Geoscience Reference
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taken as their boundaries; they can be considered as the natural conveyance systems for
mass and energy on the land surfaces of the Earth. In meteorology, the concern is more on
atmospheric motions and weather systems, and this has led to a somewhat different scale
classification; an example of a commonly used classification is shown in Table 1.5.
Table 1.5 A common scale classification in the
atmosphere (after Orlanski, 1975)
Nomenclature
Scale range
Micro
γ
<
20 m
Micro
β
20-200 m
Micro
α
200 m-2 km
Meso
γ
2 km-20 km
Meso
β
20 km-200 km
Meso
α
200 km-2000 km
Macro
γ
>
2000 km
Global
weather
patterns
Continental
scale
10
6
m
3
km
Synoptic
weather
systems
River
basin
scale
Seasonal
regimes
Frontal
rains
Headwater
catchment
scale
Thunderstorms
10
3
m1 m
River storm
Deep
runoff
Base
groundwater
flow
Soil drainage
and
ABL convection
Evaporation
Vegetation
100 m
soil
changes
Hillslope
or field
scale
moisture
drying
Overland flow
10 m
Infiltration
Atmospheric
Sand column
1m
Local
scale
turbulence
experiments
10
0
s
10
2
s
10
4
s
10
6
s
10
8
s
second
minute
hour
day
week
month
year
Time scale
Fig. 1.2 Approximate ranges of spatial and temporal scales of some common physical processes that are
relevant in hydrology.
