October January Research Articles

Surface Wave Climatology and Its Variability in the North Indian Ocean Based on ERA-Interim Reanalysis

AbstractThe climate over the north Indian Ocean (NIO) is one of the most dynamic in the world because of seasonally reversing monsoon winds. In this study, the climate of the NIO and the variability of its surface waves using the European Centre for Medium-Range Weather Forecasts (ECMWF) global atmospheric reanalysis product (ERA-Interim) for the period 1979–2012 are analyzed. Annual average significant wave height (SWH) of the NIO ranges from 1.5 to 2.5 m and the seasonal average is highest (3–3.5 m) during the monsoon period [June–September (JJAS)]. Swells propagating from the Southern Hemisphere are present in the NIO during the premonsoon [February–May (FMAM)] and postmonsoon [October–January (ONDJ)] periods. The waves are separated into wind seas and swells based on the wave energy statistical method. The results show that the NIO is swell dominated and that wind sea heights are lower compared to the swell heights. Higher wind sea and swell heights are observed during the monsoon in the western NIO because of strong cross-equatorial winds of the Somali (Findlater) jet. In the postmonsoon period, the eastern NIO shows a higher swell height than the western NIO shows. SWH shows an annual increasing trend in the western NIO. On a seasonal scale, the trends are increasing significantly in the monsoon compared to the postmonsoon period in a major part of the NIO, whereas the premonsoon period shows a decline in SWH. In the NIO, the monsoon is the dominant mode of variability and it covers 92% of the total variability. Wave climate is also influenced by the annual and interannual variability in monsoon wind and rainfall.

A multi-model evaluation of aerosols over South Asia: common problems and possible causes

Abstract. Atmospheric pollution over South Asia attracts special attention due to its effects on regional climate, water cycle and human health. These effects are potentially growing owing to rising trends of anthropogenic aerosol emissions. In this study, the spatio-temporal aerosol distributions over South Asia from seven global aerosol models are evaluated against aerosol retrievals from NASA satellite sensors and ground-based measurements for the period of 2000–2007. Overall, substantial underestimations of aerosol loading over South Asia are found systematically in most model simulations. Averaged over the entire South Asia, the annual mean aerosol optical depth (AOD) is underestimated by a range 15 to 44% across models compared to MISR (Multi-angle Imaging SpectroRadiometer), which is the lowest bound among various satellite AOD retrievals (from MISR, SeaWiFS (Sea-Viewing Wide Field-of-View Sensor), MODIS (Moderate Resolution Imaging Spectroradiometer) Aqua and Terra). In particular during the post-monsoon and wintertime periods (i.e., October–January), when agricultural waste burning and anthropogenic emissions dominate, models fail to capture AOD and aerosol absorption optical depth (AAOD) over the Indo–Gangetic Plain (IGP) compared to ground-based Aerosol Robotic Network (AERONET) sunphotometer measurements. The underestimations of aerosol loading in models generally occur in the lower troposphere (below 2 km) based on the comparisons of aerosol extinction profiles calculated by the models with those from Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) data. Furthermore, surface concentrations of all aerosol components (sulfate, nitrate, organic aerosol (OA) and black carbon (BC)) from the models are found much lower than in situ measurements in winter. Several possible causes for these common problems of underestimating aerosols in models during the post-monsoon and wintertime periods are identified: the aerosol hygroscopic growth and formation of secondary inorganic aerosol are suppressed in the models because relative humidity (RH) is biased far too low in the boundary layer and thus foggy conditions are poorly represented in current models, the nitrate aerosol is either missing or inadequately accounted for, and emissions from agricultural waste burning and biofuel usage are too low in the emission inventories. These common problems and possible causes found in multiple models point out directions for future model improvements in this important region.

Temporal variability of the current in the northeastern South China Sea revealed by 2.5-year-long moored observations

The current in the northeastern South China Sea (NSCS) has been extensively studied by both observations and numerical models, but its vertical structure and temporal variability are still not well understood because of the lack of long-term and full-depth direct observations. From August 2010 to March 2013, the current velocity in the NSCS was directly observed by Acoustic Doppler Current Profilers from a subsurface mooring at 117°52.07′E, 21°06.68′N. The observed current velocity was coherent in the vertical direction and nearly showed the same sign in the nearly full water column (960 m). The observed current presented strong intraseasonal variabilities (ISVs) within periods between 30 and 90 days. Analysis of the altimeter observation suggested that the ISVs were closely related to the propagating mesoscale eddies. Corresponding to the seasonally varying circulation in the NSCS, the ISV-removed current roughly showed a semiannual cycle. The seasonal U (V) averaged over 80–200 m depths reached the peak in March and October (January and July) and the trough in July and February (April and August), respectively, with a peak-to-trough amplitude of 0.14 m/s (0.19 m/s). Dynamical modes analysis suggested that the observed current velocity showed dominated energy in the barotropic mode during most of the observation period but enhanced energy in the first baroclinic mode during eddy events because of the enhanced vertical shear of velocity.

Hormone Levels and Ultrasound Evaluation ofCaiman latirostris(Crocodylia, Alligatoridae) Ovulation

Fil: Costa Goncalves Portelinha, Thiago. Provincia de Entre Rios. Centro de Investigaciones Cientificas y Transferencia de Tecnologia a la Produccion. Universidad Autonoma de Entre Rios. Centro de Investigaciones Cientificas y Transferencia de Tecnologia a la Produccion. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Santa Fe. Centro de Investigaciones Cientificas y Transferencia de Tecnologia a la Produccion; Argentina. Universidade Federal do Tocantins; Brasil. Universidad Nacional del Litoral; Argentina

Wave energy resource assessment for the Indian shelf seas

As a renewable energy, the assessment of wave power potential around a country is crucial. Knowledge of the temporal and spatial variations of wave energy is required for locating a wave power plant. This study investigates the variations in wave power at 19 locations covering the Indian shelf seas using the ERA-Interim dataset produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). The ERA-Interim data is compared with the measured wave parameters in the Arabian Sea and the Bay of Bengal. Along the western shelf seas of India, the seasonal oscillations lead to variation of the wave power from the lowest seasonal mean value (2.6 kW/m) in the post-monsoon period (October–January) to the highest value (25.9 kW/m) in the south-west monsoon (June–September) period. Significant (10–20%) inter-annual variations are detected at few locations. The mean annual wave power along the eastern Indian shelf seas (2.6–9.9 kW/m) is lower than the mean annual wave power along the western part (7.9–11.3 kW/m). The total annual mean wave power available along the western shelf seas of India is around 19.5 GW. Along the eastern shelf seas, it is around 8.7 GW. In the Indian Shelf seas, the annual mean wave power is highest (11.3 kW/m) at the southern location (location 11), and the seasonal variation in wave power is also less. Hence, location 11 is a better location for a wave power plant in the Indian shelf seas.

P38 participates in spermatogenesis and acrosome reaction prior to fertilization in Chinese mitten crab Eriocheir sinensis

P38 mitogen-activated protein kinases (MAPKs) comprise a family of serine/threonine protein kinases that play important roles in cellular responses to inflammatory cytokines and environmental stresses. These kinases are involved in controlling cell division, differentiation and death in mammalian testes and therefore are critical to spermatogenesis. To explore their functions in male reproduction of Chinese mitten crabs, Eriocheir sinensis p38 (Es-p38) protein expression was determined in different tissues including testes at different developmental stages by Western blot. Es-p38 was expressed in various tissues, with higher levels in the heart, stomach, gills and testes. Total Es-p38 protein levels increased gradually during spermatogenesis, but phosphorylated Es-p38 was much higher in the spermatid (August–October) than the spermatocyte (July–August) and sperm (October–January) stages. Trypan blue staining and hematoxylin/eosin staining were both used to detect sperm motility and changes in sperm morphology during the acrosome reaction (AR) induced by pre-incubation with A23187 in vitro, activated Es-p38 proteins detected by fluorescent microscopy were translocated gradually to nuclear and apical cap regions, accumulating at the anterior of the acrosomal tubule. The results suggest the involvement of p38 MAPK in spermatogenesis and the AR in E. sinensis.

Dendroclimatic reconstruction of autumn–winter mean minimum temperature in the eastern Tibetan Plateau since 1600 AD

We developed three tree-ring width chronologies of Dragon Spruce (Picea likiangensis var. balfouriana) from Qamdo region in the eastern Tibetan Plateau. It was found that the autumn–winter mean minimum temperature was the principal factor that limited the radial growth of Dragon Spruce. In particular, the tree-ring width chronology of the Changdu site was related significantly and positively with the autumn–winter mean minimum temperature. Using standard dendrochronological (STD) method, we obtained a 400-year reconstruction of October–January minimum temperature at the Qamdo meteorological station. The reconstruction explains 43.1% of the variance in the instrumental temperature records during the 1954–2006 calibration periods. It indicates that quasi-periodic changes exist on scales of 5, 11, and 102–103a. The temperature fluctuates around the mean and rises slowly from 1594 to the 1700s, following which the autumn–winter mean minimum temperature exhibited obvious stage changes with warmer periods (1769–1800, 1819–1849, 1873–1900, 1926–1954, 1987–2006) and colder periods (1716–1768, 1801–1818, 1850–1872, 1901–1925, 1955–1986). The temperature in the eastern Tibetan Plateau and the mean temperature in the Northern Hemisphere exhibited good consistency in the 20th century. From 1900 to the 1930s, the temperature rose slowly and then declined sharply in the 1940s. In the 1950s, the temperature rose, before falling again in the early 1960s, prior to a gradual increase following the late 1960s. The temperature in Qamdo represents the temperature of the southeastern Tibetan Plateau, and significant positive correlations were found with other temperature reconstructions on the southeastern Tibetan Plateau and the southern slopes of the Himalaya (including the Indian peninsula). The India-Burma Trough may have a certain effect on climate change in the eastern Tibetan Plateau. The reconstruction sheds new light on temperature variability and change in a region where the climate history for the past several centuries is poorly understood.

Reproductive seasonality in the Indian pygmy field mouse, Mus terricolor

The Indian pygmy field mouse, Mus terricolor, is a tiny, yet economically and ecologically important crop pest found throughout South-East Asia. There are no systematic reports exploring its reproductive physiology. We report the presence of distinct periods of annual reproductive activity and quiescence in M. terricolor. Body weight in males and females, relative weights of testis, epididymis and seminal vesicle in males, ovarian and uterine weight in females, gonadal histomorphic changes, testicular and ovarian cholesterol, sialic acid in epididymis, fructose in seminal vesicle, uterine protein content, melatonin in males and females, testosterone in males, estradiol, and progesterone in females were studied over a period of three years in both wild-caught and lab-acclimated mice. The number of Graafian follicles and corpora lutea, and plasma estradiol and progesterone, along with relative weights of ovary and uterus in females exhibited a peak in the months of October–January, compared to June. Based on histomorphic and hormonal status, the major reproductively active season is the winter (short-day breeding). There is a brief period of sub-maximal reproductive activity in April. M. terricolor is reproductively inactive in the summer, monsoons, and autumn. The results establish M. terricolor as a seasonal breeder in the field, with interesting implications for pest management.

Interannual variability of the Arabian Sea Warm Pool: observations and governing mechanisms

The near-surface layers in the Arabian Sea progressively warm up from February to early May resulting in the formation of pool of warm waters popularly known as the Arabian Sea Warm Pool (ASWP). The availability of high quality TMI sea surface temperature (SST) data for the years 1998–2010 is exploited to describe the evolution of the ASWP on seasonal and interannual time scales and to explain the associated mechanisms. The multi-year (1998–2010) averaged TMI SSTs during April–May show peak values of the ASWP in excess of 30 °C with its core >30.5 °C extending offshore as a well-marked southwestward tongue stretching from the southwest coast of India. The ASWP shows both seasonal and interannual variability in the evolution of spatio-temporal characteristics such as amplitude, phase and spatial extent. Among these 13 years, the ASWP was most (least) pronounced during 1998, 2003 and 2010 (1999, 2000, 2001 and 2008). The mechanisms that govern the observed interannual variability of the ASWP are examined addressing the most relevant issues such as—(1) dynamic pre-conditioning: background pycnocline topography influenced by the westward propagating Rossby waves during October–May, (2) thermal pre-conditioning: background SST/heat content signal during October–January influenced by the strength of the preceding year’s summer monsoon and the post-monsoon cyclones during October–December, (3) haline pre-conditioning: near-surface vertical salinity stratification during November–February influenced by the advection of low saline waters from the Bay of Bengal, (4) influence of surface net heat flux forcing during February–May, and (5) influence of El Nino/La Nina.

Reproductive biology of Willisia arekaliana (Podostemaceae), a freshwater endemic species of India

We investigated the floral biology, mechanism of pollination and breeding system of Willisia arekaliana (Podostemaceae), an endemic, fresh water aquatic angiosperm, restricted to the state of Kerala, India. The reproductive phase exists between late October and early January. Flowering starts under submerged condition and the flowers become conspicuous only when the water level recedes. Each flower is represented by a pistil with bi-lobed stigma and a pair of bithecous anthers and enclosed by the spathella. Pollination occurs at the air–water interface soon after the flower is partly exposed to air by a small apical opening in the spathella. Concurrence of stigma receptivity with anther dehiscence and apposition of the two organs facilitate autopollination. There is profuse pollen (∼3900) and ovule (∼170) production, and low pollen:ovule ratio (24) complies with the occurrence of obligate autogamy. As there is very short span of time available for pollination and also that the dehisced anthers may not retain pollen for sufficient time in fast flowing streams, autopollination appears to ensure sexual reproduction and high natural fecundity (seed set) in the species.

Annual ovarian cycle and other reproductive traits of female Red River Pupfish (Cyprinodon rubrofluviatilis) in the Red River drainage of Texas

We examine variation in ovarian traits over a 24-month period in Cyprinodon rubrofluviatilis, an inhabitant of highly variable stream environments in the southern Great Plains of western Texas and Oklahoma. The smallest females bearing clutches are ca. 20 mm in standard length. Ovarian traits indicate that maximum reproduction occurred from March into July, but some degree of reproduction was potentially possible throughout the year. Most ovaries had atretic oocytes as early as September when the gonadosomatic index and the percentage of females with clutches were declining, but a small proportion had mature eggs in all fall and winter months (0–2%, average 0.8%, October–January, across all years) except, possibly due to sampling error, in October. Detailed analysis of females from April and July indicate greater reproduction in 2002 than in 2003 and greater in spring than in mid-summer. There was marginal evidence from estimates of dry weight of oocytes that females invest more energy in individual offspring in spring than in mid-summer.

Influence of marine, terrestrial and anthropogenic sources on ionic and metallic composition of rainwater at a suburban site (northwest coast of Spain)

In the present research, the rainwater chemistry of soluble (SF) and non-soluble (NSF) fractions is studied over a one a half year period (from March 2011 to August 2012) at a suburban site (Oleiros, A Coruña, Spain). The monthly rainfall in this region during the studied period ranged from 10 to 137 mm, while the NSF ranged from 0.9 to 54 mg L−1. More rainfall occurs within October–January. Eighteen samples, which provide information pertaining to the monthly variation in chemistry, were analyzed. Trace metals (Al, As, Ba, Co, Cu, Cr, Fe, Mn, Ni, Pb, Sr, V, Zn) were enclosed in the study of both fractions of the rainwater. Major inorganic ions (Cl−, NO3−, SO42−, Na+, K+, Ca2+, Mg2+ and NH4+) were also enclosed in the study of the SF of the rainwater. After partition coefficients analysis, univariate and principal components analysis (PCA) and air mass back trajectories analysis, three sources were found for the ionic and metal composition of the SF of rainwater; terrestrial (Ca2+, non sea salt SO42−, Al and Fe), marine (Mg2+, Na+, Cl−) and anthropogenic (K+, NH4+, NO3−, Fe, Mn, Pb, Sr, V and Zn). Results also suggest ubiquitous sources for Ba, Co, Cu, Cr and Ni. One source (terrestrial) was found for NSF of rainwater.

Uncovering the Footprints of Erosion by On-Farm Maize Cultivation in a Hilly Tropical Landscape

A hilly region in Sri Lanka was considered to be degraded by erosion driven by intensive tobacco production, but what are reliable indicators of erosion? In addition to determining soil chemical and physical traits, maize was cropped with Nitrogen, Phosphorus and Potassium (NPK, PK) recommended mineral fertilization and without fertilizer (ZERO) in two major seasons(October–January in 2007/2008 and 2008/2009—Seasons 1 and 2 respectively) on 92 farms at inclinations ranging from 0% to 65%. In a subset of steep farms (n = 21) an A horizon of 6 cm rather than of 26 cm was strong proof of erosion above 30% inclination. Below the A level, the thickness of the horizon was unaffected by inclination. Soil organic matter contents (SOM) were generally low, more so at higher inclinations, probably due to greater erosion than at lower inclination. Maize yields decreased gradually with increasing inclination; at ZERO, effects of climate and soil moisture on yield were easier determined and were probably due to long-term erosion. However, despite an initial set of 119 farms, an exact metric classification of erosion was impossible. NPK strongly boosted yield. This was a positive sign that the deficits in chemical soil fertility were overriding physical soil weaknesses. The study illustrated that chemical soil fertility in these soils is easily amenable to modifications by mineral and organic manures.

Spatial and temporal interactions between livestock and wildlife in South Central Spain assessed by camera traps

The diversification of livestock farms into hunting estates in South Central Spain (SCS) may impede the success of Mycobacterium bovis eradication programmes by facilitating transmission between wildlife and livestock. In this observational study we aimed to provide information of relevance about the nature and frequency of interactions (observed visits to study points) between livestock (cattle and domestic pigs) and wildlife (wild boar and red deer). The study was conducted in an extensive cattle farm in SCS where the land is also used for game hunting. During a period of one year, camera traps (n=16) were placed at a priori risk points for interspecies interactions: water (natural and artificial troughs), food placed on the ground for baiting wildlife, and pasture. To define indirect interspecies interactions, a critical time window for M. bovis to survive in the environment was selected based on the literature. Results suggest that wildlife frequented food and pasture points more often than water points, and that the number of visits increased through the dry season, peaking during the acorn season (October–January) and the deer breeding season (June–July). Direct interactions were rare (n=10), as opposed to indirect interactions (n=8992). Wildlife-followed-by-livestock interactions (n=7714) occurred much more often than livestock-followed-by-wildlife (n=1278) and were frequent at water points (66% water points, 17% food, 17% pasture). Results also suggest that water points are a hotspot for indirect interactions and might therefore be a source of infection at the wildlife–livestock interface in the territory covered, particularly for M. bovis, as it is around water where the bacteria seem to survive the longest. Preventing aggregation and therefore reducing contact rates between domestic and wild animals especially at water points may be valuable for disease control in South Central Spain.

Development of an agroclimatological risk tool for dryland maize production in the Free State Province of South Africa

Decision support tools are helpful aids for sustainable natural resource management and deployment of these tools depends on their usability, appropriateness and simplicity. A decision support tool named “Free State Maize Agroclimatological Risk Tool (FS-Macrt)” was developed to provide agroclimatological risk information important to the production of rainfed maize in the Free State Province of South Africa. The tool can be used by farmers, extension officers, policy-makers and agricultural risk advisors and has two main parts: (1) climatological risk and (2) forecasting. The climatological risk component enables the user to obtain drought stress risk for 100-day, 120-day and 140-day maize cultivars for planting windows starting in October–January. The best planting dates based on the risk associated with the climatology onset and cessation of both rains and frost can be determined. Using climate forecasts obtained from the national forecasting centres, drought index can be predicted for different planting dates giving the farmer valuable information when planning for the coming season. The tool also has the functionality of predicting onset of rains using weather and climate forecasts.

Plant-Level Responses to the Economic Crisis in Europe

How are social policy actors in major sectors of the European economy responding to the current economic and financial crisis? This working paper summarises the plant-level responses of social policy actors to the symptoms of the current recession between October and mid January 2009. It examines how, during this period, organised labour and capital responded to the crisis in several key sectors and countries and what collective bargaining and labour market tools were available to deal with the effects of the crisis and safeguard employment. The paper provides an overview of the effects of the crisis on employees and the micro-level responses of the social partners. A summary of the various tools to which crisis-hit companies have resorted such as collective agreements at the sectoral, industry and company/plant level and legal regulations is provided. A particular focus is made on plant-level agreements on working time flexibilisation that are aimed at avoiding redundancies and labour market instruments to regulate short-time working. The working paper concludes with an overview of the scope and effects of the crisis in terms of employment and working time reduction and the highly diversive plant-level responses to the downturn.

Trends in Antarctic Peninsula surface melting conditions from observations and regional climate modeling

Multidecadal meteorological station records and microwave backscatter time‐series from the SeaWinds scatterometer onboard QuikSCAT (QSCAT) were used to calculate temporal and spatial trends in surface melting conditions on the Antarctic Peninsula (AP). Four of six long‐term station records showed strongly positive and statistically significant trends in duration of melting conditions, including a 95% increase in the average annual positive degree day sum (PDD) at Faraday/Vernadsky, since 1948. A validated, threshold‐based melt detection method was employed to derive detailed melt season onset, extent, and duration climatologies on the AP from enhanced resolution QSCAT data during 1999–2009. Austral summer melt on the AP was linked to regional‐ and synoptic‐scale atmospheric variability by respectively correlating melt season onset and extent with November near‐surface air temperatures and the October–January averaged index of the Southern Hemisphere Annular Mode (SAM). The spatial pattern, magnitude, and interannual variability of AP melt from observations was closely reproduced by simulations of the regional model RACMO2. Local discrepancies between observations and model simulations were likely a result of the QSCAT response to, and RACMO2 treatment of, ponded surface water, and the relatively crude representation of coastal climate in the 27 km RACMO2 grid.

Surface energy balance measurements over a banana plantation in South China

The land surface energy exchange depends highly on the surface properties. Little is known of the energy balance over a typical banana plantation of humid tropics. In this study, we examine the characteristics of surface energy exchange over a typical banana field in South China during the period of May 2010 to April 2011 by using the eddy covariance and micrometeorological tower. The results showed that the diurnal and seasonal variations in surface latent heat flux were larger compared with those over the nearby grassland. The dominant energy partitioning varies with season. The latent heat flux was the main consumer of net radiation in summer, whereas the sensible heat flux was the main consumer in winter. The increasing cloud coverage and rain appear to control the surface energy balance with the development of the monsoon. Due to increased afternoon convective cloud systems in the monsoon active period, downward shortwave radiation was dramatically diminished around 14:00 pm. The annual mean Bowen ratio was 0.69, which fell within the range of other vegetated surfaces. The observed surface energy components were not closed, and the ratio of turbulent fluxes to the available energy was about 77 % in October–January and about 85 % in the other months after considering soil heat and air heat storage.

Life history traits of the invasive estuarine shrimp <i>Palaemon macrodactylus</i> (Caridea: Palaemonidae) in a marine environment (Mar del Plata, Argentina)

The invasive oriental shrimp Palaemon macrodactylus has been extensively recorded around the world, mainly in estuarine zones. In this study, the life history of this species was studied in Mar del Plata harbour (Argentina), a fully marine area where a stable and dense population has been established. Growth, sex proportion, morphological relationships, size at maturity and reproductive cycle were analysed between March 2007 and March 2009. A total of 9 and 7 modal classes (M1-M9) were detected in the size frequency distributions of females and males, respectively. The modes of both sexes were the same until M4 but from M5 to M7 females were larger than males. The life span was about one year with a clear seasonal growth. Recruitment and reproductive periods were recorded from December to March and October to March, respectively. The total sex ratio was biased to females. Nevertheless, a clear predominance of males was observed in classes smaller than 5.25 mm carapace length (CL). Females reached maturity at a larger size in spring to early summer (October–January) than in late summer (February–March); the estimated sizes for 50% sexual maturity were 6.79 mm and 5.91 mm CL, respectively. The results showed great differences from a presumably native estuarine population (Japan), such as shorter life span, smaller maximum size and smaller size at maturity.

Temporal Trends in Atmospheric PM2.5, PM10, Elemental Carbon, Organic Carbon, Water-Soluble Organic Carbon, and Optical Properties: Impact of Biomass Burning Emissions in The Indo-Gangetic Plain

The first simultaneous measurements and analytical data on atmospheric concentrations of PM(2.5), PM(10), inorganic constituents, carbonaceous species, and their optical properties (aerosol optical depth, AOD; absorption coefficient, b(abs); mass absorption efficiency, σ(abs); and single scattering albedo, SSA) from an urban site (Kanpur) in the Indo-Gangetic Plain are reported here. Significantly high aerosol mass concentration (>100 μg m(-3)) and AOD (> 0.3) are seen as a characteristic feature throughout the sampling period, from October 2008 to April 2009. The temporal variability in the mass fractions of carbonaceous species (EC, OC, and WSOC) is pronounced during October-January when emissions from biomass burning are dominant and OC is a major constituent (∼30%) of PM(2.5) mass. The WSOC/OC ratio varies from 0.21 to 0.65, suggesting significant contribution from secondary organic aerosols (SOAs). The mass fraction of SO(4)(2-) in PM(2.5) (Av: 12.5%) exceeds that of NO(3)(-) and NH(4)(+). Aerosol absorption coefficient (@ 678 nm) decreases from 90 Mm(-1) (in December) to 20 Mm(-1) (in April), and a linear regression analysis of the data for b(abs) and EC (n = 54) provides a measure of the mass absorption efficiency of EC (9.6 m(2) g(-1)). In contrast, scattering coefficient (@ 678 nm) increases from 98 Mm(-1) (in January) to 1056 Mm(-1) (in April) and an average mass scattering efficiency of 3.0 ± 0.9 m(2) g(-1) is obtained for PM(10) samples. The highest b(scat) was associated with the dust storm event (April 17, 2009) over northern Iraq, eastern Syria, and southern Turkey; thus, resulting in high SSA (0.93 ± 0.02) during March-April compared to 0.82 ± 0.04 in October-February. These results have implications to large temporal variability in the atmospheric radiative forcing due to aerosols over northern India.