The challenges of representing vertical motion in numerical models

2018 ◽  
Author(s):  
Ousmane O. Sy ◽  
Derek J. Posselt ◽  
Susan C. van den Heever ◽  
Ziad S. Haddad ◽  
Graeme L. Stephens ◽  
...  
Keyword(s):  
Numerical Models ◽  
Vertical Motion

scholarly journals A global survey of cloud overlap based on CALIPSO and CloudSat measurements

2015 ◽  
Vol 15 (1) ◽  
pp. 519-536 ◽  
Author(s):  
J. Li ◽  
J. Huang ◽  
K. Stamnes ◽  
T. Wang ◽  
Q. Lv ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Numerical Models ◽  
Vertical Motion ◽  
Warm Pool ◽  
Central Pacific ◽  
Cloud Systems ◽  
Central Pacific Ocean ◽  
Convective Clouds ◽  
Vertical Distributions ◽  
Global Mean

Abstract. Using 2B-CLDCLASS-LIDAR (radar–lidar) cloud classification and 2B-FLXHR-LIDAR radiation products from CloudSat over 4 years, this study evaluates the co-occurrence frequencies of different cloud types, analyzes their along-track horizontal scales and cloud radiative effects (CREs), and utilizes the vertical distributions of cloud types to evaluate cloud-overlap assumptions. The statistical results show that high clouds, altostratus (As), altocumulus (Ac) and cumulus (Cu) tend to coexist with other cloud types. However, stratus (St) (or stratocumulus, Sc), nimbostratus (Ns) and convective clouds are much more likely to exhibit individual features than other cloud types. On average, altostratus-over-stratus/stratocumulus cloud systems have a maximum horizontal scale of 17.4 km, with a standard deviation of 23.5 km. Altocumulus-over-cumulus cloud types have a minimum scale of 2.8 km, with a standard deviation of 3.1 km. By considering the weight of each multilayered cloud type, we find that the global mean instantaneous net CREs of multilayered cloud systems during the daytime are approximately −41.3 and −50.2 W m−2, which account for 40.1 and 42.3% of the global mean total net CREs at the top of the atmosphere (TOA) and at the surface, respectively. The radiative contributions of high-over-altocumulus and high-over-stratus/stratocumulus (or cumulus) in the all multilayered cloud systems are dominant due to their frequency. Considering the overlap of cloud types, the cloud fraction based on the random overlap assumption is underestimated over vast oceans, except in the west-central Pacific Ocean warm pool. Obvious overestimations mainly occur over tropical and subtropical land masses. In view of a lower degree of overlap than that predicted by the random overlap assumption to occur over the vast ocean, particularly poleward of 40° S, the study therefore suggests that a linear combination of minimum and random overlap assumptions may further improve the predictions of actual cloud fractions for multilayered cloud types (e.g., As + St/Sc and Ac + St/Sc) over the Southern Ocean. The establishment of a statistical relationship between multilayered cloud types and the environmental conditions (e.g., atmospheric vertical motion, convective stability and wind shear) would be useful for parameterization design of cloud overlap in numerical models.

scholarly journals Determining the Plio-Quaternary uplift of the southern French massif-Central; a new insights for intraplate orogen dynamics

2019 ◽  
Author(s):  
Oswald Malcles ◽  
Philippe Vernant ◽  
Jean Chéry ◽  
Pierre Camps ◽  
Gaël Cazes ◽  
...  
Keyword(s):  
Numerical Models ◽  
Morphological Evolution ◽  
Vertical Motion ◽  
French Massif Central ◽  
Dynamic Topography ◽  
Active Deformation ◽  
Massif Central ◽  
The North ◽  
Cave System ◽  
Clay Deposits

Abstract. The evolution of intra-plate orogens is still poorly understood. Yet, this is of major importance for understanding the Earth and plate dynamic, as well as the link between surface and deep geodynamic processes. The French Massif Central is an intraplate orogen with a mean elevation of 1000 m, with the highest peak elevations ranging from 1500 m to 1885 m. However, active deformation of the region is still debated due to scarce evidence either from geomorphological or geophysical (i.e. geodesy and seismology) data. Because the Cévennes margin allows the use of karst sediments geochronology and morphometrical analysis, we study the vertical displacements of that region: the southern part of the French Massif-Central. Geochronology and morphometrical results, helped with lithospheric-scale numerical modelling, allow, then, a better understanding of this intraplate-orogen evolution and dynamic. Using the ability of the karst to durably record morphological evolution, we first quantify the incision rates. We then investigate tilting of geomorphological benchmarks by means of a high-resolution DEM. We finally use the newly quantified incision rates to constrain numerical models and compare the results with the geomorphometric study. We show that absolute burial age (10Be/26Al on quartz cobbles) and the paleomagnetic analysis of karstic clay deposits for multiple cave system over a large elevation range correlate consistently. This correlation indicates a regional incision rate of 83.4 +17.3/−5.4 m Ma−1 during the last ca 4 Myrs (Plio-Quaternary). Moreover, we point out through the analysis of 55 morphological benchmarks that the studied region has undergone a regional southward tilting. This tilting is expected as being due to a differential vertical motion between the north and southern part of the studied area. Numerical models show that erosion-induced isostatic rebound can explain up to two-thirds of the regional uplift deduced from dating technics and are consistent with the southward tilting obtain from morphological analysis. We presume that the remaining part is related to dynamic topography or thermal isostasy due to the Massif Central plio-quaternary magmatism.

scholarly journals Thinning leads to calving-style changes at Bowdoin Glacier, Greenland

2020 ◽  
Author(s):  
Eef C. H. van Dongen ◽  
Guillaume Jouvet ◽  
Shin Sugiyama ◽  
Evgeny A. Podolskiy ◽  
Martin Funk ◽  
...  
Keyword(s):  
Mass Loss ◽  
Numerical Models ◽  
Mass Loss Rate ◽  
Ice Sheet ◽  
Vertical Motion ◽  
Greenland Ice Sheet ◽  
Remote Sensing Data ◽  
Full Spectrum ◽  
Additional Support ◽  
Behaviour Changes

Abstract. Ice mass loss from the Greenland Ice Sheet is the largest single contributor to sea-level rise in the 21st century. The mass loss rate has accelerated in recent decades mainly due to thinning and retreat of its outlet glaciers. The diverse calving mechanisms responsible for tidewater glacier retreat are not fully understood yet. Since a tidewater glacier’s sensitivity to external forcings depends on its calving style, a detailed insight into calving processes is necessary to improve projections of ice sheet mass loss by calving. As tidewater glaciers are mostly thinning, their calving styles are expected to change. Here, we study calving behaviour changes under a thinning regime at Bowdoin Glacier, Northwest Greenland, by combining field and remote sensing data from 2015 to 2019. Previous studies showed that major calving events in 2015 and 2017 were driven by hydro-fracturing and melt-undercutting. New observations from UAV imagery and a GPS network installed at the calving front in 2019 suggest ungrounding and buoyant calving have recently occurred, as they show (1) increasing tidal modulation of vertical motion compared to previous years, (2) absence of a surface crevasse prior to calving, and (3) uplift and horizontal surface compression prior to calving. Furthermore, an inventory of calving events from 2015 to 2019 based on satellite imagery provides additional support for a change towards buoyant calving since it shows an increasing occurrence of calving events outside of the melt season. The observed change of calving style could lead to a possible retreat of the terminus, which has been stable since 2013. We therefore highlight the need for high-resolution monitoring to detect changing calving styles and numerical models that cover the full spectrum of calving mechanisms to improve projections of ice sheet mass loss by calving.

scholarly journals Determining the Plio-Quaternary uplift of the southern French Massif Central; a new insight for intraplate orogen dynamics

Solid Earth ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 241-258 ◽  
Author(s):  
Oswald Malcles ◽  
Philippe Vernant ◽  
Jean Chéry ◽  
Pierre Camps ◽  
Gaël Cazes ◽  
...  
Keyword(s):  
High Resolution ◽  
Numerical Models ◽  
Morphological Evolution ◽  
Vertical Motion ◽  
French Massif Central ◽  
Dynamic Topography ◽  
Active Deformation ◽  
Massif Central ◽  
Clay Deposits ◽  
Triggering Process

Abstract. The evolution of intraplate orogens is still poorly understood. Yet, it is of major importance for understanding the Earth and plate dynamics, as well as the link between surface and deep geodynamic processes. The French Massif Central is an intraplate orogen with a mean elevation of 1000 m, with the highest peak elevations ranging from 1500 to 1885 m. However, active deformation of the region is still debated due to scarce evidence either from geomorphological or geodetic and seismologic data. We focus our study on the southern part of the Massif Central, known as the Cévennes and Grands Causses, which is a key area to study the relationship between the recent geological deformation and landscape evolution. This can be done through the study of numerous karst systems with trapped sediments combined with the analysis of a high-resolution digital elevation model (DEM). Using the ability of karst to durably record morphological evolution, we first quantify the incision rates. We then investigate tilting of geomorphological benchmarks by means of a high-resolution DEM. We finally use the newly quantified incision rates to constrain numerical models and compare the results with the geomorphometric study. We show that absolute burial age (10Be∕26Al on quartz cobbles) and the paleomagnetic analysis of karstic clay deposits for multiple cave system over a large elevation range correlate consistently. This correlation indicates a regional incision rate of 83 +17/-5 m Ma−1 during the last ca. 4 Myr (Pliocene–Quaternary). Moreover, we point out through the analysis of 55 morphological benchmarks that the studied region has undergone a regional southward tilting. This tilting is expected as being due to a differential vertical motion between the northern and southern part of the studied area. Numerical models show that erosion-induced isostatic rebound can explain up to two-thirds of the regional uplift deduced from the geochronological results and are consistent with the southward tilting derived from morphological analysis. We presume that the remaining unexplained uplift is related to dynamic topography or thermal isostasy due to the Massif Central Pliocene–Quaternary magmatism. Integrating both geochronology and morphometrical results into lithospheric-scale numerical models allows a better understanding of this intraplate–orogen evolution and dynamic. We assume that the main conclusions are true to the general case of intraplate deformation. That is to say, once the topography has been generated by a triggering process, rock uplift is then enhanced by erosion and isostatic adjustment leading to a significant accumulation of mainly vertical deformation.

Analysis Guidelines and Application of a Riser-Soil Interaction Model Including Trench Effects

2004 ◽  
Author(s):  
Bernt J. Leira ◽  
Elizabeth Passano ◽  
Daniel Karunakaran ◽  
Knut-Aril Farnes ◽  
Egil Giertsen
Keyword(s):  
Strong Influence ◽  
Numerical Models ◽  
Interaction Model ◽  
Vertical Motion ◽  
Response Analysis ◽  
Response Characteristics ◽  
General Overview ◽  
Typical Behaviour ◽  
Basic Input ◽  
Soil Pipe

A general overview of design aspects related to metal catenary risers is first given. Response characteristics of these types of riser configurations are considered. It is subsequently focused on models for soil-pipe interaction, which have a strong influence on computed riser stresses in the touch-down region. The so-called CARISIMA models for riser-soil interaction in relation to horizontal and vertical motion (i.e.horizontal resistance and suction) are presented. Inherent limitations of the models are summarised. Basic input parameters are described, considerations relevant for establishment of initial trench profile are given, and examples of riser response analysis are presented. Typical behaviour of the numerical models which is observed in the example analyses is also reported.

scholarly journals The dynamics of forearc - back-arc vertical motion: numerical models and observations from the Mediterranean

2021 ◽  
Author(s):  
Attila Balazs ◽  
Claudio Faccena ◽  
Taras V. Gerya ◽  
Kosuke Ueda ◽  
Francesca Funiciello
Keyword(s):  
Numerical Models ◽  
Vertical Motion ◽  
The Mediterranean ◽  
Back Arc

scholarly journals Impact of parameterized convection on a numerically simulated tropical Cyclone structure

MAUSAM ◽  
2021 ◽  
Vol 48 (2) ◽  
pp. 135-156
Author(s):  
MUKUT B. MATHUR
Keyword(s):  
Numerical Models ◽  
Vertical Motion ◽  
Horizontal Resolution ◽  
Tropical Storm ◽  
Numerical Results ◽  
Lagrangian Model ◽  
Convective Heating ◽  
Time Step ◽  
Fine Mesh ◽  
The Impact

ABSTRACT. Condensational heating is a primary source of energy for disturbances like a tropical storm. The resolvable scale condensation and the parameterized convection, in many fine mesh numerical models, are evaluated at intervals greater than the time step, order of a minute, used for computing dynamical processes. The latent heating may depend on the model resolution and the interval at which the precipitation physics is evaluated. Numerical results from a series of short range forecasts are compared to study the impact of varying the horizontal resolution and the interval for evaluating condensation physics, and of excluding the parameterized convective heating. A horizontal grid spacing of 40 km (coarse mesh) or 20 km (fine mesh) in National Centers for Environmental Prediction's Quasi-Lagrangian Model (QLM), and the initial data for a tropical storm case, are utilized. Resolvable scale condensation is invoked only at supersaturated grid points, and a Kuo-type convective parameterization procedure is employed.   Significant structural differences are produced when the interval for computing both parameterized convection and resolvable scale heating is changed, and these differences broaden when the horizontal resolution is increased. The central warm cote structure and storm intensity are simulated better when both condensational processes are evaluated at an interval of twelve time steps than at each time step. Vertical columns in central storm area rapidly become convectively stable, and the maximum in vertical motion and strongest horizontal winds shift in the outer storm area, when both condensational processes are invoked at each time step. The central storm area remains conditionally unstable, and strongest winds develop close to the center, when both condensational processes are evaluated at intervals of twelve time steps.   The central storm area remains conditionally unstable also in the fine mesh experiment in which the parameterized convective heating is excluded and the resolvable scale heating is evaluated at each time step. Intense vertical motion and vigorous heating develop in deep vertical columns, indicating that the heating on the convective scale is simulated as the resolvable scale heating. The vertical distribution of heating and the storm structure, during the first six hours in this case, are similar to those in the fine mesh run in which both condensational processes are evaluated at intervals of twelve time steps. However, the storm intensifies more rapidly after 6 h in the former than in the later case. Numerical results from additional experiments are presented to show that predicted storm structure is modified with a change in interval for invoking either or both condensational processes, and these circulation differences are not due to the initial spin up.   Transfer of moisture and heat from low levels into the higher troposphere in cumulonimbus clouds takes place in several minutes. Above cited and other predictions from the QLM suggest that storm structure. intensity and motion in a mesoscale model are likely to, be improved when parameterized convective heating is included; however, a parameterization scheme that concurrently produces alterations in the entire model cloud depth should be invoked at intervals of several minutes.      

Further Experimental Investigations on Vortex Self-Induced Vibrations (VSIV) With a Small-Scale Catenary Riser Model

2017 ◽  
Author(s):  
Celso P. Pesce ◽  
Guilherme R. Franzini ◽  
André L. C. Fujarra ◽  
Rodolfo T. Gonçalves ◽  
Rafael Salles ◽  
...  
Keyword(s):  
Numerical Models ◽  
Vertical Motion ◽  
Experimental Tests ◽  
Experimental Results ◽  
Dynamic Responses ◽  
Experimental Methodology ◽  
Experimental Investigations ◽  
Small Scale ◽  
General View ◽  
Technical Literature

This paper presents further experimental results of the dynamic response of a small-scale catenary riser model subjected to sinusoidal vertical motion imposed to the top, as a continuation of a previous one, presented at OMAE’2013. In that paper, a general view of an innovative experimental methodology using underwater optical techniques was given, together with some experimental results on VSIV - Vortex Self-Induced Vibrations, also referred to as Heave-Induced Lateral Motion, or Vessel Motion Induced VIV. It was then shown that such a behavior recovered similar ones reported in the technical literature by other authors and resembled fundamental studies, by Sumer and Fredsøe. In the present paper, new experimental tests are reported and analyzed. A similar catenary configuration is assessed. The analysis of VSIV trajectories is made via space-frequency amplitude spectra and space-time amplitude scalograms, revealing rich dynamic responses. The results are meant to serve as an experimental basis, contributing to the understanding of the VSIV phenomenology and to the benchmarking of numerical models.

scholarly journals Thinning leads to calving-style changes at Bowdoin Glacier, Greenland

2021 ◽  
Vol 15 (2) ◽  
pp. 485-500
Author(s):  
Eef C. H. van Dongen ◽  
Guillaume Jouvet ◽  
Shin Sugiyama ◽  
Evgeny A. Podolskiy ◽  
Martin Funk ◽  
...  
Keyword(s):  
Mass Loss ◽  
Numerical Models ◽  
Mass Loss Rate ◽  
Ice Sheet ◽  
Vertical Motion ◽  
Greenland Ice Sheet ◽  
Remote Sensing Data ◽  
Full Spectrum ◽  
Additional Support ◽  
Behaviour Changes

Abstract. Ice mass loss from the Greenland ice sheet is the largest single contributor to sea level rise in the 21st century. The mass loss rate has accelerated in recent decades mainly due to thinning and retreat of its outlet glaciers. The diverse calving mechanisms responsible for tidewater glacier retreat are not fully understood yet. Since a tidewater glacier’s sensitivity to external forcings depends on its calving style, detailed insight into calving processes is necessary to improve projections of ice sheet mass loss by calving. As tidewater glaciers are mostly thinning, their calving styles are expected to change. Here, we study calving behaviour changes under a thinning regime at Bowdoin Glacier, north-western Greenland, by combining field and remote-sensing data from 2015 to 2019. Previous studies showed that major calving events in 2015 and 2017 were driven by hydro-fracturing and melt-undercutting. New observations from uncrewed aerial vehicle (UAV) imagery and a GPS network installed at the calving front in 2019 suggest ungrounding and buoyant calving have recently occurred as they show (1) increasing tidal modulation of vertical motion compared to previous years, (2) absence of a surface crevasse prior to calving, and (3) uplift and horizontal surface compression prior to calving. Furthermore, an inventory of calving events from 2015 to 2019 based on satellite imagery provides additional support for a change towards buoyant calving since it shows an increasing occurrence of calving events outside of the melt season. The observed change in calving style could lead to a possible retreat of the terminus, which has been stable since 2013. We therefore highlight the need for high-resolution monitoring to detect changing calving styles and numerical models that cover the full spectrum of calving mechanisms to improve projections of ice sheet mass loss by calving.

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