Nitric oxides in the stratosphere — A two dimensional atmospheric model

Abstract This paper presents the first attempt to apply the compressible nonhydrostatic Active Tracer High-Resolution Atmospheric Model–Fluidity (ATHAM-Fluidity) solver to a series of idealized atmospheric test cases. ATHAM-Fluidity uses a hybrid finite-element discretization where pressure is solved on a continuous second-order grid while momentum and scalars are computed on a first-order discontinuous grid (also known as ). ATHAM-Fluidity operates on two- and three-dimensional unstructured meshes, using triangular or tetrahedral elements, respectively, with the possibility to employ an anisotropic mesh optimization algorithm for automatic grid refinement and coarsening during run time. The solver is evaluated using two-dimensional-only dry idealized test cases covering a wide range of atmospheric applications. The first three cases, representative of atmospheric convection, reveal the ability of ATHAM-Fluidity to accurately simulate the evolution of large-scale flow features in neutral atmospheres at rest. Grid convergence without adaptivity as well as the performances of the Hermite–Weighted Essentially Nonoscillatory (Hermite-WENO) slope limiter are discussed. These cases are also used to test the grid optimization algorithm implemented in ATHAM-Fluidity. Adaptivity can result in up to a sixfold decrease in computational time and a fivefold decrease in total element number for the same finest resolution. However, substantial discrepancies are found between the uniform and adapted grid results, thus suggesting the necessity to improve the reliability of the approach. In the last three cases, corresponding to atmospheric gravity waves with and without orography, the model ability to capture the amplitude and propagation of weak stationary waves is demonstrated. This work constitutes the first step toward the development of a new comprehensive limited area atmospheric model.

Download Full-text

Southern hemispheric halon trends and global halon emissions, 1978–2011

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-5551-2013 ◽

2013 ◽

Vol 13 (11) ◽

pp. 5551-5565 ◽

Cited By ~ 14

Author(s):

M. J. Newland ◽

C. E. Reeves ◽

D. E. Oram ◽

J. C. Laube ◽

W. T. Sturges ◽

...

Keyword(s):

Steady State ◽

Atmospheric Model ◽

Production Data ◽

Two Dimensional ◽

Top Down ◽

East Anglia ◽

Mixing Ratios ◽

The Past ◽

Alternative Set ◽

Cape Grim

Abstract. The atmospheric records of four halons, H-1211 (CBrClF2), H-1301 (CBrF3), H-2402 (CBrF2CBrF2) and H-1202 (CBr2F2), measured from air collected at Cape Grim, Tasmania, between 1978 and 2011, are reported. Mixing ratios of H-1211, H-2402 and H-1202 began to decline in the early to mid-2000s, but those of H-1301 continue to increase up to mid-2011. These trends are compared to those reported by NOAA (National Oceanic and Atmospheric Administration) and AGAGE (Advanced Global Atmospheric Experiment). The observations suggest that the contribution of the halons to total tropospheric bromine at Cape Grim has begun to decline from a peak in 2008 of about 8.1 ppt. An extrapolation of halon mixing ratios to 2060, based on reported banks and predicted release factors, shows this decline becoming more rapid in the coming decades, with a contribution to total tropospheric bromine of about 3 ppt in 2060. Top-down global annual emissions of the halons were derived using a two-dimensional atmospheric model. The emissions of all four have decreased since peaking in the late 1980s–mid-1990s, but this decline has slowed recently, particularly for H-1301 and H-2402 which have shown no decrease in emissions over the past five years. The UEA (University of East Anglia) top-down model-derived emissions are compared to those reported using a top-down approach by NOAA and AGAGE and the bottom-up estimates of HTOC (Halons Technical Options Committee). The implications of an alternative set of steady-state atmospheric lifetimes are discussed. Using a lifetime of 14 yr or less for H-1211 to calculate top-down emissions estimates would lead to small, or even negative, estimated banks given reported production data. Finally emissions of H-1202, a product of over-bromination during the production process of H-1211, have continued despite reported production of H-1211 ceasing in 2010. This raises questions as to the source of these H-1202 emissions.

Download Full-text

Atmospheric Simulations of Extreme Surface Heating Episodes on Simple Hills

International Journal of Wildland Fire ◽

10.1071/wf9920099 ◽

1992 ◽

Vol 2 (3) ◽

pp. 99 ◽

Cited By ~ 7

Author(s):

WE Heilman

Keyword(s):

Wildland Fire ◽

Atmospheric Model ◽

Surface Heating ◽

Turbulence Energy ◽

Two Dimensional ◽

Extreme Surface ◽

Turbulence Structures ◽

Roll Vortices ◽

Windward Slope ◽

The Impact

A two-dimensional nonhydrostatic atmospheric model was used to simulate the circulation patterns (wind and vorticity) and turbulence energy fields associated with lines of extreme surface heating on simple two-dimensional hills. Heating-line locations and ambient crossflow conditions were varied to qualitatively determine the impact of terrain geometry on the development of buoyancy-induced horizontal roll vortices and their turbulence structures. The model simulations indicate that the type of induced circulation that develops near a line of extreme surface heating on a simple hill is very dependent on the location of the heating line. Heating lines located on the crests of simple hills produced symmetric horizontal roll vortices with large values of turbulent kinetic energy. Symmetric vortices did not develop over heating lines located on the slopes of the hills. The introduction ofa light ambientcrossflowradically changed the circulation and turbulence structures. Simulated vorticity and turbulence energy values over a heating line located on the windward slope were very different than those observed over heating lines located on the crest or leeward slope. A low-level vortex developed just downwind of the windward-slope heating line when a light ambient crossflow was introduced, and this vortex became stronger as the steepness of the hill was increased. Although field dataare not available toconfirm the model results, the simulations suggest that terrain effects play an important role in the development and destruction of vortices near lines of extreme surface heating, especially when a light ambient crossflow is introduced. These effects have implications for fire-fighter safety in actual wildland fire episodes.

Download Full-text

Hydrogen soil deposition at an urban site in Finland

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-14873-2009 ◽

2009 ◽

Vol 9 (4) ◽

pp. 14873-14899 ◽

Cited By ~ 2

Author(s):

M. Lallo ◽

T. Aalto ◽

J. Hatakka ◽

T. Laurila

Keyword(s):

Deposition Velocity ◽

Atmospheric Model ◽

Photochemical Reactions ◽

Urban Site ◽

Two Dimensional ◽

Tracer Method ◽

Closed Chamber ◽

Radon Exhalation ◽

Soil Deposition ◽

Chamber Measurements

Abstract. Hydrogen deposition velocities (v_d) were estimated by field chamber measurements and model simulations. A closed-chamber method was used for soil deposition studies in Helsinki, Finland, at an urban park inhabited by broad-leaved trees. Radon tracer method was used to estimate the v_d in nighttime when photochemical reactions were minimal and radon gas was concentrated to shallow boundary layer due to exhalation from soil. A two-dimensional atmospheric model was used for calculation of respective v_d values and radon exhalation rate. v_d and radon exhalation rates were lower in winter than in summer according to all methods. The radon tracer method and two-dimensional model results for hydrogen deposition velocity were in the range of 0.13 mm s−1 to 0.90 mm s−1 (radon tracer) and 0.12 mm s−1 to 0.61 mm s−1 (two-dimensional). The soil chamber results for v_d were 0.00 mm s−1 to 0.70 mm s−1. Both models and chamber measurements revealed relation between one week cumulative rain sum and deposition velocity. Lower v_d values were usually measured in high soil moisture conditions. Precipitation occurring a few days before chamber measurements decreased v_d values. The snow cover also lowered v_d.

Download Full-text

The Distribution of Ozone and Active Stratospheric Species: Results of a Two-Dimensional Atmospheric Model

Atmospheric Ozone ◽

10.1007/978-94-009-5313-0_16 ◽

1985 ◽

pp. 77-81 ◽

Cited By ~ 7

Author(s):

D. Cariolle ◽

D. Brard

Keyword(s):

Atmospheric Model ◽

Two Dimensional

Download Full-text

Southern hemispheric halon trends and global halon emissions, 1978–2011

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-29289-2012 ◽

2012 ◽

Vol 12 (11) ◽

pp. 29289-29324 ◽

Cited By ~ 3

Author(s):

M. J. Newland ◽

C. E. Reeves ◽

D. E. Oram ◽

J. C. Laube ◽

W. T. Sturges ◽

...

Keyword(s):

Steady State ◽

Atmospheric Model ◽

Two Dimensional ◽

Top Down ◽

Bottom Up ◽

Mixing Ratios ◽

The Past ◽

Cape Grim

Abstract. The atmospheric records of four halons, H-1211 (CBrClF2), H-1301 (CBrF3), H-2402 (CBrF2CBrF2) and H-1202 (CBr2F2), measured from air collected at Cape Grim, Tasmania between 1978 and 2011, are reported. Mixing ratios of H-1211, H-2402 and H-1202 began to decline in the early to mid-2000s but those of H-1301 continue to increase throughout the record. These trends are compared to those reported by NOAA (National Oceanic and Atmospheric Administration) and AGAGE (Advanced Global Atmospheric Experiment). The continued increase of H-1301 mixing ratios means that the contribution of the halons to total tropospheric bromine is not declining. Top-down global annual emissions of the halons were derived using a two-dimensional atmospheric model. The emissions of all four have decreased since peaking in the late 1980s–mid 1990s but this decline has slowed recently, particularly for H-1301 and H-2402 which have shown no decrease in emissions over the past five years. The UEA top-down model derived emissions are compared to those reported using a top-down approach by NOAA and AGAGE and the bottom-up estimates of HTOC (Halons Technical Options Committee). Additionally results are presented that suggest that H-1202 emissions are linked to H-1211 emissions rather than H-1211 production. Finally revised steady state atmospheric lifetimes are reported as 14 yr for H-1211, 75 yr for H-1301, 17 yr for H-2402 and 2.6 yr for H-1202. These revised lifetimes would reduce the estimated existing bank of H-1211 by over 80% to 10 Gg while increasing the H-1301 bank by 15% to 49 Gg.

Download Full-text

Spectrophotometric measurements of objective-prism spectra

Symposium - International Astronomical Union ◽

10.1017/s007418090005333x ◽

1966 ◽

Vol 24 ◽

pp. 118-119

Author(s):

Th. Schmidt-Kaler

Keyword(s):

Progress Report ◽

Two Dimensional ◽

Objective Prism ◽

Made In

I should like to give you a very condensed progress report on some spectrophotometric measurements of objective-prism spectra made in collaboration with H. Leicher at Bonn. The procedure used is almost completely automatic. The measurements are made with the help of a semi-automatic fully digitized registering microphotometer constructed by Hög-Hamburg. The reductions are carried out with the aid of a number of interconnected programmes written for the computer IBM 7090, beginning with the output of the photometer in the form of punched cards and ending with the printing-out of the final two-dimensional classifications.

Download Full-text

Introductory paper

Symposium - International Astronomical Union ◽

10.1017/s0074180900053031 ◽

1966 ◽

Vol 24 ◽

pp. 3-5

Author(s):

W. W. Morgan

Keyword(s):

Line Intensity ◽

Classification Scheme ◽

Two Dimensional ◽

Spectral Classification ◽

Dimensional Array ◽

Rr Lyrae ◽

Metallic Line ◽

Introductory Paper ◽

Parameter Varying ◽

Definition Of

1. The definition of “normal” stars in spectral classification changes with time; at the time of the publication of theYerkes Spectral Atlasthe term “normal” was applied to stars whose spectra could be fitted smoothly into a two-dimensional array. Thus, at that time, weak-lined spectra (RR Lyrae and HD 140283) would have been considered peculiar. At the present time we would tend to classify such spectra as “normal”—in a more complicated classification scheme which would have a parameter varying with metallic-line intensity within a specific spectral subdivision.

Download Full-text

A one-dimensional self-gravitating stellar gas

Symposium - International Astronomical Union ◽

10.1017/s0074180900105261 ◽

1966 ◽

Vol 25 ◽

pp. 46-48 ◽

Cited By ~ 2

Author(s):

M. Lecar

Keyword(s):

Gravitational Field ◽

Phase Space ◽

Motion Picture ◽

Space Distribution ◽

Two Dimensional ◽

One Dimensional ◽

Phase Space Distribution ◽

Dimensional Phase Space ◽

The Mean

“Dynamical mixing”, i.e. relaxation of a stellar phase space distribution through interaction with the mean gravitational field, is numerically investigated for a one-dimensional self-gravitating stellar gas. Qualitative results are presented in the form of a motion picture of the flow of phase points (representing homogeneous slabs of stars) in two-dimensional phase space.

Download Full-text

Analysis of the 9th November 1990 flare

International Astronomical Union Colloquium ◽

10.1017/s025292110006454x ◽

2000 ◽

Vol 179 ◽

pp. 229-232

Author(s):

Anita Joshi ◽

Wahab Uddin

Keyword(s):

Image Processing ◽

Two Dimensional ◽

Temporal Behaviour ◽

Contour Maps ◽

Dimensional Measurements ◽

Processing Software ◽

Image Processing Software

AbstractIn this paper we present complete two-dimensional measurements of the observed brightness of the 9th November 1990Hαflare, using a PDS microdensitometer scanner and image processing software MIDAS. The resulting isophotal contour maps, were used to describe morphological-cum-temporal behaviour of the flare and also the kernels of the flare. Correlation of theHαflare with SXR and MW radiations were also studied.

Download Full-text