Transcript WRF_EnKF_Overview_Feb08.ppt

WRF-EnKF Lightning Assimilation
Real-Observation Experiments
Overview
Cliff Mass, Greg Hakim, Phil Regulski
Department of Atmospheric Sciences
University of Washington
February 12, 2008
1
Overview




Project Review
Lightning Assimilation Technique Review
Model Estimate Experiments
Case Studies




December 2002 (Case 1 Review)
October 2004
November 2006
In-progress/Future work
2
Project Review

Review

Two working WRF-EnKF models

LTNG2 – Original


Tested successfully on Dec. 2002 regime
LTNG4 – Minimal counting technique

Tested successfully on Dec. 2002 regime
3
Project Review

Research Progress




Oct. 2004 Test Case - Analysis
Nov. 2006 Test Case - Analysis
Modifications to LTNG2 and LTNG4 models to improve
analysis and forecasts
In-progress



Forecast analysis of Oct. 2004 Test Case
Forecast analysis of Nov. 2006 Test Case
1-hr assimilation of cumulative convective rain rate data
(previously using 6-hr cumulative totals) for LTNG2 and
LTNG4 models
4
Lightning Assimilation Techniques
How model assimilates lightning: LTNG2

Original Lightning Experiment (LTNG2)






NLDN/LR lightning strike is detected
Lightning strike is converted into lightning rate from nearby LTNG
observations
Lightning rate converted into convective rainfall rate using
Pessi/Businger convective rain rate/lightning rate relationship
Relaxed WRF-EnKF quality control accepts more lightning strike
convective rainfall values when comparing to background forecasts
Convective rainfall (mm) is assimilated into WRF-EnKF
Successful testing on Dec. 2002 case


Apply to other test case events
Test model adjustments to improve performance
5
Lightning Assimilation Techniques
How model assimilates lightning: LTNG4

Minimal Counting Technique Lightning Experiment (LTNG4)







NLDN/LR lightning strike is detected
Lightning strike is converted into lightning rate from nearby LTNG
observations
Once any nearby lightning strikes are used to calculate a lightning density they
are no longer available as an assimilation point (although they are still used to
calculate LTNG densities)
Lightning rate converted into convective rainfall rate using Pessi/Businger
convective rain rate/lightning rate relationship
Relaxed WRF-EnKF quality control accepts more LTNG strike convective
rainfall values when comparing to background forecasts
Convective rainfall (mm) is assimilated into WRF-EnKF
Successful testing on Dec. 2002 case


Apply to other test case events
Test model adjustments to improve performance
6
Model Estimate Experiments
Can we further improve Dec 2002 performance?

Model-estimate and observations of cumulative convective precipitation calculated
by LTNG density occasionally have large innovations leading to large increments in
the model’s dynamical fields, possibly leading to locally unbalanced states


Minimal Counting Technique Lightning Experiment (LTNG4) w/ modifications
(LTNG5)




Same techniques as LTNG4 with upper bound (18mm)
Less improvement in analysis and forecasts
Original LTNG4 still best performing model to test further on new regimes
Original Lightning Experiment (LTNG2) w/ modifications (LTNG6)




Set a upper bound on assimilated cumulative convective precipitation
Same techniques as LTNG2 with upper bound (18mm)
Less improvement in analysis and forecasts
Original LTNG2 still best performing model to test further on new regimes
Another solution
Reduce cumulative value of convective rain assimilated from 6- to 1-hr block
(In-progress)

7
Case Studies (Case 1 Review)

Case #1: December 16-21, 2002

Analysis
Extra-tropical cyclone minimum SLP with new
modifications
 SLP fields
 WRF-EnKF v. Observations

8
Case Study #1 – December 2002
Minimum SLP recorded at extra-tropical cyclone’s center
Limiting upper bound of cumulative convective
precipitation degrades analysis performance (LTNG5/6)
9
Case Study #1 – December 2002
SLP Analysis Fields
Correct location and intensity of SLP cyclone center for LTNG assimilations
10
Case Study #1 – December 2002
WRF-EnKF v. Observations: Integrated Error of SLP
LTNG assimilation reduces error over control
11
Case Studies

Case #2: October 4-7, 2004

Analysis
Extra-tropical cyclone minimum SLP
 SLP, H500 fields
 WRF-EnKF v. Observations


Number of LTNG strikes during test case is much
smaller than Dec. 2002 case
12
Case Study #2 – October 2004
Minimum SLP recorded at extra-tropical cyclone’s center
LTNG assimilated from 04/00 – 07/18
LTNG4 more accurately simulates min. SLP
depth of extra tropical cyclone
13
Case Study #2 – October 2004
SLP Analysis Fields
Correct location and intensity of SLP cyclone center for LTNG assimilations
14
Case Study #2 – October 2004
H500 Analysis Fields
Correct location and intensity of H500 center for LTNG assimilations
15
Case Study #2 – October 2004
H500 Analysis Fields
LTNG4 pulls location of upper-level cyclone center too close to LTNG observations
Reducing to 1-hr cumulative convective rain totals could weigh OBS correctly
16
Case Study #2 – October 2004
WRF-EnKF v. Observations: Integrated Error of SLP
LTNG assimilated from 04/00 – 07/18
17
Case Study #2 – October 2004
WRF-EnKF v. Observations: Cloud top temperature v. Satellite
LTNG2: 10/08 00
18
Case Study #2 – October 2004
WRF-EnKF v. Observations: Cloud top temperature v. Satellite
LTNG4: 10/08 00
19
Case Studies

Case #3: November 8-12, 2006

Analysis
Extra-tropical cyclone minimum SLP
 SLP, H500 fields
 WRF-EnKF v. Observations

20
Case Study #3 – November 2006
Minimum SLP recorded at extra-tropical cyclone’s center
Only LTNG assimilated hours
21
Case Study #3 – November 2006
SLP Analysis Fields
Correct location and intensity of SLP cyclone center for LTNG assimilations
22
Case Study #3 – November 2006
H500 Analysis Fields
Correct location and intensity of H500 center for LTNG assimilations
23
Case Study #3 – November 2006
WRF-EnKF v. Observations: Integrated Error of SLP
LTNG assimilated from 08/00 – 11/18
24
Case Study #3 – November 2006
WRF-EnKF v. Observations: Cloud top temperature v. Satellite
LTNG2: 11/10 12
25
Case Study #3 – November 2006
WRF-EnKF v. Observations: Cloud top temperature v. Satellite
LTNG4: 11/10 12
26
In-progress/Future Work

In-Progress





Future Work




Reduce WRF cumulative convective precipitation assimilation from 6- to 1-hr
to avoid unbalanced states
24-hr Forecasts for Oct 2004 Case
24-hr Forecasts for Nov 2006 Case
Investigate robustness of Pessi/Businger lightning rate/convective rain rate
relationship
Test Case #4 – December 2006
Implement UW-ATMS lightning rate/convective rain rate relationship
Investigate lightning/graupel relationship
Questions/Comments?
27