advanced objective dvorak technique (aodt) afwa/xogm

AdvancedAdvancedObjective Dvorak Objective Dvorak Technique (AODT)Technique (AODT)

AFWA/XOGMAFWA/XOGM

UW-CIMSS Advanced Objective Dvorak UW-CIMSS Advanced Objective Dvorak Technique (AODT)Technique (AODT)

• Tim Olander and Chris VeldenTim Olander and Chris Velden• University of Wisconsin - MadisonUniversity of Wisconsin - Madison• Cooperative Institute for Meteorological Satellite StudiesCooperative Institute for Meteorological Satellite Studies

In cooperation with :In cooperation with :

• Jeff HawkinsJeff Hawkins• Naval Research Laboratory - Monterey, CANaval Research Laboratory - Monterey, CA• Office of Naval ResearchOffice of Naval Research

Material for this training module largely comes from:

Advanced Objective Advanced Objective Dvorak Technique (AODT)Dvorak Technique (AODT)

- What is the AODT?- What is the AODT?

- How does it work?- How does it work?

- Why use it?- Why use it?

- How will we use it here? - How will we use it here?

OverviewOverview

What is the AODT?What is the AODT?

AAODT is a computerized method for ODT is a computerized method for determining the intensity of tropical determining the intensity of tropical cyclones. It was originally developed by cyclones. It was originally developed by the University of Wisconsin, and we are the University of Wisconsin, and we are able to perform some AODT functions able to perform some AODT functions currently.currently.

Ok, so how does it work?Ok, so how does it work?

Advanced Objective Advanced Objective Dvorak Technique (AODT)Dvorak Technique (AODT)

AODT MethodologyAODT Methodology


• Identification of two environmental temperatures (BTs)Identification of two environmental temperatures (BTs)– Uses IR data only– Eye Temperature (0-40 km)– Cloud Temperature (26-136 km)

• Scene identification performedScene identification performed– AODT is only performed for five types of features: – Eye, Embedded Center, CDO, Curved Band, and Shear– SIDAS version handles all five features– Based on histogram and Fourier Transform Analysis

AODT MethodologyAODT Methodology• Determination of the cloud pattern is performed

objectively (in other words, by the computer) by examining area histograms of cloud top temperatures and corresponding Fourier Analysis for the eye region and surrounding cloud region. Based on this analysis, five scene patterns can be categorized by AODT: Eye, Central Dense Overcast, Embedded Center, Curved Band, and Shear.


• Storm Center Location Storm Center Location

– The only user input is the specification of the storm center location• AODT depends on a fixer’s position to work

– AODT only does intensities

• EYE determination

– If the storm has an eye, it uses the warmest pixel temperature within a 40 km radius of the chosen storm center – Warm values represent ocean surface or low cloud within the eye– This value is retained as the 'eye temperature'.

ODT MethodologyODT Methodology

Warmest value = 'eye temperature'Warmest value = 'eye temperature'

AODT MethodologyAODT Methodology• EYE determination (con’t)

– AODT analyzes temperatures on concentric rings (1 pixel wide) centered on the eye between 24 km and 136 km from the eye location (this range was empirically determined by many observations of coldest ring radii).

– For GOES data with 4km pixel resolution, this results in a total of 28 rings that are analyzed to determine the 'surrounding temperature'. – In addition, a continuous ring of cold temperatures surrounding the eye is more indicative of an organized (and more intense) storm than one with breaks in

the convection.– Therefore, the warmest temperature found on each ring is identified and stored, with the coldest of these retained as the final surrounding temp value. – AODT does not reposition the storm center, since it has been found that the subsequent analysis of the surrounding temperature field may be improperly

influenced by this adjustment in some cases ('false' eyes).

ODT MethodologyODT Methodology

AODT MethodologyAODT MethodologyThe warmest temperature is found on each ring...

AODT MethodologyAODT MethodologyThis ring has “Light Grey”as its warmest temp.

AODT MethodologyAODT MethodologyOf those temps that areleft, the coldest is takenas the surrounding ring


• “No Eye” Condition – AODT can handle Central Dense Overcast (CDO)/Embedded Center– Temperatures near the storm center are dominated by cold cloud tops and a warm eye is not resolvable. – The value of the pixel at the user-defined storm center location is used as the 'eye’ temperature– Shear scenario is also detected in AODT – The CURVED BAND, SHEAR, CDO/EMBD CTR ARE AVAILABLE IN SIDAS II, but not the older SIDAS I.

AODT MethodologyAODT Methodology• Initial intensity estimate determined Initial intensity estimate determined (Raw T#)(Raw T#)

– Based on original Dvorak Rules for different patterns and cloud top temperatures. Eye temperature serves as adjustment

• Use history file with previous storm analysis data Use history file with previous storm analysis data (Final T#)(Final T#)

– Provide data for 12-hour time weighted time averaging scheme– This means we have to perform AODT after every fix– Data is saved in SIDAS interface

• Implementation of Dvorak Rule 9 for weakening storms Implementation of Dvorak Rule 9 for weakening storms (CI#)(CI#)– Corrects underestimate bias in weakening storms– Hold T# constant for 12 hours after initial weakening, add 1.0 T# until dissipation or

restrengthening– Not currently implemented in SIDAS

AODT PurposeAODT PurposeOk, but why use it?Ok, but why use it?

1. 1. It’s It’s OBJECTIVEOBJECTIVE• Doesn’t depend on opinions of human beingDoesn’t depend on opinions of human being• Done the same way every timeDone the same way every time• Can be more accurate (sometimes)Can be more accurate (sometimes)

2. 2. It’s It’s FASTFAST• Computer derivedComputer derived• Some storms are harder than othersSome storms are harder than others

3. 3. It’s It’s WANTEDWANTED•JTWC has formally requested that we do thisJTWC has formally requested that we do this•Test mode only for nowTest mode only for now

Current User StatusCurrent User Status

Operational UseOperational Use• NOAA/NESDIS Satellite

Analysis Branch

• NHC/Tropical Analysis Forecast Branch

• Joint Typhoon Warning Center

Experimental UseExperimental Use• Air Force Weather

Agency

• Central Pacific Hurricane Center

• Australian Bureau of Meteorology

• Japanese Meteorological Agency

• JTWC uses it on NSDS-EJTWC uses it on NSDS-E• SAB uses it in MCIDASSAB uses it in MCIDAS

• How will we use it here?How will we use it here?– SIDAS IISIDAS II– New AODT option in the interaction menuNew AODT option in the interaction menu

AODT IS AODT IS ALWAYSALWAYS TO BE PERFORMED TO BE PERFORMED AFTERAFTER YOU COMPLETE YOUR OWN INDEPENDENT YOU COMPLETE YOUR OWN INDEPENDENT ANALYSIS!ANALYSIS!

AODT ImplementationAODT Implementation

To Begin an AODT calculation, first you must estimate the position of the low level circulation center (LLCC) manually.

Use the “Lat/Lon Browse” feature in SIDAS II to determine the lat/long of the LLCC.

You can interactively roam on the satellite graphic to determine the lat/long of the LLCC.

Next, go to the “Interaction Mode” pull-down menu and select [AODT]. Next, hit the LLCC position on the satellite graphic – once!

The AODT sub-window now appears. Hit [OK]

The AODT graphical user interface (GUI) will now say ‘Calculating AODT’ inside the GUI textbox. This might take 30-60 seconds. Please wait.

The AODT GUI displays a spot analysis calculation. This calculation has not been initialized, so it is quite possible that this might be a very wildly inaccurate number. Please do not worry about this first number when you are starting a storm for the first time.

We are going to properly initialize AODT now.Go to the “IC value” pull-down menu and select the T number that you chose in your manual Dvorak classification. ONLY DO THIS FOR THE INITIAL AODT calculation for any storm.

Notice that this storm is started as a T1.5. I could have chosen T1.0, depending on the intial intensity of the storm.

Also, notice that I could have chosen a higher T number – this can be done if you forgot to start AODT normally, but the results will be less accurate if you do this…...

So start on time!

The text window of the AODT GUI now says “Recalculate AODT”. Just hit the [OK] button here!

The AODT GUI displays a a properly initialized analysis calculation. Since This calculation is your very first one, it will almost always be identical to the “IC value” that you selected earlier. This is not a problem.

1. Hit the button [Start new file]. You will see a windows file directory interface appear, as seen here here in the upper left hand corner. Navigate to

L:\tropical\AODT\2004

2. Note:

“L: drive” is mounted to nt18, under the “z_drive partition”.

See Mr. McCrone for set up help

1. In the windows file directory interface, navigate to the ocean basin that the storm is in (SIO, NWPAC, ATL, etc).

Enter a file name that describes the storm. An example would

be: TC-14S-monty. The file system will put the “.odt” extension on the end of the file.

JUST HIT [OK] here.

You may now return to normal SIDAS ops.

You have now correctly started a storm.

Normally, you will be doing another manual position fix in 3 hours. At this point, you will load the new image into SIDAS II, then get your fix position, similar to the process described earlier. Then you hit [AODT] again… & select the LLCC from your fix (only hit it once!)

*

The AODT GUI comes up again. Hit the button called

[Select AODT history file]. A windows file select interface will appear.

A windows file select interface will appear.

A windows file select interface will appear. Select the file that is connected with the storm that you are analyzing.

The text window of the AODT GUI now says “Recalculate AODT”. Just hit the [OK] button here!

The AODT GUI displays a a time averaged analysis calculation. This calculation may be a number like T1.8, or 4.7, etc.

There are two pieces of info to record on your fix bulletin: The CI # and the Scene type.

You need to save this data! To save, you hit the [Write History] button once!

You have saved this data! Just hit the [OK] button once!

OPTIONAL: you can review the history of the AODT!

OPTIONAL: you can review the history of the AODT! Just hit the [Display History] button once! Otherwise, you can hit [Cancel] and return to ordinary SIDAS ops.

Normally, you will be doing continual manual position fix in 3 hours until the storm is finalled. You can repeat this process for a given storm by following the instructions of this ppt show (go back to the slide with the big red asterisk

*

AODT Past PerformanceAODT Past Performance

Year, Month, Date, Time (GMT)

ODT Past PerformanceODT Past Performance

Legend : TAFB - Tropical Analysis Forecast Branch - NOAA/NCEPSAB - Satellite Analysis Branch - NOAA/NESDISAFWA - U.S. Air Force Weather Agency

Legend : TAFB - Tropical Analysis Forecast Branch - NOAA/NCEPSAB - Satellite Analysis Branch - NOAA/NESDISAFWA - U.S. Air Force Weather Agency

Units in hPa Bias RMSE SampleODT +1.69 7.34 407Op. Center +4.31 10.35 407

Units in hPa Bias RMSE SampleTAFB +2.29 10.76 305ODT +1.58 7.46 305

SAB +4.88 10.42 319ODT +1.45 7.35 319

AFWA +5.55 12.06 146ODT +0.53 7.39 146

Developmental Data SampleDevelopmental Data Sample1995-19971995-1997

Units in hPa Bias RMSE SampleODT -0.72 7.97 397Op. Center -0.05 10.38 397

Units in hPa Bias RMSE SampleTAFB -1.25 10.65 341ODT -0.62 8.72 341

SAB +0.58 9.91 334ODT -0.53 8.75 334

AFWA +1.83 10.40 334ODT -0.43 8.07 334

Independent Data SampleIndependent Data Sample1998-19991998-1999

Super Typhoon Bilis (18W)Super Typhoon Bilis (18W)

• Good agreement with operational center and Best Track estimates– Slight overestimate during intensification and at peak– CI#s compare better with Best Track during weakening than Final T#s– Rapid weakening indicated by Final T#s supported by AMSU data (landfall)

– SAB ODT estimates differ from JTWC ODT during intensification

http://pzal.npmoc.navy.mil/jtwc_archive/2000/STORM_FOLDERS/NORTHWEST_PACIFIC/18W/Time_Intensity_Chart/18W_ti.gif://pzal.npmoc.navy.mil/jtwc_archive/2000/STORM_FOLDERS/NORTHWEST_PACIFIC/18W/Time_Intensity_Chart/18W_ti.gif

Super Typhoon Saomai (22W)Super Typhoon Saomai (22W)

• Good agreement with operational center and Best Track estimates– Underestimate during weakening with Final T#s (should use CI#s)– Initial estimates off due to very cold cloud top temperatures (~-80ºC)– SAB ODT analysis very similar to JTWC ODT analysis


Super Typhoon Shanshan (26W)Super Typhoon Shanshan (26W)

• Slight disagreement with operational center and Best Track estimates– Over/Underestimate during strengthening/weakening processes– CI#s compare better with Best Track during weakening than Final T#s– Rapid intensification cycles noted but led to ODT overestimates– SAB ODT analysis very similar to JTWC ODT analysis


Summary and ConclusionsSummary and Conclusions• 6 storm sample for 2000 West Pacific season6 storm sample for 2000 West Pacific season

– Overall, good comparison between JTWC and SAB ODT estimates

– JTWC and SAB ODT Final T# estimates were typically within 0.5 T# of JTWC Best Track estimates

– Very cold cloud temperatures led to high bias in Final T# relative to JTWC Best Track estimates (cloud temperatures < upper -70°C)

– Rapid intensification flag correctly identified events but led to large Final T# high bias when coupled with very cold cloud top temperatures (tuning to West Pacific needed)

• Slight differences between JTWC and SAB ODT estimatesSlight differences between JTWC and SAB ODT estimates

– Possible errors with ocean basin identification (basin flag is manually adjusted; could be automated)

– Implementation of 48 Hour Rule is slightly different between JTWC and SAB due to different ODT versions (fixed vs. time-weighted value)

• Overall, CI#s provided better fit to JTWC Best Track estimate than Final T#s during Overall, CI#s provided better fit to JTWC Best Track estimate than Final T#s during weakeningweakening

Future DirectionsFuture Directions• Operational ODT UsageOperational ODT Usage

– Full operational test at JTWC during 2001 with devoted analyst (patterned after SAB and TAFB evaluation)

– Experimental use only here at AFWA• Research FocusResearch Focus

– Further tune ODT for West Pacific based on JTWC and SAB 2000 results– Expand analysis range for tropical storms and weaker systems (will

remove need for 48 Hour Rule)– Investigate application of rapid intensification flag based on user analysis

and feedback– Begin development of Multispectral Dvorak Technique (MDT),

incorporating multiple satellite and channel information (AMSU, SSM/I, visible, water vapor, etc.)

Questions?Questions?AdvancedAdvanced

Objective Dvorak Objective Dvorak Technique (AODT)Technique (AODT)

AFWA/XOGMAFWA/XOGM

advanced objective dvorak technique (aodt) afwa/xogm

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