Remote Sens. 2016, 8, 286 3 of 15
Due to the large spatial extent and the sheer volume of water in the Great Lakes, the lakes have
been shown to play a large role in the surface climate of the region [
22
]. In the autumn, the heat stored
in the water bodies is released in the form of latent heat of evaporation. Thus, the highest evaporation
rates usually occur during this time of year (late fall and early winter). Shorter day lengths together
with an increase in cloudiness gradually decrease the air temperatures. The temperature of the lakes
continues to decline in the winter, when the frigid and dry Arctic air from the northwest travels over
the moist warmer lakes. In early spring, increasing solar radiation begins to heat the surface and
the overlying atmosphere, resulting in the thaw of snow and lake ice (if any is present). During this
period, the lakes are usually warmer than the land and tend to keep the surrounding area cool, thus
occasionally calm conditions continue well into April. In the summer, the longer sunshine duration
warms the surface layer of water in the lakes, making surface water warmer and less dense than the
heavier and colder water below.
Remote Sens. 2016, 8, 286 3 of 15
Due to the large spatial extent and the sheer volume of water in the Great Lakes, the lakes have
been shown to play a large role in the surface climate of the region [22]. In the autumn, the heat
stored in the water bodies is released in the form of latent heat of evaporation. Thus, the highest
evaporation rates usually occur during this time of year (late fall and early winter). Shorter day
lengths together with an increase in cloudiness gradually decrease the air temperatures. The
temperature of the lakes continues to decline in the winter, when the frigid and dry Arctic air from
the northwest travels over the moist warmer lakes. In early spring, increasing solar radiation begins
to heat the surface and the overlying atmosphere, resulting in the thaw of snow and lake ice (if any is
present). During this period, the lakes are usually warmer than the land and tend to keep the
surrounding area cool, thus occasionally calm conditions continue well into April. In the summer,
the longer sunshine duration warms the surface layer of water in the lakes, making surface water
warmer and less dense than the heavier and colder water below.
Figure 1. The Great Lakes basin boundaries and geographic locations for water surface temperature
measurements.
3. Methods
Wan and Dozier [23] explained a fundamental theory for the land surface temperature (LST)
algorithm based on the Planck function as:
L(λ,T) = ε(λ), B(λ,T
s) (1)
where
L is emitted spectral radiance;
B is brightness temperature;
λ is wavelength;
T
s is surface temperature (K); and
ε is spectral emissivity Planck function.
However, Equation (1) can only be applied during clear-sky conditions when the spectral
radiance (L) emitted from the surface is detectable. In cloudy conditions, L cannot be retrieved from
Figure 1.
The Great Lakes basin boundaries and geographic locations for water surface
temperature measurements.
3. Methods
Wan and Dozier [
23
] explained a fundamental theory for the land surface temperature (LST)
algorithm based on the Planck function as:
Lpλ, Tq “ εpλq, Bpλ, T
s
q (1)
where
L is emitted spectral radiance;
B is brightness temperature;
λ is wavelength;
T
s
is surface temperature (K); and
ε is spectral emissivity Planck function.
However, Equation (1) can only be applied during clear-sky conditions when the spectral radiance
(L) emitted from the surface is detectable. In cloudy conditions, L cannot be retrieved from the surface
since the cloud tops, not the surface, is what is detected by the satellites. Therefore, in this study, the