Atmospheric flows are governed by the equations of fluid dynamics. These equations are nonlinear. But because atmospheric flows are inhomogeneous and anisotropic, the nonlinearity may manifest itself only weakly through interactions of non-trivial mean flows with disturbances or eddies. In such situations, the quasi-linear (QL) approximation, that retains eddy-mean flow interactions but neglect eddy-eddy interactions, hold promise in resolving large-scale atmospheric dynamics. The statistics of the QL system corresponds to closing the hierarchy of statistical moments at the second order.
Hence, exploring QL dynamics paves the way for the development of direct statistical simulations of geophysical flows.
Using a hierarchy of idealized general circulation models, we identify when the QL approximation captures large-scale dynamics. We show that the QL dynamics fails to capture the flow when the dissipation of large-scale eddies occurs through strongly nonlinear eddy-eddy interactions in upper tropospheric surf zones, as it is often the case on Earth. But we demonstrate that the QL approximation captures eddy absorption when it arises from the shearing by the mean flow, for example when the eddy amplitude is small enough or the planetary rotation rate is large enough.
These results illustrate different classes of nonlinear processes that can control wave dissipation in the upper troposphere and show that in some parameter regimes the QL approximation is accurate to resolve large-scale dynamics.
This document provides an introduction and overview of the third version of the Cloud Security Alliance's "Security Guidance for Critical Areas of Focus in Cloud Computing". Some key points:
- It has been updated and expanded from the second version, with each section now assigned its own editor and peer reviewed by industry experts.
- There are now 14 domains covering issues like cloud architecture, governance, legal issues, compliance, data security, and security operations.
- The guidance is intended to help organizations strategically manage security in cloud services and adopt industry best practices.
This document provides an overview of a presentation on Salesforce DevOps. It begins with an introduction to DevOps culture and how it relates to technology. It then discusses the Salesforce DevOps ecosystem and tools for version control, continuous integration, continuous delivery, and testing. It presents a use case of implementing GitOps with Salesforce involving tracking changes in a version control system, deploying from feature branches to sandbox and production environments, and using GitHub actions for automation. It also demonstrates a GitHub workflow for continuous integration and delivery pipelines.
The document introduces Check Point's Quantum SD-WAN solution, which embeds an SD-WAN software blade into Check Point Quantum Gateways. This provides optimized and secure connectivity for branch offices while lowering costs compared to traditional MPLS networks. The SD-WAN blade offers capabilities like sub-second failover, steering of over 10,000 applications, and a complete SASE solution with consistent security policies across networks. Case studies demonstrate how the solution provided superior security and fulfilled requirements for resilient connectivity and a single converged security and SD-WAN appliance.
Impact of Karlovitz and Reynolds Numbers on Vortex Evolution Through FlameChris Bradley
This document summarizes research on simulating the interaction between vortices and premixed methane flames. The simulations varied the size and speed of the vortices relative to the flame to study the effect on vortex evolution. For small vortices, viscous diffusion dominated the vortex evolution. For large, slow vortices, baroclinic torque dominated and caused the vortex to decay into streaks of vorticity. For large, fast vortices, baroclinic torque canceled out and dilatation dominated the evolution. The simulations identified which terms in the vorticity equation - viscous diffusion, baroclinic torque, or dilatation - were most important for vortices of different sizes and speeds interacting
The document summarizes the status and findings of version 01.xx of the GOSAT TANSO-FTS SWIR Level 2 retrieval algorithm. It finds that 93% of level 1B data is removed through quality screening. The seasonal variations of XCO2 and XCH4 seen in the retrievals are generally consistent with prior knowledge, though some regional biases exist. The data quality and accumulation over time will enable further scientific analysis of trends, seasonal cycles and variability for carbon flux estimation.
This document discusses the collapse of turbulence in the atmospheric nocturnal boundary layer. It notes there are two nocturnal regimes: a weakly stable boundary layer with cloudy skies and strong winds, and a very stable boundary layer with clear skies and weak winds. It is important to predict these regimes accurately as they can impact fog, icy roads, smog, and frozen plant blossoms. The document also examines how cooling rates and wind speeds can impact the collapse of turbulence through numerical simulations, and compares the simulation results to theoretical predictions of turbulence collapse.
This document provides an introduction and overview of the third version of the Cloud Security Alliance's "Security Guidance for Critical Areas of Focus in Cloud Computing". Some key points:
- It has been updated and expanded from the second version, with each section now assigned its own editor and peer reviewed by industry experts.
- There are now 14 domains covering issues like cloud architecture, governance, legal issues, compliance, data security, and security operations.
- The guidance is intended to help organizations strategically manage security in cloud services and adopt industry best practices.
This document provides an overview of a presentation on Salesforce DevOps. It begins with an introduction to DevOps culture and how it relates to technology. It then discusses the Salesforce DevOps ecosystem and tools for version control, continuous integration, continuous delivery, and testing. It presents a use case of implementing GitOps with Salesforce involving tracking changes in a version control system, deploying from feature branches to sandbox and production environments, and using GitHub actions for automation. It also demonstrates a GitHub workflow for continuous integration and delivery pipelines.
The document introduces Check Point's Quantum SD-WAN solution, which embeds an SD-WAN software blade into Check Point Quantum Gateways. This provides optimized and secure connectivity for branch offices while lowering costs compared to traditional MPLS networks. The SD-WAN blade offers capabilities like sub-second failover, steering of over 10,000 applications, and a complete SASE solution with consistent security policies across networks. Case studies demonstrate how the solution provided superior security and fulfilled requirements for resilient connectivity and a single converged security and SD-WAN appliance.
Impact of Karlovitz and Reynolds Numbers on Vortex Evolution Through FlameChris Bradley
This document summarizes research on simulating the interaction between vortices and premixed methane flames. The simulations varied the size and speed of the vortices relative to the flame to study the effect on vortex evolution. For small vortices, viscous diffusion dominated the vortex evolution. For large, slow vortices, baroclinic torque dominated and caused the vortex to decay into streaks of vorticity. For large, fast vortices, baroclinic torque canceled out and dilatation dominated the evolution. The simulations identified which terms in the vorticity equation - viscous diffusion, baroclinic torque, or dilatation - were most important for vortices of different sizes and speeds interacting
The document summarizes the status and findings of version 01.xx of the GOSAT TANSO-FTS SWIR Level 2 retrieval algorithm. It finds that 93% of level 1B data is removed through quality screening. The seasonal variations of XCO2 and XCH4 seen in the retrievals are generally consistent with prior knowledge, though some regional biases exist. The data quality and accumulation over time will enable further scientific analysis of trends, seasonal cycles and variability for carbon flux estimation.
This document discusses the collapse of turbulence in the atmospheric nocturnal boundary layer. It notes there are two nocturnal regimes: a weakly stable boundary layer with cloudy skies and strong winds, and a very stable boundary layer with clear skies and weak winds. It is important to predict these regimes accurately as they can impact fog, icy roads, smog, and frozen plant blossoms. The document also examines how cooling rates and wind speeds can impact the collapse of turbulence through numerical simulations, and compares the simulation results to theoretical predictions of turbulence collapse.
This document summarizes results from analyzing CO2 and CH4 concentrations retrieved from GOSAT/TANSO-FTS TIR measurements. The TIR retrievals show reasonable latitudinal gradients for both gases, though CO2 has some high biases in the tropics and CH4 has occasional high concentration orbits there. Validation with aircraft and AIRS data show general agreement within uncertainties, helping to establish the reliability of the new TIR measurements for studying greenhouse gases.
EVALUATIONS OF WIND VECTORS OBSERVED BY ASCAT USING STATISTICAL DISTRIBUTIONSgrssieee
The document evaluates wind vectors observed by the Advanced Scatterometer (ASCAT) satellite using statistical analysis. It finds that ASCAT wind speeds and directions agree well with buoy observations. Global wind speed histograms vary by cross-track cell location. ASCAT wind directions show directivity relative to the antenna beams, with low wind speeds and outer cells showing alignment to the flight direction. Similar analyses are conducted for Oceansat-II scatterometer (OSCAT) data.
The document discusses using GIS tools to study glaciers and analyze changes in North American glaciers over time. Specific GIS data and tools discussed include Landsat imagery, digital elevation models, slope and aspect mapping, accumulation area ratio analysis, hypsography mapping, and DEM differencing to calculate changes in glacier area, volume, height and annual mass balance for several glaciers between 1948-1995. The analysis shows most glaciers experiencing significant loss of area, volume and negative annual mass balances.
1) Removing eddy-eddy interactions in a dry GCM causes the eddy momentum flux maximum to shift downward away from the upper troposphere, indicating these interactions are important for concentrating flux in the upper troposphere.
2) Restoring only barotropic triad interactions in the reduced model is enough to recover the upper troposphere flux maximum.
3) Baroclinic wave lifecycle experiments show the importance of eddy-eddy interactions, particularly near critical layers, for vorticity rearrangement and mixing that enhances the upper troposphere flux.
Jan Kyselý, Jan Picek, Romana Beranová: Estimating extremes in climate model ...Jiří Šmída
The proposed non-stationary POT model uses a time-dependent threshold estimated through quantile regression to model extremes in non-stationary climate data. This approach avoids issues with previous stationary POT models and models that use a fixed threshold. The non-stationary model separates changes in extremes into changes in the threshold and changes in variability. Spatial patterns of increases in high quantiles are influenced by both of these factors. Regression quantiles provide a natural way to set a time-dependent threshold in POT analysis.
The document presents a method to retrieve properties of biomass burning aerosols using a combination of near-UV radiance measurements from the GOSAT/CAI sensor and near-IR polarimetry measurements from the PARASOL/POLDER sensor. The method involves estimating ground reflectance, atmospheric light, aerosol models using refractive indices, vertical aerosol profiles from CALIPSO data, and retrieving aerosol optical thickness, Angstrom exponent and single scattering albedo. Validation with AERONET data shows the retrieved aerosol optical thickness and Angstrom exponent values match partially. The method demonstrates the biomass burning aerosol properties vary over plumes with optical depth and Angstrom exponent
The stable atmospheric boundary layer a challenge for wind turbine operatio...ndkelley
An overview presentation of the impact and challenge of the stable atmospheric boundary layer on wind turbine dynamics presented to AGU Fall Meeting 2008
This document discusses downscaling of global climate model (GCM) data to provide higher resolution climate change projections relevant for adaptation planning. It describes two main downscaling methods: dynamic downscaling using regional climate models, and statistical/empirical downscaling using statistical relationships between large-scale predictors and local predictands. Both methods have pros and cons related to computational expense, dependence on GCM outputs, and ability to represent local weather phenomena. The document emphasizes that downscaled climate projections have uncertainties and limitations but provide the best available scientific information for decision-making around climate change impacts and adaptation.
Nwtc seminar overview of the impact of turbulence on turbine dynamics, sept...ndkelley
Overview presentation on the impact of atmospheric turbulence on the dynamic response of wind turbines derived from 20 years of research at the National Renewable Energy Laboratory.
According to a recent IPCC report and other studies:
1) Global temperatures have increased by 0.74°C over the past 100 years, causing glaciers and ice sheets to melt at accelerating rates.
2) Glacier melt has contributed to a 1.8 mm per year rise in sea levels from 1961 to 2003.
3) Greenland and Antarctic ice sheets are losing mass rapidly, with Greenland's ice loss doubling between 1996 and 2005 due to melting concentrated in low-elevation coastal regions.
The document describes glaciers and periglacial landforms and processes. It defines different types of glaciers and explains glacial processes like formation, movement, erosion, transportation and deposition. This creates landforms like moraines, drumlins and eskers. Periglacial landscapes lacking glacial ice are also described, featuring permafrost and patterned ground. The Pleistocene epoch is summarized, noting continental glaciation, sea level changes, and paleoclimate studies of past climate variations.
The document discusses uncertainties in modeling precipitation and the hydrological cycle across spatial scales. It focuses on downscaling global climate model projections to local scales using examples from the Karakoram-Himalaya mountains. Several precipitation datasets are characterized, including issues with sparse station coverage, biases, and uncertainties inherent in interpolation methods. Modeling approaches aim to better understand precipitation changes and feed local processes back to large scales while navigating uncertainties at each step of the downscaling chain from global to local.
This document summarizes a seminar presentation on eddy current brakes given by a student at Jyothi Engineering College. It begins with the vision and mission of the mechanical engineering department. It then explains the working principle of eddy current brakes, which use electromagnetic induction to create resistance and slow objects down. The document discusses the two main types - circular brakes that use a disc between magnet poles, and linear brakes that use a rail. It covers advantages like no contact or wear, applications in trains and rollercoasters, and future prospects like replacing ordinary brakes. In conclusion, eddy current brakes provide a way to control high-speed vehicles without parts wear.
Air refrigeration system by Bell Coleman cycle and Vortex tubeaparnamalyala
This document describes the aim, introduction, working principles, experimental setup and results of a project comparing the Bell-Coleman refrigeration cycle to a vortex tube refrigeration system. The aim was to study the cold end temperatures and COP of different vortex tube designs. Four vortex tubes with varying dimensions, nozzle numbers, orifice sizes and Venturi designs were fabricated and their cooling rates and COPs compared. Results showed the vortex tube designs produced higher cooling effects and COPs than the Bell-Coleman cycle at the same power input. Vortex tube 1 with a 13.5mm diameter, 2 nozzles and orifice had the best performance.
This document summarizes a study on the effects of low-level wind shear orientation on low-level rotation in simulated supercell thunderstorms. The study uses the cloud model CM1 to simulate supercells under different low-level wind shear orientations. Results show that low-level vertical vorticity is strongest when the distance between the midlevel mesocyclone and maximum surface circulation is smallest. In the simulations, a 0 degree shear orientation relative to the deep-layer wind led to the smallest distance and strongest low-level rotation. Future work involves additional simulations and comparing results to real tornadic storms.
Climate downscaling aims to bridge the scale gap between global climate models (GCMs) and local decision-making needs. There are two main downscaling methods: statistical downscaling establishes empirical relationships between large-scale GCM outputs and local variables, while dynamical downscaling uses regional climate models nested within GCMs at higher resolution. Both methods make assumptions about stationary relationships between scales, and dynamical downscaling is more computationally expensive. Downscaling can provide added value like improved regional precipitation simulations, but choosing appropriate domains and bias-correction techniques is important. Statistical downscaling is presently more suitable than dynamical downscaling for seasonal forecasts.
Colloquium given at the Caltech star formation group (Feb. 24, 2015) and NASA/JPL (Feb. 26, 2015). The presentation features recent research highlights by myself and collaborators and is intended for a non-expert astronomy audience.
Alessandra Buonanno gave a lecture on the analytical and numerical relativity approaches used to model gravitational waveforms from inspiraling binary systems. She discussed how post-Newtonian theory, effective one body theory, and numerical relativity are used to approximately and exactly solve Einstein's field equations. She emphasized the crucial synergy between analytical and numerical relativity approaches to develop accurate gravitational waveform models like EOBNR and Phenom that have been used to infer astrophysics from LIGO/Virgo detections.
This document summarizes a study that used a high-resolution climate model to examine how tropical cyclone activity responds to increased greenhouse gas forcing and solar forcing. The model was run with various prescribed sea surface temperature profiles and CO2 concentrations. The results showed that increased CO2 led to a strong direct decrease but also a strong indirect increase in tropical cyclone frequency due to higher temperatures. Solar forcing did not have the same effects as CO2 forcing. Environmental variables like potential intensity and vertical wind speed decreased in all simulations, suggesting they are important predictors of tropical cyclone changes. Geoengineering was deemed unlikely to effectively counteract increased CO2 forcing impacts on tropical cyclones.
Earth-like lithospheric thickness and heat flow on Venus consistent with acti...Sérgio Sacani
Venus is Earth’s twin in size and radiogenic heat budget, yet it remains
unclear how Venus loses its heat absent plate tectonics. Most Venusian
stagnant-lid models predict a thick lithosphere with heat fow about half
that of Earth’s mobile-lid regime. Here we estimate elastic lithospheric
thickness at 75 locations on Venus using topographic fexure at 65 coronae—
quasi-circular volcano-tectonic features—determined from Magellan
altimetry data. We fnd an average thickness at coronae of 11 ± 7 km. This
implies an average heat fow of 101 ± 88 mW m−2, higher than Earth’ s
average but similar to terrestrial values in actively extending areas. For
some locations, such as the Parga Chasma rift zone, we estimate heat fow
exceeding 75 mW m−2. Combined with a low-resolution map of global elastic
thickness, this suggests that coronae typically form on thin lithosphere,
instead of locally thinning the lithosphere via plume heating, and that most
regions of low elastic thickness are best explained by high heat fow rather
than crustal compensation. Our analysis identifes likely areas of active
extension and suggests that Venus has Earth-like lithospheric thickness
and global heat fow ranges. Together with the planet’s geologic history,
our fndings support a squishy-lid convective regime that relies on plumes,
intrusive magmatism and delamination to increase heat fow.
This document summarizes results from analyzing CO2 and CH4 concentrations retrieved from GOSAT/TANSO-FTS TIR measurements. The TIR retrievals show reasonable latitudinal gradients for both gases, though CO2 has some high biases in the tropics and CH4 has occasional high concentration orbits there. Validation with aircraft and AIRS data show general agreement within uncertainties, helping to establish the reliability of the new TIR measurements for studying greenhouse gases.
EVALUATIONS OF WIND VECTORS OBSERVED BY ASCAT USING STATISTICAL DISTRIBUTIONSgrssieee
The document evaluates wind vectors observed by the Advanced Scatterometer (ASCAT) satellite using statistical analysis. It finds that ASCAT wind speeds and directions agree well with buoy observations. Global wind speed histograms vary by cross-track cell location. ASCAT wind directions show directivity relative to the antenna beams, with low wind speeds and outer cells showing alignment to the flight direction. Similar analyses are conducted for Oceansat-II scatterometer (OSCAT) data.
The document discusses using GIS tools to study glaciers and analyze changes in North American glaciers over time. Specific GIS data and tools discussed include Landsat imagery, digital elevation models, slope and aspect mapping, accumulation area ratio analysis, hypsography mapping, and DEM differencing to calculate changes in glacier area, volume, height and annual mass balance for several glaciers between 1948-1995. The analysis shows most glaciers experiencing significant loss of area, volume and negative annual mass balances.
1) Removing eddy-eddy interactions in a dry GCM causes the eddy momentum flux maximum to shift downward away from the upper troposphere, indicating these interactions are important for concentrating flux in the upper troposphere.
2) Restoring only barotropic triad interactions in the reduced model is enough to recover the upper troposphere flux maximum.
3) Baroclinic wave lifecycle experiments show the importance of eddy-eddy interactions, particularly near critical layers, for vorticity rearrangement and mixing that enhances the upper troposphere flux.
Jan Kyselý, Jan Picek, Romana Beranová: Estimating extremes in climate model ...Jiří Šmída
The proposed non-stationary POT model uses a time-dependent threshold estimated through quantile regression to model extremes in non-stationary climate data. This approach avoids issues with previous stationary POT models and models that use a fixed threshold. The non-stationary model separates changes in extremes into changes in the threshold and changes in variability. Spatial patterns of increases in high quantiles are influenced by both of these factors. Regression quantiles provide a natural way to set a time-dependent threshold in POT analysis.
The document presents a method to retrieve properties of biomass burning aerosols using a combination of near-UV radiance measurements from the GOSAT/CAI sensor and near-IR polarimetry measurements from the PARASOL/POLDER sensor. The method involves estimating ground reflectance, atmospheric light, aerosol models using refractive indices, vertical aerosol profiles from CALIPSO data, and retrieving aerosol optical thickness, Angstrom exponent and single scattering albedo. Validation with AERONET data shows the retrieved aerosol optical thickness and Angstrom exponent values match partially. The method demonstrates the biomass burning aerosol properties vary over plumes with optical depth and Angstrom exponent
The stable atmospheric boundary layer a challenge for wind turbine operatio...ndkelley
An overview presentation of the impact and challenge of the stable atmospheric boundary layer on wind turbine dynamics presented to AGU Fall Meeting 2008
This document discusses downscaling of global climate model (GCM) data to provide higher resolution climate change projections relevant for adaptation planning. It describes two main downscaling methods: dynamic downscaling using regional climate models, and statistical/empirical downscaling using statistical relationships between large-scale predictors and local predictands. Both methods have pros and cons related to computational expense, dependence on GCM outputs, and ability to represent local weather phenomena. The document emphasizes that downscaled climate projections have uncertainties and limitations but provide the best available scientific information for decision-making around climate change impacts and adaptation.
Nwtc seminar overview of the impact of turbulence on turbine dynamics, sept...ndkelley
Overview presentation on the impact of atmospheric turbulence on the dynamic response of wind turbines derived from 20 years of research at the National Renewable Energy Laboratory.
According to a recent IPCC report and other studies:
1) Global temperatures have increased by 0.74°C over the past 100 years, causing glaciers and ice sheets to melt at accelerating rates.
2) Glacier melt has contributed to a 1.8 mm per year rise in sea levels from 1961 to 2003.
3) Greenland and Antarctic ice sheets are losing mass rapidly, with Greenland's ice loss doubling between 1996 and 2005 due to melting concentrated in low-elevation coastal regions.
The document describes glaciers and periglacial landforms and processes. It defines different types of glaciers and explains glacial processes like formation, movement, erosion, transportation and deposition. This creates landforms like moraines, drumlins and eskers. Periglacial landscapes lacking glacial ice are also described, featuring permafrost and patterned ground. The Pleistocene epoch is summarized, noting continental glaciation, sea level changes, and paleoclimate studies of past climate variations.
The document discusses uncertainties in modeling precipitation and the hydrological cycle across spatial scales. It focuses on downscaling global climate model projections to local scales using examples from the Karakoram-Himalaya mountains. Several precipitation datasets are characterized, including issues with sparse station coverage, biases, and uncertainties inherent in interpolation methods. Modeling approaches aim to better understand precipitation changes and feed local processes back to large scales while navigating uncertainties at each step of the downscaling chain from global to local.
This document summarizes a seminar presentation on eddy current brakes given by a student at Jyothi Engineering College. It begins with the vision and mission of the mechanical engineering department. It then explains the working principle of eddy current brakes, which use electromagnetic induction to create resistance and slow objects down. The document discusses the two main types - circular brakes that use a disc between magnet poles, and linear brakes that use a rail. It covers advantages like no contact or wear, applications in trains and rollercoasters, and future prospects like replacing ordinary brakes. In conclusion, eddy current brakes provide a way to control high-speed vehicles without parts wear.
Air refrigeration system by Bell Coleman cycle and Vortex tubeaparnamalyala
This document describes the aim, introduction, working principles, experimental setup and results of a project comparing the Bell-Coleman refrigeration cycle to a vortex tube refrigeration system. The aim was to study the cold end temperatures and COP of different vortex tube designs. Four vortex tubes with varying dimensions, nozzle numbers, orifice sizes and Venturi designs were fabricated and their cooling rates and COPs compared. Results showed the vortex tube designs produced higher cooling effects and COPs than the Bell-Coleman cycle at the same power input. Vortex tube 1 with a 13.5mm diameter, 2 nozzles and orifice had the best performance.
This document summarizes a study on the effects of low-level wind shear orientation on low-level rotation in simulated supercell thunderstorms. The study uses the cloud model CM1 to simulate supercells under different low-level wind shear orientations. Results show that low-level vertical vorticity is strongest when the distance between the midlevel mesocyclone and maximum surface circulation is smallest. In the simulations, a 0 degree shear orientation relative to the deep-layer wind led to the smallest distance and strongest low-level rotation. Future work involves additional simulations and comparing results to real tornadic storms.
Climate downscaling aims to bridge the scale gap between global climate models (GCMs) and local decision-making needs. There are two main downscaling methods: statistical downscaling establishes empirical relationships between large-scale GCM outputs and local variables, while dynamical downscaling uses regional climate models nested within GCMs at higher resolution. Both methods make assumptions about stationary relationships between scales, and dynamical downscaling is more computationally expensive. Downscaling can provide added value like improved regional precipitation simulations, but choosing appropriate domains and bias-correction techniques is important. Statistical downscaling is presently more suitable than dynamical downscaling for seasonal forecasts.
Colloquium given at the Caltech star formation group (Feb. 24, 2015) and NASA/JPL (Feb. 26, 2015). The presentation features recent research highlights by myself and collaborators and is intended for a non-expert astronomy audience.
Alessandra Buonanno gave a lecture on the analytical and numerical relativity approaches used to model gravitational waveforms from inspiraling binary systems. She discussed how post-Newtonian theory, effective one body theory, and numerical relativity are used to approximately and exactly solve Einstein's field equations. She emphasized the crucial synergy between analytical and numerical relativity approaches to develop accurate gravitational waveform models like EOBNR and Phenom that have been used to infer astrophysics from LIGO/Virgo detections.
This document summarizes a study that used a high-resolution climate model to examine how tropical cyclone activity responds to increased greenhouse gas forcing and solar forcing. The model was run with various prescribed sea surface temperature profiles and CO2 concentrations. The results showed that increased CO2 led to a strong direct decrease but also a strong indirect increase in tropical cyclone frequency due to higher temperatures. Solar forcing did not have the same effects as CO2 forcing. Environmental variables like potential intensity and vertical wind speed decreased in all simulations, suggesting they are important predictors of tropical cyclone changes. Geoengineering was deemed unlikely to effectively counteract increased CO2 forcing impacts on tropical cyclones.
Earth-like lithospheric thickness and heat flow on Venus consistent with acti...Sérgio Sacani
Venus is Earth’s twin in size and radiogenic heat budget, yet it remains
unclear how Venus loses its heat absent plate tectonics. Most Venusian
stagnant-lid models predict a thick lithosphere with heat fow about half
that of Earth’s mobile-lid regime. Here we estimate elastic lithospheric
thickness at 75 locations on Venus using topographic fexure at 65 coronae—
quasi-circular volcano-tectonic features—determined from Magellan
altimetry data. We fnd an average thickness at coronae of 11 ± 7 km. This
implies an average heat fow of 101 ± 88 mW m−2, higher than Earth’ s
average but similar to terrestrial values in actively extending areas. For
some locations, such as the Parga Chasma rift zone, we estimate heat fow
exceeding 75 mW m−2. Combined with a low-resolution map of global elastic
thickness, this suggests that coronae typically form on thin lithosphere,
instead of locally thinning the lithosphere via plume heating, and that most
regions of low elastic thickness are best explained by high heat fow rather
than crustal compensation. Our analysis identifes likely areas of active
extension and suggests that Venus has Earth-like lithospheric thickness
and global heat fow ranges. Together with the planet’s geologic history,
our fndings support a squishy-lid convective regime that relies on plumes,
intrusive magmatism and delamination to increase heat fow.
The Sun’s differential rotation is controlled by high- latitude baroclinicall...Sérgio Sacani
Rapidly rotating fluids have a rotation profile that depends only on the distance from the rotation axis, in accor-dance with the Taylor- Proudman theorem. Although the Sun was expected to be such a body, helioseismology showed that the rotation rate in the convection zone is closer to constant on radii. It has been postulated that this deviation is due to the poles being warmer than the equator by a few degrees. Using numerical simulations, we show that the pole- to-equator temperature difference cannot exceed 7 kelvin as a result of the back- reaction of the high- latitude baroclinically unstable inertial modes. The observed amplitudes of the modes further indicate that this maximum temperature difference is reached in the Sun. We conclude that the Sun’s latitudinal differential rotation reaches its maximum allowed value
Interannual and decadal variations of Antarctic ice shelves using multi-mission satellite radar altimetry, and links with oceanic and atmospheric forcings
From the workshop "High-Resolution Submillimeter Spectroscopy of the Interste...Lars E. Kristensen
Presentation given at the workshop "High-Resolution Submillimeter Spectroscopy of the Interstellar Medium and Star Forming Regions — From Herschel to ALMA and Beyond" held in Zakopane, Poland, May 2015: https://fox.ncac.torun.pl/export/herschel2alma/?slcn=main
Science Express Paper by: Kevin B. Stevenson et al.GOASA
- Spectroscopic phase curve observations of the exoplanet WASP-43b using the Hubble Space Telescope revealed a distinct increase in flux as the dayside rotated into view, peaking prior to secondary eclipse.
- Analysis of the spectrally resolved phase curves showed wavelength-dependent amplitudes, phase shifts, and eclipse depths, allowing inference of the temperature structure and molecular abundances at 15 orbital phases.
- Atmospheric modeling found water to be the dominant absorber influencing the phase-resolved emission spectra. The data showed large day-night temperature variations at all measured altitudes and a monotonically decreasing temperature with pressure.
This document provides information about homework help resources and an online physics study guide. It begins with links to websites for research paper help, online tutoring, and freelance tutoring sites. It then provides a preface and overview of the physics study guide which is intended to supplement an introductory college physics course. The guide is organized into three sections covering various physics concepts and includes appendices with physics constants and other reference information.
Quality factor of seismic coda waves in garhwaliaemedu
This document analyzes seismic coda wave attenuation in the Garhwal Himalayan region using data from 75 earthquakes recorded between 2004-2006. Coda quality factor (QC) values were estimated at different frequencies using a lapse time of 50 seconds and four coda window lengths. QC was found to fit a power law relationship with frequency, with exponents ranging from 0.967 to 1.016. Lower QC values at lower frequencies indicate higher attenuation, while higher QC values at higher frequencies indicate lower attenuation, suggesting heterogeneity decreases with depth in the study region.
Quality factor of seismic coda waves in garhwal himalayasiaemedu
This document analyzes seismic coda wave attenuation in the Garhwal Himalayan region using data from 75 earthquakes recorded between 2004-2006. Coda quality factor (QC) values were estimated at different frequencies using a lapse time of 50 seconds and four coda window lengths. QC was found to fit a power law relationship with frequency, with exponents ranging from 0.967 to 1.016. Lower QC values at lower frequencies indicate higher attenuation, while higher QC values at higher frequencies indicate lower attenuation, suggesting heterogeneity decreases with depth in the study region.
Quality factor of seismic coda waves in garhwal himalayas 2IAEME Publication
This document analyzes seismic coda wave attenuation in the Garhwal Himalayan region using data from 75 earthquakes recorded between 2004-2006. Coda quality factor (QC) values were estimated at different frequencies using a lapse time of 50 seconds and four coda window lengths. QC was found to fit a power law relationship with frequency, with exponents ranging from 0.967 to 1.016. Lower QC values at lower frequencies indicate higher attenuation, while higher QC values at higher frequencies indicate lower attenuation, suggesting heterogeneity decreases with depth in the study region.
Airborne and underground matter-wave interferometers: geodesy, navigation and...Philippe Bouyer
The remarkable success of atom coherent manipulation techniques has motivated competitive research and development in precision metrology. Matter-wave inertial sensors – accelerometers, gyrometers, gravimeters – based on these techniques are all at the forefront of their respective measurement classes. Atom inertial sensors provide nowadays about the best accelerometers and gravimeters and allow, for instance, to make the most precise monitoring of gravity or to device precise tests of the weak equivalence principle (WEP). I present here some recent advances in these fields
RINA - AOG 2017 - Numerical Modelling of Marine Structure Behaviours in Steep...Nick Bentley
The interaction of steep waves with structures is still not fully
understood, and is of great importance for the design and operation of these structures. A particular difficulty with modelling such interaction lies in necessity of modelling the waves field in a large scale of about 20 kilometers during a seat state (about 3 hours) and nonlinear behaviours of the structures. This presentation will describe how we tackle the difficulty to obtain the results of large scale nonlinear wave fields, to
numerically calculate the wave loading on fixed structures, to simulate the responses of single and two floating bodies to steep waves, and to investigate the effects of sloshing on the motion of floating structures.
The presentation will also discuss the difference between nonlinear wave loadings on a structures moving with a forward speed and on the structure which is fixed but subjected to a current with a speed same as the forward speed when they are all in steep waves. The difference is an issue because the forward speed of a moving structure should not affect the incoming wave field but the current may alter the incoming waves if nonlinearity must be taken into account. This will lead to the difference in wave loadings even though the encountering frequency is the same. This issue has not been well understood so far but would be important for the problems involving steeps waves.
Directional Spreading Effect on a Wave Energy ConverterElliot Song
The results demonstrate the importance of tuning the WEC system for specific wave environments to harvest most energy and to avoid potential capsize due to hurricanes etc.
Modeling extrasolar planetary atmospheres discusses techniques for modeling exoplanet atmospheres including:
1) 1D radiative models that reconstruct atmospheric temperature structures and simulate thermal emission and reflected light.
2) 2D and 3D global circulation models that simulate atmospheric winds and temperature distributions driven by stellar irradiation and planetary rotation.
3) Advanced 3D models that combine radiative transfer with hydrodynamics to model atmospheric chemistry, clouds, and winds. These simulations produce synthetic spectra and light curves for comparison to observations.
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1. Quasi-linear approaches to
large-scale atmospheric flows
(or: how turbulent is the atmosphere?)
Farid Ait-Chaalal(1),
in collaboration with:
Tapio Schneider(1,3) and Brad Marston(2)
(1)ETH, Zurich, Switzerland, (2)Brown University, Providence, USA
(3)Caltech, Pasadena, USA
2. The general circulation
Superposition of a mean flow and turbulent eddies
Source: EUMETSAT, https://www.youtube.com/watch?v=m2Gy8V0Dv78
March 2013 brightness temperature (clouds)
4. FMS GFDL pseudospectral dynamical core
Radiation: Newtonian relaxation of temperatures toward a fixed
profile
Convection: Relaxation of the vertical lapse rate toward
0.7 ⨉ (dry adiabatic)
Uniform surface, no seasonal cycle
Run at T85 (256 x 128 in physical space) with 30 vertical sigma-
levels
600 days average after 1400 days spin-up
(Held and Suarez, 1994; Schneider andWalker, 2006)
An idealized dry general circulation model (GCM)
Convenient to play with:We can change rotation rate, pole-to-
equator temperature contrast, surface friction, convection, etc….
6. Sigma
30
30
20
10
20
10
−10
295
320
350
a
−60 −30 0 30 60
0.2
0.8
−30
−20
−10
0
10
20
30
Colors:
Eddy momentum
flux (EMF)
convergence
Contours:
Zonal flow
(m s-1)
Dotted lines:
Potential
temperature (K)
Green line:
Tropopause
Eddy momentum
flux (EMF)
Friction on surface westerlies
balances vertically averaged
convergence of momentum
Friction on easterlies (trade winds)
balances vertically averaged
divergence of momentum
(Held 2000, Schneider 2006)
u0v0 cos
EMFconvergence(10-6ms-2)
Eddy zonal
wind
Eddy meridional
wind
Overbar:
zonal-time mean
Eddy momentum flux
An idealized dry GCM:The mean zonal flow
a = a + a0
7. Sigma
53
1
3
1
−5
−3
−1
−3
−1
a
−60 −30 0 30 60
0.2
0.8
−30
−20
−10
0
10
20
30
Colors:
Eddy momentum
flux (EMF)
convergence
(10-6 m s-2)
Contours:
Mass stream
function
(1010 kg s-1)
Dotted lines:
Potential
temperature (K)
Green line:
Tropopause
Ferrel cell
(Coriolis torque on the upper branch balances locally
EMF convergence)
Hadley cell
(Coriolis torque on the upper branch balances locally
EMF divergence)
(Held 2000, Schneider 2006,Walker and Schneider 2006, Korty and Schneider 2007, Levine and Schneider 2015, etc…)
An idealized dry GCM:The mean meridional flow
Streamfunction(1010kgs-1)
Eddy momentum flux
8. Heating the poles and cooling the equator
Warm pole
Cold tropics
Near surface
temperature
Near surface
relative vorticity
Westerlies
Easterlies
(Ait-Chaalal and Schneider, 2015)
9. Heating the poles and cooling the equator
Reversed insolation
Latitude
Sigma
2
2
−2
−10
−20
−40 −40
−60 −30 0 30 60
0.2
0.8
−10
−5
0
5
10
Latitude
Sigma
295
320
350
e
−60 −30 0 30 60
0.2
0.8
−1
0
1
Earth-Like
EMF(m2s-2)Streamfunction(1010kgs-1)
Latitude
Sigma
30
20
10
5
−5
−5
−60 −30 0 30 60
0.2
0.8
−40
−30
−20
−10
0
10
20
30
40
Latitude
Sigma
295
320
350
f
−60 −30 0 30 60
0.2
0.8
−6
0
6
Contours: Zonal mean flow (m/s) Dotted lines: Potential temperature (K) Green line:Tropopause
(Ait-Chaalal and Schneider, 2015)
EMF(m2s-2)Streamfunction(1010kgs-1)
10. Large-scale eddies and the general circulation
Large-scale motion in the atmosphere is controlled by eddy—
mean-flow interactions (e.g., Held 2000, Schneider 2006).
Atmospheric flows look linear from macroturbulent
scalings and do not exhibit nonlinear cascades of energy over a
wide range of parameters (Schneider and Walker 2006, Schneider
andWalker 2008, Chai andVallis 2014)
What happens if we retain eddy-mean flow
interactions and neglect eddy-eddy interactions, in
other words if we make a quasi-linear (QL)
approximation?
11. Why is the QL approximation interesting?
QL dynamics ~ closing the equations for statistical moments
at the second order
Is it possible to build statistical models to “solve climate”
based on QL dynamics as a closure strategy?
"More than any other theoretical procedure, numerical integration is also
subject to the criticism that it yields little insight into the problem. The
computed numbers are not only processed like data but they look like data,
and a study of them may be no more enlightening than a study of real
meteorological observations. An alternative procedure which does not
suffer this disadvantage consists of deriving a new system of equations
whose unknowns are the statistics themselves...."
Edward Lorenz, The Nature and Theory of the General Circulation of the
Atmosphere (1967)
12. The QL approximation
Take for example the meridional advection of a scalar (zonal mean/
eddy decomposition)
a = a + a0
@a
@t
= v
@a
@y
v
@a0
@y
v0 @a
@y
v0 @a0
@y
@a
@t
= v
@a
@y
v
@a0
@y
v0 @a
@y
v0
@a0
@y
becomes
Equation for the mean flow:
Equation for the eddies:
@a0
@t
= ¯v
@a0
@y
v0 @¯a
@y
(v0 @a0
@y
v0
@a0
@y
).
QL
@¯a
@t
= ¯v
@¯a
@y
v0
@a0
@y
.
Removing eddy-eddy interactions in the GCM:
Eddy-eddy interactions
(O’Gorman and Schneider 2007; Ait-Chaalal et al., 2015)
@a
@t
= v
@a
@y
= ¯v
@¯a
@y
¯v
@a0
@y
v0 @¯a
@y
v0 @a0
@y
13. The QL approximation conserves invariants consistent with the order of
truncation, for example zonal momentum and energy (Marston et al., 2014).
In the literature
Stochastic structural stability (S3T) theory to study coherent structures in
stable flows: Farrell, Ioannou, Bakas, Krommes, Parker, etc…
Cumulant expansions of second order (CE2): Marston, Srinivasan,Young, etc…
Some attempts to recover atmospheric statistics from linearized GCMs with a
stochastic forcing: Whitaker and Sardeshmuck, 1998; Zhang and Held 1999; Delsole
2001
Here: we look at unstable planetary baroclinic flows with large-scale forcing
and dissipation.
The QL approximation
14. Full
The QL approximation: Mean zonal flow
Contours:
Zonal flow (m/s)
Green line:
Tropopause
Sigma
30
20
10
a
−60 −30 0 30 60
0.2
0.8
−1
−0.5
0
0.5
Latitude
Sigma
40
20
10
10
b
−60 −30 0 30 60
0.2
0.8
−1
−0.5
0
0.5
(O’gorman and
Schneider, 2007)
QL
15. Eddy Momentum Flux Divergence
Colors:
Eddy momentum
flux (EMF)
Contours:
Zonal flow (m/s)
Dotted lines:
Potential
temperature (K)
Green line:
Tropopause
The QL approximation:The eddy momentum flux
EMF(m2s-2)EMF(m2s-2)
Full
Sigma
30
2010
a
−60 −30 0 30 60
0.2
0.8
−50
0
50
Latitude
Sigma
40
10
10
b
−60 −30 0 30 60
0.2
0.8
−20
−10
0
10
20
(Ait-Chaalal and
Schneider, 2015)
QL
16. Eddy Momentum Flux Divergence
Colors:
Eddy kinetic
energy (EKE)
Contours:
Zonal mean flow
(m/s)
Dotted lines:
Potential
temperature (K)
Green line:
Tropopause
EKE(m2s-2)EKE(m2s-2)
Full
Sigma
30
20
10
a
−60 −30 0 30 60
0.2
0.8
100
200
300
Latitude
Sigma
10
10
40
b
−60 −30 0 30 60
0.2
0.8
150
250
350
(Ait-Chaalal and
Schneider, 2015)
QL
0.5 (u02 + v02)
The QL approximation:The eddy kinetic energy
17. How is large-scale eddy decay captured in the QL
model?
Why is the eddy momentum flux not maximum in the upper
troposphere in the QL model ?
Why are weak momentum fluxes associated with high EKE in the
QL model?
The QL approximation: Summary
19. A prototype model for the upper troposphere
Two-dimensional flow (barotropic)
Wavenumber 6 perturbation in a westerly jet
Initial value problem: how does the perturbation decay when eddy-
eddy interactions are suppressed?
Relative vorticity field
Vorticity of the eddies about 6 times larger than that of the mean flow.
Rossby number of order 0.2 in mid-latitudes.
Jet relative vorticity Jet + eddies relative vorticity
21. “Earth-like” parameters, large-amplitude eddies
EQ
30N
60N
30S
60S
0 10 20 30 40 50
-0.01
-0.001
0
0.001
0.01
EQ
30N
60N
30S
60S
0 10 20 30 40 50
-0.01
-0.001
0
0.001
0.01
EQ
30N
60N
30S
60S
0 10 20 30 40 50
-0.01
-0.001
0
0.001
0.01
EQ
30N
60N
30S
60S
0 10 20 30 40 50
-0.01
-0.001
0
0.001
0.01
x10-3
10
1
0
-1
-10Eddy kinetic energy Eddy kinetic energy
Eddy momentum flux convergence Eddy momentum flux convergence
x10-3
10
0
-10
x10-3
10
0
-10
x10-3
10
1
0
-1
-10
Time Time
Time Time
(Ait-Chaalal et al., 2015)
Full QL (CE2)
An prototype model for the upper troposphere
22. The QL dynamics
d
T = 1.2 T = 4.0
T = 5.9 T = 17.5
a b
c e
V
10
0
-1
-10T = 7.5
X
X
1
Relativevorticity
Relative vorticity field evolution in the QL approximation
23. The fully nonlinear dynamics
Day 1.2 Day 4.0
Day 7.5 Day 17.5
a b
d e
Day 5.9c
7
0.7
0
-0.7
-7
X
X X X
T = 1.2 T = 4.0
T = 5.9 T = 7.5 T = 17.5
10
1
0
-1
-10-10
Relativevorticity
Relative vorticity field evolution in the fully nonlinear dynamics
(for some theory, seeWarn andWarn 1978 or Stewartson 1978)
24. Vorticity - streamfunction relationship:
Flow - streamfunction relationship:
Mean-flow and eddy vorticity equations:
Shear Eddy-eddy interactions Beta-term
“Rossby number”, ratio of the mean flow vorticity to the planetary rotation rate
Relative amplitude of the eddies to the mean flow (need not to be small !!)
A prototype model for the upper troposphere
25. Decreasing the amplitude of the eddies (by a factor 3)
Relative vorticity field
A prototype model for the upper troposphere
26. EQ
30N
60N
30S
60S
0 10 20
-0.001
-0.0001
0
0.0001
0.001
EQ
30N
60N
30S
60S
0 10 20
-0.001
-0.000
0
0.0001
0.001
EQ
30N
60N
30S
60S
0 10 20
-0.001
-0.0001
0
0.0001
0.001
EQ
30N
60N
30S
60S
0 10 20
-0.001
-0.0001
0
0.0001
0.001
x10-3
10
1
0
-1
-10Eddy kinetic energy Eddy kinetic energy
Eddy momentum flux convergence Eddy momentum flux convergence
x10-3
10
0
-10
x10-3
10
0
-10
x10-3
10
1
0
-1
-10
Time Time
Time Time
(Ait-Chaalal et al., 2015)
Full QL (CE2)
Decreasing the amplitude of the eddies (by a factor 3)
A prototype model for the upper troposphere
27. Mean-flow and eddy vorticity equations:
Shear Eddy-eddy interactions Beta-term
“Rossby number”, ratio of the mean flow vorticity to the planetary rotation rate
Relative amplitude of the eddies to the mean flow (need not to be small !!)
A prototype model for the upper troposphere
29. Eddy absorption can be linear or nonlinear, QL captures the later
but not for the former (in which case eddies are “reemitted”
from the surf zone).
Eddies need not to be “small” for linear absorption. Smaller is the
Rossby number, larger are the eddies that can be absorbed
linearly. A theory that would describe the transition is missing.
Is this relevant to a baroclinic atmosphere?
A prototype model for the upper troposphere
How is large-scale eddy decay captured in the QL
model?
30. Baroclinic wave lifecycle experiments
Initialize a zonal wavenumber 6 perturbation in the
zonally averaged circulation (fully nonlinear model)
Let it evolve without forcing and dissipation
Experiments run with the full model and the QL
model
Back to the (baroclinic) GCM
(Simmons and Hoskins, 1978; Thorncroft et al., 1993; etc…)
31. Time (days)
Conversion(m2
s−3
)
0 25 50 75 100
−1
0
1
x 10
−4
EAPE > EKE
ZKE > EKE
Time (days)
Conversion(m2
s−3
)
0 25 50 75 100
−1
0
1
x 10
−4
Baroclinic conversion: eddy
available potential energy
(EAPE) to eddy kinetic energy
(EKE).
Barotropic conversion: Zonal
kinetic energy (ZKE) to eddy
kinetic energy (EKE).
Back to the (baroclinic) GCM
Baroclinic wave lifecycle experiments
(Ait-Chaalal and Schneider, 2015)
32. Baroclinic wave lifecycle experiments
Day 42
Sigma
0 30 60
0.2
0.8 −4
0
4
Day 23
Sigma
0 30 60
0.2
0.8
−1
0
1
Time (days)
Conversion(m2
s−3
)
0 25 50 75 100
−1
0
1
x 10
−4
Time (days)
Conversion(m2
s−3
)
0 25 50 75 100
−1
0
1
x 10
−4
EAPE > EKE
ZKE > EKE
A2 B2
21
PVU
0
A1 B1
Full QL
a
b
c
QGPVFlux(10-5ms-2)
Latitude Latitude
Sigma
Grey arrows: Eliassen-Palm flux
(~ baroclinic equivalent of the
barotropic momentum flux)
Colors: Potential vorticity flux
(~ baroclinic equivalent of
the barotropic momentum flux
convergence)
Potential vorticity on the 300K isentrope
@¯u
@t
= r · F = (
@A
@t
)
r · F = v0q0
F = R cos
0
@
u0v0
f v0✓0/@p
¯✓
1
A
(Ait-Chaalal and Schneider, 2015)
33. Baroclinic wave lifecycle experiments
Day 46
Sigma
0 30 60
0.2
0.8 −4
0
4
Day 29
Sigma
0 30 60
0.2
0.8
−1
0
1
21
PVU
0
Full QL
a
b
c
Latitude Latitude
Sigma
QGPVFlux(10-5ms-2)
Time (days)
Conversion(m2
s−3
)
0 25 50 75 100
−1
0
1
x 10
−4
Time (days)
Conversion(m2
s−3
)
0 25 50 75 100
−1
0
1
x 10
−4
EAPE > EKE
ZKE > EKE
Potential vorticity on the 300K isentrope
Grey arrows: Eliassen-Palm flux
(~ baroclinic equivalent of the
barotropic momentum flux)
@¯u
@t
= r · F = (
@A
@t
)
r · F = v0q0
F = R cos
0
@
u0v0
f v0✓0/@p
¯✓
1
A
Colors: Potential vorticity flux
(~ baroclinic equivalent of
the barotropic momentum flux
convergence)
(Ait-Chaalal and Schneider, 2015)
34. Back to the (baroclinic) GCM
Sigma
30
2010
a
−60 −30 0 30 60
0.2
0.8
−50
0
50
Latitude
Sigma
40
10
10
b
−60 −30 0 30 60
0.2
0.8
−20
−10
0
10
20
Sigma
30
20
10
a
−60 −30 0 30 60
0.2
0.8
100
200
300
Latitude
Sigma
10
10
40
b
−60 −30 0 30 60
0.2
0.8
150
250
350
Full
QL
Eddy momentum flux Eddy kinetic energy
35. Example of a baroclinic flow in which QL works
Latitude
Sigma
40
40
−10
−60 −30 0 30 60
0.2
0.8
Latitude
Sigma
40
40
−60 −30 0 30 60
0.2
0.8
Latitude
Sigma
10
10
20
20
−60 −30 0 30 60
0.2
0.8
Latitude
Sigma
30 30
−60 −30 0 30 60
0.2
0.8
Full
QL
Earth-like Reduced surface friction
Also works in many other situations (e.g., the reversed insolation
experiment)
36. Conclusive remarks
Eddy-eddy interactions do matter for eddy absorption in the
upper troposphere.They have to be parametrized in some
way to achieve direct statistical simulations.
Eddy absorption can be linear in some regimes (without the
requirement of small-amplitude waves). In what case QL
dynamics and the second order cumulant expansion capture
the dynamics.
QL maybe more promising for giant plants, e.g. to study the
long-term evolution of jets.