Compact Probe for In-Situ Optical Snow Grain Size Stratigraphy

Snowmelt provides >75% of California’s water. Mountain snow is the main water source for 60 million Americans. Snowmelt sustains one billion people globally. Snowpacks are rapidly changing.

Remote Sensing of Snow Snow Water Equivalent (SWE) – Radar SMAP, SCLP, Cryosat II, ERS 1 & 2, Sentinels – Microwave SCLP, EOS Aqua, Envisat, SMOS, ERS 1 &2

Remote Sensing of Snow SWE algorithms are limited by knowledge of grain size and understanding of the relation between signal and grain size variation.

Remote Sensing of Snow There exists no ground instrument to provide large datasets of grain size stratigraphy. Armstrong et. al., Annals of Glaciology, 17, 1993, “Snow depths and grain-size relationships with relevance for passive microwave studies”

Traditional Grain Size Measurements

Traditional Grain Size Measurement

Contact Spectroscopy Advantages – Less subjective – Repeatable – Faster – Data applicable to remote sensing Painter et al., Journal of Glaciology 2007

Spectral Profiler Probe Send optics down hole Lateral reflectance spectra Fiber optic sends signal to surface No snowpit! Much faster than pit methods probe carrier body drive tube optical camera spectral reflectance probe nylon brush aluminum sleeve fiber optic to spectrometer

optical inspection camera spectral reflectance probe nylon brush In-bore light source Spectral Profiler Probe Hardware

Field Testing probe stowed for transport Niwot Ridge, CO Storm Peak Lab, Steamboat Springs, CO

Storm Peak Lab Feb 2010 results Paper submitted to Journal of Glaciology

New version: Fast, Small, Cheap, Robust Use discrete optics – Eliminate spectrometer, fiber optic, pre drilling T measurement ~1cm dia. Probe Algorithms for on-site grain size retrieval

Ultra-compact probe design

Probe tip closeup

Discrete Optics Concept Test Re-processed spectral data using only 2 points

Lab test using LED’s Quick cold lab experiment using COTS LED and photodiode/ amplifier shows sensitivity to grain size. Detector + amplifier LED Snow in pan

Discrete Optics Concept Test availability of LED and laser sources. Wavelength (nm) reflectance

NILU collaboration Collect data from ESA and NASA satellites – Concurrent with probe data Develop improved algorithms for SWE – Test against ground measurements

The Future of Snow Science All measurements from space Need better retrieval algorithms Must understand grain size affect on signals Need large ground datasets to get there

supplemental

Acknowledgements Jennifer Petrzelka Ty Atkins Alex Arnsten Ian McCubbin (Storm Peak Lab) Gannet Hallar (Storm Peak Lab) Part of this work was performed at the Jet Propulsion Laboratory/California Institute of Technology under contract from NASA.

Compact Probe for In-Situ Optical Snow Grain Size Stratigraphy Daniel Berisford 1, Noah Molotch 1,2, Thomas H. Painter 1, Michael Durand 3 1.NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 2.INSTAAR, University of Colorado, Boulder, CO 3.The Ohio State University, Columbus, OH Presented at the American Geophysical Union fall meeting, San Francisco, CA. December 13, 2010

Contact Spectroscopy optical equivalent grain size obtained by integrating absorption feature and comparing to RT model Painter et al., 2007; Nolin and Dozier, 2000.

2 configurations fiber light In-bore light

Niwot Ridge April 2010 results

Field Testing tarp to block sunlight spectrometer

Field testing

Aluminum reflectance spectrum

Kapton tape reflectance spectrum