A Short Course in Cloud Physics

M.K. Yau,R R Rogers

• Éditeur: Butterworth-Heinemann
• Année: 1996
• ISBN:
  9780080570945
• Édition: 3
• Sujet: Physical Sciences
• Sous-sujet: Meteorology & Climatology

Covers essential parts of cloud and precipitation physics and has been extensively rewritten with over 60 new illustrations and many new and up to date references. Many current topics are covered such as mesoscale meteorology, radar cloud studies and numerical cloud modelling, and topics from the second edition, such as severe storms, precipitation processes and large scale aspects of cloud physics, have been revised. Problems are included as examples and to supplement the text.

1

Thermodynamics of Dry Air

Atmospheric composition

Air is a mixture of several so-called permanent gases, a group of gases with variable concentrations, and different solid and liquid particles of variable concentrations. Nitrogen and oxygen account respectively for about 78% and 21% by volume of the atmosphere’s permanent gases, with the remaining 1% consisting mainly of argon, but with trace amounts of neon, helium, and other gases. The composition of air is remarkably uniform, with the relative proportions of these permanent gases being essentially the same the world over and up to an altitude of 90 km.

The most abundant of the gases present in variable amounts are water vapor, carbon dioxide, and ozone. These gases strongly affect radiative transfer in the atmosphere. Water vapor is also of central importance in atmospheric thermodynamics.

The particles of solid and liquid material suspended in the air are called aerosols. Common examples are smoke, dust, and pollen. The water droplets and ice crystals of which clouds are composed are aerosols too, but they are usually classified with rain and other precipitation forms as hydrometeors, condensed forms of water in the atmosphere. Thermodynamics is concerned with the gases, but a select group of the aerosols called hygroscopic nuclei are crucial for the condensation of water in the atmosphere.

The approach in meteorology is to treat air as a mixture of two ideal gases: “dry air” and water vapor. This mixture is called moist air. The thermodynamic properties of moist air are determined by combining the separate thermodynamic behaviors of dry air and water vapor.

Equation of state for dry air

The equation of state for a perfect gas, or ideal gas law, expresses the relationship a...