@article{fdi:010074028,
  title = {{D}ownwelling surface solar irradiance in the tropical {A}tlantic {O}cean : a comparison of re-analyses and satellite-derived data sets to {PIRATA} measurements},
  author = {{T}rolliet, {M}. and {W}alawender, {J}. {P}. and {B}ourl{\`e}s, {B}ernard and {B}oilley, {A}. and {T}rentmann, {J}. and {B}lanc, {P}. and {L}efevre, {M}. and {W}ald, {L}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}his paper assesses the merits and drawbacks of several data sets of solar downwelling radiation received at the horizontal surface of the tropical {A}tlantic {O}cean where the magnitude of this radiation and its spatial and temporal variability are not well known. {T}he data sets are compared to quality-controlled measurements of hourly means of irradiance made at five buoys of the {PIRATA} network for the period 2012-2013. {T}he data sets comprise the re-analyses {MERRA}-2 and {ERAS}, and three satellite-derived data sets: {H}elio{C}lim-3v5, {SARAH}-2 and {CAMS} {R}adiation {S}ervice v2. {I}t was found that the re-analyses {MERRA}-2 and {ERAS} often report cloud-free conditions while the actual conditions are cloudy, yielding an overestimation of the irradiance in such cases; and reciprocally, they report actual cloud-free conditions as cloudy, yielding an underestimation. {T}he re-analyses exhibit more bias in irradiance in cases of medium and high-level clouds than for low-level clouds. {T}hey correlate well with the hourly means of irradiance (as a whole, correlation coefficients greater than 0.85 for {MERRA}-2 and 0.89 for {ERAS}); they correlate very poorly with daily means of irradiance (coefficients of less than 0.48 and 0.59 for {MERRA}2 and {ERAS}, respectively) and with the hourly and daily clearness indices (coefficients of less than 0.53 and 0.46 for {MERRA}-2 and less than 0.63 and 0.59 for {ERAS}). {T}he irradiance pattern at both hourly and daily timescales is spatially distorted by re-analyses, especially for {MERRA}-2. {T}he three satellite-derived data sets exhibit similar performances between them. {T}he correlation coefficients are greater than 0.95 and 0.78 for irradiance and clearness index, respectively, in most cases for hourly values and 0.90 and 0.88, respectively, for daily values. {T}he relative standard deviation of errors is of the order of 15 % for hourly values and 8 % for daily values. {I}t is concluded that these data sets reproduce well the dynamics of the irradiance and clearness index at both hourly and daily timescales. {T}hey exhibit overestimation, with the lowest biases reached by the {CAMS} {R}adiation {S}ervice v2 and ranging between 11 and 37 {W} {M}-2 depending on the buoy. {I}t is suggested that {H}elio{C}lim-3v5 and {CAMS} {R}adiation {S}ervice v2 are suited for reproducing the spatial gradients of the irradiance and reflecting the spatial variability in the irradiance.},
  keywords = {{ATLANTIQUE} ; {ZONE} {TROPICALE}},
  booktitle = {},
  journal = {{O}cean {S}cience},
  volume = {14},
  numero = {5},
  pages = {1021--1056},
  ISSN = {1812-0784},
  year = {2018},
  DOI = {10.5194/os-14-1021-2018},
  URL = {https://www.documentation.ird.fr/hor/fdi:010074028},
}