scholarly journals Land–Ocean Warming Contrast over a Wide Range of Climates: Convective Quasi-Equilibrium Theory and Idealized Simulations

2013 ◽  
Vol 26 (12) ◽  
pp. 4000-4016 ◽  
Author(s):  
Michael P. Byrne ◽  
Paul A. O’Gorman
Keyword(s):  
Land Surface ◽  
General Circulation ◽  
Large Scale ◽  
Circulation Model ◽  
Ocean Warming ◽  
Quasi Equilibrium ◽  
Wide Range ◽  
The Difference ◽  
Limited Moisture ◽  
Lapse Rates

Abstract Surface temperatures increase at a greater rate over land than ocean in simulations and observations of global warming. It has previously been proposed that this land–ocean warming contrast is related to different changes in lapse rates over land and ocean because of limited moisture availability over land. A simple theory of the land–ocean warming contrast is developed here in which lapse rates are determined by an assumption of convective quasi-equilibrium. The theory predicts that the difference between land and ocean temperatures increases monotonically as the climate warms or as the land becomes more arid. However, the ratio of differential warming over land and ocean varies nonmonotonically with temperature for constant relative humidities and reaches a maximum at roughly 290 K. The theory is applied to simulations with an idealized general circulation model in which the continental configuration and climate are varied systematically. The simulated warming contrast is confined to latitudes below 50° when climate is varied by changes in longwave optical thickness. The warming contrast depends on land aridity and is larger for zonal land bands than for continents with finite zonal extent. A land–ocean temperature contrast may be induced at higher latitudes by enforcing an arid land surface, but its magnitude is relatively small. The warming contrast is generally well described by the theory, although inclusion of a land–ocean albedo contrast causes the theory to overestimate the land temperatures. Extensions of the theory are discussed to include the effect of large-scale eddies on the extratropical thermal stratification and to account for warming contrasts in both surface air and surface skin temperatures.

scholarly journals Global Meteorological Drought: A Synthesis of Current Understanding with a Focus on SST Drivers of Precipitation Deficits

2016 ◽  
Vol 29 (11) ◽  
pp. 3989-4019 ◽  
Author(s):  
Siegfried D. Schubert ◽  
Ronald E. Stewart ◽  
Hailan Wang ◽  
Mathew Barlow ◽  
Ernesto H. Berbery ◽  
...  
Keyword(s):  
Time Scales ◽  
Land Surface ◽  
General Circulation ◽  
Large Scale ◽  
Circulation Model ◽  
Meteorological Drought ◽  
Current Understanding ◽  
Northern Eurasia ◽  
Eastern Canada

Abstract Drought affects virtually every region of the world, and potential shifts in its character in a changing climate are a major concern. This article presents a synthesis of current understanding of meteorological drought, with a focus on the large-scale controls on precipitation afforded by sea surface temperature (SST) anomalies, land surface feedbacks, and radiative forcings. The synthesis is primarily based on regionally focused articles submitted to the Global Drought Information System (GDIS) collection together with new results from a suite of atmospheric general circulation model experiments intended to integrate those studies into a coherent view of drought worldwide. On interannual time scales, the preeminence of ENSO as a driver of meteorological drought throughout much of the Americas, eastern Asia, Australia, and the Maritime Continent is now well established, whereas in other regions (e.g., Europe, Africa, and India), the response to ENSO is more ephemeral or nonexistent. Northern Eurasia, central Europe, and central and eastern Canada stand out as regions with few SST-forced impacts on precipitation on interannual time scales. Decadal changes in SST appear to be a major factor in the occurrence of long-term drought, as highlighted by apparent impacts on precipitation of the late 1990s “climate shifts” in the Pacific and Atlantic SST. Key remaining research challenges include (i) better quantification of unforced and forced atmospheric variability as well as land–atmosphere feedbacks, (ii) better understanding of the physical basis for the leading modes of climate variability and their predictability, and (iii) quantification of the relative contributions of internal decadal SST variability and forced climate change to long-term drought.

scholarly journals Multivariable evaluation of land surface processes in forced and coupled modes reveals new error sources to the simulated water cycle in the IPSL (Institute Pierre Simon Laplace) climate model

2021 ◽  
Vol 25 (4) ◽  
pp. 2199-2221
Author(s):  
Hiroki Mizuochi ◽  
Agnès Ducharne ◽  
Frédérique Cheruy ◽  
Josefine Ghattas ◽  
Amen Al-Yaari ◽  
...  
Keyword(s):  
Land Surface ◽  
General Circulation ◽  
Climate Model ◽  
Water Cycle ◽  
Circulation Model ◽  
Coupled Modes ◽  
Error Sources ◽  
Area Index ◽  
Coupled Mode ◽  
The Difference

Abstract. Evaluating land surface models (LSMs) using available observations is important for understanding the potential and limitations of current Earth system models in simulating water- and carbon-related variables. To reveal the error sources of a LSM, five essential climate variables have been evaluated in this paper (i.e., surface soil moisture, evapotranspiration, leaf area index, surface albedo, and precipitation) via simulations with the IPSL (Institute Pierre Simon Laplace) LSM ORCHIDEE (Organizing Carbon and Hydrology in Dynamic Ecosystems) model, particularly focusing on the difference between (i) forced simulations with atmospheric forcing data (WATCH Forcing Data ERA-Interim – WFDEI) and (ii) coupled simulations with the IPSL atmospheric general circulation model. Results from statistical evaluation, using satellite- and ground-based reference data, show that ORCHIDEE is well equipped to represent spatiotemporal patterns of all variables in general. However, further analysis against various landscape and meteorological factors (e.g., plant functional type, slope, precipitation, and irrigation) suggests potential uncertainty relating to freezing and/or snowmelt, temperate plant phenology, irrigation, and contrasted responses between forced and coupled mode simulations. The biases in the simulated variables are amplified in the coupled mode via surface–atmosphere interactions, indicating a strong link between irrigation–precipitation and a relatively complex link between precipitation–evapotranspiration that reflects the hydrometeorological regime of the region (energy limited or water limited) and snow albedo feedback in mountainous and boreal regions. The different results between forced and coupled modes imply the importance of model evaluation under both modes to isolate potential sources of uncertainty in the model.

scholarly journals Effects of Rotation Rate and Seasonal Forcing on the ITCZ Extent in Planetary Atmospheres

2017 ◽  
Vol 74 (3) ◽  
pp. 665-678 ◽  
Author(s):  
Sean Faulk ◽  
Jonathan Mitchell ◽  
Simona Bordoni
Keyword(s):  
Rotation Rate ◽  
General Circulation ◽  
Circulation Model ◽  
Hadley Circulation ◽  
Earth’S Rotation ◽  
Quasi Equilibrium ◽  
Earth's Rotation ◽  
Weather Patterns ◽  
Rotation Rates ◽  
Wide Range

Abstract The authors study a wide range of atmospheric circulations with an idealized moist general circulation model to evaluate the mechanisms controlling intertropical convergence zone (ITCZ) migrations. They employ a zonally symmetric aquaplanet slab ocean of fixed depth and force top-of-atmosphere insolation to remain fixed at the pole for an “eternal solstice” simulation and also vary seasonally for a range of rotation rates, keeping all other parameters Earth-like. For rotation rates ΩE/8 and slower, a transient maximum in zonal-mean precipitation appears at the summer pole; however, the ITCZ associated with the ascending branch of the Hadley circulation lies at ~60°. The authors assess how widely used predictors of the ITCZ position perform in this wide parameter space. Standard predictors based on different estimates of the Hadley cell’s poleward extent are correlated with but overestimate off-equatorial ITCZ locations. Interestingly, in the eternal-solstice case for Earth’s rotation rate, the ITCZ remains at subtropical latitudes even though the lower-level moist static energy maximizes at the summer pole. While seemingly at odds with convective quasi-equilibrium arguments, this can happen because at Earth’s rotation rates, the thermal stratification set in convective regions can only be communicated within the tropics, where temperature gradients are constrained to be weak. The authors therefore develop an understanding of the ITCZ’s position based on top-of-atmosphere energetics and the boundary layer momentum budget and argue that friction and pressure gradient forces determine the region of maximum convergence, offering a modified dynamical perspective on the monsoon-like seasonal weather patterns of terrestrial planets.

scholarly journals Effects of Anthropogenic and Natural Forcings on the Summer Temperature Variations in East Asia during the 20th Century

Atmosphere ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 690 ◽  
Author(s):  
Sungbo Shim ◽  
Jinwon Kim ◽  
Seong Soo Yum ◽  
Hannah Lee ◽  
Kyung-On Boo ◽  
...  
Keyword(s):  
East Asia ◽  
20Th Century ◽  
Land Surface ◽  
General Circulation ◽  
Large Scale ◽  
Circulation Model ◽  
Volcanic Eruptions ◽  
Anthropogenic Aerosols ◽  
Cooling Period ◽  
Interaction Term

The effects of the emissions of anthropogenic greenhouse gases (GHGs), aerosols, and natural forcing on the summer-mean surface air temperature (TAS) in the East Asia (EA) land surface in the 20th century are analyzed using six-member coupled model inter-comparison project 5 (CMIP5) general circulation model (GCM) ensembles from five single-forcing simulations. The simulation with the observed GHG concentrations and aerosol emissions reproduces well the land-mean EA TAS trend characterized by warming periods in the early (1911–1940; P1) and late (1971–2000; P3) 20th century separated by a cooling period (1941–1970; P2). The warming in P1 is mainly due to the natural variability related to GHG increases and the long-term recovery from volcanic activities in late-19th/early-20th century. The cooling in P2 occurs as the combined cooling by anthropogenic aerosols and increased volcanic eruptions in the 1960s exceeds the warming by the GHG increases and the nonlinear interaction term. In P3, the combined warming by GHGs and the interaction term exceeds the cooling by anthropogenic aerosols to result in the warming. The SW forcing is not driving the TAS increase in P1/P3 as the shortwave (SW) forcing is heavily affected by the increased cloudiness and the longwave (LW) forcing dominates the SW forcing. The LW forcing to TAS cannot be separated from the LW response to TAS, preventing further analyses. The interaction among these forcing affects TAS via largely modifying the atmospheric water cycle, especially in P2 and P3. Key forcing terms on TAS such as the temperature advection related to large-scale circulation changes cannot be analyzed due to the lack of model data.

scholarly journals Moist Convection and the Thermal Stratification of the Extratropical Troposphere

2008 ◽  
Vol 65 (11) ◽  
pp. 3571-3583 ◽  
Author(s):  
Tapio Schneider ◽  
Paul A. O’Gorman
Keyword(s):  
Latent Heat ◽  
Thermal Stratification ◽  
General Circulation ◽  
Large Scale ◽  
Circulation Model ◽  
Lapse Rate ◽  
Moist Convection ◽  
Wide Range ◽  
Simulation Results ◽  
Warm Climates

Abstract Simulations with an aquaplanet general circulation model show that sensible and latent heat transport by large-scale eddies influences the extratropical thermal stratification over a wide range of climates, even in relatively warm climates with small meridional surface temperature gradients. Variations of the lapse rate toward which the parameterized moist convection in the model relaxes atmospheric temperature profiles demonstrate that the convective lapse rate only marginally affects the extratropical thermal stratification in Earth-like and colder climates. In warmer climates, the convective lapse rate does affect the extratropical thermal stratification, but the effect is still smaller than would be expected if moist convection alone controlled the thermal stratification. A theory for how large-scale eddies modify the thermal stratification of dry atmospheres is consistent with the simulation results for colder climates. For warmer and moister climates, however, theories and heuristics that have been proposed to account for the extratropical thermal stratification are not consistent with the simulation results. Theories for the extratropical thermal stratification will generally have to take transport of sensible and latent heat by large-scale eddies into account, but moist convection may only need to be taken into account regionally and in sufficiently warm climates.

scholarly journals Towards quantifying uncertainty in predictions of Amazon ‘dieback’

2008 ◽  
Vol 363 (1498) ◽  
pp. 1857-1864 ◽  
Author(s):  
Chris Huntingford ◽  
Rosie A Fisher ◽  
Lina Mercado ◽  
Ben B.B Booth ◽  
Stephen Sitch ◽  
...  
Keyword(s):  
Land Surface ◽  
General Circulation ◽  
Net Primary Productivity ◽  
Circulation Model ◽  
Light Interception ◽  
Rooting Depth ◽  
Amazon Forest ◽  
Carbon Cycle Model ◽  
Wide Range ◽  
Amazonian Rainforest

Simulations with the Hadley Centre general circulation model (HadCM3), including carbon cycle model and forced by a ‘business-as-usual’ emissions scenario, predict a rapid loss of Amazonian rainforest from the middle of this century onwards. The robustness of this projection to both uncertainty in physical climate drivers and the formulation of the land surface scheme is investigated. We analyse how the modelled vegetation cover in Amazonia responds to (i) uncertainty in the parameters specified in the atmosphere component of HadCM3 and their associated influence on predicted surface climate. We then enhance the land surface description and (ii) implement a multilayer canopy light interception model and compare with the simple ‘big-leaf’ approach used in the original simulations. Finally, (iii) we investigate the effect of changing the method of simulating vegetation dynamics from an area-based model (TRIFFID) to a more complex size- and age-structured approximation of an individual-based model (ecosystem demography). We find that the loss of Amazonian rainforest is robust across the climate uncertainty explored by perturbed physics simulations covering a wide range of global climate sensitivity. The introduction of the refined light interception model leads to an increase in simulated gross plant carbon uptake for the present day, but, with altered respiration, the net effect is a decrease in net primary productivity. However, this does not significantly affect the carbon loss from vegetation and soil as a consequence of future simulated depletion in soil moisture; the Amazon forest is still lost. The introduction of the more sophisticated dynamic vegetation model reduces but does not halt the rate of forest dieback. The potential for human-induced climate change to trigger the loss of Amazon rainforest appears robust within the context of the uncertainties explored in this paper. Some further uncertainties should be explored, particularly with respect to the representation of rooting depth.

scholarly journals Study of Climate Change using GCM Downscaling: Special Reference to Indian Subcontinent

2015 ◽  
Vol 16 ◽  
pp. 36-39
Author(s):  
Narayan P. Gautam ◽  
Manohar Arora
Keyword(s):  
Climate Change ◽  
Land Surface ◽  
General Circulation ◽  
Large Scale ◽  
Global Climate ◽  
Indian Subcontinent ◽  
Circulation Model ◽  
Physical Processes ◽  
Energy And Environment ◽  
Emerging Issues

Climate change refers to a change in a state of the climate and it is one of the emerging issues in the 21st century. General Circulation Model (GCM) represents physical processes in the atmosphere, ocean, cryosphere and land surface. It is one of the advanced tools for simulating the response of the global climate system to increasing greenhouse gas (GHG) concentrations. The application of GCMs and its downscaling outputs helps to fill up the gap existing between large-scale and local-scale variables. This study clearly showed that GCM downscaling has been increasingly applied to the study of climate change in many parts of the world including the Indian sub-continent and their results are utilized to enhance planning and management purposes. DOI: http://dx.doi.org/10.3126/hn.v16i0.12222         HYDRO Nepal  Journal of Water Energy and Environment Issue. 16, 2015, January Page: 36-39 Upload date: March 1, 2015 

scholarly journals Can We Infer Diapycnal Mixing Rates from the World Ocean Temperature–Salinity Distribution?

2016 ◽  
Vol 46 (12) ◽  
pp. 3751-3775 ◽  
Author(s):  
Olivier Arzel ◽  
Alain Colin de Verdière
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Water Mass ◽  
World Ocean ◽  
Eddy Diffusivity ◽  
Regional Variability ◽  
Diapycnal Mixing ◽  
Inverse Models ◽  
The World ◽  
The Difference

AbstractThe turbulent diapycnal mixing in the ocean is currently obtained from microstructure and finestructure measurements, dye experiments, and inverse models. This study presents a new method that infers the diapycnal mixing from low-resolution numerical calculations of the World Ocean whose temperatures and salinities are restored to the climatology. At the difference of robust general circulation ocean models, diapycnal diffusion is not prescribed but inferred. At steady state the buoyancy equation shows an equilibrium between the large-scale diapycnal advection and the restoring terms that take the place of the divergence of eddy buoyancy fluxes. The geography of the diapycnal flow reveals a strong regional variability of water mass transformations. Positive values of the diapycnal flow indicate an erosion of a deep-water mass and negative values indicate a creation. When the diapycnal flow is upward, a diffusion law can be fitted in the vertical and the diapycnal eddy diffusivity is obtained throughout the water column. The basin averages of diapycnal diffusivities are small in the first 1500 m [O(10−5) m2 s−1] and increase downward with bottom values of about 2.5 × 10−4 m2 s−1 in all ocean basins, with the exception of the Southern Ocean (50°–30°S), where they reach 12 × 10−4 m2 s−1. This study confirms the small diffusivity in the thermocline and the robustness of the higher canonical Munk’s value in the abyssal ocean. It indicates that the upward dianeutral transport in the Atlantic mostly takes place in the abyss and the upper ocean, supporting the quasi-adiabatic character of the middepth overturning.

scholarly journals Towards a regional ocean forecasting system for the IBI (Iberia-Biscay-Ireland area): developments and improvements within the ECOOP project framework

Ocean Science ◽  
2012 ◽  
Vol 8 (2) ◽  
pp. 143-159 ◽  
Author(s):  
S. Cailleau ◽  
J. Chanut ◽  
J.-M. Lellouche ◽  
B. Levier ◽  
C. Maraldi ◽  
...  
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Vertical Mixing ◽  
Circulation Model ◽  
Storm Surges ◽  
Ocean General Circulation Model ◽  
Tidal Mixing ◽  
Basin Scale ◽  
Forecasting System ◽  
Ocean Forecasting

Abstract. The regional ocean operational system remains a key element in downscaling from large scale (global or basin scale) systems to coastal ones. It enables the transition between systems in which the resolution and the resolved physics are quite different. Indeed, coastal applications need a system to predict local high frequency events (inferior to the day) such as storm surges, while deep sea applications need a system to predict large scale lower frequency ocean features. In the framework of the ECOOP project, a regional system for the Iberia-Biscay-Ireland area has been upgraded from an existing V0 version to a V2. This paper focuses on the improvements from the V1 system, for which the physics are close to a large scale basin system, to the V2 for which the physics are more adapted to shelf and coastal issues. Strong developments such as higher regional physics resolution in the NEMO Ocean General Circulation Model for tides, non linear free surface and adapted vertical mixing schemes among others have been implemented in the V2 version. Thus, regional thermal fronts due to tidal mixing now appear in the latest version solution and are quite well positioned. Moreover, simulation of the stratification in shelf areas is also improved in the V2.

HAPEX—MOBILHY: A Hydrologic Atmospheric Experiment the Study of Water Budget and Evaporation Flux at the Climatic Scale

1986 ◽  
Vol 67 (2) ◽  
pp. 138-144 ◽  
Author(s):  
Jean-Claude André ◽  
Jean-Paul Goutorbe ◽  
Alain Perrier
Keyword(s):  
Remote Sensing ◽  
Soil Moisture ◽  
Land Surface ◽  
Water Budget ◽  
General Circulation ◽  
Circulation Model ◽  
Surface Energy Budget ◽  
Surface Hydrology ◽  
Land Surface Water ◽  
Evaporation Flux

The HAPEX-MOBILHY program is aimed at studying the hydrological budget and evaporation flux at the scale of a GCM (general circulation model) grid square, i.e., 104 km2. Different surface and subsurface networks will be operated during the year 1986, to measure and monitor soil moisture, surface-energy budget and surface hydrology, as well as atmospheric properties. A two-and-a-half-month special observing period will allow for detailed measurements of atmospheric fluxes and for intensive remote sensing of surface properties using well-instrumented aircraft. The main objective of the program, for which guest investigations are strongly encouraged, is to provide a data base against which parameterization schemes for the land-surface water budget will be tested and developed.

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