GLOBAL CHANGES IN OUR ATMOSPHERE: a top-down point of view  Atmospheric Science 101  Structure of atmosphere  Important relationships  The Northern Hemisphere Annular Mode (NAM)  NAM patterns  Significance  Vortex variation  Amplifier mechanism  Implications and trends Var Limpasuvan 1 and Kumar Jeev 2 1 Department of Chemistry and Physics and 2 Department of Computer Science Coastal Carolina University, Conway, South Carolina 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”)

2 Orientation: Atmospheric Science o N equator 60 o N altitude 30 o N equator 60 o N NP 60 o N 30 o N equator altitude 30 o N equator 60 o N NP60 o N 30 o N equator altitude latitude 30 o N equator 60 o N NP60 o N 30 o N equator altitude latitude 12 km (~39,300 ft ) troposphere 50 km (~164,000 ft ) stratosphere mesosphere tropopause stratopause

3 Basic Atmospheric Structure 30 o N equator 60 o N sun west-east wind (“zonal wind”) sun West-east (zonal) wind (m/s)Temperature (deg K) Longitudinally Average winter summer VORTEX  Pressure (density) decreases rapidly with altitude  Where is the coldest region in atmosphere?  Note the jet reversal near 90 km

4 Simple Atmosphere sun West-east (zonal) wind (m/s)Temperature (deg K) Longitudinally Average winter summer  Radiatively determined state  Look markedly different than observations  Wind & temperature are governed by physics  Near geostrophic and hydrostatic balance  Latitudinal temp gradient ~ vertical wind shear

5 Atmospheric Waves and Circulation  Planetary waves (~ mountain; land-sea contrast; > 5000 km)  Gravity Waves (~ convection; adjustment; < 1000 km) Close-off jets cooling warming  Synoptic Waves (~weather storm; instability; between km)

6 Basic Atmospheric Structure Revisited West-east (zonal) wind (m/s)Temperature (deg K) Longitudinally Average winter summer  Atmospheric waves are important to maintain structure.  Circulating gyres due to waves spread response.  Balance between dynamics and radiative effects  Latitudinal temp gradient ~ vertical wind shear VORTEX Thermal Wind Relationship

7 Wintertime Climatology (DJF) Sea Level Pressure & Surface WindsZonal Wind 10 km & Storm Tracks  40-year average using NCEP/NCAR Reanalyses every 5 hPa 12 m/s H L H L H every 5 m/s track Jetstream Weather systems Aleutian Icelandic

8 Modes of Variability

9 The Northern Hemisphere Annular Mode (NAM) NAM PatternNAM Index HIGH LOW HIGH  “See-Saw” across Arctic Circle  30% of winter variance  North Atlantic Oscillation (NAO)  Jet Stream Shift (storm activity) Storm activity

10 The NAM Summary HIGH PhaseLOW Phase  Natural Mode of variability  Strong troposphere and stratosphere coupling  Characteristic of rotating fluids (i.e. other planets)  Changes that project on NAM will be amplified  Connects polar vortex with surface conditions  Rethinking of surface climate and weather

11 Stratospheric Influence of Surface Climate?  Impossible !!!  Growing evidence for “downward” influence  75 % of the atmospheric mass in troposphere.  Atmospheric waves mostly originate from near-surface.  Strong variation in polar vortex strength appears to reach surface  This variation occurs naturally within the system during winter  Surely, troposphere affects stratosphere. One way interaction!  D ynamics of this natural downward influence? How? (Mr. Jeev) Altitude (km)

12 Atmospheric Wave Amplifier VORTEX warm cold JET NORTH POLEEQUATOR TROPOSPHERE STRATOSPHERE TROPOPAUSE ALTITUDE (km) WINTERTIME heat flux colder JET VORTEX heat flux colder JET HIGH NAM  Positive feedback by waves  Turning the troposphere on itself

13 How Can the Polar Vortex Change?  Naturally with the atmospheric system  Solar Variability: 11-year solar cycle (Sunspots)  Stratospheric ozone and UV changes (10-20% of solar irradiance  )  Polar vortex becomes stronger and colder during UV increase El Chicon (1982, 17 o N)  Volcanic eruptions: stronger, colder vortex after eruption Pinatubo (1991, 15 o N) North pole Equator Aerosols (sulfuric acid + water) dark warm cold JET Wave amplification HIGH NAM  Similar mechanism to above ozone

14 Observed Trends in Northern Hemisphere  Polar stratospheric cooling  ~3-5 degrees since 1979 NAM Index Polar Stratospheric Clouds (PSC) Kiruna, Sweden Polar Mesospheric Clouds Edmonton, Alberta Canada  Trend toward positive NAM index  Stronger polar vortex (PSCs)  Change in wave propagation  Change in overturning gyres Surface Air Temperature  Incipient ozone loss (~SH)

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