Atmospheric Measurement Techniques Evaluation of the flux gradient technique for measurement of ozone

• Main Authors: F. Bocquet, D. Helmig, B. A. Van Dam, C. W. Fairall
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2011
• Subjects: Greenland; Lent
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1032.5160; http://www.atmos-meas-tech.net/4/2305/2011/amt-4-2305-2011.pdf

Abstract. A multi-step procedure for investigating ozone surface fluxes over polar snow by the tower gradient method was developed and evaluated. These measurements were then used to obtain five months (April–August 2004) of tur-bulent ozone flux data at the Summit research camp lo-cated in the center of the Greenland ice shield. Turbu-lent fluxes were determined by the gradient method incor-porating tower measurements of (a) ozone gradients mea-sured by commercial ultraviolet absorption analyzers, (b) ambient temperature gradients using aspirated thermocou-ple sensors, and (c) wind speed gradients determined by cup anemometers. All gradient instruments were regularly inter-compared by bringing sensors or inlets to the same measure-ment height. The developed protocol resulted in an uncer-tainty on the order of 0.1 ppbv for 30-min averaged ozone gradients that were used for the ozone flux calculations. This protocol facilitated a lower sensitivity threshold for the ozone flux determination of ∼8 × 10−3µg m−2 s−1, respec-tively∼0.01 cm s−1 for the ozone deposition velocity for typ-ical environmental conditions encountered at Summit. Un-certainty in the 30-min ozone exchange measurements (eval-uated by the Monte Carlo statistical approach) was on the or-der of 10−2 cm s−1. This uncertainty typically accounted to ∼20–100 % of the ozone exchange velocities that were de-termined. These measurements are among the most sensitive Correspondence to: D. Helmig