scholarly journals Evaluation of coastal Antarctic precipitation in MAR3.9 regional and LMDz6 global atmospheric model with ground-based radar observations

2020 ◽  
Author(s):  
Florentin Lemonnier ◽  
Alizée Chemison ◽  
Hubert Gallée ◽  
Gerhard Krinner ◽  
Jean-Baptiste Madeleine ◽  
...  
Keyword(s):  
General Circulation ◽  
Climate Modeling ◽  
Circulation Model ◽  
Atmospheric Model ◽  
Sensitivity Study ◽  
Scale Model ◽  
Polar Regions ◽  
Global Atmospheric Model ◽  
Precipitation Simulation ◽  
Antarctic Precipitation

Abstract. In the current context of climate change in the poles, one of the objectives of the APRES3 (Antarctic Precipitation Remote Sensing from Surface and Space) project is to characterize the vertical structure of precipitation in order to better simulate it. Nowadays, the precipitation simulated by models in Antarctica is very widespread and overestimated the data. Sensitivity studies have been conducted using two models and compared to the observations obtained at the Dumont d'Urville coast station, obtained by a Micro Rain Radar (MRR). The MAR meso-scale model specifically developed for the polar regions and the LMDz/IPSL general circulation model, with zoomed configuration over Dumont d'Urville, have been considered for this study. These models being different in resolution and physical configuration, performing an inter-comparison required numerical, dynamic and physical adjustments in LMDz. A sensitivity study was conducted on the physical and numerical parameters of the LMDz model and on the resolution of the MAR with the aim of estimating their contribution to the precipitation simulation. Sensitivity tests with MAR revealed that this model is well adjusted for precipitation modeling in polar climates, this confirming that this model is a reference in polar climate modeling. Regarding LMDz, sensitivity experiments revealed that modifications in the sedimentation and sublimation parameters do not significantly impact precipitation rate. However, dissipation of the LMDz model, which is a numerical process that dissipates spatially excessive energy and keeps the model stable, impacts precipitation indirectly but very strongly. A suitable adjustment of the dissipation reduces significantly precipitation over Antarctic peripheral area, thus providing a simulated profile in better agreement with the MRR observations.

scholarly journals Evaluation of coastal Antarctic precipitation in LMDz6 global atmospheric model using ground-based radar observations

2021 ◽  
Vol 67 (2) ◽  
pp. 147-164
Author(s):  
F. Lemonnier ◽  
A. Chemison ◽  
G. Krinner ◽  
J.-B. Madeleine ◽  
C. Claud ◽  
...  
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Circulation Model ◽  
Atmospheric Model ◽  
Sensitivity Study ◽  
Global Atmospheric Model ◽  
Precipitation Simulation ◽  
Antarctic Precipitation

In the current context of climate change in the poles, one of the objectives of the APRES3 (Antarctic Precipitation Remote Sensing from Surface and Space) project was to characterize the vertical structure of precipitation in order to better simulate it. Precipitation simulated by models in Antarctica is currently very widespread and it overestimates the data. Sensitivity studies have been conducted using a global climate model and compared to the observations obtained at the Dumont d’Urville coast station, obtained by a Micro Rain Radar (MRR). The LMDz/IPSL general circulation model, with zoomed configuration over Dumont d’Urville, has been considered for this study. A sensitivity study was conducted on the physical and numerical parameters of the LMDz model with the aim of estimating their contribution to the precipitation simulation. Sensitivity experiments revealed that changes in the sedimentation and sublimation parameters do not significantly impact precipitation rate. However, dissipation of the LMDz model, which is a numerical process that dissipates spatially excessive energy and keeps the model stable, impacts precipitation indirectly but very strongly. A suitable adjustment of the dissipation reduces significantly precipitation over Antarctic peripheral area, thus providing a simulated profile in better agreement with the MRR observations.

scholarly journals Magnetic perturbations seen by CHAMP and evaluated using the TIE-GCM

2007 ◽  
Vol 25 (7) ◽  
pp. 1543-1554
Author(s):  
D. T. Mozzoni ◽  
M. Mandea ◽  
J. Cain
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
Temporal Correlation ◽  
Atmospheric Model ◽  
Initial Study ◽  
Vector Data ◽  
Magnetic Vector ◽  
Global Atmospheric Model ◽  
Magnetic Perturbations ◽  
Current Systems

Abstract. The Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIE-GCM) is a self-consistent, global, atmospheric model that can be used to estimate magnetic perturbations at satellite altitude. These computed perturbations can then be compared with the magnetic vector data provided by low-earth orbiting satellites. In this initial study, the quietest day of each month from 2001–2005 was selected for comparison. CHAMP magnetic vector residuals were computed for these intervals using the CHAOS model to remove core and crustal geomagnetic contributions. Under various input parameters, the TIE-GCM predictions were compared with the CHAMP residuals on an orbit by orbit basis. Initial results demonstrate a reasonable agreement between the TIE-GCM estimates and the CHAMP residuals in non-polar, dayside regions (±50° magnetic latitude) where both are able to resolve the Equatorial Electro-Jet (EEJ) and solar quiet (Sq) current systems. Although no clear component or temporal correlation was discerned, evidence showing the decrease in residual comparisons presents the possibility of using the TIE-GCM to pre-process geomagnetic data for main field modeling purposes.

scholarly journals Global Atmospheric Model Simulates Fine Details of Gravity Waves

Eos ◽  
2015 ◽  
Vol 96 ◽  
Author(s):  
Puneet Kollipara
Keyword(s):  
Gravity Wave ◽  
General Circulation Model ◽  
Gravity Waves ◽  
General Circulation ◽  
Circulation Model ◽  
Atmospheric Model ◽  
Global Atmospheric Model ◽  
Atmosphere General Circulation Model

Whole-atmosphere general circulation model captures many aspects of mesoscale gravity wave structures—down to the tens of kilometers—and resulting temperatures and tides.

Future Change of Western North Pacific Typhoons: Projections by a 20-km-Mesh Global Atmospheric Model*

2011 ◽  
Vol 24 (4) ◽  
pp. 1154-1169 ◽  
Author(s):  
Hiroyuki Murakami ◽  
Bin Wang ◽  
Akio Kitoh
Keyword(s):  
North Pacific ◽  
General Circulation ◽  
Western North Pacific ◽  
Large Scale ◽  
Vertical Wind Shear ◽  
Circulation Model ◽  
Atmospheric Model ◽  
Japan Meteorological Agency ◽  
Global Atmospheric Model ◽  
Meteorological Research Institute

Abstract Projected future changes in tropical cyclone (TC) activity over the western North Pacific (WNP) under the Special Report on Emissions Scenarios (SRES) A1B emission scenario were investigated using a 20-km-mesh, very-high-resolution Meteorological Research Institute (MRI)–Japan Meteorological Agency (JMA) atmospheric general circulation model. The present-day (1979–2003) simulation yielded reasonably realistic climatology and interannual variability for TC genesis frequency and tracks. The future (2075–99) projection indicates (i) a significant reduction (by about 23%) in both TC genesis number and frequency of occurrence primarily during the late part of the year (September–December), (ii) an eastward shift in the positions of the two prevailing northward-recurving TC tracks during the peak TC season (July–October), and (iii) a significant reduction (by 44%) in TC frequency approaching coastal regions of Southeast Asia. The changes in occurrence frequency are due in part to changes in large-scale steering flows, but they are due mainly to changes in the locations of TC genesis; fewer TCs will form in the western portion of the WNP (west of 145°E), whereas more storms will form in the southeastern quadrant of the WNP (10°–20°N, 145°–160°E). Analysis of the genesis potential index reveals that the reduced TC genesis in the western WNP is due mainly to in situ weakening of large-scale ascent and decreasing midtropospheric relative humidity, which are associated with the enhanced descent of the tropical overturning circulation. The analysis also indicates that enhanced TC genesis in the southeastern WNP is due to increased low-level cyclonic vorticity and reduced vertical wind shear. These changes appear to be critically dependent on the spatial pattern of future sea surface temperature; therefore, it is necessary to conduct ensemble projections with a range of SST spatial patterns to understand the degree and distribution of uncertainty in future projections.

scholarly journals The GCM Response to Current Parameterizations of Nonorographic Gravity Wave Drag

2005 ◽  
Vol 62 (7) ◽  
pp. 2394-2413 ◽  
Author(s):  
Charles McLandress ◽  
John F. Scinocca
Keyword(s):  
Gravity Wave ◽  
General Circulation ◽  
Critical Level ◽  
Climate Modeling ◽  
Circulation Model ◽  
Wave Drag ◽  
Nonlinear Dissipation ◽  
Additional Experiment ◽  
Identical Response ◽  
Dissipation Mechanism

Abstract A comparison is undertaken of the response of a general circulation model (GCM) to the nonorographic gravity wave drag parameterizations of Hines, Warner and McIntyre, and Alexander and Dunkerton. The analysis is restricted to a comparison of each parameterization’s nonlinear dissipation mechanism since, in principle, this is the only component that differs between the schemes. This is achieved by developing a new, more general parameterization that can represent each of these dissipation mechanisms, while keeping all other aspects of the problem identical. The GCM simulations reveal differences in the climatological response to the three dissipation mechanisms. These differences are documented for both tropopause and surface launch elevations of the parameterized waves. The simulations also reveal systematic differences in the height at which momentum is deposited. This behavior is investigated further in a set of experiments designed to reduce these systematic differences, while leaving the details of the dissipation mechanisms unaltered. These sensitivity experiments demonstrate that it is possible to obtain nearly identical responses from all three mechanisms, which indicates that the GCM response is largely insensitive to the precise details of the dissipation mechanisms. This finding is supported by an additional experiment in which the nonlinear dissipation mechanisms are turned off and critical-level filtering is left to act as the only source of dissipation. In this experiment, critical-level filtering effectively replaces the nonlinear dissipation mechanism, producing a nearly identical response. The results of this study suggest that climate modeling efforts would potentially benefit more from the refinement of other aspects of the parameterization problem, such as the properties of the launch spectrum, than they have benefited from the refinement of dissipation mechanisms.

Interannual oscillations in an ocean general circulation model coupled to a simple atmosphere model

1989 ◽  
Vol 329 (1604) ◽  
pp. 189-205 ◽  
Keyword(s):  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
Circulation Model ◽  
Coupled System ◽  
General Circulation Models ◽  
Atmospheric Model ◽  
Ocean General Circulation Model ◽  
Coupled Oscillations

A model is being developed for tropical air-sea interaction studies that is intermediate in complexity between the large coupled general circulation models (GCMS) that are coming into use, and the simple two-level models with which pioneering El Nino Southern Oscillation studies were done. The model consists of a stripped-down tropical Pacific Ocean GCM, coupled to an atmospheric model that is sufficiently simple that steady-state solutions may be found for low-level flow and surface stress, given oceanic boundary conditions. This permits examination of the nature of interannual coupled oscillations in the absence of atmospheric noise. In preliminary tests of the model the coupled system is found to undergo a Hopf bifurcation as certain parameters are varied, giving rise to sustained three to four year oscillations. For stronger coupling, a secondary bifurcation yields six month coupled oscillations during the warm phase of the El Nino-period oscillation. Such variability could potentially affect the predictability of the coupled system.

scholarly journals Modelling the wintertime response to upper tropospheric and lower stratospheric ozone anomalies over the North Atlantic and Europe

2003 ◽  
Vol 21 (10) ◽  
pp. 2107-2118 ◽  
Author(s):  
I. Kirchner ◽  
D. Peters
Keyword(s):  
North Atlantic ◽  
General Circulation ◽  
Initial Conditions ◽  
Stratospheric Ozone ◽  
Circulation Model ◽  
Sensitivity Study ◽  
Boreal Winter ◽  
Radiative Processes ◽  
The North ◽  
The North Atlantic

Abstract. During boreal winter months, mean longitude-dependent ozone changes in the upper troposphere and lower stratosphere are mainly caused by different ozone transport by planetary waves. The response to radiative perturbation induced by these ozone changes near the tropopause on the circulation is unclear. This response is investigated with the ECHAM4 general circulation model in a sensitivity study. In the simulation two different mean January realizations of the ozone field are implemented in ECHAM4. Both ozone fields are estimated on the basis of the observed mean January planetary wave structure of the 1980s. The first field represents a 14-year average (reference, 1979–1992) and the second one represents the mean ozone field change (anomaly, 1988–92) in boreal extra-tropics during the end of the 1980s. The model runs were carried out pairwise, with identical initial conditions for both ozone fields. Five statistically independent experiments were performed, forced with the observed sea surface temperatures for the period 1988 to 1992. The results support the hypothesis that the zonally asymmetric ozone changes of the 80s triggered a systematic alteration of the circulation over the North Atlantic – European region. It is suggested that this feedback process is important for the understanding of the decadal coupling between troposphere and stratosphere, as well as between subtropics and extra-tropics in winter.Key words. Meteorology and atmospheric dynamics (general circulation; radiative processes; synoptic-scale meteorology)

scholarly journals Climatic stability of the geographic origin of Antarctic precipitation simulated by an atmospheric general circulation model

1999 ◽  
Vol 29 ◽  
pp. 45-48 ◽  
Author(s):  
Gilles Delaygue ◽  
Valérie Masson ◽  
Jean Jouzel
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Latitudinal Gradient ◽  
Atmospheric General Circulation Model ◽  
Hydrological Cycle ◽  
Geographic Origin ◽  
Circulation Model ◽  
Sea Surface ◽  
Atmospheric General Circulation ◽  
Antarctic Precipitation

AbstractThe geographic origin of Antarctic precipitation is important for ice-core isotopic interpretation as well as ice-sheet mass-balance calculations. Here we estimate these moisture origins with the NASA/Goddard Institute of Space Studies atmospheric general circulation model, under different climatic conditions. This model reasonably simulates the broad features of the present-day observed hydrological cycle, and indicates a subtropical to subglacial (30-60° S) latitudinal origin for the Antarctic precipitation. We use different climatic reconstructions, all based on CLIMAP, for the Last Glacial Maximum (about 21000 years ago), which differ by the latitudinal sea-surface temperature gradient and seasonality. CLIMAP conditions increase the latitudinal gradient and the sea-ice extent, with the consequence of slightly enhancing the low-latitude origins. Shifting the seasonal cycle of oceanic prescribed conditions has an important effect on the hydrological cycle but less on the precipitation origin. Prescribing cooler tropical sea-surface temperatures, which decreases the latitudinal gradient, makes the latitudinal contributions closer to modern ones and increases the dominant oceanic sources. Globally the origins of Antarctic precipitation do not change significantly, either annually or seasonally.

scholarly journals DMS atmospheric concentrations and sulphate aerosol indirect radiative forcing: a sensitivity study to the DMS source representation and oxidation

2003 ◽  
Vol 3 (1) ◽  
pp. 49-65 ◽  
Author(s):  
O. Boucher ◽  
C. Moulin ◽  
S. Belviso ◽  
O. Aumont ◽  
L. Bopp ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
General Circulation ◽  
Marine Boundary Layer ◽  
Circulation Model ◽  
Sensitivity Study ◽  
Sulphate Aerosol ◽  
Sulphate Aerosols ◽  
The Impact ◽  
Atmospheric Concentrations ◽  
Indirect Radiative Forcing

Abstract. The global sulphur cycle has been simulated using a general circulation model with a focus on the source and oxidation of atmospheric dimethylsulphide (DMS). The sensitivity of atmospheric DMS to the oceanic DMS climatology, the parameterisation of the sea-air transfer and to the oxidant fields have been studied. The importance of additional oxidation pathways (by O3 in the gas- and aqueous-phases and by BrO in the gas phase) not incorporated in global models has also been evaluated. While three different climatologies of the oceanic DMS concentration produce rather similar global DMS fluxes to the atmosphere at 24-27 Tg S yr -1, there are large differences in the spatial and seasonal distribution. The relative contributions of OH and NO3 radicals to DMS oxidation depends critically on which oxidant fields are prescribed in the model. Oxidation by O3 appears to be significant at high latitudes in both hemispheres. Oxidation by BrO could be significant even for BrO concentrations at sub-pptv levels in the marine boundary layer. The impact of such refinements on the DMS chemistry onto the indirect radiative forcing by anthropogenic sulphate aerosols is also discussed.

Sensitivity of the Aerosol Indirect Effect to Subgrid Variability in the Cloud Parameterization of the GFDL Atmosphere General Circulation Model AM3

2011 ◽  
Vol 24 (13) ◽  
pp. 3145-3160 ◽  
Author(s):  
Jean-Christophe Golaz ◽  
Marc Salzmann ◽  
Leo J. Donner ◽  
Larry W. Horowitz ◽  
Yi Ming ◽  
...  
Keyword(s):  
General Circulation Model ◽  
Indirect Effect ◽  
General Circulation ◽  
Coupled Model ◽  
Circulation Model ◽  
Atmospheric Model ◽  
Radiation Balance ◽  
Cloud Drop ◽  
Aerosol Indirect Effect ◽  
Alternate Model

Abstract The recently developed GFDL Atmospheric Model version 3 (AM3), an atmospheric general circulation model (GCM), incorporates a prognostic treatment of cloud drop number to simulate the aerosol indirect effect. Since cloud drop activation depends on cloud-scale vertical velocities, which are not reproduced in present-day GCMs, additional assumptions on the subgrid variability are required to implement a local activation parameterization into a GCM. This paper describes the subgrid activation assumptions in AM3 and explores sensitivities by constructing alternate configurations. These alternate model configurations exhibit only small differences in their present-day climatology. However, the total anthropogenic radiative flux perturbation (RFP) between present-day and preindustrial conditions varies by ±50% from the reference, because of a large difference in the magnitude of the aerosol indirect effect. The spread in RFP does not originate directly from the subgrid assumptions but indirectly through the cloud retuning necessary to maintain a realistic radiation balance. In particular, the paper shows a linear correlation between the choice of autoconversion threshold radius and the RFP. Climate sensitivity changes only minimally between the reference and alternate configurations. If implemented in a fully coupled model, these alternate configurations would therefore likely produce substantially different warming from preindustrial to present day.

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