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Apr_Chlorophyll_a_Conc_Trendline.jnl
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32 lines (27 loc) · 2.21 KB
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! 30 January 2025
! This program plots the basin-average line graphs along with its trend-line of February chlorophyll-a concentrations, in the south-east Indian Ocean (0° to 50°S, 80°E to 147°E), averaged in the time-period from August 2002 to December 2023.
! The Globcolour monthly MODIS product of chlorophyll-a concentration data was downloaded from the webpage https://hermes.acri.fr/index.php?class=archive , on 22 January 2025.
! The data of chlorophyll-a concnetration was monthly and in the period from August 2002 to December 2023.
! The data has a spatial resolution of 4 km, and is in the area from (0N to 50S, 80E to 147E).
! The reference for the data are as follows:
! O Reilly, J.E., and 24 Coauthors, 2000: SeaWiFS Postlaunch Calibration and Validation Analyses, Part 3. NASA Tech. Memo. 2000-206892, Vol. 11, S.B. Hooker and E.R. Firestone, Eds., NASA Goddard Space Flight Center. http://oceancolor.gsfc.nasa.gov/cms/reprocessing/r2009/ocv6
! The reference for GSM is as follows:
! Maritorena, S. and Siegel, D.A. 2005. Consistent Merging of Satellite Ocean Colour Data Sets Using a Bio-Optical Model. Remote Sensing of Environment, 94, 4, 429-440.
SET MEMORY/MAX=10000
use Chlorophyll_a_Conc_Globcolour_GSM_00N50S080E147E_200208_202312.nc
LET chl_apr = chl1_mean[x=@ave,Y=@ave, l=9:257:12]
LET p=t[l=1:21]
LET q=chl_apr[l=1:21]
SET GRID q
GO regresst
LET slope_per_year=slope*60*60*24*365.25
LET chlorx=chl_apr[l=1:21@ave]
PLOT/nolab chl_apr[l=1:21]
PLOT/VS/OVER/LINE/COLOUR=2/TITLE="Trendline" p, qhat
LABEL/nouser 4.0 -0.8 0 0 0.15 "April Chlorophyll-a concentration (mg/m^3) and trendline ((mg/m^3)/yr) in the<nl>south-east Indian Ocean (00^oN- 50^oS, 80^oE- 147^oE),<nl>area averaged in the south-east Indian Ocean from August 2002 to December 2023"
LABEL/Nouser -0.8 3 0 90 0.12 "Chlorophyll-a Concentration (mg/m^3)"
LABEL/Nouser 0 6.7 -1 0 0.12 "Average Chlorophyll-a Concentration = `Chlorx, PRECISION=4` mg/m^3"
LABEL/Nouser 0 6.4 -1 0 0.12 "Coefficient of Determination (R^2) = `RSQUARE, PRECISION=4`"
! LABEL/Nouser 0 6.1 -1 0 0.12 "y = `Slope_per_year, PRECISION=4` x + `intercep, PRECISION=4`"
FRAME/File="Chlorophyll_a_conc_area_avg_04_Apr_SEIO.gif"
FRAME/File="Chlorophyll_a_conc_area_avg_04_Apr_SEIO.pdf"