scholarly journals An efficient multi-resolution grid for global models and coupled systems

2019 ◽  
Vol 16 ◽  
pp. 137-142 ◽  
Author(s):  
Jian-Guo Li
Keyword(s):  
Coupled Systems ◽  
Global Coordinate System ◽  
High Latitudes ◽  
Global Models ◽  
Quad Tree ◽  
Fixed Reference ◽  
Multiple Cell ◽  
Wave Models ◽  
Ocean Surface Wave ◽  
Polar Singularity

Abstract. The latitude-longitude (lat-lon) grid is the most widely used global coordinate system for various purposes but its singularity at the Pole and the vector polar problems associated with its converging meridians hinder its applications. Well from the very start of numerical modelling history, quite a few grids have been attempted to tackle these problems and reduced grid is the simplest one among other grids. However, the reduced grid is almost abandoned by modern numerical modellers due to its unsatisfactory results for dynamical models in the polar region. Spherical multiple-cell (SMC) grid is similar to the reduced grid apparently but uses the unstructured technique for efficiency. It merges longitudinal cells at high latitudes like the reduced grid to overcome the CFL restriction and introduces a polar cell to remove the polar singularity. It also supports quad-tree-like mesh refinement to form a multi-resolution grid. To tackle the vector polar problem associated with the increased curvature at high latitudes, the SMC grid uses a new fixed reference direction to define vector components near the poles for improved polar performance. Global transportation is quite efficient on the SMC grid with optional second or third order transportation scheme. Present applications of the SMC grid, particularly in ocean surface wave models, are presented and possible future usage in global models and coupled systems are proposed.

scholarly journals Global Transport on a Spherical Multiple-Cell Grid

2011 ◽  
Vol 139 (5) ◽  
pp. 1536-1555 ◽  
Author(s):  
Jian-Guo Li
Keyword(s):  
Ocean Surface ◽  
The Arctic ◽  
Global Ocean ◽  
Time Step ◽  
Spherical Coordinate ◽  
Advection Schemes ◽  
Global Transport ◽  
Multiple Cell ◽  
Wave Models ◽  
Polar Singularity

Second- and third-order upstream nonoscillatory (UNO) advection schemes are applied on a spherical multiple-cell (SMC) grid for global transport. Similar to the reduced grid, the SMC grid relaxes the Courant–Friedrichs–Lewy (CFL) restriction of the Eulerian advection time step on the conventional latitude–longitude grid by zonally merging cells toward the poles. Round polar cells are introduced to remove the polar singularity of the spherical coordinate system. The unstructured feature of the SMC grid allows unused cells to be removed out of memory and transport calculations. Solid-body rotation and deformation flow tests are used for comparison with other transport schemes. Application on the global ocean surface is used to demonstrate the flexibility of the SMC grid by removing all land points and making possible the extension of global ocean surface wave models to cover the Arctic in response to the retreating sea ice in recent summers. Numerical results suggest that UNO schemes on the SMC grid are suitable for global transport.

scholarly journals Tropopause fold occurrence rates over the Antarctic station Troll (72° S, 2.5° E)

2013 ◽  
Vol 31 (4) ◽  
pp. 591-598 ◽  
Author(s):  
M. Mihalikova ◽  
S. Kirkwood
Keyword(s):  
Weather Forecasting ◽  
Radar Data ◽  
Occurrence Rate ◽  
High Latitudes ◽  
Global Models ◽  
Model Studies ◽  
Direct Measurements ◽  
Wind Profiler Radar ◽  
Summer Minimum ◽  
The Antarctic

Abstract. One of the important mechanisms of stratosphere–troposphere exchange, which brings ozone-rich stratospheric air to low altitudes in extratropical regions, is transport related to tropopause folds. The climatology of folds has been studied at high latitudes of the Northern Hemisphere with the help of radars and global models. Global models supply information about fold occurrence rates at high latitudes of the Southern Hemisphere as well, but so far comparisons with direct measurements are rare. The Moveable Atmospheric Radar for Antarctica (MARA), a 54.5 MHz wind-profiler radar, has been operated at the Norwegian year-round station Troll, Antarctica (72° S, 2.5° E) since December 2011. Frequent tropopause fold signatures have been observed. In this study, based on MARA observations, an occurrence rate statistics of tropopause folds from December 2011 until November 2012 has been made, and radar data have been compared with the analysis from the European Center for Medium-Range Weather Forecasting (ECMWF). The fold occurrence rates exhibit an annual cycle with winter maximum and summer minimum and suggest significantly higher occurrence rates for the given location than those obtained previously by global model studies.

scholarly journals Using beryllium-7 to assess cross-tropopause transport in global models

2016 ◽  
Vol 16 (7) ◽  
pp. 4641-4659 ◽  
Author(s):  
Hongyu Liu ◽  
David B. Considine ◽  
Larry W. Horowitz ◽  
James H. Crawford ◽  
Jose M. Rodriguez ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Transport Model ◽  
Meteorological Data ◽  
Data Sets ◽  
High Latitudes ◽  
Chemical Transport Model ◽  
Modeling Framework ◽  
Global Models ◽  
Deposition Fluxes ◽  
Upper Troposphere

Abstract. We use the Global Modeling Initiative (GMI) modeling framework to assess the utility of cosmogenic beryllium-7 (7Be), a natural aerosol tracer, for evaluating cross-tropopause transport in global models. The GMI chemical transport model (CTM) was used to simulate atmospheric 7Be distributions using four different meteorological data sets (GEOS1-STRAT DAS, GISS II′ GCM, fvGCM, and GEOS4-DAS), featuring significantly different stratosphere–troposphere exchange (STE) characteristics. The simulations were compared with the upper troposphere and/or lower stratosphere (UT/LS) 7Be climatology constructed from  ∼  25 years of aircraft and balloon data, as well as climatological records of surface concentrations and deposition fluxes. Comparison of the fraction of surface air of stratospheric origin estimated from the 7Be simulations with observationally derived estimates indicates excessive cross-tropopause transport at mid-latitudes in simulations using GEOS1-STRAT and at high latitudes using GISS II′ meteorological data. These simulations also overestimate 7Be deposition fluxes at mid-latitudes (GEOS1-STRAT) and at high latitudes (GISS II′), respectively. We show that excessive cross-tropopause transport of 7Be corresponds to overestimated stratospheric contribution to tropospheric ozone. Our perspectives on STE in these meteorological fields based on 7Be simulations are consistent with previous modeling studies of tropospheric ozone using the same meteorological fields. We conclude that the observational constraints for 7Be and observed 7Be total deposition fluxes can be used routinely as a first-order assessment of cross-tropopause transport in global models.

scholarly journals The seamless and multi-model coupling between atmosphere, land, hydrology, ocean, waves and sea-ice models based on SURFEX surface model using OASIS3-MCT

2017 ◽  
Author(s):  
Aurore Voldoire ◽  
Bertrand Decharme ◽  
Joris Pianezze ◽  
Cindy Lebeaupin Brossier ◽  
Florence Sevault ◽  
...  
Keyword(s):  
Weather Prediction ◽  
Ocean Waves ◽  
Coupled Systems ◽  
Surface Model ◽  
Atmospheric Models ◽  
Common Structure ◽  
Wide Range ◽  
Wave Models ◽  
Prediction Systems ◽  
Component Models

Abstract. This study presents the principles of the new coupling interface based on the SURFEX multi-surface model and the OASIS3-MCT coupler. As SURFEX can be plugged into several atmospheric models, it can be used in a wide range of applications, from global and regional coupled climate systems to high-resolution Numerical Weather Prediction systems or very fine scale systems dedicated to process studies. The objective of this development is to build and share a common structure for all these applications for the atmosphere-surface coupling, between atmospheric models and ocean, ice, hydrology, and wave models. The numerical and physical principles of the SURFEX interface between the different component models are described, and the different coupled systems into which the SURFEX OASIS3-MCT-based coupling interface is already applied are presented.

scholarly journals SURFEX v8.0 interface with OASIS3-MCT to couple atmosphere with hydrology, ocean, waves and sea-ice models, from coastal to global scales

2017 ◽  
Vol 10 (11) ◽  
pp. 4207-4227 ◽  
Author(s):  
Aurore Voldoire ◽  
Bertrand Decharme ◽  
Joris Pianezze ◽  
Cindy Lebeaupin Brossier ◽  
Florence Sevault ◽  
...  
Keyword(s):  
Weather Prediction ◽  
Ocean Waves ◽  
Coupled Systems ◽  
Surface Model ◽  
Atmospheric Models ◽  
Common Structure ◽  
Wide Range ◽  
Wave Models ◽  
Prediction Systems ◽  
The One

Abstract. This study presents the principles of the new coupling interface based on the SURFEX multi-surface model and the OASIS3-MCT coupler. As SURFEX can be plugged into several atmospheric models, it can be used in a wide range of applications, from global and regional coupled climate systems to high-resolution numerical weather prediction systems or very fine-scale models dedicated to process studies. The objective of this development is to build and share a common structure for the atmosphere–surface coupling of all these applications, involving on the one hand atmospheric models and on the other hand ocean, ice, hydrology, and wave models. The numerical and physical principles of SURFEX interface between the different component models are described, and the different coupled systems in which the SURFEX OASIS3-MCT-based coupling interface is already implemented are presented.

scholarly journals Characterization of organic aerosol across the global remote troposphere: a comparison of ATom measurements and global chemistry models

2020 ◽  
Vol 20 (8) ◽  
pp. 4607-4635 ◽  
Author(s):  
Alma Hodzic ◽  
Pedro Campuzano-Jost ◽  
Huisheng Bian ◽  
Mian Chin ◽  
Peter R. Colarco ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Current Model ◽  
Lower Troposphere ◽  
Organic Aerosol ◽  
High Latitudes ◽  
Free Troposphere ◽  
Model Ensemble ◽  
Global Models ◽  
Remote Troposphere

Abstract. The spatial distribution and properties of submicron organic aerosol (OA) are among the key sources of uncertainty in our understanding of aerosol effects on climate. Uncertainties are particularly large over remote regions of the free troposphere and Southern Ocean, where very few data have been available and where OA predictions from AeroCom Phase II global models span 2 to 3 orders of magnitude, greatly exceeding the model spread over source regions. The (nearly) pole-to-pole vertical distribution of non-refractory aerosols was measured with an aerosol mass spectrometer onboard the NASA DC-8 aircraft as part of the Atmospheric Tomography (ATom) mission during the Northern Hemisphere summer (August 2016) and winter (February 2017). This study presents the first extensive characterization of OA mass concentrations and their level of oxidation in the remote atmosphere. OA and sulfate are the major contributors by mass to submicron aerosols in the remote troposphere, together with sea salt in the marine boundary layer. Sulfate was dominant in the lower stratosphere. OA concentrations have a strong seasonal and zonal variability, with the highest levels measured in the lower troposphere in the summer and over the regions influenced by biomass burning from Africa (up to 10 µg sm−3). Lower concentrations (∼0.1–0.3 µg sm−3) are observed in the northern middle and high latitudes and very low concentrations (<0.1 µg sm−3) in the southern middle and high latitudes. The ATom dataset is used to evaluate predictions of eight current global chemistry models that implement a variety of commonly used representations of OA sources and chemistry, as well as of the AeroCom-II ensemble. The current model ensemble captures the average vertical and spatial distribution of measured OA concentrations, and the spread of the individual models remains within a factor of 5. These results are significantly improved over the AeroCom-II model ensemble, which shows large overestimations over these regions. However, some of the improved agreement with observations occurs for the wrong reasons, as models have the tendency to greatly overestimate the primary OA fraction and underestimate the secondary fraction. Measured OA in the remote free troposphere is highly oxygenated, with organic aerosol to organic carbon (OA ∕ OC) ratios of ∼2.2–2.8, and is 30 %–60 % more oxygenated than in current models, which can lead to significant errors in OA concentrations. The model–measurement comparisons presented here support the concept of a more dynamic OA system as proposed by Hodzic et al. (2016), with enhanced removal of primary OA and a stronger production of secondary OA in global models needed to provide better agreement with observations.

scholarly journals Using beryllium-7 to assess cross-tropopause transport in global models

2015 ◽  
Vol 15 (18) ◽  
pp. 26131-26189 ◽  
Author(s):  
H. Liu ◽  
D. B. Considine ◽  
L. W. Horowitz ◽  
J. H. Crawford ◽  
J. M. Rodriguez ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Transport Model ◽  
Meteorological Data ◽  
Observational Constraints ◽  
High Latitudes ◽  
Chemical Transport Model ◽  
Modeling Framework ◽  
Global Models ◽  
Deposition Fluxes ◽  
Middle Latitudes

Abstract. We use the Global Modeling Initiative (GMI) modeling framework to assess the utility of cosmogenic beryllium-7 (7Be), a natural aerosol tracer, for evaluating cross-tropopause transport in global models. The GMI chemical transport model (CTM) was used to simulate atmospheric 7Be distributions using four different meteorological data sets (GEOS1-STRAT DAS, GISS II' GCM, fvGCM, and GEOS4-DAS), featuring significantly different stratosphere–troposphere exchange (STE) characteristics. The simulations were compared with the upper troposphere/lower stratosphere (UT/LS) 7Be climatology constructed from ~ 25 years of aircraft and balloon data, as well as climatological records of surface concentrations and deposition fluxes. Comparison of the fraction of surface air of stratospheric origin estimated from the 7Be simulations with observationally-derived estimates indicates excessive cross-tropopause transport at middle latitudes in simulations using GEOS1-STRAT and at high latitudes using GISS II' meteorological data. These simulations also overestimate 7Be deposition fluxes at middle latitudes (GEOS1-STRAT) and at high latitudes (GISS II'), respectively. We show that excessive cross-tropopause transport of 7Be corresponds to overestimated stratospheric contribution to tropospheric ozone. Our perspectives on STE in these meteorological fields based on 7Be simulations are consistent with previous modeling studies of tropospheric ozone using the same meteorological fields. We further apply observational constraints to other global models including GFDL AM2 and GEOS-Chem (driven by GEOS3-DAS and GEOS5-DAS). We conclude that the observational constraints for 7Be and observed 7Be total deposition fluxes can be used routinely as a first-order assessment of cross-tropopause transport in global models.

Motions of neutral hydrogen at high latitudes

1967 ◽  
Vol 31 ◽  
pp. 265-278 ◽  
Author(s):  
A. Blaauw ◽  
I. Fejes ◽  
C. R. Tolbert ◽  
A. N. M. Hulsbosch ◽  
E. Raimond
Keyword(s):  
Surface Density ◽  
Velocity Dispersion ◽  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
High Latitudes ◽  
Low Velocity

Earlier investigations have shown that there is a preponderance of negative velocities in the hydrogen gas at high latitudes, and that in certain areas very little low-velocity gas occurs. In the region 100° &lt;l&lt; 250°, + 40° &lt;b&lt; + 85°, there appears to be a disturbance, with velocities between - 30 and - 80 km/sec. This ‘streaming’ involves about 3000 (r/100)2solar masses (rin pc). In the same region there is a low surface density at low velocities (|V| &lt; 30 km/sec). About 40% of the gas in the disturbance is in the form of separate concentrations superimposed on a relatively smooth background. The number of these concentrations as a function of velocity remains constant from - 30 to - 60 km/sec but drops rapidly at higher negative velocities. The velocity dispersion in the concentrations varies little about 6·2 km/sec. Concentrations at positive velocities are much less abundant.

Long-term Cyclic Variations of Prominences, Green and Red Coronae over Solar Cycles

2000 ◽  
Vol 179 ◽  
pp. 201-204
Author(s):  
Vojtech Rušin ◽  
Milan Minarovjech ◽  
Milan Rybanský
Keyword(s):  
Emission Lines ◽  
High Latitudes ◽  
Green Line ◽  
Solar Cycles ◽  
The South ◽  
Coronal Emission ◽  
Local Maxima ◽  
The North ◽  
Cyclic Variations

AbstractLong-term cyclic variations in the distribution of prominences and intensities of green (530.3 nm) and red (637.4 nm) coronal emission lines over solar cycles 18–23 are presented. Polar prominence branches will reach the poles at different epochs in cycle 23: the north branch at the beginning in 2002 and the south branch a year later (2003), respectively. The local maxima of intensities in the green line show both poleward- and equatorward-migrating branches. The poleward branches will reach the poles around cycle maxima like prominences, while the equatorward branches show a duration of 18 years and will end in cycle minima (2007). The red corona shows mostly equatorward branches. The possibility that these branches begin to develop at high latitudes in the preceding cycles cannot be excluded.

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