As
the Earth rotates on its axis, creating the cycle of night and day that
scientists refer to as the diurnal cycle,
there is a delay between the time when the earth-atmosphere system is
irradiated and when the temperature begins to increase on the surface
of the planet. This delay is known as the thermal response, and depending
on the time of the year and the latitude, the lag can be as long as three
or four hours. An example would be that the hottest time of day during
a typical summer afternoon would be in the mid afternoon, not at solar
noon.
The figures to the right, from the NOAA Climate
Prediction Center show global and ultraviolet (UV) radiation (top
graph) on a mostly clear day, and the variation of surface temperature
(below graph) for the same time period. By the time the surface temperature
reaches its maximum, the amount of UV radiation reaching the surface has
decreased almost by half of that at solar noon. Also see Solar
Heating Sensitivity- Land vs. Ocean.
The "dark
side" of the diurnal cycle is particularly important in regions where
temperatures drop below the freezing point of water, normally 0 degrees
Celsius, when water turns to ice and expands. This force, which can crack
boulders and burst pipes, is a major mechanism for geologic weathering,
especially through repeated cycles of freeze and thaw.
Earth's
Daily Pulse
Over the course of a day, the rhythm of night and day influences
other natural pulses, such as the tides. The
gravitational effects of the sun and moon, which will vary over
the course of the year and lunar phase, have an impact on daily
tide cycles. Image
above from NASA shows a synthetic view of how the tides move
around the world's oceans over a sixteen day period. Blue indicates
places where the ocean level is lower than average reference
height, and red areas depict where it's higher.
See
NOAA's
Tides Online for access to current tidal data from the National
Ocean Service.
Plants
have a role in weather and climate patterns, and one of the
ways they influence the climate system is through the process
of photosynthesis. Driven by the sunlight during the day, plants
take in carbon dioxide, splitting off the carbon which it then
combines with hydrogen from water to form carbohydrates which
can be stored as fuel for later. The remaining oxygen is released
as free oxygen and water vapor is transpired in active photosynthesis.
FORCING
FACTORS
The
tilt of the Earth's axis creates seasonal variability, but there
are other factors that may impact climate systems at the annual
scale, such as volcanic aerosols which can cool climate and shorten
growing seasons.
How
Measured Instruments used to track annual variability
and climate patterns include thermometers, rain gauges, and stream
gauges. Paleo
proxies such as tree rings and cores from corals and
ice caps and glaciers also provide information on an annual resolution
in terms of precipitation and in some cases extreme events such
as fires or volcanic activity.
Diurnal
Cycle & Carbon Cycle
The image above shows the modeled effect of the diurnal cycle of carbon
metabolism on the annual mean atmospheric CO2 concentration and
is from a study by "Terrestrial Carbon Metabolism and Atmospheric CO2
" by Dr. David Randall, Colorado
State University, Department of Atmospheric Science.
Images from NWS, NOAA and NASA.
http://www.ncdc.noaa.gov/paleo/ctl/clisci0.html
Downloaded Sunday, 26-May-2013 02:59:04 EDT
Last Updated Wednesday, 20-Aug-2008 11:22:39 EDT by
paleo@noaa.gov
Please see the
Paleoclimatology Contact Page or the
NCDC Contact Page if you have questions or comments.
As
the Earth rotates on its axis, creating the cycle of night and day that
scientists refer to as the 
Plants
have a role in weather and climate patterns, and one of the
ways they influence the climate system is through the process
of photosynthesis. Driven by the sunlight during the day, plants
take in carbon dioxide, splitting off the carbon which it then
combines with hydrogen from water to form carbohydrates which
can be stored as fuel for later. The remaining oxygen is released
as free oxygen and water vapor is transpired in active photosynthesis.