Egger J.,Ludwig Maximilians University of Munich |
Hoinka K.-P.,Institute for Atmospheric Physics |
Spengler T.,University of Bergen
Journal of the Atmospheric Sciences
Some aspects of the dynamics of generalized potential vorticity (PV) density P = ω · ∇χ are discussed with the main emphasis on P fluxes, where ωa is absolute vorticity and χ is a scalar. The impermeability theorem claims that there is no net P flux across a χ surface. Various forms of the flux are presented that mostly cross χ surfaces. As these fluxes are as dynamically relevant as the one chosen for the theorem, P fluxes through a surface element are inherently multivalued and there is no best choice on physical grounds. Nevertheless, the net P flux is unique for closed surfaces. This point is illustrated by P integrals over the volume between the earth's surface and an isentropic surface. Reanalysis data are used to present mean advective and some nonadvective P fluxes for χ = θ in height coordinates. The extratropical tropopause appears to be supported by advective P fluxes. A satisfactorily closed P budget cannot, however, be presented. © 2015 American Meteorological Society. Source
Stevens M.H.,U.S. Navy |
Deaver L.E.,GATS, Inc. |
Hervig M.E.,GATS, Inc. |
Russell J.M.,Hampton University |
And 6 more authors.
Journal of Geophysical Research: Atmospheres
Temperature observations in the polar mesosphere and lower thermosphere are critical for studies of polar mesospheric cloud (PMC) formation and variability. The Solar Occultation for Ice Experiment (SOFIE) on NASA's Aeronomy of Ice in the Mesosphere (AIM) satellite has been measuring temperatures in the polar atmosphere nearly continuously since 2007. We herein present an improved SOFIE temperature data set and validate it against a variety of satellite and ground-based observations. We find that when taking all comparisons together, SOFIE temperatures are in agreement with independent observations to within reported systematic uncertainties from 15 to 88km altitude. Between 88 and 95km SOFIE temperatures have a warm bias that peaks between 10 and 15K in the Arctic summer and 20-30K in the Antarctic summer. Much of the warm bias is likely related to uncertainties in prescribed atomic oxygen densities that are required for the SOFIE temperature retrieval. © 2012. American Geophysical Union. All Rights Reserved. Source
Friedrich M.,University of Graz |
Torkar K.M.,Austrian Academy of Sciences |
Hoppe U.-P.,Norwegian Defence Research Establishment |
Hoppe U.-P.,University of Oslo |
And 4 more authors.
The ECOMA (Existence and Charge state Of Meteoric dust grains in the middle Atmosphere) series of sounding rocket flights consisted of nine flights with almost identical payload design and flight characteristics. All flights carried a radio wave propagation experiment together with a variety of plasma probes. Three of these measured electron densities, two ion densities. The rockets were all launched from the Andøya Rocket Range, Norway, in four campaigns between 2006 and 2010. Emphasis is on the final three flights from 2010 where the payloads were equipped with four instruments capable of measuring plasma densities in situ, among them a novel probe flown for the first time in conjunction with a wave propagation experiment. Deviation factors of all probe data relative to the wave propagation results were derived and revealed that none of the probe data were close to the wave propagation results at all heights, but - more importantly - the instruments showed very different behaviour at different altitudes. The novel multi-needle Langmuir probe exhibits the best correlation to the wave propagation data, as there is minimal influence of the payload potential, but it is still subject to aerodynamics, especially at its location at the rear of the payload. For all other probe types, the deviation factor comes closer to unity with increasing plasma density. No systematic difference of the empirical deviation factor between day and night can be found. The large negative payload potential in the last three flights may be the cause for discrepancies between electron and ion probe data below 85 km. © Author(s) 2013. Source
Fritts D.C.,GATS, Inc. |
Pautet P.-D.,Utah State University |
Bossert K.,GATS, Inc. |
Taylor M.J.,Utah State University |
And 5 more authors.
Journal of Geophysical Research D: Atmospheres
An Advanced Mesosphere Temperature Mapper and other instruments at the Arctic Lidar Observatory for Middle Atmosphere Research in Norway (69.3°N) and at Logan and Bear Lake Observatory in Utah (42°N) are used to demonstrate a new method for quantifying gravity wave (GW) pseudo-momentum fluxes accompanying spatially and temporally localized GW packets. The method improves on previous airglow techniques by employing direct characterization of the GW temperature perturbations averaged over the OH airglow layer and correlative wind and temperature measurements to define the intrinsic GW properties with high confidence. These methods are applied to two events, each of which involves superpositions of GWs having various scales and character. In each case, small-scale GWs were found to achieve transient, but very large, momentum fluxes with magnitudes varying from ~60 to 940 m2 s-2, which are ~1-2 decades larger than mean values. Quantification of the spatial and temporal variations of GW amplitudes and pseudo-momentum fluxes may also enable assessments of the total pseudo-momentum accompanying individual GW packets and of the potential for secondary GW generation that arises from GW localization. We expect that the use of this method will yield key insights into the statistical forcing of the mesosphere and lower thermosphere by GWs, the importance of infrequent large-amplitude events, and their effects on GW spectral evolution with altitude. © 2014. American Geophysical Union. All Rights Reserved. Source
Stevens M.H.,U.S. Navy |
Lossow S.,Karlsruhe Institute of Technology |
Lossow S.,Chalmers University of Technology |
Fiedler J.,Institute for Atmospheric Physics |
And 14 more authors.
Journal of Geophysical Research: Atmospheres
The space shuttle launched for the last time on 8 July 2011. As with most shuttle launches, the three main engines injected about 350t of water vapor between 100 and 115km off the east coast of the United States during its ascent to orbit. We follow the motion of this exhaust with a variety of satellite and ground-based data sets and find that (1) the shuttle water vapor plume spread out horizontally in all directions over a distance of 3000 to 4000km in 18h, (2) a portion of the plume reached northern Europe in 21h to form polar mesospheric clouds (PMCs) that are brighter than over 99% of all PMCs observed in that region, and (3) the observed altitude dependence of the particle size is reversed with larger particles above smaller particles. We use a one-dimensional cloud formation model initialized with predictions of a plume diffusion model to simulate the unusually bright PMCs. We find that eddy mixing can move the plume water vapor down to the mesopause near 90km where ice particles can form. If the eddy diffusion coefficient is 400 to 1000m2/s, the predicted integrated cloud brightness is in agreement with both satellite and ground-based observations of the shuttle PMCs. The propellant mass of the shuttle is about 20% of that from all vehicles launched during the northern 2011 PMC season. We suggest that the brightest PMC population near 70N is formed by space traffic exhaust. © 2012 American Geophysical Union. All Rights Reserved. Source