DOI: 10.25326/612
title: NOx - MAP-IO - STATION LEVEL 2

description: The objective of the MAP-IO program is to assess the feasibility of building an atmospheric and marine biology observatory on board the Marion Dufresne. This observatory aims to carry out atmospheric observations at the ocean-atmosphere interface and integrated on the atmospheric column over the entire globe with a focus of particular interest for the study of the Indian and Southern Oceans. The MAP-IO program is positioned in an observatory logic with four main objectives; (i) integration into international atmospheric and oceanic networks by providing high quality data on a region devoid of permanent observation, (ii) validating and calibrating space sensors and numerical weather forecasting models, (iii) monitoring global changes on the Indian and Southern Ocean and (iv) observation of atmospheric and biology phytoplankton variability over the Indian and Southern Oceans.

The Model T200UP provides trace level measurements of NO and NO2 using our Model T200U NOx analyzer combined with a patented high efficiency photolytic converter. Even low temperature molybdenum converters transform other nitrogen-containing compounds such as HNO3, PAN, etc. to a considerable extent. Simultaneous measurements of NO2 performed with molybdenum and photolytic converters have shown significantly different results in the presence of such compounds. In the photolytic process the sample gas passes through a cell where it is exposed to light at a specific wavelength from an LED array. This causes the NO2 to be selectively converted to NO with negligible interference from other gases. Combined with the proven Model T200U, it provides ultra-sensitive performance, with a lower detectable limit of 0.05 ppb or better, and is ideally suited for NCore research sites and the low-level direct NO2 measurements required for roadside monitoring.  Advances in the photolytic converter technology now yields NO2 conversion efficiency that is similar to molybdenum under typical ambient NO2 concentrations, but without the same interferences.
More information on https://www.teledyne-api.com/products/nitrogen-compound-instruments/t200up

MAP-IO takes advantage of the scientific campaigns at sea planned by the FOF by exploring different poorly documented ocean areas and by increasing and completing the observation systems of the programs with additional measurements. The differentiation value of MAP-IO versus conventional scientific programs at sea, and that it relies on the regular rotations of the TAAFs by documenting the atmosphere and the ocean surface state over a wide variability of sea ​​and latitude conditions. These multi-year observations of the Indian and Southern Oceans make it possible to uniquely document the trends, the mechanisms of ocean-atmosphere exchanges and the atmospheric composition on a seasonal and interannual basis.

STATION LEVEL 2 corresponds to nitrogen concentrations validated by the PI at native time resolution.

Variables in the cvs files are follow:
- date: day/month/year hour:minutes:seconds
- CAMPAGNES: names of the campaign
- NO2_conc: Nitrogen dioxyde in ppbv
- NO_conc: Nitrogen oxyde in ppbv
- lat_gaz: latitude of the measurement
- lon_gaz: longitude of the measurement
- filtre_vaisala_d0.55945_w0.5590_ff4: flags indexes using the relative wind to limit protential local contamination by stack pollution; criteria are low wind < 2 m/s (Risk of pollution from the activity on the ship) and angle tailwind (90°-225° or median angle 157° with a deviation of +/- 67) risk of pollution from the ship's stack located aft.
- FLAG_ICOS_CO: flags to supress contamination by local combustion:  concentration peak filtering approach developed by the ICOS IR is added to the dynamic method. The spike detection algorithm is described by El Yazidi etl. (2018).

Flags codes as follow:
Flags have been added as follow: 
- 157: detection limit 
- 456 Invalidated by data originator 
- 559 Unspecified contamination of local influence But valid data 
- 599 Unspecified contamination of local influence 
- 999 Missing measurement, unspecified reason