Importance of the atmospheric boundary layer (2)

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Importance of the atmospheric boundary layer (2)
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Review of last lecture

• The mission of meteorology is to understand and
  predict weather- and climate-related disasters
  (e.g. tornados, hurricanes, El Nino and global
  warming).
• The modern climatology (meteorology) was born in
  the 1940s (a very young science!), but has been
  growing very fast! Now we have a global
  observational network with many satellites,
  ships, radars and surface stations, as well as
  very comprehensive prediction models running on
  the worlds largest computers.
• The current status of weather and climate
  predictions (1) weather prediction good to 10
  days, (2) tropical cyclone prediction good in
  track but not in intensity, (3) climate
  prediction good to two seasons, (4) climate
  change projections have a 3-fold difference in
  magnitude.

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Why is it so difficult to understand and predict
weather and climate?
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Problem I Different parts of the world are
strongly connected to each other (The
Teleconnection Problem)
(Lin et al. 2006, Journal of Climate)
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Example Remote impacts of Amazon deforestation
2006
2002
From Werth and Avissar
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Problem II Different components of the earth
system (atmosphere, land, ocean, ice, clouds,
etc) are strongly interacting with each other
(The Feedback Problem)
(Lin 2007, Journal of Climate)
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Problem III The earth system composes of both
very big objects (such as the whole Pacific
Ocean) and very small objects (such as the cloud
droplets), making it very difficult to draw them
on the same page (The Subgrid-Scale
Problem)
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Vertical Structure of the Atmosphere

• Definition of the atmospheric boundary layer
  (ABL) "that part of the troposphere that is
  directly influenced by the presence of the
  earth's surface and responds to surface forcings
  with a time scale of about an hour or less.
• Scale variable, typically between 100 m - 3 km
  deep

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Importance of ABL(1) Interface between
atmosphere and ocean/ land/ice - flux transfer
and feedback
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Importance of ABL(2) The human beings are
living in the ABL and changing the climate system

• Release of greenhouse gases
• Release of pollutants (aerosols)
• Change of land cover (deforestation and
  afforestation)

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Importance of ABL(3) A basic subgrid-scale
process
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Summary

• The main reasons of the difficulties in weather
  and climate predictions (1) Teleconnection
  problem, (2) Feedback problem, and (3)
  Subgrid-scale problem.
• Importance of the ABL (1) interface between
  atmosphere and ocean/land/ice - flux transfer and
  feedback, (2) the human beings are living in the
  ABL and change the environment, (3) a basic
  subgrid-scale process