Trend Analysis Of Precipitation Research Articles

Chemical fluxes in time through forest ecosystems in the UK – Soil response to pollution recovery

Long term trend analysis of bulk precipitation, throughfall and soil solution elemental fluxes from 12 years monitoring at 10 ICP Level II forest sites in the UK reveal coherent national chemical trends indicating recovery from sulphur deposition and acidification. Soil solution pH increased and sulphate and aluminium decreased at most sites. Trends in nitrogen were variable and dependant on its form. Dissolved organic nitrogen increased in bulk precipitation, throughfall and soil solution at most sites. Nitrate in soil solution declined at sites receiving high nitrogen deposition. Increase in soil dissolved organic carbon was detected – a response to pollution recovery, changes in soil temperature and/or increased microbial activity. An increase of sodium and chloride was evident – a possible result of more frequent storm events at exposed sites. The intensive and integrated nature of monitoring enables the relationships between climate/pollutant exposure and chemical/biological response in forestry to be explored.

Application of New Precipitation and Reconstructed Streamflow Products to Streamflow Trend Attribution in Northern Eurasia

Abstract River runoff to the Arctic Ocean has increased over the last century, primarily during the winter and spring and primarily from the major Eurasian rivers. Some recent studies have suggested that the additional runoff is due to increased northward transport of atmospheric moisture (and associated increased precipitation), but other studies show inconsistencies in long-term runoff and precipitation trends, perhaps partly due to biases in the observational datasets. Through trend analysis of precipitation, temperature, and streamflow data, the authors investigate the extent to which Eurasian Arctic river discharge changes are attributable to precipitation and temperature changes as well as to reservoir construction and operation between the years of 1936 and 2000. Two new datasets are applied: a gridded precipitation product, in which the low-frequency variability is constrained to match that of long-term bias-corrected precipitation station data, and a reconstructed streamflow product, in which the effects of reservoirs have been minimized using a physically based reservoir model. It is found that reservoir operations have primarily affected streamflow seasonality, increasing winter discharge and decreasing summer discharge. To understand the influences of climate on streamflow changes, the authors hypothesize three cases that would cause precipitation trends to be inconsistent with streamflow trends: first, for the coldest basins in northeastern Siberia, streamflow should be sensitive to warming primarily as a result of the melting of excess ground ice, and for these basins positive streamflow trends may exceed precipitation trends in magnitude; second, evapotranspiration (ET) in the warmer regions of western Siberia and European Russia is sensitive to warming and increased precipitation, therefore observed precipitation trends may exceed streamflow trends; and third, streamflow from the central Siberian basins should respond to both effects. It is found that, in general, these hypotheses hold true. In the coldest basins, streamflow trends diverged from precipitation trends starting in the 1950s to 1960s, and this divergence accelerated thereafter. In the warmest basins, precipitation trends consistently exceeded streamflow trends, suggesting that increased precipitation contributed to increases in both ET and streamflow. In the central basins, permafrost degradation and ET effects appear to be contributing to long-term streamflow trends in varying degrees for each basin. The results herein suggest that the extent and state of the permafrost underlying a basin is a complicating factor in understanding long-term changes in Eurasian Arctic river discharge.

Spatial and temporal variability of phytoplankton biomass, primary production and community structure in the Pontevedra Ria (NW Iberian Peninsula): oceanographic periods and possible response to environmental changes

The spatial distribution of phytoplankton assemblages, chlorophyll, primary production and physical and chemical parameters were studied in the Pontevedra Ria in Galicia (NW Iberian Peninsula) from October 1997 to October 1998. In addition to the usual oceanographic periods described for the Galician Coast, two other periods were observed: a Prebloom or winter bloom, occurring dur- ing calm, sunny days in winter and a Continental period, related to the allochthonous intrusion of low salinity water from the Mino River in late spring. The phytoplankton bio- mass and production in both periods reached values of up to 145 mgChl-a m i2 and 3.6 gC m i2 day i1 , respectively, which were similar to those found in summer upwelling blooms. Throughout the year, the phytoplankton biomass and primary production gradients along the ria's axis were highly dependent on the balance between upwelling and runoV. When the latter prevailed, increased values were measured toward the inner ria, while the opposite pattern was observed during summer upwelling blooms. According to projections derived from climate models and the analysis of wind patterns, temperature and precipitation trends in the area, a drop in the productivity of the ria would be expected as a result of reduced upwelling intensity in summer and decreasing rainfall in spring. In any case the estuarine part of the ria would be the most seriously aVected.

Climate change and glacier retreat in northern Tien Shan (Kazakhstan/Kyrgyzstan) using remote sensing data

This paper presents an analysis of precipitation and temperature trends and a GIS-supported investigation of the related glacier change in the mountain ridges Zailiyskiy and Kungey Alatau, which represent an important part of the northern Tien Shan. The recent glacier coverage was delineated in a semi-automated way using a TM4/TM5 ratio image of a Landsat ETM Scene from the year 1999 and a merged ASTER/SRTM3-DEM. The extent of these glaciers is compared to that of the glaciers in the Soviet Glacier Inventory [UdSSR, Academica Nauk (1966 to 1983). Katalog Lednikov SSSR (in Russian), Gidrometeoizdat. Leningrad], which represents the situation in study area in approx. 1955. Regionalization of temperature and precipitation as well as solar radiation calculation was conducted in order to determine the climate situation at the glaciers. Trend and correlation analysis for the period from 1879 to 2000 at 16 climate stations showed a temperature increase, which have become pronounced since the 1950s. Another strong increase occurred at the beginning of the 1970s and since around 1980, the temperatures have generally stayed at this high level. The trend coefficient was about 0.8 K/100a for the period 1900 to 2000 and about 2.0 K/100a on average for the second half of the last century. The increase was about two times higher than the global average in northern Tien Shan from 1950 until 2000, where the increase was mainly due to temperature rise in autumn and winter. The increase is less pronounced in the mountainous areas, but still obvious. However, the higher temperature increase at the lower stations, located for the most part in cities or larger settlements, may be due in part to increased urbanization. For precipitation, there was a small increase on average, but no clear trend. On the average, the decrease in glacier extent was more than 32% between 1955 and 1999 in the investigated valleys of Zailiyskiy and Kungey Alatau. The glacier retreat was not homogeneous, but depended strongly on the size, location and climate regime at the glaciers. The area loss of the continental-type glaciers with very predominant summer accumulation, as for those situated in the deeply incised Chon-Kemin valley between Zailiyskiy and Kungey Alatau, was conspicuously less, in parts, than the loss at the more maritime glaciers on the northern slope of Zailiyskiy Alatau. This is consistent with the small increase in summer temperatures. However, under dryer conditions with high solar radiation input, such as with glaciers in the Chon-Aksu valley in Kungey Alatau, the area retreat of the continental-type glaciers can be even more pronounced than that of the more maritime glaciers.

Trend analysis of Icelandic discharge, precipitation and temperature series

This study is a part of a Nordic co-operative research project, Climate and Energy, funded by Nordic Energy Research and the Nordic energy sector. The project has the objective of a comprehensive assessment of the impact of climate change on Nordic renewable energy resources including hydropower, wind power, biofuels and solar energy. In this paper, the long term variability of precipitation, temperature and discharge of Icelandic rivers is analyzed with respect to trends. Trend is tested for two periods: 1941–2002, since the longest Icelandic discharge records reach 60 years back in time, and 1961–2000, so that a larger set of discharge records could be included, as only a few Icelandic discharge records extend more than 40 years back in time. An eventual trend in the time series is analyzed using the Mann–Kendall test. The test is applied to the time series of both annual and seasonal values, and also to the timing and volume of the maximum daily discharge in spring and autumn, respectively. The main conclusions from the study are that, despite significant increase in measured precipitation, discharge in non-glacial rivers has not increased. Meanwhile, spring temperatures have a negative trend and spring floods, therefore, are larger and delayed.

Application of Bayesian Regularized BP Neural Network Model for Trend Analysis, Acidity and Chemical Composition of Precipitation in North Carolina

Bayesian regularized back-propagation neural network (BRBPNN) was developed for trend analysis, acidity and chemical composition of precipitation in North Carolina using precipitation chemistry data in NADP. This study included two BRBPNN application problems: (i) the relationship between precipitation acidity (pH) and other ions (NH4 +, NO3 −, SO4 2−, Ca2+, Mg2+, K+, Cl− and Na+) was performed by BRBPNN and the achieved optimal network structure was 8-15-1. Then the relative importance index, obtained through the sum of square weights between each input neuron and the hidden layer of BRBPNN(8-15-1), indicated that the ions' contribution to the acidity declined in the order of NH4 + > SO4 2− > NO3 −; and (ii) investigations were also carried out using BRBPNN with respect to temporal variation of monthly mean NH4 +, SO4 2− and NO3 − concentrations and their optimal architectures for the 1990–2003 data were 4-6-1, 4-6-1 and 4-4-1, respectively. All the estimated results of the optimal BRBPNNs showed that the relationship between the acidity and other ions or that between NH4 +, SO4 2−, NO3 − concentrations with regard to precipitation amount and time variable was obviously nonlinear, since in contrast to multiple linear regression (MLR), BRBPNN was clearly better with less error in prediction and of higher correlation coefficients. Meanwhile, results also exhibited that BRBPNN was of automated regularization parameter selection capability and may ensure the excellent fitting and robustness. Thus, this study laid the foundation for the application of BRBPNN in the analysis of acid precipitation.

Compatibility analysis of precipitation and runoff trends over the large Siberian watersheds

The consistency of long‐term yearly precipitation and runoff trends over the largest Arctic watersheds (Ob, Yenisei and Lena Rivers) is examined. Three gridded precipitation datasets (Climatic Research Unit, University of Delaware, NCEP) are used for comparative analyses with runoff data collected at basin outlets. The results generally demonstrate inconsistency in long‐term changes of basin precipitation and runoff. The Yenisei River runoff increases significantly, while precipitation data show mostly negative trends. The Ob River does not show any significant trend either in precipitation or runoff. Positive trend in the Lena River runoff is accompanied by a weak precipitation increase; however, the precipitation increase is not strong enough to support the observed runoff change. The inconsistency identified in basin precipitation and runoff trends suggests uncertainty in both the quality of basin precipitation and runoff datasets, as well as the perceived hydrologic factors impacting runoff change.

Trend analysis of precipitation and drought in Basilicata from 1923 to 2000 within a southern Italy context

AbstractSeries of annual, monthly and seasonal precipitation from 50 stations, distributed all over the Basilicata territory (southern Italy), were studied for the period 1923–2000. All the series were checked for homogeneity using MASH v. 1.0.1 software and the time series analysis was performed with the Mann–Kendall nonparametric test in order to detect possible trends. The results show that the annual total rainfall decreased by about 156 mm during the period investigated; the decrease becomes stronger in the last 30 years. There are considerably different trends for the different seasons. In particular, only the winter trend, which is downward, is statistically significant. In this season the total rainfall has decreased by about 133 mm. For this same period the standardized precipitation index (SPI) for multiple time scales of 12, 24 and 48 months has been computed. It appears that periods of drought have been quite frequent starting from 1975, with SPI ranging from about −1 to about −3. Copyright © 2004 Royal Meteorological Society

Analysis of Precipitation Trends in 1990s in the Yangtze River Catchment

依据国家气象局提供的实测月降水和日降水资料,运用Mann-Kendall(M-K)非参数检验法验证了降水趋势,并通过空间插补法,由点扩展到面,分析了1990s长江流域降水变化特征,发现1990s长江流域降水变化以降水在时间和空间分布上的集中度的增加为主要特点:时间上,年降水的增加趋势以冬季1月和夏季6月降水的集中增加为主;一日降水量大于等于50mm的暴雨日数和暴雨量在1990s也有了较明显的增加.空间上,年降水、夏季降水、冬季降水的增加都以中下游区的增加为主,尤其以鄱阳湖水系、洞庭湖水系的降水增加为主.1990s长江流域春季和秋季降水的减少以5月和9月两个汛期月份的降水减少为主,除金沙江水系和洞庭湖水系等少数地区外,流域大部分地区降水呈减少趋势.上述1990s出现的降水趋势明显与近年来全球变暖背景下长江流域各地区不同的温度及水循环变异有关.;Applying with Mann-Kendall statistical method and IDW interpolation method, the precipitation trends in 1990s in the Yangtze River catchment were analysed based on the monthly and daily precipitation data provided by National Meteorology Administration of China. The results show:(1) The precipitation trends in the Yangtze River catchment are characterized by concentration on temporal and spatial distribution. Precipitation increases in January (winter) and in June (summer) contribute most to yearly precipitation increment; days with rainstorm and magnitude of rainstorm are increased evidently in 1990s compared with time period 1951-1990; the yearly, summer and winter precipitation trends are positive in most part of the middle and lower reaches of Yangtze River, especially in Poyang Lake basin and Dongting Lake basin. (2) Precipitation decreases in May and in September contribute most to spring precipitation decrement and autumn precipitation decrement, except for regions in Jinshajiang River basin and Dongting Lake basin; the precipitation in spring and autumn in the whole catchment shows negative trends in 1990s approximately.

Variability and trends of sub-continental scale surface climate in the twentieth century. Part II: AOGCM simulations

This work presents an analysis of simulated temperature and precipitation variability and trends throughout the twentieth century over 22 land regions of sub-continental scale in the HADCM3 and HADCM2 (two realizations) coupled models. Regional temperature biases in the HADCM3 and HADCM2 are mostly in the range of –5 K to +3 K for the seasonal averages and –3 K to +2 K for the annual average. Seasonal precipitation biases are mostly in the range of –50% to 75% of present day precipitation, with a tendency in both models to overpredict cold season precipitation. Except for cold season temperature in mid- and high-latitude Northern Hemisphere regions, the average climatology of the HADCM2 and HADCM3 is of comparable quality despite the lack of an ocean flux adjustment in the HADCM3. Both models show warming trends of magnitude in line with observations, although the observed inter-regional patterns of warming trend are not well reproduced. Measures of temperature and precipitation interannual to interdecadal variability in the models are in general agreement with observations except for Northern Hemisphere summer temperature variability, which is overestimated. The models somewhat underestimate the inter-decadal variations in interannual variability measures observed during the century and overestimate the range of anomalies. Both models tend to overpredict the occurrences of short persistences (1–3 years) and underpredict the occurrence and maximum length of long persistences (greater than three years), which is an indication of a deficiency in the simulation of long-lived anomaly regimes. Compared to observations, the models produce a higher magnitude of temporal anomaly correlation across regions and correlation between temperature and precipitation anomalies for a given region. This suggests that local processes that may be effective in decoupling the observed regional anomalies are not captured well. Overall, the variability measures in the HADCM2 and HADCM3 are of similar quality, indicating that the use of a flux correction in the HADCM2 does not strongly affect the regional variability characteristics of the model.

Living with uncertainty: climate change, river flows and water resource management in Scotland

The recent increased variability of Scotland's hydroclimate poses major problems for water resource managers charged with making informed investment decisions given the likely impact of future climate change. Two strategies are developed in this paper to assist managers faced with this environmental uncertainty. The first involves trend analysis of precipitation and runoff since the 1960s and 1970s viewed against longer-term variability reported from instrumental records. The second strategy is based upon current climate change scenarios coupled with GCMs, and downscaling of precipitation and temperature to provide inputs to rainfall-runoff models. The long-term records of precipitation (back to the 1860s) and runoff (back to the 1930s) reveal the late 1980s and early 1990s as the wettest period on record for the west but not for the east. Over the period 1961–1996 the precipitation gradient has intensified across Scotland: wetter west; relatively dry east. Changes in runoff over the period 1970–1996 are also reported with increases in annual flows at 33 out of 38 stations (significantly at 12 stations) and decreases in low flows at 21 out of 38 stations (significantly at one station). The bulk of these flow increases occurred in the south and west especially in the autumn and spring. In terms of high flows over the period 1970–1996, four out of 44 stations reported a change in magnitude and 15 reported an increase in the frequency of POT events. In terms of future climate change, Hulme and Jenkins (1998) predict annual precipitation increases of 6–16% (Scotland) and 6–14% (Scottish Borders) from the 2020s to the 2080s based on the Hadley Centre model (HadCM2) medium–high scenario. Seasonal changes are concentrated in the autumn (SON) and winter (DJF) with increases as high as 24 and 29% for the autumn by the 2080s. ( Arnell NW, et al. Institute of Hydrology Report No. 107, Wallingford, 1996), using an earlier transient Hadley experiment (IS92a), predict a 5–15% increase in annual runoff across Scotland by the 2050s, locally rising to 25%. Simulation flow duration curves for the 2050s generate Q 95 values up by 5% or less (Rivers Don, Almond and Nith) and Q 5 up by 10–24% (Rivers Don, Almond, Nith and Lyne Water). In terms of water resource planning, these predicted changes should be regarded as first order approximations, as they take no account of natural climatic variability, and could generate different absolute values if other scenarios were used. The predictions are, however, broadly consistent with trends in precipitation and runoff for Scotland since the 1970s. Major issues of concern to water resource managers are identified and commented upon in the light of these predictions.

Trend analysis of monthly precipitation over the iberian peninsula for the period 1921–1995

In this study monthly and annual total precipitation records of the Iberian Peninsula are analyzed for trend. In order to take into account seasonality and serial correlation, the different months of the year are considered separately.The precipitation series were observed at forty meteorological stations scattered all over the Iberian Peninsula. The group of series were selected for their spatial and temporal representativeness. The long common period of seventy-five years (from January 1921 to December 1995) permits a reliable climatic investigation.The Wald and Wolfowitz (1943) test was applied to the series in order to detect serial correlation that could affect the subsequent trend analysis. Due to the long interval of time (one year) between consecutive data, the monthly total precipitation series for the different months showed no persistence. However, the annual total precipitation series showed a positive serial correlation.In order to detect possible trends in precipitation over the Iberian Peninsula, the Mann-Kendall test was applied to the annual and monthly series. This test is non-parametric and thus, has the advantage of being insensitive to the true (unknown) form of the distribution involved.No significant global trend was found in the annual total precipitation series. The only trend observed was a downward trend in twenty-one of the forty series of monthly total precipitation only for the month of March.

A principal component and long-term trend analysis of daily precipitation in Switzerland

Daily precipitation patterns over Switzerland are investigated by rotated and unrotated principal component analysis for the periods 1901–1990 (with 113 continuously operating rain-gauge sites) and 1961–1990 (with 304 sites). Empirical orthogonal functions are utilized to homogenize the precipitation series and to optimally transform the 113 series of the long-term record into a few variables. Several statistically significant linear trends are detected. This includes, in particular, a wintertime increase in precipitation by up to 30 per cent per 100 years in the western and northern parts of Switzerland. This trend is statistically significant at the 90 per cent level. In most parts of southeastern Switzerland, winter precipitation increased as well but by a smaller rate and at a slightly lower statistical significance level. For the period 1961–1990, precipitation amounts increased in most subregions and all seasons with the exception of summer. A statistical model is formulated in order to isolate the contributions to the observed precipitation trends that are related to changes in either the frequency or the precipitation activity of Alpine weather classes. It is demonstrated that the observed precipitation trends cannot be interpreted based upon changing frequencies of weather classes (the observed changes would in fact lead to drier wintertime conditions), but are rather dominated by the tendency of most rain-producing weather types to produce more rain. Some physical mechanisms that could account for this unexpected result are also discussed. © 1997 by the Royal Meteorological Society. Int. J. Climatol., 17: 1333–1356 (1997) (No. of Figs: 9. No. of Tables: 5. No. of

Step-wise analysis of precipitation and river chemistry trends in Atlantic Canada

Monotonic trends in hydrogen (H + ), sulfate (SO 4 -2 )and nitrate (NO 3 - ) were calculated using non-parametric techniques at four Canadian Air and Precipitation Monitoring Network (CAPMoN) sites and six nearby river systems in Atlantic Canada for the period 1983-1991. Over the whole interval, there were increasing nitrate concentrations and deposition trends at three of the four monitoring sites and no trends in SO 4 -2 or H + concentrations and deposition. We found that SO 4 -2 concentrations increased at three of our six river sites, NO 3 - increased at one site and H + decreased at one site. River exports showed no trends in the entire study interval. The series were also analyzed in five year time windows, incremented by six months, to see if changes in trend presence or direction would occur, compared to trend analysis over the entire interval. We show that while trends in river chemistry do not contradict deposition patterns, the changes that occurred were not necessarily in step. We also found that the trends which we measured were the result of short-term changes as opposed to long-term continuous monotonic trends. The time lag between precipitation and chemistry trend changes seemed longer in basins dominated by softwoods than by hardwoods.