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.

Freshwater outflow and Subtropical Convergence influence on phytoplankton biomass on the southern Brazilian continental shelf

Abstract: The present study discusses the role of different continental shelf water masses on inorganic nutrient levels and on phytoplankton biomass along the southern Brazilian coast during October 1987 and September 1988. In this productive area, variability of phytoplankton biomass has been related to the seasonal latitudinal displacement of the Subtropical Convergence and to the freshwater outflow of La Plata River and Patos Lagoon. Very distinct precipitation rates, as a consequence of the ENSO (El Nin˜o-Southern Oscillation) cycle, preceding the two sampled periods of this study, allowed a first evaluation of the impact of this event on freshwater outflow and shelf phytoplankton biomass. The amount of chlorophyll in shelf waters was directly related to nutrients supplied by the Coastal Water (i.e. freshwater outflow), Subtropical and Subantarctic Waters. Comparing the results of this study with previous cruises performed in the area, it was found that high chl a concentrations are common features during periods of elevated precipitation rates. Apart from nutrient input by freshwater and the consequent changes in the vertical profiles of density, the extreme precipitation rates are also associated with different wind patterns, which, in turn, control the presence of particular water masses in the euphotic zone. Our results suggest that ENSO events have an important impact on the variability of phytoplankton production, and thus should affect biogeochemical cycles in the southern Brazilian coastal areas.

Seasonal characteristics of the relationship between daily precipitation intensity and surface temperature

Abstract: [1] Past studies have argued that the intensity of extreme precipitation events should increase exponentially with temperature. This argument is based on the principle that the atmospheric moisture holding capacity increases according to the Clausius-Clapeyron equation and on the expectation that precipitation formation should follow accordingly. We test the latter assumption by investigating to what extent a relation with temperature can be observed intraseasonally in present-day climate. For this purpose, we use observed and simulated daily surface temperature and precipitation over Europe. In winter a general increase in precipitation intensity is indeed observed, while in summer we find a decrease in precipitation intensity with increasing temperature. We interpret these findings by making use of model results where we can distinguish separate precipitation types and investigate the moisture content in the atmosphere. In winter, the Clausius-Clapeyron relationship sets a limit to the increase in the large-scale precipitation with increasing temperature. Conversely, in summer the availability of moisture, and not the atmosphere's capacity to hold this moisture, is the dominant factor at the daily timescale. For convective precipitation, we find a peak like structure which is similar for all subregions, independent of the mean temperature, contrary to large-scale precipitation which has a more monotonic dependence on temperature.

Long-term precipitation variability in Morocco and the link to the large-scale circulation in recent and future climates

Abstract: Summary Monthly precipitation data from the Global Historical Climatology Network for 42 stations in Morocco and its vicinity are investigated with respect to baroclinicity, storm track and cyclone activity, moisture transports, North Atlantic Oscillation (NAO) variations, and different circulation types by means of correlation and composite studies. The results are related to a climate change scenario from an ECHAM4=OPYC3 transient greenhouse gas only (GHG) simulation. Precipitation in northwestern Morocco shows a clear link to the baroclinic activity over the North Atlantic during boreal winter (DJF). In large precipitation months the North Atlantic storm track is shifted southward, more westerly and northwesterly circulation situations occur and moisture transports from the Atlantic are enhanced. The occurrence of local cyclones and upper-level troughs is more frequent than in low precipitation months. The negative correlation to the NAO is relatively strong, especially with Gibraltar as a southern pole ( � 0.71). The northward shift of the storm track and eastward shift of the Azores High predicted by the ECHAM model for increasing GHG concentrations would therefore be associated with decreasing precipitation and potentially serious impacts for the future water supply for parts of Morocco. In the region south of the Atlas mountains, moisture transports from the Atlantic along the southern flank of the Atlas Mountains associated with cyclones west of Morocco and the Iberian Peninsula can be identified as a decisive factor for precipitation. Northeastern Morocco and Northwestern Algeria, however, is rather dominated by the influence of cyclones over the Western Mediterranean that are associated with a strong northwesterly moisture transport. As both regions appear to be less dependent on the North Atlantic storm track and more on local processes, a straight forward interpretation of the large-scale changes predicted by the ECHAM4=OPYC3 cannot be done without the application of down-scaling methods in the future.

Seasonally in ENSO‐related precipitation, river discharges, soil moisture, and vegetation index in Colombia

Abstract: An analysis of hydrologic variability in Colombia shows different seasonal effects associated with El Nino/Southern Oscillation (ENSO) phenomenon. Spectral and cross-correlation analyses are developed between climatic indices of the tropical Pacific Ocean and the annual cycle of Colombia's hydrology: precipitation, river flows, soil moisture, and the Normalized Difference Vegetation Index (NDVI). Our findings indicate stronger anomalies during December-February and weaker during March-May. The effects of ENSO are stronger for streamflow than for precipitation, owing to concomitant effects on soil moisture and evapotranspiration. We studied time variability of 10-day average volumetric soil moisture, collected at the tropical Andes of central Colombia at depths of 20 and 40 cm, in coffee growing areas characterized by shading vegetation ("shaded coffee"), forest, and sunlit coffee. The annual and interannual variability of soil moisture are highly intertwined for the period 1997-1999, during strong El Nino and La Nina events. Soil moisture exhibited greater negative anomalies during 1997-1998 El Nino, being strongest during the two dry seasons that normally occur in central Colombia. Soil moisture deficits were more drastic at zones covered by sunlit coffee than at those covered by forest and shaded coffee. Soil moisture responds to wetter than normal precipitation conditions during La Nina 1998 -1999, reaching maximum levels throughout that period. The probability density function of soil moisture records is highly skewed and exhibits different kinds of multimodality depending upon land cover type. NDVI exhibits strong negative anomalies throughout the year during El Ninos, in particular during September-November (year 0) and June-August (year 0). The strong negative relation between NDVI and El Nino has enormous implications for carbon, water, and energy budgets over the region, including the tropical Andes and Amazon River basin.