ASCAT IB VOD product documentation

ASCAT IB VOD was developed by the INRAE-Bordeaux (IB) Remote Sensing Lab (Liu et al., 2021, in review). ASCAT IB VOD is the active C-band vegetation optical depth (C-VOD) retrieved from ASCAT at a resolution of 25 x 25 km. The data was retrieved based on the Water Cloud Model (WCM) coupled with the Ulaby linear model.

Key Features: ASCAT IB VOD is independent of passive microwave observations. The main features of IB VOD are that (i) the ERA5-Land soil moisture (SM) dataset was used as an auxiliary SM dataset in the retrievals, (ii) pixel-based soil model parameters were mapped using Random Forest (RF), and (iii) the vegetation model parameter was calibrated for each day.

Product: ASCAT IB VOD provides 5-years (2015-2019) daily descending (overpass at 09:30 a.m. Local Solar Time) VOD in the NetCDF format with the WGS84 project. The global product is ongoing.

Reference: Liu, X. Wigneron J.-P., et al., ASCAT IB: A radar-based vegetation optical depth retrieved from the ASCAT scatterometer satellite, Remote Sensing of Environment, in review.

Naming convention:

METOPA: The Advanced SCATterometer (ASCAT) were carried by three satellites (MetOp-A, MetOp-B and MetOp-C). METOPA means the backscatter from MetOp-A were used to retrieve the VOD.

ASCAT: Advanced SCATterometer. The name of sensor.

IB: INRAE-Bordeaux. The name of product.

VOD: Vegetation Optical Depth.

M: Morning (Descending).

C: C-band.

DOY: Day of year.

2015001: Tag for the day 4 digit year and 3 digit doy.

Data Format:

All data are saved in ‘netcdf4’ format as 64-bit DOUBLE point numbers in NetCDF format. Each file contains a 720 by 1440 entry map.

lat: latitude (°)

lon: longitude (°)

vod1: original daily vod

vod2: smoothed daily vod with moving window 21 days

vod3: original daily vod with moving outliers


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