ABoVE: Monthly Hydrological Fluxes for Canada and Alaska, 1979-2018

This dataset provides modeled estimates of monthly hydrological fluxes at 0.25-degree resolution over Alaska and Canada for the years 1979-2018. The estimates were derived from the Variable Infiltration Capacity (VIC) macroscale hydrological model version 4.1.2 with water and energy balance schemes at 0.25-degree spatial and daily temporal resolution for this 38-year period. The gridded output data products are monthly average water balance variables including precipitation (P), evapotranspiration (E), 'P minus E', evaporation, soil moisture in three soil layers, base flow and runoff, snow depth, snow water equivalent (SWE), and snow sublimation, and energy balance variables including surface temperature, albedo, latent and sensible heat flux, ground heat flux, short- and long-wave and other radiative fluxes. The daily modeled values for precipitation and evapotranspiration were also aggregated to water years and precipitation was also aggregated to a 30-year climate normal average.

The spatial extent specifically includes the Core and Extended study areas of the Arctic Boreal Vulnerability Experiment (ABoVE) in Alaska and Canada plus all areas of eastern and northern Canadian provinces. The model forcing data were a temporal combination of (1) the Climate Forecast System Reanalysis (CFSR) extension for land surface hydrological modeling i.e., CFSR-Land, developed by Coccia and Wood (2018, in review) for 1979-2011 and (2) data extended to March 31, 2018 using Climate Forecast System Version 2 (CFSv2) forecast and reanalysis products.

There are 26 data files with this dataset which includes 25 data files in NetCDF (.nc4) format and the precipitation climate normal data in GeoTIFF (.tif) format.

This dataset provides modeled estimates of monthly hydrological fluxes at 0.25-degree resolution over Alaska and Canada for the years 1979-2018. The estimates were derived from the Variable Infiltration Capacity (VIC) macroscale hydrological model version 4.1.2 with water and energy balance schemes at 0.25-degree spatial and daily temporal resolution for this 38-year period. The gridded output data products are monthly average water balance variables including precipitation (P), evapotranspiration (E), 'P minus E', evaporation, soil moisture in three soil layers, base flow and runoff, snow depth, snow water equivalent (SWE), and snow sublimation, and energy balance variables including surface temperature, albedo, latent and sensible heat flux, ground heat flux, short- and long-wave and other radiative fluxes. The daily modeled values for precipitation and evapotranspiration were also aggregated to water years and precipitation was also aggregated to a 30-year climate normal average.

The spatial extent specifically includes the Core and Extended study areas of the Arctic Boreal Vulnerability Experiment (ABoVE) in Alaska and Canada plus all areas of eastern and northern Canadian provinces. The model forcing data were a temporal combination of (1) the Climate Forecast System Reanalysis (CFSR) extension for land surface hydrological modeling i.e., CFSR-Land, developed by Coccia and Wood (2018, in review) for 1979-2011 and (2) data extended to March 31, 2018 using Climate Forecast System Version 2 (CFSv2) forecast and reanalysis products.

Project: Arctic-Boreal Vulnerability Experiment

The Arctic-Boreal Vulnerability Experiment (ABoVE) is a NASA Terrestrial Ecology Program field campaign based in Alaska and western Canada between 2016 and 2021. Research for ABoVE links field-based, process-level studies with geospatial data products derived from airborne and satellite sensors, providing a foundation for improving the analysis and modeling capabilities needed to understand and predict ecosystem responses and societal implications.

Acknowledgements:

This study was funded by the NASA Terrestrial Ecology Program, ABoVE grant number NNX17AC60A

Spatial Coverage:  Alaska and Canada

Spatial Resolution: 0.25 degree

Temporal Coverage: Most data cover the period 1979-01-01 to 2018-04-01. The three 'water year' files end on 2017-10-01.

Temporal Resolution: Monthly 

Study Areas (All latitude and longitude given in decimal degrees)

Site	Westernmost Longitude	Easternmost Longitude	Northernmost Latitude	Southernmost Latitude
Alaska and Canada	-172.2497361	-53.42553056	83.125	41.75075278

 

Data File Information

There are 26 data files with this dataset, including:

• 22 NetCDF files with monthly aggregations of the daily modeled output over the 471 months of the 1979-01-01 to 2018-04-01 period. Each file provides data for one model output variable.
• Three NetCDF files with "water year" aggregations of the daily modeled output over the 38 water years in the 1979-10-01 to 2017-10-01 period. Water year is defined as the 12-month period beginning on October 1. The water year is designated by the calendar year in which it ends.
• One GeoTIFF file with the '30-year climate normal' data consisting of the daily modeled output for precipitation averaged over the 30 year period 1979-2010.

No data values: 

• The no data value for all files (except upward_latent_heat_flux_monthly.nc4) is zero (0).
• The no data value for upward_latent_heat_flux_monthly.nc4 is -9999.  There are grid cells with data values of 0.

Spatial Data Properties

All NetCDF files have EPSG: 4326

The GeoTIFF file 'Precipitation_Climate_Normal_1979-2010.tif'  has one data band, the no data value = 0, and EPSG: 4326.

 

 Table 1. File names and Variables

File Name	Variables	Units/format	Description
Water Balance Variables
precipitation_monthly.nc4	OUT_PREC	kg/m2	Precipitation
evapotranspiration_monthly.nc4	EVAP	kg/m2	Monthly evapotranspiration
canopy_evap_monthly.nc4	EVAP_CANOP	kg/m2	Net evaporation from canopy interception
bare_soil_evap_monthly.nc4	EVAP_BARE	kg/m2	Net evaporation from bare soil
moisture_intercept_storage_monthy.nc4	WDEW	kg/m2	Total moisture interception storage in canopy
vegetation_transpiration_monthly.nc4	TRANSP_VEG	Kg/m2	Net transpiration from vegetation
soil_moisture_monthly.nc4	SOIL_LIQ1, SOIL_LIQ2, and SOIL_LIQ3	kg/m2	Soil moisture at 3 levels: top=LIQ1, middle=LIQ2, and bottom=LIQ3
snow_depth_monthly.nc4	SNOW_DEPTH	cm	Snow Depth
snow_water_equivalent_monthly.nc4	SWE	kg/m2	Snow Water Equivalent
net_snow_sublimation_monthly.nc4	SUB_SNOW	kg/m2	Total net sublimation from snowpack (surface and blowing)
canopy_snow_sublimation_monthly.nc4	SUB_CANOP	kg/m2	Net sublimation from snow stored in canopy
baseflow_monthly.nc4	BASEFLOW	kg/m2	Baseflow
runoff_monthly.nc4	RUNOFF	kg/m2	Runoff
Energy Balance Variables
surface_temperature_monthly.nc4	SURF_TEMP	Degrees C	Average surface temperature
radiative_surface_temp_monthly.nc4	RAD_TEMP	Degrees C	Average radiative surface temperature
upward_latent_heat_flux_monthly.nc4	LATENT	W/m2	Net upward latent heat flux
upward_sensible_heat_flux_monthly.nc4	SENSIBLE	W/m2	Net upward sensible heat flux
ground_heat_flux_monthly.nc4	GRND_FLUX	W/m2	Net heat flux into ground
surface_albedo_monthly.nc4	ALBEDO		Average surface albedo (albedo as a fraction)
downward_shortwave_flux_monthly.nc4	NET_SHORT	W/m2	Net downward shortwave flux
downward_radiation_flux_monthly.nc4	R_NET	W/m2	Net downward radiation flux
aerodynamic_resistance_monthly.nc4	AERO_RESIST	m-1/s	"Scene" canopy aerodynamic resistance (tiles with overstory contribute overstory resistance; others contribute surface resistance)
Water Year Files
precipitation_water_year.nc4	OUT_PREC	kg/m2	Precipitation for the water year, 38 years
evapotranspiration_water_year.nc4	EVAP	kg/m2	Evapotranspiration for the water year, 38 years
precip_evapo_water_year.nc4	P_E	kg/m2	Precipitation minus Evapotranspiration for the water year, 38 years
Precipitation Climate Normal
Precipitation_Climate_Normal_1979-2010.tif	OUT_PREC	mm/year	Climate Normal (30-year average in mm/year) for the period 1979-2010

 

These data provide estimated historical climate information for the ABoVE study domain, which can be used to understand hydrological trends associated with climate change.

For validation of the data product, Environment and Climate Change Canada (ECCC) gauges, ECCC climate normal (1981-2010), and station based gridded data CRU.TS.4.01 (Harris et al., 2014) were used. Evaluation of the data product for regional and seasonal biases showed that in higher elevations there is a positive bias, especially in the Rocky Mountains of British Columbia, Yukon, and Alaska, but considering the domain-wide region, the data product agrees well with the recent climate normal (1981-2010) published by ECCC. Seasonal bias was found to be negligible across all regions.

Known problems that may limit use:

1. Some missing points (gaps) were filled with nearest neighbor interpolation.
2. The monthly mean quantile values of Precipitation, Wind Speed and Temperature for the period 2011-2018 were mapped to match the quantile values of the reference period 1979-2010.
3. Modeled evaporation does not account for lakes, and this may represent a significant amount of evaporation. An update to the data product including explicit lake characterization will be released in 2019.

The Variable Infiltration Capacity (VIC) model, a macroscale hydrologic model that solves full water and energy balances (Liang et al., 1994) over a gridded land surface, was used for data simulations.

The model forcing data were derived from a combination of (1) Climate Forecast System Reanalysis (CFSR) extension for land surface hydrological modeling i.e., CFSR-Land, developed by Coccia and Wood (2018, in review) for the time period 1979-2011. CFSR-Land is an extension of the Sheffield et al. (2006) dataset, which constitutes global meteorological forcing for land surface models. And, (2) Climate Forecast System Version 2 (CFSv2) products were used to extend the data to March 31, 2018. CFSv2 includes an upgraded four-level soil model, an interactive three-layer sea ice model, and historically prescribed (i.e., rising) CO₂  concentrations (Saha et al., 2014).  Monthly means were matched with CFSR-Land by quantile mapping at the monthly scale. The number of rain days were also corrected to match CFSR-Land.

The Variable Infiltration Capacity (VIC) macroscale hydrological model version 4.1.2 with water and energy balance schemes was run at 0.25 degree spatial resolution and daily temporal resolution. The data product produced included gridded files (netcdf) of several water balance variables such as precipitation (P), evapotranspiration (E), P-E, soil moisture in 3 soil layers, snow depth, snow water equivalent, etc. and energy balance variables such as albedo, latent heat, short- and long-wave and other radiative fluxes.

Harris, I., P. D. Jones, T. J. Osborn, and D. H. Lister. 2014. “Updated High-Resolution Grids of Monthly Climatic Observations – the CRU TS3.10 Dataset.” International Journal of Climatology 34 (3): 623–42. https://doi.org/ 10.1002/joc.3711

Coccia, G., Wood, E., 2018. CFSR-Land: a new High Temporal Resolution Global Land Data Assimilation Product (in review).

Liang, X., D. P. Lettenmaier, E. F. Wood, and S. J. Burges, 1994: A Simple hydrologically Based Model of Land Surface Water and Energy Fluxes for GSMs, J. Geophys. Res., 99(D7), 14,415-14,428. https://doi.org/10.1029/94JD00483

Saha, S., S. Moorthi, X. Wu, J. Wang, S. Nadiga, P. Tripp, D. Behringer, Yu-T. Hou, M. Iredell, M. Ek, J. Meng, R. Yang, M.P. Mendez, H. van den Dool, Q. Zhang, W. Wang, M. Chen, and E. Becker. 2014. “The NCEP Climate Forecast System Version 2.” Journal of Climate 27 (6): 2185–2208. https://doi.org/10.1175/JCLI-D-12-00823.1