Noah-MP (Fortran) – Research Version

This repository contains a Fortran-based implementation of the Noah-MP Land Surface Model (LSM) used in the following studies:

• ESS Open Archive Preprint: https://essopenarchive.org/doi/full/10.22541/essoar.172286649.90332939/v1
• Hydrology and Earth System Sciences (HESS, 2025): https://hess.copernicus.org/articles/29/547/2025/

This version represents a research-oriented modification of Noah-MP, developed to improve the representation of key hydrological processes, particularly in soil moisture dynamics, runoff generation, and subsurface flow.

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🔬 Key Model Developments

Compared to the standard Noah-MP implementation (e.g., NCAR version), this repository includes several important enhancements:

1. Mixed-Form Richards Equation Solver

• Implements a mixed-form solution of Richards equation for soil moisture dynamics
• Improves numerical stability and physical consistency
• Enhances representation of unsaturated flow and soil moisture redistribution

2. Van Genuchten (VG) Parameterization

• Uses Van Genuchten soil hydraulic functions for:
  • Soil water retention
  • Hydraulic conductivity
• Provides a more physically realistic description of soil hydraulic processes
• Note: availability of VG parameterization may differ across Noah-MP versions; this implementation ensures consistent use within the solver framework.

3. Surface Ponding Representation

• Introduces explicit surface ponding storage
• Allows accumulation of water when infiltration capacity is exceeded
• Improves simulation of:
  • Saturation-excess runoff
  • Surface water dynamics

4. Macropore / Preferential Flow

• Includes representation of macropore flow pathways
• Enables rapid vertical transport beyond matrix flow assumptions
• Improves representation of:
  • Infiltration-excess runoff
  • Deep percolation and groundwater recharge

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⚖️ Comparison with Standard Noah-MP (NCAR)

Feature	NCAR Noah-MP (typical)	This Version
Richards Solver	Pressure-head / simplified	Mixed-form solver
Soil Hydraulics	Lookup / simplified	Van Genuchten formulation
Ponding	Limited / implicit	Explicit ponding storage
Preferential Flow	Not explicitly represented	Macropore flow included
Hydrologic Focus	General LSM	Enhanced process-based hydrology

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📁 Repository Structure

Noah_code/

Core Noah LSM source code:

• module_Noahlsm.F
• module_Noahlsm_param_init.F
• module_date_utilities.F
• module_Noahlsm_utility.F

IO_code/

Input/output handling modules:

• module_Noah_NC_output.F
• module_Noahlsm_gridded_input.F
• Noahlsm_driver.F – main model driver

Run/

Execution configuration:

• Noah_offline.namelist – model configuration file
• Compiled executable (./Noah) is generated here

Noah_data/

forcings/

• Forcing data reprocessed from GLDAS (NetCDF format)

results/

Simulation outputs:

• exp1/hrly/ – hourly outputs (e.g., runoff)
• exp1/hist/ – monthly mean outputs
• exp1/ini/ – end-of-year states

static/

Static input datasets (1° resolution):

• gvf.nc – vegetation fraction
• landmask.nc – land-sea mask
• plotmask.nc – grid mapping
• tbot.nc – deep soil temperature (~8 m)
• lon_lat.nc – grid coordinates
• soilcolor.nc – soil color index (1–8)
• veg_soil.nc – vegetation type & soil texture index
• rawdata/ – higher/lower resolution source datasets

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⚙️ How to Run

1. Compile the Model

make

If compilation fails:

• Modify the Makefile for your system

• Ensure required compilers and libraries are available

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2. Configure

Edit the namelist file:

Run/Noah_offline.namelist

Update settings such as:

• Simulation period

• Input/output paths

• Physics options

• Experiment configuration

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3. Run

From the Run/ directory:

./Noah

4. Output

Simulation results will be written to:

`Noah_data/results/`

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Requirements

This model is intended for use in a Unix/Linux environment and typically requires:

• A Fortran compiler (e.g., gfortran or ifort)

• Standard build tools such as make

• NetCDF libraries (if enabled in the build and I/O configuration)

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Notes

• This repository is a research archive and may differ from official Noah-MP releases, including the NCAR version.

• The modifications in this repository were developed for process-based hydrological investigations and scientific analysis, rather than operational forecasting.

• Users should carefully review the model structure, assumptions, and configuration before applying it to other studies.

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Acknowledgment

We acknowledge all contributors involved in the development of this code.

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In Memoriam

Our thoughts and prayers are with Jetal Agnihotri, who was also involved in the development of this code.