Climate Trend Mapper (CTM) – an interactive desktop application with which users can visualize temperature and precipitation trends across Canada using Environment Canada’s AHCCD data.
This program makes it easy for you to visualize the climate data and trends recorded at weather stations across Canada. In particular, the program allows you to produce high-quality maps of the trends (or lack thereof) observed in the monthly, seasonal and annual temperature and precipitation data. For temperature, you can map the trends in the maximum, minimum and mean temperatures. For precipitation, you can map the trends for rain, snow and total precipitation.
Introduction – Climate Trend Mapper
Climate Trend Mapper is a computer program designed using IDL for Windows. This program makes it easy to visualize the climate data and trends recorded at weather stations across Canada. In particular, the program allows you to produce high-quality maps of the trends (or lack thereof) observed in the monthly, seasonal and annual temperature and precipitation data. For temperature, you can map trends in the maximum, minimum and mean temperatures. For precipitation, you can map trends for rain, snow and total precipitation. The site is a visualization tool; it is not meant to provide detailed statistical analyses of trends.
What type of data do we use?
The data being mapped are Environment Canada’s Adjusted and Homogenized Canadian Climate Data (AHCCD). These are long-term data that have been quality-controlled and adjusted as necessary to remove bias that may have been introduced by, for example, site or instrument changes, urban heat islands, or observer error. The daily, monthly, seasonal and annual data are available from: http://www.cccma.ec.gc.ca/hccd/. Data is currently available for the years 1840-2010. The user can select the years to be included in the map. We thank Environment Canada for this excellent data set.
How to install and run the CTM program
To run the program, you will first need to download and install the current version of IDL Virtual Machine (version 8.0 or newer), a free download available here (~500 MB). You will have to register for and install the full version of IDL; however you do not have purchase IDL to run Virtual Machine. Then simply download and unzip the CTM program files onto your computer. Double click the .sav file to run the program. CTM works best on high-res monitors.
R. Smith and D. Blair, 2012. University of Winnipeg, Department of Geography.
What are ‘trends’?
Very simply: for each station meeting the criteria to be included in a map, we calculate the slope of the least-squares regression line fitted to the station’s time series for a given climate variable. These slopes are then mapped using IDL’s powerful MIN_CURVE_SURF and CONTOUR mapping functions, with the thin-plate spline option to interpolate the data. We realize that linear regression is not necessarily robust, given the amount of variability (and non-linearity) within the climate data series, especially in the precipitation data. The user is advised to be cautious. Note that the slopes of the lines are expressed in degrees Celsius per century for temperature, mm per century for rain and total precipitation, and cm per century for snow.