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.

Changes in the Extremes of the Climate Simulated by CCC GCM2 under CO2 Doubling

Abstract: Changes due to CO2 doubling in the extremes of the surface climate as simulated by the second-generation circulation model of the Canadian Centre for Climate Modelling and Analysis are studied in two 20-yr equilibrium simulations. Extreme values of screen temperature, precipitation, and near-surface wind in the control climate are compared to those estimated from 17 yr of the NCEP‐NCAR reanalysis data and from some Canadian station data. The extremes of screen temperature are reasonably well reproduced in the control climate. Their changes under CO2 doubling can be connected with other physical changes such as surface albedo changes due to the reduction of snow and sea ice cover as well as a decrease of soil moisture in the warmer world. The signal in the extremes of daily precipitation and near-surface wind speed due to CO 2 doubling is less obvious. The precipitation extremes increase almost everywhere over the globe. The strongest change, over northwest India, is related to the intensification of the summer monsoon in this region in the warmer world. The modest reduction of wind extremes in the Tropics and middle latitudes is consistent with the reduction of the meridional temperature gradient in the 23CO2 climate. The larger wind extremes occur in the areas where sea ice has retreated.

A Lagrangian Analysis of the Atmospheric Branch of the Global Water Cycle. Part I: Method Description, Validation, and Demonstration for the August 2002 Flooding in Central Europe

Abstract: Understanding and quantifying the relationships between evaporation of water in one region, precipitation in another, and the transport processes connecting them, is one of the key problems in hydrometeorology. However, to date few methods exist that are suitable for establishing these relationships. In this paper, a new Lagrangian technique is described that builds on methods that have been developed for investigating source‐receptor relationships for air pollutants. It is based on meteorological analysis data and a particle dispersion model and uses a Lagrangian analog to the Eulerian budget method to diagnose the surface moisture flux. Because of its Lagrangian nature, regions of net evaporation are connected by trajectories with regions of net precipitation, and these trajectories can be used to examine how the two are related. The method is shown to yield estimates for the global distribution of the annual mean surface freshwater flux that are equally accurate as those obtained with the Eulerian budget method. It is then applied in a case study of an extreme precipitation event that occurred in central Europe in August 2002 and led to floodings with return periods of 100 to 300 yr in some river catchments. Again it is shown that the moisture fluxes obtained with the Lagrangian and Eulerian method, respectively, agree well with each other, and both agree well with observed precipitation patterns and shortrange precipitation forecasts. Then the new method is used to determine where the water that became precipitation during the flooding event has evaporated. It is found that in addition to a strong Mediterranean source, much of the water evaporated from land. The strong extra evaporation over land was likely due to a wet spell the weeks before that left soils saturated with water in large parts of Europe and flooded in some smaller regions. It appears that precipitation forecasts suffered from predicting too little evaporation in these regions.

Precipitation fluctuations in the Nepal Himalaya and its vicinity and relationship with some large scale climatological parameters.

Abstract: Precipitation records from 78 stations distributed across Nepal were analysed and all-Nepal (1948–1994) and subregional records (1959–1994) were developed. The all-Nepal and regional precipitation series showed significant variability on annual and decadal time scales. Distinct long-term trends were not found in these precipitation records. The all-Nepal record agrees well with the precipitation records from northern India, while it does not compare well with the all-India precipitation record. The all-Nepal monsoon record is highly correlated with the Southern Oscillation Index (SOI) series. The exceptionally dry year of 1992 recorded in Nepal coincides with the elongated El Nino of 1992–1993 and the Mount Pinatubo eruption. A remarkable cooling in the region covering the Tibetan Plateau also occurred in 1992, suggesting that Pinatubo aerosol played a major role in the drought of that particular year in Nepal. In other years, the correlation between the precipitation record from Nepal and the temperature of the Tibetan Plateau is not significant, while a stronger correlation with temperature over the Indian Ocean and southern India exists. This provides further support for the strong relationship between the El Nino–Southern Oscillation (ENSO) and precipitation fluctuation in Nepal. The correlation is stronger between all-Nepal monsoon precipitation and SOI averaged over seasons following the monsoon compared with seasons preceding the monsoon. Copyright © 2000 Royal Meteorological Society

Afternoon rain more likely over drier soils

Abstract: Analysis of observations on six continents reveals a global preference for afternoon rain to fall on locally drier soils—contrary to the predictions of large-scale climate models, and suggesting that such models may exaggerate the occurrence of droughts. Soil moisture is known to influence precipitation across a range of scales in time and space, and most models suggest that wetter soils promote higher atmospheric moisture content and favour the local development of storms. But this analysis of global precipitation data from a combination of weather satellites shows that — especially in semi-arid regions — afternoon precipitation is more likely over dry soil than over wet soil. The findings suggest that current climate models may be missing fundamental processes regulating convection and land–atmosphere interactions. Land surface properties, such as vegetation cover and soil moisture, influence the partitioning of radiative energy between latent and sensible heat fluxes in daytime hours. During dry periods, soil-water deficit can limit evapotranspiration, leading to warmer and drier conditions in the lower atmosphere1,2. Soil moisture can influence the development of convective storms through such modifications of low-level atmospheric temperature and humidity1,3, which in turn feeds back on soil moisture. Yet there is considerable uncertainty in how soil moisture affects convective storms across the world, owing to a lack of observational evidence and uncertainty in large-scale models4. Here we present a global-scale observational analysis of the coupling between soil moisture and precipitation. We show that across all six continents studied, afternoon rain falls preferentially over soils that are relatively dry compared to the surrounding area. The signal emerges most clearly in the observations over semi-arid regions, where surface fluxes are sensitive to soil moisture, and convective events are frequent. Mechanistically, our results are consistent with enhanced afternoon moist convection driven by increased sensible heat flux over drier soils, and/or mesoscale variability in soil moisture. We find no evidence in our analysis of a positive feedback—that is, a preference for rain over wetter soils—at the spatial scale (50–100 kilometres) studied. In contrast, we find that a positive feedback of soil moisture on simulated precipitation does dominate in six state-of-the-art global weather and climate models—a difference that may contribute to excessive simulated droughts in large-scale models.

Precipitation variability increases in a warmer climate

Abstract: Understanding changes in precipitation variability is essential for a complete explanation of the hydrologic cycle’s response to warming and its impacts. While changes in mean and extreme precipitation have been studied intensively, precipitation variability has received less attention, despite its theoretical and practical importance. Here, we show that precipitation variability in most climate models increases over a majority of global land area in response to warming (66% of land has a robust increase in variability of seasonal-mean precipitation). Comparing recent decades to RCP8.5 projections for the end of the 21st century, we find that in the global, multi-model mean, precipitation variability increases 3–4% K−1 globally, 4–5% K−1 over land and 2–4% K−1 over ocean, and is remarkably robust on a range of timescales from daily to decadal. Precipitation variability increases by at least as much as mean precipitation and less than moisture and extreme precipitation for most models, regions, and timescales. We interpret this as being related to an increase in moisture which is partially mitigated by weakening circulation. We show that changes in observed daily variability in station data are consistent with increased variability.