MEGHA-TROPIQUES MISSION

The overall area to cover is the tropical belt: 23°N to 23°S, even more with Scarab. In order to obtain interesting inter-annual variations, the duration of the mission is at least 3 years.

An ideal time sampling would be one measurement every 2 hours. However, realistic orbital constraints do not allow this kind of sampling over the whole intertropical band. Then the minimum sampling requirement has been defined as:

at least 3 measurements per day over the whole tropical zone, with possibly more over the zone between 10° to 20° (up to five with the choosen orbit of 20° inclination)
successive observations at less than 2 hours interval during limited periods.

The space resolution is driven by the the size of the systems to observe and the square size used to built statistics. The smallest details deal with the convective precipitation field, with a size of individual convective cell of about 10 km. Thus statistics inside a 1° x 1° grid will include more than 100 pixels. The water vapour has also to be measured at that resolution. For other parameters concerning cloud and radiation, the resolution can be relaxed up to 40 km, which implies 5 to 10 pixels in a 1° x 1° square. Then we can derive the following requirements:

10 km horizontal resolution for convective cells and water vapour
40 km horizontal resolution for radiative budget and other cloud parameters.

Latest Update 09/10/2006