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

O Martínez-Alvarado,I M Moroz,L Montabone,P L Read,S R Lewis

doi:10.5194/angeo-27-3663-2009

O Martínez-Alvarado, I M Moroz + Show 3 more

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https://doi.org/10.5194/angeo-27-3663-2009

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Abstract

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.

Highlights

Dust is an atmospheric component that plays a more important role in the Martian climate than in that of the present day Earth
The objective of this paper is to extend the use of proper orthogonal decomposition (POD) to characterise a transient teleconnection event during the initial stage of the 2001 planet-encircling dust storm on Mars (Cantor, 2007; Montabone et al, 2008), which occurred at a time scale in the order of a few sols (1 sol=1 Martian day 1 terrestrial day+40 min)
The analysis of the data has been carried out using a combination of a total atmospheric energy (TE)-based proper orthogonal decomposition (POD) (Achatz and Opsteegh, 2003) and spatio-temporal short-time Fourier analysis (STFA), in a similar way to that described in Martınez-Alvarado et al (2009)

Summary

Introduction

Dust is an atmospheric component that plays a more important role in the Martian climate than in that of the present day Earth. One of the most striking features of the Martian atmosphere is its capacity to develop and sustain dust storms that virtually cover the whole planet, a phenomenon known as “planet-encircling dust storm”. The processes that start, sustain and cause a dust storm to decay have been subject to extensive studies involving observations (Smith et al, 2002; Strausberg et al, 2005; Cantor, 2007), Mars general circulation models (MGCMs) (Newman et al, 2002a,b; Toigo et al, 2002; Basu et al, 2006), and data assimilation (Lewis and Barker, 2005; Montabone et al, 2005, 2007). Improving our capability to forecast these phenomena is vital for populations living in desert areas of our planet, as well as for aiding the safe landing of spacecraft on Mars

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