# Presentation: 164739

## Convectively ForcedGravity Wave DragGWDC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

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

**OUTLINE**

## Theory by Chun and Baik 1998

## Convective Forcing

- 2-Dimensional    x-z
- Steady-state
- Non-rotating
- Hydrostatic
- Inviscid
- Boussinesq
- Linearized – Small perturbations
- U, N     Constant with x and z

**0 ;**

- Orographic Forcing

## Slide 6

## w

**w**

**u**

- 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

## Slide 8

## Slide 9

## F  =  -U M

- Fz  =  -Uz M

## F

- M

- F  =  -U M

## F

- M

- H

- L

- F  =  -U M

## Parameterization proposed by Chun and Baik 1998

## STEP 1

## c1

- c1

- c2

- c1  =    1.41
- c2     =  - 0.38
- α   =    0.1

- a1  =    α Δx

## Vct

**V**ct

**V**

**Essentially     **
**1-dimensional**
**in the horizontal plane**

## STEP 2

## Wave breaking

**Reduction of**
**Momentum Flux**

- F

- M

## Lindzen’s Saturation Hypothesis

**          ****If**
**Reduce wave amplitude so that Ri = 1⁄4**
**Gives new reduced **

##                    Main Reasons for Wave braking

-                                               Stress Reduction
-                                               Momentum deposition

- Critical levels
- Low wind speeds
- Low density

## Climate runs

**with**
**CFS SET22 T126L64**

## 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

**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

- Encouraging
- Results

## 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

## Observational and Simulation Data Sets

| Experiment Acronym | Description | Time period | Number of years |
| --- | --- | --- | --- |
| ERA40 | Observations | JAN1971-DEC2000 | 30 |
| CNTR
(Saha) | SET22 | JAN1948-FEB1959 | 11 |
| GWDC1 | SET22 + GWDC Alt1 | JAN1948-FEB1959 | 11 |
| GWDC2 | SET22 + GWDC Alt2 | JAN1948-FEB1959 | 11 |

## Two GWDC Experiments

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

## CONTROL EXPERIMENT

## Slide 27

## Slide 28

## Slide 29

## Slide 30

## QBO

## Slide 32

## Slide 33

## Slide 34

## Slide 35

## Slide 36

## CFS have no QBO

## Slide 38

## Slide 39

## Extreme Negative and Positive Anomalies

- Stratospheric Polar Night Jet
- 1971-2000

## Slide 41

## Slide 42

## GWDC EXPERIMENT

## Slide 44

## Slide 45

## 1

**1**

**2**

**3**

## Slide 47

## Slide 48

## 1/10 Contour interval

**1/10 Contour interval**

**DJF               GWDC1**

## DJF               GWDC1

**DJF               GWDC1**

## DJF               GWDC2

**DJF               GWDC2**

## DJF               GWDC2

**DJF               GWDC2**

## JJA               GWDC1

**JJA               GWDC1**

## JJA               GWDC1

**JJA               GWDC1**

## JJA               GWDC2

**JJA               GWDC2**

## JJA               GWDC2

**JJA               GWDC2**

## Slide 57

## Slide 58

## SST and PRATE

- DJF 1950-1959

## Slide 60

## Slide 61

## SST and PRATE

- JJA 1950-1959

## Slide 63

## Slide 64

##  Data Assimilation and Week-1 Forecast Experiments

| Experiment Acronym | Description | Time period | Number of days |
| --- | --- | --- | --- |
| prs46h | CNTR | 24DEC2007  -  22JAN2008 | 30 |
| prs45hg | CNTR+GWDC2 | 12JUL2007  -  28JUL2007 | 30 |
| prs41h | CNTR | 24DEC2007  -  22JAN2008 | 30 |
| prs46hg | CNTR+GWDC2 | 12JUL2007  -  28JUL2007
 | 30 |

## Fit to Obs

**Boreal Summer**

- 150 – 50 hPa
- Vector Wind                       1-Day and 2-Day

## Slide 67

## Slide 68

## Slide 69

## Slide 70

## Fit to Obs

**Boreal Summer**

- Temperature                      1-Day and 2-Day

## Slide 72

## Slide 73

## Slide 74

## Slide 75

## Fit to Obs

**Boreal Winter**

- Vector Wind                       1-Day and 2-Day

## Slide 77

## Slide 78

## Slide 79

## Slide 80

## Fit to Obs

**Boreal Winter**

- Temperature                      1-Day and 2-Day

## Slide 82

## Slide 83

## Slide 84

## Slide 85

## 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

## Neutral Results

**Neutral Results**

## Neutral Results

**Neutral Results**

## Neutral Results

**Neutral Results**

## Neutral Results

**Neutral Results**

## 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

## Slightly worse

**Slightly worse**
**By 1 point**

## Neutral Results

**Neutral Results**

## Slightly worse

**Slightly worse**
**By 0.13**

## Neutral Results

**Slightly better**
**By 0.08**

## 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

## Suggestions

**Suggestions**

- 1. Gravity waves are ubiquitous in the atmosphere – Not only over land – GWD Magnitude
- 2. Spectrum of waves with different wave speeds