DOI: 10.25326/616
title: OPC-N3 - 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.

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.

The OPC-N3 has the same dimensions and power/interface as the older OPC-N2, however it now measures from 0.35μm to 40 μm and sorts into 24 size bins.
Additional features of the OPC-N3 include improved aerodynamics with reduction of particle deposition, better small particle detection and extended upper size measurements. As a result, the OPC-N3 can measure from in a broad range of applications, from clean rooms to areas with pollution levels of up to 2,000 μg/m3 (PM2.5), all with the unique feature of being able to measure pollen.
More information on https://www.alphasense.com/products/optical-particle-counter/

Variables in the cvs files are follow:
- datetime: year-month-day hour:minutes:seconds
- CAMPAGNES: names of scientific campaigns
- from 0.41 to 38.50: Number concentration within each bin (dN/dLOG(D), particles.cm-3.µm-1). Bins mean diameter are from 0.41 µm to 38.5 µm. 
-  FlowRate: air flow  in (ml.min-1)
- cm3: Total aerosols number (particles.cm-3) without filtering
- 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: A 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).
- FLAG_ACTRIS_NO: flags to supress contamination by  local NO pollution. Flag is added when NO concentration is up to ??
- FLAG_TOTAL: sum af all flags (filtre_vaisala_d0.55945_w0.5590_ff4+FLAG_ICOS_CO+FLAG_ACTRIS_NO)
- LAT: latitude of the measurement
- LON: longitude of the measurement
- ALT-AMSL: altitude of measurement (in meter above sea layer)

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

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