PopularSummaryDeforestationis rapidly increasingin Amazonia.If deforestationcontinuesat the current rate,mostof the Amazoniantropical forestswould disappear in lessthan 100years.One questionthat arisesis whether large-scaledeforestationin Amazonia might affect the regional climate. Early modeling studiesconcludedthat widespreaddeforestationof Amazoniawould lead to decreased rainfall. More realistic and sophisticatedmesoscale modelsshowthatdeforestationcancreatelocalizedcirculationswith rising motionsover the deforested areas. The potentialimpactof thesecirculationson cloudinessandrainfall is the subjectof this paper.We analyzegeosynchronous (GOES) infrared satellite data with respectto cloudiness,andanalyzepassivemicrowavedatafrom sensorsaboardthe Tropical Rainfall MeasuringMission satellitewith respectto rainfall. We concludethat in the dry-season(August)whentheeffectsof the surfacearenot overwhelmedby largescaleweatherdisturbances, the occurrenceof cloudinessandrainfall increaseover the deforestedandnon-forested(savanna) regions.During the day,the amountof cloudiness shifts towardafternoonhoursin the deforestedandsavannaregions,ascomparedto the forestedregions. Analysis of 14 yearsof monthly estimatesfrom the Special Sensor Microwave/Imagerrevealedthat only in August did rainfall amountsincreaseover the deforested region.Many modeling studieshave concluded that widespreaddeforestationof Amazonia would leadto decreased rainfall. We analyzegeosynchronous infrared satellitedatawith respectpercentcloudiness,and analyzerain estimatesfrom microwavesensorsaboard the Tropical Rainfall MeasuringMission satellite.We concludethat in the dry-season, when the effects of the surface are not overwhelmed by synoptic-scale weather disturbances, deepconvectivecloudiness,aswell asrainfall occurrence, all increaseover the deforested and non-forested (savanna) regions. This is in responseto a local circulation initiated by the differential heating of the region's varying forestation.Analysis of the diurnal cycle of cloudinessrevealsa shift toward afternoonhoursin the deforestedandsavannaregions,comparedto the forestedregions. Analysis of 14 years of datafrom the SpecialSensorMicrowave/Imagerdatarevealedthatonly in Augustdid rainfall amountsincreaseover the deforested region.
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