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Convectively Forced Gravity Wave Drag GWD C in the CFS and GFS. Åke Johansson. ACKNOWLEDGEMENTS. Hye-Yeong Chun Jong-Jin Baik In-Sun Song Suranjana Saha Shrinivas Moorthi Hua-Lu Pan Jordan Alpert Huug van den Dool Mark Iredell. OUTLINE. Theory by Chun and Baik 1998

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slide2

ACKNOWLEDGEMENTS

Hye-Yeong Chun

Jong-Jin Baik

In-Sun Song

Suranjana Saha

Shrinivas Moorthi

Hua-Lu Pan

Jordan Alpert

Huug van den Dool

Mark Iredell

slide3

OUTLINE

  • Theory by Chun and Baik 1998
  • Parameterization proposed by Chun and Baik 1998
  • Climate runs with CFS
  • Data Assimilation and Week-1 runs with GFS
  • Conclusions
  • Suggestions
slide5

2-Dimensional x-z

Steady-state

Non-rotating

Hydrostatic

Inviscid

Boussinesq

Linearized – Small perturbations

U, N Constant with x and z

0 ;

Orographic Forcing

Convective Forcing

slide7

U = 15 m/s

N = 0.007 s-1

Zb = 1.5 km

Zt = 11 km

a1 = 10 km

a2 = 5 a1

To = 273 K

Qo = 1 J/kg/s

w

u

slide10

F = -U M

Fz = -Uz M

slide15

c1

c2

a1 = αΔx

c1 = 1.41

c2 = - 0.38

α = 0.1

slide16

V

Vct

Essentially

1-dimensional

in the horizontal plane

slide18

Wave breaking

Reduction of

Momentum Flux

M

F

slide19

Lindzen’s Saturation Hypothesis

If

Reduce wave amplitude so that Ri = ¼

Gives new reduced

slide20

Main Reasons for Wave braking

Stress Reduction

Momentum deposition

  • Critical levels
  • Low wind speeds
  • Low density
slide21

Climate runs

with

CFS SET22 T126L64

slide22

Yonsei Univ GCM 2001

4° x 5° ( lat x lon ) Δx ~ 445 Km

15 Layers Top a 1 hPa

Perpetual July AMIP integrations for 360 days

Last 90 day averages are considered

With vs Without GWDC

α = 0.4

Encouraging

Results

NCAR CCM3 2004

T42 Δx ~ 315 Km

18 Layers Top a 2.5 hPa

Perpetual January and July AMIP integrations for 3 yrs

Last 2 yrs averages are considered

With vs Without GWDC

α < 0.16

Encouraging

Results

slide23

CFS Experiments

T126L64 Δx ~ 106 Km Top at 0.2 hPa

SET22 = Operational CFS + Several updates

New Shortwave radiation: Hourly + RRTM1

Longwave Radiation: Hourly + RRTM

Realistic CO2

Maximum-random cloud overlap

ESMF 3.0.1

Enthalpy equation

slide25

Two GWDC Experiments

Two different ways in which the momentum compensation within the cloud is distributed

slide40

Extreme Negative and Positive Anomalies

Stratospheric Polar Night Jet

1971-2000

slide46

3

2

1

slide49

DJF GWDC1

1/10 Contour interval

slide59

SST and PRATE

DJF 1950-1959

slide62

SST and PRATE

JJA 1950-1959

slide66

Fit to Obs

Boreal Summer

150 – 50 hPa

Vector Wind 1-Day and 2-Day

slide71

Fit to Obs

Boreal Summer

Temperature 1-Day and 2-Day

slide76

Fit to Obs

Boreal Winter

Vector Wind 1-Day and 2-Day

slide81

Fit to Obs

Boreal Winter

Temperature 1-Day and 2-Day

slide86

Skill Scores

Boreal Winter

AC NH Z500 5-Day

AC SH Z500 5-Day

RMSE Tropical Vector Wind 200 hPa 3-Day

RMSE Tropical Vector Wind 850 hPa 3-Day

slide91

Skill Scores

Boreal Summer

AC NH Z500 5-Day

AC SH Z500 5-Day

RMSE Tropical Vector Wind 200 hPa 3-Day

RMSE Tropical Vector Wind 850 hPa 3-Day

slide92

Slightly worse

By 1 point

slide95

Slightly better

By 0.08

Neutral Results

slide96

CONCLUSIONS

  • Climate is improved in tropical upper troposphere and lower stratosphere for zonal wind
  • Climate in the extratropics is not statistically different from Control
  • Fits to Obs shows improvements in the tropical stratosphere for Wind and Temperature
  • NWP Skill scores are essentially neutral
slide97

Suggestions

1. Gravity waves are ubiquitous in the atmosphere – Not only over land – GWD Magnitude

2. Spectrum of waves with different wave speeds