Climate Aspects of the Tropics PDF

# Climate Aspects of the Tropics ## Contents - Features of Tropical Climates - Climate Boundaries, Subdivision, and Transition Zones of the Tropics - References ## Abstract Unlike the high latitudes and most of the mid-latitudes, the tropical ecozone benefits from a constant radiation surplus....

# Climate Aspects of the Tropics ## Contents - Features of Tropical Climates - Climate Boundaries, Subdivision, and Transition Zones of the Tropics - References ## Abstract Unlike the high latitudes and most of the mid-latitudes, the tropical ecozone benefits from a constant radiation surplus. In daytime, the sunrays descend at a steep angle up to 90° at noon between the tropics twice per year. Hence, long-shaded slopes in mountain landscapes do not exist. Lengths of day and night stay almost the same at the equator (approx. 12 h.), while at the tropics of Cancer and Capricorn, minimum and maximum day lengths vary within a time span from 10.5 to 13.5 h. As a result marked thermal seasons are absent in the tropical climates. ## Keywords - "Warm" and "Cold" tropics - "Humid" and "Arid" tropics - Diurnal Temperature Amplitude - ITCZ ## Features of Tropical Climates - **Cooler mountain climates within the tropics are considered tropical.** While some biologists speak of "subtropical" belts or areas, this latter term should be restricted to the eponymous ecozones of the tropics. - **Tropical climates lack distinct thermal** seasons. Diurnal temperature amplitudes are larger than seasonal temperature amplitudes. - **Boundaries of tropical climates do not follow a straight line** but instead show an irregular course depending on factors such as cold or warm ocean currents, the extension of moist or dry areas, as well as the size and distribution of land masses. The tropical boundary can shift from year to year. The local impact and strength of El Niño or La Niña phenomena might be mentioned as examples of crucial triggers. - **Moisture conditions play a significant role in defining tropical climates.** Most tropical climates are governed by summer rains during solstice. Most botanists tend to view the dominance of summer rain as a significant criterion. However, using rainfall regimes or the number of humid months to define the tropics is not useful. Poleward adjacent subtropical areas along the eastern coasts of continents as in southern Africa, both Americas, eastern Australia, and the Far East reveal similar solstice rainfall patterns. ## Climate Boundaries, Subdivision, and Transition Zones of the Tropics **The presence of distinct thermal seasons differentiates tropical from subtropical climates** as well as the warmth of the lowlands. The requirement of monthly mean minimum temperature of >18 °C and the lack of any frost event are mentioned as essential for the occurrence of tropical lowland forests. ### The Intertropical Convection Zone (ITCZ) - The Irregular course of the both tropical boundaries shows two particular anomalies: - one with far-reaching poleward shifts of the northern ITCZ in summer of the northern hemisphere - four with equatorward anomalies of the southern ITCZ during the warm period there. - The farthest extension toward the extratropics stretches to the foothills of the Himalaya, up to approximately 33°N. - **Continental landmasses experience tropic boundaries extending further poleward compare to sea surfaces.** This is due to the different reaction times of surface warming. - **The northern hemisphere has more landmasses.** This results in the northern ITCZ and accordingly the northern tropical boundary protrude further in a north-ward position than does the southern equivalent into a southward one. - **Cold, equator-bound ocean currents lead to narrowings of the tropical sector.** This effect becomes obvious close to the Peruvian and northwestern Mexican seaboards in particular and the northwestern as well as southwestern African seashores as further examples. - In these cases fog deserts such as the Atacama and Peru Desert, the Namib, and the Western Sahara as well as the Vizcaino on Baja California mask an invisible longitudinal boundary between subtropical mild and tropical hot deserts. ## References - MacGregor GR, Nieuwolt S (1998) Tropical climatology. Wiley, Chichester - Richter M (2001) Vegetationszonen der Erde. Klett-Perthes, Gotha/Stuttgart - Troll C, Paffen KH (1964) Karte der Jahreszeiten-Klimate der Erde. Erdkunde 18:5-28 - Lauer W (1975) Vom Wesen der Tropen. Klimaökologische Studien zum Inhalt und Abgrenzung eines irdischen Landschaftsgürtels. Akademie der Wissenschaften und der Literatur Abhandlungen der Mathematisch-Naturwissenschaftlichen Klasse 3, Mainz, p 52 - Lauer W (1993) Climatology. In: Pancel L (ed) Tropical forestry handbook, vol 1. Springer, Berlin/New York, pp 96-164