Interactive Model Evaluation and Diagnostics System

 

V2.6 User Guide

September 1, 2009

 

 

Eve-Marie Devaliere, MS

University of North Carolina – Institute of Marine Sciences

US Army Corps of Engineers – Field Research Facility

 

Jeffrey L. Hanson, PhD

US Army Corps of Engineers - Field Research Facility

 

 

 

 


Table of Contents

 

I.          IMEDS Description_ 3

II.        IMEDS Requirements 4

III.       Starting IMEDS_ 5

IV.       Preprocess Data Module 6

1.1.  Model Data Pre-processors 8

1.2.  Observed Data Pre-processors 8

1.3.  Auto-Filling of the IMEDS Setup Form_ 9

V.        Evaluate Data Module 11

VI.       Display Module 17

1.     Overview of the IMEDS Display Module and Performance Sub-Module_ 19

1.1.  Stations Statistics Sub-Module_ 20

1.2.  Monthly Statistics Sub-Module_ 22

1.3.  Peak Analysis Performance Sub-Module_ 22

Appendix 1: Wavedat Format Description_ 25

Reference 26


 

             I.      IMEDS Description

The Interactive Model Evaluation and Diagnostics System (IMEDS) is a custom GUI-driven toolbox for MATLABTM to assess coastal process model performance using a variety of temporal and spatial metrics. A significant challenge in evaluating large temporal- or spatial-scale simulations is the need to statistically reduce millions of model estimates to a meaningful measure of prediction skill, yet retain sufficient level of detail to identify model strengths and deficiencies. This challenge is now met with IMEDS. IMEDS is fully functional with wind and wave data.  Water level data will be included in a future release.

IMEDS requires both an observation data set as ground truth, and a model or test data set to evaluate.  In addition to evaluating model data, IMEDS can be used to compare 2 observation stations or model runs together.  The user simply identifies one as being the ground truth data and the other one the test data.  The data are composed of time series output at specific geographic stations (i.e., NDBC buoys).  The observation data are decomposed into a series of components, such as wind-sea, young swell and mature swell for wave spectrum data.  These are further broken down into specific data attributes, such as the height, period and direction of each wave component.  More information on this particular technique can be found in Hanson et al. (2009). A variety of error metrics (such as root-mean-square error, bias, scatter index) are calculated for the model predictions at each station, by component and attribute. A performance score is then calculated from the errors. The performances are then folded through space and time giving the user an assessment of the total model performance for each attribute.  As a diagnostic tool the user can then explore model errors and performance as a function of many variables (station, time, components, etc).

The three statistical approaches available in IMEDS are Temporal Correlations (TC), Quantile-Quantile (QQ), and Peak Event (PE).  The results of these are folded into a Performance Score computation.  Each of these computations is briefly described below.

Temporal Correlation (TC) Analysis

The TC analysis is a direct comparison of time-paired data attributes. The TC analysis provides an indication of how well the hindcast quantities match the observed quantities in absolute time.  The following metrics are used to quantify the TC errors:

For non-directional data (speed, time, height and period) the error metrics are

 

  1. RMS error
  2. Bias
  3. Scatter index. 

 

For directional data the error metrics are 

 

  1. Circular correlation
  2. Circular bias

 

Quantile-Quantile (QQ) Analysis

The QQ analysis provides information on how the distribution of data attributes compare between observation and model results.  Quantile-Quantile distributions computed for both data sets (observed and modeled) are statistically compared to compute a set non-directional error metrics (see list above).

 

Peak Event (PE) Analysis

The PE analysis extends the IMEDS capability by isolating and computing statistics on event peak data.  User-provided thresholds (constants or Standard Deviation multipliers) are used to identify event peaks in wind and wave records.  A standard up-crossing analysis is used to isolate time series segments that contain relevant data. Corresponding peaks are identified in the test data using a user-provided time search threshold.  Only the bulk (full-spectrum) statistics are used for this analysis.  The attributes extracted from each peak event form data pairs that are then used to compute the standard non-directional error metrics (see list above).

 

            Performance Scores

This above analyses result in a set of error metrics that quantify the hindcast skill in reproducing the physical attributes at each observation station.  For a 1-year wave study with 6 stations this can result in a database of 3,500 independent measures of model skill for each hindcast run.  A performance scoring method was developed to reduce the error metric database into a small set of performance indicators for overall skill assessment.  Performance scores are computed by normalizing the wave component metrics to mean quantities and averaging them across metrics, months and stations with contributions weighted by sample size.  The resulting non-dimensional performance scores range from 0 (uncorrelated) to 1 (perfect correlation) and relate to the fraction of the mean that is not impacted by error.  So a performance score of 0.8 can be interpreted that error levels are within approximately (1-0.8)*100 = 20% of the attribute means.

 


          II.      IMEDS Requirements

            In order to run IMEDS successfully a few conventions have to be used. Those are listed below:

  • Models (or test) and observation data has to be in a ‘wavedat’ format. For a description of this format, please see Appendix 1. Since IMEDS v2.2 you can use a data preprocessing module if your data is not in wavedat format. Please see the IMEDS pre-processor section.
  • The wavedat file has to hold one month or less of data. If validation is needed over a longer period of time, the data needs to be broken up into monthly files.
  • Filename conventions:
    • The station ID (as the user wants it to appear in the plots) needs to be in the filename for both ground-truth and test data. This is how IMEDS knows which files to pair up. The user has 2 choices to organize the data:
      • Group it in folders holding the station ID with the station ID figuring anywhere in the filenames.
      • Not organize it in folders but have the station ID as the beginning of the filename up to the underscore.
    • If the run spans many months the model and observation files need to specify the month and year in the filename using 3 letter or 2 digits month and 4 digit year as in 41025_NDBC_Jun2000.mat. (the order of the code, month and year doesn’t matter as long as they are all included in the filename)
    • As of version 2.6, only one file with the station code can be in the directory that iMEDs is looking in for single month runs.

·        If the user is using the preprocessors to format the data, the filename convention will be taken care of. However, other conventions need to be followed for the use of the preprocessors. Please refer to the preprocessors section for further information.

  • Reserved Words: Certain words are not supported by MATLABTM because they conflicting with MATLABTM commands. Do not use the followings in any edit field:

o       default

 

 

 

        III.      Starting IMEDS

  • Using your directory browser, set the current directory to /imedsRoot/IMEDS/src where imedsRoot is the path to the directory IMEDS has been placed in.
  • Double-click on imeds.exe to open the imeds Module Selection Window (Figure 1)
  • Select between the 3 IMEDS modules

o       Preprocess Data: Format data.  If the data is not in wavedat format, a finite set of preprocessors are available for formatting the user's data.

o       Evaluate Data: Initiate the IMEDS run set up process with the ‘Run Setup’ window. Once the IMEDS run is completed it automatically starts the results display.

o       Display Results: View results from previously analyzed data

 

Figure 1: IMEDS Module Selection Window

 

Each of these modules is described below.


      IV.      Preprocess Data Module

The preprocessor module shown in Figure 2 allows one to pre-process both model and/or observed data. If one doesn’t want to process both model and observed data at the same time (e.g. second run of a model, the observed data would have been already processed) one can skip the selection of the directory for the given data. In this case one has to be careful to select which event this run is related to in the event pull-down menu so that the observed data can be retrieved accordingly (details follow).

When browsing to the model or observed data, IMEDS pre-processor automatically points to /imedsRoot/IMEDS/data/raw. It is suggested that the user put the raw data in sub-directories of this one, but one could browse anywhere.

Each observed data is associated to an event (e.g. Isabel, year 2007…). The observed data produced by the preprocessor will be in: /imedsRoot/IMEDS/data/obs/event_name/ (if the event and run name contains spaces they will be replaced by underscore to avoid bugs on Linux systems ; imedsRoot is the directory in which IMEDS has been unzipped to)

Each model data set is associated to an event and a run (model run) since a model can be run many times with different settings for the same event. The data produced by the preprocessor will be in (The space rule mentioned above is also valid here for event and run names): /imedsRoot/IMEDS/data/obs/event_name/run_name

Instructions for specific Preprocessor inputs follows.

  • Single Event Checkbox

If the raw data covers many months, the formatters will automatically split the data into monthly files. However, it may be that the user doesn’t want monthly statistics (e.g.: the studied hurricane event is occurring at the end of a month, trailing into the other month). In this case, the user can force the preprocessors to handle the multi-month event into a single month event, by checking the ‘Single Event’ checkbox.

  • Add to Existing Run Checkbox

In some cases, one will need to either reprocess data and/or add some data to an already setup run. Alternatively, the user might not want IMEDS to set up the directory structure as previously stated. Either way, the ‘Add to Existing Run’ checkbox allows the user to specify the directory where he wishes the pre-processed data to be stored at. 

  • Organized by Station Checkbox

If ‘Organized by Station’ is checked that means the files (model or observed) are organized by folders whose name is the station name inside the root directory that the user selected. If it is not checked the program would be looking for the data files in the root directory selected by the user.

 

  • Time-Zone Pull-Down Menu

The user needs to specify which time-zone the results are in so that IMEDS can correctly match the observed data and model results.

  • Smooth Data Checkbox

For observed data, the user can also choose to smooth the data by checking the ‘Smooth data’ checkbox and entering the number of hours he or she desires the data to be smoothed over in the ‘Smoothing Interval’ edit area. . This data will be saved smoothed. If the user chooses to try different smoothing values, it would be advised not to smooth the data here but use the smoothing option in the Run Setup. This later option will not affect the data saved on the drive, but only the data used in a particular run.

 

 

Figure 2: IMEDS Pre-Processor

 

 

1.1.        Model Data Pre-processors

WAVEWATCH III (WW3) Formatter

  • As of release 2.6, one unique WW3 formatter handling single month/station and multi months/station exists.
  • The only filename convention is that the filename is a ‘*spc’ file.
  • The station name is obtained from the file. The station name will be 46042 if the header looks like: '224  46042'  37.00 237.50     988.6  10.73 318.1   0.00 270.0  or '46042    '  37.00 237.50     988.6  10.73 318.1   0.00 270.0.
  • If your header line looks any different, you may encounter problem. Please let us know if that’s the case.
  • The data can be organized by stations or all the stations can be in the same folders

SWAN Formatter

·        The SWAN formatter works on single station SWAN output. It needs both the TAB and spectra files.

·        If the files are organized by folder, the formatter gets the station name from the folder name. If they are not, it will get the station name from the TAB file, up to the underscore. (e.g. 45032 will be the station name from the file 45032_TAB)

·        The station name also needs to be included in the spectra file as in spec2d.out.45032.

·        Each station file can have as many records as desired. IMEDS will take care of dividing it into monthly files if necessary.

Oceanweather Formatter

  • This formatter is developed for Oceanweather, Inc formatted wave spectra files.
  • The data can be organized by stations or all the stations can be in the same folders
  • The filename convention is buoyName.asc (as in 47012.asc). This can be modified if necessary.
  • Each station file can have as many records as desired. IMEDS will take care of dividing it into monthly files if necessary.

 

1.2.        Observed Data Pre-processors

CHL NDBC Formatters (spe1D or spe2e and onln)

  • This is a custom format used by USACE-CHL.
  • The IMEDS preprocessor selects the NDBC processor to use depending on the extension of the spectra file (spe1D or spe2D). If the files are organized by station the preprocessor is called once for all the files in the directory. If not it is called file by file since it has to pick which processor to use for each file.
  • It will give an error if a spectra file can’t be found.
  • As for the WW3 formatter if the data is organized by directory the station name (which needs to be the same than for the model data) is assumed to be the name of the directory. If not, it will take the 2nd character of the filename up to the first underscore. (e.g. for n46041_2000_11.onln, 46041 is the station name)

NODC formatter

·        This formatter operates on wind and wave spectra from the standard NODC File Type 291.  NODC data can be downloaded at http://www.nodc.noaa.gov/BUOY/buoy.html

·        Data can be organized by station folders or not. As for the other formatters if the data is organized by folder, the station name is assumed to be the folder name. If it is not, we use NODC conventions as in 44009_200902 with stationName_YearMonth used to identify the station name and dates. The year and month will be used as described above in both cases.

·        The data needs to be unzipped before running the preprocessor as MATLABTM unzip function doesn’t support the .Z extension used by NODC.

·        Since NODC files don’t have any extension, IMEDS will consider each file found in the specified directory to be a valid NODC format.

1.3.        Auto-Filling of the IMEDS Setup Form

  • Once the pre-processor is done preprocessing the input data (and if no problem was encountered) the IMEDS setup GUI is launched and auto-filled with the information from the preprocessor.
  • If one only decides to preprocess model data, the observed data directory in the IMEDS setup would be automatically selected as being  /imedsRoot/IMEDS/data/obs/event_name/. A warning is displayed to tell the user that this information needs to be checked.
  • If one only decides to preprocess observed data, the model data directory would be automatically selected as being: /imedsRoot/IMEDS/data/obs/event_name/run_name if the run name has been specified. A warning will also be displayed. If the run name has not been specified in the preprocessor, the user will have to browse to the model data directory in the IMEDS setup screen.
  • In both above cases the ‘Organized by station’ is checked by default since it seems to be the most likely.
  • The output directory is automatically selected as being

/imedsRoot/IMEDS/data/processed/event_name/run_name but the user can browse to another directory if he desires. Again if the run name hasn't been specified the user will have to browse to the output data directory in the IMEDS setup screen. This directory will then be created while IMEDS is running. If the user tries to change this directory name, the browsing will take him or her to an upper level directory since the directory would not exist yet.

·        For wave models the wave data type is automatically selected.

·        The analysis types TC and QQ are selected by default and no output (display or save) is selected. 

·        The stations list is automatically populated.

 

All those settings can be modified at the user discretion.

 


         V.      Evaluate Data Module

The Run Setup Window, depicted in Figure 3, allows the user to setup all necessary information for IMEDS to process both observed and modeled data. Below is a description of each feature available in the Run Setup Window.

 

  • Preset Event and Preset Run

User-defined run setups can be saved for future use. In order to simplify the access of a run, different runs are associated with an event. The user can thus run different versions (runs) of Katrina (the event). Selecting a given event in the Preset Event would give the user a list of associated runs in the Preset Run pull-down menu. If this is a new event and/or a new run, both pull-down menus have an ‘Enter New…’ option that will guide the user into entering a new event and run name if chosen from the Preset Event pull down menu or a new run only if chosen from the Preset Run pull-down menu. Figure 4 shows the popup window the user needs to fill when choosing a new event.

If the user selects a preset event and a preset run then the form is filled in automatically.

 

  • Test Directory, Ground Truth Directory and Output Directory

This is where IMEDS looks for the test (model) data, ground truth data and where to output the results. The user can type the name of the required directories or browse to them by clicking the Browse buttons. The Organized by Station checkbox needs to be selected if the data is organized by station. In this case the folder name needs to be the station code. (E.g.: It needs to be checked if the model data file is /imedsRoot/IMEDS/data/mod/myTest/41025/41025_SWAN.mat and unchecked if it is /imedsRoot/IMEDS/data/mod/myTest/41025_SWAN.mat (/imedsRoot/IMEDS/data/mod/myTest/ being the Test Directory entry))

 

  • Test Name

This can be a model name (e.g.: SWAN) or a test name. It needs to be what was referred to as test in the IMEDS requirements paragraph. If the name the user is looking for is not in the list, one can be entered by selecting 'Enter New'. The user would then be guided into entering a test name.

 

  • Multi-Months Selection

A basic IMEDS run is based on a monthly file. However, the IMEDS run can be performed over more than one month of data. If the user chooses to do so, the time selection check box needs to be checked and the time span of the run declared using the pull down menus and edit boxes situated below the time selection check box.

Figure 3: IMEDS Run Setup Window

 

Figure 4: IMEDS New Event Entry Form

  • Data Selection

The user has the choice between wind, wave and water-level analysis. Wind and Wave can be done at the same time as long as both data type are included in the wavedat file.

Select types of analysis desired:   Quantile-Quantile (QQ) or Peak Analysis (PK). Temporal Correlation (TC) is executed by default. If PK is selected, the Peak Analysis setup window will pop up.

 

As of version 2.6, two types of Peak Analysis are possible using a fixed elevation or using standard deviation. The peak event analysis will occur for each data type selected in the Data Selection area in the run setup window. The other ones will be grayed out.

As shown in Figure 5, if the user select the fixed elevation methodology, thresholds have to be entered in terms of wave height, wind speed and/or water-level amplitude. 

If the standard deviation is chosen, the user needs to specify the number of standard deviation above the mean for each data type. An example is shown in Figure 6.

Whichever methodology is used a delta T in hours needs to be specified for any given data type. If 6 hours is selected the peak analysis will look for the model peak 6 hours behind and ahead of the observed peak.

 

Figure 5: IMEDS Peak Event Setup for Fixed Elevation for all data types

 

 

 

Figure 6: IMEDS Peak Event Setup for Standard Deviation for Wave Only

 

  • Subset Month
    • If a single-month run is being setup, this section would subset the monthly file from starting day and hour to ending day and hour. The user is warned if the time-range specified is out of the file time-range. Model outputs have usually larger time-steps than observed data. If a user requests a subset from the 5th at 7 am to the 15th at 8am and the output is every 6 hours (00,06,12 and 18) the file would be subset from the 5th at 12 am to the 15th at 6am. One thus needs to be careful by requesting a subset large enough to include both modeled (or tested) and observed data. The time-zone used here is the time-zone selected for the output.
    • If a multi-month run is being setup, the first month will be subset from the starting day and time to the end of the month and the last month will be subset from the beginning of the month to the ending day and time. The same rules as the single month subset apply here.

 

  • Output Selection

After IMEDS is done running the display module opens and all plots, graphs and tables are then available to the user. However, the user has 2 options concerning the output while IMEDS is running.

o       Display Output: the figures produced by IMEDS will be visible and pop up to the screen while IMEDS is running.

o       Save Output as *.png: The figures are save as a *.png file while IMEDS is running. (This is particularly useful if the user intends to use all or most of the figures into a presentation) .The user has the possibility to choose what type of output he wants to be save. The error plots and tables are associated to each station statistics and performances, while the performances tables and graphs are associated to the summary of the model run (when the stations statistics are folded up).

 

  • Time-Zone

This is the time-zone the results are going to be displayed in. Once the wavedat files are loaded in IMEDS, the data is switched to this time-zone for the processing and results display.

 

  • Station Selection

The user needs to specify which stations the IMEDS run need to consider. This is done in the Station Selection part of the IMEDS Run Setup GUI.

Four parameters common to all stations for a given run need to be specified.

    • Min Wave Height: the minimum height a wave partition needs to be to be considered in the performance calculations. Default to 0.3 m.
    • Max Partition: The maximum number of partitions to consider at a given point in space and time. Default to 4.
    • Min total records: The minimum number of observed records to be available for IMEDS to do any processing. If a file has a number of records below this threshold IMEDS would behave as if this file does not exist. Default to 25.
    • Min components records: The minimum number of record for a component to be included in some statistics and any performance calculations. A data set needs to have at least this number of wind-sea for example for the wind-sea performances to be calculated. This number thus corresponds on the number of matching records between observed and tested data. (generally less than the number of observed records). Residuals, scatters and bias are still calculated if the number of components records fall below this threshold. Default to 15.

 

  • Populate Station List

At the push of this button, the stations list is populated from files IMEDS could find in the observation and tests directories. For more information on how IMEDS finds those station IDs, please refer to the IMEDS Requirements section at the beginning of the User Guide. If the user chooses to do so, a run can be done over a subset of those stations. One needs to select the station he doesn’t want to process from the station list and push the ‘Delete Station’ push button.

 

·        Tools Menu

Three options are available from the ‘Tool Menu’:

o       Delete Event/Runs

This option will open the ‘Events/Runs Manager’ as shown in Figure 7. This allows this user to clear some of his old events/runs. This will delete events and/or runs from the Run Setup GUI lists but won’t delete any processed data associated to a particular run.

If a run is selected in the ‘Associated Runs’ list, hitting the ‘Delete’ button will remove this run.

In order to remove all the runs from a particular event, a faster option is to select the event itself from the ‘Events’ list and hit ‘Delete All’.

The ‘Help’ button gives a reminder on how to use this Events/Runs Manager.

The ‘Exit’ button closes the window.

 

Figure 7: IMEDS Events/Runs Manager GUI

 

o       Waitbar

Waitbars are automatically turned on during IMEDS processing. The user can turn them off by checking this option off in the Tools menu.

o       Smooth

This option enables data smoothing for the observed dataset over a specific interval. The Smoothing Setup’ window, shown in Figure 8, pops up when selecting thee ‘Smooth’ option. The user can then enter the smoothing interval in hours that he wishes for. The smoothed data will be used for the run but won’t be saved on the hard drive. The user can thus try different smoothing values without preprocessing his data again. This can be particularly useful for the Peak Analysis.

 

Figure 8 : Smoothing Setup Window

 

·        Save Setup Button

This button allows the user to save the particular setup without running IMEDS

 

·        Run IMEDS Button

Run IMEDS Button first asks the user if he wishes to save the setup and then run IMEDS. Once IMEDS is done running the Display Module will get launched.

 

·        Reset Form

The Reset Form button resets the Run Setup form as it was found when starting the GUI

 

·        Cancel Button

This closes IMEDS.

 

·        Help Button

This button opens the help document

      VI.      Display Module

The Display Module opens once an IMEDS run is over or can be called directly from the Module Selection Window for a previous run. When it opens, it automatically opens the performance module for all the stations and month (if more than one month was selected) for each wave component. The Display Module is interactive and greys out options that are not available in particular circumstances (e.g. No direction data for 1D buoys). It also warns the user if any data is missing (e.g.: some buoys are out of service over several months in the course of a year) or if some statistics haven’t been computed because of too few data points. Temporal correlation, quantile-quantile Analysis, and peak analysis are available from the Display Module , as long as they have been included in the analysis. The displays for temporal correlation and quantile-quantile analysis are very similar and described in the three following sections. The peak analysis display is slightly different and is presented separately.

 


1.  Overview of the IMEDS Display Module and Performance Sub-Module

Figure 9 illustrates the options available in the Display Module and some options from the Performance Sub-Module.

The features are listed from top to bottom and left to right.

 

 

Figure 9: Display Module and Performances Sub-Module Features

 

·        Toolbar

The toolbar options allow the user to explore the data in more depth by (in order) zooming in, zooming out, pan, obtain the data for a particular point (graphs only), print and save.

·        Analysis Push Buttons (Temporal Correlation, Quantile-Quantile Analysis, Peak Event Analysis)

These push buttons switch between the different analysis types.  If a display type is chosen that is not available in one particular analysis type, the user will be automatically redirected to the performance or statistics table. A message will alert the user if this happens.

·        Module Options

This radio-button group selects one of the different IMEDS display modules: global performance scores, statistics grouped by stations or by months. The global performance scores is selected in Figure 9.

·        Display Options

This radio-button group changes the IMEDS display type. In the performance module, the user can review summarized performances in a table or in a bar graph.

·        Data Options

In the performance module, the user can select to view performances grouped by stations or by components (wind-sea, swells..)

·        Map

The map button, in the lower-left corner, represented by a globe, plots a map of the different stations used in the given run.

·        Help

The help button opens the wave display help.

·        Cancel

Cancel closes the wave display window.

·        Go

Once the selection of the different options in the right hand-side of the Display Module is done, hitting the Go button displays the results.

 

1.1.        Stations Statistics Sub-Module

The Stations Statistics sub-module gets deeper into the IMEDS results and gives information related to each station for each given month.  Figure 10 illustrates the features available in the Stations Statistics Sub-Module.  As previously, the features are described from top to bottom. Only the ones that differ from the Performance Sub-Module are stated.

 

 

 

Figure 10: Stations Statistics Sub-Module Features

 

·  Station and Month Selections

The user can select the station and the month he wants the statistics for using the stations and month pull-down menus. The left and write arrows make it easier to navigate through stations and months once a particular display type is chosen (no need to push ‘Go’). For a multi-month run, an extra check-box ‘All Months’ (below the months selection) is available in the Stations Statistics Sub-Module for a given station statistics for all months.

 

·  Display Options

The user can review statistics in a table, a residual graph, a scatter plot or time-series for TC analysis, and a table or QQ plot for QQ analysis. Residuals, scatters and time-series can also be plotted for all months if the ‘All Months’ check box is selected.

 

·  Components Selection

In the Stations Statistics module, for all display types but the table, the graphs can be plotted using the full spectrum information of the different wave components.

 

·  Attributes Selection

The wave attribute can be selected using radio buttons.

 

1.2.        Monthly Statistics Sub-Module

The Monthly Statistics Sub-Module is only available for a multi-month run. The features of the Monthly Statistics Sub-Module are presented in Figure 11.  The stations list on the right-hand side allows the user to choose which stations and which wave attribute he wants to plot. It then plots time series of the bias, RMS Error, Scatter Index and Performances for each selected station for the full spectrum and each wave component.

 

1.3.        Peak Analysis Performance Sub-Module

When selecting the Peak Event Analysis, the Peak Summary is automatically loaded. This summary, shown in Figure 12, includes a scatter plot with the peaks color and symbol coded by stations. Many peaks through the course of a month or many months are plotted with the same symbol and color. A peak statistics table is also included in this summary. The table gives the bias, RMS error, scatter index and performance score for the overall peak analysis. The summary can be obtained for any wave attribute, using the ‘Attributes’ radio-button group.  The time-series for each station and month, illustrating the different peaks used for the analysis can be obtained by selecting the ‘Station Peaks’ radio-button. Similarly to the Peak Summary, each wave attribute can be selected. Note that the threshold line would only appear for the wave height. An example can be seen in Figure 13.

 

Figure 11: Monthly Statistics Display



Figure 12: Peak Analysis Summary Display

 

Figure 13 : Peak Analysis Station Peaks Display
Appendix 1: Wavedat Format Description

 

Data processed by IMEDS are stored in special structure called wavedat.   The various preprocessors modify the given raw format (e.g.: WW3 or NDBC) into this wavedat format.  A summary of the required wavedat input fields follows:

 

·        file: (string) Processing History

·        time: [1x m double] Observation Date and Time

·        espt: {1x m cell} Directional Wave Spectra (m2/(hz x deg)

·        dwfhz: [1x64 double] Frequency Bins (Hz)

·        dwdeg: [1x24 double] Angle Bins (deg)

·        dwAvv: {1x m cell} 1D Energy-Frequency Spectga

·        hs: [1x m double]  Significant Wave Height (m)

·        fp: [1x m double]  Peak Frequency (Hz)

·        thetap: [1x m double] Peak Direction (Hz)

·        winddir: [1x m double] Wind Direction (Deg From True North)

·        windspeed: [1x m double] Wind Speed (m/s)

·        name: (string) Data Set Name

·        size: [1x1] Number of Records

·        type: '2D' or 1D, Specifies Directional or Non-Directional Data

·        lat: [1x1] Latitude (decimal degrees +N/-S)

·        lon: [1x1] Longitude (decimal degrees +E/-W)

·        depth: [1x1] Water Depth (m)

 

       

 Partitioning the data stored in wavedat (automatically done by IMEDS while running) adds an ‘out’ field. The fields in wavedat.out contain information on the individual wave components (spectral partitions):

 

·         time: [1x m double] Date and Time

·        rms: [1x m double]  RMS Wave Height (m)

·        azimuth: [1x m double] Mean Direction (Deg from True North)

·        freq: [1x m double] Peak Frequency (Hz)

·        grp: [1x m double]  Wave System Number

·        sys: [1x m double]  Swell Event Number

·        totnrg: [1x m double] Total Energy (m2)

·        sighight: [1x m double]  Significant Wave Height (m)

·        dirspread: [1x m  double] Directional Spread          

·        par: [1x m double] Partition Number

·        wforce: [1x m double] Wave Force Ratio

 


Reference

 

Hanson, J.L., B. Tracy, H. Tolman and R. Scott, 2009. Pacific hindcast performance of three numerical wave models, J. Atmos. Oceanic Technol., 26, pp. 1614-1633.