. ; Sanabia, Elizabeth
    The Air-Launched Autonomous Micro Observer (ALAMO) is a versatile profiling float that can be launched from an aircraft to make temperature and salinity observations of the upper ocean for over a year with high temporal sampling. Similar in dimensions and weight to an airborne expendable bathythermograph (AXBT), but with the same capability as Argo profiling floats, ALAMOs can be deployed from an A-sized (sonobuoy) launch tube, the stern ramp of a cargo plane, or the door of a small aircraft. Unlike an AXBT, however, the ALAMO float directly measures pressure, can incorporate additional sensors, and is capable of performing hundreds of ocean profiles compared to the single temperature profile provided by an AXBT. Upon deployment, the float parachutes to the ocean, releases the air-deployment package, and immediately begins profiling. Ocean profile data along with position and engineering information are transmitted via the Iridium satellite network, automatically processed, and then distributed by the Global Telecommunications System for use by the operational forecasting community. The ALAMO profiling mission can be modified using the two-way Iridium communications to change the profiling frequency and depth. Example observations are included to demonstrate the ALAMO’s utility.
  • Article
    Results of the first Arctic Heat Open Science Experiment
    (American Meteorological Society, 2018-04-19) Wood, Kevin R. ; Jayne, Steven R. ; Mordy, Calvin W. ; Bond, Nicholas A. ; Overland, James E. ; Ladd, Carol ; Stabeno, Phyllis J. ; Ekholm, Alexander K. ; Robbins, Pelle E. ; Schreck, Mary-Beth ; Heim, Rebecca ; Intrieri, Janet
    Seasonally ice-covered marginal seas are among the most difficult regions in the Arctic to study. Physical constraints imposed by the variable presence of sea ice in all stages of growth and melt make the upper water column and air–sea ice interface especially challenging to observe. At the same time, the flow of solar energy through Alaska’s marginal seas is one of the most important regulators of their weather and climate, sea ice cover, and ecosystems. The deficiency of observing systems in these areas hampers forecast services in the region and is a major contributor to large uncertainties in modeling and related climate projections. The Arctic Heat Open Science Experiment strives to fill this observation gap with an array of innovative autonomous floats and other near-real-time weather and ocean sensing systems. These capabilities allow continuous monitoring of the seasonally evolving state of the Chukchi Sea, including its heat content. Data collected by this project are distributed in near–real time on project websites and on the Global Telecommunications System (GTS), with the objectives of (i) providing timely delivery of observations for use in weather and sea ice forecasts, for model, and for reanalysis applications and (ii) supporting ongoing research activities across disciplines. This research supports improved forecast services that protect and enhance the safety and economic viability of maritime and coastal community activities in Alaska. Data are free and open to all (see www.pmel.noaa.gov/arctic-heat/).
  • Article
    Observations of the upper ocean from autonomous platforms during the passage of extratropical Cyclone Epsilon (2020)
    (Oceanography Society, 2024-03-18) Zimmerman, Michael T. ; Jayne, Steven R. ; Rainville, Luc ; Lee, Craig M. ; Toole, John M. ; Edson, James B. ; Clayson, Carol Anne ; Ekholm, Alexander K. ; Densmore, Casey R.
    Hurricane Epsilon (2020) was a late-season, category-3 tropical cyclone that underwent extratropical transition and became Extratropical Cyclone Epsilon on October 26. The upper ocean response to the passage of the storm was observed by three types of autonomous platforms: an eXpendable Spar buoy, an Air-Launched Autonomous Micro-Observer profiling float, and two Seagliders. Taken together, this array enabled the rare collection of contemporaneous observations of the upper ocean, air-sea interface, and atmospheric boundary layer before, during, and after the passage of the storm. The evidence presented suggests that Extratropical Cyclone Epsilon contributed to breaking down the residual North Atlantic summer stratification regime and accelerated the shift to the prolonged ocean cooling associated with winter. The synergistic capabilities of the observational array are significant for two reasons: (1) by enabling the comparison of complementary atmosphere and ocean observations, taken from different platforms, they permit a comprehensive approach to better understand how storm-induced momentum, heat, and moisture fluxes alter upper ocean structure, and (2) they demonstrate the ability of future, targeted deployments of similar observational arrays to assess the fidelity of coupled ocean-atmosphere-wave numerical prediction models.