Harvard Forest

Data Archive

HF447

EXPOS Model for Estimating Topographic Exposure to Wind (R and Python)

Related Publications

Data

• HF447-01: source code in R and Python v. 1.1

Overview

• Lead: Emery Boose
• Investigators:
• Contact: Information Manager
• Start date:
• End date:
• Status: complete
• Location: Global
• Latitude: -90 to +90 degrees
• Longitude: -180 to +180 degrees
• Elevation:
• Datum: WGS84
• Taxa:
• Release date: 2024
• Language: English
• EML file: knb-lter-hfr.447.1
• DOI: digital object identifier
• EDI: data package
• DataONE: data package
• Related links:
• EXPOS Model for Estimating Topographic Exposure to Wind
• Modeling Impacts of Hurricanes on Current Aboveground Forest Carbon in New England 2020-2120
• Study type: modeling
• Research topic: ecological informatics and modelling
• LTER core area: disturbance patterns
• Keywords: geographic information systems, hurricane damage, meteorology, models, region, wind
• Abstract:

  The EXPOS model uses a digital elevation model (DEM) to estimate exposed and protected areas for a given hurricane wind direction and inflection angle. The resulting topograhic exposure maps can be combined with output from the HURRECON model to estimate hurricane wind damage across a region. EXPOS is available in R and Python. The R version is available on CRAN as ExposR. The model is an updated version of the original EXPOS model written in Borland Pascal for use with Idrisi (see HF024). For more details and sample datasets, see the project website on GitHub (https://github.com/expos-model).

• Methods:

  Getting Started

  Here are the basic steps for using the model: (1) Create a directory for a particular study area with subdirectories as described below. (2) Copy the digital elevation file to the dem subdirectory and rename it "dem.tif". (3) Download or create geographic and political boundary shapefiles for the desired study area. Copy these files to the vector subdirectory and rename so the first name of each file is "boundaries". (4) Use the expos_model function to create exposure maps for different wind directions and inflection angles. (5) Use the expos_damage function to create maps of enhanced Fujita scale wind damage for particular hurricanes.

  Details

  All user functions begin with "expos". The wind direction and inflection angle must be specified in degrees.

  The user specifies a directory (exp_path) for a given study area. Input and output files are stored on the following subdirectories of this directory: exp_path/dem, exp_path/exposure, exp_path/damage, exp_path/vector.

  The dem subdirectory contains the input elevation file. The exposure subdirectory contains output files from the expos_model function. The damage subdirectory contains input files from the HURRECON model, the reprojection file, and output files from the expos_damage function. Shapefiles that contain geographic and political boundaries for viewing results are stored on the vector subdirectory.

  Model Functions

  The expos_model function estimates topographic exposure for a specified wind direction and inflection angle. The input file is assumed to be a raster of elevation values in GeoTiff format with missing values represented by zero. Cells may be rectangular. The user can specify if coordinates are lat/long; otherwise lat/long is assumed if X values are between -180 and 180 and Y values are between -90 and 90. If coordinates are lat/long, horizontal and vertical units are assumed to be degrees and meters, respectively; otherwise horizontal and vertical units must be the same. Columns are assumed to be closely aligned with true North (0 degrees); if not, the map orientation (azimuth) must be specified in degrees. The name of the input file is assumed to be "dem.tif". The output file is a raster file in GeoTiff format with the following values: 0 = missing data, 1 = protected, 2 = exposed. Output files are named "expos-xxx-yy.tif" where xxx is the wind direction and yy is the inflection angle. In previous studies, spatial resolutions of 30 or 60 meters and an inflection angle of 6 degrees were found to work well. Note that increasing the inflection angle tends to decrease the size and number of protected areas while increasing the odds that these sites are protected.

  The expos_damage function estimates regional hurricane damage where topographic exposure at each location is determined by peak wind direction. If a location is protected, the enhanced Fujita scale (EF) rating from HURRECON is reduced by a specified number of EF ratings. This function requires a hurricane GeoTiff file created by HURRECON, exposure files created by EXPOS for the eight cardinal wind directions (N, NE, E, etc), and a reprojection file in CSV format (reproject.csv) that contains lat/long coordinates for the lower left and upper right corners of the digital elevation model (variables: name, lat_0, lon_0, lat_1, lon_1). The output file is a raster file in GeoTiff format with the following values: 0 = missing, 1 = no damage, 2 = EF0 damage, 3 = EF1 damage, 4 = EF2 damage, 5 = EF3 damage, 6 = EF4 damage, 7 = EF5 damage. Output files are named "hhhh-damage-yy-z.tif" where hhhh is the hurricane ID, yy is the inflection angle, and z is the reduction in EF rating for protected areas. Note: for large areas, best results will be obtained by converting the DEM to latitude/longitude coordinates (if necessary) before running expos_model and expos_damage and then converting the resulting damage maps to the desired map projection.

  The expos_set_path function sets the path for the current set of model runs. The expos_get_path function returns the current path. Use expos_set_path before using other functions.

  The expos_summarize function displays summary information for a specified raster file, including the number of rows and columns, spatial extent, cell height and width, and minimum and maximum value.

  The expos_plot function creates a plot of a specified raster file.

• Organization: Harvard Forest. 324 North Main Street, Petersham, MA 01366, USA. Phone (978) 724-3302. Fax (978) 724-3595.

• Project: The Harvard Forest Long-Term Ecological Research (LTER) program examines ecological dynamics in the New England region resulting from natural disturbances, environmental change, and human impacts. (ROR).

• Funding: National Science Foundation LTER grants: DEB-8811764, DEB-9411975, DEB-0080592, DEB-0620443, DEB-1237491, DEB-1832210.

• Use: This dataset is released to the public under Creative Commons CC0 1.0 (No Rights Reserved). Please keep the dataset creators informed of any plans to use the dataset. Consultation with the original investigators is strongly encouraged. Publications and data products that make use of the dataset should include proper acknowledgement.

• License: Creative Commons Zero v1.0 Universal (CC0-1.0)

• Citation: Boose E. 2024. EXPOS Model for Estimating Topographic Exposure to Wind (R and Python). Harvard Forest Data Archive: HF447 (v.1). Environmental Data Initiative: https://doi.org/10.6073/pasta/0db4cfa6b825866723074553d72fc003.

Detailed Metadata

HF447-01: source code in R and Python v. 1.1

• Compression: zip
• Format: R and Python scripts
• Type: model