DOI: 10.5281/zenodo.12914014
title: 2012_2020_VIIRS_FourierProcessed_1k_ER

description: Overview:

This is a set of images produced by Temporal Fourier Analysis (TFA) of VIIRS data:

NDVI: Normalised Difference Vegetation Index

EVI: Enhanced Vegetation Index

MIR: Middle Infra-Red

DLST: Day-time Land Surface Temperature

NLST: Night-time Land Surface Temperature

The imagery summarises some key environmental indicators, incorporating seasonal dynamics, for The European and North African extent.This series of VIIRS data has been updated to include imagery from 2012 to 2020. 

 

Abstract:

Image values were extracted from VIRRS imagery from 2012 to 2020. The day and night land temperature came from the 8-day VNP21A2   data whilst the vegetation indices and Middle Infra Red values were extracted from the VNP13A2, 16-day datasets.  Each parameter extract dataset was then processed by a temporal Fourier processing algorithm. A stepwise system of thresholds and interpolations screened erroneous values and bridged gaps in the time series. The smoothed series was sampled at 5-day intervals and transformed into a set of sine curves describing annual, bi-annual, and tri-annual fluctuations. For each of these curves, the Fourier algorithm generated images expressing the amplitude, phase, and variance. Other outputs recorded the mean, minimum, and maximum of the time series, and error measured during the Fourier transform. For a detailed description of the Fourier algorithm and its output, please see the article by Scharlemann et al., 2008 (https://doi.org/10.1371/journal.pone.0001408)Sea pixels were masked with a VIIRS land/sea layer and the images were projected from sinusoidal to geographic. The MOOD study region was a subset of global images. Idrisi rasters were converted to GeoTIFF format to give data users more flexibility.

This new VIIRS Dataset is used as an update and continuation of our MODIS TFA product and can be utilised in the same way. 

File naming scheme:  

The er at the start of each file name indicates that the image covers the wider Europe and North Africa region included in the MOOD study area and is in geographic projection. 20 refers to the year timeline of 2012-2020.The next two characters identify the channel:03 - middle infra-red07 - daytime land surface temperature08 - nighttime land surface temperature14 - NDVI: Normalised Difference Vegetation Index15 - EVI: Enhanced Vegetation IndexThe last two characters of each file name denote the output from Fourier processing:a0 - meanmn - minimummx - maximuma1 - amplitude of annual cyclea2 - amplitude of bi-annual cyclea3 - amplitude of tri-annual cyclep1 - phase of annual cyclep2 - phase of bi-annual cyclep3 - phase of tri-annual cycled1 - variance in annual cycled2 - variance in bi-annual cycled3 - variance in tri-annual cycleda - combined variance in annual, bi-annual, and tri-annual cyclesvr - variance in raw data

Files can be accessed here as well (including Global files). 

 Projection + EPSG code:Latitude-Longitude/WGS84 (EPSG: 4326)Spatial extent:Extent  -32.0000000000000000,10.0000000000000000 : 68.9999999999999574,81.9999999999999716Spatial resolution:0.0083333 deg (approx. 1000 m)  Temporal resolution: 8-day and 16-day  for 2012 to 2020 

Pixel values

Parameter Fourier Variable Image values areMIR (03) A0, A1, A2, A3, Min, Max, Vr Reflectance values * 10000LST (07 day,08 night) A0, A1, A2, A3, Min, Max, Vr (Degrees Centigrade+273)*50NDVI (14) and EVI (15) A0, A1, A2, A3, Index Value * 1000NDVI (14) and EVI (15) A0, Min, Max, Index Value * 1000 + 10000NDVI (14) and EVI (15) VR Value * 10000ALL D1,D2,D3,Da PercentagesALL E1,E2,E3 PercentagesALL P1,P2.P3 Months*100. (Jan=100)

Source:  VIIRS NASA :VNP21A2 and VNP13A2

Software used:Codes for modelling are in Python and C++The software used for map production is ESRI ArcMap 10.8

License: CC-BY-SA 4.0Processed by:ERGO (Environmental Research Group Oxford) https://ergoonline.co.uk/ for the H2020 MOOD project