Mobile version

Raindrops keep falling on the sea

Image of the Month - March 2000

Rain rate (in mm per hour, black curve) derived from analysis of Topex radar waveforms at 13.6 GHz (Ku-band) reflected by the surface, overlaid on a brightness temperature map (showing SSM/I measurements, in degrees Kelvin) of tropical cyclone Elsie. Rainfall is heaviest in the branches of the cyclone, whereas all is calm at its center (measurements were acquired by the two satellites about one hour and 30 minutes apart). (Credits Ifremer)

The Topex altimeters, and Poseidon-2 in the near future, operate at two frequencies (13.6 GHz and 5.3 GHz). They first measure electron content in the atmosphere. We can use these measurements to study rainfall by exploiting the fact that one of the altimeter frequencies is more sensitive to liquid water. Rain attenuates the return signal received by the altimeter, and because this attenuation increases with signal frequency we can compare measurements acquired at the two frequencies and analyze Topex radar waveforms reflected by the surface to calculate the rain rate and size of rainfall cells.
This information is very useful for correcting altimetry data and for weather forecasting-indeed, rainfall gages are pretty hard to come by in mid-ocean!

EnglishFrançaisEspañol
Rss feedsContactSitemapPartnersFAQGlossaryLexiconMobile
You must enable cookies in your browser preferences to save the modifications
You are using an older version of Internet Explorer, please update to take full advantage of Aviso+ features

Customize the home page

View all widgets
Reduce display
Public profile
User profile

Select/Deselect widgets

Discover AVISO+

Customizable home, reading tools, products search guide, etc.. Discover step by step the features of the new site AVISO+.

Customizable homepage

The new home page is composed of blocks called "widgets".

Rearrange the blocks with a "Click & Drop".

Hide a widget with the cross at the top right. Reset or add a widget with the "wrench" icon. The "User" and "Public" profiles offer a predefined organization.

All the modifications are automatically saved as cookies on your machine so as to enable you to have your own specific AVISO+.

Reading tools

Ease your reading by choosing the page background colour (black/white) and/or by modifying the font size.

Browsing menu and breadcrum trail

To ease your browsing through AVISO+, you can use at any time the main banner items with the interactive submenus or use the browsing menu on the left side of the screen (it is open by default). For more readiness of the page contents, you can fold and unfold the browsing menu by clicking on the tab. At any time you can know where you are thanks to the browsing menu or the breadcrum at the top of the page.

Products search guide

The first submenu of the "Data" banner item leads you to a new search form enabling you to find quickier the product that suits your needs. The list of results is updated according to your selection criteria.

AVISO+ Multimedia

The first submenu of the "Multimedia" banner item leads you to AVISO+ collections of images and videos linked to altimetry and its applications. Have a nice visit!