In this study, we address two key issues in the hydrological cycle that have remained elusive: 1) to what extent can we expect climate change to affect the transport of moisture? and, in particular, 2) how will the changes in the sources’ intensity (that is, more evaporation) affect the distribution of continental precipitation? This was achieved using a multimodel ensemble that allowed delimiting those oceanic areas where climate change will likely lead to an increase in evaporation (E) minus precipitation (P). Finally, a sophisticated Lagrangian model was used to identify which continental regions will be affected by changes in precipitation (E − P < 0) originating in each oceanic moisture source. We find that in boreal winter, wide sectors of Europe, Asia, Middle East, South America, and southern Africa are affected, but North America emerges as the most affected continental region. In austral winter, the largest changes are confined to northern and Central America.
The influence that the evolution of the ENSO cycle has on the moisture transport from the major oceanic moisture sources is investigated using a sophisticated Lagrangian approach informed by ERA-interim data, together with composites of ENSO phases. When maintaining the sources of moisture defined for the climatological period 1980-2012, the variations in the moisture sinks associated with each of these evaporative sources throughout the ENSO cycle reproduce the known patterns of variations of the large-scale atmospheric and precipitation systems over this cycle. Such variations include those observed in rainfall over the equatorial Pacific, in the major Summer monsoon systems, and in subtropical rainfall. When the areas of the sources were redefined according to the phase of ENSO, most of them remained stationary over the period of interest, nevertheless four of them showed notable differences in terms of their extents, namely the South Pacific and the Coral Sea (Pacific Ocean); the Mexican Caribbean (Atlantic), and the Arabian Sea (Indian).
The clathrate‐I Ba8–xSi46 was manufactured from BaSi2 and α‐Si by high‐pressure high‐temperature synthesis at 5 GPa and 900 °C and by redox reaction from Ba4Li2Si6. The transport properties were measured on specimens from the high‐pressure high‐temperature synthesis. The composition of the Ba8–xSi46 phase [space group Pm$\bar{3}$n, a = 10.3051(1) Å] corresponds to x = 0.8(2) according to the refined lattice parameter, the value determined from full‐profile refinement of powder X‐ray diffraction data amounts to x = 0.73(1), and the chemical analysis results in x = 1.0(1), yielding the average composition Ba7.2(2)Si46. The electrical transport properties of the phase with x = 0.8 were determined in the temperature range 2–300 K using a polycrystalline bulk specimen. The material is a metallic conductor with ρ(300 K) = 3.3 μΩ m and S(300 K) = –6.8 μV K–1. The thermal conductivity shows a relatively large – for an intermetallic clathrate – value of about 8 W·K–1 m–1.
This technical note describes a catalog of moisture sources for two sets of continental climatic regions: one based on regions with similar late 20th century mean climate and similar projected late 21st century precipitation changes, and the other widely used in IPCC assessment reports. By illustrating with one region by classification, the European one was selected and we identify and characterize all the major sources of moisture, and analyze their interannual variability and the role of the three dominant modes of global climate variability, including the El Niño-Southern Oscillation (ENSO) and the Northern and Southern Annular Modes (NAM, SAM). We also estimate the influence of those oceanic regions that will see the greatest increases in evaporation rate in future years.
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