FN Archimer Export Format PT J TI Improved correction for non-photochemical quenching of in situ chlorophyll fluorescence based on a synchronous irradiance profile BT AF XING, Xiaogang BRIGGS, Nathan BOSS, Emmanuel CLAUSTRE, Herve AS 1:1;2:2;3:3;4:4; FF 1:;2:;3:;4:; C1 State Ocean Adm, State Key Lab Satellite Ocean Environm Dynam SOED, Inst Oceanog 2, Hangzhou 310012, Zhejiang, Peoples R China. Univ Southampton, Natl Oceanog Ctr Southampton, Southampton SO14 3ZH, Hants, England. Univ Maine, Sch Marine Sci, 706 Aubert Hall, Orono, ME 04469 USA. Sorbonne Univ, CNRS, LOV, F-06230 Villefranche Sur Mer, France. C2 SIO, CHINA UNIV SOUTHAMPTON, UK UNIV MAINE US, USA UNIV PARIS 06, FRANCE IN DOAJ IF 3.561 TC 41 UR https://archimer.ifremer.fr/doc/00640/75204/75335.pdf LA English DT Article CR MD 205 / SOCLIM BO Marion Dufresne AB In situ chlorophyll fluorometers have been used to quantify the distribution of chlorophyll concentration in natural waters for decades. However, chlorophyll fluorescence is depressed during daylight hours due to non-photochemical quenching (NPQ). Corrections attempted to date have provided improvement but still remain unsatisfactory, often over-estimating the expected value. In this study. we examine the relationship between NPQ and instantaneous Photosynthetically Active Radiation (iPAR) using field data from BGC-Argo floats equipped with Chlorophyll-alpha fluorometers and radiometers. This analysis leads to an improved NPQ correction that incorporates both iPAR and mixed layer depth (MLD) and is validated against data collected at sunrise or sunset. The optimal NPQ light threshold is found to be iPAR = 15 mu mol quanta m(-2) S-1, and the proposed methods based on such a light threshold correct the NPQ effect more accurately than others, except in "shallow-mixing" waters (NPQ light threshold depth deeper than MLD). For these waters, an empirical-relationship-based method is proposed for improvement of NPQ correction using an iPAR profile. It is therefore recommended that, for optimal NPQ corrections, profiling floats measuring chlorophyll fluorescence in daytime be equipped with iPAR radiometers. PY 2018 PD SEP SO Optics Express SN 1094-4087 PU Optical Soc Amer VL 26 IS 19 UT 000444705000037 BP 24734 EP 24751 DI 10.1364/OE.26.024734 ID 75204 ER EF