Lines of constant latitude are called parallels, and winds parallel to the parallels are identified as zonal flows (Fig. 11.2). Lines of constant longitude are called meridians, and winds parallel to the meridians are known as meridional flows.
Between latitudes of 30° and 60° are the midlatitudes. High latitudes are 60° to 90°, and low latitudes are 0° to 30°. Each 1° of latitude = 111 km.
Tropics, subtropics, subpolar, and polar regions are as shown in Fig. 11.2. Regions not in the tropics are called extratropical; namely, poleward of about 30°N and about 30°S.
For example, tropical cyclones such as hurricanes are in the tropics. Low-pressure centers (lows, as indicated by L on weather maps) outside of the tropics are called extratropical cyclones.
In many climate studies, data from the months of June, July, and August (JJA) are used to represent conditions in N. Hemisphere summer (and S. Hemisphere winter). Similarly, December, January, February (DJF) data are used to represent N. Hemisphere winter (and S. Hemisphere summer).