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About Me

I am a Ph.D. and my research stands in the intersection of Earth Science interdisciplinary.

I started programming and using GIS/Remote Sensing since 2005. I have been acquiring new skills ever since and am still learning. I use and build tools/models to solve problems across scales.

My ultimate goal is trying to understand how our nature works, especially under the changing climate. Without understanding our nature, we cannot appreciate how important it is to protect our only home, Earth.

In my opinion, science communication is very important and has always been understated. If I cannot explain my work to my wife, I cannot expect our public community to understand as well.

We all know it is not easy to understand nature, that is why we explore various ways to improve.

In a word, most of the articles I post here are related but not limited to Earth Science. These topics may cover:
  • Carbon cycle
  • Ecosystem
  • GIS
  • Hydrology (groundwater and surface water)
  • High Performance Computing
  • Permafrost
  • Programming
  • Remote Sensing
  • Snow dynamics
  • ...
All the posts will be original and are actual reflections of my research and potential publications. While publications do not always tell the whole story given limited resources and editors' preferences, it can be very difficult for audiences to fully understand a good research. That is why I am here to close the gap, a behind scene illustration of how science is actually done.

When I am not doing research, I do lots of activities including
  • basketball
  • BBQ (if it counts)
  • camping
    Yellowwood, IN
    Sugar Valley, IN
  • fishing
  • biking
  • hiking
    Death Valley, CA

    Ancient Lakes, WA
  • kayaking
    Columbia, WA

    South Ben, IN
  • swimming
    Colchuck Lake, WA
  • watching games
    DC

    Clemson, SC
  • ...
I am also active in several social networks including Twitter (@changliao1025).
Feel free to contact me if you have questions.




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.…