Principal Investigator (PI): John Kimball, University of Montana

We propose to extend and enhance the Earth System Data Record (ESDR) quantifying daily landscape freeze/thaw (FT) state dynamics over all global vegetated land areas where seasonal frozen temperatures are a significant constraint to ecosystem processes, including land-atmosphere carbon, water, and energy fluxes. The freeze/thaw ESDR (FT-ESDR) captures dynamic seasonal to annual variability, and large regional and global trends in frozen temperature constraints to landscape water mobility and ecosystem processes in response to recent climate change. The proposed FT-ESDR continuity and enhancements will provide a continuous global data record encompassing almost four decades and representing one of the longest satellite environmental data records in existence, while providing an extended domain, finer spatial resolution FT retrievals for the northern latitudes and increased product science utility over the existing global baseline.

The proposed activities are the logical extension of an expiring Making Earth System Data Records for Use in Research Environments (MEaSUREs) activity— "An Earth System Data Record for Land Surface Freeze-Thaw State: Quantifying Terrestrial Water Mobility Constraints to Global Ecosystem Processes" (Kimball, PI; McDonald, Co-I), and build on a successful FT-ESDR developed by merging overlapping satellite passive microwave daily brightness temperature (Tb) records from the Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave Imager (SSM/I). The FT-ESDR includes a consistent and relatively precise (>80% mean spatial classification accuracy) daily (AM and PM) classification of the predominant frozen and non-frozen status of the landscape at moderate (25-km) resolution, with detailed metadata. We propose to continue the global FT-ESDR baseline by incorporating additional calibrated Tb records from the continuing SSM/I series, while documenting product accuracy in relation to global World Meteorological Organization station observations and similar FT retrievals from other satellite microwave records.

The proposed activities will utilize lessons learned from our initial FT-ESDR development and ongoing validation and product quality assessment activities. We will also evaluate potential enhancements to the FT-ESDR baseline, including an expanded product domain encompassing the larger cryosphere, production of regionally enhanced FT records for northern (>/=45N) land areas using similar overlapping Tb records from the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) and WindSat, with potential two- to four-fold spatial resolution enhancement over the existing FT-ESDR baseline.

The proposed FT-ESDR serves several Earth Science focus areas and associated user communities, including Water and Energy Cycle, Carbon Cycle and Ecosystems, and Climate Variability and Change. The initial FT-ESDR (version 01) is publicly available through the NSIDC DAAC; current (Feb-012) user metrics for these data indicate more than 2083 hits and 138 GB of data downloaded to the community, with more than 20 known scientific publications involving these data, while the number of users, science applications and publications from these data continue to grow. The proposed FT-ESDR continuity and enhancements will enable precise detection and diagnosis of both climate variability and long-term trends extending over almost 40 years. The proposed activities will directly benefit the Soil Moisture Active Passive (SMAP) mission, which has a planned mid-2014 launch and will provide an operational FT product similar to the FT-ESDR; the proposed data records will inform mission science and product development and validation, and provide baseline information for assessing the global change significance of future FT measurements from SMAP and associated accuracy requirements, validation and uncertainty measurements for meeting mission objectives.