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Rainfall Pattern and its Effect on Seasonal Variability of Owena River in Ondo State of Nigeria
Akinro O. Akinola,Olawale Olanrewaju
Journal of Engineering and Applied Sciences , 2012,
Abstract: Data on monthly rainfall depths in Owena catchment area were collected and analyzed. The mean monthly rainfall depths were found and these values were plotted against the months of occurrence. Periods of high and low rainfall were found from the graph. The streamflow hydrograph of River Owena was also obtained. A comparison was then made between the graphs. From the study, it was found that seven months experienced intense rainfall while five months of the year experienced rainfall deficit. Similarly, from the hydrograph, it was found that River Owena experienced high flows in seven months and low flows in five months, the months perfectly correlating with the onset and cessation of rainfall in the catchment area. This clearly shows that rainfall is a major contributor to the reservoir build up of River Owena and the major cause for its seasonal stage and discharge variability.
Seasonal and interannual variability in population abundances of the intertidal macroinfauna of Queule river estuary, south-central Chile
JARAMILLO,EDUARDO; CONTRERAS,HERALDO; QUIJóN,PEDRO;
Revista chilena de historia natural , 2001, DOI: 10.4067/S0716-078X2001000200019
Abstract: sediment samples were monthly collected at queule river estuary (ca. 39° s), south-central chile, from october 1990 to april 1992, and from september 1995 to november 1997 to study temporal variability in population abundances of the macroinfauna inhabiting sandy and muddy-sand intertidal substrates. sandy sediments had higher percentages of sand particles and lower percentages of mud particles, biogenic aggregates and total organic matter than muddy-sand sediments. the same macroinfaunal species were found at both sites. that macroinfauna was dominated by polychaetes: the spionid prionospio (minuspio) patagonica augener 1923, the capitellid capitella sp. and the nereid perinereis gualpensis jeldes 1963. other common organisms were the amphipod paracorophium hartamannorum andres 1975 and the small bivalve kingiella chilenica soot-ryen 1959. the highest abundances of the total macroinfauna usually ocurred during summer months (january-february). the most abundant species was p. (m.) patagonica (up to 130-140,000 ind m-2 in the muddy-sand sediments). during some months, this species had significantly higher abundances at the muddy-sand sediments. a similar trend is that shown by p. hartmannorum; i.e., significantly higher abundances at the muddy-sand sediments (up to 75,000 ind m-2). during many months, the population abundances of capitella sp. and k. chilenica were significantly higher at the sandy site. the highest population abundances of capitella sp. were close to 37,800 ind m-2 (february 1991 and february 1996), while the maximum values for k. chilenica ranged from 13,000 to 14,000 ind m-2 (february 1991 and november 1995, respectively). the population abundances of p. gualpensis (with the exception of the period october 1995-january 1996) were similar at both sites. interannual comparisons of macroinfaunal abundances carried out for the sandy site showed no significant differences among years for the total macroinfauna and for all the species, but p. gualpensi
Impacts of seasonal and regional variability in biogenic VOC emissions on surface ozone in the Pearl River Delta region, China  [PDF]
S. Situ,A. Guenther,X. Wang,X. Jiang
Atmospheric Chemistry and Physics Discussions , 2013, DOI: 10.5194/acpd-13-6729-2013
Abstract: In this study, the BVOC emissions in November 2010 over the Pearl River Delta (PRD) region in southern China have been estimated by the latest version of a Biogenic Volatile Organic Compound (BVOC) emission model (MEGAN v2.1). The evaluation of MEGAN performance at a representative forest site within this region indicates MEGAN can estimate BVOC emissions reasonably well in this region except overestimating isoprene emission in autumn for reasons that are discussed in this manuscript. Along with the output from MEGAN, the Weather Research and Forecasting model with chemistry (WRF-Chem) is used to estimate the impacts of BVOC emissions on surface ozone in the PRD region. The results show BVOC emissions increase the daytime ozone peak by ~3 ppb on average, and the max hourly impacts of BVOC emissions on the daytime ozone peak is 24.8 ppb. Surface ozone mixing ratios in the central area of Guangzhou-Foshan and the western Jiangmen are most sensitive to BVOC emissions BVOCs from outside and central PRD influence the central area of Guangzhou-Foshan and the western Jiangmen significantly while BVOCs from rural PRD mainly influence the western Jiangmen. The impacts of BVOC emissions on surface ozone differ in different PRD cities, and the impact varies in different seasons. Foshan and Jiangmen being most affected in autumn, result in 6.0 ppb and 5.5 ppb increases in surface ozone concentrations, while Guangzhou and Huizhou become more affected in summer. Three additional experiments concerning the sensitivity of surface ozone to MEGAN input variables show that surface ozone is more sensitive to landcover change, followed by emission factors and meteorology.
PARTICLE-SIZE CHARACTERISTICS AND SEASONAL VARIABILITY OF SUSPENDED PARTICULATE MATTERS IN THE CHANGJIANG RIVER ESTUARY
长江口悬浮体粒度特征及其季节性差异

LI Jun,GAO Shu,ZENG Zhi-Gang,JIA Jian-Jun,
李 军
,高 抒,曾志刚,贾建军

海洋与湖沼 , 2003,
Abstract: Grain size compositions of 78 samples of suspended particulate matter collected from the Changjiang River estuary during November 1998 and May 1999 were analyzed with a Cilas-940L Laser Grain-size Analyzer.The results show that the suspended sediment consists mainly of fine-grained (silt) materials,relatively poorly sorted,with small skewness and kurtosis values; the grain size decreases in the seaward direction.The particle-size distribution curves show bimodal or multi-modal patterns,and several peaks are present in the curves of the standard deviation versus particle size.The correlation between the SPM concentration and the median particle-size is poor,but it is high between the inorganic particle content and D 50,indicating that the terrigenous detritus content of SPM is an important factor controlling the particle size of the SPM.Further,there is significant seasonal variability of the particle-size characteristics.The main factors affecting the variability include sediment sources,tidally-induced resuspension of bottom sediment,biological activity,and flocculation of fine-grained particles.
Seasonal and interannual variability of sedimentation and organic matter distribution in the Buor-Khaya Gulf: the primary recipient of input from Lena River and coastal erosion in the southeast Laptev Sea
A. N. Charkin, O. V. Dudarev, I. P. Semiletov, A. V. Kruhmalev, J. E. Vonk, L. Sánchez-García, E. Karlsson, . Gustafsson
Biogeosciences (BG) & Discussions (BGD) , 2011,
Abstract: Climate warming is amplified in the land-sea system of the East Siberian Arctic, which also holds large pools of vulnerable carbon in permafrost. This coastal area is strongly influenced by sediment and carbon transport from both its large rivers and extensive erosion of Pleistocene permafrost along its coastline. This study is investigating the coastal fate of the sediment and organic carbon delivered to the Buor-Khaya Gulf, which is the first recipient of the overwhelming fluvial discharge from the Lena River and is additionally receiving large input from extensive erosion of the coastal ice-complex (permafrost a.k.a. Yedoma; loess soil with high organic carbon content). Both water column suspended particulate matter (SPM) and surface sediments were sampled at about 250 oceanographic stations in the Gulf in this multi-year effort, including one winter campaign, and analyzed for the distribution and sorting of sediment size, organic carbon content, and stable carbon isotope signals. The composition of the surface sediment suggests an overwhelmingly terrestrial contribution from both river and coastal erosion. The objective of this paper is to improve our understanding of the seasonal (i.e., winter vs summer) and interannual variability of these coastal sedimentation processes and the dynamics of organic carbon (OC) distribution in both the water column SPM and the surface sediments of the Buor-Khaya Gulf. Based on data collected during several years in the period 2000–2008, two different sedimentation regimes were revealed for the Buor-Khaya Gulf, the relative importance of each at a given time depend on hydrometeorological conditions, the Lena River water discharge and sea-ice regime: Type 1 erosion-accumulation and Type 2 accumulation. The Type 1 erosion-accumulation sedimentation regime is typical (2000–2006) for the ice-free period of the year (here considered in detail for August 2005). Under such conditions terrigenous sources of SPM and particulate organic carbon (POC) stem predominantly from river discharge, thermal erosion of coastal ice-complex and remobilized bottom sediments. The Type 2 accumulation sedimentation regime develops under ice-covered conditions, and only occasionally during the ice-free period (August 2008). In Type 2 winter, combined terrigenous and marine-biogenic SPM and POC sources are dominating due to relatively low overall terrigenous input (April 2007). In Type 2 summer, river alluvium becomes the major SPM and POC source (August 2008). The water column SPM and POC loadings vary by more than a factor of two between the two regimes. This study underscores the necessity of multi-year investigations to better understand the functioning of the primary recipient of terrestrially expulsed matter in the East Siberian Arctic.
Variabilidade sazonal da rela o entre a radia o fotossinteticamente ativa e a radia o global na bacia do rio Doce, Estado de Minas Gerais = Seasonal variability of the relationship between the photosynthetically active radiation and the global radiation at the river Doce basin, Minas Gerais State
Antonio José Steidle Neto,Aristides Ribeiro,Sérgio Zolnier,Fernando Palha Leite
Acta Scientiarum : Agronomy , 2006,
Abstract: O conhecimento da Radia o Fotossinteticamente Ativa (RFA) é importante para diferentes áreas relacionadas à fisiologia vegetal e ciências agrárias. Modelos de estimativa de RFA a partir da Radia o Global (Rg) s o extremamente úteis, visto que a Rg é convencionalmente medida nas esta es meteorológicas. Assim, analisou-se a variabilidade sazonal da rela o RFA/Rg em cinco áreas localizadas na bacia do rio Doce, Estado de Minas Gerais, considerando-se os períodos secos e chuvosos dos anos de 2001 a 2004. As rela es RFA/Rg obtidas para os períodos secos e chuvosos, assim como para todos os dados, apresentaram concordancia com as rela es determinadas por diversos pesquisadores em diferentes áreas do mundo. Analisando-se os resultados, constatou-se que, de maneira geral,as rela es RFA/Rg tendem a ser superiores durante os períodos chuvosos comparativamente aos secos. Por este estudo, p de-se concluir que existe varia o interanual desta rela o, demonstrando assim a necessidade de se considerar esta variabilidade para estimaradequadamente a RFA a partir da Rg. The knowledge of the Photosynthetically Active Radiation (PAR) is important to different areas of vegetal physiology and agricultural sciences. Estimation models of the PAR based on the Global Radiation (GR) are extremely useful, since the GR is conventionally measured atthe meteorological stations. Thus, the seasonal variability of the relationship PAR/GR was analyzed in five areas located at the river Doce basin, Minas Gerais State, Brazil, considering the dry and wet periods of the years 2001 to 2004. The relationships PAR/GR obtained for the dry and wet periods, and also to all data, presented agreement with those ones determined by several researchers in different areas of the world. Results showed that the relationshipsPAR/GR generally tend to be greater during the wet periods when compared with the dry ones. By this work, it could be concluded that there is interannual variability of this relationship, showing thus, the need to consider this variability to estimate the PAR based onGR appropriately.
Influence of River Plume on Variability of Chlorophyll a Concentration using Satellite Images  [PDF]
T. Lihan,M.A. Mustapha,S.A. Rahim,S. Saitoh
Journal of Applied Sciences , 2011,
Abstract: Freshwater discharge from rivers into the ocean is an important element of the dynamics in coastal areas. River discharge from land that includes chlorophyll a, nutrients, sediments and pollutants have been identified as one of the major causes of deterioration of the coastal water. The objective of this study was to examine the relationship between river discharge and variability of chlorophyll a concentration in plume area using satellite imagery. Satellite ocean color and Sea Surface Temperature (SST) imagery were used to present the synoptic quantification of chlorophyll a variability on seasonal and interannual timescales for the plume area of Tokachi River, Japan. Five years (1998 to 2002) of SeaWiFS local area coverage, AVHRR imagery and surface wind were analyzed using default NASA coefficients and community-standard algorithms as implemented by SeaDAS. The chlorophyll a climatology seasonal pattern showed seasonal cycles, first peak in spring and second peak in late summer to early autumn. Elevated chlorophyll a concentration demonstrates seasonal cycles and interannual variability are present around plume area associated with variation of river discharge. Elevated chlorophyll a concentration in offshore area was seen to be influenced by low sea surface temperature and wind stress.
Seasonal and interannual variability of sedimentation and organic matter distribution in the Buor Khaya Gulf – the primary recipient of input from Lena River and coastal erosion in the SE Laptev Sea  [PDF]
A. N. Charkin,O. V. Dudarev,I. P. Semiletov,A. V. Kruhmalev
Biogeosciences Discussions , 2011, DOI: 10.5194/bgd-8-1917-2011
Abstract: Climate warming is amplified in the land-sea system of the East Siberian Arctic, which also holds large pools of vulnerable carbon in permafrost. This coastal area is strongly influenced by sediment and carbon transport from both its large rivers and extensive erosion of Pleistocene permafrost along its coastline. This study is investigating the coastal fate of the sediment and organic carbon delivered to the Buor-Khaya Gulf, which is the first recipient of the 16 overwhelming fluvial discharge from the Lena River and is additionally receiving large input from extensive erosion of the coastal ice-complex (permafrost a.k.a. Yedoma; loess soil with high organic carbon content). Both water column suspended particulate matter (SPM) and surface sediments were sampled at about 250 oceanographic stations in the Gulf in this multiyear effort, including one winter campaign, and analyzed for the distribution and sorting of sediment size, organic carbon content, and stable carbon isotope signals. The composition of the surface sediment suggests an overwhelmingly terrestrial contribution from both river and coastal erosion. Based on data collected during several years in the period 2000–2008, two different sedimentation regimes were revealed for the Buor-Khaya Gulf, the relative importance of each at a given time depend on hydrometeorological conditions, the Lena River water discharge and sea-ice regime: Type 1 erosion-accumulation and Type 2 accumulation. The Type 1 erosion-accumulation sedimentation regime is typical (2000–2006) for the ice-free period of the year (here considered in detail for August 2005). Under such conditions terrigenous sources of suspended particulate matter (SPM) and particulate organic carbon (POC) stem predominantly from river discharge, thermal erosion of coastal ice-complex and remobilized bottom sediments. The Type 2 accumulation sedimentation regime develops under ice-covered conditions, and only occasionally during the ice-free period (August 2008). In Type 2 winter, combined terrigenous and marine-biogenic SPM and POC sources are dominating due to relatively low overall terrigenous input (April 2007). In Type 2 summer, river alluvium becomes the major SPM and POC source (August 2008). The water column SPM and POC loadings vary by more than a factor of two between the two regimes. This study underscores the necessity of multi-year investigations to better understand the functioning of the primary recipient of terrestrially expulsed matter in the East Siberian Arctic.
Spatial distribution and seasonal variability in chlorophyll concentrations in the coastal Lake Gardno (Poland)
Dariusz Ficek, Magdalena Wielgat-Rychert
Oceanological and Hydrobiological Studies , 2009, DOI: 10.2478/v10009-009-0002-z
Abstract: In 2006 the spatial distribution and seasonal variations in chlorophyll concentration were measured, at about two-week frequency, in Lake Gardno. In general, chlorophyll concentrations in the central part of the lake were high throughout the growth season. The minimum chlorophyll concentration was recorded in March (7.5 mg m-3), and the maximum value in September (303 mg m-3). Higher chlorophyll concentrations and lower temporal variability were measured in the central part of the lake, compared to lower concentrations and higher variability in the vicinity of the upawa River input to the lake. Chlorophyll concentrations were measured fluorometrically along several vertical and horizontal profiles, enabling direct observations of the dynamics of changing chlorophyll concentrations in Lake Gardno throughout the year.
Seasonal characteristic and interannual variability of the atmospheric hydrological cycle in the Yangtze River basin during the summer monsoon period
夏季风期间长江流域的水汽输送状态及其年际变化

ZHAO Rui-Xia,WU Guo-Xiong,ZHANG Hong,
赵瑞霞

地球物理学报 , 2008,
Abstract: The atmospheric hydrological cycle over the Yangtze River basin during summer monsoon period is examined using the NCEP/NCAR reanalysis.The primary focus is the linkage between the interannual variability of the moisture convergence in Yangtze River and the large-scale water vapor transport and circulation fields.The southwest wind over the basin is strongest during June to July.The meridional water vapor transport makes convergence over the river in May to August,and divergence over it in September;and the zonal water vapor transport makes divergence over the river in May to July,and convergence over it in August to September.During the period when the summer monsoon is comparatively weaker over the east of China,such as May,August and September,the interannual variation of the water vapor budget over the river is significantly affected by the variation of the south wind across the south boundary.While the Yangtze River is unusually wet,an anomalous low-pressure is established over the east of Qinghai-Tibet plateau for the three months,and an anomalous anti-cyclonic circulation accompanied with a positive air pressure anomaly is established over Indo-China Peninsula as well as its eastern ocean in August and September.These two anomalous circulations all increase the water vapor input through the south boundary.But during the period when the summer monsoon is comparatively stronger over the east of China,such as June and July,the water vapor output by the south wind across the north boundary is evidently increased,and becomes the most vital path for the interannual variation of the water vapor budget over the river.While the river is unusually wet,an anomalous cyclonic circulation accompanied with a negative pressure anomaly is established in June over the Yellow Sea and the East China Sea in mid-latitude,and an anomalous anti-cyclonic circulation accompanied with a positive air pressure anomaly is established in July over the region around the outer Xinganling mountain in mid and high latitude.These two different anomalous circulations all decrease the water vapor output through the north boundary.
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