Transcript 1.Solar-Radiation.Energy.Temp

GLOBAL PATTERNS OF THE
CLIMATIC ELEMENTS:
(1) SOLAR ENERGY
(Linked to solar insolation
& R, net radiation)
CONTROLS OF SOLAR INSOLATION
1) Sun angle (intensity) -- changes with latitude,
time of day, time of year
2) Duration (day length) -- changes with latitude,
time of year
3) Cloud cover
(and general reflectivity of atmosphere)
4) Surface albedo
(water, soil, snow, ice, vegetation, land use)
In general, land areas (with lower atmospheric moisture)
receive more insolation than adjacent water areas and
the
REVIEW OF
INSOLATION
DURATION
INTENSITY
RADIATION /
ENERGY BALANCE
Q* = ( K↓ - K↑ ) + ( L↓ - L↑ )
where K↓ = direct + diffuse shortwave
solar radiation
Kiehl and Trenberth (1997) BAMS
Trenberth et al. (2009) BAMS
Radiative Components
Net short-wave radiation =
short-wave down - short-wave up
Net long-wave radiation =
long-wave down - long-wave up
Net radiation (R net) =
net short-wave radiation + net long-wave radiation
Positive values represent energy moving towards the
surface, negative values represent energy moving
away from the surface.
Net short-wave radiation =
Positive values represent
energy moving towards the
surface, negative values
represent energy moving
away from the surface.
SW absorbed =
Function of
INTENSITY &
DURATION & sun
angle / albedo
Net long-wave radiation =
Positive values represent
energy moving towards the
surface, negative values
represent energy moving
away from the surface.
Net Surplus
Annual mean absorbed solar radiation,
emitted longwave radiation (OLR) and
net radiation by latitude
S = Solar radiation T = Terrestrial
Net Radiation =
Positive values represent
energy moving towards the
surface, negative values
represent energy moving
away from the surface.
Non-Radiative Components
Sensible heat flux (H) = direct heating, a
function of surface and air temperature
Latent heat flux (LE) = energy that is stored
in water vapor as it evaporates, a function of
surface wetness and relative humidity
Positive values for sensible and latent heat flux
represent energy moving towards the atmosphere,
negative values represent energy moving away from
the atmosphere.
Non-Radiative Components
Change in heat storage (G) =
net radiation - latent heat flux - sensible heat flux
G = R net - LE - H
Positive values for change in heat storage
represent energy moving out of storage,
negative values represent energy moving into
storage.
Sensible Heat Flux = H
Positive values for sensible and
latent heat flux represent energy
moving towards the atmosphere,
negative values represent energy
moving away from the atmosphere.
Latent Heat Flux = LE
Positive values for sensible and
latent heat flux represent energy
moving towards the atmosphere,
negative values represent energy
moving away from the atmosphere.
R net
LE
H
Humid
Tropical /
Equatorial
rainforest
R net
H
Tropical
desert
LE
Tropical wet climate
Tropical wet-dry climate
Tropical desert
climate
Grassland /steppe climate
Change in Heat Storage = G
Positive values for change in heat
storage represent energy moving
out of storage, negative values
represent energy moving into
storage.
Air Temperature (at the surface) = T (C)
Seasonal temperature variations can be explained in terms
of the latitudinal & seasonal variations in the surface energy balance.
The pattern of temperatures are a function
of net short-wave radiation, net long-wave
radiation, sensible heat flux, latent heat
flux and change in heat storage.
GLOBAL PATTERNS OF
THE CLIMATIC
ELEMENTS:
(2) TEMPERATURE
CONTROLS OF HORIZONTAL
TEMPERATURE PATTERNS
1. Sun angle & Duration
2. Land vs. water thermal contrasts
3. Warm & Cold surface ocean
currents
4. Elevation
5. Ice/Snow albedo effects
6. Prevailing atmospheric
circulation
1. Sun Angle & Duration
Sun angle (influences intensity of solar insolation &
albedo)
Duration (based on day length)
- both change with latitude and time of year
Leads to:
zonal (east-west) distribution of isotherms,
hot in low latitudes; cold in high latitudes
2. Land vs. water thermal contrasts
Given the same intensity of insolation, the surface of any
extensive deep body of water heats more slowly and cools more
slowly than the surface of a large body of land.
4 Reasons:
1) water has a higher specific heat and heat capacity than land
2) transmission of sunlight into transparent water
3) mixing is possible in water, but not soil
4) evaporation cools air over water during hot season (less evap
during winter)
Leads to:
• annual and diurnal temperature ranges will be less in
coastal/marine locations
• the lag time from maximum insolation to time of maximum
temperature may be slightly longer in coastal/marine locations
3. Warm and Cold Ocean Currents
4. Elevation
5. Ice /Snow Albedo & Other Effects
6. Prevailing atmospheric circulation
Temperatures are affected by the
temperature "upwind" -- i.e. where the
prevailing winds and air masses originate
MAPPING HORIZONTAL
TEMPERATURE PATTERNS
•Isotherms = lines connecting points of equal temperature
•Isotherms will be almost parallel, extending east-west if
Control #1 (sun angle) is the primary control.
•If any of the other controls are operating, isotherms on a
map will have an EQUATORWARD shift over COLD surfaces
and a POLEWARD shift over WARM surfaces
•The TEMPERATURE GRADIENT will be greatest where
there is a rapid change of temperature from one place to
another (closely spaced isotherms).
Continental surfaces in winter tend to have the
steepest temperature gradients.
Temperature gradients are much smaller over oceans,
no matter what the season.
JANUARY
Northern Hemisphere
Southern Hemisphere
JULY
JANUARY
Northern Hemisphere
Southern Hemisphere
JULY
http://geography.uoregon.edu/envchange/clim_animations/
Constructed by:
Jacqueline J. Shinker, “JJ”
Univ of Oregon Climate Lab
The NCEP / NCAR
REANALYSIS PROJECT
DATASET
http://www.cdc.noaa.gov/cdc/data.ncep.reanalysis.html
The assimilated data are:
-- computed by the reanalysis
model at individual gridpoints
-- to make gridded fields
extending horizontally over the
whole globe
-- at 28 different levels in the
atmosphere.
(Some of these levels correspond to
the "mandatory" pressure height
level at which soundings are taken,
e.g., 1000, 850, 700, 500, 250 mb,
etc.)
The horizontal resolution of the gridpoints is based on the T62
model resolution (T62 = "Triangular 62-waves truncation") which is
a grid of 192 x 94 points, equivalent to an average horizontal
resolution of a gridpoint every 210 km.
The pressure level data are saved on a 2.5 latitude-longitude grid.
Note that the gridpoints for computed model output are more
numerous and much closer together in the mid and high latitudes,
and fewer and farther apart over the low latitudes.
Map of locations of Raobs soundings for the globe:
Raobs = rawindsonde balloon soundings
Reanalysis Output Fields
The gridded output fields computed for different
variables have been classified into four classes (
A, B, C, and D) depending on the relative
influence (on the gridded variable) of:
(1) the observational data
(2) the model
IMPORTANT: "the user should exercise
caution in interpreting results of the
reanalysis, especially for variables classified
in categories B and C." (p 448)
Class A = the most reliable class of variables;
"analysis variable is strongly influenced by observed
data"
value is closest to a real observation
Class A variables:
mean sea level pressure,
geopotential height (i.e. height of 500 mb surface,
700 mb surface, etc.),
air temperature,
wind (expressed as two vectors dimensions: zonal
= u wind (west-east ) and meridional = v wind
(north-south),
vorticity (a measure of rotation)
Class B = the next most reliable class of variables
"although some observational data directly affect
the value of the variable, the model also has a very
strong influence on the output values."
Class B variables:
surface pressure,
surface temperature (and near-surface 2-m
temperature) ,
max and min temperature,
vertical velocity,
near-surface wind (u & v wind at 10 m),
relative humidity, mean relative humidity,
precipitable water content, and snow cover
Class C = the least reliable class of variables
-- NO observations directly affect the variable and it is
derived solely from the model computations
-- forced by the model's data assimilation process, not
by any real data.
Class C variables:
precipitation,
snow depth,
soil wetness and soil temperature,
surface runoff,
cloud fraction (% high, middle, low),
cloud forcing, skin temperature, surface wind
stress, gravity wind drag,
and latent and sensible heat fluxes from surface or top
of the atmosphere.