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Var Limpasuvan 1 and Kumar Jeev 2. Goals : To demonstrate that changes in our atmosphere above 30,000 feet can influence surface climate To see global changes in a new perspective (“top- down view”). GLOBAL CHANGES IN OUR ATMOSPHERE: a top-down point of view.

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var limpasuvan 1 and kumar jeev 2
Var Limpasuvan1 and Kumar Jeev2
  • Goals:
    • To demonstrate that changes in our atmosphere
    • above 30,000 feet can influence surface climate
    • To see global changes in a new perspective (“top-
    • down view”)

GLOBAL CHANGES IN OUR ATMOSPHERE: a top-down point of view

1Department of Chemistry and Physics and 2Department of Computer Science

Coastal Carolina University, Conway, South Carolina

  • Atmospheric Science 101
    • Structure of atmosphere
    • Important relationships
  • The Northern Hemisphere Annular Mode (NAM)
    • NAM patterns
    • Significance
  • Vortex variation
    • Amplifier mechanism
    • Implications and trends
orientation atmospheric science 101

60oN

60oN

60oN

30oN

30oN

30oN

altitude

altitude

equator

equator

equator

latitude

latitude

60oN

longitude

longitude

NP

30oN

60oN

latitude

latitude

50 km (~164,000 ft )

stratopause

equator

altitude

altitude

30oN

stratosphere

12 km (~39,300 ft )

tropopause

troposphere

equator

equator

equator

NP

60oN

60oN

NP

30oN

30oN

longitude

longitude

latitude

latitude

Orientation: Atmospheric Science 101

mesosphere

basic atmospheric structure

Longitudinally Average

sun

sun

west-east wind

(“zonal wind”)

West-east (zonal) wind (m/s)

Temperature (deg K)

60oN

30oN

VORTEX

VORTEX

equator

summer

winter

winter

summer

Basic Atmospheric Structure
  • Pressure (density) decreases rapidly with altitude
  • Where is the coldest region in atmosphere?
  • Note the jet reversal near 90 km
simple atmosphere

Latitudinal temp gradient ~ vertical wind shear

  • Near geostrophic and hydrostatic balance

Longitudinally Average

sun

West-east (zonal) wind (m/s)

Temperature (deg K)

summer

winter

winter

summer

130

270

250

290

230

190

210

150

100

50

-100

200

150

250

300

-50

170

Simple Atmosphere
  • Radiatively determined state
  • Wind & temperature are governed by physics
  • Look markedly different than observations
atmospheric waves and circulation

Close-off jets

Close-off jets

  • Planetary waves (~ mountain; land-sea contrast; > 5000 km)
  • Gravity Waves (~ convection; adjustment; < 1000 km)
  • Synoptic Waves (~weather storm; instability; between 1000-3000 km)

cooling

warming

Atmospheric Waves and Circulation
basic atmospheric structure revisited

Longitudinally Average

West-east (zonal) wind (m/s)

Temperature (deg K)

VORTEX

VORTEX

summer

winter

winter

summer

Thermal Wind Relationship

50

270

250

290

230

190

210

170

-100

150

100

200

150

250

300

-50

130

Basic Atmospheric Structure Revisited
  • Atmospheric waves are important to maintain structure.
  • Circulating gyres due to waves spread response.
  • Latitudinal temp gradient ~ vertical wind shear
  • Balance between dynamics and radiative effects
wintertime climatology djf

Aleutian

Jetstream

12 m/s

Weather systems

Icelandic

every 5 m/s

every 5 hPa

track

Wintertime Climatology (DJF)

Sea Level Pressure & Surface Winds

Zonal Wind (Jet) @ 10 km & Storm Tracks

H

L

H

H

L

  • 40-year average using NCEP/NCAR Reanalyses
the northern hemisphere annular mode nam

NAM Index

Storm activity

HIGH

LOW

HIGH

The Northern Hemisphere Annular Mode (NAM)
  • “See-Saw” across Arctic Circle

NAM Pattern

  • 30% of winter variance
  • North Atlantic Oscillation (NAO)
  • Jet Stream Shift (storm activity)
the nam summary

LOW Phase

HIGH Phase

The NAM Summary
  • Natural Mode of variability
  • Characteristic of rotating fluids (i.e. other planets)
  • Changes that project on NAM will be amplified
  • Strong troposphere and stratosphere coupling
  • Connects polar vortex with surface conditions
  • Rethinking of surface climate and weather
stratospheric influence of surface climate
Stratospheric Influence of Surface Climate?
  • Impossible !!!
  • 75 % of the atmospheric mass in troposphere.
  • Atmospheric waves mostly originate from near-surface.
  • Surely, troposphere affects stratosphere. One way interaction!

Altitude (km)

  • Growing evidence for “downward” influence
  • Strong variation in polar vortex strength appears to reach surface
  • This variation occurs naturally within the system during winter
  • Dynamics of this natural downward influence? How? (Mr. Jeev)
atmospheric wave amplifier

VORTEX

colder

JET

JET

JET

warm

cold

colder

STRATOSPHERE

heat flux

heat flux

ALTITUDE (km)

TROPOPAUSE

  • Positive feedback by waves

TROPOSPHERE

  • Turning the troposphere on itself

EQUATOR

NORTH POLE

WINTERTIME

Atmospheric Wave Amplifier

VORTEX

HIGH NAM

how can the polar vortex change

JET

  • Volcanic eruptions: stronger, colder vortex after eruption

Aerosols (sulfuric acid + water)

JET

cold

warm

North pole

Equator

dark

How Can the Polar Vortex Change?
  • Naturally with the atmospheric system

Pinatubo (1991, 15oN)

ozone

El Chicon (1982, 17oN)

Wave amplification

HIGH NAM

  • Solar Variability: 11-year solar cycle (Sunspots)
  • Polar vortex becomes stronger and colder during UV increase
  • Stratospheric ozone and UV changes (10-20% of solar irradiance D)
  • Similar mechanism to above
observed trends in northern hemisphere

NAM Index

Polar Stratospheric Clouds (PSC)

Kiruna, Sweden

Polar Mesospheric Clouds

Edmonton, Alberta Canada

Surface Air Temperature

Observed Trends in Northern Hemisphere
  • Polar stratospheric cooling
  • ~3-5 degrees since 1979
  • Stronger polar vortex (PSCs)
  • Incipient ozone loss (~SH)
  • Change in wave propagation
  • Change in overturning gyres
  • Trend toward positive NAM index
summary
Summary
  • Dramatic changes above 30,000 ft (tropopause) are present
    • sporadic: volcanic eruptions, sudden vortex changes
    • cyclical: solar cycle
    • trends: stratospheric/mesospheric cooling
    • future NASA missions (EOS-AURA, SABER, AIM)
  • Their influence can extend downward and affect surface
    • amplification process due to atmospheric waves
    • projection on to preferred mode of variability (NAM)
  • Strong stratospheric-tropospheric coupling
    • stratosphere ignored in the past; future models must extend up
    • improving mid-range forecasting
  • Support: National Science Foundation – RUI; CCU