To acquire atmospheric data in support of both the prediction and detection of severe weather and of climate trend and variability research. This serves a broad range of users including researchers, policy makers, and service providers. Main gaps: Long-term, atmospheric monitoring in the North poses a significant challenge both operationally (e.g. in-situ automated snowfall measurements) and financially (charterd flights for maintenance and calibration).Most monitoring in the North is limited to populated areas. Attempts to develop an AMDAR capacity out of First Air and Canadian North fleets failed due to economical and technical difficulties. As demonstrated through impact studies, benefits of AMDAR in the North would be tremendous, however would require acquisition and deployment of specialized sensing packages such as TAMDAR (which includes measurements of relative humidity), development of datalink capacity through satellite communications (e.g. Iridium), and upgrading some aircraft systems when possible, especially the aircraft navigation systems. Network type: Atmospheric observing stations over land and sea composed of: - Surface Weather and Climate Network: o In-situ land stations comprising both Hourly stations and Daily Climate observations - Marine Networks: o Buoys (moored and drifting) o Ships: Automatic Volunteer Observing System - Upper Air Network: o In situ (radiosonde) o In situ Commercial Aircraft (AMDAR)