Page 157 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

5.1
EARTH’S HOTTEST “HOT SPOTS”
In terms of air temperature, Death Valley, California, is considered the hottest place on Earth. Based on land surface temperature, locations in Iran, China, and Australia are hotter.
Highest LST in 2008: Turpan Depression, China 66.8°C
LST is higher than air temperature because the surface absorbs solar radiation, heats up, and then emits infrared energy.
5.2
World record surface temperature:
Death Valley, USA 56.7°C
Air temperatures are moderated by the circulation of air above the suface. The LST on this day was likely higher than the measured air temperature.
Highest LST measured from 2003 to 2009: Lut Desert, Iran 70.7°C
Air temperatures = black
Land surface temperatures = red
Highest LST in 2003: Queensland, Australia 69.3°C
EFFECT OF ALBEDO AND LAND COVER ON LST
These images of China’s Turpan Depression show how spatial variations in albedo affect LST. Notice that the lowest LSTs are in areas with agriculture and other plant cover. [NASA]
Light-coloured rock and sediment with a high albedo reflect more solar radiation and are therefore cooler.
Dark-coloured sand dunes have a lower albedo and absorb more solar radiation, heating the surface.
Flaming Mountain
Natural-colorur
Shanshan dune field 0
dark-coloured dunes 0
10 Km
10 Km
crops Skin Temperature
bright sediment
Surface Temperature (C˚)
30 40 50 60
121
Earth’s hottest locations are determined by air temperature, which is measured at least 1.2–1.8 m above a surface in an instrument shelter (shown in
Figure 5.4). The MODIS sensor aboard several satellites provides another temperature measurement, known as
land surface temperature (LST), or land skin tempera- ture, which is often significantly hotter than air tempera- ture (GIA 5.1). One main factor influencing LST is surface albedo (GIA 5.2).
GEOquiz
Visit the Study Area in MasteringGeographyTM to explore temperature extremes.
Visualize: Study a geoscience animation of temperature extremes. Assess: Demonstrate understanding of temperature extremes
(if assigned by instructor).
1. Explain: Why are the land surface temperatures in Figure 5.1 hotter than Death Valley's air temperature?
2. Analyze: Based on the two images in Figure 5.2, explain how and why LST varies across the Shanshan dune field.
geosystems in action 5HEaT wavES