Soil moisture generation at ECMWF

Gisela Seuffert and Pedro Viterbo

European Centre for Medium Range Weather Forecasts

ELDAS Interim Data Co-ordination Meeting17./18.09.2003

Plans ( ELDAS 1st progress meeting)

Assimilation aspects:• Minimize the combined errors in prediction of soil moisture, latent heat flux and

screen level observations

• Further mw-Tb assimilation experiments (viewing angle, times)

• Assimilation of heating rates

Technical aspects:• Paper(s) focusing on the

- new features of assimilation method - assimilation of mw-Tb

- (assimilation of heating rates)

• Summer 2003: Build production system for the annual data base

• End of 2003: Start production

Action: no further development

Action: in production

Action: SCM test runs

Action: 2 papers:-published in GRL (T,RH,Tb)-Cond. accepted at JHM (OI, EKF)

Action: still pending

Soil moisture analysis systems

Optimal Interpolation:• Used in the operational ECMWF-

forecast since 1999 (Douville et al., 2000)

• Fixed statistically derived forecast errors

• Criteria for the applicability of the method

- atmospheric and soil exceptions

- corrections when T and RH error are negatively correlated

Extended Kalman Filter:• Used in the operational DWD-

forecast since 2000 (Hess, 2001) *

• Updated forecast errors

• Criteria for the applicability of the method- no ‘direct’ atmospheric exceptions- soil exceptions still to be tested

* Changes:- Assimilation of 2m- T and RH, mw-Tb

- Model forecast operator accounts for water transfer between soil layers

- Test adaptive EKF

Experiment Design

Atm. initial conditions +dynamics forcing from

ECMWF reanalysis (ERA40)

Single-column model of theECMWF NWP model

+ microwave emissivity model

First guess: T2m,RH2m,HR(?)

Soil moisture analysis schemeOI or Extended Kalman Filter

Soil moisture Background error

Increments (daily)

Observations: T2m,RH2m,HR

Observation of precipitation + radiation

Production system for soil moisture

Starting point:• Experiments based on Single Column version of the ECMWF’s NWP

model (SCM)

Requirements:1. 0.2 x 0.2 regular lat/lon grid for Europe (15W-38E, 35N-72N)2. Computer time (cost efficiency)3. Annual database for 1.10.1999 – 31.12.2000 control system

Solutions:Add 1: run n x n SCMs over Europe (each SCM runs independently) Add 2: - run SCMs only for land points (about 25 000 SCMs)

- I/O consideration- High degree of parallelisation in an easy way balance saving of computer time and time for

programmingAdd 3: Supervisor Monitor Scheduler (SMS)

Production system for soil moisture(2)

Progress of work:

• Changes to the SCM source code– SCM structure has been changed to run n x n SCMs in one run

(single point area)

– I/O netcdf I/O grib

– OpenMP parallelization (up to 8 processes on one thread)

• Changes to the soil moisture analysis (SMA)– SMA has been changed to run n x n points in one run

– I/O netcdf I/O grib

• Forcing data– Composition of forcing data changed from one point to n x n points

– O netcdf O grib

• Control Structure– First SMS layout

1) Soil moisture analysis

1) Get forcing data from Mars archive2) Prepare data for SCM INPUT

1) Background run

1) Get forcing data from Mars archive2) Prepare data for SCM INPUT

1) Soil moisture perturbation

1) Final (soil moisture) trajectory 2) Check success of SMA (Costfunctions)

1) Forecast run

1) Final (soil temperature) trajectory2) Check success of STA (costfunctions)

1) Soil temperature analysis

1) Soil temperature perturbation

Production system for soil moisture (3)

• What is still missing?– Interpolation from gaussian grid to reg. 0.2 x 0.2 lat/lon grid

– Incorporation of ELDAS maps (e.g. land cover)

– Incorporation of ELDAS forcing data (precipitation, radiation)

– Archiving of output in MARS

– Observation (Re-analysis) data of 2mT and 2mRH for SMA +STA

– Post-processing routines for parameters especially asked for by ELDAS validation

– ECMWF orography problems (LW)

• Final tests

Time schedule(1)

Estimated Production Time:• Analysis for one day: - one SCM run for 1000 pixels needs 5 min on 8 nodes ~ 2 hours for 25000 pixels - 5 x SCMs are needed 10 hours for 25000 pixels

approx. 5-6 months for annual database further parallelization needed (splitting Europe into boxes) (MPI, distributed memory)

Time schedule(2)

Under normal circumstances:•6 weeks required to include missing bits and pieces

•2 weeks final tests

Start production by November/December

Expected Start of production:

?

Assimilating SHR, T+RH, T+RH+SHR

160 180 200 220 240 260 280julian day

15

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[%]

ObsCtrlEKF assim. T,RH,SHREKF assim. T,RHEKF assim. SHR

Corr. Bias RMS0.94 3.46 2.000.81 0.89 2.440.79 0.97 2.530.94 2.95 1.58

Soilmoisture

Days when SHR is available (50% data missing, 25% cloudy)

Variable SHR observation error depends on cloud fraction flag (how many hours are cloud free):• cloud fraction flag of neighbouring pixels• cloud fraction flag of pixel