Exploring the Ripples of Earth s Upper Atmosphere: Waves & Tides

Transcription

1 Exploring the Ripples of Earth s Upper Atmosphere: Waves & Tides Dr. Katelynn R. Greer, University of Colorado Boulder Ask questions! *Special Thanks to Dr. Federico Gasperini

2 Exploring the Ripples of Earth s Upper Atmosphere: Waves & Tides Dr. Katelynn R. Greer, University of Colorado Boulder Variability in the Thermosphere Atmospheric Waves Observa7on of Wave Field

3 Variability in the Thermosphere SOURCES Above Absorption of Solar EUV Radiation Solar EUV absorption GOLD Below Courtesy of the NCAR HAO and COMET 2 Courtesy of Dr. L. Frank, the University of Iowa

4 Variability in the Thermosphere SOURCES Above Absorption of Solar EUV Radiation Particle Precipitation Joule Heating Solar EUV absorption Particle Precipitation Joule Heating Magnetosphere- Ionosphere Current System Below Courtesy of the NCAR HAO and COMET 2 Courtesy of Dr. L. Frank, the University of Iowa

5 Variability in the Thermosphere SOURCES Above Absorption of Solar EUV Radiation Particle Precipitation Joule Heating GOLD In the last decade evidence has shown that terrestrial weather significantly influences the ionosphere- thermosphere system Below Dissipation of Upward Propagating Waves Courtesy of the NCAR HAO and COMET Courtesy of Dr. L. Frank, the University of Iowa

6 Variability in the Thermosphere SOURCES Courtesy of the NCAR HAO and COMET IllustraGon from the Solar and Space Physics Decadal Survey v The primary mechanism through which energy and momentum are transferred from the lower atmosphere to the upper atmosphere and ionosphere is through the propagamon of waves Courtesy of Dr. L. Frank, the University of Iowa

7 Atmospheric Waves Thermal Tides Kelvin Waves Propagate to thermosphere Propagate to thermosphere Mme scale: 2-20 days λx Earth s circumference Mme scale: 1/3 to 1 solar day λx Earth s circumference Gravity Waves Rossby (Planetary) Waves Do not easily propagate to thermosphere Mme scale: 2 to >30 days λx km Propagate to thermosphere Mme scale: min- hrs λx 1 to >100 km 7

8 Atmospheric Waves Thermal Tides Kelvin Waves The focus is on Thermal Tides and Gravity Waves, waves responsible for coupling the lower atmosphere to the upper atmosphere and Propagate to thermosphere ionosphere Mme scale: 2-20 days Propagate to thermosphere Mme scale: 1/3 to 1 solar day λx Earth s circumference Gravity Waves λx Earth s circumference Rossby (Planetary) Waves Do not easily propagate to thermosphere Mme scale: 2 to >30 days λx km Propagate to thermosphere Mme scale: min- hrs λx 1 to >100 km 8

9 thermosphere Atmospheric Waves Thermal Tides Ø The primary mechanism of excitamon: periodic heamng of the atmosphere by the Sun Solar&Radia*ve&Tidal&S O s=+k s= k N n=1 A n,s z = height ϑ = lagtude Ωn = frequency Ω = 2π/24 ( ( )) ( z,θ)cos nωt + sλ φ n,s z,θ t = UT Mme s = zonal wavenumber (s>0 to west) λ = longitude Φ = phase mesosphere O 2 ~90km UltraViolet O 3 ~30km heating rate mean diurnal semidiurnal stratosphere troposphere H 2 O ~15km local time 9

10 thermosphere Atmospheric Waves Thermal Tides Ø The primary mechanism of excitamon: periodic heamng of the atmosphere by the Sun Solar&Radia*ve&Tidal&S O s=+k s= k N n=1 A n,s z = height ϑ = lagtude Ωn = frequency Ω = 2π/24 ( ( )) ( z,θ)cos nωt + sλ φ n,s z,θ t = UT Mme s = zonal wavenumber (s>0 to west) λ = longitude Φ = phase O 2 Global waves observed in measurements like Temperature and Wind mesosphere ~90km UltraViolet Waves with s = n are referred to as migramng Mdes, follow the apparent momon of the Sun stratosphere troposphere H 2 O ~15km O 3 ~30km Waves with s n are referred to as non- migramng Mdes 10

11 Ø The primary mechanism of excitamon: periodic heamng of the atmosphere by the Sun Solar&Radia*ve&Tidal&S Major driver of the wave- 4 structure in the ionosphere/thermosphere C ph = O diurnal 2 Excited in the tropical troposphere by latent heat nω/s release in deep convecmve clouds mean Large source of variability ~90km in the MLT (up to 30 Waves K, or 20 with m/s) s n (s = n) are referred to as non- migramng Mdes (migramng). mesosphere stratosphere troposphere Atmospheric Waves Thermal Tides H 2 O ~15km UltraViolet O 3 A n,s Standard Nomenclature s= k n=1 O ~30km s= k n=1 s=+k heating rate N z = height ϑ = lagtude Ωn = frequency Ω = 2π/24 The zonal phase speed is: ( ( )) ( z,θ)cos nωt + sλ φ n,s z,θ DWx (DEx) to denote a westward- (eastward- ) propagamng diurnal Mde with zonal wavenumber x = s thermosphere For semidiurnal and terdiurnal Mdes S and T replaces D s=+k Diurnal Eastward- propagamng Tide with s=3, or DE3 t = UT Mme s = zonal wavenumber (s>0 to west) λ = longitude Φ = phase semidiurnal With fixed local Mme (e.g. sun- synch orbit): s=+k s= k N N A 0 n,s ( z,θ)cos nωt LT + ( s n)λ φ 12 n,s ( z,θ) 24 local time n=1 A n,s ( ( )) ( z,θ)cos nωt + sλ φ n,s z,θ ( ) 11

12 Atmospheric Waves Thermal Tides Ø The primary mechanism of excitamon: periodic heamng of the atmosphere by the Sun Curtesy of J. Oberheide 12

13 Atmospheric Waves Gravity Waves (GWs) ² Not to be confused with GravitaMonal Waves Gravity and Buoyancy are the restoring force for air parcels Local Waves Play an important role in coupling the lower atmosphere with the middle and upper atmosphere Orography Deep Convec7on 13

14 Atmospheric Waves Gravity Waves (GWs) Liu, H.- L., J. M. McInerney, S. Santos, P. H. Lauritzen, M. A. Taylor, and N. M. Pedatella(2014), Gravity waves simulated by high- resolumon Whole Atmosphere Community Climate Model, Geophys. Res. Lej., 41, , doi: /2014gl

15 Atmospheric Waves Nonlinear Wave Interactions cos( σ 1 t + s 1 λ) cos( σ 2 t + s 2 λ) ì î cos ((σ 1 +σ 2 )t +(s 1 + s 2 )λ) cos ((σ 1 σ 2 )t +(s 1 s 2 )λ) Al7tude Secondary Wave 1 Secondary Wave 2 cos[(σ 1 + σ 2 )t +(s 1 + s 2 )λ] cos[(σ 1 - σ 2 )t + (s 1 - s 2 )λ] Nonlinear Forcing Region Primary Wave 1 cos(σ 1 t + s 1 λ) Primary Wave 2 cos(σ 2 t + s 2 λ) 15

16 Observation of Wave Field Ground-based methods Advantages Incoherent scarer radars Resonance lidars MLT temperatures and winds at km, but only in intervals of 2 to 10 days Temperatures and winds both day and night, but not conmnuously MF and meteor radars Passive op7cal methods Winds between 80 and 100 km MLT temperatures and winds, but are restricted to nighrme 1. Ability to dismnguish waves over short Mme periods 2. InformaMon on vermcal structure Disadvantages 1. Lack of informamon on the lamtude- longitude structure 2. Inability to dismnguish between global- and local- scale waves

17 Observation of Wave Field Historical Side Note Studying Thermal Tides with Grenades Review lecture - Rocket studies of atmospheric 7des G. V. Groves Proc. R. Soc. Lond. A ; DOI: /rspa Published 8 December

18 Observation of Wave Field Space-based methods Advantage La7tude- longitude coverage The lower the inclinamon, the more rapid the orbit precesses with respect to the Sun (e.g., 120 days for i = 70 o ) Disadvantages Sampling Due to inherent variability of atmospheric system within the 24- hour local Mme coverage Low Earth OrbiMng Satellites Changing Longitude & LaGtude Aliasing Zonal mean and other longer- period waves can alias into the derived Mdal field and be perceived as local Mme changes 18

19 Observation of Wave Field Space-based methods Advantage Local Time coverage Observes waves as they develop and change in place, separamng Mme and spamal variability Disadvantages Longitude Coverage Cannot observe far side of the Earth and complicates derivamon of Mdes GeostaMonary Satellites Constant Longitude 19

20 Observation of Wave Field Initial GOLD Observations

21 Exploring the Ripples of Earth s Upper Atmosphere: Waves & Tides Dr. Katelynn R. Greer, University of Colorado Boulder Variability in the Thermosphere is due to both incoming energy from above (the Sun) and from below (atmospheric weather) Thermal Tides and Gravity Waves help connect the lower and upper atmosphere We use different observa7onal techniques to sense waves and 7des from the ground and space

22 Exploring the Ripples of Earth s Upper Atmosphere: Waves & Tides Dr. Katelynn R. Greer, University of Colorado Boulder Ques7ons?