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.

Intensification of the Amazon hydrological cycle over the last two decades

Abstract: The Amazon basin hosts half the planet's remaining moist tropical forests, but they may be threatened in a warming world. Nevertheless, climate model predictions vary from rapid drying to modest wetting. Here we report that the catchment of the world's largest river is experiencing a substantial wetting trend since approximately 1990. This intensification of the hydrological cycle is concentrated overwhelmingly in the wet season driving progressively greater differences in Amazon peak and minimum flows. The onset of the trend coincides with the onset of an upward trend in tropical Atlantic sea surface temperatures (SST). This positive longer-term correlation contrasts with the short-term, negative response of basin-wide precipitation to positive anomalies in tropical North Atlantic SST, which are driven by temporary shifts in the intertropical convergence zone position. We propose that the Amazon precipitation changes since 1990 are instead related to increasing atmospheric water vapor import from the warming tropical Atlantic.

Drought in Central and Southwest Asia: La Niña, the Warm Pool, and Indian Ocean Precipitation.

Abstract: Severe drought over the past three years (1998‐2001), in combination with the effects of protracted sociopolitical disruption, has led to widespread famine affecting over 60 million people in central and southwest (CSW) Asia. Here both a regional and a large-scale mode of climate variability are documented that, together, suggest a possible forcing mechanism for the drought. During the boreal cold season, an inverse relationship exists between precipitation anomalies in the eastern Indian Ocean and CSW Asia. Suppression of precipitation over CSW Asia is consistent with interaction between local synoptic storms and wave energy generated by enhanced tropical rainfall in the eastern Indian Ocean. This regional out-of-phase precipitation relationship is

Greenhouse Gas–induced Climate Change Simulated with the CCC Second-Generation General Circulation Model

Abstract: The Canadian Climate Centre second-generation atmospheric general circulation model coupled to a mixed-layer ocean incorporating thermodynamic sea ice is used to simulate the equilibrium climate response to a doubling of C02. Features of the simulation include the use of higher model resolution than previously for studies of this kind, specification of ocean heat transport for the open ocean and under sea ice, incorporation of information on vegetation and soil type in the treatment of land surface processes, and the inclusion of a parameterization of variable cloud optical properties. The results of the simulation indicate a global annual warming of 3.5°C with enhanced warming found over land and at higher latitudes. Precipitation and evaporation rates increase by about 4%, and cloud cover decreases by 2.2%. Soil moisture decreases over continental Northern Hemisphere land areas in summer. The frozen component of soil moisture decreases and the liquid component increases in association with the ...

Recent decline in precipitation and tree growth in the eastern Mediterranean

Abstract: We present evidence of a recent drying in the eastern Mediterranean, based on weather and tree-ring data for Samos, an island of the eastern Aegean Sea. Rainfall declined rapidly after the late 1970s following trends for the entire Mediterranean and was associated with reduced tree-ring width in Pinus brutia. The most recent decline led to the lowest annual radial stem increment after the last 100 years (as far as records reach). As moisture availability decreased best correlations of tree growth with rainfall were obtained for progressively longer integration periods (1–2 years in moister periods, 5–6 years during the severe dryness of 20th century's last decades), suggesting increasing dependency in deep soil water. Such long-term integration periods of tree-growth responses to precipitation have not been reported before. They may reflect a tree-rooting pattern adapted to cope with even several successive dry years. In late summer 2000, moisture reserves became exhausted, however, and a substantial fraction of low altitude pines died, including some 80-year-old trees, which underlines the exceptional extent this trend had reached. Our findings provide empirical support for Intergovernmental Panel on Climate Change projections derived from global circulation models that the Mediterranean, its eastern basin in particular, should become drier as temperature rises, as was the case in the recent past.

Climate and vegetation controls on the surface water balance: Synthesis of evapotranspiration measured across a global network of flux towers

Abstract: [1] The Budyko framework elegantly reduces the complex spatial patterns of actual evapotranspiration and runoff to a general function of two variables: mean annual precipitation (MAP) and net radiation. While the methodology has first-order skill, departures from a globally averaged curve can be significant and may be usefully attributed to additional controls such as vegetation type. This paper explores the magnitude of such departures as detected from flux tower measurements of ecosystem-scale evapotranspiration, and investigates their attribution to site characteristics (biome, seasonal rainfall distribution, and frozen precipitation). The global synthesis (based on 167 sites with 764 tower-years) shows smooth transition from water-limited to energy-limited control, broadly consistent with catchment-scale relations and explaining 62% of the across site variation in evaporative index (the fraction of MAP consumed by evapotranspiration). Climate and vegetation types act as additional controls, combining to explain an additional 13% of the variation in evaporative index. Warm temperate winter wet sites (Mediterranean) exhibit a reduced evaporative index, 9% lower than the average value expected based on dryness index, implying elevated runoff. Seasonal hydrologic surplus explains a small but significant fraction of variance in departures of evaporative index from that expected for a given dryness index. Surprisingly, grasslands on average have a higher evaporative index than forested landscapes, with 9% more annual precipitation consumed by annual evapotranspiration compared to forests. In sum, the simple framework of supply- or demand-limited evapotranspiration is supported by global FLUXNET observations but climate type and vegetation type are seen to exert sizeable additional controls.