Variability Of Precipitation Regime Research Articles

Impact of Variability in Precipitation Patterns on the Geochemistry of Pyritic Uranium Tailings Rehabilitated with Saturated Cover Technology

Increasing variability in precipitation patterns is expected to result from climate change in Canada. This effect has the potential to affect the performances of saturated covers in inhibiting acid rock drainage (ARD) and metal leaching (ML) processes. Because ARD and ML may cause the release of deleterious chemical species into the environment, such climate-change-driven impact was investigated using trickle leach columns. The physical, chemical, and mineralogical characteristics of the tailings as well as chemical composition of the leachate were measured before and after the column study. Results from the experiment showed that higher variability in precipitation regimes could enhance leaching of uranium. Leaching ranged from 67.1 to 90.1% of the total amount of U, with greater values associated with higher variability in precipitation patterns. Lower water levels and prolonged drought periods led to higher oxygen fluxes to the U tailings and dissolution of carbonate-bearing minerals. The release of carbonates could have enhanced uranium leaching through the formation of stable uranium-carbonate complexes in solution. Overall, this study shows that water level variation caused by varying precipitation patterns can significantly affect the drainage chemistry of saturated cover systems for which the level fluctuates freely near the tailings–cover interface.

Variability of Precipitation regime in Ladakh region of India from 1901-2000

Ladakh region being a high elevation cold desert of India is marked by extreme aridity with acute moisture deficit throughout the year. Annual precipitation is extremely low due to rain shadow effect caused by Karakoram ranges on one side, mighty Greater Himalayas and Zanskar ranges on the other side. The study of precipitation variability is extremely important for a region like Ladakh, in which the lifestyle of inhabitants, agriculture, live stock rearing and water resources are dependent on the nature and magnitude of precipitation. Despite experiencing low precipitation, extremely low temperature enables Ladakh to contain some of the largest alpine glaciers in the world. These glaciers feed a number of river systems including Indus being the largest and the most important. The precipitation regime however has shown a changing trend over the period of time. In this backdrop, the present study attempts to analyze, core summer and core winter trends to ascertain the temporal variability in the precipitation regime from 1901-2000. Mann-Kendall test (non-parametric test) has been used to analyze the significance levels. Results for summer season show non-significant results with a test statistic of -1.102 with decrease of the order of 0.127 mm per year while for winter season Mann-Kendall test shows a rise of 0.04 mm per year showing significant trend with test statistic of 1.92 at 0.10 significance levels. The results are indicative of decreasing precipitation during summers and increasing precipitation off late during winters which will have a profound impact on the glacial environment of Ladakh region.

Snowmelt and the hydrological interaction of forest-grassland ecosystems in Central Yakutia, eastern Siberia

In the last two decades the major focus of study in forest water and carbon balances in eastern Siberia has been on the effect of rain during the growing season. Little attention has been paid to the contribution of snowmelt water. The results of the present study indicate that weather conditions during the snowmelt period as well as the soil moisture conditions carried from the previous year's growing season strongly determined the water availability for the forest ecosystem at the beginning of the next growing season. In the forest–grassland intermingled ecosystem of lowland Central Yakutia, gradual snowmelt water flow from the forest into the adjacent grassland depressions increased when soil moisture was high and air temperature was low, whereas low soil moisture and high air temperatures accelerated soil thawing and consequently snowmelt water infiltration into the forest soil. We found that snow depth did not determine the volume of snowmelt water moving to the grassland depression since the thermokarst lake water level in the adjacent grassland was about 25 cm lower in 2005 than in May 2006, even though maximum snow depth reached 57 cm and 43 cm in the winter of 2004–05 and 2005–06, respectively. The contribution of snowmelt water to forest growth as well as the flow of water from the forest to the grasslands showed a strong annual variability. We conclude that warmer springs and high variability in precipitation regimes as a result of climate change will result in more snowmelt water infiltration into the forest soil when the previous year's precipitation is low while more snowmelt water will flow into the thermokarst lake when the previous year's precipitation is high. Copyright © 2015 John Wiley & Sons, Ltd.

Seasonal precipitation trends in the Mediterranean Iberian Peninsula in second half of 20th century

AbstractThis is a study of the changes in annual and seasonal precipitation amounts and variability, during the period 1951–2000, using MOPREDAMES. This dataset includes 1113 complete and homogeneous monthly precipitation time series from the Mediterranean Iberian Peninsula (IP), and corresponds to the five official Spanish hydrological divisions which drain into the Mediterranean Sea. The time series of annual and seasonal precipitation were used to test for trends. The absolute value of the anomaly time series was also tested for trends to identify changes in interannual variability of precipitation. The significance of these changes was assessed using the non‐parametric Spearman rank test. The intensities of observed changes, both on mean values and variability, were estimated by using linear regression techniques. Finally, we analysed the area affected by different trends by using raster maps and spatial statistics, in addition to calculating the global balances for the five hydrological divisions. We detected high variability in precipitation regimes and conditions in the study area; nevertheless, a decrease in seasonal and annual precipitation has predominated in the east of the IP during the second half of the 20th century. On an annual scale, precipitation has diminished over 90.1% of the study area. Additionally, a high percentage of the territory was affected by diminishing precipitation at a seasonal level: 85% (of territory) in summer, 82% in spring, 64% during winter and 61% in autumn. Taking the study area as a whole, seasonal precipitation decreases are ranked as follows: summer (−22.5%), spring (−19.3%), winter (−7.3%), and autumn (−5.2%), with a decrease in the value of the global mean annual precipitation − 12.4%. We also detected an increase of precipitation variability in winter (+23.5%) and summer (+11.4%), and a decrease in autumn and spring (−14.9 and − 16.8%, respectively) with a global mean value of + 7.8%. Copyright © 2008 Royal Meteorological Society

Coupled vegetation‐precipitation variability observed from satellite and climate records

Variability in precipitation regimes at seasonal and longer time scales strongly influences ecosystem dynamics in arid and semi‐arid regions. In this paper, we use time series of global precipitation and satellite normalized difference vegetation index (NDVI) data to analyze joint spatial and temporal variability between terrestrial ecosystems and precipitation regimes. Accumulated monthly rainfall anomalies are quantified using a standardized precipitation index (SPI), which provides a better measure of ecologically significant precipitation excess or deficit at growing season time scales relative to monthly precipitation data. Results from canonical correlation analysis reveal geographically extensive patterns of joint NDVI‐SPI variability suggestive of strong climate‐biosphere coupling. Further, leading modes of covariability are shown to be related to large‐scale ocean‐atmosphere circulation anomalies. These results illustrate the global extent and sensitivity of ecosystems susceptible to climate change‐induced perturbations in precipitation regimes.