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.

FIFE Surface Climate and Site-Average Dataset 1987–89

Abstract: This paper analyzes the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment site-average datasets for near-surface meteorology, soil moisture, and temperature; the surface fluxes of radiation, sensible, and latent heat; and the ground heat flux, for the period May 1987‐November 1989. The diurnal and seasonal variation of surface albedo for this grassland site are discussed. The coupling of precipitation, soil moisture, evaporation, pressure height to the lifting condensation level, and equivalent potential temperature (uE) on seasonal and diurnal timescales is also discussed. The 1988 data confirm the authors’ result, shown earlier from the 1987 data that over moist soils increased evapotranspiration lowers afternoon lifting condensation level and increases afternoon uE, suggesting a mechanism for a local positive feedback between soil moisture and precipitation on horizontal scales greater than 200 km. The seasonal cycle of ground heat flux and soil temperature is examined and the authors show that the coupling in the warm months between uE and soil temperature on seasonal scales is similar over land to the coupling found over warm oceans despite very different controls on the surface fluxes. The boundary layer equilibrium over the ocean is contrasted with the diurnal cycle over land, which is soil moisture dependent.

A Investigation of the Sensitivity of Simulated Precipitation to Model Resolution and Its Implications for Climate Studies

Abstract: This paper examines the sensitivity of a regional atmospheric model to horizontal resolution and topographic forcing. The model is run for January and July month-long simulations over the European region at gridpoint spacings ranging from 200 to 50 km and with various topography configurations. Different precipitation parameterizations of complexity and structure similar to those used in present-day climate models are tested. When averaged over the whole continent, the precipitation amounts are more sensitive to gridpoint spacing than to topographic forcing. Topography mostly contributes to spatially redistributing precipitation, and its effect is dominant only over subregions characterized by complex topographical features (e.g., the Alps). Other variables, such as cloudiness, surface energy fluxes, and precipitation intensity distributions are also sensitive to resolution. Finally, simulated precipitation amounts vary with the parameterization scheme used at all resolutions. These results have ...

The Turn of the Century North American Drought: Global Context, Dynamics, and Past Analogs

Abstract: The causes and global context of the North American drought between 1998 and 2004 are examined using atmospheric reanalyses and ensembles of atmosphere model simulations variously forced by global SSTs or tropical Pacific SSTs alone. The drought divides into two distinct time intervals. Between 1998 and 2002 it coincided with a persistent La Nina–like state in the tropical Pacific, a cool tropical troposphere, poleward-shifted jet streams, and, in the zonal mean, eddy-driven descent in midlatitudes. During the winters reduced precipitation over North America in the climate models was sustained by anomalous subsidence and reductions of moisture convergence by the stationary flow and transient eddies. During the summers reductions of evaporation and mean flow moisture convergence drove the precipitation reduction, while transient eddies acted diffusively to oppose this. During these years the North American drought fitted into a global pattern of circulation and hydroclimate anomalies with noticeab...

Deuterium excess in recent Antarctic snow

Abstract: Deuterium excess (d = δD - 8 * δ18O) values in surface snow are presented for central and east Antarctica. The samples are primarily from Soviet, French, and Australian traverses. The d values exhibit a large change going from coastal sites to high-altitude sites on the ice sheet. The d values are relatively constant at 3 to 6‰ from the coast to an altitude of 2500 m, and at higher elevations d increases steadily to values of 16 to 18‰ at Vostok and Plateau Station. The data is modeled as d versus δD using the kinetic Rayleigh model for isotopes in precipitation developed by Jouzel and Merlivat. The model accounts for kinetic fractionation during evaporation into undersaturated air over the ocean and during snow formation in <−10°C clouds where vapor is supersaturated with respect to snow. The overall pattern of d versus δD can be fit well with a supersaturation function which increases linearly with decreasing temperature and which predicts reasonable values of the supersaturation. Vapor originating from 20° to 60°S was tested with different supersaturation functions. The data could only be fit with moisture originating from 30° to 40°S, indicating that these latitudes are the main source of vapor for snow falling in Antarctica. The conclusion of a mid-latitude vapor source for polar snow agrees with the analysis of d and δ18O seasonal cycles in Greenland snow performed by Johnsen and coworkers. The model was also tested with moisture simultaneously originating from all latitudes from 30°S to the Antarctic coast. The addition of up to 20% of moisture evaporated from latitudes south of 50°, and 5% from latitudes south of 60°, is compatible with low d values occasionally observed in snow near the coast. The conclusion of a “local moisture” effect for coastal and near coastal (<2000 m elevation) snowfall supports a similar conclusion by Saigne and Legrand from their analysis of methanesulphonic acid in Antarctic snow. Finally, the effects of changes in the sea surface temperature and changes in oceanic humidity on the d values observed in Antartic snow are greatly modified during the precipitation process. Hence the interpretation of d values in ice cores should be done in the context of a precipitation model.