M. I. P. de Lima

On the Use of Unmanned Aerial Systems for Environmental Monitoring

Environmental monitoring plays a central role in diagnosing climate and management impacts on natural and agricultural systems; enhancing the understanding of hydrological processes; optimizing the allocation and distribution of water resources; and assessing, forecasting, and even preventing natural disasters. Nowadays, most monitoring and data collection systems are based upon a combination of ground-based measurements, manned airborne sensors, and satellite observations. These data are utilized in describing both small- and large-scale processes, but have spatiotemporal constraints inherent to each respective collection system. Bridging the unique spatial and temporal divides that limit current monitoring platforms is key to improving our understanding of environmental systems. In this context, Unmanned Aerial Systems (UAS) have considerable potential to radically improve environmental monitoring. UAS-mounted sensors offer an extraordinary opportunity to bridge the existing gap between field observations and traditional air- and space-borne remote sensing, by providing high spatial detail over relatively large areas in a cost-effective way and an entirely new capacity for enhanced temporal retrieval. As well as showcasing recent advances in the field, there is also a need to identify and understand the potential limitations of UAS technology. For these platforms to reach their monitoring potential, a wide spectrum of unresolved issues and application-specific challenges require focused community attention. Indeed, to leverage the full potential of UAS-based approaches, sensing technologies, measurement protocols, postprocessing techniques, retrieval algorithms, and evaluation techniques need to be harmonized. The aim of this paper is to provide an overview of the existing research and applications of UAS in natural and agricultural ecosystem monitoring in order to identify future directions, applications, developments, and challenges.

Macroweather precipitation variability up to global and centennial scales

We investigate precipitation variability in the “macroweather” regime – the intermediate regime between the familiar weather and climate regimes – which is associated to time scales from about 10 days to 30–100 years. Macroweather precipitation is characterized by negative fluctuation exponents. This implies – contrary to the weather regime – that fluctuations tend to cancel each other out, they diminish with time scale, this is important for seasonal, annual and decadal forecasts. Aiming at a wide scale range space-time statistical description of macroweather precipitation, we study the scaling of three centennial, global scale precipitation products (one gauge based, one reanalysis based, one satellite based) and systematically compare them over wide ranges of time and space scales. Although these products have very similar temporal statistics, at 5° resolution, they only agree with each other after being averaged over scales of several years. In space, there is less agreement on the statistics but since the data have low resolutions (mostly 5°×5°), the disagreement is only over a small overall range of scales: the monthly data agree fairly well at scales 20°–30° and larger. Moreover, we quantify the outer scale limit of the temporal scaling (20-40 years, depending on the product, on the spatial scale, pixel or global). Overall, results show that precipitation can be modelled with space-time scaling processes. The improved understanding of the space-time macroweather precipitation variability and the limitations of precipitation products provided by this work opens new perspectives to the stochastic modelling and forecasting of macroweather fields. This article is protected by copyright. All rights reserved.

Incorporating the Effect of Moving Storms into Hillslope Hydrology: Results from a Multiple-Slope Soil Flume

The importance of storm movement on surface flow has long been acknowledged at varying scales ranging from headwater scales to drainage basins. Different studies have shown that moving rainstorms substantially affect surface flow hydrographs, although some of the results reported need further discussion. The main objective of this study is to quantify at the hillslope scale the hydrologic response to both non-moving and moving rainstorms in terms of discharge and soil loss. Controlled laboratory experiments were carried out using a multiple-slope soil flume subjected to a movable sprinkling-type rainfall simulator. To simulate moving rainstorms, the rainfall simulator was moved upstream and downstream over the soil surface at different speeds. Results show that the direction of storm movement, especially for very high intensity rainfall events, significantly affected runoff and water erosion with downstream-moving storms, causing higher peak runoff and erosion than did upstream-moving storms.