2012_2014_VIIRS_Fourier Processed_1k_ER

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 processed according to Scharlemann et al (2008), has been updated to include imagery from 2012 to 2014, and was produced to compare with next three years' time series,

Process:

Image values were extracted from VIRRS imagery from 2012 to 2014. 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 output recorded the time series's mean, minimum, and maximum, 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/jou…)
Sea pixels were masked with a VIIRS land/sea layer and the images were projected from sinusoidal to geographic. The  E4warning study region was a subset of global images. Idrisi rasters were converted to GeoTIFF format in order 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. 

 

Projection + EPSG code:
Latitude-Longitude/WGS84 (EPSG: 4326)

File names:

The er at the start of each file name indicates that the image covers the wider Europe and North Africa region included in the E4warning study area and is in geographic projection. 14 refers to the year timeline of 2012-2014.

The next two characters identify the channel:
03 - middle infra-red
07 - daytime land surface temperature
08 - nighttime land surface temperature
14 - NDVI: Normalised Difference Vegetation Index
15 - EVI: Enhanced Vegetation Index

The last two characters of each file name denote the output from Fourier processing:
a0 - mean
mn - minimum
mx - maximum
a1 - amplitude of annual cycle
a2 - amplitude of bi-annual cycle
a3 - amplitude of tri-annual cycle
p1 - phase of annual cycle
p2 - phase of bi-annual cycle
p3 - phase of tri-annual cycle
d1 - variance in annual cycle
d2 - variance in bi-annual cycle
d3 - variance in tri-annual cycle
da - combined variance in annual, bi-annual, and tri-annual cycles
vr - variance in raw data

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