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Table of Contents

2. AERSURFACE

2.1. Introduction

In this section, we will cover AERSURFACE, a preprocessor for AERMET that assists in characterizing land surface parameters. It defines three key values:

  • Surface roughness length (Zo)
  • Albedo
  • Bowen ratio
Task Assist in obtaining values that characterize land use and land cover.
Input Data Land cover, impervious surface percentage, and canopy percentage in GeoTIFF format.
Output Data Surface roughness length (Zo), albedo, and Bowen ratio — to be used in AERMET.
Parameter Definition Usage
Surface Roughness (Zo) A measure of terrain roughness — how much resistance the surface offers to wind flow due to obstacles like vegetation, buildings, and topography. Defines the wind speed profile near the surface. Higher Zo generates more turbulence, which affects pollutant dispersion.
Albedo (Alb) The proportion of solar radiation reflected by the surface. Ranges from 0 (fully absorbed) to 1 (fully reflected). Affects soil heating and, consequently, convective turbulence (rising warm air bubbles).
Bowen Ratio (Bo) The ratio between sensible heat (air heating) and latent heat (evaporation). It indicates whether heat is transferred more into the air or into evaporation. Helps estimate surface heat flux, which is essential for calculating atmospheric stability (how well the air supports pollutant dispersion).

2.2. Download the Executable

First, download the AERSURFACE executable:

AERSURFACE - EPA SCRAM

Download the appropriate file for your operating system and save it to: ..\AermodTutorial\AERSURFACE\

In Figure 1 we can observe the download page.

Figure 1

Figure 1 – AERSURFACE download

Figure 1: Download the AERSURFACE executable according to its specifications in English.

2.3 Obtaining Surface Data

Go to: MRLC Viewer. Close the pop-up window as shown in Figure 2.

Figure 2

Figure 2 – MRLC Viewer

Figure 2: MRLC Viewer

Enable only the National Atlas States and ESRI World Imagery layers. See Figure 3.

Figure 3

Figure 3 – Selected map layers

Figure 3: Enabling relevant layers for download.

Use your mouse to pan and zoom to the USA, then locate the correct state. See Figure 4.

Figure 4

Figure 4 – Map zoom

Figure 4: Zoom into the region of interest.

Next, locate the point `-88.9520 40.4471` using the mouse coordinates. See Figure 5.

Figure 5

Figure 5 – Coordinate localization

Figure 5: Pinpointing the central point of the area.

Zoom in further as shown in Figure 6.

Figure 6

Figure 6 – Detailed zoom

Figure 6: Further zoom for selection accuracy.

Click the icon shown, and using the left mouse button, select your area of interest by clicking the two corner points. See Figure 7 and Figure 8.

Figure 7

Figure 7 – Area selection tool

Figure 7: Activate the selection tool.

Figure 8

Figure 8 – Selected region

Figure 8: Example of a selected urban and rural area.

Check the boxes exactly as shown, and set Select Years to 2023. See Figure 9.

Figure 9

Figure 9 – Data configuration

Figure 9: Configure the download options.

Enter your email and click download. See Figure 10.

Figure 10

Figure 10 – Email input

Figure 10: Enter your email to receive the download link.

Check your inbox for a message from `no-reply@usgs.gov` and click the download link. See Figure 11.

Figure 11

Figure 11 – Email with download link

Figure 11: Email with the download link.

Save the downloaded ZIP file to: `C:\Users\Cliente\Desktop\AermodTutorial\1.AERSURFACE` Then extract its contents.

2.4 Preparing AERSURFACE Inputs

Rename the `.tiff` file to `landcover.tiff`. See Figure 12.

Figure 12

Figure 12 – Rename file

Figure 12: Rename the TIFF to `landcover.tiff`.

Create a new text file named `AERSURFACE.txt`. See Figure 13.

Figure 13

Figure 13 – AERSURFACE input file

Figure 13: Example of input text file.

Below is an explanation of each command in the file:

  • `CO STARTING` – Begins the control block.
  • `TITLEONE`, `TITLETWO` – Custom titles for identification in output files.
  • `OPTIONS PRIMARY ZORAD` – Requests default outputs and directionally-resolved Zo.
  • `DEBUGOPT GRID TIFF` – Enables extra debug output (grid and TIFF info).
  • `CENTERLL 40.48 -88.99 NAD83` – Geographic center of analysis.
  • `DATAFILE NLCD2011 landcover.tiff` – Defines land cover classification and file.
  • `CLIMATE AVERAGE SNOW NONARID` – Local climate parameters.
  • `FREQ_SECT MONTHLY 2 NONAP` – Monthly values, 2 directional wind sectors.
  • `SECTOR 1 135.00 225.00` – Sector 1 definition (SE–SW).
  • `SECTOR 2 225.00 135.00` – Sector 2 definition (SW–N–SE).
  • `SEASON WINTERNS 1 11 12` – Late Autumn/Winter season.
  • `SEASON WINTER 2 3` – Winter with snow.
  • `SEASON SPRING 4 5 6` – Transitional Spring.
  • `SEASON SUMMER 7 8 9` – Midsummer.
  • `SEASON AUTUMN 10` – Autumn with unharvested crops.
  • `RUNORNOT RUN` – Executes the processing.
  • `CO FINISHED` – Ends the control block.
  • `OU STARTING` – Output file section.
  • `SFCCHAR BL_2023_Imp_Can.sfc` – Output file name.
  • `OU FINISHED` – Ends the output section.

2.5 Running AERSURFACE

Open the Command Prompt and navigate to the folder: `cd C:\Users\Cliente\Desktop\AermodTutorial\1.AERSURFACE` See Figure 14.

Figure 14

Figure 14 – Command Prompt

Figure 14: Open the terminal in the correct directory.

Then type the following to execute AERSURFACE: `aersurface aersurface.txt`

If successful, it should display output like in Figure 15.

Figure 15

Figure 15 – AERSURFACE output

Figure 15: Console output when execution completes.

5. AERSURFACE Output

Once complete, the `.sfc` file will be created — this contains the surface data. See Figure 16.

Figure 16

Figure 16 – Output .sfc file

Figure 16: Surface file created after successful execution.

The following lines are an example of a surface characteristics file used by AERMET. Each line provides monthly values of albedo, Bowen ratio, and surface roughness length for a specific wind direction sector.

Example: 

**           Month    Sect    Alb      Bo        Zo
   SITE_CHAR    1       1     0.18     0.95     0.317
   SITE_CHAR    1       2     0.18     0.95     0.346
   SITE_CHAR    2       1     0.46     0.49     0.250
   SITE_CHAR    2       2     0.46     0.49     0.273
   SITE_CHAR    3       1     0.46     0.49     0.250

Column Descriptions

Column Description
SITE_CHAR Keyword indicating the start of a surface characteristics entry.
Month Month of the year (1 = January, 2 = February, etc.).
Sect Wind direction sector number. Defined in AERMET configuration.
Alb Albedo — fraction of solar radiation reflected by the surface.
Bo Bowen Ratio — ratio of sensible heat flux to latent heat flux. Reflects surface moisture conditions.
Zo Roughness Length (in meters) — describes the aerodynamic roughness of the surface, affecting wind profile near the ground.

Example Interpretation

For the line: 

SITE_CHAR    1       1     0.18     0.95     0.317

This means:

  • Month: January
  • Sector: 1 (e.g., wind directions between 135° and 225°, if there are two sectors)
  • Albedo: 0.18
  • Bowen Ratio: 0.95
  • Roughness Length (Zo): 0.317 meters

These values are used by AERMET to compute atmospheric stability and turbulence based on the physical characteristics of the surface surrounding the meteorological station.

Save this file to the folder ``C:\Users\Cliente\Desktop\AermodTutorial\3.AERMET``: It will be used in AERMET's Stage 2 as a surface input.

Next Step

After finishing this step, you can continue to: AERMINUTE

aersurface.1746714200.txt.gz · Last modified: 2025/05/08 07:23 by murilogerber
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