SMOS – The Science Perspective

Matthias DruschHamburg, Germany30/10/2009

1. What will be observed? – Geophysical parameters and accuracies.

2. What is the measurement principle? – Passive microwave radiative transfer.

3. What is the measurement technique? – Interferometry.

4. Why are soil moisture and ocean salinity important? – Turbulent surface – atmosphere exchange processes.

5. What are the main challenges?– Horizontal and vertical scaling.

6. How will the data be used? – Applications, multi-scale analyses, data fusion and data

assimilation.

OVERVIEW

WHAT WILL BE OBSERVED?

Surface Soil Moisture

SMOS observed range

10 % 20 % 30 % 40 % 50 %

4 % accuracy(at 50 50 km2)

Ocean Salinity

~ 0 % 3 % 3.5 % 33 %

0.01 – 0.02 % accuracy(monthly mean at 200 200 km2)

WHAT IS THE MEASUREMENT PRINCIPLE?

• SMOS measures radiation

21 c

mL-

band

Soil

Moi

stur

e

Radiationcold warm

wet

dry

theoretical relationshipatmospheresoil and roughnessvegetation

/ roughness and waves/ foam

Oce

an S

alin

ity

salty

fresh

WHAT IS THE MEASUREMENT TECHNIQUE?

• L-band (21 cm) wavelength required to obtain high soil moisture sensitivity, large penetration depth and low sensitivity to atmosphere and vegetation.• Long wavelength requires big antenna to obtain acceptable spatial resolution. • Big antennas are difficult to operate in space Interferometry!• SMOS will measure phase differences between electromagnetic waves detected at two or more receivers, which are a known distance apart.• Cross correlation of observations from all possible combinations of receiver pairs provide a two dimensional image.

Image courtesy of NRAO/AUI and NRAO

WHY ARE SOIL MOISTURE AND OCEAN SALINITY IMPORTANT?

Soil Moisture …

… is one key variable describing the water and heat exchange between the land surface and the atmosphere.

Bureau of Meteorology

Ocean Salinity …

… and water temperature control the density of sea water and drive the global three-dimensional ocean circulation pattern.… is closely related to the net of evaporation minus precipitation and allows to estimate the heat exchange between the ocean and the atmosphere.

WHAT ARE THE MAIN CHALLENGES?

• SMOS observations are “snapshots” in space and time providing information on the surface layer

NASAECMWF

• Additional data and models have to be used to: - obtain information on the ocean mixed layer - obtain information on the root zone - generate global maps of soil moisture and ocean salinity - validate SMOS geophysical products - use the data in forecast systems

HOW WILL THE DATA BE USED?

predictive model forecast=+Forecast System

initial (current) conditions

hydrology floods, river runoffoceanography ocean currents, ship

routing, ice damage, storm surge

numericalweatherprediction

weather forecast, droughts, precipitation, heat waves

agriculture &water management

crop yield forecasts,water availability

climate climate changetime

THANK YOU

Matthias DruschLand Surfaces Principal ScientistESTEC, The NetherlandsMatthias.Drusch@esa.int