Spaceborne microwave remote sensing of seasonal freeze-thaw processes in the terrestrial high latitudes: Relationships with land-atmosphere CO 2 exchange

Kyle C. McDonald, John S. Kimball, Maosheng Zhao, Eni Njoku, Reiner Zimmermann, Steven W. Running

Research output: Contribution to journalConference articlepeer-review

Abstract

Landscape transitions between seasonally frozen and thawed conditions occur each year over roughly 50 million square kilometers of Earth's Northern Hemisphere. These relatively abrupt transitions represent the closest analog to a biospheric and hydrologic on/off switch existing in nature, affecting surface meteorological conditions, ecological trace gas dynamics, energy exchange and hydrologic activity profoundly. We utilize time series satellite-borne microwave remote sensing measurements from the Special Sensor Microwave Imager (SSM/I) to examine spatial and temporal variability in seasonal freeze/thaw cycles for the pan-Arctic basin and Alaska. Regional measurements of spring thaw timing are derived using daily brightness temperature measurements from the 19 GHz, horizontally polarized channel, separately for overpasses with 6 AM and 6 PM equatorial crossing times. Spatial and temporal patterns in regional freeze/thaw dynamics show distinct differences between North America and Eurasia, and boreal forest and Arctic tundra biomes. Annual anomalies in the timing of thawing in spring also correspond closely to seasonal atmospheric CO 2 concentration anomalies derived from NOAA CMDL arctic and subarctic monitoring stations. Classification differences between AM and PM overpass data average approximately 5 days for the region, though both appear to be effective surrogates for monitoring annual growing seasons at high latitudes.

Original languageEnglish
Article number28
Pages (from-to)167-178
Number of pages12
JournalProceedings of SPIE - The International Society for Optical Engineering
Volume5654
DOIs
StatePublished - 2004
EventMicrowave Remote Sensing of the Atmosphere and Environment IV - Honolulu, HI, United States
Duration: Nov 9 2004Nov 11 2004

Keywords

  • Arctic
  • Boreal
  • Carbon cycle
  • Freeze/thaw
  • Growing season
  • Net primary production
  • Remote sensing
  • SSM/I

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