Abstract:

Monthly Precipitation form the ERA5 reanalysis archive supplied by the European Centre ofr Medium Range Weather Forecasting for 2001 - 2019. The original data is at 0.25 degree resolution and was downscaled by ERA extraction algroithms to 5km.

This is a set of images produced by Temporal Fourier Analysis (TFA) of ERA5 data:

ERA5: Total Precipitation 

The imagery summarises some key environmental indicators, incorporating seasonal dynamics, for whole world
This series of ERA5 data, processed according to Scharlemann et al (2008), has been updated to include imagery from 2001 to 2019. 

Precipitation from the ERA5 reanalysis archive supplied by the European Centre ofr Medium Range Weather Forecasting for 2001 - 2019. Abstract: Precipitation from the ERA5 reanalysis archive supplied by the European Centre for Medium Range Weather Forecasting . for 2001 - 2019 . The original data is at 0.25 degree resolution and wasdownscaled by ERA extraction algroithms. The daily data have been aggregated to dekadal, monthly, and annual datasets to match the outputs produced by NASA from the MODIS imagery temperature and vegetation Index datasets. The resolution was also chosen to match these MODIS datasets.

Process:

Image values were extracted from ERA5 ( Total precipitation) 5 km imagery from 2001 to 2019.  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 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 (WGS84). 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.

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

File names:

The wd at the start of each file name indicates that the image covers Globally and ER refers to  Europe, North Africa, Eurasia in the E4warning  and is in geographic projection. 19 refers to the year timeline of 2001-2019.

The next two characters identify the channel:
20 - Monthly Total Precipitation


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
ERA5  A0, A1, A2, A3, Min, Max, Vr Reflectance values  monthly total precipitation in mm
ALL D1,D2,D3,Da Percentages
ALL E1,E2,E3 Percentages
ALL P1,P2.P3 Months*100. (Jan=100)