Development of Data Assimilation Systems for

Short-Term Numerical Weather Prediction at JMA

Tadashi Fujita (NPD JMA)Y. Honda, Y. Ikuta, J. Fukuda, Y. Ishikawa, K. Yoshimoto

Contents

1. Meso-scale NWP system (MA: Meso-scale Analysis) 1-1. MA operational system 1-2. recent update

2. Local NWP system (LA: Local Analysis) 2-1. LA trial operation system 2-2. recent developments

3. Summary

Contents

1. Meso-scale NWP system (MA: Meso-scale Analysis) 1-1. MA operational system 1-2. recent update

2. Local NWP system (LA: Local Analysis) 2-1. LA trial operation system 2-2. recent developments

3. Summary

Meso-scale NWP System• Forecast Model : Meso-Scale Model (MSM) based on JMA Nonhydrostatic

Model (JMA-NHM)• Data Assimilation System : Meso-scale Analysis (MA) based on Nonhydrostatic

meso 4DVar-system (JNoVA)

•Horizontal resolution ： 5km•Domain: 3600*2880km

(721*577 grid points)•Forecast term + 00,06,12,18Z => 15hours + 03,09,15,21Z => 33hours•Forecast model Meso-Scale Model (MSM)•Initial condition (atmosphere) 　 Meso-scale Analysis (MA)•Boundary condition 20km-GSM (Global Spectral Model)

Domain Specifications

Objectives of Meso-scale NWP System

• Disaster Prevention– Prediction of severe weather such as heavy rainfall is one of

the main targets for mitigation and reduction of damage to property and loss of life.

– Input to short-range precipitation forecast system– Input to storm surge model

• Aviation Weather Forecast– Enrichment of the weather information for aviation safety– Terminal Area Forecast (TAF) Guidance and so on.

MA operational system00UTC 03UTC

JNoVA 4DVar(inner model 15km JMA-NHM)

FG (5km JMA-NHM)

Outer model 5km JMA-NHM

33h forecast

Obs. - FG

Analysis increment

03UTC 06UTC

JNoVA 4DVar(inner model 15km JMA-NHM)

FG (5km JMA-NHM)

outer model 5km JMA-NHM

15h forecast

Obs. - FG

Analysis increment

MA

MSM

MSM (5km JMA-NHM)

MA Coverage Maps of Observation Data

Coverage Maps of Observation Data

Direct assimilation of satellite radiance data

9

9

Score of MSM Precipitation ForecastVerification Grid : 20km SquareVerified Element: 1mm/3hr Verification Period :From Mar. 2001 to Sep. 2011

Threat Score

4DVar

20km GSM GPS

Major revision of physical processes

dx=10km=>5km

Nonhydro 4DVar

Nonhydro model Improvement of

convective scheme

satellite radiance temperature

Radar reflectivity

Contents

1. Meso-scale NWP system (MA: Meso-scale Analysis) 1-1. MA operational system 1-2. recent update

2. Local NWP system (LA: Local Analysis) 2-1. LA trial operation system 2-2. recent developments

3. Summary

Assimilation of RH data retrieved from3D radar reflectivity

=> 　 Improvement of humidity and precipitation forecast of MSM

MSM 3h accumulated precipitation forecast26 Jul. 2009 03UTC

Use of 3D radar reflectivity data (started 9 Jun. 2011)

(a) (b) (c)

Control FT=12 Test FT=12 Obs 2009/07/26 03UTC

First Guess (MSM)

Ze from Radar simulator Ze obs.

RH retrieval algorithm

retrieved RH

retrieved RH

retrieved RH

MSM (5km)Outer model (5km)

inner model (15km)

MA

(cf. Meteo France method)

Contents

1. Meso-scale NWP system (MA: Meso-scale Analysis) 1-1. MA operational system 1-2. recent update

2. Local NWP system (LA: Local Analysis) 2-1. LA trial operation system 2-2. recent developments

3. Summary

Local NWP System• Forecast Model : Local Forecast Model (LFM) JMA Nonhydrostatic Model

(JMA-NHM)• Data Assimilation System : Local Analysis (LA) JNoVA 3DVar• Trial operation started in Nov. 2010• operation planned in 2012

•Horizontal resolution ： 2km•Forecast term + 9hours Forecast model Local Forecast Model (LFM)•Initial condition (atmosphere) 　 Local Analysis (LA)•Boundary condition 5km-MSM

SpecificationsObjectivesProducing sophisticated disaster prevention and aviation weather information with high resolution NWP

LA (5km 441x501)

LFM(2km 551x801)

domain used in trial operation

LA trial operation system

3DVAR(5km)

LF1(5km)

3DVAR

LF1 LF1

3DVAR

LFM (2km)

MSM (in operation)

3DVAR

JMA-NHM 1h forecast, dx=5kmBoundary ConditionFirst GuesshydrometeorsAnalysis

LF1

MSM (in operation)

LA

Rapid update cycle (RUC) 3DVAR

FT=0FT=-1FT=-2FT=-3

FT=3

FT=3

LA Coverage Maps of Observation DataSurface stations

(temperature and wind)Doppler radar

(radial velocity)

Aviation(temperatureand horizontal wind)

Ground-based GPS(total column water vapor)

Wind Profiler(horizontal wind)

LFM precipitation forecast• precipitation related to heated land in the afternoon

(16 Aug. 2010 09UTC 1h precipitation)Observation LFM (FT=3)

Contents

1. Meso-scale NWP system (MA: Meso-scale Analysis) 1-1. MA operational system 1-2. recent update

2. Local NWP system (LA: Local Analysis) 2-1. LA system in trial operation 2-2. recent development

3. Summary

(i) Use of radar reflectivity observation

Simulate radar reflectivity from LF1 (JMA-NHM forecast)=> estimate RH from reflectivity=> assimilate RH in 3DVAR

LF1 LF1

3DVAR

Radar simulator

retrieval

Radar obs.

ZeZe Rain, snow, graupel

RH

RH - reflectivity Database

3h accumulated precipitation （ FT=3 ）

Control Test Observation

FT=0 Total column water vapor (Test-Control)

(i) Use of radar reflectivity observation

(ii) Vertical Coordinate of Control Variable• Control(=Trial Operation) : z*-coordinateInfluence of topography remains strong up to high altitudes

ground

model top

Slowly shift toz-coordinate

Rapidly shift toz-coordinate

z-coordinatez-coordinate

z*-coordinate CV new coordinate

• Test : New coordinatefollow terrain near the surface => rapidly shift to z-coordinate aloft

Vertical Cross Section of T increment

Control Test

Reasonably limits the influence of topography within the lower troposphere.

(ii) Vertical Coordinate of Control Variable

• Control: ground potential temperature is fixed⇒excessive temperature increment in the lower troposphere

ground

1.5m

20m

0m

surface

the lowest model level

PT

Obs

excessive increment

• Test : extend the control variable to include ground potential temperature

1.5m

20m

0mAnalyze ground PTfixed

⇒ Analyze ground PT to mitigate excessive increment

(iii) Extension of Control Variables

Control Test

Vertical cross section of temperature analysis increment

Mitigate excessive temperature increment in the lower troposphere

(iii) Extension of Control Variables

(iv) Incremental Analysis Updates

Obs. Obs. Obs. Obs.

MSM

LFM

Gradually add increment

3DVar 3DVar 3DVar 3DVar

Gradually add 3DVar increment in the assimilation window => enhance balance of the analysis

30min.

(cf. Bloom et al. 1996, Clayton 2003, Lee et al. 2006, etc.)

(iv) Incremental Analysis Updates

Gradually add 3DVar increment in the assimilation window => enhance balance of the analysis

Obs. Obs. Obs. Obs.

MSM

5km JMA-NHM

Actual implementation in test experiment

3DVar 3DVar 3DVar 3DVar30min.

Domain averaged Ps tendency Qc summed over (limited) domain

ControlTest

(iv) Incremental Analysis Updates(Test with 5km forecast)

Control

Test

FT=0FT=-3h FT=6h

Rapid update cycle 5km forecast FT=0 FT=6h5km forecast

update of B.C.

Test by single surface T observation(T increment on the lowest model level)

Control Test

•Terrain between grid points is used to modify horizontal background error correlation (steep => damp fast)•Implemented using coordinate transformation + recursive filter

(v) Terrain-Adjusted Background Error Correlation

Summary•JMA operates Meso-scale NWP system aimed at disaster prevention and aviation weather information services.

•Steady improvement of MSM forecast has been attained from various improvements of the system, including recent introduction of radar reflectivity data (retrieved RH) in MA.

•Trial operation of Local NWP system is currently underway, toward the operational run scheduled in 2012.

•Various development of LA is underway to improve the system. introduction of new observation, including radar reflectivity data new CV vertical coordinate ground PT analysis IAU terrain-adjusted background error correlation