Download presentation

Presentation is loading. Please wait.

Published byKarl Hoadley Modified over 4 years ago

1
Quantifying Rates of Soil Water Evaporation: Implementing a Soil Water Oxygen Isotope Model in Matlab Erik Oerter EPS 209 27 April 2011

2
Project Motivation: Soil Water Oxygen Isotopes Soil Water originates as meteoric water, preserving the isotopic signature of precipitation Hydrogen and Oxygen isotopes undergo Rayleigh fractionation as water evaporates Enrichment in 18 O relative to precipitation The 18 O/ 16 O can be sampled: Directly as soil water (contemporary water) Indirectly as CaCO 3 (ancient water) Use 18 O/ 16 O to estimate evaporation rate Climate Proxy

3
Evaporation Rate via Soil Water Oxygen Isotopes 18 O/ 16 O of water at z in soil profile Depth in soil profile Evap. Rate Depth of evap. front Diff coef. of water in soil 18 O/ 16 O of water at depth 18 O/ 16 O of water at evap. front (Barnes and Allison, 1988, J. of Hydrology) L = Total depth of soil profile

4
Project Idea: Fit modeled Oxygen isotope profile to observed data and find the evaporation rate Model 18 O profile Observed 18 O profile Data from Wang et al., 1996

5
Project Approach: m-file Sequence of Events 1)Load in observed data as text file 2)Initialize variables - Make an initial guess for evaporation rate - Populate a vector with evap guesses (~100) Specify the step between evap guesses - Initialize a matrix for calculated 18 O profiles (# depth increments x # evap guesses) 3)Loop over all evap guesses, calculating 18 O profiles - Now have 100 18 O profiles…

6
Project Approach: m-file Sequence of Events

7
Some Results Diffusion Coefficient of Water in Soil = 1.5*10 -10 m 2 /sec Starting Evap Rate Guess = 5x10 -11 m/sec (0.15 cm/year) E guess step = 1*10 -12 m/sec Best fit Evap rate = 1.02*10 -10 m/sec (0.32 cm/year)

8
Future Work This interpretation of the Barnes and Allison Model: - Single wet soil zone with the evaporating front at the surface Barnes and Allison envisioned a dry zone of soil overlying the wet zone and evaporating front at some depth Implement the two zone scheme - Allow for a migrating (+/- depth) evaporation front Allow for resetting of the 18 O input value (Allow it to rain on the soil)

Similar presentations

OK

Twenty Questions Science Review Chapter 1: Lessons 1 & 2.

Twenty Questions Science Review Chapter 1: Lessons 1 & 2.

© 2018 SlidePlayer.com Inc.

All rights reserved.

To ensure the functioning of the site, we use **cookies**. We share information about your activities on the site with our partners and Google partners: social networks and companies engaged in advertising and web analytics. For more information, see the Privacy Policy and Google Privacy & Terms.
Your consent to our cookies if you continue to use this website.

Ads by Google

Controller area network seminar ppt on 4g Ppt on case study research Ppt on recycling of waste papers Ppt on cleanliness and hygiene Ppt on business communication Background free download ppt on pollution How to present a seminar ppt on 4g Ppt on care of public property band Ppt on central limit theorem equation Ppt on brand management