6
R. G. Lawford
Qner = SH + LH + GF
(1.1)
where Qner = net radiation received at the surface
SH = sensible heat flux
LH = latent heat flux
GF = ground heat flux
In general, the sensible and latent heat fluxes are much larger than the
ground heat flux, with the sensible heat flux being the dominant term in
arid and semiarid regions.
The water balance can be expressed as follows:
R=P-E-S
(1.2)
where R = runoff
P = precipitation
E = evapotranspiration
S = storage
When this equation is averaged over a year or more, the changes in
the storage term generally become insignificant. On a seasonal basis,
however, storage of water in winter snow packs modulates the thermal
and runoff regimes at higher latitudes . Precipitation sets an upper limit on
the amount of evapotranspiration that can take place. In areas where the
precipitation is less than the global average, the P and E terms are large
and R is a residual term. However, in many "rainforest" areas along the
west coasts of both North and South America, P is greater than E and
runoff is a significant component of the water balance.
Study Methodology
Data Sets
In order to explore the north-south variations in the areas of interest, a
100-km wide strip of land along the western coasts of North and South
America was selected and parameters were extracted from the atlases
listed in Table 1.1. While more accurate data sources exist for some
countries, it was felt preferable to use one data source for each data type
for the entire region, provided that the source was reliable, because it
increased confidence that differences were true differences in climate
patterns rather than differences between data sources. However, where
good national records exist, they have been used to assess the reliability
of findings from this analysis. Energy and water budget parameters were
based on maps prepared from global heat budget and water balance
computations by Henning (1989) and others. In the case of the water
R. G. Lawford
Qner = SH + LH + GF
(1.1)
where Qner = net radiation received at the surface
SH = sensible heat flux
LH = latent heat flux
GF = ground heat flux
In general, the sensible and latent heat fluxes are much larger than the
ground heat flux, with the sensible heat flux being the dominant term in
arid and semiarid regions.
The water balance can be expressed as follows:
R=P-E-S
(1.2)
where R = runoff
P = precipitation
E = evapotranspiration
S = storage
When this equation is averaged over a year or more, the changes in
the storage term generally become insignificant. On a seasonal basis,
however, storage of water in winter snow packs modulates the thermal
and runoff regimes at higher latitudes . Precipitation sets an upper limit on
the amount of evapotranspiration that can take place. In areas where the
precipitation is less than the global average, the P and E terms are large
and R is a residual term. However, in many "rainforest" areas along the
west coasts of both North and South America, P is greater than E and
runoff is a significant component of the water balance.
Study Methodology
Data Sets
In order to explore the north-south variations in the areas of interest, a
100-km wide strip of land along the western coasts of North and South
America was selected and parameters were extracted from the atlases
listed in Table 1.1. While more accurate data sources exist for some
countries, it was felt preferable to use one data source for each data type
for the entire region, provided that the source was reliable, because it
increased confidence that differences were true differences in climate
patterns rather than differences between data sources. However, where
good national records exist, they have been used to assess the reliability
of findings from this analysis. Energy and water budget parameters were
based on maps prepared from global heat budget and water balance
computations by Henning (1989) and others. In the case of the water