Evaluation of stereology for snow microstructure measurement and microwave emission modeling: a case study

ABSTRACT

Reliable microstructure measurement of snow is a requirement for microwave radiative transfer model validation. Snow specific surface area (SSA) can be measured using stereological methods, in which snow samples are cast in the field and photographed in the laboratory. Processing stereology photographs manually by counting intersections of test cycloids with air–ice boundaries reduces the problems in binary segmentation. This paper is a case study to evaluate the repeatability of the manually stereology interpretation by two independent research groups. We further assessed how uncertainty in snow SSA influences simulated brightness temperature (T_B) driven by the Microwave Emission Model of Layered Snowpacks (MEMLS), and how stereology compares to Near Infrared (NIR) camera and hand lens. Data was obtained from two alpine snow profiles from Steamboat Springs, Colorado. Results showed that stereological SSA values measured by two groups are highly consistent, and the ground radiometer measured T_B at 19 and 37 GHz was successfully predicted (RMSE<3.8 K); simulations using NIR SSA and hand-lens geometric grain size (D_g) measurements have larger errors. This conclusion was not sensitive to uncertainty in the free parameters of T_B modeling.

KEYWORDS:

• Microwave radiometry
• snow
• stereology
• snow microstructure
• MEMLS

Acknowledgements

This work was supported by the NASA Terrestrial Hydrology Program under Grant no. NNX09AM10G and the Strategic Priority Research Program of Chinese Academy of Sciences under Grant no. XDA20100300. The authors would like to gratefully thank Ian McCubbin and Dr. Gannet Hallar for hosting us at Storm Peak Laboratory, Ty Atkins for his invaluable assistance with the radiometer, and Dan Berisford and Jennifer Petrzelka for their help in the snowpits. We would like to thank Abiyu Getahun for his work on the stereological processing.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by NASA Terrestrial Hydrology Program [grant number NNX09AM10G]; Strategic Priority Research Program of Chinese Academy of Sciences [grant number XDA20100300].