VicSouth Desert Spring Star Party 2007

Below are portions of MODIS true colour images, centred on the Little Desert Lodge and showing daytime cloud cover during VicSouth 2007. Resolution of these portions is 250 metres per pixel, ie: each image covers a 200x150km rectangle.

The thin vertical black line is the border between SA and Vic (added by the MODIS image processing). The horizontal bullet-shaped patch is the Little Desert National Park. The dark patch near the bottom right corner is the Grampians National Park. The larger blotchy light/dark area in the upper left are the adjoining Big Desert (in Vic) and Ngarkat (in SA) National Parks.

The MODIS instrument flies aboard two satellites, Terra and Aqua, which are in sun-synchronous and nearly polar orbits. During the daytime half of their orbits each satellite images a continuous swath of the Earth passing below it. Terra produces a mid-morning (local time) image, Aqua produces a mid-afternoon image. The MODIS website posts these raw image swathes within a few minutes of receipt. The website also automatically processes these image swathes into standardised, geometrically-corrected views of most of the Earth's landmasses -- including various parts of Australia.

The Thursday afternoon Aqua image

The Friday morning Terra image. After several hours of sunlight, the warm humid air rising from ground level has produced numerous puffy white cumulus clouds.

The Friday afternoon Aqua image. The cumulus clouds are beginning to consolidate but there's not enough moisture to generate huge clouds. Later as the ground (and air) cools with the approaching sunset, the convection sustaining these clouds fails and the clouds evaporate.

The Saturday morning Terra image. Less humidity today so it's taking much longer to generate clouds.

The Saturday afternoon Aqua image

The Sunday morning Terra image

The Sunday afternoon Aqua image. This one was assembled from adjacent image swathes by the MODIS website, so there's a "join" through this image. Resolution is also poorer because the swath edges are much further from the satellite than the swath centre.

The Monday morning Terra image

VicSouth home page : www.vicsouth.com