Transcript Slide 1

Weather and Climate at A2
Major climate controls: The structure of the atmosphere, the atmospheric heat budget, the
general atmospheric circulation, planetary surface winds, latitude, oceanic circulation and
altitude.
The climate of the British Isles: Basic climatic characteristics: temperature, precipitation and
wind.
Air masses affecting the British Isles.
Origin and nature of depressions. The Weather changes associated with depressions.
Origin and nature of anticyclones. Associated weather conditions in winter and summer.
Storm events: their occurrence, their impact and responses to them. One case study from within
the last 30 years should be undertaken.
The climate of one tropical region (tropical wet/ dry savanna or monsoon or equatorial):
Basic climatic characteristics: temperature, precipitation and wind.
The role of sub-tropical anticyclones and the ITCZ
Tropical revolving storms. Their occurrence, their impact, management of the hazard and
responses to the event. Two case studies of recent (within the last 30 years) tropical revolving
storms should be undertaken from contrasting areas of the world.
Climate on a local scale: Urban - the urban heat island effect.
Precipitation: frequency and intensity, fogs, thunderstorms, and their relationship to urban areas
Air quality: particulate pollution, photochemical smog and pollution reduction policies.
Winds: the effects of urban structures and layout on variations in wind speed, direction and
frequency
Global climate change: Evidence for climatic change over the last 20 000 years.
Global warming – possible causes. Possible effects: globally, on the chosen tropical region (above)
and on the British Isles. Responses to global warming: international, national and local
Environmental
lapse rate=
decrease in
temperature with
altitude 6.4
degrees per 1km
http://ww
w.learner
.org/cour
ses/envs
ci/unit/te
xt.php?u
nit=2&se
cNum=2
With the aid of a diagram,
describe the structure of the
atmosphere. (8 marks)
Level 1 (1-4 marks) (Midpoint 3)
Simple statements/annotations of the
structure of the atmosphere. Naming of
terms with no development; or one zone
described well (likely to be the
troposphere). A basic diagram.
Level 2 (5-8 marks) (Midpoint 6)
Detailed description of at least two zones
within the atmosphere with some
development of each. Recognition and
description of three zones should
achieve maximum credit. Accurate/detailed
diagram.
No diagram = maximum 6 marks.
Defn ITCZ:
Near the equator, from about 5° north and 5° south,
the northeast trade winds and southeast trade
winds converge in a low pressure zone known as
the Intertropical Convergence Zone or ITCZ.
Solar heating in the region forces air to rise through
convection which results in high precipitation. The
ITCZ is a key component of the global circulation
system.
The equatorial region lacks a dry season and is
constantly hot and humid.
The location of the ITCZ varies throughout the year
and while it remains near the equator, the ITCZ
over land ventures farther north or south than the
ITCZ over the oceans due to the variation in land
temperatures.
The location of the ITCZ can vary as much as 40°
to 45° of latitude north or south of the equator
based on the pattern of land and ocean.
In Africa, the ITCZ is located just south of the Sahel
at about 10°, dumping rain on the region to the
south of the desert.
Also known as the doldrums by sailors due to the
lack of horizontal air movement (the air simply rises
with convection).. Or the Equatorial Convergence
Zone or Intertropical Front.
Winds
Wind is driven by the pressure gradient: air molecules move from areas of
high to areas of low pressure
What else influences climate?
•
•
•
•
Latitude
Altitude
Continentality
Oceanic circulation
Oceanic circulation- NADW
EL NINO AND LA NINA
In normal, non-El Niño conditions (top panel of schematic diagram), the trade
winds blow towards the west across the tropical Pacific. These winds pile up
warm surface water in the west Pacific, so that the sea surface is about 1/2
meter higher at Indonesia than at Ecuador. The sea surface temperature is
about 8 degrees C higher in the west, with cool temperatures off South America,
due to an upwelling of cold water from deeper levels. This cold water is nutrientrich, supporting high levels of primary productivity, diverse marine ecosystems,
and major fisheries. Rainfall is found in rising air over the warmest water, and
the east Pacific is relatively dry.
During El Niño, the trade winds relax in the central and western Pacific leading
to a depression of the thermocline in the eastern Pacific, and an elevation of the
thermocline in the west. This reduces the efficiency of upwelling to cool the
surface and cut off the supply of nutrient rich thermocline water to the euphotic
zone. The result is a rise in sea surface temperature and a drastic decline in
primary productivity. Rainfall follows the warm water eastward, with associated
flooding in Peru and drought in Indonesia and Australia. The eastward
displacement of the atmospheric heat source overlaying the warmest water
results in large changes in the global atmospheric circulation, which in turn force
changes in weather in regions far removed from the tropical Pacific. (Europe)
http://www.cpc.nc
ep.noaa.gov/prod
ucts/analysis_mo
nitoring/ensostuff/
ensoyears.shtml
http://www.pmel.noaa.gov/tao/elnino/ninohome.html
Explain how each of altitude and oceanic circulation influence climate.
(10 marks)
Level 1 (1-4 marks)(Midpoint 3)
Simple statements of influence of altitude and oceanic circulation on
climate. No specific detail or elaboration is provided; or discussion of
one aspect only.
Level 2 (5-8 marks) (Midpoint 6)
Both elements covered with specific or detailed statements of influence
of altitude or oceanic circulation on climate; may be still an imbalance of
influence.
Level 3 (9-10 marks) (Midpoint 9)
A fully developed answer, with good elaboration and explanation of a
range of influences, with both elements reaching a Level 2 response.
The answer demonstrates both breadth and depth of understanding
There have been no other short mark questions on this section
of the specification apart from the ones in this PowerPoint so
will next year be the lucky year…
Weather Essay Questions
•
•
•
•
•
•
‘The Earth has a fever, and the fever is rising…. We are what is wrong, and
we must make it right.’ (Al Gore, 2007) In the context of global warming,
discuss the extent to which you agree with this statement. (40 marks)
Large cities .... have their own climatic conditions.’ (Andrew Goudie) To
what extent is this true? (40 marks)
Assess the relative roles of sub-tropical anticyclones and the inter-tropical
convergence zone in creating the characteristic features of the climate of
one tropical region that you have studied. (40 marks)
To what extent can preparedness and planning mitigate the effects of
tropical revolving storms? (40 marks)
To what extent do urban areas modify their climate? (40 marks)
“Up and down, up and down – that is how temperature and climate have
always gone in the past and there is no proof they are not still doing exactly
the same now. In other words, climate change is an entirely natural
phenomenon, nothing to do with the burning of fossil fuels.” David Bellamy
Discuss the extent to which you agree with this statement. (40 marks)
To what extent is oceanic
circulation the main driving force
behind the Earth’s climate -40
marks
•
•
•
•
•
What are the key points?
What needs to be in your introduction?
What else do you need to cover?
‘to what extent’ so…?
What will your conclusion be?