Seasonal Perspective Research Articles

Disaster Profile of India: A Theoretical Understanding of Regional and Seasonal Perspective

<em>India’s unique geo-climatic position makes India particularly vulnerable to natural disasters. The regional and seasonal profile of India has been presented in this paper. The main objective of this paper is to illustrate and explain the basic understanding of various natural disasters happening in various parts of India. In this paper regional profile of India is taken into consideration wherein stress has been given on various disasters happening all over the country as per geographical location of the area. Author also explains seasonal profile of India in which focus is given on the various seasons and disasters associated with each seasonal cycle. </em>

Dynamics of tropical–extratropical interactions and extreme precipitation events in Saudi Arabia in autumn, winter and spring

AbstractExtreme precipitation in the arid Middle East can cause flash floods with dramatic societal impacts. This study investigates the synoptic‐scale dynamics of three extreme precipitation events that occurred in Saudi Arabia in autumn, winter and spring. Using ERA‐Interim reanalysis, soundings and observational precipitation data, we study precipitation characteristics, the synoptic circulations, moisture transport pathways and forcing mechanisms for upward motion. All three cases involved strong tropical–extratropical interactions whereby midlatitude forcing instigated an incursion of tropical moisture over the Arabian Peninsula that fuelled the heavy rainfall. In each case, a midlatitude upper‐level trough, associated with anticyclonic Rossby wave breaking, intruded into the subtropics. The phase relationship between this trough and the tropical low‐level circulation was consistent with wave amplification through baroclinic growth. Eulerian and Lagrangian analyses reveal moisture transport from nearby and remote tropical regions, leading to above‐normal tropospheric moisture content over Saudi Arabia. The autumn case (November 2009) showed a transient midlatitude upper‐level trough that interacted with the climatological Red Sea Trough near the surface, being an ‘Active Red Sea Trough’ event. The winter case (January 2005) resembled tropical plume‐like characteristics and demonstrated the coupling of a midlatitude cyclone and the equatorial low‐pressure zone over Africa, an intensified subtropical jet stream, and pronounced moisture fluxes at middle and upper levels. The spring case (April–May 2013) involved a quasi‐stationary cut‐off low and persistent advection of low‐level moist air masses, partly from the south Indian Ocean through cross‐equatorial flow. The forcing of ascent was associated with low‐level moisture convergence and decreased static stability (autumn case), dynamical lifting (winter case), strong surface sensible heating (spring case), and orographic lifting (all cases), favouring the build‐up and release of potential instability. We discuss the three cases from a seasonal perspective and present a synthesis of their common key synoptic features.

Inter-annual variations and trends of the urban warming in Tehran

Urbanization is an extreme case of land-use change which amplifies in most cases the regional warming, and highly impacts a number of sensitive sectors, particularly human health. Using near-surface daily temperature records for a 63-yr period from 1951 to 2013, temperature changes over the urban city of Tehran were examined. Statistically significant warming trend of the order 0.37°C/decade has been observed, leading to 2.3°C rise over the entire 63-yr period, and the warming trend has been intensified in recent years. The observed warming in the urban city of Tehran has been more than triple the rate of change in the global average temperature, indicating that urbanization has had a significant warming effect. The nighttime warming (0.62°C/decade) in the urban city of Tehran was found to be more than three times greater than the daytime warming (0.17°C/decade), resulted in a decreasing trend in the diurnal temperature range (DTR; i.e. the difference between the daytime maximum and nighttime minimum temperatures). In a similar manner, a decreasing trend in the number of cold nights was identified, and the rate was more than twice as high as the rate of increase in the number of warm days. From a seasonal perspective, warming trends of the urban city of Tehran have been found to be nearly identical in winter and summer, with the rates of 0.35°C/decade and 0.33°C/decade, respectively. However, a seasonal cycle in the changes of the DTR was identified, with a stronger decrease rate in winter than summer because while the nighttime warming (which has been greater than the daytime warming) has not changed considerably from winter to summer, the daytime warming has been stronger in summer.

Coral reef fish assemblages along a disturbance gradient in the northern Persian Gulf: A seasonal perspective

Seasonal dynamics of coral reef fish assemblages were assessed along a gradient of potential anthropogenic disturbance in the Northern Persian Gulf. Overall, the attributes of coral reef fish assemblages showed seasonality at two different levels: seasonal changes irrespective of the magnitude of disturbance level (e.g. species richness), and seasonal changes in response to disturbance level (e.g. total abundance and assemblage composition). The examined parameters mostly belonged to the second group, but the interpretation of the relationship between patterns of seasonal changes and the disturbance level was not straightforward. The abundance of carnivorous fishes did not vary among seasons. SIMPER identified the family Nemipteridae as the major contributor to the observed spatiotemporal variations in the composition of coral reef fish assemblages in the study area.

Characteristics and sources of PM in seasonal perspective – A case study from one year continuously sampling in Beijing

Daily mass concentrations and chemical compositions (elemental carbon, organic carbon, water soluble ions, chemical elements and organic species) of PM were measured continuously in Beijing for one year from June 2010 to June 2011 (365 samples). The seasonal variation of PM mass concentration followed the order of spring 2011 > winter 2010 > summer 2010 > autumn 2010. Organic matter (OM) and secondary inorganic aerosol components (SNA: SO42−, NO3− and NH4+) were the two major fractions of PM during the whole year. Source apportionment by PMF performed on the basis of a full year of data, including both inorganic and organic species, showed that biomass burning, secondary sulfate and nitrate formation, mineral dust, industry, coal combustion and traffic were the main sources of PM in Beijing during 2010–2011. Specifically, comparison among the four seasons shows that the contribution of secondary sulfate and biomass burning, secondary nitrate formation, mineral dust, and coal combustion were the dominating sources of PM in summer, autumn, spring and winter, respectively. The contributions of industry to PM was distributed evenly in four seasons, while traffic contributed more in summer and autumn than in winter and spring. Backward trajectory analysis was applied in combination with PMF and showed that air flow from the South contributed mostly to high PM mass concentrations in Beijing. Meteorological parameters (temperature, wind speed, wind direction, precipitation and mixing layer height) influence such a variation. In general, high relative humidity and low mixing layer height can raise PM mass concentration, while high wind speed and precipitation can reduce pollutants. In addition, wind direction also plays a key role in influencing PM because different wind directions can bring different pollutants to Beijing from different regions.

Energy efficiency of a reversible refrigeration unit using R410A or R32

The aim of this article is twofold: first, to compare the performance of R410A with that of R32, which is considered a possible HFC substitute with lower global warming potential (675 instead of 2088); second, to exploit the effect of the circuit length in the finned coil of a packaged air-to-water reversible unit with given water plate heat exchanger and scroll compressor. Both scopes are pursued through the analysis of a case study, a system with nominal cooling capacity of about 74 kW at 35°C dry-bulb outdoor air temperature and a nominal heating capacity of about 70 kW at 2°C dry-bulb and 1°C wet-bulb ambient temperature. The performance of the two refrigerants inside a “real” machine is simulated by means of an advanced numerical model of a packaged reversible refrigeration unit. The system consists of a single refrigerating circuit with two identical scroll compressors. The compressor was characterized by its experimental performance curve according to Standard EN 12900 (EN 2013a) for both R410A and R32. Off-the-shelf copper tubes and louvered aluminum fins were considered for the condenser and typical brazed-plate heat exchanger for the evaporator of the chiller configuration. The finned coil heat exchanger was first thermodynamically optimized for R410A and R32 for both condenser and evaporator operation with regard to the number of internal circuits according to the total temperature penalization performance evaluation criteria (Cavallini et al. 2010; Brown et al. 2013), without changing the overall heat exchanger dimensions. The effect of finned coil circuit length on the performance of the investigated reversible unit with the two refrigerants was then analyzed at nominal design conditions and under a seasonal perspective. Based on the modeling work, it is possible to conclude that R32 system efficiency performance is acceptable as alternative to R410A for packaged air-to-water reversible unit.

On the assessment of aridity with changes in atmospheric CO2

AbstractA recent interpretation of climate model projections concluded that “warmer is more arid.” In contrast, dust records and other evidence have led the geoscience community to conclude that “warmer is less arid” leading to an aridity paradox. The “warmer is more arid” interpretation is based on a projected increase in the vapour pressure deficit (∼ 7–9% K−1) that results in a projected increase in potential evaporation that greatly exceeds the projected increase in precipitation. However, the increase in potential evaporation does not result in an increase in (actual) evaporation which remains more or less constant in the model output. Projected changes in the long‐term aridity can be assessed by directly interrogating the climate model output. To that end, we equate lack of precipitation with meteorological aridity and lack of runoff with hydrologic aridity. A third perspective, agro‐ecological aridity, is not directly related to the water lost but rather to the carbon gain and is equated with the reduction in photosynthetic uptake of CO2. We reexamine the same climate model output and conclude that “warmer is less arid” from all perspectives and in agreement with the geological records. Future research will need to add the critical regional and seasonal perspectives to the aridity assessments described here.

Long-term spatial and temporal variation of CO<sub>2</sub> partial pressure in the Yellow River, China

Abstract. Carbon transport in river systems is an important component of the global carbon cycle. Most rivers of the world act as atmospheric CO2 sources due to high riverine CO2 partial pressure (pCO2). By determining the pCO2 from alkalinity and pH, we investigated its spatial and temporal variation in the Yellow River watershed using historical water chemistry records (1950s–1984) and recent sampling along the mainstem (2011–2012). Except the headwater region where the pCO2 was lower than the atmospheric equilibrium (i.e. 380 μatm), river waters in the remaining watershed were supersaturated with CO2. The average pCO2 for the watershed was estimated at 2810 ± 1985 μatm, which is 7-fold the atmospheric equilibrium. As a result of severe soil erosion and dry climate, waters from the Loess Plateau in the middle reaches had higher pCO2 than that from the upper and lower reaches. From a seasonal perspective, the pCO2 varied from about 200 μatm to > 30 000 μatm with higher pCO2 usually occurring in the dry season and lower pCO2 in the wet season (at 73% of the sampling sites), suggesting the dilution effect of water. While the pCO2 responded exponentially to total suspended solids (TSS) export when the TSS concentration was less than 100 kg m−3, it decreased slightly and remained stable if the TSS concentration exceeded 100 kg m−3. This stable pCO2 is largely due to gully erosion that mobilizes subsoils characterized by low organic carbon for decomposition. In addition, human activities have changed the pCO2 dynamics. Particularly, flow regulation by dams can diversely affect the temporal changes of pCO2, depending on the physiochemical properties of the regulated waters and adopted operation scheme. Given the high pCO2 in the Yellow River waters, large potential for CO2 evasion is expected and warrants further investigation.

Combined influences of seasonal East Atlantic Pattern and North Atlantic Oscillation to excite Atlantic multidecadal variability in a climate model

The physical processes underlying the internal component of the Atlantic Multidecadal Variability (AMV) are investigated from a 1,000-yr pre-industrial control simulation of the CNRM-CM5 model. The low-frequency fluctuations of the Atlantic Meridional Overturning Circulation (AMOC) are shown to be the main precursor for the model AMV. The full life cycle of AMOC/AMV events relies on a complex time-evolving relationship with both North Atlantic Oscillation (NAO) and East Atlantic Pattern (EAP) that must be considered from a seasonal perspective in order to isolate their action; the ocean is responsible for setting the multidecadal timescale of the fluctuations. AMOC rise leading to a warm phase of AMV is statistically preceded by wintertime NAO+ and EAP+ from ~Lag −40/−20 yrs. Associated wind stress anomalies induce an acceleration of the subpolar gyre (SPG) and enhanced northward transport of warm and saline subtropical water. Concurrent positive salinity anomalies occur in the Greenland–Iceland–Norwegian Seas in link to local sea-ice decline; those are advected by the Eastern Greenland Current to the Labrador Sea participating to the progressive densification of the SPG and the intensification of ocean deep convection leading to AMOC strengthening. From ~Lag −10 yrs prior an AMOC maximum, opposite relationship is found with the NAO for both summer and winter seasons. Despite negative lags, NAO− at that time is consistent with the atmospheric response through teleconnection to the northward shift/intensification of the Inter Tropical Convergence Zone in link to the ongoing warming of tropical north Atlantic basin due to AMOC rise/AMV build-up. NAO− acts as a positive feedback for the full development of the model AMV through surface fluxes but, at the same time, prepares its termination through negative retroaction on AMOC. Relationship between EAP+ and AMOC is also present in summer from ~Lags −30/+10 yrs while winter EAP− is favored around the AMV peak. Based on additional atmospheric-forced experiments, both are interpreted as the local seasonal-dependent atmospheric response to warmer North Atlantic. Finally, advection of fresher water from the tropical basin created by local atmosphere/ocean anomalous circulation on one hand and from the Arctic on the other hand due to large-scale sea ice melting leads to decrease of density in the SPG and contributes terminating the model AMOC/AMV events. All together, the combined effects of NAO and EAP, their intertwined seasonal forcing/forced role upon/by the ocean and the primary role of salinity anomalies associated with oceanic dynamical changes acting as an integrator are responsible in CNRM-CM5 for an irregular and damped mode of variability for AMOC/AMV that takes about 35–40 (15–20) years to build up (dissipate).

Seasonal perspective of dietary arsenic consumption and urine arsenic in an endemic population

Exposure to arsenic in arsenic endemic areas is most remarkable environmental health challenges. Although effects of arsenic contamination are well established, reports are unavailable on probable seasonal variation due to changes of food habit depending on winter and summer seasons, especially for endemic regions of Nadia district, West Bengal. Complete 24-h diets, drinking-cooking water, first morning voided urine samples, and diet history were analyzed on 25 volunteers in arsenic endemic Chakdah block of Nadia district, once in summer followed by once in winter from the same participants. Results depicted no seasonal variation of body weight and body mass index. Arsenic concentration of source drinking and cooking water decreased (p = 0.04) from 26μgL(-1) in summer to 6μgL(-1) in winter season. We recorded a seasonal decrease of water intake in male (3.8 and 2.5Lday (-1)) and female (2.6 and 1.2Lday(-1)) participants from summer to winter. Arsenic intake through drinking water decreased (p = 0.04) in winter (29μgday(-1)) than in summer (100μgday(-1)), and urinary arsenic concentration decreased (p = 0.018) in winter (41μgL(-1)) than in summer (69μgL(-1)). Dietary arsenic intake remained unchanged (p = 0.24) over the seasons. Hence, we can infer that human health risk assessment from arsenic needs an insight over temporal scale.

Corrigendum to "Chemical characterization and source apportionment of PM<sub>2.5</sub> in Beijing: seasonal perspective" published in Atmos. Chem. Phys., 13, 7053–7074, 2013

Corrigendum to "Chemical characterization and source apportionment of PM<sub>2.5</sub> in Beijing: seasonal perspective" published in Atmos. Chem. Phys., 13, 7053–7074, 2013

Circadian adaptation to seasons: effects on activity behavior in subtropical House Sparrow, Passer domesticus

Birds use endogenous circadian clocks to regulate the wide array of functions. In the natural environment synchronized with day–night cycle, they exhibit these as daily rhythms in physiology and behavior. It is less understood, however, whether these daily rhythms have a seasonal perspective. We investigated this by measuring circadian clock governed activity behavior in House Sparrows (Passer domesticus) exposed to natural and artificial light–dark (LD) cycles at 27°N (Lucknow, India). Daily activity of Sparrows was recorded under natural daylight and temperature conditions (NDL) for ~11 months, beginning in late March. With more precise onsets than ends, Sparrows had varied daily activity pattern and duration between seasons. Further experiments investigated effect of seasons on circadian rhythm characteristics in Sparrows exposed to constant dim light (<1 lux) at different times of the year. The circadian rhythm period, activity pattern, and duration, but not the sensitivity of endogenous clock as shown by light-induced phase shifts, significantly varied over seasons. Also, resynchronization time (days) did not differ between seasons; although it was significantly longer to delay than to advance 6 h LD zeitgeber shifts. Thus, endogenous clock seems to closely correspond with environmental photoperiod in determining the daily activity behavior in House Sparrows.

Snow cover trend analysis using Interactive Multisensor Snow and Ice Mapping System data over Turkey

ABSTRACTThe daily snow cover data from Interactive Multisensor Snow and Ice Mapping System (IMS) by National Oceanic and Atmospheric Administration's National Environmental Satellite Data and Information Service (NOAA/NESDIS) covering the 2004–2012 time period is used in this study. In the first part of the study, daily IMS product is validated over Turkey using daily ground truth snow depth measurements from 219 climatological and synoptic sites. The categorical statistics of probability of detection (POD) and false alarm rates (FAR) are provided both for whole Turkey and with respect to geographical sub‐regions. The overall POD and FAR amounts for Turkey are obtained as 73.55 and 25.11%, respectively. The performed analysis indicates an increase in IMS accuracies as the snowpack depth at the stations increase. In the second part of the study, the nonparametric Mann‐Kendall test is performed to analyse the snow cover trend over Turkey with respect to sub‐regions considering the whole year and each season separately. A negative trend in snow‐covered area percentage is obtained for Turkey at the significance level of α = 0.05. From the seasonal perspective for Turkey, negative trend for spring and summer seasons, positive trend for autumn season and combination of negative and no trend for winter season are obtained at the same significance level. Almost the same results are valid for the sub‐regions with some local and seasonal variations.

Long-term trends and variability of rainfall extremes in the Philippines

Owing to the increasing concerns about climate change due to the recent extreme rainfall events in the Philippines, long-term trends and variability in rainfall extremes in the country are investigated using 60-year (1951–2010) daily rainfall data from 35 meteorological stations. Rainfall extremes are described using seven extreme precipitation indices (EPI) that characterize daily rainfall in terms of intensity, accumulation, and duration on a seasonal perspective. The nonparametric Mann–Kendall test is employed in combination with the moving blocks bootstrapping technique to detect significant trends in EPI. The results suggest a tendency toward a drying condition for the dry season, January–March (JFM), as indicated by statistically significant decreasing trends in seasonal wet days total rainfall (PCPTOT) associated with increasing trends in maximum length of dry spell (LDS). In contrast, statistically significant increasing trends in maximum 5-day rainfall (RX5day) and decreasing trends in LDS denote a wetting condition during the July–September (JAS) season, particularly at stations located in the northwest and central Philippines. The trends obtained are further assessed by examining the longer time series of EPI at four meteorological stations (Aparri, Dagupan, Iloilo, and Masbate) that have rainfall data from 1911 to 2010. The longer historical data revealed that the trends obtained in the shorter period (1951–2010) could either be consistent with the continuous long-term trends, as observed in RX5day during JAS at Aparri and Masbate, or represent interdecadal variability as was observed at Dagupan and Iloilo. The long-term (1911–2010) southwestward extension of the western North Pacific subtropical high associated with a weakening of the 850-hPa westerly wind over the South China Sea partly provides a possible cause of the trends in EPI during JAS, whereas the weakening of the East Asian winter monsoon contributed somewhat to the trends obtained during JFM. Furthermore, interannual variations in EPI are found to be influenced greatly by the El Niño–Southern Oscillation (ENSO). Composite analyses suggest that El Niño (La Niña) events are associated with statistically significant drier (wetter) conditions over the Philippines, especially during the seasons close to ENSO mature stage.

Chemical characterization and source apportionment of PM&amp;lt;sub&amp;gt;2.5&amp;lt;/sub&amp;gt; in Beijing: seasonal perspective

Abstract. In this study, 121 daily PM2.5 (aerosol particle with aerodynamic diameter less than 2.5 μm) samples were collected from an urban site in Beijing in four months between April 2009 and January 2010 representing the four seasons. The samples were determined for various compositions, including elements, ions, and organic/elemental carbon. Various approaches, such as chemical mass balance, positive matrix factorization (PMF), trajectory clustering, and potential source contribution function (PSCF), were employed for characterizing aerosol speciation, identifying likely sources, and apportioning contributions from each likely source. Our results have shown distinctive seasonality for various aerosol speciations associated with PM2.5 in Beijing. Soil dust waxes in the spring and wanes in the summer. Regarding the secondary aerosol components, inorganic and organic species may behave in different manners. The former preferentially forms in the hot and humid summer via photochemical reactions, although their precursor gases, such as SO2 and NOx, are emitted much more in winter. The latter seems to favorably form in the cold and dry winter. Synoptic meteorological and climate conditions can overwhelm the emission pattern in the formation of secondary aerosols. The PMF model identified six main sources: soil dust, coal combustion, biomass burning, traffic and waste incineration emission, industrial pollution, and secondary inorganic aerosol. Each of these sources has an annual mean contribution of 16, 14, 13, 3, 28, and 26%, respectively, to PM2.5. However, the relative contributions of these identified sources significantly vary with changing seasons. The results of trajectory clustering and the PSCF method demonstrated that regional sources could be crucial contributors to PM pollution in Beijing. In conclusion, we have unraveled some complex aspects of the pollution sources and formation processes of PM2.5 in Beijing. To our knowledge, this is the first systematic study that comprehensively explores the chemical characterizations and source apportionments of PM2.5 aerosol speciation in Beijing by applying multiple approaches based on a completely seasonal perspective.

Modelling potential effects of climate change on winter turbidity loading in the Ashokan Reservoir, NY

AbstractRecent studies have indicated that potential future climate change may lead to changes in the timing and quantity of snowpack accumulation and winter (November to April) streamflow patterns including increased streamflow and turbidity in early winter and a slight reduction in turbidity loads at the time of traditional early spring run‐off. In this study, we examine the potential effects of these predicted changes on reservoir turbidity levels. Our analysis focuses on Ashokan Reservoir, NY, which can at times receive significant watershed turbidity inputs mainly from stream channel erosion from the Esopus Creek. Both measured and simulated turbidity loads and climatology are input to CE‐QUAL‐W2 (W2), a reservoir turbidity transport model that can simulate reservoir turbidity and other water quality parameters. The W2 model is applied to estimate the effects of hydroclimatology on effective settling rates and turbidity transport as a result of differences in reservoir thermal structure during summer and winter events. Simulations suggest that the effective settling velocity is substantially lower at low temperatures during winter time. Winter average stream flow is simulated to increase by 12% and 20%, which leads to increases in reservoir turbidity by 11% and 17% for the future period 2046–2065 and 2081–2100, respectively. From a seasonal perspective, a change in timing of peak streamflow with increased flows during the winter and slightly reduced flows during early spring leads to increased average reservoir turbidity during winter and slightly decreased in‐reservoir turbidity during early spring and summer. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Distribution characteristics of hydraulic properties on a mountainous hillslope

Understanding the heterogeneity of infiltration has been a challenging issue in improving knowledge of hillslope hydrology. Spatial distributions of the hydraulic properties on a hillslope were measured using tension infiltrometers over four different time periods. The hillslope examined has a permanent channel initiation point located in the Bongsunsa watershed, which is a headwater for the Han River basin, South Korea. Surface hydraulic conductivity is affected by both pore development structure and soil texture. In order to explore the impact of the relationship between spatial topographical features and the surface hydraulic properties, several terrain analyses and flow evaluations were performed. The importance of flow through a larger pore size was confirmed in both the scale and variation of the spatial and seasonal perspectives, respectively. Although there is a substantial heterogeneity of field measurements in both spatial and temporal contexts, the threshold for characterizing the spatial variation of hydraulic properties can be obtained through several statistical tests, using two distinct data subsets delineated from an analysis of the terrain attributes and hydraulic properties. Results reveal that threshold behavior appears to be restricted for hydraulic properties associated with the generation of the flow through macropores.

Temperature trends in Hong Kong from a seasonal perspective

We examined the seasonal trends of mean and extreme temperatures in Hong Kong using data from 1885−2010. The analysis revealed that the daily maximum temperature (TMax), daily mean temperature (TMean), and daily minimum temperature (TMin) of Hong Kong had a sig- nificant long-term increasing trend in all 4 seasons and that the warming trend was more promi- nent in winter and spring. The relatively higher rate of increase in temperatures in winter and spring could be attributed to local urbanization effects and the weakening of the East Asian winter monsoon in the last few decades. For extreme indices, we observed a significant increase in the hot indices (TN90p and TX90p) and a significant decrease in the cold indices (TX10p and TN10p) in all seasons. The seasonal variations in the heating and cooling degree-days (HDD and CDD) also indicated that CDD in spring, summer, and autumn had a significant increasing trend, while HDD in spring, autumn and winter had a decreasing trend. Analysis of the hot and cool periods in Hong Kong showed a significant decreasing (increasing) trend in the number of cool (hot) days. Also, the cool (hot) period has become shorter (longer) over the last century.

Seasonal environments, episodic density compensation and dynamics of structure of chiropteran frugivore guilds in Paraguayan Atlantic forest

Seasonal environmental variation experienced in the subtropics may contribute substantially to dynamics of community structure. This is particularly true for Neotropical bats because the geographic terminus of most families occurs there. Paraguayan Atlantic forest provides an ideal opportunity to evaluate effects of seasonality on structure of communities; it exhibits notable spatial and seasonal environmental variation and lies near the edge of the geographic distribution of most tropical bat species occurring there. We examined seasonality of bat populations and communities as well as correspondence to seasonal environmental conditions in eastern Paraguay. Most species exhibited lower abundances in the cool than in the warm season. Nonetheless, magnitude of differences was species-specific. Accordingly, highly significant differences between warm and cool seasons existed regarding species composition, evenness and diversity. Moreover, consistent with competition theory, magnitude of positive correlation between morphological distance and abundance and hence degree of structure was greater in the cool than warm season. Across the New World, seasonality assumes various forms (i.e. cold winters, dry and wet seasons) suggesting that better understanding of mechanistic bases of bat community structure in general may come from seasonal perspectives.

Instrumental validation ofGlobigerinoides ruberMg/Ca as a proxy for NE Pacific summer SST

[1] Accurate reconstruction of sea surface temperature (SST) is a high research priority, given that it is such a crucial variable in the Earth's climate system. The Mg/Ca composition of Globigerinoides ruber (white) has been calibrated and applied for a number of tropical and extratropical paleo-SST reconstructions, though validation studies of the proxy against instrumental observations are relatively scarce. Here we present a validation of G. ruber Mg/Ca-derived SSTs against instrumental summer values, firstly from the modern seasonal water column perspective, and secondly from a 20th century observational time series. The study occurs in the San Lazaro Basin (SLB), one of the marginal basins in the NE Pacific known for very high sedimentation rates, excellent preservation, laminated sequences, and the ability to record upwelling processes on high-resolution timescales, from interannual climatic variability (El Nino / Southern Oscillation (ENSO)) to interdecadal (e.g., the Pacific Decadal Oscillation (PDO)). Results suggest that the proxy best reflects the summer season. The proxy-instrument time-series comparison for summer SSTs displays remarkable agreement, driven largely by ENSO cycles for the past century, with some events missing due to scarcity of foraminiferal specimens and/or lack of sufficient temporal resolution. This study validates the G. ruber Mg/Ca proxy for summer SSTs in this region, and suggests its high fidelity to reconstruct summer SST from SLB over longer timescales to record multi-decadal and multi-centennial variabilities.