Precipitation

About: Precipitation is a research topic. Over the lifetime, 32861 publications have been published within this topic receiving 990496 citations. The topic is also known as: rain & rainfall.

Future climate extreme events in the Mediterranean simulated by a regional climate model: a first approach

Abstract: Within the frame of PRUDENCE (Prediction of Regional scenarios and Uncertainties for Defining EuropeaN Climate change risks and Effects, EVK2-CT2001-00132), 5th Framework European programme project (2002–2005) European research project, two 30-year time-slice simulations with a regional climate model (PROMES-RCM) nested in the Hadley Centre global model have been performed: present-day climate (1961–1990) and one of the IPCC greenhouse gases emission future scenario (A2 IPCC-SRES) for 2071–2100. Model domain is centered in the Mediterranean basin, considered one of the most sensitive areas regarding to global warming and future climate extreme conditions. This study is based on objective indices to describe extreme climate events of maximum and minimum temperature and precipitation. The statistical frequency and persistence of cold spells, heat waves and intense rain days simulated in the current climate run are compared against the ones resulting from future scenario numerical experiment. Description of extreme processes in both intensity and frequency give a different and complementary overview of extreme events changes in future climate conditions for any of the magnitudes analyzed. In fact, a common feature obtained from the results is the absence of correlation between both magnitudes, as much as for temperatures as for precipitation. Results also point to the usefulness of very high-resolution models (RCM) to study extreme events, due to the great spatial variability obtained in any of the variables studied.

Biotic pump of atmospheric moisture as driver of the hydrological cycle on land

Abstract: . In this paper the basic geophysical and ecological principles are jointly analyzed that allow the landmasses of Earth to remain moistened sufficiently for terrestrial life to be possible. 1. Under gravity, land inevitably loses water to the ocean. To keep land moistened, the gravitational water runoff must be continuously compensated by the atmospheric ocean-to-land moisture transport. Using data for five terrestrial transects of the International Geosphere Biosphere Program we show that the mean distance to which air fluxes can transport moisture over non-forested areas, does not exceed several hundred kilometers; precipitation decreases exponentially with distance from the ocean. 2. In contrast, precipitation over extensive natural forests does not depend on the distance from the ocean along several thousand kilometers, as illustrated for the Amazon and Yenisey river basins and Equatorial Africa. This points to the existence of an active biotic pump transporting atmospheric moisture inland from the ocean. 3. Physical principles of the biotic moisture pump are investigated based on the previously unstudied properties of atmospheric water vapor, which can be either in or out of aerostatic equilibrium depending on the lapse rate of air temperature. A novel physical principle is formulated according to which the low-level air moves from areas with weak evaporation to areas with more intensive evaporation. Due to the high leaf area index, natural forests maintain high evaporation fluxes, which support the ascending air motion over the forest and "suck in" moist air from the ocean, which is the essence of the biotic pump of atmospheric moisture. In the result, the gravitational runoff water losses from the optimally moistened forest soil can be fully compensated by the biotically enhanced precipitation at any distance from the ocean. 4. It is discussed how a continent-scale biotic water pump mechanism could be produced by natural selection acting on individual trees. 5. Replacement of the natural forest cover by a low leaf index vegetation leads to an up to tenfold reduction in the mean continental precipitation and runoff, in contrast to the previously available estimates made without accounting for the biotic moisture pump. The analyzed body of evidence testifies that the long-term stability of an intense terrestrial water cycle is unachievable without the recovery of natural, self-sustaining forests on continent-wide areas.

Reconstruction of precipitation variation from tree rings in recent 1000 years in Delingha, Qinghai

Abstract: Using seven well-replicated Qilian juniper (Sabina przewalskii Kom.) ring-width chronologies developed at Zongwulong and Shalike Mts. in the northeastern part of the Qaidam Basin annual precipitation from previous July to current June in the recent 1000 years was re- constructed for Delingha. The reconstruction can capture 63.1% of precipitation variance and the equation was stable over time. For the reconstructed precipitation, wet periods occurred in AD1520—1633 and 1933—2001, whereas dry intervals in 1429—1519 and 1634—1741. In ad- dition, the magnitude in precipitation variation was lower before 1430 with about 15 mm, but it increased to 30 mm during the period of 1430 to 1850. After 1850, the precipitation variance de- creased again. In contrast to the increase in temperature, a decrease in annual precipitation was evident since the 1990s. The agreement in low-frequency variation between the reconstruction and the glacier accumulation and particulate content in Dunde ice cores during the recent several hundred years suggested that the precipitation reconstructed in this study was rather reliable, and represented a regional signal. This 1000-year reconstruction could benefit our understanding of climatic variation in decadal to century-scale in this region, and provide basic data to climate models and to prediction of future climate in the 21st century.

Long‐Term Soil Water Dynamics in the Shortgrass Steppe

Abstract: To assess the temporal and spatial dynamics of soil water at a shortgrass steppe site in northcentral Colorado, we evaluated the precipitation regime for a 33-yr period and ran a simulation model for this period. Small precipitation events accounted for a large fraction of the total number of events and represented a source of water with small interannual variability. The difference between wet and dry years was related to the occurrence of a few large events. Average daily precipitation was concentrated during the warmest months of the year with a maximum in late spring. Water in the surface soil layers had a short residence time and no seasonal pattern. Intermediate layers reflected the seasonal pattern of precipitation. Maximum soil water availability occurred in the late spring, but this was also the period with the highest interannual variability. The wettest layer was at 4-15 cm of depth. The frequency of wet conditions decreased above this layer because of the strong influence of evaporation and below because recharge was infrequent. No deep percolation events were recorded. During dry years distribution of soil water was very shallow and during wet years wet conditions reached to depths of 120-135 cm. This shallow distribution of soil water matches the distribution of processes and struc- tural elements in the steppe suggesting that there is a cause-effect relationship between them. We speculate that the pattern of water availability interacts with biotic constraints and determines the rate of ecosystem processes. The depth distribution of water in dry and wet years is compared to the root distribution of grasses, shrubs, herbs, and succulents to suggest the response of each group to modal and extreme conditions. Comparison of long- term soil water patterns and traits of the major species allows us to suggest why Bouteloua graci/is is the dominant species in the shortgrass steppe.