scholarly journals Idealised simulations of the deep atmosphere of hot Jupiters

2019 ◽  
Vol 632 ◽  
pp. A114 ◽  
Author(s):  
F. Sainsbury-Martinez ◽  
P. Wang ◽  
S. Fromang ◽  
P. Tremblin ◽  
T. Dubos ◽  
...  
Keyword(s):  
General Circulation ◽  
Potential Temperature ◽  
Circulation Model ◽  
Final State ◽  
Vertical Advection ◽  
Atmospheric Circulations ◽  
Hot Jupiters ◽  
Heating And Cooling ◽  
Natural Outcome

Context. The anomalously large radii of hot Jupiters has long been a mystery. However, by combining both theoretical arguments and 2D models, a recent study has suggested that the vertical advection of potential temperature leads to a hotter adiabatic temperature profile in the deep atmosphere than the profile obtained with standard 1D models. Aims. In order to confirm the viability of that scenario, we extend this investigation to 3D, time-dependent models. Methods. We use a 3D general circulation model DYNAMICO to perform a series of calculations designed to explore the formation and structure of the driving atmospheric circulations, and detail how it responds to changes in both the upper and deep atmospheric forcing. Results. In agreement with the previous, 2D study, we find that a hot adiabat is the natural outcome of the long-term evolution of the deep atmosphere. Integration times of the order of 1500 yr are needed for that adiabat to emerge from an isothermal atmosphere, explaining why it has not been found in previous hot Jupiter studies. Models initialised from a hotter deep atmosphere tend to evolve faster toward the same final state. We also find that the deep adiabat is stable against low-levels of deep heating and cooling, as long as the Newtonian cooling timescale is longer than ~3000 yr at 200 bar. Conclusions. We conclude that steady-state vertical advection of potential temperature by deep atmospheric circulations constitutes a robust mechanism to explain the inflated radii of hot Jupiters. We suggest that future models of hot Jupiters be evolved for a longer time than currently done, and when possible that models initialised with a hot deep adiabat be included. We stress that this mechanism stems from the advection of entropy by irradiation-induced mass flows and does not require a (finely tuned) dissipative process, in contrast with most previously suggested scenarios.

scholarly journals ATMOSPHERIC CIRCULATION OF HOT JUPITERS: COUPLED RADIATIVE-DYNAMICAL GENERAL CIRCULATION MODEL SIMULATIONS OF HD 189733b and HD 209458b

2009 ◽  
Vol 699 (1) ◽  
pp. 564-584 ◽  
Author(s):  
Adam P. Showman ◽  
Jonathan J. Fortney ◽  
Yuan Lian ◽  
Mark S. Marley ◽  
Richard S. Freedman ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Model Simulations ◽  
Hot Jupiters

scholarly journals A Multivariate Empirical Orthogonal Function Method to Construct Nitrate Maps in the Southern Ocean

2018 ◽  
Vol 35 (7) ◽  
pp. 1505-1519 ◽  
Author(s):  
Yu-Chiao Liang ◽  
Matthew R. Mazloff ◽  
Isabella Rosso ◽  
Shih-Wei Fang ◽  
Jin-Yi Yu
Keyword(s):  
Southern Ocean ◽  
General Circulation ◽  
Model Simulation ◽  
Potential Temperature ◽  
Circulation Model ◽  
Empirical Orthogonal Functions ◽  
Cluster Method ◽  
Sampling Strategies ◽  
Data Sampling ◽  
Mean Square Errors

AbstractThe ability to construct nitrate maps in the Southern Ocean (SO) from sparse observations is important for marine biogeochemistry research, as it offers a geographical estimate of biological productivity. The goal of this study is to infer the skill of constructed SO nitrate maps using varying data sampling strategies. The mapping method uses multivariate empirical orthogonal functions (MEOFs) constructed from nitrate, salinity, and potential temperature (N-S-T) fields from a biogeochemical general circulation model simulation Synthetic N-S-T datasets are created by sampling modeled N-S-T fields in specific regions, determined either by random selection or by selecting regions over a certain threshold of nitrate temporal variances. The first 500 MEOF modes, determined by their capability to reconstruct the original N-S-T fields, are projected onto these synthetic N-S-T data to construct time-varying nitrate maps. Normalized root-mean-square errors (NRMSEs) are calculated between the constructed nitrate maps and the original modeled fields for different sampling strategies. The sampling strategy according to nitrate variances is shown to yield maps with lower NRMSEs than mapping adopting random sampling. A k-means cluster method that considers the N-S-T combined variances to identify key regions to insert data is most effective in reducing the mapping errors. These findings are further quantified by a series of mapping error analyses that also address the significance of data sampling density. The results provide a sampling framework to prioritize the deployment of biogeochemical Argo floats for constructing nitrate maps.

scholarly journals Susceptibility of Hydropower Generation to Climate Change: Karun III Dam Case Study

Water ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 1025 ◽  
Author(s):  
Maryam Beheshti ◽  
Ali Heidari ◽  
Bahram Saghafian
Keyword(s):  
Climate Change ◽  
Power Generation ◽  
General Circulation ◽  
Average Power ◽  
Circulation Model ◽  
Precipitation Trend ◽  
Hydropower Generation ◽  
Near Future ◽  
Far Future

Climate change can cause serious problems for future hydropower plant projects and make them less economically justified. Changing precipitation patterns, rising temperatures, and abrupt snow melting affect river stream patterns and hydropower generation. Thus, study of climate change impacts during the useful life of a hydropower dam is essential and its outcome should be considered in assessing long-term dam feasibility. The aim of this research is to evaluate the impacts of climate change on future hydropower generation in the Karun-III dam located in the southwest region of Iran in two future tri-decadal periods: near (2020–2049) and far (2070–2099). Had-CM3 general circulation model predictions under A2 and B2 SRES scenarios were applied, and downscaled by a statistical downscaling model (SDSM). An artificial neural network (ANN) and HEC-ResSim reservoir model respectively simulated the rainfall–runoff process and hydropower generation. The projections showed that the Karun-III dam catchment under the two scenarios will generally become warmer and wetter with a slightly larger increase in annual precipitation in the near than the far future. Runoff followed the precipitation trend by increasing in both periods. The runoff peak also switched from April to March in both scenarios, due to higher winter precipitation, and earlier snowmelt, which was caused by temperature rise. According to both scenarios, hydropower generation increased more in the near future than in the far future. Annual average power generation increased gradually by 26.7–40.5% under A2 and by 17.4–29.3% under B2 in 2020–2049. In the far period, average power generation increased by 1.8–8.7% in A2 and by 10.5–22% under B2. In the near future, A2 showed energy deduction in the months of June and July, while B2 revealed a decrease in the months of April and June. Additionally, projections in the 2070–2099 under A2 exhibited energy reduction in the months of March through July, while B2 revealed a decrease in April through July. The framework utilized in this study can be exploited to analyze the susceptibility of hydropower production in the long term.

scholarly journals Long-term Surface Temperature (LoST) database as a complement for GCM preindustrial simulations

2019 ◽  
Vol 15 (3) ◽  
pp. 1099-1111 ◽  
Author(s):  
Francisco José Cuesta-Valero ◽  
Almudena García-García ◽  
Hugo Beltrami ◽  
Eduardo Zorita ◽  
Fernando Jaume-Santero
Keyword(s):  
Surface Temperature ◽  
General Circulation ◽  
Ground Surface ◽  
Coupled Model ◽  
Circulation Model ◽  
Research Unit ◽  
Large Spread ◽  
Intercomparison Project ◽  
Past Millennium

Abstract. Estimates of climate sensitivity from general circulation model (GCM) simulations still present a large spread despite the continued improvements in climate modeling since the 1970s. This variability is partially caused by the dependence of several long-term feedback mechanisms on the reference climate state. Indeed, state-of-the-art GCMs present a large spread of control climate states probably due to the lack of a suitable reference for constraining the climatology of preindustrial simulations. We assemble a new gridded database of long-term ground surface temperatures (LoST database) obtained from geothermal data over North America, and we explore its use as a potential reference for the evaluation of GCM preindustrial simulations. We compare the LoST database with observations from the Climate Research Unit (CRU) database, as well as with five past millennium transient climate simulations and five preindustrial control simulations from the third phase of the Paleoclimate Modelling Intercomparison Project (PMIP3) and the fifth phase of the Coupled Model Intercomparison Project (CMIP5). The database is consistent with meteorological observations as well as with both types of preindustrial simulations, which suggests that LoST temperatures can be employed as a reference to narrow down the spread of surface temperature climatologies on GCM preindustrial control and past millennium simulations.

scholarly journals Axisymmetric Constraints on Cross-Equatorial Hadley Cell Extent

2019 ◽  
Vol 76 (6) ◽  
pp. 1547-1564 ◽  
Author(s):  
Spencer A. Hill ◽  
Simona Bordoni ◽  
Jonathan L. Mitchell
Keyword(s):  
Angular Momentum ◽  
Zonal Wind ◽  
General Circulation ◽  
Potential Temperature ◽  
Circulation Model ◽  
Hadley Circulation ◽  
Hadley Cell ◽  
Equal Area ◽  
Area Model ◽  
Hadley Cells

Abstract We consider the relevance of known constraints from each of Hide’s theorem, the angular momentum–conserving (AMC) model, and the equal-area model on the extent of cross-equatorial Hadley cells. These theories respectively posit that a Hadley circulation must span all latitudes where the radiative–convective equilibrium (RCE) absolute angular momentum satisfies or or where the RCE absolute vorticity satisfies ; all latitudes where the RCE zonal wind exceeds the AMC zonal wind; and over a range such that depth-averaged potential temperature is continuous and that energy is conserved. The AMC model requires knowledge of the ascent latitude , which needs not equal the RCE forcing maximum latitude . Whatever the value of , we demonstrate that an AMC cell must extend at least as far into the winter hemisphere as the summer hemisphere. The equal-area model predicts , always placing it poleward of . As is moved poleward (at a given thermal Rossby number), the equal-area-predicted Hadley circulation becomes implausibly large, while both and become increasingly displaced poleward of the minimal cell extent based on Hide’s theorem (i.e., of supercritical forcing). In an idealized dry general circulation model, cross-equatorial Hadley cells are generated, some spanning nearly pole to pole. All homogenize angular momentum imperfectly, are roughly symmetric in extent about the equator, and appear in extent controlled by the span of supercritical forcing.

scholarly journals Sensitivity of US air quality to mid-latitude cyclone frequency and implications of 1980–2006 climate change

2008 ◽  
Vol 8 (23) ◽  
pp. 7075-7086 ◽  
Author(s):  
E. M. Leibensperger ◽  
L. J. Mickley ◽  
D. J. Jacob
Keyword(s):  
Air Quality ◽  
General Circulation ◽  
Strong Predictor ◽  
Storm Track ◽  
Circulation Model ◽  
Quality Standard ◽  
Ozone Pollution ◽  
Long Term Trend ◽  
Cyclone Frequency

Abstract. We show that the frequency of summertime mid-latitude cyclones tracking across eastern North America at 40°–50° N (the southern climatological storm track) is a strong predictor of stagnation and ozone pollution days in the eastern US. The NCEP/NCAR Reanalysis, going back to 1948, shows a significant long-term decline in the number of summertime mid-latitude cyclones in that track starting in 1980 (−0.15 a−1). The more recent but shorter NCEP/DOE Reanalysis (1979–2006) shows similar interannual variability in cyclone frequency but no significant long-term trend. Analysis of NOAA daily weather maps for 1980–2006 supports the trend detected in the NCEP/NCAR Reanalysis 1. A GISS general circulation model (GCM) simulation including historical forcing by greenhouse gases reproduces this decreasing cyclone trend starting in 1980. Such a long-term decrease in mid-latitude cyclone frequency over the 1980–2006 period may have offset by half the ozone air quality gains in the northeastern US from reductions in anthropogenic emissions. We find that if mid-latitude cyclone frequency had not declined, the northeastern US would have been largely compliant with the ozone air quality standard by 2001. Mid-latitude cyclone frequency is expected to decrease further over the coming decades in response to greenhouse warming and this will necessitate deeper emission reductions to achieve a given air quality goal.

Parameterization of PBL Processes in an Atmospheric General Circulation Model: Description and Preliminary Assessment

2009 ◽  
Vol 137 (3) ◽  
pp. 1061-1082 ◽  
Author(s):  
Celal S. Konor ◽  
Gabriel Cazes Boezio ◽  
Carlos R. Mechoso ◽  
Akio Arakawa
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Potential Temperature ◽  
Circulation Model ◽  
Surface Fluxes ◽  
Shortwave Radiation ◽  
Model Description ◽  
Atmospheric General Circulation ◽  
Seasonal And Diurnal Variations

Abstract This paper presents the basic features of a newly developed planetary boundary layer (PBL) parameterization, and the performance assessment of a version of the University of California, Los Angeles (UCLA), Atmospheric General Circulation Model (AGCM) to which the parameterization is incorporated. The UCLA AGCM traditionally uses a framework in which a sigma-type vertical coordinate for the PBL shares a coordinate surface with the free atmosphere at the PBL top. This framework facilitates an explicit representation of processes concentrated near the PBL top, which is crucially important especially for predicting PBL clouds. In the new framework, multiple layers are introduced between the PBL top and earth’s surface, allowing for predictions of the vertical profiles of potential temperature, total water mixing ratio, and horizontal winds within the PBL. The vertically integrated “bulk” turbulent kinetic energy (TKE) is also predicted for the PBL. The PBL-top mass entrainment is determined through an equation including the effects of TKE and the radiative and evaporative cooling processes concentrated near the PBL top. The surface fluxes are determined from an aerodynamic formula in which the velocity scale depends both on the square root of TKE and the grid-scale PBL velocity at the lowermost model layer. The turbulent fluxes within the PBL are determined through an approach that includes the effects of both large convective and small diffusive eddies. AGCM simulations with the new formulation of PBL are analyzed with a focus on the seasonal and diurnal variations. The simulated seasonal cycle of stratocumulus over the eastern oceans is realistic, as are the diurnal cycles of the PBL depth and precipitation over land. The simulated fluxes of latent heat, momentum, and shortwave radiation at the ocean surface and baroclinic activity in the middle latitudes show significant improvements over the previous versions of the AGCM based on the single-layer PBL.

scholarly journals TransEBM v. 1.0: description, tuning, and validation of a transient model of the Earth's energy balance in two dimensions

2021 ◽  
Vol 14 (5) ◽  
pp. 2843-2866
Author(s):  
Elisa Ziegler ◽  
Kira Rehfeld
Keyword(s):  
Energy Balance ◽  
Land Surface ◽  
General Circulation ◽  
Circulation Model ◽  
Internal Variability ◽  
Two Dimensions ◽  
Balance Model ◽  
Seasonal Temperature ◽  
Transient Model

Abstract. Modeling the long-term transient evolution of climate remains a technical and scientific challenge. However, understanding and improving modeling of the long-term behavior of the climate system increases confidence in projected changes in the mid- to long-term future. Energy balance models (EBMs) provide simplified and computationally efficient descriptions of long timescales and allow large ensemble runs by parameterizing energy fluxes. In this way, they can be used to pinpoint periods and phenomena of interest. Here, we present TransEBM, an extended version of the two-dimensional energy balance model by Zhuang et al. (2017a). Transient CO2, solar insolation, orbital configuration, fixed ice coverage, and land–sea distribution are implemented as effective radiative forcings at the land surface. We show that the model is most sensitive to changes in CO2 and ice distribution, but the obliquity and land–sea mask have significant influence on modeled temperatures as well. We tune TransEBM to reproduce the 1960–1989 CE global mean temperature and the Equator-to-pole and seasonal temperature gradients of ERA-20CM reanalysis (Hersbach et al., 2015). The resulting latitudinal and seasonal temperature distributions agree well with reanalysis and the general circulation model (GCM) HadCM3 for a simulation of the past millennium (Bühler et al., 2020). TransEBM does not represent the internal variability of the ocean–atmosphere system, but non-deterministic elements and nonlinearity can be introduced through model restarts and randomized forcing. As the model facilitates long transient simulations, we envisage its use in exploratory studies of stochastic forcing and perturbed parameterizations, thus complementing studies with comprehensive GCMs.

Trend and Variability Analysis of Sunshine Duration in Divisional Headquarters of Bangladesh

2021 ◽  
Vol 12 (1-2) ◽  
pp. 127-133
Author(s):  
MA Farukh ◽  
MA Islam ◽  
L Akter ◽  
R Khatun
Keyword(s):  
General Circulation ◽  
Sunshine Duration ◽  
Monsoon Season ◽  
Winter Season ◽  
Circulation Model ◽  
North East ◽  
Before And After ◽  
Post Monsoon Season ◽  
Sunshine Hour

In this study, Sunshine duration data of eight divisional headquarters of Bangladesh Meteorological Stations (Dhaka, Rangpur, Rajshahi, Mymensingh, Sylhet, Barishal, Khulna and Chattagram) were analyzed to evaluate the long-term changes and trends. The data used are the BMD data spanning from 1980 to 2010. The annual sunshine duration has decreased by the month of (June –September) from 1980 to 2010. Seasonal changes in sunshine duration were also analyzed where the maximum decline was found in rainy-monsoon season (June – September), the winter season (December – February), then the post-monsoon season (October – November) and the minimum in the pre-monsoon season (March – May). Analysis of observed data before and after 2000 represents the sunshine durations have decreasing trends in all divisional headquarters of Bangladesh except Chattagram station during the month of (January – December). General Circulation Model (GCM) defined that the maximum sunshine hour was decline north-east and south-west in all divisional headquarters of Bangladesh during the month of (June – September) and the minimum sunshine hour was decline in eastern part of the country during the month of (March – May). Environ. Sci. & Natural Resources, 12(1&2): 127-133, 2019

Sign in / Sign up

Export Citation Format

Share Document