A. R. Klekociuk

The Deep Propagating Gravity Wave Experiment (DEEPWAVE): An Airborne and Ground-Based Exploration of Gravity Wave Propagation and Effects from Their Sources throughout the Lower and Middle Atmosphere

AbstractThe Deep Propagating Gravity Wave Experiment (DEEPWAVE) was designed to quantify gravity wave (GW) dynamics and effects from orographic and other sources to regions of dissipation at high altitudes. The core DEEPWAVE field phase took place from May through July 2014 using a comprehensive suite of airborne and ground-based instruments providing measurements from Earth’s surface to ∼100 km. Austral winter was chosen to observe deep GW propagation to high altitudes. DEEPWAVE was based on South Island, New Zealand, to provide access to the New Zealand and Tasmanian “hotspots” of GW activity and additional GW sources over the Southern Ocean and Tasman Sea. To observe GWs up to ∼100 km, DEEPWAVE utilized three new instruments built specifically for the National Science Foundation (NSF)/National Center for Atmospheric Research (NCAR) Gulfstream V (GV): a Rayleigh lidar, a sodium resonance lidar, and an advanced mesosphere temperature mapper. These measurements were supplemented by in situ probes, dropson...

Monthly Diurnal Global Atmospheric Circuit Estimates Derived from Vostok Electric Field Measurements Adjusted for Local Meteorological and Solar Wind Influences

AbstractLocal temperature, wind speed, pressure, and solar wind–imposed influences on the vertical electric field observed at Vostok, Antarctica, are evaluated by multivariate analysis. Local meteorology can influence electric field measurements via local conductivity. The results are used to improve monthly diurnal averages of the electric field attributable to changes in the global convective storm contribution to the ionosphere-to-earth potential difference. Statistically significant average influences are found for temperature (−0.47 ± 0.13% V m−1 °C−1) and wind speed [2.1 ± 0.5% V m−1 (m s−1)−1]. Both associations are seasonally variable. After adjusting the electric field values to uniform meteorological conditions typical of the Antarctic plateau winter (−70°C, 4.4 m s−1, and 623 hPa), the sensitivity of the electric field to the solar wind external generator influence is found to be 0.80 ± 0.07 V m−1 kV−1. This compares with the sensitivity of 0.82 V m−1 kV−1 to the convective meteorology generato...

Radiosonde observations of gravity waves in the lower stratosphere over Davis, Antarctica

Radiosonde observations made from Davis station, Antarctica, (68.6°S, 78.0°E) between 2001 and 2012 are used to compile a climatology of lower stratosphere inertial gravity wave characteristics. Wavelet analysis extracts single wave packets from the wind and temperature perturbations. Wavelet parameters, combined with linear gravity wave theory, allow for the derivation of a wide range of wave characteristics. Observational filtering associated with this analysis preferentially selects inertial gravity waves with vertical wavelengths less than 2–3 km. The vertical propagation statistics show strong temporal and height variations. The waves propagate close to the horizontal and are strongly advected by the background wind in the wintertime. Notably, around half of the waves observed in the stratosphere above Davis between early May and mid-October propagate downward. This feature is distributed over the observed stratospheric height range. Based on the similarity between the upward and downward propagating waves and on the vertical structure of the nonlinear balance residual in the polar winter stratosphere, it is concluded that a source due to imbalanced flow that is distributed across the winter lower stratosphere best explains the observations. Calculations of kinetic and potential energies and momentum fluxes highlight the potential for variations in results due to different analysis techniques.

Low Ozone Over Southern Australia in August 2011 and its Impact on Solar Ultraviolet Radiation Levels

During August 2011 stratospheric ozone over much of Southern Australia dropped to very low levels (approximately 265 Dobson Units) for over a week above major population centers. The weather during this low ozone period was mostly clear and sunny, resulting in measured solar ultraviolet radiation (UVR) levels up to 40% higher than normal, with UV Index > 3 despite being winter. Satellite ozone measurements and meteorological assimilated data indicate that the event was likely due in large part to the anomalous southward movement over Australia of ozone‐poor air in the lower stratosphere originating from tropical latitudes. At the time, a study measuring the UVR exposures of outdoor workers in Victoria was underway and a number of the workers recorded substantial UVR exposures and were sunburnt. Given the cities and populations involved (approximately 10 million people), it is likely that many people could have been exposed to anomalously high levels of solar UVR for that time of year, with resultant higher UVR exposures and sunburns to unacclimatized skin (often a problem transitioning from low winter to higher spring UVR levels). Reporting procedures have been modified to utilize ozone forecasts to warn the public of anomalously high UVR levels in the future.

Automatically guiding a telescope to a laser beam on a biaxial antarctic light detection and ranging system

The operating principle of atmospheric Rayleigh LIDAR (light detection and ranging) systems is that the range-corrected return-backscatter signal is directly related to atmospheric density. For this to be the case full overlap is required between the backscattered laser signal and the field of view of the receive telescope. Time-dependent errors in this alignment compromise the experimental method, and confuse the interpretation of geophysical signals present in the data. We describe a means of locking the alignment of a small LIDAR telescope to the backscattered laser beam, using images obtained with a commercial charge-coupled device camera, to reduce the effects of relative movement of telescope and laser on field overlap. This “autoguiding” system is implemented on a biaxial Rayleigh LIDAR in operation in Antarctica. We achieve a positional precision near 3 camera pixels (1 pixel~1 arc second) across the beam, and 7 camera pixels along the beam. Positional corrections are generated once per minute. The system is capable of removing medium- and long-term drifts in the relative alignment of our telescope and laser during an observing run.

Parameters of the O(1S) excitation process deduced from photometer measurements of pulsating aurora

Abstract Intensity time-series of the 427.8 nm N 2 + (1NG) (0,1) band and 557.7 nm O( 1 S- 1 D) line emissions were obtained with 0.05 s time resolution during intervals of pulsating aurora. Using an impulse response function analysis technique in conjunction with synthetic intensity time-series constructed using measured data, we estimate the influence of measurement noise and a non-linear component of the covariance between the 557.7 nm and 427.8 nm intensity time-series on the inferred parameters of an O( 1 S) indirect excitation model. Non-linear effects had no additional influence beyond that of measurement noise on estimates of an indirect process. After accounting for the influence of measurement noise, indirect excitation accounts for between 30% and 100% of O( 1 S) production, with an average for our measurements of 58%. The average effective lifetime of the species responsible for the indirect excitation process is 0.13 s. The average percentage contribution from the indirect process is 14% lower, and the effective lifetime slightly longer, than values obtained when noise is not accounted for. Non-linearities between the auroral emissions limit the determination of the O( 1 S) effective lifetime by this technique. We obtain an O( 1 S) effective lifetime distribution with a mean of 0.71 s and a sharp cut-off at the radiative lifetime of ∼0.80 s. O( 1 S) state effective lifetimes decrease as average incident electron energies, determined from the relative O( 1 S- 1 D) and N 2 + (1NG) intensities, increase. Collisional deactivation of the O( 1 S) state can account for only of the order of 55% of the energy dependence of the O( 1 S- 1 D) and N 2 + (1NG) intensity ratio.