Advanced AHW Diagnostics

Ryan D. Torn, Univ. Albany SUNY

Chris Davis, NCAR

• AHW Assimilation System Diagnostics• AHW Forecast Diagnostics• Ready-to-go HWRF Diagnostics

Pressure Tendency• Measure of the

imbalance in initial conditions

• Computed using high-frequency model output. Files processed using short fortran program that writes netcdf tendency file.

• Plotted via NCL

Observation Verification

• Large-scale model errors and biases

• Windowing by region can demonstrate more detailed model bias information

• Computed within AHW assimilation system, could extend to HWRF if grids are made available

• NCL or Matlab plotting

Near-TC Verification• Compute errors relative to

obs. near TC. Primarily for diagnosing near-storm environmental errors

• Done from fortran program that windows observations based on distance to TC

• Aggregation using fortran program

Inner-Core Verification

• Comparison against aircraft and dropsonde obs. in vortex-relative space. Eliminates position-related errors.

• Computed via fortran program that reads WRF files and obs. from DA system and writes model estimates at observation locations.

• Plotting with Matlab, with transition to NCL

Temperature

Wind Speed

Prior Analysis Obs.

Lagrangian Diagnostics• Used extensively

during PREDICT to evaluate processes that lead to genesis

• Each Lagrangian metric is computed using a separate fortran program, could be merged into single application

• Plotting via NCLMetrics: circulation, thickness, humidity, vertical shear, divergence, precipitation, average winds

Histogram Verification• Shows conditional biases• In assimilation system,

computed via separate fortran program, aggregated via Matlab script, output as netcdf

• AHW forecasts have all-in-one fortran program

• Calculations can include equitable threat scores

• Plotting accomplished via Matlab with transition to NCL

Davis et al. 2010, WAF

Climatology Comparisons• Shows whether the model

can replicate the observed distribution of a quantity, shows systematic biases

• Easy to compute once you have quantities

Davis et al. 2010, WAF

Environment ShearRemove effect of storm from estimate of vertical shear between two levels (subscripts 1 and 2) by removing vertical difference of storm-related vorticity () and divergence ()

2 1 022 1 2 1

0

for( ) ; 0 on lateral boundaries

0

r r

r r

2 1 022 1 2 1

0

for( ) ; 0 on lateral boundaries

0

r r

r r

2 1 2 1ˆ ( ); ( )v k v

2 1envv v v v v

200 mb – 900 mb wind difference (and 900 mb relative vorticity): EPAC developing composite

Due to storm

200 mb – 900 mb wind difference with storm removed:EPAC developing composite

Davis et al., 2008: MWR

HWRF Histograms

• Convert ATCF to netcdf

• Histogram constructed via Matlab

• Plotting either via Matlab or NCL

HWRF Histograms

• Convert ATCF to netcdf

• Histogram constructed via Matlab

• Plotting either via Matlab or NCL

Future Diagnostics

• H*WIND comparisons (either RMS difference or quadrant-by-quadrant fraction coverage, similar to Marchok calculation)