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Fire is a pervasive feature of the tropical savannas of northern Australia. Increasingly extensive and intensive fires have had an adverse effect on grass layer diversity. Reduced grass species diversity and abundance are important... more
Fire is a pervasive feature of the tropical savannas of northern Australia. Increasingly extensive and intensive fires have had an adverse effect on grass layer diversity. Reduced grass species diversity and abundance are important correlates of the decline of granivores in these tropical savannas. The Gouldian finch (Erythrura gouldiae), an endangered species that is endemic to northern Australia, is particularly vulnerable to changes to the grass layer as its diet comprises only grass seed, and it relies mostly on Sorghum stipoideum during the breeding season. Although this annual grass species is abundant at breeding sites, the finches do not always choose to breed at these sites, raising the possibility that seed quality may vary from year to year. This study examines the effect of fire (time since last fire; fire frequency) on soil fertility and seed nutritional quality. We hypothesise that recently burnt sites produce a flush of soil nutrients and Sorghum stipoideum seed at th...
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Observations at the Polar Environment Atmospheric Research Laboratory at Eureka, Nunavut (80N) were taken throughout the winter of 2008/2009. Instrumentation included a wind mea-suring optical interferometer, the E-Region Wind... more
Observations at the Polar Environment Atmospheric Research Laboratory at Eureka, Nunavut (80N) were taken throughout the winter of 2008/2009. Instrumentation included a wind mea-suring optical interferometer, the E-Region Wind Interferometer (ERWIN), a meteor radar, an airglow temperature imager (the Spectral Airglow Temperature Imager SATI), an all-sky imager, and an ozone lidar. Together they provided observations of conditions above Eureka during
Research Interests: Satellite Data and Ozone
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... Charmaine N. Mchunu Simon Lorentz Graham Jewitt School of Bioresources Engineering and Environmental Hydrology, Rabie Saunders Bldg., Univ. ... and splash erosion break down soil aggregates, thus making SOC more accessible to the... more
... Charmaine N. Mchunu Simon Lorentz Graham Jewitt School of Bioresources Engineering and Environmental Hydrology, Rabie Saunders Bldg., Univ. ... and splash erosion break down soil aggregates, thus making SOC more accessible to the living de-composers, therefore T is ...
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Planetary and tidal wave activity in the mesosphere-lower thermosphere (MLT), and assessment of wave activity sources in the lower atmosphere, are studied using combinations of ground based (GB) and satellite instruments (2000-2002). CUJO... more
Planetary and tidal wave activity in the mesosphere-lower thermosphere (MLT), and assessment of wave activity sources in the lower atmosphere, are studied using combinations of ground based (GB) and satellite instruments (2000-2002). CUJO (Canada U.S. Japan Opportunity) comprises MF radar (MFR) systems at London (43°N, 81°W), Platteville (40°N, 105°W), Saskatoon (52°N, 107°W), Wakkanai (45°N, 142°E) and Yamagawa (31°N, 131°E). It
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Daily experimental data, measured by stations in Collm (52N 15E, LF D1 radar, 1993-2001 years), Kazan (56N 49E, meteor radar, 1993-2001 years) and Saskatoon (52N 103W, MST radar, 1993-2001 years) in the height range 80-100 km, and... more
Daily experimental data, measured by stations in Collm (52N 15E, LF D1 radar, 1993-2001 years), Kazan (56N 49E, meteor radar, 1993-2001 years) and Saskatoon (52N 103W, MST radar, 1993-2001 years) in the height range 80-100 km, and Assimilated Wind Data from the British Atmospheric Data Center in the height range 0-55 km (55N, 0-360 degrees by longitude, 1992-2001 years) are
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For the study of middle atmosphere circulation characteristics data sets from observatories which have operated for many years have been mainly used: Collm (52N 15E, LF D1 radar, 1993-2001 years), Kazan (56N 49E, meteor radar, 1986 - 2001... more
For the study of middle atmosphere circulation characteristics data sets from observatories which have operated for many years have been mainly used: Collm (52N 15E, LF D1 radar, 1993-2001 years), Kazan (56N 49E, meteor radar, 1986 - 2001 years) and Saskatoon (52N 107W, MF radar, 1985-2001 years) in the height range 80-100 km. Wind data from the British Atmospheric Data
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The large V/m electric fields inherent in the mesosphere play an essential role in lower ionospheric electrodynamics. They must be the cause of large variations in the electron temperature and the electron collision frequency at D region... more
The large V/m electric fields inherent in the mesosphere play an essential role in lower ionospheric electrodynamics. They must be the cause of large variations in the electron temperature and the electron collision frequency at D region altitudes, and consequently the ionospheric plasma in the lower part of the D region undergoes a transition into a nonisothermal state. This study
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EWIN-2 (E-Region Wind Interferometer) is a field-widened Michelson interferometer that is used to measure winds in the mesopause (90 km). ERWIN-2 measures Doppler shifts in the hydroxyl, green-line, and O2 airglow emissions to determine... more
EWIN-2 (E-Region Wind Interferometer) is a field-widened Michelson interferometer that is used to measure winds in the mesopause (90 km). ERWIN-2 measures Doppler shifts in the hydroxyl, green-line, and O2 airglow emissions to determine the winds. A quad mirror in the optical system allows for simultaneous measurement of five viewing directions. This results in an observation cadence of 2 minutes
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The HWM90 thermospheric wind model was revised in the lower thermosphere and extended into the mesosphere and lower atmosphere to provide a single analytic model for calculating zonal and meridional wind profiles representative of the... more
The HWM90 thermospheric wind model was revised in the lower thermosphere and extended into the mesosphere and lower atmosphere to provide a single analytic model for calculating zonal and meridional wind profiles representative of the climatological average for various geophysical conditions. Gradient winds from CIRA-86 plus rocket soundings, incoherent scatter radar, MF radar, and meteor radar provide the data base
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During the CEDAR-TIMED storm campaign in April 2002, Medium Frequency and Meteor Wind radars at more than 20 worldwide locations provided continuous wind measurements in the altitude range of 80-100 km. Preliminary results show that the... more
During the CEDAR-TIMED storm campaign in April 2002, Medium Frequency and Meteor Wind radars at more than 20 worldwide locations provided continuous wind measurements in the altitude range of 80-100 km. Preliminary results show that the zonal mean winds and amplitudes of the diurnal tide at low latitudes, such as at Kauai (22N) and Rarotonga (22S), are much larger during
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Winds from the mesopause region have now been analyzed for 12 months, Feb 2006-Jan 2007. Spectral and harmonic analyses have been used to obtain the amplitudes and phases of the solar tides (24-, 12-, 8-hrs) for each of the months and at... more
Winds from the mesopause region have now been analyzed for 12 months, Feb 2006-Jan 2007. Spectral and harmonic analyses have been used to obtain the amplitudes and phases of the solar tides (24-, 12-, 8-hrs) for each of the months and at heights of 80-100km. There are many surprises; in particular the amplitudes of the 12- and 24-hr tides are
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An important aspect of the wind dynamics in the mesosphere is to know characteristics of the atmospheric gravity waves, such as propagation direction, zonal and meridional wavenumbers, horizontal wavelength, apparent phase speed, and... more
An important aspect of the wind dynamics in the mesosphere is to know characteristics of the atmospheric gravity waves, such as propagation direction, zonal and meridional wavenumbers, horizontal wavelength, apparent phase speed, and intensity perturbation amplitude, because it is widely known that the atmospheric gravity waves transport energy and momentum from the lower atmosphere to the mesosphere and the lower
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ABSTRACT [1] Using 5 years of all-sky OH imager data over Yucca Ridge Field Station, CO (40.7°N, 104.9°W) from September 2003 to September 2008, we extract and deduce quasi-monochromatic gravity wave (GW) characteristics. The intrinsic... more
ABSTRACT [1] Using 5 years of all-sky OH imager data over Yucca Ridge Field Station, CO (40.7°N, 104.9°W) from September 2003 to September 2008, we extract and deduce quasi-monochromatic gravity wave (GW) characteristics. The intrinsic periods are clustered between approximately 4-10 min, and many of them are unstable and evanescent. GW occurrence frequency exhibits a clear semi-annual variation with equinoctial minima, which is likely related to the seasonal variation of background wind. The anomalous propagation direction in January 2006, with strong southward before major warming starting on January 21 and weak southward propagation afterwards, was most likely affected by stratospheric sudden warming (SSW). The momentum fluxes show strongly anti-correlated with the tides, with ~180° out of phase in the zonal component. While in the meridional component, the easterly maximum occurred approximately 2-6 h after maximum westerly tides. However, the anti-correlations are both weakest during the summer. The dissipating and breaking of small scale and high frequency GW's components could have a potential impact on the general circulation in the mesopause region.
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Based on the MF radar data obtained at Tromsø (69.6N, 19.2E) for about 3 years occurring between November 1, 1998 and November 30, 2001, we have examined a seasonal variation of quasi 2-day wave in the polar mesosphere from 70 to 91 km... more
Based on the MF radar data obtained at Tromsø (69.6N, 19.2E) for about 3 years occurring between November 1, 1998 and November 30, 2001, we have examined a seasonal variation of quasi 2-day wave in the polar mesosphere from 70 to 91 km height. The quasi 2 day wave signature is always found in winter months over the whole height
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While chemical ozone depletion in the Antarctic spring-time stratosphere is now an annually occurring and well-understood phenomenon, dynamical variability in the Arctic stratosphere means ozone depletion in the northern polar vortex is... more
While chemical ozone depletion in the Antarctic spring-time stratosphere is now an annually occurring and well-understood phenomenon, dynamical variability in the Arctic stratosphere means ozone depletion in the northern polar vortex is both less predictable and more susceptible to changes resulting from climate change than in the southern vortex. In order to examine ozone-depleting processes and quantify chemical changes occurring
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... In this paper we assess global PW variability in the stratosphere and MLT using MetOa ... variation due to changes made to NOAA-16 processing, which affected the data at upper ... during solstice seasons create strong stratospheric... more
... In this paper we assess global PW variability in the stratosphere and MLT using MetOa ... variation due to changes made to NOAA-16 processing, which affected the data at upper ... during solstice seasons create strong stratospheric winds according to the thermal wind equation. ...
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EWIN-2 (E-Region Wind Interferometer) is a field-widened Michelson interferometer that is used to measure winds in the mesopause (90 km). ERWIN-2 measures Doppler shifts in the hydroxyl, green-line, and O2 airglow emissions to determine... more
EWIN-2 (E-Region Wind Interferometer) is a field-widened Michelson interferometer that is used to measure winds in the mesopause (90 km). ERWIN-2 measures Doppler shifts in the hydroxyl, green-line, and O2 airglow emissions to determine the winds. A quad mirror in the optical system allows for simultaneous measurement of five viewing directions. This results in an observation cadence of 2 minutes for all three emissions at a precision of 5 m/s thereby making ERWIN-2 the fastest wind measuring instrument in the world for the mesopause region. Instrument operation, wind observations from January 2009, discussions of zero-wind calibra-tion and vertical wind determination and comparisons with meteor radar, used to validate ERWIN-2 operation and determine emission layer heights, will be presented.