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Air Masses and Frontal Zones APPENDIX A Air Masses and Frontal Zones body of air in which the temperature and moisture is fairly uni­ Aform over a large area is know as an air mass. The boundary be­ tween a given air mass and its neighbor is usually sharply defined. This discontinuity is termed a front. In the convergence zone between the tropical and polar air masses, winds are variable and high and ac­ companied by stormy weather. This zone is called the polar front. A large number of the Earth's cyclonic storms are generated here. The properties of an air mass are derived partly from the regions over which it passes. Those land or ocean surfaces that strongly impress their char­ acteristics on the overlying air masses are called source regions. Air masses are classified according to their latitudinal position (which de­ termines thermal properties) and underlying surface, whether conti­ nent or ocean (determining moisture content). They are summarized in Table A.l and illustrated in Figure A.l. Table A.l. Properties of air masses0 Major group Subgroup Source region Properties of source Polar Polar Arctic Basin; northern Cold, dry, very stable (including continental Eurasia and northern North arctic) (cP) America; Antarctica Polar Oceans poleward of 40° or Cool, moist, unstable maritime 50° (mP) Tropical Tropical Low-latitude deserts, Hot, very dry, stable (including continental especially equatorial) (c71 Sahara and Australian Deserts Tropical Oceans of tropics and Warm, moist, greater maritime subtropics instability toward (m71 west side of ocean °From Trewartha et al. (1967), p. 105. 135 136 Appendix A. Air Masses and Frontal Zones Continental tropical ource, cT ¥ ¥"' ¥"' ¥"' Figure A.l. Source regions of air masses in relation to the polar front and the intertropical convergence zone (lTC). From Elements of Physical Geography, 4th ed., by Arthur N. Strahler and Alan H. Strahler, p. 125. Copyright © 1989 by John Wiley & Sons, Inc. Reprinted by permission of John Wiley & Sons, Inc. APPENDIX B Common and Scientific Names Plants acacia Acacia ash Fraxinus aspen, quaking Populus tremuloides basswood Tilia beech, southern Nothofagus birch Betula black-eyed Susan Rudbeckia hirta bluestem, big Andropogon gerardii bluestem, little Schizachyrium scoparium buffalograss Buchloe dactyloides cactus, prickly pear Opuntina engelmanni cactus, saguaro Carnegiea giganteus cedro espinoso Bombacopsis fendleri chestnut, sweet (American) Castanea dentata creosote bush Larrea tridentata Douglas fir Pseudotsuga menziesii elm Ulmus eucalyptus Eucalyptus fir Abies hemlock Tsuga hemlock, western Tsuga heterophylla hickory Carya hornbeam, American Carpinus caroliniana juniper Juniperus kauri tree Agathis australis larch Larix 137 138 Appendix B. Common and Scientific Names laurel Kalmia locoweed Oxytropis magnolia Magnolia maple Acer maple, sugar Acer saccharum mesquite Prosopis oak Quercus oak, cork Quercus suber ocotillo Fouquieria splendens pine Pinus pine, lodgepole Pinus contorta pine, ponderosa Pinus ponderosa pinyon Pinus edulis podocarp tree Podocarpus popular Populus red cedar, western Thuja plicata redwood Sequoia sempervirens sagebrush Artemisia smoke tree Dalea spinosa spruce Picea sunflower, common Helianthus annuus tamarisk (salt-cedar) Tamarix gallica tulip tree Liriodendron tulipifera walnut Juglans willow Salix Animals antelope (see pronghorn) badger, American Taxidea taxus bear Ursidae bear, polar Thalarctos maritimus beaver Castor canadensis bison, American Bison bison bongo Boocercus eurycerus buffalo, African Syncerus caffer camel Camel us caribou Rangifer tarandus chipmunk Eutamias and Tamias chipmunk, alpine Eutamias alpinus crocodile Crocodylus deer Cervidae elephant, African Loxodonta africana Common and Scientific Names 139 elk, American CeiVus canadensis emu Dromaius novaehollandiae ermine Mustela fox Vulpes and Alopex gnu (wildebeest) Connochaetes taurinus goat, North American mountain Oreamnos americanus guanaco Lama guanacoe hamster Cricetidae hare, arctic Lepus arcticus hippopotamus Hippopotamus amphibius ibex Capra hircus kiwi Apteryx krill shrimp Euphausia superba lemming Dicrostonyx and Lemmus lemur Lemuridae lion, mountain (puma, panther) Felis concolor marmot, yellow-bellied Marmota flaviventris marten, American Martes americana mink Mustela vison moose Alces alces musk oxen Ovibos moschatus okapi Okapia johnstoni panther (see mountain lion) penguin Spheniscidae pika Ochotona princeps plover Pluvialis and Charadrius prairie dog Cynomys pronghorn antelope Antilocapra americana reindeer (see caribou) sabel (see marten) sea elephant Mirounga leonina turkey, wild Meleagris gallopavo walrus Odobenus rosmarus whale, blue Sibbaldus musculus whale, finback Balaenoptera physalus wolf Canis lupus zebra Equus burchelli APPENDIX C Conversion Factors or readers who wish to convert measurements from the metric sys­ Ftem of units to the inch-pound-Fahrenheit system, conversion fac­ tors are listed below. Multiply By To obtain millimeters 0.039 inches centimeters 0.394 inches meters 3.281 feet kilometers 0.621 miles square meters 10.764 square feet square kilometers 0. 386 square miles hectares 2.471 acres centigrade 1.8 + 32 Fahrenheit 141 Glossary of Technical Terms air mass a large and essentially homogeneous body of air, many thou­ sands of km2 in area, characterized by uniform temperature and hu­ midity Alfisol soil order consisting of soils of humid and subhumid climates, with high base status and argillic horizons alkali salts found in soils, as in some deserts anadromous fisheries migrating from salt water to spawn in fresh wa­ ter, such as salmon Aridisol soil order consisting of soils of dry climates, with or with­ out argillic horizons, and with accumulations of carbonates or sol­ uble salts arroyo in Southwest United States, steep-sided dry valley, usually inset in alluvium azonal zonal in a neighboring zone but confined to an extra-zonal environment in a given zone; mountains that cut across the lowland ecological zones or regions biomass the dry mass of all living material in an area black prairie soil (also called prairie soil or Brunizem) acid grassland soil bog a wet area covered by acid peat bolson from a Spanish word, meaning pocket, for a basin of inland drainage broadleafed with leaves other than linear in outline; as opposed to needleleafed or grass-like (graminoid) 143 144 Glossary of Technical Terms brown forest soil (also called gray-brown podzolic) acid soil with dark brown surface layers, rich in humus, grading through lighter colored soil layers to limy parent material; develops under deciduous forest brown soil alkaline soil having thin brown surface layer that grades downward into a layer where carbonates have accumulated; devel­ ops under grasses and shrubs in semi-arid environments calcification accumulation of calcium carbonate in a soil chaparral sclerophyll scrub and dwarf forest found throughout the coastal mountain ranges and hills of central and southern Califor­ nia chernozem fertile, black or dark brown soil under prairie or grass­ land with lime layer at some depth between 0.6 and 1.5 m chestnut-brown soil short-grass soil in subhumid to semi-arid climate with dark brown layer at top, which is thinner and browner than in chernozem soils, that grades downward to a layer of lime accumu­ lation climate generalized statement of the prevailing weather conditions at a given place, based on statistics of a long period of record climatic climax the relatively stable community that terminates on zonal soils climatic regime seasonality of temperature and moisture continental shelf the edge of a continent submerged in relatively shal­ low seas and oceans cyclone whirling storm characteristic of middle latitudes; any rotat­ ing low-pressure air system deciduous woody plants, or pertaining to woody plants, that sea­ sonally lose all their leaves and become temporarily bare stemmed delta the flat alluvial area at the mouth of some rivers where the mainstream splits into several distributaries desert supporting vegetation of plants so widely spaced, or sparse, that enough of the substratum shows through to give the dominant tone to the landscape desertification degradation of the plant cover and soil as a result of overuse, especially during periods of drought desert soil shallow, gray soils containing little humus and excessive amounts of calcium carbonate at depths less than 30 ern desert-like savanna tropical semi-desert with scattered low trees or shrubs Glossary of Technical Terms 145 division as defined for use in this book: a subdivision of a domain determined by isolating areas of definite vegetation affinities that fall within the same regional climate (continents) or areas of simi­ lar water temperature, salinity, and currents (oceans) doldrums an area near the equator of very ill-defined surface winds associated with the intertropical convergence zone domain as defined for use in this book: groups of ecoregions with re- lated climates (continents) or water masses (oceans) dry savanna or steppe with six to seven arid months in each year dry steppe see dry savanna ecoregion major ecosystem, resulting from large-scale predictable patterns of solar radiation and moisture, which in turn affect the kinds of local ecosystems and animals and plants found there ecosystem an area of any size with an association of physical and bi­ ological components so organized that a change in any one compo­ nent will bring about a change in the other components and in the operation of the whole system edaphic resulting from the character
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