S. D. Eckermann et al., Antarctic nitric acid trihydrate PC belt of June 2003: Observational validation of the mountain wave seeding hypothesis

Geophysical Research Letters, 36, L02807; doi:10.1029/2008GL036629.

Antarctic NAT PSC belt of June 2003: Observational validation of the mountain wave seeding hypothesis

Antarctic NAT PSC belt of June 2003: Observational validation of the mountain wave seeding hypothesis

S. D. Eckermann (Space Science Division, Naval Research Laboratory, Washington, DC, USA), L. Hoffmann (Forschungszentrum Jülich, Jülich, Germany), M. Höpfner (Forschungszentrum Karlsruhe, Karlsruhe, Germany), D. L. Wu (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA), and M. J. Alexander (Northwest Research Associates, Boulder, CO, USA)

Satellite observations of polar stratospheric clouds (PSCs) over Antarctica in June 2003 revealed small nitric acid trihydrate (NAT) particles forming suddenly along the vortex edge. Models suggest the trigger was mountain waves over the Antarctic Peninsula (AP) forming ice for NAT nucleation. We test this hypothesis by analyzing perturbations in stratospheric radiances from the Atmospheric Infrared Sounder (AIRS). AIRS data show mountain waves over the AP on 10–14 June, with no resolved wave activity before or after. Peak wave temperature amplitudes derived from independent 40 hPa channels all return values of 10–12 K, in agreement with values used to model this NAT event. These observations support a NAT wake from a small region of mountain wave activity over the AP as the source of this circumpolar NAT outbreak.

(Received 10 November 2008; accepted 12 December 2008; published 22 January 2009.)

Citation: Eckermann, S. D., L. Hoffmann, M. Höpfner, D. L. Wu, and M. J. Alexander (2009), Antarctic NAT PSC belt of June 2003: Observational validation of the mountain wave seeding hypothesis, Geophys. Res. Lett., 36, L02807, doi:10.1029/2008GL036629.

Link to abstract: http://www.agu.org/pubs/crossref/2009/2008GL036629.shtml

P. Preusse et al., Transparency of the atmosphere to short horizontal wavelength gravity waves

Journal of Geophysical Research -- Atmospheres, 113, D24104, doi:10.1029/2007JD009682.

Transparency of the atmosphere to short horizontal wavelength gravity waves

Transparency of the atmosphere to short horizontal wavelength gravity waves

Peter Preusse (Institut für Chemie und Dynamik der Geosphäre, ICG-1: Stratosphäre, Forschungszentrum Jülich GmbH, Jülich, Germany), Stephen D. Eckermann (Space Science Division, Naval Research Laboratory, Washington, DC, USA), and Manfred Ern (Institut für Chemie und Dynamik der Geosphäre, ICG-1: Stratosphäre, Forschungszentrum Jülich GmbH, Jülich, Germany)

Abstract

We use theory and global ray modeling to investigate how the potential of gravity waves to transport momentum flux globally from the lower atmosphere into the mesosphere and lower thermosphere (MLT) varies with horizontal wavelength and ground-based phase speed. Ray modeling is performed using the Gravity Wave Regional or Global Ray Tracer (GROGRAT) interfaced to realistic three-dimensional global winds and temperatures from 0 to 100 km altitude, specified by fusing analysis fields at lower altitudes to GCM results higher up. We focus on gravity waves in the short 10- to 50-km horizontal wavelength range that are unresolved by global models and, according to theory, can transport appreciable momentum flux into the MLT. Ray results for different seasons reproduce some of the limits derived from simple wave theory: that horizontal wavelengths shorter than 10 km tend to be removed by vertical reflection or evanescence at the source and slower phase speeds are more prone to critical level removal, leading to a preference for waves with longer horizontal wavelengths and faster ground-based phase speeds to reach the MLT. These findings are compared to the wavelength scales currently resolved by satellite limb and nadir sounders, highlighting wavelength ranges currently measured and those currently unresolved. A road map is developed for how current and future satellite measurements can be combined to measure the full space-time spectrum of gravity waves relevant to eddy flux deposition and momentum forcing of the global MLT. In particular, recommendations for new satellite measurement strategies that fill current measurement gaps are provided.

(Received 6 December 2007, accepted 18 September 2008, published 16 December 2008.)

Citation: Preusse, P., S. D. Eckermann, and M. Ern (2008), Transparency of the atmosphere to short horizontal wavelength gravity waves, J. Geophys. Res., 113, D24104, doi:10.1029/2007JD009682.

Link to abstract: http://www.agu.org/pubs/crossref/2008/2007JD009682.shtml

M. J. Alexander & H. Teitelbaum: Observation and Analysis of a Large Amplitude Mountain Wave Event over the Antarctic Peninsula

Journal of Geophysical Research, submitted and revised draft of April 27, 2008

Observation and Analysis of a Large-Amplitude Mountain-Wave Event over the Antarctic Peninsula

M. J. Alexander and H. Teitelbaum

Abstract

We use measurements from the Atmospheric Infrared Sounder (AIRS) on the AQUA satellite to observe the 3-dimensional structure of a gravity wave event over the Antarctic peninsula, and determine the horizontal and vertical wavelengths, propagation direction, and temperature amplitude, and from these we estimate wave momentum flux. Using theoretical knowledge of the weighting functions and radiative transfer for AIRS radiance measurements at temperature sensitive channels in the infrared, we derive a method of estimating wave temperature amplitude directly from the radiance measurements. Comparison of the radiance-based temperature amplitudes to the temperature amplitude in AIRS retrieved temperature fields shows close agreement. Because the radiances have 3-times better horizontal resolution than the retrievals, our analysis suggests we can routinely observe important geophysical properties of waves with horizontal wavelengths as short as 80 km using AIRS radiances. We further analyze a nearly identical wave event appearing in the European Centre for Medium Range Forecasts (ECMWF) temperature and wind fields from both assimilation and forecast data. Analysis of the ECMWF data and nearby radiosonde wind profiles allows the interpretation as a mountain wave event forced by flow over the topography of the Antarctic peninsula.

Link to full pdf file of manuscript: http://atmosdyn.yonsei.ac.kr/nrl/seminar/ATrevised0427.pdf