Skip to main content

Ecosystem modeling: model evaluation of current implementation in ECO3D 1.0

As I am preparing my defense, the first version of ECOSYSTEM 1.0 in my thesis was finally completed. Looking forward to the next chapter of my life, I thought it is time to evaluate the ECOSYSTEM 1.0 to see what it is capable of and what still needs to be improved or expanded in the near future.

First, here is a brief introduction of the ECOSYSTEM model:
ECOSYSTEM is a three-dimensional water and carbon cycle terrestrial ecosystem model. Within ECOSYSTEM model, water and carbon cycle are seamlessly coupled. The water cycle is developed based on the PRMS, and the carbon cycle is developed based on TEM. The core idea behind the coupling is that both water and carbon (potentially nitrogen and others) fluxes can flow in a three-dimensional domain, and that is exactly one of the reasons why dissolved organic carbon (DOC) can be observed in stream water.

A lot of improvements have been made upon the original PRMS and TEM models. For example, I have added a new litter pool to consider the carbon pool, DOC leaching from the litter.

Even though model calibration of such kind of watershed hydrology-alike ecosystem model takes much effort, my initial model evaluation based on stream discharge, snow cover, GPP/NPP and DOC has shown that the three-dimensional approach have great potential. A good example could be something like the Riparian zone. I am also observing significant differences in soil moisture due to lateral water flow.

The ECOSYSTEM model is completely developed using C++11 with OpenMP enabled. A preview of the model structure was introduced in one of my early posts. One of the advantages of using C++ is that it's relatively easy to manage based on model structure, especially for models with sophisticated data I/O and flow.

Moreover, when I designed the ECOSYSTEM, a plugin approach/concept is used, which means that new processes can be easily added following the structure. This is also the same concept used in MODFLOW and PRMS.

With ECOSYSTEM, we can answer quite a few questions, including but not limited to:
  1. How is surface hydrology responding to climate?
  2. How is surface hydrology responding to land-use and land-cover change (e.g., wildfire)?
  3. What is the role of lateral flow in soil moisture?
  4. What is the role of lateral flow in carbon cycle?
  5. What about DOC dynamics?
However, due to the time constrain, I haven't implemented some other important processes into the ECOSYSTEM model currently. And potentially I will keep working on this project and finish a newer version when time is right.

Here are a few processes that need to be added or improved in future development:
  1. Groundwater flow is currently improved but not as good as MODFLOW, but it may be unnecessary to actually implement MODFLOW within ECOSYSTEM;
  2. Soil water has different types of reservoirs, but the concept of layered model may improve vertical profile, which is also important for thermal process;
  3. Soil thermal is currently simplified, it could be coupled with soil water using algorithm from TEM or other similar model such as GIPL;
  4. Three-dimensional heat transport is missing, but with soil thermal (or even groundwater flow), it could be implemented;
  5. Snow model currently does not consider heat from soil. A better layered snow model such as Snowpack can replace the current one;
  6. A dynamical stream network may be added, which means the hydrology networks vary with  time;
  7. Carbon and nitrogen coupling;
  8. Thermokarst lake modeling is missing;
  9. With thermal and soil carbon module, a new permafrost carbon release module could be implemented.
Hopefully, the last list will be shorted or even gone within one year.

Comments

Popular posts from this blog

Spatial datasets operations: mask raster using region of interest

Climate change related studies usually involve spatial datasets extraction from a larger domain.
In this article, I will briefly discuss some potential issues and solutions.

In the most common scenario, we need to extract a raster file using a polygon based shapefile. And I will focus as an example.

In a typical desktop application such as ArcMap or ENVI, this is usually done with a tool called clip or extract using mask or ROI.

Before any analysis can be done, it is the best practice to project all datasets into the same projection.

If you are lucky enough, you may find that the polygon you will use actually matches up with the raster grid perfectly. But it rarely happens unless you created the shapefile using "fishnet" or other approaches.

What if luck is not with you? The algorithm within these tool usually will make the best estimate of the value based on the location. The nearest re-sample, but not limited to, will be used to calculate the value. But what about the outp…

Numerical simulation: ode/pde solver and spin-up

For Earth Science model development, I inevitably have to deal with ODE and PDE equations. I also have come across some discussion related to this topic, i.e.,

https://www.researchgate.net/post/What_does_one_mean_by_Model_Spin_Up_Time

In an attempt to answer this question, as well as redefine the problem I am dealing with, I decided to organize some materials to illustrate our current state on this topic.

Models are essentially equations. In Earth Science, these equations are usually ODE or PDE. So I want to discuss this from a mathematical perspective.

Ideally, we want to solve these ODE/PDE with initial condition (IC) and boundary condition (BC) using various numerical methods.
https://en.wikipedia.org/wiki/Initial_value_problem
https://en.wikipedia.org/wiki/Boundary_value_problem

Because of the nature of geology, everything is similar to its neighbors. So we can construct a system of equations which may have multiple equation for each single grid cell. Now we have an array of equation…

Watershed Delineation On A Hexagonal Mesh Grid: Part A

One of our recent publications is "Watershed Delineation On A Hexagonal Mesh Grid" published on Environmental Modeling and Software (link).
Here I want to provide some behind the scene details of this study.

(The figures are high resolution, you might need to zoom in to view.)

First, I'd like to introduce the motivation of this work. Many of us including me have done lots of watershed/catchment hydrology modeling. For example, one of my recent publications is a three-dimensional carbon-water cycle modeling work (link), which uses lots of watershed hydrology algorithms.
In principle, watershed hydrology should be applied to large spatial domain, even global scale. But why no one is doing it?  I will use the popular USDA SWAT model as an example. Why no one is setting up a SWAT model globally? 
There are several reasons we cannot use SWAT at global scale: We cannot produce a global DEM with a desired map projection. SWAT model relies on stream network, which depends on DEM.…