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

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

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  1. 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

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. Modes of Variability

  9. 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)

  10. 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

  11. 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)

  12. 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

  13. 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

  14. 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

  15. 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

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