Spatial interpolation of point data
Interpolation of Hourly scalars to Sub-daily Basins
Below is an itemized description of the interpolation process, with open data access. All interpolated (i.e., “vector”) data are automatically updated and maintained using the ORMGP-FEWS system system.
workflow:
preprocessMSCtoBasinsHourly.xml
Meteorological Service of Canada (MSC) scalars
- Scrape MSC for recent data, executed from FEWS.
- Import scraped MSC hourly scalars into FEWS.
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Export hourly MSC NetCDF file (*.nc) from FEWS, from 1989-10-01
_exportMSChourlyNetcdf.nc
$T_a, p_a, r, \text{vis}, u, u_\alpha$ - Interpolate to 10km sub-watersheds, using a python script executed from config file
pyMSChourliesToBasin.xml
that executes:ncMSCtoHourlyBasinNetCDF.py
.- Air temperature $(T_a)$, relative humidity $(r)$ and wind speeds $(u)$ are interpolated using a radial basis function (RBF) (with a cubic kernel and a smoothing factor $\lambda=1/1000$ to prevent singular matrices).
- Air/barometric pressure $(p_a)$ are first corrected for elevation then interpolated using the same cubic RBF.
- Wind directions $(u_\alpha)$ are split into their x-y components, each interpolated separately using a cubic RBF before returned to an angle. A sample result is shown below:
- Interpolated $(T_a, r, u)$ are applied to compute potential evaporation flux [m/s] (Novák, 2012):
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Save to NetCDF (.nc) for import back to FEWS.
_exportMSChourlyNetcdf_interp.nc
$T_a, p_a, r, u, E_a$ hourly basins
Hourly Basin to 6-hourly Basin interpolation
- Hourly aggregation to 6-hourly time intervals (00:00 06:00 12:00 18:00 UTC) is performed in FEWS using the:
- MeanToMean aggregation routine for $Ta, p_a, r, u$, and
- Accumulative aggregation routine for $E_a$.
These data have a set expiry.
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Export 6-hourly, basin-interpolated $P_\text{HRDPA}, T_a, p_a, r, u$ to NetCDF.
yyyyMMddHHmm-6hourlyBasin.nc
to be altered to $P_\text{HRDPA}, P_R, P_S, T_a, p_a, r, u, E_a$
6-hourly Precipitation to Basins
The 6-hourly CaPA-RDPA precipitation $(P)$ field is a gridded raster that is routinely scraped of open web resources and proportioned to the sub-watersheds using our ORMGP-FEWS system, using the Interpolation: SpatialAverage transformation.
References
Novák, V., 2012. Evapotranspiration in the Soil-Plant-Atmosphere System. Springer Science+Business Media Dordrecht. 253pp.