Geoscience Reference
In-Depth Information
surface is important for hydrometeorology because it alters the way energy from
the Sun enters the atmosphere from below and, if sufficiently extensive, land-use
change has impact on regional and perhaps global climate and weather. Examples
of such change include urban heat islands and changes to regional evaporation due
to the building of large dams, extensive irrigation, and land-cover change such as
deforestation.
When compared with most natural changes in other spheres of the globe,
change in the anthroposphere is happening very rapidly. This is partly because
human population has increased quickly over the past few centuries and still is
today, but also because strides in technology have empowered humans to
directly and indirectly effect change to the environment in new and different
ways, and because as society develops the per capita demand for energy
increases hugely.
Important points in this chapter
Hydrometeorology
: hydrometeorology (and this text) concerns the physics,
mathematics, and statistics of processes and phenomena involved in
exchanges between the atmosphere and ground that typically occur over
hours or days, and how the time average of these exchanges combine to
define hydroclimatology.
●
Water reservoirs
: the size of the Earth's water reservoirs are poorly defined
but include the oceans (~ 95.6%), groundwater (~2.4%), frozen water (1.9%),
and water bodies, soil moisture, atmospheric water, rivers and biological
water (in total ~ 0.01%).
●
Water cycle
: as a global average about 90% of oceanic evaporation falls back
to the oceans as precipitation, the remainder being transported over land;
and about 55-65% of the precipitation falling over land re-evaporates
(depending on the continent) leaving 35-45% to runoff back to the ocean in
rivers and icebergs.
●
Atmosphere
:
—
Constituents and structure
: About 80% N
2
and 20% O
2
and other minority
gases (CO
2
, O
3
, H
2
O, etc.), 99.9% of which are within 80 km of the ground
in the troposphere, stratosphere, mesosphere, thermosphere, with most
water vapor in the lower troposphere within 10 km of the ground.
—
Circulation
: Differential heating by the Sun causes global circulation in
the troposphere which moves energy toward the poles and which is
complicated by the Coriolis force but is, on average, organized.
—
Variance
: Contributions to the variance of the atmosphere arise at
frequencies linked to the seasonal cycle, transient weather systems,
and the daily cycle, with these contributions separated by a distinct
spectral gap
from those at higher frequencies that are associated
with turbulence.
●
