12/21/2015 Real­time simulation of the iterative calculation of the satellite based surface energy fluxes | Ramesh Dhungel | LinkedIn

https://www.linkedin.com/pulse/real­time­simulation­iterative­calculation­satellite­based­dhungel 1/27

Attn: Civil Engineers ­ Get a Master's in Civil Engineering. No GRE. 100% Online. 4 Concentrations.

Real­time simulation of the iterative calculation ofthe satellite based surface energy fluxesDec 21, 2015 7 views 0 Likes 0 Comments

This will be a continuing post which will be updated until most of the

real time simulations are shown.

White paper

An iterative procedure is still used to converge fluxes in evapotranspiration (ET)

calculation in many ET models like METRIC, SEBAL and SEBS. In this post, a

real­time simulation is shown to expedite the satellite based surface energy

balance fluxes in low wind speed condition. In the surface energy balance,

stability correction of aerodynamic resistance is necessary as it affects the

computation of sensible heat flux. The Monin­Obukhov stability length (L) can be

calculated either from an iterative process using wind profiles, temperature and

Ramesh DhungelWater Resources, Remote Sensing and LandSurface Modeler (LSM) (Ph.D. Civil Engineering)

Edit post View stats

Real­time simulation of theiterative calculation of thesatellite based surface energ…fluxesRamesh Dhungel

Can Phil Schiller fix the AppleApp Store?qz.com

Naked Unicorns in SubprimeValleyVikram Mansharamani

The World Wide WebCelebrates 25th Birthday, ButWhat's Next?Neil Hughes

The Fed Awakens: A New HikeFrank Holmes

How Bad Design WreckedSteve Harvey's "Universe"Eric Thomas

From Oprah to Richard

Pulse Publish a post

Home Profile Connections Jobs Interests

Business Services Try Premium for free

Advanced

1

Search for people, jobs, companies, and more...

12/21/2015 Real­time simulation of the iterative calculation of the satellite based surface energy fluxes | Ramesh Dhungel | LinkedIn

https://www.linkedin.com/pulse/real­time­simulation­iterative­calculation­satellite­based­dhungel 2/27

humidity or through more complicated measurements of wind speed, sensible

heat flux, and latent heat flux. The Monin­Obukhov similarity functions are used

to define momentum (ψ) and heat (ψ) stability correction. While computing

Monin­Obukhov similarity functions, a set of the equations must be solved

iteratively as friction velocity (u*) and L (Monin­Obukhov length) are

interdependent. These variables should be revised until the parameters of the

surface energy balance converge within prescribed limits between successive

iterations.

Some technical details:

Improved Methodology ( Dhungel et al., 2014)

Programming language: Python and ArcScript

Plot: matplotlib

Date of the satellite overpass: 05/17/2008 (Landsat 5)

12/21/2015 Real­time simulation of the iterative calculation of the satellite based surface energy fluxes | Ramesh Dhungel | LinkedIn

https://www.linkedin.com/pulse/real­time­simulation­iterative­calculation­satellite­based­dhungel 3/27

Weather data­ NARR (32 km resolution)

Area: Southern Idaho near Raft River

Number of pixels: 1455408

Area: 1300 km2

Convergence criteria: Convergence of aerodynamic resistance within + 1

second / meter

System properties: Intel ® Core (TM) i7­4790 CPU @ 3.6 GHz

Installed memory (RAM): 32 GB

System type: 64­bit Operating System

Recording software: eLecta Live Screen Recorder

Plotting example:

T_cells= Total cells

C_cells= Converged cells

N_cells= Non­converged cells

T_cells = C_cells + N_cells

P_Convg = float(C_cells)/T_cells * 100.0000

N = 50

y= P_Convg

colors = np.random.rand(N)

s = 8 * iteration ** 1.2

plt.scatter(iteration, y,s,c=colors,alpha=0.5,marker=(5, 3),zorder=2)

plt.hold(True)

stop=time.time()

12/21/2015 Real­time simulation of the iterative calculation of the satellite based surface energy fluxes | Ramesh Dhungel | LinkedIn

https://www.linkedin.com/pulse/real­time­simulation­iterative­calculation­satellite­based­dhungel 4/27

test=(stop ­ start) / 60

test1=("%.2f" % test)

plt.title('Improved Methodology ­ Minutes=%s' % test1, fontsize=18)

Increased dots means increased % of convergence:

Wind speed at set 0.8 m/s (minimal value) to understand the extreme behavior.

(97.5 % convergence of pixels at 0.8 m/s wind speed at 30 m, process

manually stopped at about 70 minutes)

12/21/2015 Real­time simulation of the iterative calculation of the satellite based surface energy fluxes | Ramesh Dhungel | LinkedIn

https://www.linkedin.com/pulse/real­time­simulation­iterative­calculation­satellite­based­dhungel 5/27

Real-time simulation of the surface en...

(99.5 % convergence of pixels at 0.8 m/s wind speed at 30 m, process

automatically stopped at about 13 minutes)

12/21/2015 Real­time simulation of the iterative calculation of the satellite based surface energy fluxes | Ramesh Dhungel | LinkedIn

https://www.linkedin.com/pulse/real­time­simulation­iterative­calculation­satellite­based­dhungel 6/27

Written byRamesh Dhungel

0 comments

Real-time simulation of the surface en...

For the further reading, references and to cite the work, please go to

the following literature.

Dhungel, Ramesh, Richard G. Allen, Ricardo Trezza, and Clarence W. Robison.

"Comparison of Latent Heat Flux Using Aerodynamic Methods and Using the

Penman–Monteith Method with Satellite­Based Surface Energy

Balance." Remote Sensing 6, no. 9 (2014): 8844­8877.

Dhungel, R.; Allen, R. Time Integration of Evapotranspiration Using a Two

Source Surface Energy Balance Model Using NARR Reanalysis Weather and

Satellite Based METRIC Data. Ph.D. Thesis, University of Idaho, Kimberly, ID,

USA, 2014

http://digital.lib.uidaho.edu/cdm/ref/collection/etd/id/829

Dhungel et al., 2015. Improving iterative surface energy balance convergence for

satellite­based flux calculation, 15804L. Journal of Applied Remote Sensing

(Under­review).

Like Comment