Factors controlling January�CApril rainfall over southern India and Sri Lanka

Most of the annual rainfall over India occurs during the Southwest (June?CSeptember) and Northeast (October?CDecember) monsoon periods. In March 2008, however, Southern peninsular India and Sri Lanka received the largest rainfall anomaly on record since 1979, with amplitude comparable to summer-monsoon interannual anomalies. This anomalous rainfall appeared to be modulated at intraseasonal timescale by the Madden Julian Oscillation, and was synchronous with a decaying La Ni?a event in the Pacific Ocean. Was this a coincidence or indicative of a teleconnection pattern? In this paper, we explore factors controlling rainfall over southern India and Sri Lanka between January and April, i.e. outside of the southwest and northeast monsoons. This period accounts for 20% of annual precipitation over Sri Lanka and 10% over the southern Indian states of Kerala and Tamil Nadu. Interannual variability is strong (about 40% of the January?CApril climatology). Intraseasonal rainfall anomalies over southern India and Sri Lanka are significantly associated with equatorial eastward propagation, characteristic of the Madden Julian Oscillation. At the interannual timescale, we find a clear connection with El Ni?o-Southern Oscillation (ENSO); with El Ni?os being associated with decreased rainfall (correlation of ?0.46 significant at the 98% level). There is also a significant link with local SST anomalies over the Indian Ocean, and in particular with the inter-hemispheric sea surface temperature (SST) gradient over the Indian Ocean (with colder SST south of the equator being conducive to more rainfall, correlation of 0.55 significant at the 99% level). La Ni?as/cold SSTs south of the equator tend to have a larger impact than El Ni?os. We discuss two possible mechanisms that could explain these statistical relationships: (1) subsidence over southern India remotely forced by Pacific SST anomalies; (2) impact of ENSO-forced regional Indian Ocean SST anomalies on convection. However, the length of the observational record does not allow distinguishing between these two mechanisms in a statistically significant manner.     

Occurrence of the toxic dinoflagellate Ostreopsis cf. ovata in relation with environmental factors in Monaco (NW Mediterranean)

To study environment characteristics favoring the toxic benthic dinoflagellate Ostreopsis cf. ovata, a survey was conducted in Monaco (NW Mediterranean Sea), in summers 2007 and 2008. Epiphytic and planktonic blooms occurred almost simultaneously and a high variation of abundances at low spatial scales was observed. An early and very marked bloom occurred in 2007, compared to a later and less abundant development in 2008. These distinct patterns in bloom timing corresponded with very different hydroclimatic scenarios in 2007 (hot spring and relatively cold summer) and 2008 (standard year compared to the median year profile estimated with data from 1995 to 2008). No clear impacts of summer seawater temperature, rainfall or nutrient concentrations were evident. Strong wind may favor the dispersal of benthic and planktonic cells. Our study suggests that further investigations are needed to examine the potential role of Ostreopsis nutritional mode (i.e. autotrophy vs. mixotrophy).     

Understanding Madden-Julian-Induced sea surface temperature variations in the North Western Australian Basin

The strongest large-scale intraseasonal (30–110 day) sea surface temperature (SST) variations in austral summer in the tropics are found in the eastern Indian Ocean between Australia and Indonesia (North-Western Australian Basin, or NWAB). TMI and Argo observations indicate that the temperature signal (std. ~0.4 °C) is most prominent within the top 20 m. This temperature signal appears as a standing oscillation with a 40–50 day timescale within the NWAB, associated with ~40 Wm^?2 net heat fluxes (primarily shortwave and latent) and ~0.02 Nm^?2 wind stress perturbations. This signal is largely related to the Madden-Julian Oscillation. A slab ocean model with climatological observed mixed-layer depth and an ocean general circulation model both accurately reproduce the observed intraseasonal SST oscillations in the NWAB. Both indicate that most of the intraseasonal SST variations in the NWAB in austral winter are related to surface heat flux forcing, and that intraseasonal SST variations are largest in austral summer because the mixed-layer is shallow (~20 m) and thus more responsive during that season. The general circulation model indicates that entrainment cooling plays little role in intraseasonal SST variations. The larger intraseasonal SST variations in the NWAB as compared to the widely-studied thermocline-ridge of the Indian Ocean region is explained by the larger convective and air-sea heat flux perturbations in the NWAB.     

Ceres,a wet planet: The view after Dawn

Ceres, a nearly 1000-km diameter body located in the Solar System’s main asteroid belt, has been classified under many categories: planet, comet, asteroid, minor planet and, presently, dwarf planet. No matter what the designation, Ceres has experienced major planetary processes. Its evolution has been controlled by water, making it a most unusual, interesting and accessible inner Solar System object that can inform the evolution of outer Solar System moons and other dwarf planets. Early telescopic observations suggested a hydroxylated mineralogy similar to carbonaceous chondrite meteorites and a size and mass indicating a bulk density that implied a water content of 17?27 wt%. Thermodynamic modeling of Ceres’ evolution indicated that thermal aqueous evolution likely occurred. The Dawn Mission produced a huge increase in our understanding of Ceres, confirming but vastly extending the early knowledge. Dawn, carrying multispectral cameras, a visible-infrared imaging spectrometer and a nuclear spectrometer, orbited Ceres between 2015–2018 (after orbiting Vesta) at a number of different altitudes, ultimately reaching 35 km from the surface at periapsis. Observations of almost the entire surface and gravity field mapping revealed multiple geological and internal features attributed to the effects of water. The surface displays cryovolcanic-like and flow structures, exposed phyllosilicates, carbonates, evaporites and water ice. The subsurface shows partial differentiation, decreasing viscosity with depth, and lateral density heterogeneity. Ceres appears to be geologically active today and possesses liquid water/brine pockets or even an extended liquid layer in the interior, confirming an “Ocean World” designation in today’s vernacular.     

Comparison of logistic regressions and snowfall intensity–duration threshold as forecasting tools for direct-action snow avalanches in the Presidential Range,New Hampshire,USA

Built environment, which includes some major investments in Oman, has been designed based on historical data and do not incorporate the climate change effects. This study estimates potential variations of the hourly annual maximum rainfall (AMR) in the future in Salalah, Oman. Of the five climate models, two were selected based on their ability to simulate local rainfall characteristics. A two-stage downscaling–disaggregation approach was applied. In the first stage, daily rainfall projections in 2040–2059 and 2080–2099 periods from MRI-CGCM3 and CNRM-CM5 models based on two Representative Concentration Pathways (RCP8.5 and RCP4.5) were downscaled to the local daily scale using a stochastic downscaling software (LARS-WG5.5). In the second stage, the stochastically downscaled daily rainfall time series were disaggregated using K-nearest neighbour technique into hourly series. The AMRs, extracted from 20 years of projections for four scenarios and two future periods were then fitted with the generalized extreme value distribution to obtain the rainfall intensity–frequency relationship. These results were compared with a similar relationship developed for the AMRs in baseline period. The results show that the reduction in number of wet days and increases in total rainfall will collectively intensify the future rainfall regime. A marked difference between future and historical intensity–frequency relationships was found with greater changes estimated for higher return periods. Furthermore, intensification of rainfall regime was projected to be stronger towards the end of the twenty-first century.     

Comparative agroenvironmental risks of pesticides in different cropping systems: application of the I-Phy indicator

The green revolution laid the foundations of modern agriculture, by using science and technology to produce more from same resources. The pesticides contributed to agricultural output in the last decades; however, their use has resulted in environmental pollution, health problems, soil and water contamination and negative impact on biota. The impacts of agricultural activities to the environment depended on the practices adopted during the production process. Measurement tools to assess the impacts of those practices are necessary to improve agricultural systems and must be evaluated in different ecosystems. Different soils, climates and crops impose many phytosanitary arrangements. This complex network and the fact that most of the indicators and measurement tools are developed for temperate climates makes it difficult to quantify the environmental impacts under subtropical regions. The I-Phy index is a predictive indicator that assesses the risks of pesticide usage in agriculture and identifies as to which practices generate the main environmental impacts of pesticides. The objective of this study was to test the suitability of the I-Phy index for subtropical conditions and, if suitable, compare the pesticide risk between two regions. Five crops were assessed under three different cropping systems: no-tillage, minimal tillage and conventional tillage. The I-Phy index was sensitive in both regions and capable of identifying that no-tillage generally presented risks of environmental pollution slightly lower than the other tillage systems. The results of I-Phy index showed that high environmental vulnerability of the fields and the numerous applications of active ingredients with high risks resulted in high risks of general contamination. The application of I-Phy on these two case studies showed the indicator can be useful as a support tool to farmers, research and extension institutions pursuing management practices with lower impact on the environment.     

The Canadian Meteorological Centre's Atmospheric Transport and Dispersion Modelling Suite

This paper describes the integrated suite of Lagrangian transport and dispersion models in operation at the Canadian Meteorological Centre. These models have been in use for several years and are applied to many types of environmental emergencies covering spatial scales from the very local to the global. The Modèle Lagrangien Courte Distance (MLCD) is used for atmospheric spills of the order of a few kilometres. The Modèle Lagrangien de dispersion de particules d'ordre 1 (MLDP1) is normally used for events affecting areas less than 100?km; Modèle Lagrangien dispersion de particules d'ordre zéro (MLDP0) is used for events of continental and global consequences. The Modèle Lagrangien dispersion de particules mode mixte (MLDPmm) alternates between first-order and zeroth-order depending on criteria specified by the user. The theoretical bases of the models are presented, and the main algorithms used in their implementation are discussed. Modelling of the diffusion processes is based on a stochastic differential equation with the assumption of quasi-stationary Gaussian turbulence, locally homogeneous in the horizontal. The practical aspects of the operational implementation are also described. Using these models, results from simulations of real cases on scales ranging from the very local, to a few kilometres, to regional (approximately 100?km) to continental (approximately 1000?km) and to global (approximately 10,000?km) are compared and validated with available observational data.     

Co-registration and correlation of aerial photographs for ground deformation measurements

We describe and test a procedure to accurately co-register and correlate multi-temporal aerial images. We show that this procedure can be used to measure surface deformation, and explore the performance and limitations of the technique. The algorithms were implemented in a software package, COSI-Corr (available from the Caltech Tectonics Observatory website). The technique is validated on several case examples of co-seismic deformation. First, we measure co-seismic ground deformation due to the 1992, Mw 7.3, Landers, California, earthquake from 1 m resolution aerial photography of the National Aerial Photography Program (United States Geological Survey). The fault ruptures are clearly detected, including small kilometric segments with fault slip as small as a few tens of centimeters. We also obtained similar performance from images of the fault ruptures produced by the 1999 Mw 7.1 Hector Mine, California, earthquake. The measurements are shown to be biased due to the inaccuracy of the Digital Elevation Model, film distortions, scanning artifacts, and ignorance of ground displacements at the location of the tie points used to co-register the multi-temporal images. We show that some of these artifacts can be identified and corrected.     

Dendrogeomorphic reconstruction of past landslide reactivation with seasonal precision: the Bois Noir landslide, southeast French Alps

The purpose of this study was to reconstruct spatiotemporal patterns of past landslide reactivation in a forested area of the Barcelonnette Basin (Bois Noir landslide, Southern French Alps). Analysis of past events was based on tree ring series from 79 heavily affected Mountain pine (Pinus uncinata Mill. ex Mirb) trees growing near or next to the landslide body. Dendrogeomorphic analysis focused on the presence of compression wood and growth reductions, with the first reaction being used for a dating of past reactivations with seasonal precision. A total of 151 growth disturbances were identified in the samples representing eight different stages of reactivation of the landslide body between 1874 and 2008. The spatiotemporal accuracy of the reconstruction is confirmed by historical records from neighboring sites and by aerial photographs. The onset of compression wood formation allows identifying five stages of landslide reactivation during the dormant season or the very beginning of the growing season of trees, i.e., between early October and late May, and three stages toward the end of the growth period. Monthly rainfall data from the HISTALP database demonstrate that the rainfall during four out of the eight reactivations are characterized by summer rainfall totals (July?CAugust) exceeding 200?mm, pointing to the important role of summer rainstorms in the triggering of events at the Bois Noir landslide body.     

Stibnite microstructures as imprints of fault movement

The natural deformation of stibnite in relation to the kinematic history of a regional fault is resolved using microstructural analysis of massive stibnite along the Biards Fault in the Massif Central (France). Stibnite underwent intra-crystalline deformation associated with a strong linear and planar anisotropy. Lepidoblastic textures, undulatory extinction of oriented grains, growth of antimony between these grains, and a colour change of stibnite from white to black, result from dynamic recrystallisation. A range of asymmetric microstructures indicate non-coaxial deformation and a left-lateral sense of shear, related to the movement of the fault zone. The computed displacement corresponds to the geological offsets measured along the fault. We conclude that stibnite has microstructurally recorded the bulk kinematics of its host fault zone.Editorial Handling: F. Tornos