Transcript Slide 1

MICROCLIMATE EFFECTS ON ATMOSPHERIC
CARBON DIOXIDE
GROUP WORK BASED ON THE PRAIRIE RIDGE
PROJECT
MEA 760: BIOGEOCHEMISTRY
WILFRED AKAH
September 21, 2006
Climate and Climate Processes -
Why climatology:
• climate as a constraint for geological processes
• climate as a constraint for environmental/
ecological/evolutionary processes
• climate as a constraint for human society
• understanding the climate system is a prerequisite for
understanding the anthropogenic impact on environment and
climate
Climate:
“Climate is the set of weather conditions typical of a given
region together with the frequency of these conditions and
their seasonal variations.” (Monin 1986)
Thus: “climate” denotes the mean weather and the statistical
weather distribution of a certain area as determined over a
certain number of years (frequently 30 years; reference
climate: 1931-1960).
Present-day climate is a result of the interaction of various
components and factors. Climate conditions at a location is
suitably described by the parameters:
• Solar radiation
• Temperature
• Precipitation and
• Air pressure
(Dommergues, 1979)
Climate classification
The generic climate classifications of Flohn (1950) regards:
1. Equatorial westerly zone: constantly wet
2. Tropical zone, winter trades: summer rain
3. Subtropical dry zone (trades or subtropical high)
4. Subtropical winter-rain zone: winter rain
5. Extra-tropical westerly zone: precipitation through the year
6. Subpolar zone: less precipitation through the year
7. High polar zone: sparse precipitation, summer rain, early
winter snow
Relevant climate parameters:
• mean annual temperature (MAT)
• mean temperature of the coldest month (CMT)
• mean temperature of the warmest month (WMT)
• mean annual precipitation (MAP)
• mean precipitation of driest month
Spatial Scales of Climate:
• Microclimate: mm to 100 m
• Mesoclimate: 100 m to 100km
• Macroclimate: 100 km to 10,000 km
Climate system:
“Atmosphere, land, ocean, ice and biosphere together form the
climate system.” (IPCC 1995)
The climate system is influenced by extraterrestrial factors, in
particular by solar radiation.
Components of the Climate System and External Factors
External Factors:
• The Sun
• Geometry and Orbital Parameters of the Earth
Components of the Climate System:
• Atmosphere
• Land
• Ocean
• Ice
• Biosphere
Average Composition of the Atmosphere (below 25 km, dry air):
• Nitrogen, N2
78 vol.% (dry air)
• Oxygen, O2
20.95
• Argon, Ar
0.93
• Carbon dioxide, CO2
• Neon, Ne
0.035
350 ppm
0.0018
• Krypton, Kr
0.0011
• Helium, He
0.0005
• Methane, CH4
0.00017
1700 ppb
Greenhouse Gases (Data from 1991)
Gas
Concentration
Increase/a
CO2
355(280)ppm
0.5%
CH4
1.7(0.8)ppm
0.9
CFM
0.3(0)ppb
4%
N2O
0.31(0.29)ppb
O3
30(?)ppb
0.25%
1%(?)
Global Cycles of Atmospheric Greenhouse Gases: Carbon
Reservoirs (pre-industrial/recent):
• Atmosphere: 600/750 Gt C
• Land Biota: 610/550 Gt C
• Soil/Detritus: 1560/1500 Gt C
• Marine Biota: 3/3 Gt C
• Ocean:
– surface: 1000/1020 Gt C
– DOC: 700/700 Gt C
– interm. & deep: 38000/38100
Humidity and precipitation
Humidity: Measurement of the proportion of water vapor in the
atmosphere (relative and absolute). Humidity depends on
temperature. The higher air temperature is, the more water vapor
can be incorporated.
Important processes which can change humidity:
Evaporation:
• Energy supply causes change from liquid water to water vapour at
temperatures below the boiling point
Condensation:
• Occurs when relative humidity is 100% and temperature further
decreases, leads then to condensation, clouds and likewise to
Precipitation
Freezing:
• Temperature decrease below 0°C in the atmosphere
Anthropogenic
Concentration of greenhouse gases since 250 years
Tropical forest
Agriculture
Energy
Chemistry
Destruction of forest
Air pollution: CO2, NO2,
Production, application
Co2 and other trace gases
Cox, CH4
CFC
Fertilization: N2O, CH4
Estimated sources of CO2 and CO2 cycle
• CO2 in Relation to Plants
At the photosynthesis level, there are three main plant groups
C3, C4, and CAM (Craussulacean Acid Metabolism) plants.
• Examples of C3 plants Soybean, wheat, rice, and potato.
• The C4 pathway is found in tropical grass crops like corn,
sugarcane, sorghum and some members of the families
Chenopodia Ceae and Arnaranthaceae.
• The C4 plants are more efficient in photosynthesis than the C3
plants.
• In C3 plants, 20-50 % of the carbon fixed is immediately lost
by photorespiration.
• In contrast, C4 plants exhibit little photorespiration.
In comparison to these two plant types, the CAM plants are a form
of C4 except that the CO2 is fixed at night and then processed via a
C3 pathway during the day.
CAM plants include pineapple and succulent vegetation like Cacti
and stone crops: they are highly efficient users of water.
Temperature change in the Atmosphere:
• Mid-tropospheric (850-300mb) temperatures have increased between
the 1970s and 1990s, in parallel with surface temperature.
• In the upper troposphere (300-100mb) there has been a steady
decline in temperature of about 0.4°C since the 1960s.
• Temperatures in the lower stratosphere (100-50mb) show the greatest
change, especially since 1980. It is mostly attributed to changes over
and
around Antarctica, probably related, in part, to the decrease in
springtime
stratospheric ozone.
Precipitation, cloud cover and sea-level change:
• With globally increasing temperatures, increases in global
precipitation would be expected due to the greater rates of
evaporation of sea surface water.
• Observations however, show for the last few decades an increase in
the mid-latitudes, decrease in the Northern Hemisphere subtropics
and increase throughout the Southern Hemisphere.
• Increased global cloudiness also would be an expected consequence
of higher global temperatures.
• Over Europe, Australia, Indian sub-continent and North America
annual mean cloudiness has increased by 6% to 10%.
• Increasing greenhouse gases are expected to cause a rise in the
global mean sea level, due partly to oceanic thermal expansion and
partly to the melting of land-based ice masses.
Prediction of future climate change is assessed when using
simulation models which include components of the climate system
and their physical features. Mostly, General Circulation Models
(GCM) are used. Associated with a doubling of pre-industrial
atmospheric CO2, the following conclusions have been made:
• A global average warming at or near the Earth's surface of between
1.5 and 4.5°C, with a "best guess" of 2.5°C, will occur
• The stratosphere will experience a significant cooling
• Surface warming will be greater at high latitudes in winter, but less
during the summer
• Global precipitation will increase by 3% to 15%
• Year-round increases in precipitation in high-latitude regions are
expected, whilst some tropical areas may experience small decreases