scholarly journals Comparison between IPSL Venus Global Climate Model results and aerobraking data

2021 ◽  
Author(s):  
Antoine Martinez ◽  
Sébastien Lebonnois ◽  
Jean-Yves Chaufray ◽  
Ehouarn Millour ◽  
Thomas Pierron
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Upper Atmosphere ◽  
Atmospheric Parameters ◽  
Solar Angle ◽  
Recent Extension ◽  
Venus Atmosphere ◽  
Selection Of ◽  
Atmosphere Of Venus

<p align="justify"><span>For fifteen years</span><span>, a G</span><span>lobal</span><span> C</span><span>limate</span><span> Model (GCM) </span><span>ha</span><span>s </span><span>been</span><span> developed for the Venus atmosphere </span><span>at Institut Pierre-Simon Laplace (IPSL), in collaboration between LMD and LATMOS, </span><span>from the surface up to 150 km altitude. Its recent extension up to </span><span>the exobase (roughly </span><span>250 km</span><span>)</span><span> within the framework of the VCD project now allows us to simulate the Venusian upper atmosphere and the key atmospheric parameters of the aerobraking phases. The aim of this presentation is to study the evolution of the density of the Venusian upper atmosphere as a function of different parameters such as solar irradiance, </span><span>latitude, </span><span>local time and zenith solar angle (SZA), </span><span>for regions from 130 to 180 km of altitude.</span><span> We will present here several comparisons of the upper atmosphere of Venus between our model results and a selection of aerobraking data from different missions such as Venus Express, Pioneer Venus and Magellan. </span></p>

The haze of Pluto: exploring its radiative impact on the climate

2020 ◽  
Author(s):  
Tanguy Bertrand ◽  
Emmanuel Lellouch ◽  
Xi Zhang ◽  
Lora Jovanovic ◽  
Thomas Gautier ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Temperature Gradients ◽  
Upper Atmosphere ◽  
Research Association ◽  
Thermal Profile ◽  
New Horizons ◽  
Radiative Impact ◽  
Significant Temperature

<p><strong>Introduction</strong></p> <p>The thermal profile of Pluto’s atmosphere has been measured from ground-based observations and from the REX instrument on-board New Horizons [1,2]. From the surface to the top of the atmosphere, the profiles show a 3-km deep ~37 K cold layer above the N<sub>2</sub> ice-covered surface, a strong positive gradient below 50 km, warming the stratosphere up to 110 K, and a 40 K negative gradient cooling the upper atmosphere to 70 K.</p> <p><strong>Our objective is to study the radiative balance of Pluto’s atmosphere in 1D with a radiative-convective model, and in 3D with the full Pluto Global Climate Model (GCM), taking into account the radiative impact of haze particles.</strong></p> <p>We focus on three aspects of the thermal profile with the GCM: (1) It has been suggested that the organic haze has a significant radiative impact and is responsible for the cooling of the upper atmosphere [3]. However, this has not been explored yet in details in a GCM and remains to be tested against JWST observations of Pluto’s atmosphere thermal emission. (2) The depth of the near-surface cold layer in the GCM is currently only 1 km, versus 3 km in the observations [4,5]. (3) The significant temperature gradient between the equator and the north pole tentatively indicated by recent ALMA observations (PI Lellouch) is not predicted by current models, because the long radiative timescale of Pluto’s atmosphere should prevent horizontal temperature gradients. However, by radiating in the infrared, haze particles could shorten the radiative timescale and trigger significant temperature gradients.</p> <p> </p> <p><strong>The Pluto GCM</strong></p> <p>The GCM is described in detail in [4,5]. It takes into account the sublimation and condensation cycles of N<sub>2</sub>, CH<sub>4</sub>, and CO [4], their thermal and dynamical effects, the cloud formation, the vertical turbulent mixing, molecular thermal conduction, and a detailed surface thermal model with different thermal inertia for various timescales (diurnal, seasonal). It also includes a parameterization of the formation of organic haze [6].</p> <p>We use the 1D radiative-convection version of the GCM to explore the radiative impact of haze depending on the haze properties. We then use the 3D GCM to explore the effect in a climatic context, with consistent 3D predictions for haze formation and methane abundance, which are used as an input for our radiative transfer calculation.</p> <p><strong>At the conference we will present the results obtained with our model for different types of haze particles (spheres, fractal aggregates) and different datasets of laboratory-generated optical constants.</strong></p> <p><strong>We will reveal if the radiative haze can solve the three mysteries mentioned in Section 1, and how it impacts Pluto’s atmosphere dynamics.</strong></p> <p> </p> <p><strong>Acknowledgements</strong></p> <p>T.B. was supported for this research by an appointment to the National Aeronautics and Space Administration (NASA) Post-doctoral Program at the Ames Research Center administered by Universities Space Research Association (USRA) through a contract with NASA.</p> <p> </p> <p><strong>References</strong></p> <p>[1] Hinson, D. P., et al., Radio occultation measurements of Pluto’s neutral atmosphere with New Horizons, Icarus, 290, 96–111, 2017.</p> <p>[2] A. Dias-Oliveira et al., Pluto's atmosphere from stellar occultations in 2012 and 2013, ApJ 811, 53, 2015.</p> <p>[3] Zhang, X., et al, Haze heats Pluto's atmosphere yet explains its cold temperature, Nature, 2017.</p> <p>[4] Forget, F., et al., A post-new horizons global climate model of Pluto including the N<sub>2</sub>, CH<sub>4</sub> and CO cycles, Icarus, 287, 54–71, 2017.</p> <p>[5] Bertrand, T., et al., Pluto’s Beating Heart Regulates the Atmospheric Circulation: Results From High-Resolution and Multiyear Numerical Climate Simulations. JGR: Planets, 125(2), 1–24, 2020.</p> <p>[6] Bertrand, T. and Forget, F.: 3D modeling of organic haze in Pluto’s atmosphere, Icarus, 287:72, 2017.</p> <p> </p>

scholarly journals High-end climate change impact on European runoff and low flows – exploring the effects of forcing biases

2016 ◽  
Vol 20 (5) ◽  
pp. 1785-1808 ◽  
Author(s):  
Lamprini V. Papadimitriou ◽  
Aristeidis G. Koutroulis ◽  
Manolis G. Grillakis ◽  
Ioannis K. Tsanis
Keyword(s):  
Global Warming ◽  
Bias Correction ◽  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Data Set ◽  
Low Flows ◽  
The Impact ◽  
Selection Of

Abstract. Climate models project a much more substantial warming than the 2 °C target under the more probable emission scenarios, making higher-end scenarios increasingly plausible. Freshwater availability under such conditions is a key issue of concern. In this study, an ensemble of Euro-CORDEX projections under RCP8.5 is used to assess the mean and low hydrological states under +4 °C of global warming for the European region. Five major European catchments were analysed in terms of future drought climatology and the impact of +2 °C versus +4 °C global warming was investigated. The effect of bias correction of the climate model outputs and the observations used for this adjustment was also quantified. Projections indicate an intensification of the water cycle at higher levels of warming. Even for areas where the average state may not considerably be affected, low flows are expected to reduce, leading to changes in the number of dry days and thus drought climatology. The identified increasing or decreasing runoff trends are substantially intensified when moving from the +2 to the +4° of global warming. Bias correction resulted in an improved representation of the historical hydrology. It is also found that the selection of the observational data set for the application of the bias correction has an impact on the projected signal that could be of the same order of magnitude to the selection of the Global Climate Model (GCM).

High bit rate ACTS experiments for performing global science - Keck Telescope and global climate model

1996 ◽  
Author(s):  
Larry Bergman ◽  
J. Gary ◽  
Burt Edelson ◽  
Neil Helm ◽  
Judith Cohen ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Bit Rate ◽  
Global Science ◽  
High Bit Rate

scholarly journals A comparison of ship and satellite measurements of cloud properties with global climate model simulations in the southeast Pacific stratus deck

2010 ◽  
Vol 10 (14) ◽  
pp. 6527-6536 ◽  
Author(s):  
M. A. Brunke ◽  
S. P. de Szoeke ◽  
P. Zuidema ◽  
X. Zeng
Keyword(s):  
Diurnal Cycle ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Cloud Fraction ◽  
Cloud Base ◽  
Liquid Water Path ◽  
Cloud Properties ◽  
Southeast Pacific ◽  
Cloud Thickness

Abstract. Here, liquid water path (LWP), cloud fraction, cloud top height, and cloud base height retrieved by a suite of A-train satellite instruments (the CPR aboard CloudSat, CALIOP aboard CALIPSO, and MODIS aboard Aqua) are compared to ship observations from research cruises made in 2001 and 2003–2007 into the stratus/stratocumulus deck over the southeast Pacific Ocean. It is found that CloudSat radar-only LWP is generally too high over this region and the CloudSat/CALIPSO cloud bases are too low. This results in a relationship (LWP~h9) between CloudSat LWP and CALIPSO cloud thickness (h) that is very different from the adiabatic relationship (LWP~h2) from in situ observations. Such biases can be reduced if LWPs suspected to be contaminated by precipitation are eliminated, as determined by the maximum radar reflectivity Zmax>−15 dBZ in the apparent lower half of the cloud, and if cloud bases are determined based upon the adiabatically-determined cloud thickness (h~LWP1/2). Furthermore, comparing results from a global model (CAM3.1) to ship observations reveals that, while the simulated LWP is quite reasonable, the model cloud is too thick and too low, allowing the model to have LWPs that are almost independent of h. This model can also obtain a reasonable diurnal cycle in LWP and cloud fraction at a location roughly in the centre of this region (20° S, 85° W) but has an opposite diurnal cycle to those observed aboard ship at a location closer to the coast (20° S, 75° W). The diurnal cycle at the latter location is slightly improved in the newest version of the model (CAM4). However, the simulated clouds remain too thick and too low, as cloud bases are usually at or near the surface.

Two-way coupling of an ENSO model to the global climate model CLIMBER-3

2009 ◽  
Vol 29 (1) ◽  
pp. 94-101 ◽  
Author(s):  
Heiko Goelzer ◽  
Anders Levermann ◽  
Stefan Rahmstorf
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Enso Model

Downscaling of precipitation on a lake basin: evaluation of rule and decision tree induction algorithms

2012 ◽  
Vol 43 (3) ◽  
pp. 215-230 ◽  
Author(s):  
Manish Kumar Goyal ◽  
C. S. P. Ojha
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Lake Basin ◽  
Monthly Precipitation ◽  
M5 Model Tree ◽  
Reanalysis Dataset ◽  
Model Tree ◽  
Basin Scale ◽  
M5 Model

We investigate the performance of existing state-of-the-art rule induction and tree algorithms, namely Single Conjunctive Rule Learner, Decision Table, M5 Model Tree, Decision Stump and REPTree. Downscaling models are developed using these algorithms to obtain projections of mean monthly precipitation to lake-basin scale in an arid region in India. The effectiveness of these algorithms is evaluated through application to downscale the predictand for the Lake Pichola region in Rajasthan state in India, which is considered to be a climatically sensitive region. The predictor variables are extracted from (1) the National Centre for Environmental Prediction (NCEP) reanalysis dataset for the period 1948–2000 and (2) the simulations from the third-generation Canadian Coupled Global Climate Model (CGCM3) for emission scenarios A1B, A2, B1 and COMMIT for the period 2001–2100. M5 Model Tree algorithm was found to yield better performance among all other learning techniques explored in the present study. The precipitation is projected to increase in future for A2 and A1B scenarios, whereas it is least for B1 and COMMIT scenarios using predictors.

scholarly journals Sea-Breeze Dynamics and Convection Initiation: The Influence of Convective Parameterization in Weather and Climate Model Biases

2015 ◽  
Vol 28 (20) ◽  
pp. 8093-8108 ◽  
Author(s):  
Cathryn E. Birch ◽  
Malcolm J. Roberts ◽  
Luis Garcia-Carreras ◽  
Duncan Ackerley ◽  
Michael J. Reeder ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Sea Breeze ◽  
Early Morning ◽  
Sea Temperature ◽  
Convective Parameterization ◽  
Study Approach ◽  
Climate Model Simulations ◽  
Convection Initiation

Abstract There are some long-established biases in atmospheric models that originate from the representation of tropical convection. Previously, it has been difficult to separate cause and effect because errors are often the result of a number of interacting biases. Recently, researchers have gained the ability to run multiyear global climate model simulations with grid spacings small enough to switch the convective parameterization off, which permits the convection to develop explicitly. There are clear improvements to the initiation of convective storms and the diurnal cycle of rainfall in the convection-permitting simulations, which enables a new process-study approach to model bias identification. In this study, multiyear global atmosphere-only climate simulations with and without convective parameterization are undertaken with the Met Office Unified Model and are analyzed over the Maritime Continent region, where convergence from sea-breeze circulations is key for convection initiation. The analysis shows that, although the simulation with parameterized convection is able to reproduce the key rain-forming sea-breeze circulation, the parameterization is not able to respond realistically to the circulation. A feedback of errors also occurs: the convective parameterization causes rain to fall in the early morning, which cools and wets the boundary layer, reducing the land–sea temperature contrast and weakening the sea breeze. This is, however, an effect of the convective bias, rather than a cause of it. Improvements to how and when convection schemes trigger convection will improve both the timing and location of tropical rainfall and representation of sea-breeze circulations.

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