The coupling of winds, aerosols and chemistry in Titan's atmosphere

2008 ◽  
Vol 367 (1889) ◽  
pp. 665-682 ◽  
Author(s):  
Sebastien Lebonnois ◽  
Pascal Rannou ◽  
Frederic Hourdin
Keyword(s):  
Complex System ◽  
Climate Model ◽  
Global Climate ◽  
Thermal Structure ◽  
Global Climate Model ◽  
Lower Atmosphere ◽  
Strongly Coupled ◽  
Atmospheric Structure ◽  
The Past ◽  
Production Mechanisms

The atmosphere of Titan is a complex system, where thermal structure, radiative transfer, dynamics, microphysics and photochemistry are strongly coupled together. The global climate model developed over the past 15 years at the Pierre-Simon Laplace Institute has been exploring these different couplings, and has demonstrated how they can help to interpret the observed atmospheric structure of Titan's lower atmosphere (mainly in the stratosphere and troposphere). This review discusses these interactions, and our current understanding of their role in the context of this model, but also of other available works. The recent Cassini results, and the importance of the production mechanisms for Titan's haze, have put forward the need to explore the mesosphere and the couplings between upper and lower atmosphere, as well as the current limits of available models.

scholarly journals Intraseasonal versus Interannual Measures of Land–Atmosphere Coupling Strength in a Global Climate Model: GLACE-1 versus GLACE-CMIP5 Experiments in ACCESS1.3b

2015 ◽  
Vol 16 (5) ◽  
pp. 2276-2295 ◽  
Author(s):  
Ruth Lorenz ◽  
Andrew J. Pitman ◽  
Annette L. Hirsch ◽  
Jhan Srbinovsky
Keyword(s):  
Coupling Strength ◽  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Climate Extremes ◽  
Care Needs ◽  
Similar Measure ◽  
Single Measure ◽  
Strongly Coupled

Abstract Land–atmosphere coupling can strongly affect climate and climate extremes. Estimates of land–atmosphere coupling vary considerably between climate models, between different measures used to define coupling, and between the present and the future. The Australian Community Climate and Earth-System Simulator, version 1.3b (ACCESS1.3b), is used to derive and examine previously used measures of coupling strength. These include the GLACE-1 coupling measure derived on seasonal time scales; a similar measure defined using multiyear simulations; and four other measures of different complexity and data requirements, including measures that can be derived from standard model runs and observations. The ACCESS1.3b land–atmosphere coupling strength is comparable to other climate models. The coupling strength in the Southern Hemisphere summer is larger compared to the Northern Hemisphere summer and is dominated by a strong signal in the tropics and subtropics. The land–atmosphere coupling measures agree on the location of very strong land–atmosphere coupling but show differences in the spatial extent of these regions. However, the investigated measures show disagreement in weaker coupled regions, and some regions are only identified by a single measure as strongly coupled. In future projections the soil moisture trend is crucial in generating regions of strong land–atmosphere coupling, and the results suggest an expansion of coupling “hot spots.” It is concluded that great care needs to be taken in using different measures of coupling strength and shown that several measures that can be easily derived lead to inconsistent conclusions with more computationally expensive measures designed to measure coupling strength.

scholarly journals A stable Atlantic Meridional Overturning Circulation in a changing North Atlantic Ocean since the 1990s

2020 ◽  
Vol 6 (48) ◽  
pp. eabc7836
Author(s):  
Yao Fu ◽  
Feili Li ◽  
Johannes Karstensen ◽  
Chunzai Wang
Keyword(s):  
North Atlantic ◽  
Climate Model ◽  
North Atlantic Ocean ◽  
Global Climate ◽  
Global Climate Model ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Overturning Circulation ◽  
The Past ◽  
Meridional Overturning

The Atlantic Meridional Overturning Circulation (AMOC) is crucially important to global climate. Model simulations suggest that the AMOC may have been weakening over decades. However, existing array-based AMOC observations are not long enough to capture multidecadal changes. Here, we use repeated hydrographic sections in the subtropical and subpolar North Atlantic, combined with an inverse model constrained using satellite altimetry, to jointly analyze AMOC and hydrographic changes over the past three decades. We show that the AMOC state in the past decade is not distinctly different from that in the 1990s in the North Atlantic, with a remarkably stable partition of the subpolar overturning occurring prominently in the eastern basins rather than in the Labrador Sea. In contrast, profound hydrographic and oxygen changes, particularly in the subpolar North Atlantic, are observed over the same period, suggesting a much higher decoupling between the AMOC and ocean interior property fields than previously thought.

scholarly journals What do moisture recycling estimates tell us? Exploring the extreme case of non-evaporating continents

2011 ◽  
Vol 15 (10) ◽  
pp. 3217-3235 ◽  
Author(s):  
H. F. Goessling ◽  
C. H. Reick
Keyword(s):  
Atmospheric Circulation ◽  
Climate Model ◽  
Global Climate ◽  
Thermal Structure ◽  
Global Climate Model ◽  
Extreme Case ◽  
Active Role ◽  
Large Spatial Scale ◽  
Moisture Recycling ◽  
Local Coupling

Abstract. Moisture recycling estimates are diagnostic measures that could ideally be used to deduce the response of precipitation to modified land-evaporation. Recycling estimates are based on moisture-budget considerations in which water is treated as a passive tracer. But in reality water is a thermodynamically active component of the atmosphere. Accordingly, recycling estimates are applicable to deduce the response to a perturbation only if other mechanisms by which evaporation affects climate do not dominate the response – a condition that has not received sufficient attention in the literature. In our analysis of what moisture recycling estimates tell us, we discuss two such additional mechanisms that result from water's active role. These are (I) local coupling, by which precipitation is affected locally via the thermal structure of the atmosphere, and (II) the atmospheric circulation, by which precipitation is affected on a large spatial scale. We perform two global climate model experiments: One with and another without continental evaporation. By this extreme perturbation we test the predictive utility of a certain type of recycling measure, the "continental recycling ratio". Moreover, by such a strong perturbation the whole spectrum of possible responses shows up simultaneously, giving us the opportunity to discuss all concurrent mechanisms jointly. The response to this extreme perturbation largely disagrees with the hypothesis that moisture recycling is the dominant mechanism. Instead, most of the response can be attributed to changes in the atmospheric circulation, while the contributions to the response by moisture recycling as well as local coupling, though noticeable, are smaller. By our case study it is not possible to give a general answer to the question posed in the title, but it demonstrates that recycling estimates do not necessarily mirror the consequences of land-use change for precipitation.

scholarly journals Global aridity synthesis for the last 60 000 years

2019 ◽  
Author(s):  
Florian Fuhrmann ◽  
Benedikt Diensberg ◽  
Xun Gong ◽  
Gerrit Lohmann ◽  
Frank Sirocko
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Sediment Cores ◽  
Growth Phases ◽  
Regional Effects ◽  
The Past ◽  
Dating Methods ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. A compilation of published literature on the dust content in terrestrial and marine sediment cores are synchronised on the basis of pollen data and speleothem growth phases within GICC05 age constrain. Based on that, aridity patterns for ten key areas in the global climate system are reconstructed over the past 60 000 years. These records have different time resolutions and rely on different dating methods, thus of various types of stratigraphy. Nevertheless, all regions show humid conditions during the early MIS3 and early Holocene, but not always of the same timing. Such discrepancies have been interpreted as regional effects while also due to stratigraphical uncertainties. In comparison, the MIS2 interval becomes arid in all northern hemisphere records, but the peak arid conditions of the Last Glacial Maximum (LGM) differ in duration and intensity among regions. In addition, we also make comparisons between the aridity synthesis to modelling results using a Global Climate Model (GCM). Indeed, both lines of evidence show great agreement for the Holocene, LGM and for the late MIS intervals.

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
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