Dust storms originating in the northern hemisphere during the third mapping year of Mars Global Surveyor

Icarus ◽  
2007 ◽  
Vol 189 (2) ◽  
pp. 325-343 ◽  
Author(s):  
H WANG
Keyword(s):  
Northern Hemisphere ◽  
Dust Storms ◽  
Mars Global Surveyor ◽  
The Third

scholarly journals Climatological Features of Cutoff Low Systems in the Northern Hemisphere

2005 ◽  
Vol 18 (16) ◽  
pp. 3085-3103 ◽  
Author(s):  
Raquel Nieto ◽  
Luis Gimeno ◽  
Laura de la Torre ◽  
Pedro Ribera ◽  
David Gallego ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Atlantic Coast ◽  
Northern China ◽  
Bimodal Distribution ◽  
Northwestern Pacific ◽  
Subsequent Paper ◽  
Equivalent Thickness ◽  
Thermal Front ◽  
The Third ◽  
Cutoff Low

Abstract This study presents the first multidecadal climatology of cutoff low systems in the Northern Hemisphere. The climatology was constructed by using 41 yr (1958–98) of NCEP–NCAR reanalysis data and identifying cutoff lows by means of an objective method based on imposing the three main physical characteristics of the conceptual model of cutoff low (the 200-hPa geopotential minimum, cutoff circulation, and the specific structure of both equivalent thickness and thermal front parameter fields). Several results were confirmed and climatologically validated: 1) the existence of three preferred areas of cutoff low occurrence (the first one extends through southern Europe and the eastern Atlantic coast, the second one is the eastern North Pacific, and the third one is the northern China–Siberian region extending to the northwestern Pacific coast; the European area is the most favored region); 2) the known seasonal cycle, with cutoff lows forming much more frequently in summer than in winter; 3) the short lifetime of cutoff lows, most cutoff lows lasted 2–3 days and very few lasted more than 5 days; and 4) the mobility of the system, with few cutoff lows being stationary. Furthermore, the long study period has made it possible (i) to find a bimodal distribution in the geographical density of cutoff lows for the European sector in all the seasons (with the exception of winter), a summer displacement to the ocean in the American region, and a summer extension to the continent in the Asian region, and (ii) to detect northward and westward motion especially in the transitions from the second to third day of occurrence and from the third to fourth day of occurrence. The long-term cutoff low database built in this study is appropriate to study the interannual variability of cutoff low occurrence and the links between cutoff lows and jet stream systems, blocking, or major modes of climate variability as well as the global importance of cutoff low in the stratosphere–troposphere exchange mechanism, which will be the focus of a subsequent paper.

Micro-Dependency: The Cuban Factor in Southern Africa

1981 ◽  
Vol 37 (3) ◽  
pp. 329-345
Author(s):  
Ali A. Mazrui
Keyword(s):  
Northern Hemisphere ◽  
Third World ◽  
Raw Materials ◽  
West African ◽  
African Countries ◽  
The Third ◽  
Industrialized Nations ◽  
The World ◽  
Gulf States ◽  
The Third World

We accept the proposition that the worst kind of dependency lies in North-South interaction. But emphasizing this dimension should not go to the extent of ignoring other dimensions. It is simply not true that all forms of international dependency concern interactions between the Northern Hemisphere and the South, or between industrialism and sources of raw materials. There are important forms of dependency among industrialized nations themselves. Increasingly, there are also forms of dependency between one country in the Third World and another; or between one region of the Third World and another. Dependency is a form of political castration. For the purposes of this essay, dependency between one country in the Northern Hemisphere and another or between one industrialized state and another, is categorized as macro-dependency. This involves variations in power within the upper stratum of the world system. Macro-dependency is thus upper-horizontal, involving variations in affluence among the affluent, or degree of might among the mighty. Micro-dependency for our purposes here concerns variations of technical development among the under-developed, or relative influence among the weak, or degrees of power among those that are basically exploited. The dependency of some West African countries upon Nigeria, or of some of the Gulf States upon Iran or Saudi Arabia, are cases of micro-dependency. We shall return to this level more fully later, but let us first begin with the phenomenon of macro-dependency.

scholarly journals Textured Dust Storm Activity in Northeast Amazonis–Southwest Arcadia, Mars: Phenomenology and Dynamical Interpretation

2017 ◽  
Vol 74 (4) ◽  
pp. 1011-1037 ◽  
Author(s):  
N. G. Heavens
Keyword(s):  
Dust Storm ◽  
Deep Convection ◽  
Dust Storms ◽  
Limited Area ◽  
Mars Global Surveyor ◽  
Storm Activity ◽  
Structure And Dynamics ◽  
Local Dust ◽  
Visible Imagery ◽  
Meteorological Phenomenon

Abstract Dust storms are Mars’s most notable meteorological phenomenon, but many aspects of their structure and dynamics remain mysterious. The cloud-top appearance of dust storms in visible imagery varies on a continuum between diffuse/hazy and textured. Textured storms contain cellular structure and/or banding, which is thought to indicate active lifting within the storm. Some textured dust storms may contain the deep convection that generates the detached dust layers observed high in Mars’s atmosphere. This study focuses on textured local dust storms in a limited area within Northeast (NE) Amazonis and Southwest (SW) Arcadia Planitiae (25°–40°N, 155°–165°W) using collocated observations by instruments on board the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) satellites. In northern fall and winter, this area frequently experiences dust storms with a previously unreported ruffled texture that resembles wide, mixed-layer rolls in Earth’s atmosphere, a resemblance that is supported by high-resolution active sounding and passive radiometry in both the near- and thermal infrared. These storms are mostly confined within the atmospheric boundary layer and are rarely sources of detached dust layers. The climatology and structure of these storms are thus consistent with an underlying driver of cold-air-advection events related to the passage of strong baroclinic waves. While the properties of the studied region may be ideal for detecting these structures and processes, the dynamics here are likely relevant to dust storm activity elsewhere on Mars.

scholarly journals Detection of Martian Dust Storms Using Mask-Regional Convolutional Neural Networks

2021 ◽  
Author(s):  
Rasha Alshehhi ◽  
Claus Gebhardt
Keyword(s):  
General Circulation ◽  
Detection Method ◽  
Ground Truth ◽  
Martian Atmosphere ◽  
Dust Storms ◽  
Mars Global Surveyor ◽  
Regional Network ◽  
Average Precision ◽  
Atmospheric General Circulation ◽  
Human Exploration

Abstract Martian dust plays a crucial role in the meteorology and climate of the Martian atmosphere. It heats the atmosphere, enhances the atmospheric general circulation, and affects spacecraft instruments and operations. Compliant with that, studying dust is also essential for future human exploration. In this work, we present a method for the deep-learning-based detection of the areal extent of dust storms in Mars satellite imagery. We use a mask regional convolutional neural network (R-CNN), consisting of a regional-proposal network (RPN) and a mask network. We apply the detection method to Mars Daily Global Maps (MDGMs) of the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC). We use center coordinates of dust storms from the eight-year Mars Dust Activity Database (MDAD) as ground-truth to train and validate the method. The performance of the regional network is evaluated by the average precision score with 50% overlap (mAP50), which is around 62.1%.

Primordial Climate

2012 ◽  
Author(s):  
Jan Zalasiewicz ◽  
Mark Williams
Keyword(s):  
Solar Wind ◽  
Mass Extinction ◽  
Homo Sapiens ◽  
Dust Storms ◽  
Running Water ◽  
Ice Caps ◽  
The Third ◽  
The Earth ◽  
Just Right

We are lucky, on Earth. We are lucky because we—as complex and self-aware organisms—are here. We are sustained, given air to breathe, and water, and food, by a very ancient planet: a planet past its midpoint, a planet that is nearer death than birth. Our species is a latecomer. It took some three billion years to bridge the gap from a single-celled organism (originating in this planet’s youth) to a multicellular one, and then a little over half a billion more to arrive at the diversity of species on Earth today, including Homo sapiens . In all this time, the chain of life has remained unbroken. The Earth has been consistently habitable, with an atmosphere, and land, and oceans. Since life began, our planet has never been truly deep-frozen, nor have the oceans boiled away. The Earth is the Goldilocks planet. One recalls, here, the children’s story, where the young heroine of that name walks into the house of the three bears, and in their absence tries out successively their bowls of porridge, their chairs, and their beds. Each time the first and second choices are too hot or cold, large or small, hard or soft—and the third choice is just right . The Earth has been, so far and all in all, just right for life: not just right at any one time, but continuously so for three billion years. There have, though, been some close calls: times of mass extinction. But, life has always clung on to bloom once more. That makes the Earth’s history more remarkable than any children’s story. Other planets have not been so lucky. Mars seems to have been a planet with an appreciable atmosphere, and—at least intermittently—running water over its surface, and may even have begun to incubate life. But the atmosphere was stripped away by the solar wind. Its early lakes and rivers became acid, charged with sulphates. Then, most of the water evaporated and was carried off into space; what little was left became locked away as permafrost and in thin ice-caps. Mars does have weather, including spectacular, planet-wide dust-storms.

scholarly journals Simultaneous tracking of reconnected flux tubes: Cluster and conjugate SuperDARN observations on 1 April 2004

2008 ◽  
Vol 26 (6) ◽  
pp. 1545-1557 ◽  
Author(s):  
Q.-H. Zhang ◽  
R. Y. Liu ◽  
M. W. Dunlop ◽  
J. Y. Huang ◽  
H. Q. Hu ◽  
...  
Keyword(s):  
Response Time ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Large Scale ◽  
Global Flow ◽  
Local Response ◽  
Polar Cap ◽  
Flux Tubes ◽  
North West ◽  
The Third

Abstract. While the Cluster spacecraft were located near the high-latitude magnetopause, between 11:30–13:00 UT on 1 April 2004, a series of medium to large scale (40 nT, 0.6–1.2 Re) FTEs were observed. During this pass, simultaneous and conjugated SuperDARN measurements are available that show a global flow pattern which is consistent with the expected (mapped) north-west motion of (predominantly sub-solar) reconnected, magnetic flux at the magnetopause. We focus on analysing the local response of three FTEs, tracking their magnetopause motion via the four-spacecraft measurements together with their corresponding ground mapped motions. For two of these FTEs, where the tracking is strongly coordinated with the ionospheric flow at each footprint of the implied flux tubes in the Northern Hemisphere, conditions corresponded to stable, increasing (>100°) clock angle, while the third event, where the correspondence is less strong, coincided with low (<100°) clock angle. Flux tube motion, both measured and modeled from the inferred X-line, qualitatively matches the clear velocity enhancements in ionospheric convections with northward and westward flow at each location in the Northern Hemisphere, measured simultaneously by SuperDARN, and also roughly matches the observed, south-eastward ionospheric flow in the Southern Hemisphere at the time of these events. The time periods of these velocity enhancements infer that the evolution time of the FTEs is about 4–6 min from its origin on magnetopause to its addition to the polar cap. However, the ionospheric response time in the Southern Hemisphere might be 2 min longer for the 12:31 UT FTE (and 6 min longer for the 12:51 UT FTE) than the response time in the Northern Hemisphere.

scholarly journals Duplicity among the Cepheids in the Northern Hemisphere

1985 ◽  
Vol 82 ◽  
pp. 75-78
Author(s):  
G. Szabados
Keyword(s):  
Lower Limit ◽  
Northern Hemisphere ◽  
Stellar Evolution ◽  
Physical Parameters ◽  
Direct Information ◽  
Individual Stars ◽  
The Third ◽  
Cepheid Variables ◽  
Points Of View

Cepheid variables in binaries are important from various points of view. These objects can in some cases provide direct information about the physical parameters of the system, can be used as tracers of stellar evolution, and the effect of the companions may influence the form of various relations (e.g. P-L-C, P-R) derived for Cepheids. While the first two advantages mentioned concern individual stars, the third involves the question of the frequency of binaries among the Cepheids. Systematic searches for binaries containing this kind of variable resulted in increasingly higher frequency of incidence: 2% (Abt 1959), 15% (Lloyd Evans 1968), >20% (Madore 1977), 25% (Pel 1978), 20%-40% (DeYoreo & Karp 1979), 35% (Madore & Fernie 1980). It was only in the early eighties that this trend ceased. The recent determinations of the incidence of binaries among the Cepheids are: 20%-40% (Gieren 1982), 18% (lower limit, Lloyd Evans 1982), 25% (Russo 1982), 25%-35% (Burki 1984). At the same time we have been going over to a qualitative era from the quantitative one, i.e. very thorough studies are now available on some individual cases of binary Cepheids (e.g. McNamara & Feltz 1981; Coulson 1983; Evans 1983; Bohm-Vitense et al. 1984).

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