Land Surface - Outline

Climate Role

Surface Energy Balance

Surface Water Balance

Vegetation (Canopy)

Soil (moisture)

Climate Roles of Land Surface

greenhouse gas emissions

      è affects global energy and biogeochemical cycles

creation of aerosols

      è affects global energy and water cycles

surface reflectivity (albedo)

      è affects global energy cycle

impacts on surface hydrology

       è affect global water cycle

Potential Evaporation

The potential evaporation is defined as the maximum possible evapotranspiration for the prevailing atmospheric condition.

PE is the amount of moisture the atmosphere demands based upon its energy status.

If there is a higher energy level in the atmosphere, e.g. very high temperature due to intense solar radiation, it demands more moisture from the Earth’s surface.

If PE > available evapotranspiration è leads to dry surface

PE < available evapotranspiration è leads to runoff.

Root Zone and Soil Storage

Climate interacts only with water that is on the surface or in the soil water zone.

The soil water zone extends downward to the depth penetrated by the root of the vegetation.

Soil storage capacity (field capacity of the soil) is the amount of moisture the soil can hold.

If soil water content increases above the capacity, gravitational forces carry the water downward to the water table, where it becomes groundwater.

Land Surface Properties

Vegetation Properties

       Type and density

Soil Properties

       Depth and physical properties

      (e.g., moisture)

Characteristics of Vegetation Canopy

Typical Height

Leaf Area Index (LAI)

Leaf area index (LAI) is ratio of the total area of all leaves (one-side) on a plant to the area of ground covered by the plant.

It defines the area that interacts with solar radiation and that is responsible for carbon absorption and exchange with the atmosphere.

Idealized Canopy

Canopy – The collection of vegetable matter covering the land surface is called the plant canopy.

Over moist regions, most of the water transferred from soil to atmosphere moves through vegetation.

Water moves into the roots, through the plant parts to leaves, and passes into the atmosphere through stomata.

Root and stomata control the exchanges between the vegetations and the atmosphere.

The idealized canopy is used to quantify the vegetation-atmosphere fluxes via LAI and leave and atmosphere properties.

Land Surface Model

Soil Moisture Content

Cryosphere

Why is Ice Important to Climate?

Surface ice of any depth is a much more effective reflector of solar radiation than the underlying surface.

Sea ice is a good insulator and allows air temperature to be very different from that of the seawater under the ice.

At present, year-round ice covers 11% of the land area and 7% of the world ocean.

Sea Ice

One major climate effect of sea ice is to seal off the underlying ocean from interaction with the atmosphere.

Without an sea ice cover, high-latitude oceans transfers large amount of heat to the atmosphere, especially in winter.

With an sea ice cover, the heat flux into the atmosphere is stopped. In addition, the ice surface absorbs little incoming solar radiation. Winter air temperature can cool 30°C or more near a sea-ice cover.

Land Ice

Ice and Sea Level

The Antarctic Ice Sheet holds the equivalent in seawater of 66 meters of global sea level.

The Greenland Ice Sheet holds the equivalent of 6 meters of global seawater.


	Climate Role
	Surface Energy Balance
	Surface Water Balance
	Vegetation (Canopy)
	Soil (moisture)


	greenhouse gas emissions
	è affects global energy and biogeochemical cycles
	creation of aerosols
	è affects global energy and water cycles
	surface reflectivity (albedo)
	è affects global energy cycle
	impacts on surface hydrology
	è affect global water cycle


	The potential evaporation is defined as the maximum possible evapotranspiration for the prevailing atmospheric condition.
	PE is the amount of moisture the atmosphere demands based upon its energy status.
	If there is a higher energy level in the atmosphere, e.g. very high temperature due to intense solar radiation, it demands more moisture from the Earth’s surface.
	If PE > available evapotranspiration è leads to dry surface
	PE < available evapotranspiration è leads to runoff.


	Climate interacts only with water that is on the surface or in the soil water zone.
	The soil water zone extends downward to the depth penetrated by the root of the vegetation.
	Soil storage capacity (field capacity of the soil) is the amount of moisture the soil can hold.
	If soil water content increases above the capacity, gravitational forces carry the water downward to the water table, where it becomes groundwater.


	Vegetation Properties
	Type and density
	Soil Properties
	Depth and physical properties
	(e.g., moisture)


	Typical Height

	Leaf Area Index (LAI)
	Leaf area index (LAI) is ratio of the total area of all leaves (one-side) on a plant to the area of ground covered by the plant.

	It defines the area that interacts with solar radiation and that is responsible for carbon absorption and exchange with the atmosphere.


	Canopy – The collection of vegetable matter covering the land surface is called the plant canopy.
	Over moist regions, most of the water transferred from soil to atmosphere moves through vegetation.
	Water moves into the roots, through the plant parts to leaves, and passes into the atmosphere through stomata.
	Root and stomata control the exchanges between the vegetations and the atmosphere.
	The idealized canopy is used to quantify the vegetation-atmosphere fluxes via LAI and leave and atmosphere properties.


	Surface ice of any depth is a much more effective reflector of solar radiation than the underlying surface.
	Sea ice is a good insulator and allows air temperature to be very different from that of the seawater under the ice.
	At present, year-round ice covers 11% of the land area and 7% of the world ocean.


	One major climate effect of sea ice is to seal off the underlying ocean from interaction with the atmosphere.
	Without an sea ice cover, high-latitude oceans transfers large amount of heat to the atmosphere, especially in winter.
	With an sea ice cover, the heat flux into the atmosphere is stopped. In addition, the ice surface absorbs little incoming solar radiation. Winter air temperature can cool 30°C or more near a sea-ice cover.


	The Antarctic Ice Sheet holds the equivalent in seawater of 66 meters of global sea level.
	The Greenland Ice Sheet holds the equivalent of 6 meters of global seawater.