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Radiative-Convective Modelling of the Earth’s Climate:The     Effect of Observed Changes in Cloud Amounts    Roger Davies,...
climate physics at Auckland•   observations                            •    theory    – MISR on Terra (global)            ...
MISR: Multiangle Imaging SpectroRadiometer                                   •   9 fixed view angles                      ...
NZIP_11   4
300 km         NZIP_11   5
NZIP_11   6
NZIP_11   7
Cloud-Top Heights measured by MISR• stereo pattern-matching from the A-cameras (±26°)   –   measurements with horizontal r...
Why bother with global cloud heights?• Cloud-Climate feedback• Changes in effective height, H   – emitted longwave radiati...
the simplest of equilibrium climate models                                    the simplest of equilibrium climate models  ...
the simplest of equilibrium climate models                20                15               raising tropopause height by ...
The Effect of Carbon Dioxide on Equilibrium Surface Temperature                                               3Change of E...
The Effect of Carbon Dioxide on Equilibrium Surface Temperature                                               3Change of E...
Annual Mean Effective Height                               meters             NZIP_11                    14
Interannual rms Fluctuation of Cloud-top                Heights                                           meters          ...
Correlation of anomalies in cloud-top height with            anomalies in sea level pressure                              ...
Correlation of anomalies in cloud-top height with          anomalies in surface temperature                               ...
Correlation of anomalies in cloud-top height with       anomalies in Southern Oscillation Index                           ...
Central Pacific, –Indonesia, –SOI                       1500                                                              ...
global cloud height anomalies                      60                      40                      20height anomaly (m)   ...
mean annual global stereo height distribution                                          clouds+surface (12/05-6/08)        ...
Standard Atmosphere with Clouds                    1pressure (hPa)                   10                                   ...
Standard Atmosphere with Clouds                    1pressure (hPa)                   10                                   ...
relative trapping of longwave emission from                 the surface       (adapted from Kiehl and Trenberth)          ...
Equilibrium Surface Temperatures: with constant albedo      Observed                                    288 K      No Atmo...
The Effect of Carbon Dioxide on Equilibrium Surface Temperature                                               3           ...
The Effect of Carbon Dioxide on Equilibrium Surface Temperature                                               3Change of E...
The Effect of Carbon Dioxide on Equilibrium Surface Temperature                                               5           ...
Standard Deviation of Annual Average of             Cloud-top Heights                                                     ...
Local Height Anomalies: Pacific Box (30°N–30°S, 100°E–130°W)                                                       rest of...
Normalized Height anomalies: Pacific Box/6, Remainder*5/6, Total                      80                      60          ...
Zonal annual mean fraction by height              20              18              16              14              12height...
In Summary• MISR cloud heights provide a useful climate data record• additional CO2 forcing over the last decade ≈ +0.28 W...
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14.20 o7 r davies

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Research 5: Roger Davies

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  • 12-month running mean of anomalies (h-hbar(time,space))overall decrease 45 m/decade. Sampling uncertainty 8 m,
  • Transcript of "14.20 o7 r davies"

    1. 1. Radiative-Convective Modelling of the Earth’s Climate:The Effect of Observed Changes in Cloud Amounts Roger Davies, Physics Department, The University of Auckland http://www.physics.auckland.ac.nz/uoa/professor-roger-davies
    2. 2. climate physics at Auckland• observations • theory – MISR on Terra (global) – equilibrium climate sensitivity • albedos, heights, winds – global balance of energy – cloud heights – radiative transfer – ‘effective’ height, H = ò f (h)h dh • shortwave (albedo) • H´ = H – <H> • longwave (greenhouse effect) – decadal time series of H´ • gases • clouds – correlations of H´ with SOI (El Niño/La Niña) – cloud physics – hints of decreasing H – convection – radiative-convective equilibrium (RCE) • with detailed clouds NZIP_11 2
    3. 3. MISR: Multiangle Imaging SpectroRadiometer • 9 fixed view angles – +70.5° to –70.5° – reflected solar radiances (4 bands) • climate data records – self-consistent: 5/2000 – present • deseasonalized interannual variations – albedo anomalies • onboard calibration ≈1% relative radiometric accuracy – height anomalies • geometrically (stereo) derived: no calibration driftTerra: 10:30 am sun-synchronous,pole-pole, 14.6 orbits per day 3
    4. 4. NZIP_11 4
    5. 5. 300 km NZIP_11 5
    6. 6. NZIP_11 6
    7. 7. NZIP_11 7
    8. 8. Cloud-Top Heights measured by MISR• stereo pattern-matching from the A-cameras (±26°) – measurements with horizontal resolution 275 m: heights every 2.2 km – effective height: max contrast in SW reflectivity, may include surface – rms instantaneous height uncertainty: ≈500 m (validated) – O(108) measurements per month, globally at 10:30 am local time – global sampling error: ≈30 m/month; ≈8 m/year• March 2000 — February 2010: the first 10 years• consistent climate data record of cloud heights – insensitive to radiometric calibration – high resolution measurements – uniform technique from pole-pole (no view angle effects)• deseasonalized anomalies, globally and regionally NZIP_11 8
    9. 9. Why bother with global cloud heights?• Cloud-Climate feedback• Changes in effective height, H – emitted longwave radiation to space controls temperatures at z > H • this temperature is fixed for a given albedo, in equilibrium – if H decreases, the convective layer is reduced • results in lower equilibrium surface temperature• In radiative-convective equilibrium (RCE) – height increase implies warming, decrease implies cooling• Over 1 decade, CO2 forcing ≈0.28 W m-2 (IPCC) – In RCE this is equivalent to an increase of ≈28 m in global average effective height NZIP_11 9
    10. 10. the simplest of equilibrium climate models the simplest of equilibrium climate models 20 20 temperature controlled by albedo Tmin temperature controlled by albedo, a 15 15 altitude controlled by thethe greenhouse effect he altitude controlled by greenhouse effectaltitude (km)altitude (km) 10 10 convection, with lapse rate G convection 5 5 0 0 -70 -70 -60 -60 -50 -50 -40 -40 -30 -30 -20 -20 -10 -10 0 0 10 10 20 20 temperature (°C) temperature (°C) NZIP_11 10
    11. 11. the simplest of equilibrium climate models 20 15 raising tropopause height by 154m (≈2xCO2) increases surface temperature by ≈1°Caltitude (km) 10 5 0 -70 -60 -50 -40 -30 -20 -10 0 10 20 temperature (°C) NZIP_11 11
    12. 12. The Effect of Carbon Dioxide on Equilibrium Surface Temperature 3Change of Equilibrium Surface Temperature °C 2 784 1 change CO2 only 554 keep clouds constant 0 keep albedo constant 392 keep water vapour constant 277 -1 190 -2 -3 100 1000 CO2 concentration (parts per million) NZIP_11 12
    13. 13. The Effect of Carbon Dioxide on Equilibrium Surface Temperature 3Change of Equilibrium Surface Temperature °C with water vapour feedback at 8%/K 2 and cloud fraction at 5%/K change CO2, water vapour and low cloud fraction 784 1 and cloud height by ±300 m/K 554 0 392 277 -1 190 -2 -3 100 1000 CO2 concentration (parts per million) NZIP_11 13
    14. 14. Annual Mean Effective Height meters NZIP_11 14
    15. 15. Interannual rms Fluctuation of Cloud-top Heights meters NZIP_11 15
    16. 16. Correlation of anomalies in cloud-top height with anomalies in sea level pressure rsea level pressure from NCEP reanalysis Mar 2000–Feb 2010 cloud-top heights from MISR NZIP_11 16
    17. 17. Correlation of anomalies in cloud-top height with anomalies in surface temperature rsurface temperature from NCEP reanalysis Mar 2000–Feb 2010 cloud-top heights from MISR NZIP_11 17
    18. 18. Correlation of anomalies in cloud-top height with anomalies in Southern Oscillation Index rSOI from Australian Bureau of Meteorology Mar 2000–Feb 2010 cloud-top heights from MISR NZIP_11 18
    19. 19. Central Pacific, –Indonesia, –SOI 1500 15 1000 10 500 5Height anomalies (m) 0 0 2000 2002 2004 2006 2008 2010 -500 -5 -1000 -10 -1500 -15 Year Indonesian heights inverted SOI inverted NZIP_11 19
    20. 20. global cloud height anomalies 60 40 20height anomaly (m) 0 -20 -40 -60 -80 -100 2000 2002 2004 2006 2008 2010 year 12-month running mean overall decrease: 45 ±5 m max departure: –80 m sampling error ±8 m interannual rms: 26 m NZIP_11 20
    21. 21. mean annual global stereo height distribution clouds+surface (12/05-6/08) WITHOUT THIN CIRRUS 20 18 16 Total fractions 14 surface: 0.366 non-surface: 0.634 12height (km) low (0-3 km): 0.363 mid (3-7 km): 0.144 high (>7 km): 0.128 all 10 cloud only 8 6 4 2 0 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 fraction/km NZIP_11 21
    22. 22. Standard Atmosphere with Clouds 1pressure (hPa) 10 RCE RE 100 1000 190 210 230 250 270 290 310 330 350 370 390 temperature (K) NZIP_11 22
    23. 23. Standard Atmosphere with Clouds 1pressure (hPa) 10 RCE RE 100 1000 190 210 230 250 270 290 310 330 350 370 390 temperature (K) NZIP_11 23
    24. 24. relative trapping of longwave emission from the surface (adapted from Kiehl and Trenberth) clouds 45% water vapour 33% carbon dioxide 15% others 7% NZIP_11 24
    25. 25. Equilibrium Surface Temperatures: with constant albedo Observed 288 K No Atmosphere 255 K Model, no clouds 278 K Model, observed clouds 291 K Model, no high clouds 286 K Model, observed clouds, 50% CO2 290 K NZIP_11 25
    26. 26. The Effect of Carbon Dioxide on Equilibrium Surface Temperature 3 with water vapour feedback @8%/1°CChange of Equilibrium Surface Temperature °C 2 change CO2 and water vapour keep relative humidity constant keep clouds constant 784 1 keep albedo constant 554 0 392 277 -1 190 -2 -3 100 1000 CO2 concentration (parts per million) NZIP_11 26
    27. 27. The Effect of Carbon Dioxide on Equilibrium Surface Temperature 3Change of Equilibrium Surface Temperature °C with water vapour feedback at 8% 2 and cloud fraction at 5%/degree change CO2, water vapour and low cloud fraction 784 1 554 0 392 277 -1 190 -2 -3 100 1000 CO2 concentration (parts per million) NZIP_11 27
    28. 28. The Effect of Carbon Dioxide on Equilibrium Surface Temperature 5 4Change of Equilibrium Surface Temperature °C Maximum Arctic ice-albedo feedback 3 2 784 1 change CO2 only keep clouds constant 554 0 keep albedo constant 392 keep water vapour constant 277 -1 190 -2 -3 Last Glacial Maximum -4 -5 100 1000 CO2 concentration (parts per million) NZIP_11 28
    29. 29. Standard Deviation of Annual Average of Cloud-top Heights metersPacific box: 30°S–30°N, 100°E–230°E (130°W)Area: 1/6 of globe NZIP_11 29
    30. 30. Local Height Anomalies: Pacific Box (30°N–30°S, 100°E–130°W) rest of world 250 200 150Height anomaly (m) 100 50 0 2000 2002 2004 2006 2008 2010 -50 -100 -150 Year NZIP_11 30
    31. 31. Normalized Height anomalies: Pacific Box/6, Remainder*5/6, Total 80 60 40 20Height anomaly (m) 0 2000 2002 2004 2006 2008 2010 -20 -40 -60 -80 -100 Year NZIP_11 31
    32. 32. Zonal annual mean fraction by height 20 18 16 14 12height (km) 58°S 10 9°N 21°N 8 6 4 2 0 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 fraction/km NZIP_11 32
    33. 33. In Summary• MISR cloud heights provide a useful climate data record• additional CO2 forcing over the last decade ≈ +0.28 W m-2 – equivalent to an increase in effective emission altitude of ≈28 m in RCE• globally averaged effective height shows this level of fluctuation at the annual level (26 m rms) – heights have decreased by ≈45 m over the last decade• the major event of the decade is coincident with the 2007-8 La Niña – offsetting height changes between Indonesia and Central Pacific – teleconnections elsewhere appear to dominate the global result NZIP_11 33
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