scholarly journals Seasonal variations of the semi-diurnal and diurnal tides in the MLT: multi-year MF radar observations from 2–70° N, modelled tides (GSWM, CMAM)

2002 ◽  
Vol 20 (5) ◽  
pp. 661-677 ◽  
Author(s):  
A. H. Manson ◽  
C. Meek ◽  
M. Hagan ◽  
J. Koshyk ◽  
S. Franke ◽  
...  
Keyword(s):  
General Circulation ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Wave Model ◽  
Global Scale ◽  
Diurnal Tide ◽  
Data Set ◽  
Height Range ◽  
Christmas Island ◽  
Tidal Data

Abstract. In an earlier paper (Manson et al., 1999a) tidal data (1990–1997) from six Medium Frequency Radars (MFR) were compared with the Global Scale Wave Model (GSWM, original 1995 version). The radars are located between the equator and high northern latitudes: Christmas Island (2° N), Hawaii (22° N), Urbana (40° N), London (43° N), Saskatoon (52° N) and Tromsø (70° N). Common harmonic analysis was applied, to ensure consistency of amplitudes and phases in the 75–95 km height range. For the diurnal tide, seasonal agreements between observations and model were excellent while for the semi-diurnal tide the seasonal transitions between clear solstitial states were less well captured by the model. Here the data set is increased by the addition of two locations in the Pacific-North American sector: Yamagawa 31° N, and Wakkanai 45° N. The GSWM model has undergone two additional developments (1998, 2000) to include an improved gravity wave (GW) stress parameterization, background winds from UARS systems and monthly tidal forcing for better characterization of seasonal change. The other model, the Canadian Middle Atmosphere Model (CMAM) which is a General Circulation Model, provides internally generated forcing (due to ozone and water vapour) for the tides. The two GSWM versions show distinct differences, with the 2000 version being either closer to, or further away from, the observations than the original 1995 version. CMAM provides results dependent upon the GW parameterization scheme inserted, but one of the schemes provides very useful tides, especially for the semi-diurnal component.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)

scholarly journals Evaluation of CLaMS, KASIMA and ECHAM5/MESSy1 simulations in the lower stratosphere using observations of Odin/SMR and ILAS/ILAS-II

2009 ◽  
Vol 9 (1) ◽  
pp. 1977-2020
Author(s):  
F. Khosrawi ◽  
R. Müller ◽  
M. H. Proffitt ◽  
R. Ruhnke ◽  
O. Kirner ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
General Circulation ◽  
Lower Stratosphere ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Lagrangian Model ◽  
Data Sets ◽  
Data Set ◽  
The Impact

Abstract. 1-year data sets of monthly averaged nitrous oxide (N2O) and ozone (O3) derived from satellite measurements were used as a tool for the evaluation of atmospheric photochemical models. Two 1-year data sets, one derived from the Improved Limb Atmospheric Spectrometer (ILAS and ILAS-II) and one from the Odin Sub-Millimetre Radiometer (Odin/SMR) were employed. Here, these data sets are used for the evaluation of two Chemical Transport Models (CTMs), the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA) and the Chemical Lagrangian Model of the Stratosphere (CLaMS) as well as for one Chemistry-Climate Model (CCM), the atmospheric chemistry general circulation model ECHAM5/MESSy1 (E5M1) in the lower stratosphere with focus on the Northern Hemisphere. Since the Odin/SMR measurements cover the entire hemisphere, the evaluation is performed for the entire hemisphere as well as for the low latitudes, midlatitudes and high latitudes using the Odin/SMR 1-year data set as reference. To assess the impact of using different data sets for such an evaluation study we repeat the evaluation for the polar lower stratosphere using the ILAS/ILAS-II data set. Only small differences were found using ILAS/ILAS-II instead of Odin/SMR as a reference, thus, showing that the results are not influenced by the particular satellite data set used for the evaluation. The evaluation of CLaMS, KASIMA and E5M1 shows that all models are in good agreement with Odin/SMR and ILAS/ILAS-II. Differences are generally in the range of ±20%. Larger differences (up to −40%) are found in all models at 500±25 K for N2O mixing ratios greater than 200 ppb. Generally, the largest differences were found for the tropics and the lowest for the polar regions. However, an underestimation of polar winter ozone loss was found both in KASIMA and E5M1 both in the Northern and Southern Hemisphere.

scholarly journals Methyl iodide production in the open ocean

2014 ◽  
Vol 11 (16) ◽  
pp. 4459-4476 ◽  
Author(s):  
I. Stemmler ◽  
I. Hense ◽  
B. Quack ◽  
E. Maier-Reimer
Keyword(s):  
Methyl Iodide ◽  
General Circulation ◽  
Circulation Model ◽  
Global Scale ◽  
Global Ocean ◽  
Phytoplankton Production ◽  
Boreal Winter ◽  
Max Planck ◽  
Data Set ◽  
Carbon Cycle Model

Abstract. Production pathways of the prominent volatile organic halogen compound methyl iodide (CH3I) are not fully understood. Based on observations, production of CH3I via photochemical degradation of organic material or via phytoplankton production has been proposed. Additional insights could not be gained from correlations between observed biological and environmental variables or from biogeochemical modeling to identify unambiguously the source of methyl iodide. In this study, we aim to address this question of source mechanisms with a three-dimensional global ocean general circulation model including biogeochemistry (MPIOM–HAMOCC (MPIOM – Max Planck Institute Ocean Model HAMOCC – HAMburg Ocean Carbon Cycle model)) by carrying out a series of sensitivity experiments. The simulated fields are compared with a newly available global data set. Simulated distribution patterns and emissions of CH3I differ largely for the two different production pathways. The evaluation of our model results with observations shows that, on the global scale, observed surface concentrations of CH3I can be best explained by the photochemical production pathway. Our results further emphasize that correlations between CH3I and abiotic or biotic factors do not necessarily provide meaningful insights concerning the source of origin. Overall, we find a net global annual CH3I air–sea flux that ranges between 70 and 260 Gg yr−1. On the global scale, the ocean acts as a net source of methyl iodide for the atmosphere, though in some regions in boreal winter, fluxes are of the opposite direction (from the atmosphere to the ocean).

scholarly journals Diurnal and semidiurnal tide in the upper middle atmosphere during the first year of simultaneous MF radar observations in northern and southern Japan (45°N and 31°N)

1999 ◽  
Vol 17 (3) ◽  
pp. 405-414 ◽  
Author(s):  
K. Hocke ◽  
K. Igarashi
Keyword(s):  
Middle Atmosphere ◽  
Wave Model ◽  
Global Scale ◽  
Diurnal Tide ◽  
First Year ◽  
Semidiurnal Tide ◽  
Tidal Amplitude ◽  
Latitudinal Dependence ◽  
Waves And Tides ◽  
Mf Radar

Abstract. The climatology of mean wind, diurnal and semidiurnal tide during the first year (1996-1997) of simultaneous wind observations at Wakkanai (45.4°N, 141.7°E) and Yamagawa (31.2°N, 130.6°E) is presented. The locations of the radars allow us to describe the latitudinal dependence of the tides. Tidal amplitude and phase profiles are compared with those of the global scale wave model (GSWM). While the observed amplitude profiles of the diurnal tide agree well with the GSWM values, the observed phase profiles often indicate longer vertical wavelengths than the GSWM phase profiles. In contrast to the GSWM simulation, the observations show a strong bimodal structure of the diurnal tide, with the phase advancing about 6 hours from summer to winter.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)

scholarly journals A study into the effect of the diurnal tide on the structure of the background mesosphere and thermosphere using the new coupled middle atmosphere and thermosphere (CMAT) general circulation model

2002 ◽  
Vol 20 (2) ◽  
pp. 225-235 ◽  
Author(s):  
M. J. Harris ◽  
N. F. Arnold ◽  
A. D. Aylward
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Atomic Oxygen ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Lower Boundary ◽  
Circulation Model ◽  
Diurnal Tide ◽  
Temperature Structure ◽  
The Mean

Abstract. A new coupled middle atmosphere and thermosphere general circulation model has been developed, and some first results are presented. An investigation into the effects of the diurnal tide upon the mean composition, dynamics and energetics was carried out for equinox conditions. Previous studies have shown that tides deplete mean atomic oxygen in the upper mesosphere-lower thermosphere due to an increased recombination in the tidal displaced air parcels. The model runs presented suggest that the mean residual circulation associated with the tidal dissipation also plays an important role. Stronger lower boundary tidal forcing was seen to increase the equatorial local diurnal maximum of atomic oxygen and the associated 0(1S) 557.7 nm green line volume emission rates. The changes in the mean background temperature structure were found to correspond to changes in the mean circulation and exothermic chemical heating.Key words. Atmospheric composition and structure (middle atmosphere – composition and chemistry) Meterology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)

scholarly journals Global distributions of diurnal and semidiurnal tides: observations from HRDI-UARS of the MLT region and comparisons with GSWM-02 (migrating, nonmigrating components)

2004 ◽  
Vol 22 (5) ◽  
pp. 1529-1548 ◽  
Author(s):  
A. H. Manson ◽  
C. Meek ◽  
M. Hagan ◽  
X. Zhang ◽  
Y. Luo
Keyword(s):  
Middle Atmosphere ◽  
Spectral Feature ◽  
Wave Model ◽  
Diurnal Tide ◽  
Wave Number ◽  
Semidiurnal Tide ◽  
Data Set ◽  
Wave Numbers ◽  
Nonmigrating Tides ◽  
Longitudinal Structures

Abstract. HRDI (High Resolution Doppler Interferometer-UARS) winds data have been analyzed in 4°-latitude by 10°-longitude cells at 96km to obtain the global distribution of the solar-tidal amplitudes and phases. The solstices June–July (1993), December–January (1993–1994), and one equinox (September–October, 1994) are analyzed. In an earlier paper (Manson et al., 2002b) the emphasis was solely upon the longitudinal and latitudinal variations of the amplitudes and phases of the semidiurnal (12h) and diurnal (24h) tides. The longitudinal structures were shown to be quite distinctive, and in the case of the EW component of the diurnal tide there were typically four maxima/perturbations of amplitudes or phases around a latitude circle. In this case they tended to be associated with the locations of the major oceans. Here, a spatial complex spectral analysis has been applied to the data set, to obtain the zonal wave numbers for the tides as functions of latitude. For the diurnal tide the dominant s=1 migrating component and nonmigrating tides with wave numbers s=–3, –2, 0, 2 are identified; and for the semidiurnal tide, as well as the dominant s=2 migrating component, the spectra indicate the presence of nonmigrating tides with wave numbers s=–2, 0, 4. These wave numbers are also simply related to the global longitudinal structures in the tidal amplitudes and phases. Comparisons are made with the Global Scale Wave Model (GSWM-02), which now incorporates migrating and nonmigrating tides associated with tropospheric latent heat processes, and offers monthly outputs. For the diurnal tide the dominant nonmigrating tidal spectral feature (94km) is for wave number s=–3; it is relatively stronger than in the HRDI winds, and produces quite consistent structures in the global tidal fields with four longitudinal maxima. Overall, the modelled 24-h tidal amplitudes are larger than observed during the equinox beyond 40° latitude. For the semidiurnal tide, nonmigrating tides are frequently indicated in the spectra with wave numbers s=–2, 0, 6; and there are complementary longitudinal structures in the global tidal fields with two and four maxima evident. Modelled 12-h tidal amplitudes are much smaller than observed during non-winter months beyond 30°. There is a detailed discussion of the spectral features, their seasonal variations, and the similarities with the HRDI tidal data. This discussion is in the context of the inherent limitations of the model.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; waves and tides)

scholarly journals Volcanic forcing for climate modeling: a new microphysics-based data set covering years 1600–present

2014 ◽  
Vol 10 (1) ◽  
pp. 359-375 ◽  
Author(s):  
F. Arfeuille ◽  
D. Weisenstein ◽  
H. Mack ◽  
E. Rozanov ◽  
T. Peter ◽  
...  
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Circulation Model ◽  
Ice Cores ◽  
Volcanic Eruptions ◽  
Global Scale ◽  
Stratospheric Aerosol ◽  
Set Covering ◽  
Data Set ◽  
Volcanic Forcing

Abstract. As the understanding and representation of the impacts of volcanic eruptions on climate have improved in the last decades, uncertainties in the stratospheric aerosol forcing from large eruptions are now linked not only to visible optical depth estimates on a global scale but also to details on the size, latitude and altitude distributions of the stratospheric aerosols. Based on our understanding of these uncertainties, we propose a new model-based approach to generating a volcanic forcing for general circulation model (GCM) and chemistry–climate model (CCM) simulations. This new volcanic forcing, covering the 1600–present period, uses an aerosol microphysical model to provide a realistic, physically consistent treatment of the stratospheric sulfate aerosols. Twenty-six eruptions were modeled individually using the latest available ice cores aerosol mass estimates and historical data on the latitude and date of eruptions. The evolution of aerosol spatial and size distribution after the sulfur dioxide discharge are hence characterized for each volcanic eruption. Large variations are seen in hemispheric partitioning and size distributions in relation to location/date of eruptions and injected SO2 masses. Results for recent eruptions show reasonable agreement with observations. By providing these new estimates of spatial distributions of shortwave and long-wave radiative perturbations, this volcanic forcing may help to better constrain the climate model responses to volcanic eruptions in the 1600–present period. The final data set consists of 3-D values (with constant longitude) of spectrally resolved extinction coefficients, single scattering albedos and asymmetry factors calculated for different wavelength bands upon request. Surface area densities for heterogeneous chemistry are also provided.

scholarly journals Methyl iodide production in the open ocean

2013 ◽  
Vol 10 (11) ◽  
pp. 17549-17595 ◽  
Author(s):  
I. Stemmler ◽  
I. Hense ◽  
B. Quack ◽  
E. Maier-Reimer
Keyword(s):  
Methyl Iodide ◽  
General Circulation ◽  
Three Dimensional ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Global Scale ◽  
Phytoplankton Production ◽  
Boreal Winter ◽  
Photochemical Degradation ◽  
Data Set

Abstract. Production pathways of the prominent volatile organic halogen compound methyl iodide (CH3I) are not fully understood. Previous model studies suggest either production via photochemical degradation of organic material or rather phytoplankton production. Correlations between biological and environmental variables derived from observations also suggest both production pathways. In this study we aim to address this question of source mechanisms with a global three-dimensional ocean general circulation model including biogeochemistry (MPIOM-HAMOCC) by carrying out a series of sensitivity experiments. Simulated distribution patterns and emissions of CH3I differ largely for the different production pathways. However, the evaluation of our model results with observations from a newly available global data set shows that observed surface concentrations of CH3I can be best explained by the photochemical production pathway. Our results further emphasize that correlations between CH3I and abiotic or biotic factors do not necessarily provide meaningful insights concerning the source of origin. Overall, we find a net global annual CH3I air–sea flux that ranges between 70 and 260 Gg yr−1. Hence, at the global scale the ocean is a net source of methyl iodide for the atmosphere, though in some regions in boreal winter fluxes are of opposite direction (from the atmosphere to the ocean).

scholarly journals The 16-day planetary waves: multi-MF radar observations from the arctic to equator and comparisons with the HRDI measurements and the GSWM modelling results

2002 ◽  
Vol 20 (5) ◽  
pp. 691-709 ◽  
Author(s):  
Y. Luo ◽  
A. H. Manson ◽  
C. E. Meek ◽  
C. K. Meyer ◽  
M. D. Burrage ◽  
...  
Keyword(s):  
Middle Atmosphere ◽  
Wave Model ◽  
Global Scale ◽  
The Arctic ◽  
Planetary Scale ◽  
Christmas Island ◽  
Wind Measurements ◽  
Strong Amplitude ◽  
Waves And Tides ◽  
Thermospheric Dynamics

Abstract. The mesospheric and lower thermospheric (MLT) winds (60–100 km) obtained by multiple MF radars, located from the arctic to equator at Tromsø (70° N, 19° E), Saskatoon (52° N, 107° W), London (43° N, 81° W), Hawaii (21° N, 157° W) and Christmas Island (2° N, 157° W), respectively, are used to study the planetary-scale 16-day waves. Based on the simultaneous observations (1993/1994), the variabilities of the wave amplitudes, periods and phases are derived. At mid- and high-latitude locations the 16-day waves are usually pervasive in the winter-centred seasons (October through March), with the amplitude gradually decreasing with height. From the subtropical location to the equator, the summer wave activities become strong at some particular altitude where the inter-hemisphere wave ducts possibly allow for the leakage of the wave from the other hemispheric winter. The observational results are in good agreement with the theoretical conclusion that, for slowly westward-traveling waves, such as the 16-day wave, vertical propagation is permitted only in an eastward background flow of moderate speed which is present in the winter hemisphere. The wave period also varies with height and time in a range of about 12–24 days. The wave latitudinal differences and the vertical structures are compared with the Global Scale Wave Model (GSWM) for the winter situation. Although their amplitude variations and profiles have a similar tendency, the discrepancies are considerable. For example, the maximum zonal amplitude occurs around 40° N for radar but 30° N for the model. The phase differences between sites due to the latitudinal effect are basically consistent with the model prediction of equatorward phase-propagation. The global 16-day waves at 95 km from the HRDI wind measurements during 1992 through 1995 are also displayed. Again, the wave is a winter dominant phenomenon with strong amplitude around the 40–60° latitude-band on both hemispheres.Key words. Meteorology and atmospheric dynamics – waves and tides – middle atmosphere dynamics – thermospheric dynamics

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