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.

Spatial patterns of precipitation and topography in the Himalaya

Abstract: Spatial variability in precipitation has received little attention in the study of connections between climate, erosion, and tectonics. However, long-term precipitation patterns show large variations over spatial scales of ~10 km and are strongly controlled by topography. We use precipitation rate estimates from Tropical Rainfall Measuring Mission (TRMM) satellite radar data to approximate annual precipitation over the Himalaya at a spatial resolution of 10 km. The resulting precipitation pattern shows gradients across the range, and from east to west along the range, and fivefold differences between major valleys and their adjacent ridges. Basin-wide average precipitation estimates correlate well with available measured mean runoff for Himalayan rivers. Estimated errors of 15%–50% in TRMM-derived annual precipitation are much smaller than the spatial variability in predicted totals across the study area. A simple model of orographic precipitation predicts a positive relationship between precipitation and two topographically derived factors: the saturation vapor pressure at the surface and this pressure times the slope. This model captures significant features of the pattern of precipitation, including the gradient across the range and the ridge-valley difference, but fails to predict the east-west gradient and the highest totals. Model results indicate that the spatial pattern of precipitation is strongly related to topography and therefore must co-evolve with the topography, and suggest that our model may be useful for investigation of the relationships among the coupled climate-erosion-tectonic system.

Impact of soil moisture-climate feedbacks on CMIP5 projections: First results from the GLACE-CMIP5 experiment

Abstract: The Global Land-Atmosphere Climate Experiment-Coupled Model Intercomparison Project phase 5 (GLACE-CMIP5) is a multimodel experiment investigating the impact of soil moisture-climate feedbacks in CMIP5 projections. We present here first GLACE-CMIP5 results based on five Earth System Models, focusing on impacts of projected changes in regional soil moisture dryness (mostly increases) on late 21st century climate. Projected soil moisture changes substantially impact climate in several regions in both boreal and austral summer. Strong and consistent effects are found on temperature, especially for extremes (about 1-1.5 K for mean temperature and 2-2.5 K for extreme daytime temperature). In the Northern Hemisphere, effects on mean and heavy precipitation are also found in most models, but the results are less consistent than for temperature. A direct scaling between soil moisture-induced changes in evaporative cooling and resulting changes in temperature mean and extremes is found in the simulations. In the Mediterranean region, the projected soil moisture changes affect about 25% of the projected changes in extreme temperature. Key Points GLACE-CMIP5 quantifies soil moisture feedbacks in climate projections Impacts on late 21st century temperature and precipitation mean and extremes Effects of about 25% for temperature extremes in Mediterranean region © 2013 The Authors. Geophysical Research Letters published by Wiley on behalf of the American Geophysical Union.

The Hydrological Cycle over a Wide Range of Climates Simulated with an Idealized GCM

Abstract: A wide range of hydrological cycles and general circulations was simulated with an idealized general circulation model (GCM) by varying the optical thickness of the longwave absorber. While the idealized GCM does not capture the full complexity of the hydrological cycle, the wide range of climates simulated allows the systematic development and testing of theories of how precipitation and moisture transport change as the climate changes. The simulations show that the character of the response of the hydrological cycle to variations in longwave optical thickness differs in different climate regimes. The global-mean precipitation increases linearly with surface temperature for colder climates, but it asymptotically approaches a maximum at higher surface temperatures. The basic features of the precipitation–temperature relation, including the rate of increase in the linear regime, are reproduced in radiative– convective equilibrium simulations. Energy constraints partially account for the precipitation–temperature relation but are not quantitatively accurate. Large-scale condensation is most important in the midlatitude storm tracks, and its behavior is accounted for using a stochastic model of moisture advection and condensation. The precipitation associated with large-scale condensation does not scale with mean specific humidity, partly because the condensation region moves upward and meridionally as the climate warms, and partly because the mean condensation rate depends on isentropic specific humidity gradients, which do not scale with the specific humidity itself. The local water vapor budget relates local precipitation to evaporation and meridional moisture fluxes, whose scaling in the subtropics and extratropics is examined. A delicate balance between opposing changes in evaporation and moisture flux divergence holds in the subtropical dry zones. The extratropical precipitation maximum follows the storm track in warm climates but lies equatorward of the storm track in cold climates.

Modeling δ18O in precipitation over the tropical Americas: 1. Interannual variability and climatic controls

Abstract: [1] We use two atmospheric general circulation models (AGCMs), the ECHAM-4 and the GISS II models, to analyze the interannual variability of δ18O in precipitation over the tropical Americas. Several different simulations with isotopic tracers forced with observed global sea surface temperatures (SST) between 1950 and 1998 reveal the influence of varying temperature, precipitation amount, and moisture source contributions on the predicted δ18O distribution. Observational evidence from climatic (NCEP-NCAR) and sparse stable isotope (IAEA-GNIP) data is used to evaluate model performance. The models capture the essential features of surface climate over the tropical Americas in terms of both their spatial and temporal characteristics. Using a low-resolution model (GISS II), adjusted to provide a more realistic Andean topography, or a higher-resolution model (ECHAM-4 T106) leads to an improved δ18O distribution over the tropical Americas with an altitude effect comparable to observations. Water vapor transport and gradual rainout and increasingly depleted composition of water vapor along its trajectory are correctly simulated in both models, although the ECHAM model appears to underestimate the continentality effect over the Amazon basin. A significant dependence of δ18O on the precipitation amount is apparent in both models, in accordance with observations, while the influence of temperature seems to be less significant in most regions and is accurately reproduced by the ECHAM model only. Over most regions, however, the δ18O signal in precipitation is influenced by a combination of factors, such as precipitation amount, temperature, moisture source variability, and atmospheric circulation changes. Over parts of the tropical Americas, the δ18O signal is therefore also significantly correlated with ENSO because ENSO is an integrator of many factors affecting the δ18O composition of precipitation.

Amplification of the North American “Dust Bowl” drought through human-induced land degradation

Abstract: The "Dust Bowl" drought of the 1930s was highly unusual for North America, deviating from the typical pattern forced by "La Nina" with the maximum drying in the central and northern Plains, warm temperature anomalies across almost the entire continent, and widespread dust storms. General circulation models (GCMs), forced by sea surface temperatures (SSTs) from the 1930s, produce a drought, but one that is centered in southwestern North America and without the warming centered in the middle of the continent. Here, we show that the inclusion of forcing from human land degradation during the period, in addition to the anomalous SSTs, is necessary to reproduce the anomalous features of the Dust Bowl drought. The degradation over the Great Plains is represented in the GCM as a reduction in vegetation cover and the addition of a soil dust aerosol source, both consequences of crop failure. As a result of land surface feedbacks, the simulation of the drought is much improved when the new dust aerosol and vegetation boundary conditions are included. Vegetation reductions explain the high temperature anomaly over the northern U.S., and the dust aerosols intensify the drought and move it northward of the purely ocean-forced drought pattern. When both factors are included in the model simulations, the precipitation and temperature anomalies are of similar magnitude and in a similar location compared with the observations. Human-induced land degradation is likely to have not only contributed to the dust storms of the 1930s but also amplified the drought, and these together turned a modest SST-forced drought into one of the worst environmental disasters the U.S. has experienced.