Development of a hybrid probabilistic forecast scheme for ... fileIntroduction Procedure Results...
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Introduction Procedure Results Summary
Development of a hybrid probabilistic forecastscheme for post-frontal shower precipitation
Tanja Weusthoff
Institute for Meteorology and Climatology,Leibniz Universitat Hannover
PhD-Students and Post-Docs Meeting on QPF 06.03.2007
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary
Contents
IntroductionSynoptic situationObjectivesDefinitions
ProcedureData materialCluster tracking
Some resultsGeneral observationsGeometrical structureInvestigation of rain rates
Summary and Outlook
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Contents
IntroductionSynoptic situationObjectivesDefinitions
ProcedureData materialCluster tracking
Some resultsGeneral observationsGeometrical structureInvestigation of rain rates
Summary and Outlook
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Post-frontal situation
I Rear side of coldfront
I Trough over NorthSea or AtlanticOcean
Berliner Wetterkarte.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Post-frontal situation
I Rear side of coldfront
I Trough over NorthSea or AtlanticOcean
I Cold, wet air aboverelatively warmsurface
Berliner Wetterkarte.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Post-frontal situation
I Rear side of coldfront
I Trough over NorthSea or AtlanticOcean
I Cold, wet air aboverelatively warmsurface
I Unstablestratification up to3 to 7 km
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Post-frontal situation
I Rear side of coldfront
I Trough over NorthSea or AtlanticOcean
I Cold, wet air aboverelatively warmsurface
I Unstablestratification up to3 to 7 km
I Typical convectivestructure
DLR.Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Post-frontal situation
I Rear side of coldfront
I Trough over NorthSea or AtlanticOcean
I Cold, wet air aboverelatively warmsurface
I Unstablestratification up to3 to 7 km
I Typical convectivestructure
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Post-frontal situation
I Rear side of coldfront
I Trough over NorthSea or AtlanticOcean
I Cold, wet air aboverelatively warmsurface
I Unstablestratification up to3 to 7 km
I Typical convectivestructure
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Objectives
I Analysis of post-frontal shower precipitation and derivation ofprinciples.
I Improvement of understanding of structure and developmentof post-frontal shower cells.
I Validation of model forecast.
I Development of a hybrid probabilistic forecast scheme forpost-frontal shower precipitation:
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Objectives
I Analysis of post-frontal shower precipitation and derivation ofprinciples.
I Improvement of understanding of structure and developmentof post-frontal shower cells.
I Validation of model forecast.
I Development of a hybrid probabilistic forecast scheme forpost-frontal shower precipitation:
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Objectives
I Analysis of post-frontal shower precipitation and derivation ofprinciples.
I Improvement of understanding of structure and developmentof post-frontal shower cells.
I Validation of model forecast.
I Development of a hybrid probabilistic forecast scheme forpost-frontal shower precipitation:
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Objectives
I Analysis of post-frontal shower precipitation and derivation ofprinciples.
I Improvement of understanding of structure and developmentof post-frontal shower cells.
I Validation of model forecast.
I Development of a hybrid probabilistic forecast scheme forpost-frontal shower precipitation:
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Planned forecast scheme
Hybrid forecasting scheme for convective shower precipitationbehind cold fronts over Germany:
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Planned forecast scheme
Hybrid forecasting scheme for convective shower precipitationbehind cold fronts over Germany:
Step 1 Deterministic forecast of cold fronts, related post-frontalconvective precipitation fields and mean rain area motionfield based on NWP model output (LM of the DWD).
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Planned forecast scheme
Hybrid forecasting scheme for convective shower precipitationbehind cold fronts over Germany:
Step 1 Deterministic forecast of cold fronts, related post-frontalconvective precipitation fields and mean rain area motionfield based on NWP model output (LM of the DWD).
Step 2 Probabilistic forecast of
(i) number of rain areas,(ii) total rain area,(iii) areal precipitation,(iv) local precipitation likelihood,(v) mean maximum local precipitation,(vi) mean rain duration and other quantities.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Planned forecast scheme
Hybrid forecasting scheme for convective shower precipitationbehind cold fronts over Germany:
Step 1 Deterministic forecast of cold fronts, related post-frontalconvective precipitation fields and mean rain area motionfield based on NWP model output (LM of the DWD).
Step 2 Probabilistic forecast of
(i) number of rain areas,(ii) total rain area,(iii) areal precipitation,(iv) local precipitation likelihood,(v) mean maximum local precipitation,(vi) mean rain duration and other quantities.
Result Hybrid probabilistic forecast scheme.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Some Definitions
Rain areaArea in radar data whererain rate R > threshold(here: 0.05 mm / 5 minwhich is about 19 dBz).
Maximum
Single cell, cluster
Maximum number
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Some Definitions
Rain area
MaximumPixel of 1 km2 areawhich is a localmaximum of rain rate,also: Peak.
Single cell, cluster
Maximum number
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Some Definitions
Rain area
Maximum
Single cell, cluster
Single cell Rain areawith onemaximum.
Cluster Rain areawith morethan onemaximum.
Maximum number
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Situation Objectives Definitions
Some Definitions
Rain area
Maximum
Single cell, cluster
Maximum numberNumber of maximainside a cluster.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Data material Cluster tracking
Contents
IntroductionSynoptic situationObjectivesDefinitions
ProcedureData materialCluster tracking
Some resultsGeneral observationsGeometrical structureInvestigation of rain rates
Summary and Outlook
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Data material Cluster tracking
The RZ composite of the DWD
I Composite of 16 local radarstations distributed overGermany: DWD Radarverbund.
I Horizontal resolution: 1 km.
I Temporal resolution: 5 min.
I Rain rates with0.01 mm / 5 min.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Data material Cluster tracking
Preparation of data
I Identifying days with post-frontal showers (17 so far processedin 2004 and 2006),
I extracting area of interest,
I label rain areas,
I determination of characteristics:
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Data material Cluster tracking
Preparation of data
I Identifying days with post-frontal showers (17 so far processedin 2004 and 2006),
I extracting area of interest,I label rain areas,I determination of characteristics:
0 time
1 label number
2 area
3 maxima number
4 mean rain rate
5 rain sum
6 maximum rain rate
7 x-value
8 y-valueTanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Data material Cluster tracking
Cluster tracking: searching box
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Data material Cluster tracking
Example data set
18 precursor
19-22 successor
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Data material Cluster tracking
Transitions
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Data material Cluster tracking
Transitions
Five different life stages could be identified:
(i) genesis
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Data material Cluster tracking
Transitions
Five different life stages could be identified:
(i) genesis
(ii) growth(including merging)
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Data material Cluster tracking
Transitions
Five different life stages could be identified:
(i) genesis
(ii) growth(including merging)
(iii) stagnation
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Data material Cluster tracking
Transitions
Five different life stages could be identified:
(i) genesis
(ii) growth(including merging)
(iii) stagnation
(iv) decrease(including splitting)
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary Data material Cluster tracking
Transitions
Five different life stages could be identified:
(i) genesis
(ii) growth(including merging)
(iii) stagnation
(iv) decrease(including splitting)
(v) dissolving
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Contents
IntroductionSynoptic situationObjectivesDefinitions
ProcedureData materialCluster tracking
Some resultsGeneral observationsGeometrical structureInvestigation of rain rates
Summary and Outlook
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Diurnal cycle
... of number of rain areas
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Diurnal cycle
... of number of rain areas and number of maxima per rain area.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Diurnal cycle
... of precipitation covered area
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Diurnal cycle
... of precipitation covered area and area per maximum.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Frequency distribution of maximum number: PND
N(p) = N0 · pc0 N0 = 0.72 c0 = −2.21
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
PND variation from day to day
(17 days)
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
PND variation from day to day
(17 days)
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Diurnal variation of PNDfor all 17 days, intervall length = 3h
I the variance from day to day is slightly larger than the diurnalvariance.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Spatial variation of PND
Theusner, 2007
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Spatial variation of PND
Theusner, 2007
I The same slope of PND is observed in all four domains.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Area size distribution
Theusner, 2007
I ... can be fitted by lognormal funcions for each maximumnumber.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Distribution of rain rates- Euler analysis -
I Analysing actual rain rates foreach time step.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Distribution of rain rates- Euler analysis -
I Analysing actual rain rates foreach time step.
I Determination of rain sum andarea of clusters with respect totheir maximum number.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Rain rate per maximum for cluster of different maximumnumber
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Rain rate per maximum for cluster of different maximumnumber
p < 10 rain sum ∝ p2
p > 10 rain sum ∝ p
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Area per maximum for cluster of different maximumnumber
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Area per maximum for cluster of different maximumnumber
p < 10 area ∝ p2
p > 10 area ∝ p
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Development of individual rain areas- Lagrangian analysis -
I Cluster development is verycomplex→ combination of individualdevelopment of embedded cellsand interactions with other cellsand clusters.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Development of individual rain areas- Lagrangian analysis -
I Cluster development is verycomplex→ combination of individualdevelopment of embedded cellsand interactions with other cellsand clusters.
I Differentiation between singlecells and single clusters andclusters that are involved inmerging and splitting processes.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Role of single cells
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Transition likelihoods (n → m)
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Transition likelihoods (n → m)
(i) genesis
(ii) growth (including merging)
(iii) stagnation
(iv) decrease (including splitting)
(v) dissolving
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Transition likelihoods (n → m)
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Transition likelihoods (n → m)
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Transition likelihoods (n → m)
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Transition likelihoods (n → m)
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Simple growth model
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Simple growth model
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Simple growth model
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Rain sum over whole life time of single cells
I Maximum rain amount is observed within first half of life time.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary General observations Geometrical structure Rain rates
Rain sum over whole life time of single cells
I rain sum ∝ life span2
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary
Contents
IntroductionSynoptic situationObjectivesDefinitions
ProcedureData materialCluster tracking
Some resultsGeneral observationsGeometrical structureInvestigation of rain rates
Summary and Outlook
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary
Summary
I Geometrical structure of the post-frontal precipitation fieldcan be described by simple analytical functions anddistributions⇒ Dissertation Michael Theusner (Leibniz UniversitatHannover, 2007)
I Development of convective rain areas is in principleunderstood.
I Further research concentrates on:I Rain amount of clusters with complex life cycle.I Analytical description of development processes.I Development of forecast scheme.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary
Summary
I Geometrical structure of the post-frontal precipitation fieldcan be described by simple analytical functions anddistributions⇒ Dissertation Michael Theusner (Leibniz UniversitatHannover, 2007)
I Development of convective rain areas is in principleunderstood.
I Further research concentrates on:I Rain amount of clusters with complex life cycle.I Analytical description of development processes.I Development of forecast scheme.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary
Summary
I Geometrical structure of the post-frontal precipitation fieldcan be described by simple analytical functions anddistributions⇒ Dissertation Michael Theusner (Leibniz UniversitatHannover, 2007)
I Development of convective rain areas is in principleunderstood.
I Further research concentrates on:I Rain amount of clusters with complex life cycle.I Analytical description of development processes.I Development of forecast scheme.
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary
Applications
I Development and test of forecast scheme.
I Verification of model output with respect to the precipitationstructure ⇒ LMK.
I Nowcasting for smaller catchment areas.
I ...
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary
Applications
I Development and test of forecast scheme.
I Verification of model output with respect to the precipitationstructure ⇒ LMK.
I Nowcasting for smaller catchment areas.
I ...
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary
Applications
I Development and test of forecast scheme.
I Verification of model output with respect to the precipitationstructure ⇒ LMK.
I Nowcasting for smaller catchment areas.
I ...
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary
Applications
I Development and test of forecast scheme.
I Verification of model output with respect to the precipitationstructure ⇒ LMK.
I Nowcasting for smaller catchment areas.
I ...
Tanja Weusthoff Post-frontal shower precipitation
Introduction Procedure Results Summary
Thank you!
Tanja Weusthoff Post-frontal shower precipitation