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The Yellow Sea Cold Water Mass (YSCWM) is one of the important water mass in the Yellow Sea (YS). It is distributed in the lower layer in the Yellow Sea central trough with the temperature less than 10°C and the salinity lower than 33.0. To understand the variability of the YSCWM, the hydrographic data obtained in April and August during 2009-2011 are analyzed in the southeastern Yellow Sea. In August 2011, relatively warm and saline water compared with that in 2009 and 2010 was detected in the lower layer in the Yellow Sea central area. Although the typhoon passed before the cruise, the salinity in the Yellow Sea central trough is much higher than the previous season. It means that the saline event cannot be explained by the typhoon but only by the intrusion of saline water during the previous winter. In April 2011, actually, warm and saline water ( T >10°C, S >34) was observed in the deepest water depth of the southeastern area of the Yellow Sea. The wind data show that the northerly wind in 2011 winter is stronger than in 2009 and 2010 winter season. The strong northerly wind can trigger the intrusion of warm and saline Yellow Sea Warm Current. Therefore, it is proposed that the strong northerly wind in winter season leads to the intrusion of the Yellow Sea Warm Current into the Yellow Sea central trough and influenced a variability of the YSCW Min summer. [ABSTRACT FROM AUTHOR]

A hydrodynamic-biogeochemical model was coupled to an individual-based fish model (IBM) to study the influence of physical and biological processes on Peruvian anchovy recruitment. Temperature and the concentrations of four plankton groups from a 1991 to 2007 simulation of a Pacific basin-scaled Regional Ocean Model System (ROMS) coupled with the Carbon Silicate Nitrogen Ecosystem (CoSiNE) model were used as inputs to the anchovy IBM. The anchovy IBM domain covered the upwelling area (0–20°S and 70–85°W) from 0 to 100m depth, and was 166 by 120 cells with 10 vertical. A cohort of eggs was started each month from 1991 to 2007, and individuals within each cohort followed through daily development, growth, mortality, and movement for one year. Growth was represented with a bioenergetic equation that used temperature and plankton concentrations from the ROMS–CoSiNE simulation as input. Mortality rate was stage-dependent and length-dependent. Movement of eggs and larvae was based on passive transport, and movement of juveniles and adults was a combination of passive transport and behavioral movement. Average number of days required to reach 5cm and the number surviving to 5cm were used as measures of recruitment. Averaged temperature and plankton concentrations within the IBM spatial domain showed strong interannual variation, and spatial and temporal patterns typical of the Peruvian upwelling system. Modeled anchovy growth and survival also showed strong interannual variation that resulted in large fluctuations in recruitment. Growth in a normal year resulted in anchovy requiring about 60–80 days to reach 5cm and the number of recruits was around 1010. Averaged anchovy length and number of survivors after 6 months for all monthly cohorts combined showed that good growth conditions and high survival occurred in the region from 5°S to 17°S, within 200km offshore and in the upper 100m. Vertically, centers of population distribution occurred at depths of 10m and between 50 and 70m. During the 1997–1998 El Niño, anchovy growth rate decreased so that it took fish 150–270 days to reach 5cm, and the numbers of survivors was about five orders of magnitude lower. Model results showed anchovy during El Niño conditions were located closer to shore, farther south, and at deeper depths than in normal years. Model results of interannual variation were insensitive to the length of anchovy used to define recruitment, how passive transport and behavioral movement were combined within different life stages, and to the starting locations of the monthly egg cohorts within the IBM domain. We discuss how our results can be used to infer anchovy recruitment under future climate change. [ABSTRACT FROM AUTHOR]

The Weather Research and Forecasting (WRF) model is used in a regional climate model configuration to simulate past precipitation climate of China during the rainy season (May-September) of 1981-2000, and to investigate potential future (2041-2060 and 2081-2100) changes in precipitation over China relative to the reference period 1981-2000. WRF is run with initial conditions from a coupled general circulation model, i.e., the high-resolution version of MIROC (Model for Interdisciplinary Research on Climate). WRF reproduces the observed distribution of rainy season precipitation in 1981-2000 and its interannual variations better than MIROC. MIROC projects increases in rainy season precipitation over most parts of China and decreases of more than 25 mm over parts of Taiwan and central Tibet by the mid-21st century. WRF projects decreases in rainfall over southern Tibetan Plateau, Southwest China, and northwestern part of Northeast China, and increases in rainfall by more than 100 mm along the southeastern margin of the Tibetan Plateau and over the lower reaches of the Yangtze River during 2041-2060. MIROC projects further increases in rainfall over most of China by the end of the 21st century, although simulated rainfall decreases by more than 25 mm over parts of Taiwan, Guangxi, Guizhou, and central Tibet. WRF projects increased rainfall of more than 100 mm along the southeastern margin of the Tibetan Plateau and over the lower reaches of the Yangtze River and decreased rainfall over Southwest China, and southern Tibetan Plateau by the end of the 21st century. [ABSTRACT FROM AUTHOR]

Using Joint Typhoon Warning Center tropical cyclone (TC) track data over the North Indian Ocean (NIO), National Centers for Environmental Prediction monthly reanalysis wind and outgoing long-wave radiation data, and National Oceanic and Atmospheric Administration sea surface temperature data from 1981 to 2010, spatiotemporal distributions of NIO TC activity and relationships with local sea surface temperature (SST) were studied with statistical diagnosis methods. Results of empirical orthogonal function (EOF) analysis of NIO TC occurrence frequency show that the EOF1 mode, which accounts for 16% of total variance, consistently represents variations of TC occurrence frequency over the whole NIO basin. However, spatial distributions of EOF1 mode are not uniform, mainly indicating variations of westward-moving TCs in the Bay of Bengal. The prevailing TC activity variation mode oscillates significantly on a quasi-5 year interannual time scale. NIO TC activity is notably influenced by the Indian Ocean dipole (IOD) mode. When the Indian Ocean is in a positive (negative) phase of the IOD, NIO SST anomalies are warm in the west (east) and cold in the east (west), which can weaken (strengthen) convection over the Bay of Bengal and eastern Arabian Sea, and cause anticyclonic (cyclonic) atmospheric circulation anomalies at low levels. This results in less (more) TC genesis and reduced (increased) opportunities for TC occurrence in the NIO. In addition, positive (negative) IOD events may strengthen (weaken) westerly steering flow over the Bay of Bengal, which further leads to fewer (more) westward-moving TCs which appear in regions west of 90°E in that bay. [ABSTRACT FROM AUTHOR]

We analyzed the temporal and spatial variation, and interannual variability of the North Pacific meridional overturning circulation using an empirical orthogonal function method, and calculated mass transport using Simple Ocean Data Assimilation Data from 1958-2008. The meridional streamfunction field in the North Pacific tilts N-S; the Tropical Cell (TC), Subtropical Cell (STC), and Deep Tropical Cell (DTC) may be in phase on an annual time scale; the TC and the STC are out of phase on an interannual time scale, but the interannual variability of the DTC is complex. The TC and STC interannual variability is associated with ENSO (El Niño-Southern Oscillation). The TC northward, southward, upward, and downward transports all weaken in El Niños and strengthen in La Niñas. The STC northward and southward transports are out of phase, while the STC northward and downward transports are in phase. Sea-surface water that reaches the middle latitude and is subducted may not completely return to the tropics. The zonal wind anomalies over the central North Pacific, which control Ekman transport, and the east-west slope of the sea level may be major factors causing the TC northward and southward transport interannual variability and the STC northward and southward transports on the interannual time scale. The DTC northward and southward transports decrease during strong El Niños and increase during strong La Niñas. DTC upward and downward transports are not strongly correlated with the Niño-3 index and may not be completely controlled by ENSO. [ABSTRACT FROM AUTHOR]

The Hawaiian Lee Countercurrent (HLCC) is an eastward surface current flowing against the broad westward flow of the North Pacific subtropical circulation. Analyses of satellite altimeter data over 16 years revealed that the HLCC is characterized by strong interannual variations. The strength and meridional location of the HLCC axis varied significantly year by year. The eastward velocity of the HLCC was higher when the location of the axis was stable. Mechanisms for the interannual variations were explored by analyses of the altimeter data and results from a simple baroclinic model. The interannual variations in the strength of the HLCC did not correlate with those of the wind stress curl (WSC) dipole formed on the leeward side of the Hawaii Islands, although the WSC dipole has been recognized as the generation mechanism of the HLCC. Meridional gradients of the sea surface height anomaly (SSHA) across the HLCC generated by baroclinic Rossby waves propagating westward from the east of the Hawaii Islands were suggested as a possible mechanism for the interannual variations in the HLCC. The spatial patterns in the observed SSHAs were reproduced by a linear baroclinic Rossby wave model forced by wind fields from a numerical weather prediction model. Further analysis of the wind data suggested that positive and negative anomalies of WSC associated with changes in the trade winds in the area east of the Hawaii Islands are a major forcing for generating SSHAs that lead to the HLCC variations with a time lag of about 1 year. [ABSTRACT FROM AUTHOR]

As ammonia is the main component of PM 2.5 , long time series of ammonia emission characteristics are an important basis for studying the historical causes of PM 2.5 pollution. In this study, the activity data of various anthropogenic ammonia emissions from 11 cities were collected in Zhejiang. The anthropogenic ammonia emissions inventory in Zhejiang was established using emission factors, and then a 1 km×1 km spatial grid distribution was carried out using ArcGIS software. The results showed that from 2008 to 2018, the ammonia emissions from anthropogenic sources in Zhejiang exhibited a downward trend, with an average annual decline rate of approximately 3.97%. The ammonia emissions were 108.52 kt in 2018, and the emission intensity was 1.03 t·km -2 , in which there was 90.02 kt from agricultural sources and 18.50 kt from non-agricultural sources. The ammonia emissions of Hangzhou, Jiaxing, and Wenzhou were higher than those of the other cities, accounting for 14.72%, 11.86%, and 11.80% of the total ammonia emissions, respectively. The spatial distribution characteristics showed that ammonia emissions were mainly distributed in the northern part of Zhejiang, showing an emission trend of "high in the north and low in the south." Uncertainty analysis showed that the simulated average value of ammonia emissions was 108.37 kt, and the uncertainty range in the 95% confidence interval was -5.40%-5.60%.

Elucidating the interannual variation of soil organic nitrogen fractions and its response to straw returning is of great significance for rational regulation of soil organic nitrogen pool and sustainable soil utilization. We conducted a field microcosm experiment with typic hapludoll soil at the National Field Observation and Research Station of Shenyang Agroecosystems. Three treatments were set, including nitrogen fertilizer addition (200 kg N·hm -2 , the same in other treatments), nitrogen fertilizer addition with 50% straw return, and nitrogen fertilizer addition with 100% straw return. We classified soil organic nitrogen fractions in the 1st, 3rd, 6th, and 9th years of the experiment by using the Bremner acid hydrolysis method. The results showed that the content of amino acid nitrogen increased with the tillage years, with an increase rate of 39.8% compared with 1st year. The content of hydrolyzable unknown nitrogen increased by 10.8% compared with 1st year, which reached the highest in the 3rd year. The content of total soil nitrogen and other organic nitrogen fractions showed limited variation with tillage years. The proportion of hydrolyzable total nitrogen that is relatively easy to mineralize in the total soil nitrogen gradually increased with the tillage years, and that of relatively stable acid insoluble nitrogen to total soil nitrogen gradually decreased, indicating that soil nitrogen availability increased with the tillage years, which would facilitate the soil nitrogen supply capacity. Compared with the treatment without straw returning, adding straw improved soil total nitrogen and each hydrolyzable nitrogen contents, with such positive effect be stronger under the treatment with heavier straw returning. The effect of straw returning on hydrolyzable nitrogen fractions mainly occurred in the 6th and 9th years. The components of soil total nitrogen that have been increased were mainly the amino acid nitrogen and hydrolyzed unknown nitrogen, resulting in increased proportion of hydrolyzable nitrogen. Straw returning could increase soil nitrogen pool and improve soil nitrogen conservation and supply capacity.

Abstract: Nitrous oxide (N2O) fluxes were measured over a 3-year period (2004–2007) in a long-term experimental field. The objectives of the study were to evaluate the interannual variation of N2O emissions from a maize–wheat rotation, under different fertilizer regimes and to determine the key controlling factors. The study involved four treatments: compost (OM), half compost N plus half inorganic fertilizer-N (HOM), inorganic fertilizer-N (NPK), and control (CK) where no N application. The mean annual N2O emission over a 3-year period was 0.30 ± 0.11 kg N2O–N ha−1 in the CK treatment, but increased to 1.61 ± 0.10 kg N2O–N ha−1 in the HOM treatment, 2.13 ± 0.15 kg N2O–N ha−1 in the OM treatment, and 2.76 ± 0.19 kg N2O–N ha−1 in the NPK treatment. Differences were significant among treatments. The N2O emission factors of the applied OM, NPK and HOM were 0.61 ± 0.02, 0.82 ± 0.10 and 0.44 ± 0.04%, respectively, at a rate of 300 kg N ha−1 year−1, indicating that the combined application of compost with inorganic fertilizer significantly reduced N2O emission. Over a maize–wheat rotation year, more than 65% of the annual N2O emission occurred during the maize growing season. There was a large interannual variation in N2O emission in all treatments, albeit not significant either during the maize growing season or at an inter-year scale. This interannual variation was mainly attributable to differences in soil moisture after basal fertilizer application, and irrigation and/or heavy rainfall events immediately following basal fertilization could induce more N2O production than pre-irrigation before plowing. The HOM treatment had higher N fertilizer use efficiency and lowest yield-scaled N2O emissions compared with the OM and NPK treatments. We therefore argue that the combined application of half compost N plus half fertilizer-N will mitigate N2O emissions from soils in the North China plain. [Copyright &y& Elsevier]

A bstract Many of the statistical techniques commonly used in ecology assume independence among responses. However, there are many marine mammal survey techniques, such as those involving time series or subgroups, which result in correlations within the data. Generalized estimating equations (GEEs) take such correlations into account and are an extension of generalized linear models. This study demonstrates the application of GEEs by modeling temporal variation in bottlenose dolphin presence from sightings data. Since dolphins could remain in the study area for several hours resulting in temporal autocorrelation, an autoregressive correlation structure was used within the GEE, each cluster representing hours within a day of survey effort. The results of the GEE model showed that there was significant diel, tidal, and interannual variation in the presence of dolphins. Dolphins were most likely to be seen in the early morning and during the summer months. Dolphin presence generally peaked during low tide, but this varied among years. There was a significantly lower probability of dolphins being present in 2003 than 2004, but not between 2004 and the other years (1991, 1992, and 2002). GEE-model fitting packages are now readily available, making this a valuable, versatile tool for marine mammal biologists. [ABSTRACT FROM AUTHOR]

With the unprecedented spaceborne precipitation radar (PR), the Tropical Rainfall Measuring Mission (TRMM) satellite has collected high-quality precipitation measurements for over ten years. The TRMM/PR data are nowadays extensively exploited in numerous meteorological and hydrological fields. Yet an artificial orbit boost of the TRMM satellite in August 2001 modulated the observation parameters, which inevitably affects climatological applications of the PR data and needs to be clarified. This study investigates the orbit boost effects of the TRMM satellite on the PR-derived precipitation characteristics. Both the potential impacts on precipitation frequency (PF) and precipitation intensity (PI) are carefully analyzed. The results show that the total PF decreases by 8.3% and PI increases by 4.0% over the tropics after the orbit boost. Such changes significantly exceed the natural variabilities and imply the strong effects of orbit boost on precipitation characteristics. The impacts on stratiform precipitation and convective precipitation are inconsistent, which is attributed to their distinct precipitation features. Further analysis reveal that the increased PI of stratiform precipitation is mainly due to the decreased frequencies of light precipitation, while the semi-constant PI of convective precipitation is caused by the concurrently decreased frequencies of light and heavy precipitation. A modification is applied to the post-boost PR precipitation data to retrieve the actual trends of tropical precipitation characteristics. It is found that the PI of total-precipitation approximately keeps invariable from 1998 to 2005. The total PF has no obvious trend over tropical oceans but decreases considerably over tropical lands. [ABSTRACT FROM AUTHOR]

Aim Temporal variation in animal-landscape relationships hinders management decisions and development of conservation policy. Animal-landscape relationships may be modelled using several model selection criteria ( MSC), but how such criteria affect measures of temporal variation of modelled relationships is unclear. Location Appalachian Mountains, USA. Methods We used results from linear and logistic regression models for 98 bird species over a 5-year period to compute two measures of interannual variation in bird-landscape relationships: model consistency reflected the degree to which variables and directions of relationships in a model were the same. R2 coefficient of variation ( R2 CV) reflected the degree to which the strength of relationships was the same. We calculated both metrics for each species' models after using four common MSC: AICc, BIC, stepwise-0.15 and adjusted R2. Results Although positively correlated ( r = 0.43−> 0.99; P = 0.030−< 0.001), interannual variation metrics for species differed up to 80% among different MSC. One exception was that using stepwise-0.15 and AICc resulted in identical bird-landscape models > 90% of the time and thus produced the same interannual variation metrics for those models. MSC affected R2 CV less than model consistency. Model consistency did not differ significantly among MSC. Use of BIC led to the highest R2 CV (greatest interannual variation), and use of AICc and stepwise-0.15 led to the lowest R2 CV. Main conclusions Comparisons of interannual variation metrics across studies or regions should be based on models derived from the same MSC. When cross-study comparisons must be made, effects of MSC on interannual variation in the strength of relationships ( R2 CV) may be smaller than effects of MSC on interannual variation in the identity of relationships (model consistency). Model consistency metrics could potentially be used in concert with other model evaluation criteria to refine landscape-based species conservation planning. [ABSTRACT FROM AUTHOR]

The relationship between heat content and sea surface height (SSH) in the global ocean on the interannual time scale is examined with satellite altimeter measurements, historical hydrography, and model assimilation outputs. Results show that correlation between altimetric SSH and heat content in the upper 700 m calculated from Ishii data is geographically nonuniform. In the tropical ocean, heat content and SSH are strongly correlated and exhibit nearly the same interannual variations. In the polar ocean, their correlation is relatively weak. Further analysis with Simple Ocean Data Assimilation outputs shows that such nonuniform distribution is not from dynamical origin but from the limited integral depth selected to calculate heat content. The integral depth of 700 m is inadequate to capture variation of the deep main thermocline in the polar region. The halosteric effect also contributes to the nonuniform pattern of correlation, because saline contraction becomes significant in the polar ocean owing to low temperature. [ABSTRACT FROM AUTHOR]

The interannual variability of occurrence of multiple tropical cyclone (MTC) events during June-October in the western North Pacific (WNP) was examined for the period 1979-2006. The number of the MTC events ranged from 2 to 9 per year, exhibiting a remarkable year-to-year variation. Seven active and seven inactive MTC years were identified. Compared to the inactive years, tropical cyclone genesis locations extended farther to the east and in the meridional direction during the active MTC years. A composite analysis shows that inactive MTC years were often associated with the El Niño decaying phase, as warm SST anomalies in the equatorial eastern-central Pacific in the preceding winter transitioned into cold sea surface temperature (SST) anomalies in the concurrent summer. Associated with the SST evolution were suppressed low-level cyclonic vorticity and weakened convection in the WNP monsoon region. In addition to the mean flow difference, significant differences between active and inactive MTC years were also found in the strength of the atmospheric intraseasonal oscillation (ISO). Compared with inactive MTC years, ISO activity was much stronger along the equator and in the WNP region during active MTC years. Both westward- and northward-propagating ISO spectrums strengthened during active MTC years compared to inactive years. The combined mean state and ISO activity changes may set up a favorable environment for the generation of MTC events. [ABSTRACT FROM AUTHOR]

The interannual variation of precipitation in the southern part of Iran and its link with the large-scale climate modes are examined using monthly data from 183 meteorological stations during 1974-2005. The majority of precipitation occurs during the rainy season from October to May. The interannual variation in fall and early winter during the first part of the rainy season shows apparently a significant positive correlation with the Indian Ocean Dipole (IOD) and El Niño-Southern Oscillation (ENSO). However, a partial correlation analysis used to extract the respective influence of IOD and ENSO shows a significant positive correlation only with the IOD and not with ENSO. The southeasterly moisture flux anomaly over the Arabian Sea turns anti-cyclonically and transport more moisture to the southern part of Iran from the Arabian Sea, the Red Sea, and the Persian Gulf during the positive IOD. On the other hand, the moisture flux has northerly anomaly over Iran during the negative IOD, which results in reduced moisture supply from the south. During the latter part of the rainy season in late winter and spring, the interannual variation of precipitation is more strongly influenced by modes of variability over the Mediterranean Sea. The induced large-scale atmospheric circulation anomaly controls moisture supply from the Red Sea and the Persian Gulf. [ABSTRACT FROM AUTHOR]

Tropospheric ozone observations over China from 2005 to 2010 at three pressure levels (484, 681 and 825 hPa) from the Tropospheric Emission Spectrometer on board the NASA Aura satellite have been analyzed. Fourier Transform analysis revealed the trends and seasonality of regionally-averaged, monthly-mean ozone concentrations over western, northern and southern China. Significant increases in ozone levels are found over all three regions at 464 hPa and the rate of increase is fastest over northern China, reaching 0.89±0.059 nL/(L a). At 681 hPa, ozone shows increases over northern and western China, at a rate of 0.57± 0.065 nL/(L a) and 0.41±0.041 nL/(L a) respectively, but is constant over southern China. At 825 hPa, ozone increases at a rate of 0.36±0.074 nL/(L a) over northern China, while decreasing over southern China at a rate of −0.21±0.061 nL/(L a). Over the three regions, ozone levels are generally higher in summer and lower in winter. Over southern China at all three pressure levels and northern China at the 825 hPa level, ozone shows double peaks occurring in spring and autumn as a result of the combined effects of atmospheric chemistry and global transport. This work provides a useful observational dataset and tools for future analysis of changes in tropospheric ozone over China. [ABSTRACT FROM AUTHOR]

When restoring ecosystems dominated by exotic plants, reinvasion pressure, or the rate of new exotic recruitment following mature exotic removal, can vary broadly between similarly invaded habitats. Reinvasion pressure strongly influences restoration costs and outcomes but is difficult to predict. Ontogenetic niche shifts (ONSs, changes in niche breadth or position during development) in exotic species paired with interannual variation in abiotic conditions may decouple pre-removal mature exotic density and average reinvasion pressure. Identifying such decouplings could improve restoration efficiency by informing site selection and management strategies, but requires estimates of average reinvasion pressure that mandate greater understanding of its principle drivers. We hypothesize that reinvasion pressure is predominantly driven by exotic propagule abundance and spatiotemporal availability of realized recruitment windows, which are periods of variable duration that permit exotic establishment from propagules. Realized recruitment windows are based on the 'safe sites' concept but account for ONSs and are determined by abiotic conditions and interspecific interactions with recipient communities. Biotic resistance or facilitation may increase or decrease times required for establishment by influencing exotic growth rates or altering niche availability and may permit or preclude establishment in marginal abiotic conditions. We discuss factors influencing reinvasion pressure, basic approaches to estimate reinvasion pressure, and potential ways to increase management efficiency under different reinvasion pressure scenarios. Accurate estimates of reinvasion pressure could improve restoration efficacy, efficiency, and predictability in ecosystems dominated by exotic plants. We argue that greater theoretical and practical considerations of reinvasion pressure and ONSs are merited. [ABSTRACT FROM AUTHOR]

In a deciduous larch forest in eastern Siberia, the mean and standard deviation of the total evapotranspiration ( E) during May to September (day of year (DOY) = 121-274) for 2003-2006 were 181.5 and 26.4 mm, respectively. The interannual variation (IAV) in the total E was caused by the IAV in E for the canopy-foliated period (DOY = 164-253), not by the IAV in the dates of leaf expansion and leaf fall. For the years with higher total E, E in the canopy-foliated period was consistently higher, which corresponded to the higher soil water content in these years. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The warming of the Arctic Intermediate Water (AIW) is studied based on the analyses of hydrographic observations in the Canada Basin of the Arctic Ocean during 1985-2006. It is shown that how the anomalously warm AIW spreads in the Canada Basin during the observation time through the analysis of the AIW temperature spatial distribution in different periods. The results indicate that by 2006, the entire Canada Basin has almost been covered by the warming AIW. In order to study interannual variability of the AIW in the Canada Basin, the Canada Basin is divided into five regions according to the bottom topography. From the interannual variation of AIW temperature in each region, it is shown that a cooling period follows after the warming event in upstream regions. At the Chukchi Abyssal Plain and Chukchi Plateau, upstream of the Arctic Circumpolar Boundary Current (ACBC) in the Canada Basin, the AIW temperature reached maximum and then started to fall respectively in 2000 and 2002. However, the AIW in the Canada Abyssal Plain and Beaufort Sea continues to warm monotonically until the year 2006. Furthermore, it is revealed that there is convergence of the AIW depth in the five different regions of the Canada Basin when the AIW warming occurs during observation time. The difference of AIW depth between the five regions of the Canada Basin is getting smaller and smaller, all approaching 410 m in recent years. The results show that depth convergence is related to the variation of AIW potential density in the Canada Basin. [ABSTRACT FROM AUTHOR]

We monitored variation in seasonal and annual net ecosystem production (NEP), gross primary production (GPP), and ecosystem respiration ( R) based on 7-year eddy covariance measurements above a cool-temperate deciduous broad-leaved forest (Japanese beech forest). The 7-year means (±SD) of annual NEP, GPP, and R were 312 ± 64, 1250 ± 62, and 938 ± 36 g C m year, respectively. Variation in NEP was much larger than variation in GPP and R. During the growing season, the main factor controlling carbon balance was air temperature; variation in seasonal integrated NEP was regulated by accumulated air temperature (degree-day) with a significant negative correlation, whereas the seasonal ratio of R to GPP was correlated positively with accumulated air temperature. Because the deviation of seasonal NEP was also significantly correlated with seasonal R/GPP, NEP was controlled by R/GPP, depending on air temperature during the growing season. Seasonal R in the defoliation and snow seasons was also important for evaluating the annual carbon balance, because the total number of days in the two seasons was quite large owing to a long snowy winter. In the defoliation and snow seasons, we found defoliation season length was a major factor determining seasonal integrated R, illustrating the positive correlation between R and defoliation season length. The major factors controlling interannual variations in forest carbon balance are discussed. [ABSTRACT FROM AUTHOR]

Active rock glaciers are permafrost landforms in high relief terrain moving slowly downward. Despite the fact that the movement of a rock glacier is influenced by site specific factors (e.g. slope, bedrock topography), climate and thereby mainly temperature are of main importance for surface flow velocity and its changes over time. However, establishing statistical significant correlations between climatic parameters and interannual variations in velocity is difficult and was hardly attempted because physical processes linking climate to rock glacier dynamics are complex and act at various spatial and temporal scale. In this study we compared rock glacier velocity data with different climatic parameters at three rock glaciers in the Hohe Tauern Range, Central Austria. Our study is based on annual geodetic field campaigns (maximum time span 1995-2011) with complementary data from aerial photogrammetric measurements covering up to 57 years totally. The three time series are some of the longest for the European Alps, therefore provide valuable insight into rock glacier velocity changes. Furthermore, continuous ground surface (maximum 10 years of data) and near ground-surface temperature (maximum 5 years) from the three rock glaciers, air temperature data from two meteorological stations, and complementary climate data from an official meteorological observatory were used. Results show that rock glacier velocities between the mid-1950s and mid-1990s were lower compared to the period afterwards. Either the time spans 2003-2004 or 2010- 2011 was the fastest period with velocities about 1.5 to 3.2 times faster compared to the minimums in the last 57 years. Intercomparison of the three velocity time series showed strong correlations also revealing six different main phases: low velocities in the mid-1990s, faster velocities at the end of the 1990s, low velocities in 1999-2000, steady increase in velocity peaking in 2003-2004, steady deceleration in velocities until 2007-2008, and steady but rather fast increase until 2011. Comparison with air temperature data revealed a time lag of one to more years for acceleration caused by warm air temperatures. In contrast, strong cooling causes a slightly faster deceleration possibly related to the availability of liquid water within the rock glacier. Correlation analysis of rock glacier velocity with 13 different climatic parameters revealed that the interrelationships are complex. Only 13 out of 270 pairs of variables correlated statistically significant. Results showed for instance that a four-times milder winter measured at the ground surface causes an increase in velocity by 1.5 times. In contrast, an only two-times milder winter measured at one meter depth causes also an acceleration of 1.5 times indicating different influences of the temperature at the surface or at one meter depth to velocities. Furthermore, a warming of the mean annual ground temperature at one meter depth by only 1°C from -2°C to -1°C increases velocity by 1.5 times. All three studied rock glacier fronts are close to the local lower limits of permafrost. Therefore, the inversion from velocity increase due to warming of permafrost to decrease due to substantial thawing of permafrost will possibly occur in this century, a plausible hypothesis for many other rock glaciers in Austria. [ABSTRACT FROM AUTHOR]

The eight datasets of the summer (June-August) surface sensible heat (SH) flux over the Tibetan Plateau (TP) are compared on the time scales of the climatology, interannual variability and linear trend during 1980-2006. These data sets include five reanalyses (National Center for Environmental Prediction reanalysis, NCEPR1 and NCEPR2, NCEP climate forecast system reanalysis, CFSR, Japanese 25-year reanalysis, JRA, and European Centre for Medium Range Weather Forecasts reanalysis, ERA40), two land surface model outputs (Noah model data of Global Land Data Assimilation System version 2, G2_Noah, and Simple Biosphere version 2 output by Yang et al., YSiB2), and estimated SH based on China Meteorological Administration (CMA) station observations, ObCh. The results suggest that the summer SH on the TP differs from one dataset to another due to different inputs and calculations. Climatologically, the ERA40 and JRA distribute rather uniformly while the other six products show similar regional disparities, that is, larger in the west than in the east and stronger in the north and the south than in the middle of the plateau. The mean magnitude of the SH averaged over the 76 stations above the TP varies considerably among each dataset with the difference of more than 20 W m between the maximum (G2_Noah) and minimum (ObCh). Nevertheless, they are consistent in the interannual variability and mostly show a significant decreasing trend corresponding to the weakening surface wind speed, in spite of the distinct trend for the ground-air temperature difference among the different data sets. These two consistencies indicate the particular availability of the SH products, which is helpful to the relevant climate dynamics research. [ABSTRACT FROM AUTHOR]

Recent (2007-2010) research results about ocean's role in climate variation and change by Chinese scientists are highlighted. This paper reviews a majority contributions by Chinese scientists to the understanding of ocean variability and change. This paper starts with the results about the important role of the tropical Indian Ocean in interannual variation of the Asia summer monsoon, the effect of sea surface temperature (SST) and freshwater flux on climate variability in the Pacific, and interannual variability research in other oceans. Then results about ocean dynamic and thermodynamic roles in decadal climate variation are reviewed. Finally, the results about oceanic response to global warming are discussed, again showcasing ocean's important role in climate. [ABSTRACT FROM AUTHOR]

El Niño-Southern Oscillation (ENSO) and local sea surface temperature (SST) have been regarded as the important factors influencing the precipitation, evaporation and circulation over the Asian-Australian monsoon (AAM) region. The moisture source is determined directly by precipitation and evaporation. This present paper studies the impacts of ENSO and local SST on moisture source in the AAM region during boreal summer. Relative roles of ENSO and local SST are also discussed by using the singular value decomposition (SVD) and conditional SVD (CSVD) methods. The authors identify one major coupled mode between the interannual variations of apparent moisture sink () and SST for the period 1979–2008. Spatial structure of the major mode exhibits two key regions of moisture source, one over the western-central southern Indian Ocean (SIO) where is negative, and the other over the northwest and north side of Australia, where is positive. In the corresponding map of SST, negative values are also seen in the former region, but are positive in the latter region. The interannual variation of moisture source in the AAM region has an outstanding positive correlation with the local SST. Furthermore, ENSO also has a remarkable correlation with the principle component (PC) of the first empirical orthogonal function (EOF) mode of . ENSO and local SST work cooperatively to determine the variations of moisture source in the AAM region. [ABSTRACT FROM AUTHOR]

One of the strongest El Niño events on record took place in the tropical Pacific in 1997–1998, causing remarkable changes in monsoon systems over the South China Sea (SCS) basin. This would induce prominent anomalies in the SCS upper layer circulation. The monsoon anomalies and the response of the upper layer circulation over the SCS during the 1997–1998 El Niño event are examined through data analysis and ocean numerical modeling, respectively. The winter monsoon and summer monsoon show southerly wind anomalies and northeasterly wind anomalies respectively during 1997/98 El Niño event, which was a reversal of the climatology. In contrast to climatology, the weakening of the winter monsoon does not change the upper layer circulation pattern, but causes a prominent change in the strength of the western boundary current. Corresponding to the anomalies of the summer monsoon, the upper layer circulation shows changes not only in magnitude, but also in structure from the climatology. The changes of the structure lie in the bifurcation of the western boundary current. [ABSTRACT FROM AUTHOR]

The effects of air-sea coupling over the tropical Indian Ocean (TIO) on the eastward- and northward-propagating boreal summer intraseasonal oscillation (BSISO) are investigated by comparing a fully coupled (CTL) and a partially decoupled Indian Ocean (pdIO) experiment using SINTEX-F coupled GCM. Air-sea coupling over the TIO significantly enhances the intensity of both the eastward and northward propagations of the BSISO. The maximum spectrum differences of the northward- (eastward-) propagating BSISO between the CTL and pdIO reach 30% (25%) of their respective climatological values. The enhanced eastward (northward) propagation is related to the zonal (meridional) asymmetry of sea surface temperature anomaly (SSTA). A positive SSTA appears to the east (north) of the BSISO convection, which may positively feed back to the BSISO convection. In addition, air-sea coupling may enhance the northward propagation through the changes of the mean vertical wind shear and low-level specific humidity. The interannual variations of the TIO regulate the air-sea interaction effect. Air-sea coupling enhances (reduces) the eastward-propagating spectrum during the negative Indian Ocean dipole (IOD) mode, positive Indian Ocean basin (IOB) mode and normal years (during positive IOD and negative IOB years). Such phase dependence is attributed to the role of the background mean westerly in affecting the wind-evaporation-SST feedback. A climatological weak westerly in the equatorial Indian Ocean can be readily reversed by anomalous zonal SST gradients during the positive IOD and negative IOB events. Although the SSTA is always positive to the northeast of the BSISO convection for all interannual modes, air-sea coupling reduces the zonal asymmetry of the low-level specific humidity and thus the eastward propagation spectrum during the positive IOD and negative IOB modes, while strengthening them during the other modes. Air-sea coupling enhances the northward propagation under all interannual modes due to the persistent westerly monsoon flow over the northern Indian Ocean. [ABSTRACT FROM AUTHOR]

Using National Centers for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) reanalysis data and monthly Hadley Center sea surface temperature (SST) data, and selecting a representative East Asian winter monsoon (EAWM) index, this study investigated the relationship between EAWM and East Asian summer monsoon (EASM) using statistical analyses and numerical simulations. Some possible mechanisms regarding this relationship were also explored. Results indicate a close relationship between EAWM and EASM: a strong EAWM led to a strong EASM in the following summer, and a weak EAWM led to a weak EASM in the following summer. Anomalous EAWM has persistent impacts on the variation of SST in the tropical Indian Ocean and the South China Sea, and on the equatorial atmospheric thermal anomalies at both lower and upper levels. Through these impacts, the EAWM influences the land-sea thermal contrast in summer and the low-level atmospheric divergence and convergence over the Indo-Pacific region. It further affects the meridional monsoon circulation and other features of the EASM. Numerical simulations support the results of diagnostic analysis. The study provides useful information for predicting the EASM by analyzing the variations of preceding EAWM and tropical SST. [ABSTRACT FROM AUTHOR]

A singular value decomposition (SVD) analysis is carried out to reveal the relationship between the interannual variation of track and intensity of the western North Pacific tropical cyclones (WNPTCs) in the tropical cyclone (TC) active season (July-November) and the global net airsea heat flux ( Q) in the preceding season (April-June). For this purpose, a tropical cyclone track and intensity function (TIF) is defined by a combination of accumulated cyclone energy (ACE) index and a cyclone track density function. The SVD analysis reveals that the first mode is responsible for the positive correlation between the upward heat flux in the tropical central Pacific and the increased activity of western North Pacific (WNP) TIF, the second mode for the positive correlation between the upward heat flux in the North Indian Ocean and the northeastward track shift of WNPTCs and the third mode for the negative correlation between the upward heat flux in mid-latitude central Pacific and the northwest displacement of the WNP TC-active center. This suggests that Q anomalies in some key regions have a substantial remote impact on the WNP TC activity. [ABSTRACT FROM AUTHOR]

In southern African savannas, grass production, and therefore the annual extent of fire, is highly dependent on rainfall. This response has repeatedly been noted in the literature but authors used different input variables and modelling approaches and the results are not comparable. Using long-term fire occurrence data from six protected areas in southern Africa we tested various methods for determining the relationship between antecedent rainfall and burned area. The types of regression model, the most appropriate index of accumulated rainfall, and the period over which to calculate annual burned area were all investigated. The importance of accumulating rainfall over more than one growing season was verified in all parks - improving the accuracy of the models by up to 30% compared with indices that only used the previous year's rainfall. Up to 56% of the variance in burned area between years could be explained by an 18-month accumulated rainfall index. Linear models and probit models performed equally well. The method suggested in this paper can be applied across southern Africa. This will improve our understanding of the drivers of interannual variation in burned area in this globally important fire region. [ABSTRACT FROM AUTHOR]

Abstract: The sensitivity of the Indian summer monsoon rainfall (ISMR) and its interannual variation (IAV) to model time step is investigated using NCAR-Community Atmosphere Model version 3 (CAM3). A set of multiyear numerical experiments is performed using the atmospheric model inter-comparison project (AMIP) protocol with observed sea surface temperature (SST). The default value of time step for 64×128 horizontal resolution with semi-Lagrangian dynamical core is 60min. The model overestimates the mean and underestimates the standard deviation. The mean and standard deviation of ISMR systematically decrease with decrease of time step size. With respect to observations, the mean becomes more reasonable but standard deviation becomes less reasonable. There is a decrease in precipitation over the Saudi Arabia, Maritime Continent, and northwestern Arabian Sea with decrease in time step, while over the Eastern Indian Ocean, Eastern Arabian Sea, and Eastern Bay of Bengal there is an increase in precipitation. The pattern correlation of precipitation with observation systematically increases with decrease of time step. In regard to the IAV of ISMR, simulation with 20min time step outperforms the other time steps i.e. 60, 40, 30, and 05min. When it is decreased to 20min, the model bias in precipitation climatology is reduced and the low-level westerly jet over the Indian peninsular becomes more realistic. There is an overall improvement in the climatology of rainfall and winds in the vicinity of Indian summer monsoon region with 20min time step. [Copyright &y& Elsevier]

Summer rainfall is vital for crops in Northeast China. In this study, we investigated large-scale circulation anomalies related to monthly summer rainfall in Northeast China using European Center for Medium-Range Weather Forecast ERA-40 reanalysis data and monthly rainfall data from 79 stations in Northeast China. The results show that the interannual variation in rainfall over Northeast China is mainly dominated by a cold vortex in early summer (May-June) and by the East Asian summer monsoon in late summer (July-August). In early summer, corresponding to increased rainfall in Northeast China, an anomalous cyclonic anomaly tilted westward with height appears to the northwest and cold vortices occur frequently. In late summer, the rainfall anomaly is mainly controlled by a northward shift of the local East Asian jet stream in the upper troposphere and the northwest extension of the western Pacific subtropical high (WPSH) in the lower troposphere. The enhanced southwesterly anomaly in the west of the WPSH transports more moisture into Northeast China and results in more rainfall. In addition, compared with that in July, the rainfall in Northeast China in August is also influenced by a mid- and high-latitude blocking high over Northeast Asia. [ABSTRACT FROM AUTHOR]

Intraseasonal oscillation (ISO) of rainfall during the summer monsoon season (June-August) and its plausible effect on interannual variation (IAV) of total summer monsoon rainfall over Bangladesh are examined using daily rainfall data from 25 rain-gauge stations for 20 years (1981-2000). Submonthly scale (7-25 days) ISO is a dominant mode of summer rainfall fluctuation over Bangladesh. In the active (suppressed) ISO phases, a cyclonic (anticyclonic) circulation anomaly develops at the low-level troposphere from northeastern India to Bangladesh, and an anticyclonic (cyclonic) circulation anomaly appears over the Bay of Bengal, accompanied by the enhancement of westerly/southwesterly (easterly/southeasterly) moisture flux anomalies over Bangladesh. The IAV of total summer monsoon rainfall is significantly correlated with that of the rainfall variance, mainly in the submonthly scale, suggesting that the ISO activity controls the IAV of the total summer monsoon rainfall. Moreover, the spatial patterns of atmospheric circulation and convection associated with the ISO and the IAV are quite similar to each other around the monsoon trough, especially from northeastern India to Bangladesh. In wet monsoon years, more frequent strong submonthly scale ISOs and a larger number of rainy days related to the active ISO phase are evident compared with that of dry monsoon years. Climatologically, Bangladesh is one of the most predominant areas of submonthly scale ISO; however, 30-60-day ISO is not prominent. These characteristic features probably allow the submonthly scale ISO to modulate the total seasonal rainfall and the spatial patterns of circulation and convection over and near Bangladesh. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The interannual variations of the early summer South China monsoon rainfall (SCMR) in relation to different Pacific Decadal Oscillation (PDO) backgrounds are examined using station rainfall data and the European Centre for Medium-range Weather Forecasts (ECMWF) 40-year reanalysis (ERA-40) data. The objective of this study is to investigate the atmospheric circulation patterns responsible for such variations, thereby understanding the interdecadal modulation and the cause for the extreme wet and dry SCMR. The interannual SCMR variance shows an interdecadal change before and after the late 1970s, with significant differences in sea-surface temperature (SST) and atmospheric circulation anomalies between the negative (1958-1976) and positive (1980-1998) PDO epochs. The dominant atmospheric teleconnection patterns associated with extreme wet and dry SCMR are remarkably different in these two epochs. During 1958-1976, an anomalous wet (dry) SCMR is characterized by a significantly anomalous anticyclone (cyclone) over the South China Sea (SCS) and western Pacific in the lower troposphere in the form of a meridional wave-like coupling along the coast of western North Pacific in the early summer, and preceded by a monopole circulation anomaly over the Ural Mountain in the preceding winter. During 1980-1998, however, an anomalous wet (dry) SCMR features a relatively weak anomalous anticyclone (cyclone) over the SCS in the low level without a significantly meridional juxtaposition of anomalous circulations in the early summer, and it follows a remarkable coherent long wave train pattern in middle-high latitudes in the preceding winter. Such interdecadal differences in anomalous circulation structures suggest that the relative roles of internal atmospheric variability and external forcing may be different from different epochs. But for both epochs, the circulation anomaly over the Ural Mountain shows a highly negative correlation with anomalous SCMR, suggesting that the winter circulation anomaly around the Ural Mountain is of great significance for improving the seasonal prediction of SCMR. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The low-frequency variability of the North Equatorial Current (NEC) bifurcation during 1958 to 2001 was investigated with the Simple Ocean Data Assimilation (SODA) 2.0.2 dataset. In agreement with recent observations, the NEC bifurcation latitude (NBL) shifted northward as depth increases, from about 12.7°N near the surface to about 17.1°N at depths around 500 m for the annual average. This study reveals that the interannual variations of NBL, with five years period, mainly focused on the upper 500 m with amplitude increasing as depth increased. The NBL shifted southward in the past 40 years, which was more significant in the subsurface at more than −0.02°/a. The NBL manifests itself in the transports of NMK (NEC-Mindanao Current (MC)-Kuroshio) system in strong relationship with MC (0.7) and Kuroshio (−0.7). The EOF analysis of meridional velocity off the Philippine coast shows that the first mode, explaining 62% of variance and 5 years period, was highly correlated with the southward shift of NBL with coefficient at about 0.75. The southward shift of NBL consists with the weakening of MC and strengthening of Kuroshio, which exhibited linear trends at −0.24Sv/a and 0.11Sv/a. Both interannual variation and trend of NBL were closely related to the variation of NMK system. [ABSTRACT FROM AUTHOR]

Despite increasing interest in the patterns of trace gas emissions in terrestrial ecosystems, little is known about the impacts of climate change on nitrous oxide (NO) fluxes. The aim of this study was to determine the importance of the three main drivers of climate change (warming, summer drought, and elevated CO concentrations) on NO fluxes from an extensively managed, upland grassland. Over a 2-year period, we monitored NO fluxes in an in situ ecosystem manipulation experiment simulating the climate predicted for the study area in 2080 (3.5°C temperature increase, 20% reduction in summer rainfall and atmospheric CO levels of 600 ppm). NO fluxes showed significant seasonal and interannual variation irrespective of climate treatment, and were higher in summer and autumn compared with winter and spring. Overall, NO emissions showed a positive correlation with soil temperature and rainfall. Elevated temperature had a positive impact on mean annual NO fluxes but effects were only significant in 2007. Contrary to expectations, neither combined summer drought and warming nor the simultaneous application of elevated atmospheric CO concentrations, summer drought and warming had any significant effect on annual NO fluxes. However, the maximum NO flux rates observed during the study occurred when elevated CO was combined with warming and drought, suggesting the potential for important, short-term NO-N losses in enriched CO environments. Taken together, our results suggest that the NO responses of temperate, extensively managed grasslands to future climate change scenarios may be primarily driven by temperature effects. [ABSTRACT FROM AUTHOR]

The Baiu frontal activity (BFA) clearly shows spatiotemporal differences in its interannual variability. This work examines the physical mechanisms behind these differences. On interannual time scales, the Baiu front can be divided into three subregions: (1) the western Baiu (WB), (2) the central Baiu (CB), and (3) the eastern Baiu (EB). Time series analysis revealed that the dominant periods in these three subregions are long eastward periods of approximately 2 years in the WB, 4 years in the CB, and 6 years in the EB. The biennial oscillation of the Asian monsoon controls the interannual variation in the WB through specific meridional circulation in the western North Pacific, whereas the El Niño/Southern Oscillation forces the interannual variation in the CB through the Pacific-East Asian teleconnection. The interannual variation in the EB is controlled by mid-latitude atmospheric circulations, not by effects from the Tropics. The summertime North Atlantic Oscillation (SNAO) with a 6-year period excites the stationary Rossby waves, the energies of which reach Japan through the strong upper tropospheric westerlies over Eurasia. Geopotential height anomalies then appear around Japan with an equivalent barotropic structure that modifies the precipitation in the EB. Copyright © 2009 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Spatiotemporal characteristics of interannual temperature variations in the Tsushima Strait are investigated on the basis of historical hydrographic data applying the same procedures as Senjyu et al. (2006). Empirical orthogonal function (EOF) analysis revealed that the most energetic mode of variation (the EOF first mode), which accounts for about 31.5% of the total variance, is the in-phase temperature change for the entire strait. The wintertime temperature variation described by the first mode is associated with the wintertime heat flux in the northern East China Sea, while they are poorly correlated in other seasons. The large standard deviation in the time coefficient of the first mode in August suggests a relationship with the horizontal heat advection in summer in the northern East China Sea. On the other hand, the EOF second mode, which explains about 12.6% of the total variance, is associated with the stratification and baroclinicity in the strait. The time coefficient of the EOF second mode negatively correlates with the baroclinic volume transport through the strait in summer. Comparison of temporal variations among the leading EOF modes for temperature and salinity shows no significant correlations. This indicates that the principal modes of variation in temperature and salinity vary independently within an interannual timescale. [ABSTRACT FROM AUTHOR]

We use eddy covariance measurements of net ecosystem productivity (NEP) from 21 FLUXNET sites (153 site-years of data) to investigate relationships between phenology and productivity (in terms of both NEP and gross ecosystem photosynthesis, GEP) in temperate and boreal forests. Results are used to evaluate the plausibility of four different conceptual models. Phenological indicators were derived from the eddy covariance time series, and from remote sensing and models. We examine spatial patterns (across sites) and temporal patterns (across years); an important conclusion is that it is likely that neither of these accurately represents how productivity will respond to future phenological shifts resulting from ongoing climate change. In spring and autumn, increased GEP resulting from an 'extra' day tends to be offset by concurrent, but smaller, increases in ecosystem respiration, and thus the effect on NEP is still positive. Spring productivity anomalies appear to have carry-over effects that translate to productivity anomalies in the following autumn, but it is not clear that these result directly from phenological anomalies. Finally, the productivity of evergreen needleleaf forests is less sensitive to phenology than is productivity of deciduous broadleaf forests. This has implications for how climate change may drive shifts in competition within mixed-species stands. [ABSTRACT FROM AUTHOR]

Abstract: In extra-Andean Patagonia, wet meadows contrast with the prevailing arid steppes, and present a gradient of water availability from the periphery to the center. The objectives of this paper are to describe the spatial and temporal variation of aerial net primary production (ANPP) of Patagonian meadows, and to obtain a model for the relationship between the normalized difference vegetation index (NDVI) and ANPP. We determined ANPP in four regionally scattered meadows during 3–5 years and in three positions of the gradient of water availability. In one meadow, we correlated ANPP with NDVI during 2 years. Annual ANPP was 2–3 times larger in the center than in the periphery, and also varied 2–3 fold among the four meadows. The interannual variation of ANPP was high and similar across meadows and zones. ANPP was closely correlated with NDVI through a linear model. Within the growing season, the central zone had a more extended period of high NDVI into the summer than the peripheral and the intermediate zones. We conclude that (1) the local variation of ANPP across the gradient of water availability is strong and must be taken into account for management, and (2) the highly variable ANPP may be monitored by remote sensing. [Copyright &y& Elsevier]

Future climate scenarios predict simultaneous changes in environmental conditions, but the impacts of multiple climate change drivers on ecosystem structure and function remain unclear. We used a novel experimental approach to examine the responses of an upland grassland ecosystem to the 2080 climate scenario predicted for the study area (3.5°C temperature increase, 20% reduction in summer precipitation, atmospheric CO levels of 600 ppm) over three growing seasons. We also assessed whether patterns of grassland response to a combination of climate change treatments could be forecast by ecosystem responses to single climate change drivers. Effects of climate change on aboveground production showed considerable seasonal and interannual variation; April biomass increased in response to both warming and the simultaneous application of warming, summer drought, and CO enrichment, whereas October biomass responses were either non-significant or negative depending on the year. Negative impacts of summer drought on production were only observed in combination with a below-average rainfall regime, and showed lagged effects on spring biomass. Elevated CO had no significant effect on aboveground biomass during this study. Both warming and the 2080 climate change scenario were associated with a significant advance in flowering time for the dominant grass species studied. However, flowering phenology showed no significant response to either summer drought or elevated CO. Species diversity and equitability showed no response to climate change treatments throughout this study. Overall, our data suggest that single-factor warming experiments may provide valuable information for projections of future ecosystem changes in cool temperate grasslands. [ABSTRACT FROM AUTHOR]

Interannual variation in experimental field conditions produce variability in the results of experiments monitored over multiple years, termed here “year effects.” When experimental treatments are replicated in separate years, interannual variation may influence treatment effects and produce significant treatment by initiation-year interactions. Understanding the frequency and strength of these effects requires initiating identical experiments across years. We conducted a review of literature covering more than 500 experimental articles published in 7 journals between 1966 and 2008. Only 5% of the 276 general ecological field studies initiated experiments in multiple years. This rarity was even more evident in the journal Restoration Ecology, in which none of the 173 surveyed experimental studies initiated experiments in multiple years. In contrast, 48% of the 58 field experiments published in an agronomy journal were replicated across years. We found only 17 studies that tested treatment by initiation-year interactions. Despite their rarity, 76% of these studies found significant interactions between treatment and initiation year. We conclude that the results of many ecological field experiments are likely to be contingent on the year in which they are implemented. We discuss the importance of treatment by initiation-year interactions in ecology and restoration, factors that have hindered the inclusion of temporal replication in the past, and some suggestions for the appropriate design and analysis of temporally replicated experiments. We argue for more deliberate investigation of temporal contingency in ecological experimentation, especially in the field of restoration ecology, which may be particularly sensitive to treatment by initiation-year interactions. [ABSTRACT FROM AUTHOR]

In southern African savannas, grass production, and therefore the annual extent of fire, is highly dependent on rainfall. This response has repeatedly been noted in the literature but authors used different input variables and modelling approaches and the results are not comparable. Using long-term fire occurrence data from six protected areas in southern Africa we tested various methods for determining the relationship between antecedent rainfall and burned area. The types of regression model, the most appropriate index of accumulated rainfall, and the period over which to calculate annual burned area were all investigated. The importance of accumulating rainfall over more than one growing season was verified in all parks - improving the accuracy of the models by up to 30% compared with indices that only used the previous year's rainfall. Up to 56% of the variance in burned area between years could be explained by an 18-month accumulated rainfall index. Linear models and probit models performed equally well. The method suggested in this paper can be applied across southern Africa. This will improve our understanding of the drivers of interannual variation in burned area in this globally important fire region. [ABSTRACT FROM AUTHOR]

Abstract: The SODA product is used to investigate three Indonesian throughflow (ITF) branches: the flow through the Makassar Strait; through the South China Sea; and through the eastern Indonesian basins. The results reveal strong interannual variation in the Makassar Strait and the eastern Indonesian basins throughflow. Inspection of vertically integrated dynamic height (0–1000db), a proxy of transport function, suggests that this interannual variation can be traced to the New Guinea Coastal Current, indicative of a strong influence of the South Pacific. The vertically integrated dynamic height along the south Java coast is related to variation in the North Pacific and in particular near the east coast of Mindanao Island, whereas the vertically integrated dynamic height along the coast of West Australia is related to variation in the South Pacific, and in particular near the coast of New Guinea. The integrated dynamic height difference between the Java and New Guinea coast appears to be a good proxy of ITF transport on the interannual time scale. Regression analysis shows a phase dependence of the three ITF pathways on the Nino3.4 index. Decoupling of current anomalies between the surface and subsurface layers is identified in the developing and mature phase of El Nino, reflecting different effects of local and remote forcing through oceanic pathways at the Makassar Strait and eastern Indonesian basins. [Copyright &y& Elsevier]

The article presents a study which examines the changes of rainy season in the Philippines from 1961 to 2000. The study uses empirical orthogonal function (EOF) analysis to rainfall data to determine the spatial and temporal structures of interannual difference in the seasonal march of rainfall. The result shows that a contrast in seasonal marches of rainfall between the west and the east coastal region are due to the east-northeasterly wind and the west-southwesterly wind.

Climate change is known to influence interannual variation in grassland aboveground net primary productivity (ANPP), or seasonal biomass, but direct, long-term ground observations are rare. We present a 22-year (1982–2003) measurement series from the Inner Mongolia grassland, China, to examine the effect of climate change on interannual variations in ANPP and monthly aboveground biomass (MAB). ANPP exhibited no increase over 1982–2003 but there was an association with previous-year precipitation. MAB in May increased by 21.8% from 47.8 g m−2 (averaged for 1982–1984) to 58.2 g m−2 (2001–2003), whereas there was no significant variation in June, July and August, and a decrease of 29.7% in September. The MAB increase in May was correlated with increases in precipitation and temperature in the preceding months. These findings suggest that the effects of climate change on grassland production vary throughout the growing season, with warmer and wetter springs resulting in increased biomass early in the growing season, and drier falls causing a decrease in biomass late in the growing season. [ABSTRACT FROM AUTHOR]

Defining the intensity of the East Asian winter monsoon (EAWM) with a simple index has been a difficult task. This paper elaborates on the meanings of 18 existing EAWM strength indices and classifies them into four categories: low level wind indices, upper zonal wind shear indices, east-west pressure contrast indices, and East Asian trough indices. The temporal/spatial performance and prediction potential of these indices are then analyzed for the 1957–2001 period. It reveals that on the decadal timescale, most indices except the east-west pressure contrast indices can well capture the continuous weakening of the EAWM around 1986. On the interannual timescale, the low level wind indices and East Asian trough indices have the best predictability based on knowledge of the El Niño-Southern Oscillation and Arctic Oscillation, respectively. All the 18 existing indices can well describe the EAWM-related circulation, precipitation, and lower tropospheric air temperature anomalies. However, the variations of surface air temperature over large areas of central China cannot be well captured by most indices, which is possibly related to topographic effects. The results of this study may provide a possible reference for future studies of the EAWM. [ABSTRACT FROM AUTHOR]

Reconstruction of evenly-spaced, regular time series from routine survey serial data was investigated for precise analysis of spatio-temporal variations in a temperate sea at mid-latitudes where the seasonality dominates the interannual variability. Considering that the annual range of sea surface temperature in the Yellow Sea and the northwestern East China Sea can be as large as 15–20 °C, temperature data collected bi-monthly in these temperate seas were used for the assessment of reconstruction methodology. The cubic spline interpolation with a sampling interval of 0.5 months reconstructed the regular time series closest to the in-situ measurements among various interpolation schemes. Also, two computation methods for the interannual anomaly were compared; the residual method that the long-term monthly means are subtracted from the monthly serial data and the filtering method that high-frequency variations are removed using a low-pass filter. In that the high-frequency variations in frequencies greater than 1 cycle per year are comparable in magnitude to the interannual variation, the residual method proves inadequate in the temperate sea. High-frequency noises can be effectively removed through the use of a proper low-pass filter with bell-shaped weights. [ABSTRACT FROM AUTHOR]

Grassland is the largest terrestrial ecosystem in China. It is of great significance to measure accurately the soil respiration of different grassland types for the contribution evaluation of the Chinese terrestrial ecosystem's carbon emission to the atmospheric CO concentration. A three-year (2005-2007) field experiment was carried out on three steppes of Stipa L. in the Xilin River Basin, Inner Mongolia, China, using a static opaque chamber technique. The seasonal and interannual variations of soil respiration rates were analyzed, and the annual total soil respiration of the three steppes was estimated. The numerical models between soil respiration and water-heat factors were established respectively. Similar seasonal dynamic and high annual and interannual variations of soil respiration were found in all of the three steppes. In the growing season, the fluctuation of soil respiration was particularly evident. The coefficients of variation ( CVs) for soil respiration in different growing seasons ranged from 54% to 93%, and the annual CVs were all above 115%. The interannual CV of soil respiration progressively decreased in the order of Stipa grandis ( S. grandis) steppe > Stipa baicalensis ( S. baicalensis) steppe > Stipa krylovii ( S. krylovii) steppe. The annual total soil respiration for the S. baicalensis steppe was 223.62-299.24 gC m a, 150.62-226.99 gC m a for the S. grandis steppe, and 111.31-131.55 gC m a for the S. krylovii steppe, which were consistent with the precipitation gradient. The variation in the best fitting temperature factor explained the 63.5%, 73.0%, and 73.2% change in soil respiration in the three steppes at an annual time scale, and the corresponding Q values were 2.16, 2.98, and 2.40, respectively. Moreover, the Q values that were calculated by soil temperature at different depths all expressed a 10 cm > 5 cm > surface in the three sampling sites. In the growing season, the soil respiration rates were related mostly to the surface soil moisture, and the 95.2%, 97.4%, and 93.2% variations in soil respiration in the three steppes were explained by the change in soil moisture at a depth of 0-10 cm, respectively. [ABSTRACT FROM AUTHOR]

Abstract: This study examined 11-year (1997–2008) weekly and monthly time series of satellite-observed ocean color to understand the dominant temporal and spatial patterns of chlorophyll-a in the southwest Atlantic sector of the Southern Ocean. Using empirical orthogonal function analysis and k-means classification, we classified the study area into eight regions, which were in good accordance with the oceanographic and topographic features. Examination of the chlorophyll-a time series in each region revealed that contrary to our expectation, regular seasonal phytoplankton blooms were observed only in a limited area. Of the eight regions, only two showed typical seasonal blooms, and one showed weak seasonality, whereas other regions exhibited irregular seasonal blooms of variable duration. We attribute the absence of regularity in seasonal blooms to relatively shallow winter mixing, which would prevent entrainment of limiting micronutrients such as iron and silicate. In the southwest Atlantic sector of the Southern Ocean, topographic effects and sea ice may be the most important factors controlling primary productivity. In the South Georgia region, chlorophyll-a showed a significant correlation with geostrophic current velocity, indicating that topographic effects depend on the interaction of current strength and topographic structure. Interannual variability of the surface chlorophyll in some regions also revealed longer periodicity (∼6 years). The periodicity seemed to be related to El Niño–Southern Oscillation and to sea-ice dynamics influenced by the Antarctic Circumpolar Current. [Copyright &y& Elsevier]

We measured the gas exchange and foliar terpene concentrations and terpene emission rates of Cistus albidus throughout the seasons of two annual periods (2003 and 2005) of contrasting precipitations (900 vs. 500 mm) and in response to experimental drought in a Mediterranean forest of southern Catalonia. C. albidus showed a typical seasonal oscillation of photosynthetic rates and stomatal conductance. Maximum photosynthetic activity appeared in the spring of the first year of the study and minimum ones in both summers. Net photosynthetic rates and stomatal conductance tended to decrease with drought treatment. In the first year, Cistus albidus presented maximum values of stored terpenes in autumn and winter and minimum values in spring and summer. Average concentrations in the first year were 154 and 96 μg g−1 dry matter (d.m.) for control and drought, respectively. Average concentrations in the second year were higher, 339 and 263 μg g−1 (d.m.) for control and drought, respectively. The most abundant terpene was zingiberene, followed by aromadendrene, germacrene, (−)-α-cedrene, and sesquiphellandrene. The drought treatment tended to decrease terpene content, but not significantly. Considering all the treatments together, total terpene emissions ranged between practically 0 (spring 2003) to 9 μg g−1 (d.m.) h−1 (winter 2003). In the second year, total terpene emission rates decreased 39% in control plants, and 29% in drought plants. Significant seasonal differences in emission rates were found. Total emission rates tended to be higher in the drought treatment, especially in spring and autumn. These results help for a better understanding of the behavior of plant volatiles in Mediterranean conditions interannualy and seasonally, an issue of great interest for forest flammability and atmospheric chemistry. [ABSTRACT FROM AUTHOR]