SPIRITS tips JRC IES MARS Unit, Ispra (VA) Italy

Recommendations With 1000s of files, it is easy to get quickly lost: create a directory structure to archive the various files so as to be able to find them quickly (rainfall and NDVI images for each year/dekad, long term stats of rainfall and NDVI, abs, rel, standardized anomalies of rainfall and NDVI, map templates called QL, graph templates called charts, PNG images for reports, tasks, scenario files, vectors, Reference data such as land cover masks and admin regions masks for each sensor or image time series Save your scenarios and tasks (i.e. the parameters used) so as to be able to re-run them and find back what you did to create an output in the future; save also QL and graphs templates (.qnq and.cnc files) so as to reuse them (need to update title and colour scale) Pay attention to spelling, spelling and also spelling of input files (95% of beginners’mistakes) Understand the coding of real values of rainfall, temperature, NDVI, relative anomalies… coded as Digital Numbers -> see next slides

How to go from DN to real value Real value: rain (mm), NDVI (-), abs diff of rain (mm), relative diff of rain or NDVI (%), std_difference of rain or NDVI (nb of std dev), Temperature (deg C) DN: a number between 0 and 255 if byte image, 0 and 2^16 – 1 if unsigned integer… Value (unit) = DN* slope + intercept

Example: value = slope*DN + intercept eMODIS: values = {NDVI, -, 1, 200, 92, 190, -1, 0.01} NDVI = 0.01*DN -1 If DN = 1, NDVI = If DN = 200, NDVI = 1 Spot VGT/ProbaV: values = {NDVI-toc, -, 0, 250, 10, 250, -0.08, 0.004} If DN = 0, NDVI = If DN = 250, NDVI = 250*0.004 – 0.08 = 1 – 0.08 = 0.92

Example: value = slope*DN + intercept Chirps: values = {rainfall, mm, 0, 10000, 0, , 0, 1} Rainfall (mm) = 1*DN – 0 = DN Chirps absolute anomaly (as computed by my scenario – remember I gave min and max values) : values = {ADha[rainfall], mm, 0, 250, 117, 141, -100, 0.8} If DN = 0, abs anom (mm) = 0.8 *DN – 100 = -100 mm If DN = 250, abs anom = 0.8*250 – 100 = 100 mm Chirps relative anomaly values = {RDha[rainfall], -, 0, 250, 42, 250, -1.25, 0.01} If DN = 0, rel anom (-) = that is -125% If DN = 250, abs anom = 1.25 that is 125%

Example: value = slope*DN + intercept Chirps: values = {rainfall, mm, 0, 10000, 0, , 0, 1} Rainfall (mm) = 1*DN – 0 = DN Chirps standardized anomaly (abs anom in number of std dev): values = {SDh[rainfall], -, 0, 250, 0, 250, -2.5, 0.02} If DN = 0, std anom () = -2.5 (rain at -2.5 std dev from the mean) If DN = 250, std anom = 2.5 Tamsat rainfall values = {rainfall, mm, 0, 2000, 0, 92, 0, 1} If DN = 0, rainfall (mm) = 0 If DN = 2000, rainfall (mm) = 2000

Example: value = slope*DN + intercept eMODIS standardized anomaly (abs anom in number of std dev): values = {SDh[NDVI], -, 0, 250, 0, 250, -2.5, 0.02} If DN = 0, std anom () = -2.5 (rain at -2.5 std dev from the mean) If DN = 250, std anom = 2.5

Long term statistics Spirits uses the same naming convention for the LT stats as for the images of the time series, i.e. same prefix (e.g. eMODIS_amha_) same date convention (YYTT or YYYYMMDD…), same suffix But special reserved years (see Spirits manual) : – 1962 for the average – 1963 for the std deviation – 1950 for the minimum – 1960 for the maximum – 1955 for the median… It is a good idea to store these LTA images in a separate directory (e.g. HIS for historical stats)

Where to find Spirits files (in envi format) JRC Spirits website (google “JRC spirits”) : ttp://spirits.jrc.ec.europa.eu/ttp://spirits.jrc.ec.europa.eu/ Go to to find: Vegetation indices eMODIS (E Africa, 70 Mb/dekad, then need to extract ROI); NB: last 3 dekads (eaYYTTi_m) are temporary smoothed NDVI files In the future, will put back VGT/ProbaV archive Tamsat rainfall (whole Africa, <1Mb/file) ECMWF gridded meteo data (0.25 deg resol, 50kb/file) from – HRES (operational) model from 01/2008 to now – ERA Interim model from 01/1989 – 12/2014 (for computing LTA) CHIRPS rainfall in the near future Contact JRC in case of doubt

10 Days data (Chirps, NDVI...) Quicklook template Quicklook series Long term average Quicklook template Quicklook series Anomaly images Quicklook template Quicklook series Map production flow chart