  We propose a new measure based on drought period length to assess the
temporal difference between the recent two severe droughts of 2005 and 2010 in
the Amazonia. The sensitivity of the measure is demonstrated by disclosing the
distinct spatial responding mechanisms of the Northeastern and Southwestern
Amazon (NA, SA) to the surrounding sea surface temperature (SST) variabilities.
The Pacific and Atlantic oceans have different roles on the precipitation
patterns in Amazonia. More specifically, the very dry periods in the NA are
influenced by El Ni\~no events, while the very dry periods in the SA are
affected by the anomalously warming of the SST in the North Atlantic. We show
convincingly that the drought 2005 hit SA, which is caused by the North
Atlantic only. There are two phases in the drought 2010: (i) it was started in
the NA in August 2009 affected by the El Ni\~no event, and (ii) later shifted
the center of action to SA resulted from anomalously high SST in North
Atlantic, which further intensifies the impacts on the spatial coverage.
