92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Tuesday, 24 January 2012: 9:15 AM
Contribution of Fast-Response Tunable Diode Lasers for Measuring N2o Fluxes From Field to Landscape Using Tower and Aircraft Platforms
Room 342 (New Orleans Convention Center )
Elizabeth Pattey, Agriculture and Agri-Food Canada, Ottawa, ON, Canada; and R. L. Desjardins, D. Dow, W. Smith, B. Grant, J. I. MacPherson, and R. Srinivasan

Since the development of fast-response tunable diode lasers for detecting trace gas fluctuations, considerable progress has been made over the past decades for quantifying greenhouse gas fluxes at the field (i.e., tower-based measurements) and at landscape and regional (i.e., aircraft-based measurements) scales using micrometeorological techniques. Although networks of long-term monitoring micrometeorological tower flux sites expanded a lot in the past two decades (>500) for quantifying carbon dioxide flux, only few sites measure methane and even less measure nitrous oxide fluxes because of various challenges (i.e., expertise, cost, day to day maintenance) involved in doing so. For aircraft, vibration, payload and power consumption are some of the limiting factors. The new generation of analyzers is helping overcoming these difficulties for measuring methane, while for nitrous oxide some roadblocks still exist. We will discuss the main micrometeorological approaches we used to quantify N2O fluxes using tower and aircraft platforms and present key N 2O flux results we obtained in agroecosystems. Emissions of N 2O are mostly produced by the agricultural sector associated with nitrogen application to the fields. They are mainly generated from cultivated soils during microbial denitrification, which takes place under anaerobic conditions that can result from rainfall. In northern countries, the major periods of emissions follows fertilizer applications and snowmelt. We measured N 2O emissions in cultivated field of eastern Canada over 10 years. We found that N 2O emissions following snowmelt varied from 1 to more than 3 kg N 2O -N ha -1, while those following synthetic fertilizer applications ranged between 0.5 and 2.5 kg N 2O -N ha-1 for synthetic N application rates of 40-160 kg N ha-1. The magnitude of N 2O emissions following snowmelt was validated at the regional scale using a relaxed eddy accumulation system mounted on board of an aircraft, which flew georeferenced transects on several occasions. These N 2O flux results largely contributed to the refinement of process-based models (e.g., DNDC, ecosys, etc.) and emission inventories (e.g., IPCC Tier 2 & 3), which are essential for establishing bottom-up regional and national predictions.

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