Hindcasting using weather data

Introduction

ERF supports hindcasting simulations using weather data from ERA5 and GFS. There are automated Python tools that download and process the weather data, and writes out visualizable output as well as the initial and boundary condition files for running ERF simulations in a seamless manner. Currently there are examples for performing hurricane hindcasting using weather data.

Hurricane simulations

This folder contains examples for hurricane simulations from real weather data.

  1. Follow the steps in the erftools directory to generate the initial condition and boundary condition files.

    • For ERA5 data see the README section here.

    • For GFS data see the README section here.

  2. From the step above, copy the Output/ERA5Data_3D (Output/GFSData_3D for GFS) directory to the directory where ERF will be run. This is the boundary data for the lateral forcing of large-scale meteorology. Set the inputs option erf.hindcast_boundary_data_dir = ERA5Data_3D.

  3. The Python script also outputs the domain size to be used in the inputs file for the ERF run. For example:

    geometry.prob_lo  =  -2593434.0 -2065213.0 0.0
geometry.prob_hi  =   2593434.0  2328015.0 25000.0

  4. Copy the initial condition file to the ERF run directory. This can be the first file in the hindcast_boundary_data_dir. It can also be a file that was generated at the same time as the first file in hindcast_boundary_data_dir. For example, the initial condition can be from ERA5 data, but the boundary data can be from GFS data. However, the initial condition and the very first file in hindcast_boundary_data_dir should correspond to the same date and geographical area.

  5. Run ERF.

Inputs for hindcast simulations

The following are the inputs required for hindcast simulations.

// If using era5 or gfs data to initialize
// and for boundary forcing
erf.init_type = "hindcast"
// Initial condition filename -
// obtained from running the python script
// with the inputs file specifying the date and
// geographical area
erf.hindcast_IC_filename = "ERF_IC_2025_08_18_00_00_000.bin"

// Boundary conditions
geometry.is_periodic = 0 0 0
xlo.type = "Outflow"
xhi.type = "Outflow"
ylo.type = "Outflow"
yhi.type = "Outflow"
zlo.type = "SlipWall"
zhi.type = "SlipWall"

// Lateral forcing with reanalysis/forecast data
erf.hindcast_boundary_data_dir = "ERA5Data_3D"
// Time interval in hours between the boundary
// data files
erf.hindcast_data_interval_in_hrs = 3.0
erf.hindcast_lateral_forcing = true
// Sponge strength
erf.hindcast_lateral_sponge_strength = 0.3
// Sponge length of 144 km (for eg.)
erf.hindcast_lateral_sponge_length = 144000

// Sponge damping for top of domain
// to absorb reflections
erf.hindcast_zhi_sponge_damping = true
// Sponge strnegth
erf.hindcast_zhi_sponge_strength = 0.3
// Sponge length of 5 km
erf.hindcast_zhi_sponge_length = 5000.0

// Coriolis force
erf.use_coriolis = true
erf.coriolis_3d = true