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Assimilation of radar data - research plan Marián Jurašek Slovak Hydrometeorological Institute.

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Presentation on theme: "Assimilation of radar data - research plan Marián Jurašek Slovak Hydrometeorological Institute."— Presentation transcript:

1 Assimilation of radar data - research plan Marián Jurašek Slovak Hydrometeorological Institute

2 Introduction –in June 2003 prepared proposal of workplan for research of radar data assimilation for ALADIN –radar data - essential for mesoscale assimilation –available radar data: –reflectivity –instantaneous rainrate –cumulated rainfall –doppler wind, wind shear, turbulence –vertical wind profile –quantities from multiple polarisation measurements ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

3 Which radar data? –each has advantages and disadvantages –not all available on all radar sites –reflectivity seems to be available on most European sites –not common form of data: –PPI images –volume data ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

4 The philosophy –learning from satellites –remote sensing process is complex and nonlinear we should assimilate quantity close to measured (reflectivity instead of rainrate) we should assimilate quantity close to measured (reflectivity instead of rainrate) derived quantities contain hardly correctable errors coming from mixture of real data, model field and empirical assumptions about the atmosphere derived quantities contain hardly correctable errors coming from mixture of real data, model field and empirical assumptions about the atmosphere ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

5 The philosophy (2) –observation operator must simulate the reflectivity for each radar development of system for radar data against model data monitoring development of system for radar data against model data monitoring –biases and big errors cannot be handled by 3D/4D-Var software for detection and removal of corrupted data software for detection and removal of corrupted data ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

6 The philosophy (3) study of space- and time structure of biases between simulated and observed data for bias correction study of space- and time structure of biases between simulated and observed data for bias correction each radar processed independently each radar processed independently thinning of too dense data consistently with the resolution of the analyses thinning of too dense data consistently with the resolution of the analyses ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

7 The philosophy (4) –very accurate modelling of physical process of observation precisely interpolating / averaging model variables along the radar beam path precisely interpolating / averaging model variables along the radar beam path –physical part of observation operator should be prepared by radar specialists ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

8 Which model? –reflectivity is sensitive to cloud properties simulation depends on clouds representation in model (subgrid-scale diagnostic cloud in large- scale physics or detailed prognostic mesoscale microphysics) simulation depends on clouds representation in model (subgrid-scale diagnostic cloud in large- scale physics or detailed prognostic mesoscale microphysics) problem: we must work on both ALADIN and AROME model problem: we must work on both ALADIN and AROME model advantage: we will be prepared for ARPEGE (resp. IFS) advantage: we will be prepared for ARPEGE (resp. IFS) ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

9 Which model? (2) –observation operator need not to know how the fields are calculated should be developed relatively independent from model physics –we need only interface with each model physics to get field for reflectivity simulation ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

10 Things To Do –get samples of very good quality radar reflectivity data –get idea of fields needed to simulate reflectivity –literature study –study of existing radar simulation models (DWD/HIRLAM) –get simple (to start with) reflectivity simulation formulae ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

11 Things To Do (2) –specify observation operator by: –list of necessary model fields for interpolation –list of necessary information about observation for screening and minimisation –obs. operator should access to the radar data by radar beam rather that by gridded pixels like for imagery - processing volume radar data ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

12 Things To Do (3) –carefully specify the technical implementation of previous things –parallelization –minimise the disturbance for others developers –universal structure compatible with next similar obs. operator (= with slanted interpolation path) ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

13 Things To Do (4) –implement radar data into the ODB processing –radar data only loaded to the model –check CPU and memory costs –implement direct interpolation of model fields –extracting grided fields from physics (or historical files) –interpolation/average to the radar beam path –beam feeling problem ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

14 Things To Do (5) –convert model field to the reflectivity, compute and store difference with observation –storing differences in ODB –computation of the Jo in screening run ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

15 Things To Do (6) –study monitoring statistics –design bias correction, screening, thinning and quality control –implementation to the screening part or to the preprocessing program –crucial for success of reflectivity assimilation ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

16 Things To Do (7) –code tangent linear and adjoint of obs. Operator –functional 3DVar minimisation –check speed and quality –simulate one radar pixel –check correction of atmospheric field by 3DVar ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

17 Things To Do (8) –study the impact of reflectivity assimilation to forecast –for ALADIN and AROME –for different situations (front, strong convection) –for different resolutions (10 km, 2.5 km) –check spin up ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

18 Things To Do (9) –run several cycles of data assimilation to see the cumulative and beneficial effect –background should be closer to the radar –retune preprocessing and analysis parameters –improve obs. operator ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003

19 Thank You for your attention! ALADIN/RC LACE Data assimilation miniworkshop Budapest, October 2003


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