Question

Why are the diurnal and annual range of temperature high in tropical deserts?

Answer 1

Tropical deserts show very large day–night and year–to‑year temperature swings because they lie under persistent high‑pressure belts with clear, cloudless skies and extremely dry air; without clouds or water vapor to reflect incoming solar radiation or to trap outgoing longwave radiation, the ground receives intense daytime heating and then loses heat very rapidly at night. In addition the surface is usually sand or bare rock with very low heat capacity and little soil moisture or vegetation, so it heats up quickly by day and cools quickly by night; these same dry, cloudless conditions also provide little atmospheric buffering of seasonal changes in insolation, so the annual range is relatively large (in some tropical deserts the diurnal range can be as much as 28°C while the annual range is about 17°C).