LECTURE 2: INTRODUCTION 1.1 Where are the tropics and what makes them special? 1.2 The amount of energy received by the earth 1.3 Moisture in the tropics 1.4 Basic equations and scalings

1.1 Where are the tropics and what makes them special? Arbitrary definitions for where they are: Geography:Tropics are the region of the earth bounded by the tropic of Cancer (23.5 o N) and the tropic of Capricorn (23.5 o S). These are the latitudes where the sun reaches the zenith just once a year at the summer solstices. Equal Halves:The region between 30N and 30S would divide the earth into two equal halves. Defined this way, the tropics would be the source of all the angular momentum of the atmosphere and most of the heat. But this is not meteorologically sensible. Processes:Riehl (1979) chose to define the “meteorological” tropics as those parts of the world where atmospheric processes differ significantly from those in higher latitudes (see next slides). Riehl (1979) Climate and Weather in the Tropics, Academic Press.

Figure 1.1

Land and ocean contrasts Figure 1.2: Markedly non-uniform distribution of land and ocean areas in the tropics may be expected to have a large influence on the meteorology there

Annual Mean Rainfall Figure 1.3

Mean Meridional Circulations Figure 1.4

1.2 The amount of energy received by the earth Figure 1.6 Figure 1.5 Solar Radiation Received at TOA Outgoing radiation Solar absorbed Northward transport of energy Northward transport by atmosphere

Figure The amount of energy received by the earth

Figure 1.8(a)

1.2 The amount of energy received by the earth Figure 1.8(b)

1.3 Moisture in the tropics Figure 1.9

Figure Moisture in the tropics

Figure Moisture in the tropics

Figure 1.12(b) Figure 1.12(a)

1.4 Basic equations and scalings where Adiabatic, Frictionless Equations in Pressure Coordinates