1. Intergovernmental Panel on Climate Change Climate Change 1994: Radiative Forcing of Climate Change J. T. Houghton et al. Eds. (Cambridge Univ. Press Cambridge 1995) chap. 2.
2. K. E. Trenberth Ed. Climate System Modeling (Cambridge Univ. Press Cambridge 1992).
3. The troposphere is the part of the atmosphere that is generally characterized by sharply decreasing temperatures with increasing altitude roughly 6°C/km. Its thickness ranges from roughly 8 km in higher latitudes to 16 km in the tropics. Because the cloudless atmosphere is nearly transparent to incoming solar radiation the troposphere is essentially heated from below with dynamically induced vertical mixing shaping the vertical temperature structure. The upper limit of the troposphere is conventionally called the tropopause.
4. The stratosphere begins at the tropopause and extends to an altitude of about 50 km. Its temperature slowly increases with altitude mainly resulting from the absorption of solar ultraviolet radiation by ozone.
5. Under adiabatic conditions (no addition or subtraction of heat) an air parcel conserves its entropy or equivalently its potential temperature as it undergoes expansion or compression. From direct manipulation of the first law of thermodynamics potential temperature is defined as Θ = T ( P 0 / P ) k where T is temperature P is pressure P 0 is a reference pressure at Earth’s surface κ = R / mc P R is the universal gas constant m is the molecular weight of dry air and c P is the specific heat of air at constant pressure. Under these idealized circumstances the first law of thermodynamics adopts the simple form d Θ/ dt = 0; that is potential temperature is conserved following an air parcel over time t. In the atmosphere Θ generally increases with altitude markedly so in the stratosphere. Long-term transport between the troposphere and stratosphere must be tightly constrained by the magnitude of net diabatic processes ultimately of dynamical origin moving air across surfaces of constant potential temperature. Static stability is defined here for convenience as the vertical pressure gradient of potential temperature (−∂θ/∂ P ) and is a measure of the resistance of air to vertical displacement. Use of potential temperature as a vertical coordinate allows straightforward use of the radiosonde-based meteorological network of wind temperature and pressure data to calculate 3D air trajectories in the troposphere to the extent that the air moves nearly adiabatically. This substitution is a powerful diagnostic tool for addressing tracer movements because it evades the problem that standard meteorological measurements do not measure vertical velocity directly (8-11).