Download Unit 4 - Climate

CROP PRODUCTION
Unit 4: Climate
Climate (p. 97)

Weather
– Short term status of atmospheric conditions
– Processes involved in establishing
weather/weather patterns = meteorology

Climate
– Average weather and variations over time
– Study of climate = climatology
Climate (97)
Eight major factors in determining crop distribution:
1. Temperature


Influenced by latitude, elevation, and water bodies
Determine temperature extremes and number of frost free days
2. Humidity
3. Precipitation
–
4.
5.
6.
7.
8.
Examples: snow, sleet, rain, hail
Weather Patterns
Solar radiation
Wind
Topographic features
Social/political factors
(First three determine moisture availability and
heat/moisture stress on crops)
Profile of the Atmosphere
(p. 98)
Layer
Depth
Actions
Troposphere
0-10 miles
Weather events, clouds, jet stream
Stratosphere
10-31 miles
Ozone layer protects from UV rays
Mesosphere
31-53 miles
Temperature decreases w/height
Thermosphere 53-310 miles
Warmest layer
Exosphere
>310 miles
Atoms/molecules escape earth’s gravity
into space
Ionosphere
37-620 miles
Electrified, reflects radio waves back to
earth
Troposphere (99)

Air will move upward if:
– Temperature increases
– Air pressure decreases
– Air has more water vapor

Rising air cools at the rate of 1° C per 100
meters
– As air cools, water vapor condenses
– If humidity is high, condensation will begin at
higher temperatures
Troposphere (99)

Air will move downward if:
– Temperature decreases
– Air pressure increases
– Air has less water vapor
Descending air warms at the rate of 1°
C per 100 meters
 Warmer air holds more moisture than
cooler air

Precipitation (99)

Distribution patterns
– Geographic cropping regions:
 Arid (0-25 cm/yr)
 Semiarid (25-50 cm/yr)
 Sub-humid (50-75 cm/yr)
 Humid (75-100 cm/yr)
 Per-humid (100+ cm/yr)
Precipitation (99)

Distribution patterns
– Monthly – look at:
 Precipitation vs. crop water needs
 Soil-saturated moisture
 Transpiration rate
– Monthly—consider:
 12” precipitation will grow wheat in ND and sparse
grazing in TX
– Increase production by fallowing in
arid/semiarid regions
World Climate
Temperature (p. 101)

Inversion
– Air near the ground is cooler than the air above

Cardinal temperatures
– Varies for different crops
– Minimum
 Lowest temp required for growth or process
– Optimum
 Temp required for best growth/process
– Maximum
 Highest temp limit for growth/process
– Within range, growth rate doubles for every 10° C
increase in temperature (see chart p. 102)
Temperature (p. 103)

Hopkins Bioclimatic Law
– Events such as planting, harvesting, etc. are delayed
 4 days for one degree latitude north,
 5 degrees longitude east, and
 400 feet in altitude

Growing season requirements for major crops:
–
–
–
–
–
Corn—120 days
Oats—90 days
Barley—80 days
Sugarcane—450 days
Cotton—180 days
Temperature (103)

Heat Units
– Used to measure plant development
H.U. = daily min. temp. + daily max temp – base temp
2

Base temp for major crops
– Corn: 50° F
– Soybeans: 50° F
– Sorghum & Cotton: 60° F
– Small Grains: 40° F
Temperature (103)

Growing Degree Days (GDD)
– Place minimum and maximum daily temperature limits;
provides a “calendar” for physiological maturity
GDD = daily min. + daily max. – critical min. temp.
2
– Critical max for corn is 86° F
– Critical min for corn is 50° F
– GDD can never be negative
– Used especially in vegetables, hybrid seed production,
and crop scouting (insects & weeds)
Sample Calculations
Day
Min
temp
Max
temp
1
45
62
2
50
65
3
54
68
4
55
74
5
60
80
Totals:
GDDs
HUs
More Sample Calculations
Day
Min
temp
Max
temp
1
49
62
2
52
72
3
56
81
4
60
82
5
64
89
Totals:
GDDs
HUs
Temperature (103)

Other types of degree days…
– Cooling Degree Days
 Measure air conditioning bill
– Heating Degree Days
 Measure heating costs
– Stress Degree Days
 Same as GDD, but 86° F is base
Humidity (104)
Evapotranspiration
 Relative Humidity

– Amount of water in the air compared to the
total water the air could hold at a given
temperature

Vapor Pressure
– Pressure caused by presence of water vapor
molecules in the air

Vapor Pressure Deficit
– Drying power of the air
Weather Patterns (105)
High Pressure Cells
“Anticyclonic”
Low Pressure Cells
Movement
“Cyclonic”
Clockwise
Circulation
Sinking & away
from center
Air Movement
CounterClockwise
Rising & towards
center
Few
Cloud Cover
Many
Little
Precipitation
Much
Weather Patterns (106)

Air mass
– Large body of air essentially uniform in
horizontal directions

Four major masses are described by
origin:
1.
2.
3.
4.
c – originate over land = continental
m – originate over water = maritime
P – cool or cold = polar
T – warm or hot = tropical
Weather Patterns (106)
So…how would you describe each of the
following air masses?
– cP
 Dry, cool
– mP
 Moist, cool
– cT
 Dry, warm
– mT
 Moist, warm
Weather
Patterns
(107)

Weather front
– Two or more air masses with different properties collide and
create an area of instability in the boundary zone
– Cold Front
 When a cold air mass replaces warm air, pushing it upwards;
thunderstorms and showers result
– Warm Front
 When a warm air mass replaces cold air and moves higher; if air is
moist, widespread precipitation results
– Occluded Front
 A composite of two fronts; usually result in cool, drizzly weather
Weather Patterns (108)

Surface features affect weather
– One example
 Mountains forcing air to rise, resulting in
precipitation on the windward (upwind) side and
drier climate on the leeward (downwind) side
– Northern Hemisphere
 Usually find dry/arid regions on the east side of
the mountain because weather patterns move
west to east
Climatic Change (109)

Microclimate
– Crop environment

Macroclimate
– Can also be affected by human activity
– Greenhouse Effect

Four gases have increased due to human activity
1.
2.
3.
4.
Carbon dioxide
Methane
Nitrous oxide
Chloroflourocarbons
Climatic Change (110)

Effects of greenhouse gases/human activity
– Acid rain
 Resulting from sulfur pollution
– Desertification
 Expansion of deserts due to mis-use of land
– Deforestation
 Greed of ag producers
Cirrus Clouds
Occurring at
elevations of
20,000-40,000 feet
 Cirrostratus or
cirrocumulus

Cumulous Clouds
Clouds that are
vertically developed
 Causes severe
weather
 Cumulonimbus


Website resources
– http://ww2010.atmos.uiuc.edu/(Gh)/home.rxml
– http://en.wikipedia.org
– http://www.geographic.org/maps/maps.html

Chapter 4
– Review Questions (p. 112-113)
– Thinker