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By R. Rahmoune and M. Picchiani

Tor Vergata University, Italy

Plot of backscattering coefficients
Soil moisture map obtained from SMOS level 2 data (01-04 July 2011)
Click on the image for larger version.

Soil moisture is a critical element for both global water and energy budgets. Soil moisture controls the redistribution of rainfall into infiltration, surface runoff and evaporation at the Earth's surface. Soil moisture also has a strong effect on surface energy exchange. Thus soil moisture trends may have a great impact on climate change over land. However, estimations of global soil moisture from satellites is not trivial because the effects of roughness and vegetation cover partially reduce the monitoring capability. Therefore it is important to understand how these effects can be managed to set up complete retrieval methodologies. ESA SMOS instrument is performing according to expectations and level 1 brightness temperatures have reached a level of quality that allows the distribution of level 2 soil moisture data as well. SMOS soil moisture retrieval is based on matching measured and modelled (surface emission) brightness temperatures, with the modelled values depending on soil moisture as well as other physical parameters.

IMPORTANT NOTE: This lesson requires Bilko 3.4 from February 2013 or later, as earlier versions of the software can not open and display all data as described in the lesson.


The knowledge of the soil moisture on a global scale and with adequate temporal sampling is required to improve meteorological and climatic predictions. The aim of the ESA SMOS mission is to give scientists the possibility of taking into account the moisture content of a few centimeters of soil as well as sea salinity in the study on the Earth's water cycle. Operating at L Band the SMOS radiometer allows the retrieval of soil moisture despite the soil cover. The lesson will explain the basics of the SMOS retrieval algorithm and will focus on the understanding of Level 2 products. Particular attention will be paid to the most important fields of the datum, concerning its application in an application framework. Finally, examples of soil moisture variation on a mid latitude and a desert scenario will be shown.

Lesson Overview

Aim and objectives

This lesson teaches how to work with the retrieved soil moisture product of the ESA SMOS satellite mission. It gives an overview of the main data product intended for end users: User Data Product (UDP) and explains how to interpret the associated flags.

At the end of the lesson you should be able to

Lesson content

The lesson is divided into 7 sections, which take you through the soil moisture retrieval process from the SMOS data and let you interact with the main products delivered by the mission.

  1. SMOS level 2 UDP data description.
  2. Parameters of the model used to develop the UDP product.
  3. SMOS orbits.
  4. Analysis of retrieved soil moisture and measured brightness temperature.
  5. Seasonal Changes of the soil moisture

Data and tools for this lesson

SMOS Soil Moisture Data

The following Level 2 SMOS soil moisture data are taken over the central area of North America. The data set contains soil moisture retrieval and the brightness temperatures at both polarizations.

Supplementary data

coastline_23305.dat.bz2 world coastline for use with the images.

Bilko tools used in the lesson


Formula documents

Downloading the lesson

The lesson downloads contain everything you need to complete the lesson. This includes the data and tools listed above, and three PDF documents:

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