The Role of large scale Vegetation and Land Use in Water Cycle and climate in Monsoon Asia
The Role of large scale
Vegetation and Land Use in
Water Cycle and
climate in Monsoon Asia
By: Jannat Iftikhar 16
Nimrah Zahid 17
Summayya Tahir 18
Salma Shehzadi 19
Tayyaba Latif 20
• Monsoon is traditionally defined as
“a seasonal reversing wind accompanied by corresponding
changes in precipitation”.
• But now it is used to describe seasonal changes in
atmospheric circulation and precipitation associated with the
asymmetric heating of land and sea.
Major Monsoon Systems
• The major monsoon systems of the world consist of
a) The West African and Asia-Australian monsoons.
b) The North and South American monsoons.
c) Asian monsoon
Indian monsoon (South-Asian)
Asian Monsoon as a Huge Water
• Well known land-atmosphere-ocean system.
• Two water channels
a) From Tibetan Plateau to Indian Ocean
b) From Tropical Pacific Ocean towards east and southeast
• This monsoon transports huge amount of water vapours over
south, southeast and east Asia.
• This plays an essential role in maintaining cumulus convection
and precipitation over “monsoon Asia”.
• Which reinforces the monsoon circulation system through
latent heat release.
Impacts of Monsoon
• Monsoon circulation results in cool, dry winters and warm,
wet summer over the continents.
• This humid monsoon climate maintains dense vegetation zone
called “the green belt”. (from tropical southeast Asia to sub-
• Changes in this convectively active region can result in severe
draught, or flood over the large densely populated regions.
• Most important factor for life on land
vegetation and water resources
• Origins: Tropical monsoon Asia, water vapour transport with C
should be moisture source
• Data from analysis of atmospheric water balance by ECMWF
revealed time space characteristics of P C E relationship.
• Humid tropics: Both C and E contribute, C is main source
• The Indian sub- continent and indo china peninsula, C is larger
• In mid to high latitudes: E is source, P is far smaller than in
• Contribution of E to P suggests the essential role of vegetation
in surface water balance by transpiration
• Tropics: C plays role in P, E from vegetative surface is equally
important, compare to mid/ high latitudes.
Is monsoonrainfall decreasing?
Impact of deforestationon watercycle
In Thailand rainfall in late monsoon show a remarkable trend
•Decrease in rainfall
•Change the surface water balance
•Change the vegetation
• According to recent model decreasing trend of
September rainfall may be due to recent deforestation in
Thailand which likely to induce
• Reduction of surface roughness
• Evaporation efficiency
• Increase of albedo
• Which result
Sensible heat and surface heat
• Sensible heat is a thermal energy whose transfer to or
from a substance results in a change of temperature.
• When the Sun warms the Earth, warm air rises into the
atmosphere. As it rises, it expands and cools. Water
vapor condenses out of the cool air to form a cloud, this
is called surface heat.
• Change in surface heating, affects the atmospheric
stability, cumulus convection and rainfall.
• However the effect of deforestation decreasing rainfall is
noticeably only in September when southern monsoon
current has become week.
• In July and August when monsoon current is still strong it
tend to change the distribution of rainfall rather then
decrease the overall rainfall amount over the deforested
Do Water-FedRice PaddyFields Increase
Rainfallin Monsoon Asia?
• Rice paddy fields occupy a huge area in Southeast and East
• Southern China
• Deforestation and widespread mixed shrub/paddy fields
• Water-fed paddy fields increase evaporation compared to
drier farmland and fields.
• In June and July, the China plain is strongly affected by the
Meiyu (or Baiu in Japanese) frontal activity, which is a major
part of the Asian monsoon system in East Asia.
• The southwest monsoon current from South and Southeast
Asia is a main moisture source for rainfall in the Meiyu frontal
• Based upon cloud-resolving meso-scale model:
Water-fed paddy fields latent heat flux dominates
Farmland sensible heat flux dominates
Fig. Land use affects rainfall: simulations by Shinoda and Uyeda (2001) show that where rice
paddy fields exist (upper graph), the atmospheric boundary layer becomes wetter than that for
the farmland (lower graph), and deep convection easily develops to produce strong rainfall
Taiga-permafrost system in
• It is well known that one climatic zone corresponds well with
one dominant vegetation type.
• However, we should also note that vegetation over a broad
region effects the atmosphere and also the climate of a
• This implies that we should
consider vegetation and climate
as an interactive system rather
than one way relation from one
• Eastern Siberia is a broad
permafrost zone and taiga
forest is distributed on it.
• Long-term energy and water flux
measurement in typical Taiga
forest of Lena river basin has
revealed some interesting
features in the seasonal change
of this eco-climate system.
• The east Siberia has the Lena
river that starts from south and
ends in north in Arctic sea.
• It is the 11th longest river in the
world and the 3rd largest river in
• In spring snow melt occurs from April to May but sensible heat flux
was dominant and latent heat flux was very small or negligible.
• The latent heat flux suddenly increased in June when foliation of
• Now question arises that why did evapotranspiration started so
• The best answer to it is that the melting process of the permafrost
and root depth are likely to be closely related to this problem.
• When depth of melted layer reached 20cm where a large portion
of larch roots are present the foliation and transpiration from the
leaves may have started.
• On the other hand we noted that most water vapor for
precipitation in summer is occupied by evapotranspiration from
surface of this area implying that most water is recycling
between vegetation and atmosphere in summer.
• The hydro-meteorological studies in Siberia have strongly
suggested a symbiotic system of climate and vegetation
through the hydrological cycle, where Taiga maintains itself by
recycling water between atmosphere and vegetated surface of
• While the permafrost is also maintained by the Taiga through
suppressing sensible heating in summer.
• This rapid Global warming in Siberia which may be inducing
melting of permafrost may affect this “ Taiga-permafrost