Gridded climate data for 1961-90 and scenarios for 2010-39 and 2040-69 periods

Documentation for gridded climate data for 1961-90 and scenarios for 2010-39 and 2040-69 periods

1961-1990 baseline climate

The file ‘Normals61.txt’ contains gridded monthly mean values for daily maximum and minimum air temperature and total precipitation for the 1961-1990 period. These data were constructed by interpolating monthly climate data as a function of latitude, longitude and elevation using ANUSPLIN (Hutchinson, 2000). ANUSPLIN uses thin plate smoothing splines as the interpolation technique (Hutchinson, 1995). Any stations with 5 or more years of record were used (Environment Canada, 1994). The grid is 500 arc seconds and was developed using a Digital Elevation Model (DEM) data, based on the National Topographic Series 1:250,000 topographic data. For details of these particular Canadian applications see McKenney et al. (2001) (see also Price et al. 2000).

File Name: Normals61.ZIP File Structure: Comma-delimited text file, compressed using WinZip. Variables on the file are as follows:
Latitude and Longitude (decimal degrees) 12 monthly values (Jan. – Dec.) for average maximum temperature, ºC 12 monthly values (Jan. – Dec.) for average minimum temperature, ºC 12 monthly values (Jan. – Dec.) for total precipitation, mm File Size: Zipped: 4.4 Mb; decompressed 12.7 Mb

Climate scenarios – 2010-2039 and 2040-2069

Climate change scenarios were based on the first generation coupled Canadian General Circulation Model, greenhouse gas with aerosols simulation 1 (CGCMI GA1). Mean monthly changes in temperature and in precipitation ratios from 1961-1990 values were interpolated to the same 500 arc second grid as above using ANUSPLIN with only latitude and longitude as predictor variables. The interpolated change values were then applied to the gridded 1961-1990 normals in ‘Normals61.txt’.

File Names: Normals10.ZIP (Monthly climate normals for 2010-2039 period) Normals40.ZIP (Monthly climate normals for 2040-2069 period) File Structure: Same as ‘Normals61.ZIP’ File Size: Similar to ‘Normals61.ZIP’

Calculation of agro-climatic indices

Agroclimatic indices were computed using the gridded monthly values as input data.  Initially, 365 daily values of average maximum temperature and of average minimum temperature were generated from monthly average values using the Brooks sine wave interpolation procedure (Brooks, 1943).  Average daily values for precipitation were generated by dividing the monthly values by the number of days in the month.  The average daily values were then used to compute the following indices:

Growing degree-days above 5ºC (GDD): GDD were computed by calculating the amount by which average daily mean temperature (Tmean) exceeded 5.0°C and summing these values from the time when Tmean first exceeded 5.0°C in spring until the last date of Tmean exceeded 5.0°C in fall. While this procedure will result in some differences from GDD computed from daily values rather than averages (since averages may include days when temperatures were below the base value in the spring and fall periods), it has been commonly accepted as being of sufficient accuracy (Chapman and Brown 1978)

Effective Growing Degree-Days (EGDD): EGDD are used as a primary climate classifier in the suitability rating system for spring-seeded small grains and are determined based on the method described in the Working Group report (Agronomics Interpretations Working Group, 1995). GDD were summed from 10 days after Tmean 5.0°C in spring to the average date of the first fall frost (0°C), and a daylength factor was applied to compensate for increased effectiveness of GDD in maturing cereal crops in northern latitudes. Average fall frost dates were estimated from monthly temperature normals, elevation and astronomical data as described by Sly et al. (1971). Daylength (N) and solar radiation at the top of the atmosphere (Qo) were estimated from latitude and time of year using procedures described by Robertson and Russelo (1968).

Potential Evapotranspiration (PE) and Precipitation Deficit (DEFICIT): Average daily PE was determined by calculating Latent evaporation (LE) from daily temperatures and solar radiation at the top of the atmosphere, using Baier and Robertson (1965) Formula I and converting LE to PE by using the conversion factor of 0.086. Average daily DEFICIT was calculated by subtracting average daily precipitation (P) from PE. Daily DEFICIT and PE values were accumulated over periods shown below.

Data og ressurser

Tilleggsinformasjon

Felt Verdi
Kilde http://www.cccsn.ca/Download_Data/Gridded_Climate_Data-e.html
Vedlikeholdes av BootsmaA@agr.gc.ca
date_released 2007-01-19
date_updated
department Environment Canada
federal_agency
level_of_government Federal
temporal_coverage-from 1961
temporal_coverage-to 2069
update_frequency

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