Explanation for the increase in high altitude water on Mars observed by NOMAD during the 2018 global dust storm

Using the GEM-Mars three-dimensional general circulation model (GCM), we examine the mechanism responsible for the enhancement of water vapour in the upper atmosphere as measured by the Nadir and Occultation for MArs Discovery (NOMAD) instrument onboard ExoMars Trace Gas Orbiter (TGO) during the 2018 global dust storm on Mars.Experiments with different prescribed vertical profiles of dust show that when more dust is present higher in the atmosphere, the temperature increases and the amount of water ascending over the tropics is not limited by saturation until reaching heights of 70-100 km. The warmer temperatures allow more water to ascend to the mesosphere. The simulation of enhanced high-altitude water abundances is very sensitive to the vertical distribution of the dust prescribed in the model.The GEM-Mars model includes gas-phase photochemistry, and these simulations show how the increased water vapour over the 40-100 km altitude range results in the production of high-altitude atomic hydrogen which can be linked to atmospheric escape.

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Transient teleconnection event at the onset of a planet-encircling dust storm on Mars

Annales Geophysicae ◽

10.5194/angeo-27-3663-2009 ◽

2009 ◽

Vol 27 (9) ◽

pp. 3663-3676 ◽

Cited By ~ 13

Author(s):

O. Martínez-Alvarado ◽

L. Montabone ◽

S. R. Lewis ◽

I. M. Moroz ◽

P. L. Read

Keyword(s):

Dust Storm ◽

General Circulation ◽

Thermal Emission ◽

Three Dimensional ◽

Circulation Model ◽

Empirical Orthogonal Functions ◽

State Variables ◽

Orthogonal Functions ◽

Teleconnection Patterns ◽

Pressure Surface

Abstract. We use proper orthogonal decomposition (POD) to study a transient teleconnection event at the onset of the 2001 planet-encircling dust storm on Mars, in terms of empirical orthogonal functions (EOFs). There are several differences between this and previous studies of atmospheric events using EOFs. First, instead of using a single variable such as surface pressure or geopotential height on a given pressure surface, we use a dataset describing the evolution in time of global and fully three-dimensional atmospheric fields such as horizontal velocity and temperature. These fields are produced by assimilating Thermal Emission Spectrometer observations from NASA's Mars Global Surveyor spacecraft into a Mars general circulation model. We use total atmospheric energy (TE) as a physically meaningful quantity which weights the state variables. Second, instead of adopting the EOFs to define teleconnection patterns as planetary-scale correlations that explain a large portion of long time-scale variability, we use EOFs to understand transient processes due to localised heating perturbations that have implications for the atmospheric circulation over distant regions. The localised perturbation is given by anomalous heating due to the enhanced presence of dust around the northern edge of the Hellas Planitia basin on Mars. We show that the localised disturbance is seemingly restricted to a small number (a few tens) of EOFs. These can be classified as low-order, transitional, or high-order EOFs according to the TE amount they explain throughout the event. Despite the global character of the EOFs, they show the capability of accounting for the localised effects of the perturbation via the presence of specific centres of action. We finally discuss possible applications for the study of terrestrial phenomena with similar characteristics.

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On the response of a three-dimensional general circulation model to imposed changes in the ozone distribution

Journal of Geophysical Research Atmospheres ◽

10.1029/97jd00529 ◽

1997 ◽

Vol 102 (D11) ◽

pp. 13051-13077 ◽

Cited By ~ 21

Author(s):

B. Christiansen ◽

A. Guldberg ◽

A. W. Hansen ◽

L. P. Riishøjgaard

Keyword(s):

General Circulation Model ◽

General Circulation ◽

Three Dimensional ◽

Circulation Model ◽

Ozone Distribution

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Simulation of the isotopic composition of stratospheric water vapour – Part 1: Description and evaluation of the EMAC model

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-5537-2015 ◽

2015 ◽

Vol 15 (10) ◽

pp. 5537-5555 ◽

Cited By ~ 8

Author(s):

R. Eichinger ◽

P. Jöckel ◽

S. Brinkop ◽

M. Werner ◽

S. Lossow

Keyword(s):

Isotopic Composition ◽

Water Vapour ◽

General Circulation ◽

Climate Model ◽

Hydrological Cycle ◽

Circulation Model ◽

Isotope Ratios ◽

Physical Fractionation ◽

Water Isotopologues ◽

Stratospheric Water Vapour

Abstract. This modelling study aims at an improved understanding of the processes that determine the water vapour budget in the stratosphere by means of the investigation of water isotope ratios. An additional (and separate from the actual) hydrological cycle has been introduced into the chemistry–climate model EMAC, including the water isotopologues HDO and H218O and their physical fractionation processes. Additionally an explicit computation of the contribution of methane oxidation to H2O and HDO has been incorporated. The model expansions allow detailed analyses of water vapour and its isotope ratio with respect to deuterium throughout the stratosphere and in the transition region to the troposphere. In order to assure the correct representation of the water isotopologues in the model's hydrological cycle, the expanded system has been evaluated in several steps. The physical fractionation effects have been evaluated by comparison of the simulated isotopic composition of precipitation with measurements from a ground-based network (GNIP) and with the results from the isotopologue-enabled general circulation model ECHAM5-wiso. The model's representation of the chemical HDO precursor CH3D in the stratosphere has been confirmed by a comparison with chemical transport models (1-D, CHEM2D) and measurements from radiosonde flights. Finally, the simulated stratospheric HDO and the isotopic composition of water vapour have been evaluated, with respect to retrievals from three different satellite instruments (MIPAS, ACE-FTS, SMR). Discrepancies in stratospheric water vapour isotope ratios between two of the three satellite retrievals can now partly be explained.

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Operational ocean models in the Adriatic Sea: a skill assessment

Ocean Science ◽

10.5194/os-4-61-2008 ◽

2008 ◽

Vol 4 (1) ◽

pp. 61-71 ◽

Cited By ~ 25

Author(s):

J. Chiggiato ◽

P. Oddo

Keyword(s):

General Circulation ◽

Mean Squared Error ◽

Three Dimensional ◽

Circulation Model ◽

Remote Sensing Data ◽

Skill Assessment ◽

Regional Models ◽

Operational Systems ◽

Forecasting System ◽

The Mediterranean

Abstract. In the framework of the Mediterranean Forecasting System (MFS) project, the performance of regional numerical ocean forecasting systems is assessed by means of model-model and model-data comparison. Three different operational systems considered in this study are: the Adriatic REGional Model (AREG); the Adriatic Regional Ocean Modelling System (AdriaROMS) and the Mediterranean Forecasting System General Circulation Model (MFS-GCM). AREG and AdriaROMS are regional implementations (with some dedicated variations) of POM and ROMS, respectively, while MFS-GCM is an OPA based system. The assessment is done through standard scores. In situ and remote sensing data are used to evaluate the system performance. In particular, a set of CTD measurements collected in the whole western Adriatic during January 2006 and one year of satellite derived sea surface temperature measurements (SST) allow to asses a full three-dimensional picture of the operational forecasting systems quality during January 2006 and to draw some preliminary considerations on the temporal fluctuation of scores estimated on surface quantities between summer 2005 and summer 2006. The regional systems share a negative bias in simulated temperature and salinity. Nonetheless, they outperform the MFS-GCM in the shallowest locations. Results on amplitude and phase errors are improved in areas shallower than 50 m, while degraded in deeper locations, where major models deficiencies are related to vertical mixing overestimation. In a basin-wide overview, the two regional models show differences in the local displacement of errors. In addition, in locations where the regional models are mutually correlated, the aggregated mean squared error was found to be smaller, that is a useful outcome of having several operational systems in the same region.

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A Tropospheric Emission Spectrometer HDO/H2O retrieval simulator for climate models

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-13827-2012 ◽

2012 ◽

Vol 12 (6) ◽

pp. 13827-13880

Author(s):

R. D. Field ◽

C. Risi ◽

G. A. Schmidt ◽

J. Worden ◽

A. Voulgarakis ◽

...

Keyword(s):

Time Scales ◽

General Circulation ◽

Climate Models ◽

Circulation Model ◽

Satellite Measurement ◽

Climate Simulations ◽

Accurate Comparison ◽

Free Running ◽

The Tropics ◽

Short Time

Abstract. Retrievals of the isotopic composition of water vapor from the Aura Tropospheric Emission Spectrometer (TES) have unique value in constraining moist processes in climate models. Accurate comparison between simulated and retrieved values requires that model profiles that would be poorly retrieved are excluded, and that an instrument operator be applied to the remaining profiles. Typically, this is done by sampling model output at satellite measurement points and using the quality flags and averaging kernels from individual retrievals at specific places and times. This approach is not reliable when the modeled meteorological conditions influencing retrieval sensitivity are different from those observed by the instrument at short time scales, which will be the case for free-running climate simulations. In this study, we describe an alternative, "categorical" approach to applying the instrument operator, implemented within the NASA GISS ModelE general circulation model. Retrieval quality and averaging kernel structure are predicted empirically from model conditions, rather than obtained from collocated satellite observations. This approach can be used for arbitrary model configurations, and requires no agreement between satellite-retrieved and modeled meteorology at short time scales. To test this approach, nudged simulations were conducted using both the retrieval-based and categorical operators. Cloud cover, surface temperature and free-tropospheric moisture content were the most important predictors of retrieval quality and averaging kernel structure. There was good agreement between the δD fields after applying the retrieval-based and more detailed categorical operators, with increases of up to 30‰ over the ocean and decreases of up to 40‰ over land relative to the raw model fields. The categorical operator performed better over the ocean than over land, and requires further refinement for use outside of the tropics. After applying the TES operator, ModelE had δD biases of −8‰ over ocean and −34‰ over land compared to TES δD, which were less than the biases using raw modeled δD fields.

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Zonal Wave 3 Pattern in the Southern Hemisphere generated by tropical convection

10.21203/rs.3.rs-320008/v1 ◽

2021 ◽

Author(s):

Rishav Goyal ◽

Martin Jucker ◽

Alex Sen Gupta ◽

Harry Hendon ◽

Matthew England

Keyword(s):

Sea Ice ◽

Atmospheric Circulation ◽

Southern Hemisphere ◽

Ocean Circulation ◽

General Circulation ◽

Deep Convection ◽

Circulation Model ◽

Hadley Cell ◽

Wave Source ◽

The Tropics

Abstract A distinctive feature of the Southern Hemisphere (SH) extratropical atmospheric circulation is the quasi-stationary zonal wave 3 (ZW3) pattern, characterized by three high and three low-pressure centers around the SH extratropics. This feature is present in both the mean atmospheric circulation and its variability on daily, seasonal and interannual timescales. While the ZW3 pattern has significant impacts on meridional heat transport and Antarctic sea ice extent, the reason for its existence remains uncertain, although it has long been assumed to be linked to the existence of three major land masses in the SH extratropics. Here we use an atmospheric general circulation model to show that the stationery ZW3 pattern is instead driven by zonal asymmetric deep atmospheric convection in the tropics, with little to no role played by the orography or land masses in the extratropics. Localized regions of deep convection in the tropics form a local Hadley cell which in turn creates a wave source in the subtropics that excites a poleward and eastward propagating wave train which forms stationary waves in the SH high latitudes. Our findings suggest that changes in tropical deep convection, either due to natural variability or climate change, will impact the zonal wave 3 pattern, with implications for Southern Hemisphere climate, ocean circulation, and sea-ice.

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The Freshening of Surface Waters in High Latitudes: Effects on the Thermohaline and Wind-Driven Circulations

Journal of Physical Oceanography ◽

10.1175/jpo3033.1 ◽

2007 ◽

Vol 37 (4) ◽

pp. 896-907 ◽

Cited By ~ 28

Author(s):

Alexey Fedorov ◽

Marcelo Barreiro ◽

Giulio Boccaletti ◽

Ronald Pacanowski ◽

S. George Philander

Keyword(s):

Surface Waters ◽

General Circulation ◽

Thermohaline Circulation ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Critical Parameters ◽

High Latitudes ◽

Oceanic Circulation ◽

Meridional Overturning ◽

The Tropics

Abstract The impacts of a freshening of surface waters in high latitudes on the deep, slow, thermohaline circulation have received enormous attention, especially the possibility of a shutdown in the meridional overturning that involves sinking of surface waters in the northern Atlantic Ocean. A recent study by Fedorov et al. has drawn attention to the effects of a freshening on the other main component of the oceanic circulation—the swift, shallow, wind-driven circulation that varies on decadal time scales and is closely associated with the ventilated thermocline. That circulation too involves meridional overturning, but its variations and critical transitions affect mainly the Tropics. A surface freshening in mid- to high latitudes can deepen the equatorial thermocline to such a degree that temperatures along the equator become as warm in the eastern part of the basin as they are in the west, the tropical zonal sea surface temperature gradient virtually disappears, and permanently warm conditions prevail in the Tropics. In a model that has both the wind-driven and thermohaline components of the circulation, which factors determine the relative effects of a freshening on the two components and its impact on climate? Studies with an idealized ocean general circulation model find that vertical diffusivity is one of the critical parameters that affect the relative strength of the two circulation components and hence their response to a freshening. The spatial structure of the freshening and imposed meridional temperature gradients are other important factors.

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