Canadian Effort for Improved Precipitation – Present Status and Transfer Function Development

Good quality precipitation observation is a critical element of the water cycle and is fundamental for streamflow, climate and weather forecasting. However, it is one of the most difficult climate variables to measure accurately. Several groups within Environment and Climate Change Canada (ECCC) are involved in obtaining, managing, using and distributing precipitation data. The ECCC Precipitation Round Table (PRT) was established to provide inter-departmental coordination to the Meteorological Service of Canada’s Surface Renewal Project as an exchange mechanism aiming for integration and optimization of precipitation data and product related activities. The objective of the PRT is to ensure that all requirements are considered with respect to measurements, processing, utilization, product development and distribution of precipitation data. Within the PRT, special focus is given to the quality of the precipitation observation. Key users such as National Weather Prediction (NWP) and Canadian Precipitation Analysis (CaPA) identified the need to develop and apply a transfer functions for precipitation gauge wind bias adjustments applicable for diverse Canadian climates. The quality control verification systems often flags and disqualifies solid precipitation measurements in windy conditions. This is a severe problem for weather forecast verification, especially in winter at high latitudes where the selective quality control systematically eliminates most snow events.

The World Meteorological Organization’s (WMO) Solid Precipitation Inter-Comparison Experiment (SPICE) developed site specific and universal transfer functions for the adjustment of snowfall measurements using data from eight supersites representing different climate conditions. Given the geographical span and climate diversities of Canada, the additional characterization of important regions such as the Canadian Arctic is still required. Further development and testing of climate dependent transfer function is possible using Canadian research supersites equipped with integrated measurement system collecting core meteorological data as well as precipitation observations via several automatic gauge configurations.

The first part of the presentation will include an overview of available precipitation measurement locations, instruments and current developments happening across the ECCC networks. Further opportunities are examined for the use of observations external to the ECCC network, considering the challenges due to different instrumentation and data quality. The second part of the presentation will focus on the difficulty of data processing procedures and transfer function development. The applicability of existing transfer functions for adjusting automated precipitation observations will be evaluated using typical climate conditions characterized with site exposure, wind and temperature mean and extreme values of the Canadian operational network.