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The coupling between the neutral and ionized atmosphere is important to improve our understanding of the dynamics of the upper atmosphere and thus improving the prediction of space weather. The Arctic atmosphere is a natural laboratory for understanding these processes. The High-frequency Active Auroral Research Program (HAARP) facility located in Gakona Alaska hosts many scientific instruments that can be used for active experiments. An all-solid state Iron Resonance Temperature Lidar system is under development to be deployed at HAARP to enrich the capability of the HAARP facility. We present recent developments of this lidar system. Progress has been made on the development of the transmitter, and the etalon-based laser frequency monitoring system. We are modifying a commercial Nd:YAG laser to operate at 1116 nm. We have achieved broadband lasing at 1116 nm with 1mJ at 100 Hz in long-pulse mode. The 1116 nm laser will be Q-switched and injection seeded to yield narrowband high power emission. The light will then be tripled to 372 nm and serve as the lidar transmitter. Using a frequency-lock Rb laser, we demonstrate accurate monitoring of the laser’s frequency differences when locked to different Doppler free features with errors <1 MHz. This will support the measurement of temperature with this lidar. 

Abstract Oceanic ctenophores are widespread predators on pelagic zooplankton. While data on coastal ctenophores often show strong top-down predatory impacts in their ecosystems, differing morphologies, prey capture mechanisms and behaviors of oceanic species preclude the use of coastal data to draw conclusion on oceanic species. We used high-resolution imaging methods both in situ and in the laboratory to quantify interactions of Ocyropsis spp. with natural copepod prey. We confirmed that Ocyropsis spp. uses muscular lobe contraction and a prehensile mouth to capture prey, which is unique amongst ctenophores. This feeding mechanism results in high overall capture success whether encountering single or multiple prey between the lobes (71 and 81% respectively). However, multiple prey require several attempts for successful capture whereas single prey are often captured on the first attempt. Digestion of adult copepods takes 44 min at 25 °C and does not vary with ctenophore size. At high natural densities, we estimate that Ocyropsis spp. consume up to 40% of the daily copepod standing stock. This suggests that, when numerous, Ocyropsis spp. can exert strong top-down control on oceanic copepod populations. At more common densities, these animals consume only a small proportion of the daily copepod standing stock. However, compared to data from pelagic fishes and oceanic medusae, Ocyropsis spp. appears to be the dominant copepod predator in this habitat. 

A narrowband sodium resonance wind-temperature lidar (SRWTL) has been deployed at Poker Flat Research Range, Chatanika, Alaska (PFRR, 65° N, 147° W). Based on the Weber narrowband SRWTL, the PFRR SRWTL transmitter was upgraded with a state-of-the-art solid-state tunable diode laser as the seed laser. The PFRR SRWTL currently makes simultaneous measurements in the zenith and 20° off-zenith towards the north with two transmitted beams and two telescopes. Initial results for both nighttime and daytime measurements are presented. We review the performance of the PFRR SRWTL in terms of seven previous and currently operating SRWTLs. The transmitted power from the pulsed dye amplifier (PDA) is comparable with other SRWTL systems (900 mW). However, while the efficiency of the seeding and frequency shifting is comparable to other SRWTLs the efficiency of the pumping is lower. The uncertainties of temperature and wind measurements induced by photon noise at the peak of the layer with a 5 min, 1 km resolution are estimated to be ~1 K and 2 m/s for nighttime conditions, and 10 K and 6 m/s for daytime conditions. The relative efficiency of the zenith receiver is comparable to other SRWTLs (90–97%), while the efficiency of the north off-zenith receiver needs further optimization. An upgrade of the PFRR SRWTL to a full three-beam system with zenith, northward and eastward measurements is in progress.