Assessing the impact/adaptation of human activities on/to climate change is a key issue, especially in the tropics that concentrate major anthropogenic dynamics such as deforestation and nearly two-thirds of the planetary rainfall. However, this task is often made tough because human activities such as agricultural dynamics are usually analysed at local or regional scale whereas climate related studies are led at large to global scales due to a lack of reliable data, especially in the tropics. In this article we argue that the increased spatial resolution of remote sensing-based rainfall estimates enables assessing the spatiotemporal variability of rainfall regimes at regional and local scales, thus allowing fine analysis of the interactions with human activities. We processed Tropical Rainfall Measuring Mission (TRMM) 3B42 daily rainfall estimates over the state of Mato Grosso (southern Brazilian Amazon) for the 1998–2012 study period in order to compute rainfall metrics such as annual rainfall and duration, onset and end dates of the rainy season based on the Anomalous Accumulation methodology (at a 0.25° spatial resolution). We then crossed these metrics with agricultural maps (produced at a 250 m spatial resolution) and proved that the adoption of intensive agricultural practices such as double cropping systems is partly the result of a strategy to adapt practices to local climatic conditions. Finally, we discuss how such results raise important issues regarding the sustainability of the agricultural development model in the Southern Amazon.

The connections between intrusions of stratospheric air into the upper troposphere and deep convection in the tropical eastern Pacific are examined using a combination of data analysis, potential vorticity (PV) inversion, and numerical simulations. Analysis of NCEP–NCAR reanalyses and satellite measurements of outgoing longwave radiation during intrusion events shows increased cloudiness, lower static stability, upward motion, and a buildup of convective available potential energy (CAPE) at the leading edge of the intruding tongue of high PV. Potential inversion inversion calculations show that the upper-level PV makes the dominant contribution to the changes in the quantities that characterize convection. This supports the hypothesis that upper-level PV anomalies initiate and support convection by destabilizing the lower troposphere and causing upward motion ahead on the PV tongue. The dominant role of the upper-level PV is confirmed by simulations using the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5). Convection only occurs when the upper-level PV anomaly is present in the simulations, and the relative contribution of the upper-level PV to changes in the quantities that characterize convection is similar to that inferred from the PV inversion calculations.

The evolution and structure of stratospheric intrusions into the upper troposphere (UT) over the northern tropical Pacific is examined in terms of both potential vorticity (PV) and ozone (O3). Analysis of 20 years of NCEP–NCAR reanalysis PV shows that the intrusion events have remarkably similar evolution and structure at 350 K, with all events producing narrow tongues of high PV that have an almost north–south orientation and last around 3 days. Nearly all events extend up into the lower stratosphere, but only for a small percentage is there deep downward penetration. The intrusions explain a large amount of the observed variability in upper tropospheric O3 above Hilo, Hawaii, with large values occurring when a tongue of high PV passes over Hilo and low values when Hilo is just upstream of a high-PV tongue. There is also an increase in total column ozone within the PV tongues, but for most intrusions the increase is relatively small. The relationship between deep convection, as diagnosed by sate... Abstract The evolution and structure of stratospheric intrusions into the upper troposphere (UT) over the northern tropical Pacific is examined in terms of both potential vorticity (PV) and ozone (O3). Analysis of 20 years of NCEP–NCAR reanalysis PV shows that the intrusion events have remarkably similar evolution and structure at 350 K, with all events producing narrow tongues of high PV that have an almost north–south orientation and last around 3 days. Nearly all events extend up into the lower stratosphere, but only for a small percentage is there deep downward penetration. The intrusions explain a large amount of the observed variability in upper tropospheric O3 above Hilo, Hawaii, with large values occurring when a tongue of high PV passes over Hilo and low values when Hilo is just upstream of a high-PV tongue. There is also an increase in total column ozone within the PV tongues, but for most intrusions the increase is relatively small. The relationship between deep convection, as diagnosed by sate...

Satellite-derived estimates of precipitation are essential to compensate for missing rainfall measurements in regions where the homogeneous and continuous monitoring of rainfall remains challenging due to low density rain gauge networks. The Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks—Climate Data Record (PERSIANN-CDR) is a relatively new product (released in 2013) but that contains data since 1983, thus enabling long-term rainfall analysis. In this work, we used three decades (1983–2014) of PERSIANN-CDR daily rainfall data to characterize precipitation patterns in the southern part of the Amazon basin, which has been drastically impacted in recent decades by anthropogenic activities that exacerbate the spatio-temporal variability of rainfall regimes. We computed metrics for the rainy season (onset date, demise date and duration) on a pixel-to-pixel basis for each year in the time series. We identified significant trends toward a shortening of the rainy season in the southern Amazon, mainly linked to earlier demise dates. This work thus contributes to monitoring possible signs of climate change in the region and to assessing uncertainties in rainfall trends and their potential impacts on human activities and natural ecosystems.