|
||
|
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | |
|
||
First Edition Preface Second Edition Preface Acknowledgments
Section A A index 151-159 of 917 terms
Previous 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 Next
active nitrogen—(Also known as odd nitrogen species.) Reactive forms of nitrogen comprising nitric oxide, NO, and nitrogen dioxide, NO2; usually designated by NOx. These oxides of are responsible for ozone formation in the troposphere and play a major part in ozone loss in the stratosphere. The major sources of active nitrogen in the atmosphere are combustion, soil emissions, lightning, and the reaction of nitrous oxide with excited oxygen atoms in the stratosphere.
active permafrost—Permanently frozen ground (permafrost) which, after thawing by artificial or unusual natural means, reverts to permafrost under normal climatic conditions; opposed to passive permafrost. Compare active layer.
active site—A site on an ice nucleus that forms ice at a lower supersaturation or a smaller supercooling than elsewhere, resulting from a local impurity or defect giving a region of local strain and deformation in the atomic arrangement of the nucleus, matching it more closely to the arrangement of molecules in ice, and a lower energy requirement for nucleation.
active system—A remote sensing system that transmits its own electromagnetic energy, then measures the properties of the returned radiation. Active systems require more power to operate than passive systems, but can be designed to have greater sensitivity. Examples of active systems are radar, lidar, and acoustic sounders.
activity coefficient—A measure of the extent to which substances, on dissolving in water, form charged ions or associate to form multiple molecules; the amount dissolved influences colligative effects, such as equilibrium freezing point depression of solution drops and reaction rates in solution.
activity—Measure of the effective concentration of a chemical in the gas or liquid phase. The activity is usually less than the mass concentration, from which it differs due to the nonideal nature of gases and solutions. In the limit of very dilute mixtures, the activity is the same as the concentration for liquid solutions, or the partial pressure for gases. The activity coefficient, usually denoted by γ or f, is the ratio of the activity to the actual physical concentration.
actual elevation—The vertical distance above mean sea level of the ground at the meteorological station. This term is denoted by the symbol H in international usage.
actual evaporation—Quantity of water evaporated from a region comprising open water or ice surfaces, bare soil, or vegetation-covered soil.
actual evapotranspiration—See effective evapotranspiration.
actual pressure—The atmospheric pressure at the level of the barometer (elevation of ivory point), as obtained from the observed reading after applying the necessary corrections for temperature, gravity, and instrument errors. This may or may not be the same as station pressure.
Previous 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 Next