The Martian Climate Revisited

by Read, Peter L.; Lewis, Stephen R.

• ISBN13: 9783540407430
• ISBN10: 354040743X
• Format: Hardcover
• Copyright: 2004-03-31
• Publisher: Springer Verlag

Summary

The atmosphere and climate of Mars is a crucial factor, both for understanding the planet's past and appreciating the possibilities of its future. Given the high level of current interest in Mars, and the major advances afforded by recent space exploration, this book seeks to examine and review our knowledge and understanding of the meteorology and climate of Mars in its present state. This is based not only upon direct observations, but also on the newer techniques of modelling: numerical simulation and data assimilation. This authoritative discussion of Mars' atmosphere and climate gives a balanced review of some of the hottest issues concerning Mars' environments, its present and past climate and potential to support life, and its possible future following manned exploration.

Table of Contents

Preface	xi
Abbreviations	xv
List of figures	xvii
List of tables	xxi
List of plates	xxiii
1 An introduction to Mars	1	(14)
1.1 Comparative atmospheric science	2	(3)
1.1.1 Planetary features	4	(1)
1.1.2 Atmospheric properties	4	(1)
1.2 Past and present climates	5	(2)
1.3 Observations of the Martian climate and meteorology	7	(6)
1.3.1 Beginnings of the space age	8	(1)
1.3.2 Martian exploration renewed: the present campaign	9	(4)
1.4 Plan of the book	13	(2)
2 Mars climate models	15	(30)
2.1 Modelling the Martian atmosphere	15	(2)
2.2 Mars GCM background	17	(1)
2.3 Mesoscale modelling	18	(1)
2.4 Upper atmosphere modelling	19	(1)
2.5 GCMs	20	(19)
2.5.1 Fluid dynamics	20	(6)
2.5.2 Physical processes and environmental factors	26	(13)
2.6 Data assimilation for Mars	39	(6)
3 Mars' global-scale atmospheric structure	45	(28)
3.1 Some basics: the role of buoyancy forces	45	(4)
3.1.1 Stable and unstable stratification	45	(2)
3.1.2 Horizontal and vertical density contrasts	47	(1)
3.1.3 Stratification in a compressible atmosphere	47	(2)
3.2 Mars' zonal mean atmospheric structure	49	(5)
3.2.1 Annual mean thermal structure and net heating	50	(1)
3.2.2 Vertical structure and the atmospheric energy budget	51	(3)
3.3 Annual and zonal mean atmospheric circulation	54	(6)
3.3.1 The Held-Hou model	56	(4)
3.4 CO2 sublimation and the seasonal cycle	60	(6)
3.4.1 CO2 sublimation and the atmospheric circulation	63	(3)
3.5 Seasonal variations in Mars' zonal mean circulation	66	(5)
3.5.1 TES observations	66	(1)
3.5.2 GCM simulations of the seasonal zonal mean circulation	67	(2)
3.5.3 An osymmetric Held-Hou model	69	(2)
3.6 Summary	71	(2)
4 Topographical influences on the atmospheric circulation	73	(40)
4.1 The topography of Mars from MGS/MOLA	73	(4)
4.1.1 Mapping Mars from space	74	(1)
4.1.2 Large-scale areography of Mars	75	(2)
4.2 Stationary planetary waves	77	(11)
4.2.1 Simple models of wave excitation and propagation	77	(2)
4.2.2 More realistic models	79	(8)
4.2.3 Evidence for stationary planetary wave activity	87	(1)
4.3 Low-level jets and western boundary currents (WBCs)	88	(11)
4.3.1 WBCs on Earth	88	(2)
4.3.2 A simple model of an equator-crossing WBC	90	(4)
4.3.3 W BCs more realistic models	94	(4)
4.3.4 Observations of WBCs	98	(1)
4.4 Small-scale gravity waves	99	(14)
4.4.1 A simple model for internal gravity waves generated by mountains	99	(4)
4.4.2 More realistic models of mountain lee waves	103	(2)
4.4.3 Observations of mountain waves on Mars	105	(3)
4.4.4 Large-scale gravity-wave drag	108	(5)
5 Diurnal phenomena	113	(24)
5.1 The diurnal cycle on Mars	113	(2)
5.1.1 Mars Pathfinder (MPF)	113	(2)
5.2 Planetary thermal tides	115	(13)
5.2.1 Migrating tides	117	(5)
5.2.2 Interaction with topography	122	(2)
5.2.3 Planetary free modes	124	(2)
5.2.4 Tides in a Mars GCM	126	(2)
5.3 Morning clouds, fogs, and frosts	128	(1)
5.4 Nocturnal jets	129	(4)
5.5 Slope and thermal contrast winds	133	(4)
6 Transient weather systems	137	(42)
6.1 Variable weather on Earth	137	(2)
6.1.1 Origins as instabilities	138	(1)
6.2 Observations of Martian 'weather' systems	139	(8)
6.2.1 Cloud features and weather systems	139	(2)
6.2.2 Viking Lander (VL) time series	141	(2)
6.2.3 Travelling thermal waves	143	(4)
6.3 Basic theory of baroclinic and barotropic weather systems	147	(7)
6.3.1 'Classical' models of baroclinic and barotropic instability	148	(6)
6.4 More realistic linearized models	154	(4)
6.4.1 Mixed baroclinic-barotropic instability	154	(4)
6.5 Transient weather systems in GCM simulations	158	(8)
6.5.1 Seasonal variations in baroclinic transients	159	(1)
6.5.2 Wave structures and frequencies	160	(2)
6.5.3 Topography and 'storm zones'	162	(2)
6.5.4 Transient eddy heat and momentum transports	164	(2)
6.6 Predictability and chaos	166	(11)
6.6.1 A GCM 'thought experiment': turning night into day	167	(1)
6.6.2 Intransitivity and hysteresis	168	(2)
6.6.3 A laboratory analogue storms in a teacup?	170	(3)
6.6.4 Weather regimes in simplified Mars GCMs	173	(3)
6.6.5 Tidal perturbations and chaos: shaking the table?	176	(1)
6.7 Overview	177	(2)
7 Dust storms, devils, and transport	179	(40)
7.1 A desert planet	179	(4)
7.2 The nature of Mars' sand and suspended dust	183	(5)
7.2.1 Martian soil and sand	183	(1)
7.2.2 Suspended dust in the atmosphere	183	(5)
7.3 How does dust enter and leave the atmosphere?	188	(10)
7.3.1 Near-surface wind stress	188	(4)
7.3.2 Convection and 'dust devils'	192	(5)
7.3.3 Dust deposition and removal processes	197	(1)
7.4 Dust Storms	198	(7)
7.4.1 Local and regional storms	199	(2)
7.4.2 Planet-encircling storms	201	(4)
7.5 Processes influencing dust storm initiation, evolution, and decay	205	(6)
7.5.1 Meteorological organization of dust lifting	205	(2)
7.5.2 Radiative-dynamical feedbacks	207	(1)
7.5.3 Dust storms in GCMs	208	(3)
7.6 Dust transport, climate, and interannual variability	211	(8)
7.6.1 Transport, erosion, and deposition	211	(4)
7.6.2 Interannual variability of dust storms and climate	215	(4)
8 Water, climate, and the Martian environment	219	(30)
8.1 Water and Mars	219	(2)
8.2 Water and the formation of the ancient Martian landscape	221	(12)
8.2.1 Valley networks	223	(2)
8.2.2 Outflow channels and flood plains	225	(3)
8.2.3 Oceanus Borealis?	228	(2)
8.2.4 Glacial activity and permafrost	230	(1)
8.2.5 Warm and wet or cold and dry?	231	(2)
8.3 Evidence for water in Mars' present climate	233	(10)
8.3.1 Residual ice caps	233	(1)
8.3.2 Atmospheric water vapour	234	(2)
8.3.3 Water ice clouds	236	(3)
8.3.4 Fog and frost	239	(1)
8.3.5 The regolith	240	(3)
8.4 Modelling the atmospheric water cycle	243	(4)
8.4.1 Diffusive models	243	(1)
8.4.2 Water cycles in simple GCMs	244	(1)
8.4.3 Comprehensive GCMs	245	(2)
8.5 Outstanding questions	247	(2)
9 Cyclic climate change	249	(26)
9.1 Cyclic climate change and the polar layered terrains (PLTs)	249	(4)
9.2 Quasiperiodic and chaotic astronomical cycles	253	(1)
9.2.1 Spin-orbit cycles on Mars	253	(1)
9.2.2 Spin-orbit cycles and the Earth's climate	253	(2)
9.2.3 Obliquity cycles and insolation	255	(1)
9.2.4 Correlating PLTs with the obliquity cycle	256	(2)
9.3 Modelling the response to the obliquity cycle	258	(1)
9.3.1 Qualitative overview	258	(1)
9.3.2 Quantitative models: energy balance models	259	(2)
9.3.3 Quantitative models: GCMs	261	(3)
9.4 Scenarios for Mars' response to obliquity variations	264	(9)
9.4.1 Low obliquity conditions	264	(1)
9.4.2 High obliquity conditions	265	(5)
9.4.3 Obliquity cycles and the 'gullies'?	270	(3)
9.5 Mars' variable climate	273	(2)
10 Future climates: the human factor?	275	(16)
10.1 Human exploration of Mars in the short term	275	(3)
10.2 Long-term exploration and colonization?	278	(1)
10.3 Basic requirements for terraforming Mars	279	(2)
10.4 Feedbacks and the 'runaway greenhouse'?	281	(2)
10.5 Energy requirements and timescales	283	(1)
10.6 Practical methods of achieving global warming	284	(1)
10.6.1 Polar reflectors	285	(1)
10.6.2 Polar albedo	285	(1)
10.6.3 Artificially-enhanced greenhouse warming	285	(1)
10.7 How long would it last?	286	(1)
10.8 We can - but should we?	287	(4)
Appendix A A climate database for Mars	291	(10)
Afterword	301	(2)
References	303	(18)
Index	321