Aloha! Welcome to Yu-Fen Huang’s website!

Here, I share the knowledge of hydrology, data analysis, and water along with my Ph.D. journey. Also, I’d love share different things that I’ve learned to you. Mahalo (thanks) for stopping by.

Map of the website:

  • About - About Yu-Fen Huang, including contact, research focus, current projects and position, and CV.
  • Academic - Anything related to hydrology, data analysis, water, and Ph.D. life.
  • Discover - Things I’ve learned or discovered; stay in adventure!
  • Products - Products I’ve made in the past, including publication, poster, oral presentation, programming scripts, or programming package, etc.
  • Gallery - Gallery for my work and life. :)

I hope you enjoy, and please feel free to leave messages or comments.


2019 May - June: Modeled ungaged stream and estimated the streamflow for five locations in Wailua, Kauai, by the Soil & Water Assessment Tool (SWAT) to help CWRM‘s project of the instream flow standard.

2016 - 2018: Understand tropical watershed (PI: Dr. Yinphan Tsang).

2018 Fall: White paper to The State of Hawaiʽi Greenhouse Gas Sequestration Taskforce: Agroforestry and Greenhouse Gas Sequestration in Hawaiʽi: Analyzing policies to promote agroforestry as a greenhouse gas sequestration strategy in Hawaiʽi (by Friswold, Brooke; Hastings, Zoe; Hendrickson, Cole; Huang, Yu-Fen). Presented to the State of Hawaiʽi Greenhouse Gas Sequestration Taskforce on 12/7/2018 and to DLNR on 12/19/2018.

2017 Spring: Understanding Manoa Watershed

2016 Summer: Comparison of Flood Inundation Mapping Techniques between Different Modeling Approaches and Satellite Imagery

2013 - 2015: Summer Leeside Rainfall Maxima over the Island of Hawaii (PI: Dr. Yi-Leng Chen)

2011 - 2013: The re-built typhoon, Fanapi (PI: Dr. Ming-Jen Yang)

Huang, Y. and Y. Chen (2019). Numerical Simulations of Seasonal Variations of Rainfall over the Island of Hawaii. J. Appl. Meteor. Climatol., 58, 1219–1232,

Munasinghe, D., Cohen, S., Huang, Y-F., Tsang, Y., Zhang, J. and Fang, Z. (2018). “Inter-comparison of Satellite Remote Sensing Techniques of Flood Inundation Mapping”. Journal of the American Water Resources Association (JAWRA) 54(4): 834-846.

Zhang, J., Munasinghe, D., Huang, Y-F., Fang, Z., Cohen, S., and Tsang, Y.P (2018). “Comparative Analysis of Inundation Mapping Approaches for the 2016 Flood in the Brazos River, Texas”, Journal of the American Water Resources Association (JAWRA) 54(4): 820-833.

Cohen, S., Brakenridge, G. R., Kettner, A., Bates, B., Nelson, J., McDonald, R., Huang, Y-F., Munasinghe, D., and Zhang, J., (2017). Estimating Floodwater Depths from Flood Inundation Maps and Topography. Journal of the American Water Resources Association (JAWRA) 54(4): 847-858.

Zhang, J., Munasinghe, D., & Huang, Y-F. (2016). Comparison of Flood Inundation Mapping Techniques between Different Modeling Approaches and Satellite Imagery. NATIONAL WATER CENTER INNOVATORS PROGRAM SUMMER INSTITUTE REPORT 2016, 4, 46.

Personal Driven

In 2016, I joined Tsang Hydrology Lab because I want to know what’s happening when the rain hit the ground. With the same amount of rainfall, why did cause flood sometimes but sometimes not?

Yet, in the first two year, I wasn’t really focus on my questions since everything was so new, so interesting, and so inspiring after I switch my major from atmospheric sciences into natural resources and environmental management. I wondered if I should go for water right, water and watershed management, drought, climate impact on island water, stream ecosystem, geomorphology, etc. Whatever I saw or read, I wanted to do the research of it. One day, Yinphan told me that I should focus on just few topics, and it’s about the time to come up with dissertation proposal, so I re-think my research questions, and decided to go back to my original questions - flood/flash flood.

Community Driven

Besides my personal interests, flash flood threats and costs the most in Hawaii (Figure 2 to Figure 4), although flash flood is not the most frequent hazard (Figure 1). Lack of study about extreme stream events in Hawaii while global warming is changing the hydrological cycle and we are expecting more extreme rainfall events that might cause more flooding. Better knowledge of the mechanism and trends of flash flood in Hawaii would help our decision of future planning, financial focus, infrastructure design, etc. Also, our stream natives relies on those flood events as signals to swim/climb back to the islands. Any shifts of magnitude and occurrence time would affect our stream ecosystem that the “how so” and “how much it matters” are still unknown. I hope I can somehow help our communities a little bit from my research.

The counts of each hazard in Hawaii from 1998 to 2018:

Figure 1. The counts of each hazard in Hawaii from 1998 to 2018

The damages of each hazard in Hawaii from 1998 to 2018:

Figure 2. The counts of death during flash flood events in Hawaii from 1998 to 2018

Figure 3. The counts of injuries during flash flood events in Hawaii from 1998 to 2018

Economical loss:
Figure 4. The reported economical loss from flash flood in Hawaii between 1998 and 2018

For all the students that are considering graduate school, especially a Ph.D. degree:

I didn’t know much about graduate school and studying abroad until I struggled and heard others good experiences, struggles, or lessons. None of my family member has studied abroad, and only one of them has a Master degree. Teachers/Professors in school rarely told us what should we be aware to study in a higher education abroad, they are generally happy for us if we want to study more. :)

I would like to do or know more about these niches before I entered the graduate school (kind of too late now. :p) An advisor is crazily super important for a graduate student, especially for a Ph.D. student. Different advisor will direct you into different research topics, approaches and methods, emotional loading, and even different life style. So…

Before you choose your academic advisor:

  1. Always talk to a many people as you can who knows the potential advisors

    • How do people like them?
    • What are their leading style?
    • How did they mentor their students before?
    • Are there any rumors about them?
    • What are the experts and personal characters of them?
    • Are they supporting different gender, culture, etc.? Are they okay with you having a baby during your study (if you plan to have kids in your life)?
  2. Have a in-person or video meeting with your potential advisors

    • Are you feeling good and conformable talking with them?
    • Are they planning to stay long term? Are they got tenure? (is there any potential that they would leave while you’re in the program)
    • What are their philosophy of mentoring?
    • What do they expect from a graduate student in terms of M.S. or Ph.D. students?
    • Can you support yourself financially? Do they have or potentially have funding for you?
    • Are they supporting different gender, culture, etc.? Are they okay with you having a baby during your study (if you plan to have kids in your life)?
  3. Understand the university or department policies and environments of your potential advisors are in

    • Do you like the policies and environment of the university and the department? If no, are you willing to tolerate them because you’d like to follow that advisor so much?
    • Student environment is one important part of your graduate student life, please do consider the atmosphere within graduate students and faculties. Is the environment competitive or cooperative?

It was always amazing to watch Merrie Monarch. Besides hula, I can learn about Hawaiian mele (songs) and also the hula instruments. I’ve been watching Merrie Monarch for 3 years, and I’m still learning about the hula instruments that I’ve never seen. In Merrie Monarch 2019, there are two interesting instruments - ʻulili and ʻukēkē.


I thought it was some kind of ʻuliʻuli while watching TV. But kumu Noe told us that it was ʻulili. It made from the fruit of laamia (Crescentia cujete). The end gourds contain alii poe (canna) seeds, and when dancers pull the cord to make the gourds spin, the result is a whirring sound. Besides insterement ʻulili also stand for a shorebird!

ʻulili photo from


Kumu told us that there was only one person knows how to play the ʻukēkē, but now it’s amazing to see a group of people playing it in Merrie Monarch. I don’t know if that’s the reason that the group won the first place of Kane hula Kahiko.

“The ʻukēkē is made of koa wood, 16 to 24 inches long and about 1½ inches wide with two or three strings fastened through and around either end. The strings were strummed with one hand while the other hand kept the ʻukēkē in position. The mouth would then act as a resonating chamber. The ʻukēkē is the only stringed instrument indigenous to Hawaii, with other Hawaiian string instruments like the ukulele and slack-key guitar having been introduced by European sailors and settlers.” from Wikipedia

The music with ʻukēkē:

As a hydrological modeler, meteorological forcing is always crucial and challenging. Although I’ve heard re-analysis for a quite long time, I’ve never really tried to understand it till now. All I knew was that reanalysis is combining observation and model to produce gridded, 3-dimensional atmospheric data.

I found a BAMS essay by Wendy S. Parker (September 2016): REANALYSES AND OBSERVATIONS - What’s the Difference?. My idea of reanalysis wasn’t too far, yet I was surprised that the re-analysis is not too different from observation except that we have less understanding of accuracy and uncertainty in re-analysis than observation.

Reanalysis is a product of gridded comprehensive snapshots of conditions at a regular interval over long time periods by data assimilation. Data assimilation is a process to use information to estimate as accurately as possible the state of a system (Talagrand 1997) - combining various observations, including ground-based station ship, airplanes, satellite ,radar, etc. and the initial guess from numerical weather prediction (NWP) models. The first guess of NWP models is from the previous observation along with theory-based calculation.

Then, people debated that re-analysis differs significantly from observations:

  1. Reanalysis results are obtained by inference, while observation are not.
  2. Reanalysis relies on forecasts, while observation does not.
  3. Reanalysis involves solving an ill-posed inverse problem, while observation does not.
  4. The accuracy of reanalysis results is less well understood than that of observations.

After thoroughly considering the claims one by one, Wendy (2016) concluded:

  1. Both observations and reanalyses involve inference - either derived measurements or indirect observations. So it’s not different between both in this perspective.
  2. They are different in this case but not significant. The only thing matters is whether results are sufficiently accurate.
  3. They are different sometimes but not necessarily significant, it just depends if the solution is sufficiently accurate.
  4. The lack of understanding in the accuracy of reanalysis has significant differences in some cases. It’s harder to judge the usage of reanalyses in those cases.

That said, I should feel secure while using reanalysis as my meteorological forcing besides the ground-based observation if I don’t need to consider the uncertainties. Yet most of reanalysis data has a very coarse spatial-resolution and okay temporal-resolution, I wonder if there any way to get higher resolution reanalysis?

Also, I’m not sure why we don’t use the validation or forecasting result to introduce the uncertainty of reanalysis? Do you know?

The Waterhackweek has just finished today. It was a great opportunity to work on the project that has technical problem with more experienced people. Besides, I got to met people who created python package and learned how to use their packages and how to build a package.

Yinphan and I proposed a project about blending meteorological data and making them into the NetCDF format that WRF-Hydro can read. We didn’t really touch the blending part since most of time we were dealing with re-formatting and re-gridding. Although we didn’t complete during the waterhackweek, I would like to continue it. And hopefully, I can use it for my Ph.D. research. ;)

The flowchart shows what we proposed and want to do.

There were a lot of cardboard boxes on the ground with his stocks inside when I visited my friend’s place. I asked him “don’t you feel inconvenient walking around?” He said yes, but he got used to it and didn’t know what he can do for his stocks.

I asked him “do you want to buy a shelf?” He said he doesn’t want to spend money on the shelf and there is no elevator in his place. Then I look at those boxes, they are mostly in the same size… hmmm, good shape! I told my friend “I can make shelf for you with these boxes.”

At beginning, he rejected my idea, he said “those stocks are heavy, the cardboard boxes can’t hold them for long time. I don’t want them crash and destroy my stocks.” I insisted “How about let’s try first and observe, if you still think it’s still not a good ideal, I’ll restore them.” Then, I made this shelf within half hour.

A year after, I asked him “how do you like the shelf?” He said “I love them! It’s super useful and convenient that I can organize and get the model I need very easily. Thank you!” I got confirmed that they did well and last long, so I decided to post here!

Let’s see how I made this quick and dirty but long-lasting cardboard box shelf!

You don’t need much, but be prepared

You will need:

  • Cardboard box * (see how many you want)
  • A scissor or a knife
  • A heavy duty tape

Make one block of the shelf

Cut the sides and make the support

This is the secret (not anymore) of the long-lasting! Cut both inner flaps (short sides) by a scissor or a knife (obvious I like knife more in the video :p). Then tape both flaps together, and put it to the side for now.

Fix the side with tape for easier to stack up the boxes.

Locate the support in the middle/center of the box.


Depends on what size of shelf you want, repeat previous steps till you’re satisfied or exhausted. Note that The top layers don’t really need support if you’re not putting stuffs above them. ;)

(Note: you can also have different size of boxes to have different size for each block. Also, I don’t stick or tie the boxes together because I want the flexibility that I can re-arrange the boxes easily, but you can tie them with tapes or plastic ties if you’re not moving them here and there.)

Your browser is out-of-date!

Update your browser to view this website correctly. Update my browser now