Studies on the diurnal cycle of rainfall and its variations during the TRMM-LBA and Wet AMC.LBA campaigns during Austral Summer 1999

ABSTRACT:

The diurnal cycle of rainfall and convective development, as well as their variations during significant weather events have been studied based on the December 1998-March 1999 high resolution rainfall data. These observations were taken from a network of 40 raingauges. The data have been integrated on 5 minutes interval. The December 1998-March 1999 austral summer campaigns in Rondonia, southwestern

Amazonia. This network was part of a 30 NASA TRMM and 10 LBA tipping buckets, that were part of the TRMM-LBA (or TRMM-Brazil) campaign planned by NASA and was parallel to the Brazilian Atmospheric Mesoscale Campaign (WET AMC-LBA), being both integral part of the Large Scale Biosphere Atmosphere experiment ion Amazonia (LBA). They were ordered on 4 clusters.

Preliminary results indicate that on the region, the maximum of rainfall occurred between 15 and 20 LST, while there are indications of night maximum between 21 and 04 LST during some weather events like squall lines and thunderstorms that developed at night, and that moved from northwest to southwest. The amount of rainfall tend to be larger at the late afternoon early night maximum. Several dry days were observed during December 1998, while the rainy season apparently started by late December 1998. Climatically, the mid-summer drought (or veranicos) are detected during February-March on the region, while is detected earlier (January-February) during La Nina, which was the case of 1999. The location of the veranicos tend to show larger variability (December-March) during the summers of El Nino.