RASAKUMAR M.Sc (agri)

1. GLOBAL PATTERNS OF THE
CLIMATIC ELEMENTS:
(1) SOLAR ENERGY
(Linked to solar insolation
& R, net radiation)

2. 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
highest values occur over subtropical deserts.

3. REVIEW OF
INSOLATION

8. DURATION

11. INTENSITY

12. RADIATION /
ENERGY BALANCE
Q* = ( K↓ - K↑ ) + ( L↓ - L↑ )
where K↓ = direct + diffuse shortwave
solar radiation

14. Kiehl and Trenberth (1997) BAMS

15. Trenberth et al. (2009) BAMS

16. 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.

17. Net short-wave radiation =
Positive values represent
energy moving towards the
surface, negative values
represent energy moving
away from the surface.

18. SW absorbed =
Function of
INTENSITY &
DURATION & sun
angle / albedo

19. Net long-wave radiation =
Positive values represent
energy moving towards the
surface, negative values
represent energy moving
away from the surface.

21. Net Surplus

22. Annual mean absorbed solar radiation,
emitted longwave radiation (OLR) and net
radiation by latitude

23. S = Solar radiation T = Terrestrial radiation

24. Net Radiation =
Positive values represent
energy moving towards the
surface, negative values
represent energy moving
away from the surface.

26. 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.

27. 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.

28. 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.

29. 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.

31. Humid Tropical /
Equatorial
rainforest
Tropical
desert
R net
LE
H
R net
LE
H

32. Tropical wet-dry climate
Grassland /steppe climate
Tropical wet climate
Tropical desert
climate

33. 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.

35. 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.

36. GLOBAL PATTERNS OF
THE CLIMATIC ELEMENTS:
(2) TEMPERATURE

37. 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

38. 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

39. 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
2. Land vs. water thermal contrasts

40. 3. Warm and Cold Ocean Currents

41. 4. Elevation

42. 5. Ice /Snow Albedo & Other Effects

43. 6. Prevailing atmospheric circulation
Temperatures are affected by the temperature
"upwind" -- i.e. where the prevailing winds and
air masses originate

44. 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.

45. JANUARY JULY
Northern Hemisphere
Southern Hemisphere

46. Southern Hemisphere
Northern Hemisphere
JANUARY JULY

50. http://geography.uoregon.edu/envchange/clim_animations/
Constructed by:
Jacqueline J. Shinker, “JJ”
Univ of Oregon Climate Lab

51. The NCEP / NCAR
REANALYSIS PROJECT
DATASET
http://www.cdc.noaa.gov/cdc/data.ncep.reanalysis.html

52. 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.)

53. 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.

54. Map of locations of Raobs soundings for the globe:
Raobs = rawindsonde balloon soundings

55. 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)

56. 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)

57. 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

58. 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.