Transcript Air Masses/Fronts, El Nino/La Nina

Week 8 Notes
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Weather Review
Term Paper Outline Guidelines
AMS Climate Change Policy (HW#6)
Airmasses and Fronts (Chp 8)
El Niño Classwork (HW#7)
El Niño and La Niña
• March 24 – No Class (Spring Break)
• March 31 – No Class (Cesar Chavez Day)
Week 8 Notes (cont’d)
• April 7
– Remote Sensing
– Weather Forecasting
– Review for Midterm #2
• April 14
– Midterm #2
– Term paper Outlines Due
• April 21
– Thunderstorms and Tornadoes
Term Paper Outline
Due Apr 14
• Typed
• Double Spaced
• Formatted per next page
• References
• At Least 3 references
• You can add more references later
• Only 1/3 Internet only sources
• Proper formatting for electronic sources
• APA Format only (link in Syllabus)
Term Paper Outline
I. Introduction
II. Three Major Points
A. Point 1.
1. Subpoint 1
2. Subpoint 2
B. Point 2.
1. Subpoint 1
2. Subpoint
C. Point 3.
1. Subpoint 1
2. Subpoint 2
III. Summary
References:
At Least 3 references
APA Format only (link in Syllabus)
Only 1/3 Internet Sources (and properly formatted)
Sample Term Paper Outline
I. Introduction
A. Performed by Committee of Citizens named by Board of Educ.
B. Findings:
1. Unsatisfactory sports facilities
2. Ongoing traffic and parking congestion.
3. Outdated science labs
4. Outdated physical facilities:
II. Funding Sources:
A. Bond referendum passed by votes of four sending towns on 12/9/03.
B. Breakdown:
1. $8.8 million provided by communities via increased taxes.
2. $6.3 million provided by State of NJ via school funding pool.
C. Timetable for Expenditures:
III. Benefits to School and District:
A. Reduction of Special Education costs by keeping students at school.
B. Maintenance of Property values for sending district real estate.
C. Enhancement of education program at the school.
IV. Drawbacks to School and District:
A. Increased property taxes to residents for 15-20 years to pay off bond.
B. Disruption of academic programs at Gateway during the period of construction.
C. Re-location of sporting events and some programs during renovations.
V. Conclusion: Although there will be some costs involved and some disruption, believe the benefits
of renovating Gateway H.S., with substantial funding from the State of N.J., are in the best interests of
all students and residents.
CLIMATE CHANGE POLICY
• IPCC - Intergovernmental Panel on Climate Change
• Set up by World Meteorological Organization (WMO)
• IPCC Fourth Assessment Report 2007
• 1000+ Scientists
• Synthesis of Exisitng Research
• No Actual research or Data Collection
• AMS – American Meteorological Society
AMS CLIMATE CHANGE POLICY - HW#6
Divide into SIX GROUPS
• Read individually your section
• Discuss as a group
• Come up with at least one “bullet point” per paragraph
• Choose a group spokesperson who will present to the class
• Each group will turn in a sheet of paper with members names
CLEARLY WRITTEN
Group:
• #1 – Background
• #2 – How is Climate Changing?
• #3 – Why is Climate Changing?
• #4 – How Can Climate Change be Projected in the Future?
• #5 – How will Climate Change in the Future? (First 4 paras)
• #6 – How will Climate Change in the Future? (Last 4 paras)
Air Masses and Fronts
Air Mass Development
Semi-permanent circulation patterns provide
consistent wind patterns and breeding grounds for
air masses.
Air Mass Properties
•
•
•
•
Take on the properties of the underlying surface
Characterized by Temperature and Humidity
Classified by location of “origin”
Geographically
– Tropical
– Polar
– Arctic
• Surface Properties
– Maritime
– continental
• Characteristics more prevalent if air mass remains
over source region for a long period
Air Mass Classifications
• cP - continental Polar
– Cold, dry, stable
– Extremely cold cP air mass may be designated cA
(continental Arctic)
• mP - maritime Polar
– Cool, moist, unstable
• mT - maritime Tropical
– Warm, moist, usually unstable
• cT - continental Tropical
– Hot, dry
– Stable air aloft, unstable surface air
• cA – continental Arctic
Air Mass Source Regions
Continental Polar (cP)
– Cold, Dry
– Develops over the interior of
• North America -- Central Canada -- Siberia
Arctic Air (cA)
– Bitterly Cold and Very Dry
– Develops over the snow or ice usually north of 60° N
Marine Polar (mP)
– Cold, Moist
– Source: Cold ocean waters of the North Pacific and North Atlantic
– Often conversion of cP Siberian air to mP which is moistened and
warmed from the Japanese “Gulf Stream Current”
– Major type for storms to affect N. California and the Pacific NW
– Responsible for fueling “Nor-easters”
Tropical (T)
• Continental Tropical (cT)
– Hot, Dry
– Source: Deserts of Mexico and the SW United States
– Very unstable because of heat and convection, but
cloudless because of lack of moisture.
• Marine Tropical (mT)
– Warm, Humid
– Source: Tropical and subtropical oceans and the Gulf
of Mexico
United States Air Masses
Example Air Masses
cP
mT
Air Mass Invasion
Air Mass Modification
• Air masses eventually move
• If it moves over a region different from where it
originated, the air mass will be modified, by the
land that the air is travelling over.
• Changes: warming, cooling, adding or reducing
moisture content
Air Mass Modification
cP
The cP air mass will
be warmed by the
warmer land that it
passes over.
Warmer
Land
Air Mass Modification
• Originates as cP air from Asia and is carried across the
Pacific becoming mP
mP
cP
Lake Effect Snow
Fronts
• Fronts
– Narrow transition zone between air masses
of differing densities.
– The density differences usually arise from
temperature differences.
– Density differences may be a result of
humidity differences (summer).
• A front is the boundary or transition zone
between different air masses.
Frontal Symbols
Cold Front
• Cold Front
– Boundary with a colder (more dense)
airmass advances and displaces the
warmer (less dense) air.
– The largest temperature differences are
normally associated with cold fronts.
– Average speed ≈ 30 mph
– Temperatures drop rapidly
Cold Front
Cold Front
•Precipitation: Located on either side of the front.
•Convective, showery in nature
Warm Front
• Warm Front
– Colder (more dense) air retreats and is
replaced by the warmer (less dense) air.
– Warm fronts tend to have weaker
temperature gradients.
– Average speed ≈ 16 mph
– Temperatures slowly rise
Warm Front
Warm Front
• Lifted warm air produces widespread clouds
and precipitation well in advance of boundary
Occluded Front
• Cold fronts typically move faster than warm
fronts.
• Cold fronts can catch up and “overtake” a warm
front.
• Two types of occlusions:
– Cold type occlusion
– Warm type occlusion (very, very rare)
Occluded Front
Occluded Front
What kind of front is it?
• From the vantage point of the ground…
•If warm air replaces colder air, the front is
a warm front
• If cold air replaces warmer air, the front is
a cold front
• If the front does not move, it is a
stationary front
• Occluded fronts do not intersect the
ground; the interface between the air
masses is aloft
Norwegian Wave Cyclone Model
Wave Cyclone Formation
Typical Wave Cyclone Paths
Wave Cyclone Development
Convergence and Divergence
What initiates
“cyclogenesis?”
Low
High
500 mb height
When upper-level
divergence is stronger
than lower-level
convergence, more air is
taken out at the top than
is brought in at the
bottom. Surface pressure
drops, and the low
intensifies, or “deepens.”
Generation of Divergence Aloft
UPPER LEVEL
DIVERGENCE
INITIATES AND
MAINTAINS A
SURFACE LOW.
Formation of Cyclones
• Cyclogenesis – Development of a region of low
pressure -- a cyclone.
• Conditions:
– Cyclonic flow must be established at the surface.
– Cyclonic flow is CCW in the Northern Hemisphere.
– Convergence at the surface must be supported by
divergence aloft.
Shortwave Propagation
Cyclone Stages
Wave Cyclone Development
The cyclone matures
“Comma” shape is
characteristic of a well
developed wave cyclone.
cP
Cloud
“Shield”
L
mT
Wave Cyclone Development
The cyclone occludes
Cold front overtakes
warm front.
The cold air surrounds
the cyclone. Gradients
weaken and the low
slowly dies.
L
cP
mT
Mid-Latitude Cyclone
El Niño, La Niña
and Other Climate
Variables
Classwork: El Niño Pre-Test (HW#7)
Divide into 6 groups. Discuss and choose a spokesperson to
present a few comments from then group. THIS IS A
CLOSED BOOK/COMPUTER EXERCISE. Turn in a sheet for
each group with last names.
1. What is El Niño?
2. Where does El Nino occur?
3. What impact does El Niño have on California?
4. Does it impact other parts of the world?
5. What is La Niña?
6. Is there currently an El Niño, La Niña or neither?
Ripped from the Headlines…
El Niño Myths
• El Niño will be coming to California again
• All El Niños are the same
• El Niño spawns storms
• El Niño means lots of rain for California
• El Niño means flooding and big waves for
California
Ripped from the Headlines…
Is there currently an El Niño, La Niña or
neither?
Normal
Pacific Sea Surface Temperatures (SST)
El Niño
Pacific Sea Surface Temperatures (SST)
El Niño
Storm Track Pattern
Worldwide El Niño Impacts
La Niña
Pacific Sea Surface Temperatures (SST)
La Niña
Storm Track Pattern
Worldwide La Niña Impacts
Southern Oscillation
• Pressure Difference between Darwin and Tahiti
• Discovered by Gilbert Walker in 1924
•
“Tropical See-Saw”
• Negative SOI closely related to El Niño
• ENSO = El Niño Southern Oscillation
Oceanic Niño Index (ONI)
• SST departures from average in the Niño 3.4 region
• Three month running mean values of SST departures
El Niño: ONI ≥ +0.5°C
La Niña: ONI ≤ - 0.5°C
List of ENSO Events
Warm Episodes
max
Cold Episodes
min
JAS 1951 - NDJ 1951/52
MAM 1957 – MJJ 1958
JJA 1963 – DJF 1963/64
MJJ 1965 – MAM 1966
OND 1968 – AMJ 1969
ASO 1969 – DJF 1969/70
AMJ 1972 – FMA 1973
ASO 1976 – JFM 1977
ASO 1977 - DJF 1977/78
AMJ 1982 – MJJ 1983
JAS 1986 – JFM 1988
AMJ 1991 – MJJ 1992
FMA 1993 – JJA 1993
MAM 1994 – FMA 1995
AMJ 1997 – MAM 1998
AMJ 2002 – FMA 2003
JJA 2004 – JFM 2005
0.7
1.6
1.0
1.6
1.0
0.7
2.1
0.8
0.8
2.3
1.6
1.8
0.8
1.3
2.5
1.5
0.9
ASO 1949 – FMA 1951
MAM 1954 – DJF 1956/57
ASO 1961 – MAM 1962
MAM 1964 – JFM 1965
SON 1967 – MAM 1968
JJA 1970 – DJF 1971/72
AMJ 1973 – JJA 1974
ASO 1974 – AMJ 1976
ASO 1983 – DJF 1983/84
SON 1984 – MJJ 1985
AMJ 1988 – AMJ 1989
ASO 1995 – FMA 1996
JJA 1998 – MJJ 2000
SON 2000 – JFM 2001
JAS 2007 - AMJ 2008
-1.8
-2.1
-0.6
-1.1
-0.9
-1.4
-2.0
-1.8
-0.9
-1.1
-1.9
-.08
-1.6
-0.7
-1.5
5 Consecutive months of criteria
All El Niños
Weak El Niño
Moderate El Niño
Strong El Niño
ENSO vs. California Flooding
“Pineapple Connection”
New Years 1997 Storm
Other Atmospheric Indices
• PDO - Pacific Decadal Oscillation
• PNA – Pacific North American
• NAO – North Atlantic Oscillation
• AO – Arctic Oscillation
• MJO – Madden-Julian Oscillation
PDO
• Timescale (events ~ 20-30 yrs)
• Decadal variability in the Indo-Pacific sector
PDO
• Negative Phase: 1950’s mid 1970’s (La Niña like)
• Positive Phase: Mid
1970’s - 1990s (El Niño like)
MJO – Madden-Julian Oscillation
• 30-60 day cycles
that modulate
tropical rainfall/
atmospheric
circulation patterns
• ENSO-like
impacts on shorttime scale
• Modulates the
occurrence of
extreme weather
events
MJO – Madden-Julian Oscillation
Other Atmospheric Indices
NAO / AO Influence on Winter Extremes
+ Positive
Phase
- Negative
Phase