This set of files includes downscaled historical estimates of decadal means of monthly total precipitation (in milimeters, no unit conversion necessary) for each month of every decade from 1910 - 2006 (CRU TS 3.0) or 2009 (CRU TS 3.1.01) at 2x2 kilometer spatial resolution. Each file represents a mean monthly total in a given decade.
The spatial extent includes Alaska, the Yukon Territories, British Columbia, Alberta, Saskatchewan, and Manitoba.
Each set of files originates from the Climatic Research Unit (CRU, http://www.cru.uea.ac.uk/) TS 3.0 or 3.1.01 dataset. TS 3.0 extends through December 2006 while 3.1.01 extends to December 2009.
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Downscaling:
These files are bias corrected and downscaled via the delta method using PRISM (http://prism.oregonstate.edu/) 1961-1990 (for 2km Alaska and Western Canada data) or 1971-2000 (for 771 meter Alaska data) as baseline climate. Absolute anomalies are utilized for temperature variables. Proportional anomalies are utilized for precipitation variables.
For more detailed information on base input data (GCMs, historical data), emmission scenarios, the downscaling process, or uncertainty, please go to http://www.snap.uaf.edu/
Note that for CRU TS 3.x precipitation downscaling, due to large precipitation "holes" of zero-values in the original CRU TS 3.x data, any cells with a 30-yr climatology zero-value are withheld from the anomaly spline interpolation step of the downscaling process. This is done in order to avoid an undefined proportional anomaly calculation with 0 in the denominator.
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File naming scheme:
While it’s hard to have a completely static file naming scheme, we make every attempt to keep some consistency across our various datasets. This naming scheme outlined below is our general guide, although it does vary depending upon each dataset.
[variable]_[metric]_[units]_[format]_[assessmentReport]_[groupModel]_[scenario]_[timeFrame].[fileFormat]
some examples of these file names parts include:
[variable] pr, tas, logs, dot, dof, veg, age, dem
[metric] mean, total, decadal mean monthly mean
[units] mm, C, in, km
[format] optional, if layer is formatted for special use
[assessmentReport] ar4, ar5 (assessment report, for projected data only)
[groupModel] cccma_cgcm31, mpi_echam5, gfdl_cm21, ukmo_hadcm3, miroc3_2_medres, 5modelavg, cru_ts31
[scenario] sresb1, sresa2, sresa1b
[timeFrame] yyyy or mm_yyyy or yyyy_yyyy or mm_yyyy_mm_yyyy
[fileFormat] tif, txt, png, pdf
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full file name examples:
tas_mean_C_ar4_cccma_cgcm3_1_sresb1_05_2034.tif
This file represents May 2034 mean temperature in degrees Celsius from the 4th Assessment Report on Climate Change from the CCCMA modeling group, using their CGCM3.1 model, under the B1 climate scenario.
pr_decadal_mean_DJF_total_mm_cru_TS31_historical_1920_1929.tif
This file represents mean total winter(Dec, Jan, Feb) precipitation from 1920-1929 from downscaled CRU TS 3.1 data.
tas = near-surface air temperature
pr = precipitation including both liquid and solid phases
dof = day of freeze
dot = day of thaw
logs = length of growing season
