Christoph zingerle and pertti nurmi
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Christoph Zingerle and Pertti Nurmi. Utilisation of satellite data in the verification of HIRLAM cloud forecasts. Contents. verification, the task the forecasting system HIRLAM observations = satellite data making forecast and observation comparable an example summary future. Task.

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Utilisation of satellite data in the verification of HIRLAM cloud forecasts

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Christoph zingerle and pertti nurmi

Christoph Zingerle and Pertti Nurmi

Utilisation of satellite data in the verification of HIRLAM cloud forecasts


Utilisation of satellite data in the verification of hirlam cloud forecasts

Contents

  • verification, the task

  • the forecasting system HIRLAM

  • observations = satellite data

  • making forecast and observation comparable

  • an example

  • summary

  • future


Utilisation of satellite data in the verification of hirlam cloud forecasts

Task

  • Verification of the HIRLAM cloud forecast

-detection of deficiencies in the cloud forecast

scheme

-feasibility of different approaches to verification

using satellite data

-methodology of verifying cloud forecasts and its

operational implementation


Utilisation of satellite data in the verification of hirlam cloud forecasts

HIRLAM at FMI

  • HIgh Resolution Limited Area Model

- FMI is running the reference HIRLAM (RCR) operationally

-resolution 0.2 deg horizontal (438x336 grid points, ~ 22 km)

40 levels vertical (up to 10 hPa)

- semi-lagrangian advection

- 3D–Var analysis (no satellite data)

- lateral boundary conditions from ECMWF

-Denmark, Finland, Iceland, Ireland, Netherlands, Norway,

Spain and Sweden (France)


Utilisation of satellite data in the verification of hirlam cloud forecasts

HIRLAM RCR domain


Utilisation of satellite data in the verification of hirlam cloud forecasts

Satellite Observations

  • satellite data at FMI from:

- METEOSAT 7/8:

high resolution (temporal and spatial)

coarse resolution at the edges - like Finland - with limb darkening

- NOAA polar orbiting satellites

high spatial resolution

coarse temporal resolution


Utilisation of satellite data in the verification of hirlam cloud forecasts

Observation – Forecast

  • Model to Satellite:

  • Satellite to Model:

- transferring the observations

to parameters forecasted by

the model

- Cloud classification scheme

generally thresholding methods

based on typical cloud properties

- transferring the parameters

forecasted by the model to

observations

- Radiative Transfer Model

uses model data to simulate

observed radiances and Tb’s


Utilisation of satellite data in the verification of hirlam cloud forecasts

Model to Satellite

  • Radiative Transfer Model (RTM)

- RTTOV 7

- a fast RTM for the assimilation of satellite data

calculates radiances (and Tb's) as seen by a satellite instrument

uses profiles oftemperature

humidity

cloud fraction

cloud liquid water

cloud ice water

ozone

surface properties


Utilisation of satellite data in the verification of hirlam cloud forecasts

Model to Satellite

  • 'synthetic' NOAA AVHRR image (10.8µ)

- 24 h forecast from HIRLAM

- AVHRR because of the

high resolution provided

even at the poles


Utilisation of satellite data in the verification of hirlam cloud forecasts

Observation Re-sampling

  • NOAAAVHRR satellite image

- re-sampling needed

- preprocessed (AAPP) AVHRR image (calibrated and navigated)

pixel center in the grid-box corresponding to the HIRLAM grid

pixel assigned to this grid-box

- Assumptions:

HIRLAM grid value represents

average over all the values in box

neighbouring pixels don't differ much

from each other


Utilisation of satellite data in the verification of hirlam cloud forecasts

full resolution, 30.4.2004 (10.8µ)

after re-sampling, 30.4.2004 (10.8µ)


Utilisation of satellite data in the verification of hirlam cloud forecasts

simulated, 30.4.2004 (10.8µ)

observed, 30.4.2004 (10.8µ)


Utilisation of satellite data in the verification of hirlam cloud forecasts

Difference:

observed - simulated

Difference > 40 K:

Model error?


Utilisation of satellite data in the verification of hirlam cloud forecasts

simulated

observed

Summary distributions

relative frequency of Tb

observed / simulated Tb


Utilisation of satellite data in the verification of hirlam cloud forecasts

Summary

  • RTTOV

- a tool to simulate satellite measurements as close as possible

- surface parameters and transmission (clouds) dependent

  • observations

- simple re-sampling of NOAA AVHRR data is sufficient

- re-sampling will be more sophisticated for other instruments

  • verification of HIRLAM

- cloud forecast scheme not yet verified extensively

- approach to verification looks promising


Utilisation of satellite data in the verification of hirlam cloud forecasts

Future

  • examine approaches to verification

- satellite to observation approach (SAFNWC software)

- pattern recognition methods

  • expand to other satellite data (instruments)

- Meteosat data over Europe

- polar orbiting satellites over Scandinavia and Nordic Countries

  • operational verification

- refine methodology to verify cloud forecasts

- improve the operational verification package of FMI


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