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Better spread-error relationship in a multimodel ensemble prediction system
No full textThis study describes an attempt to overcome the underdispersive nature of single-model ensembles (SMEs). As an Indo–U.S. collaboration designed to improve the prediction capabilities of models over the Indian monsoon region, the Climate Forecast System (CFS) model framework, developed at the National Centers for Environmental Prediction (NCEP-CFSv2), is selected. This article describes a multimodel ensemble prediction system, using a suite of different variants of the CFSv2 model to increase the spread without relying on very different codes or potentially inferior models. The SMEs are generated not only by perturbing the initial condition, but also by using different resolutions, parameters, and coupling configurations of the same model (CFS and its atmosphere component, the Global Forecast System). Each of these configurations was created to address the role of different physical mechanisms known to influence error growth on the 10–20-day time scale. Last, the multimodel consensus forecast is developed, which includes ensemble-based uncertainty estimates. Statistical skill of this CFS-based Grand Ensemble Prediction System (CGEPS) is better than the best participating SME configuration, because increased ensemble spread reduces overconfidence errors
On the possible use of satellite fixed positions for Argo float profiles in case of wrong fixes by GPS
No full textIndian National Centre for Ocean Information Services (INCOIS) had deployed Iridium based Provor Bio-Argo floats obtained from NKE Instrumentation, France. These floats are fitted with GPS for obtaining accurate position of the Argo profiles. However there are cases where in the GPS fitted with the Argo floats tend to give wrong coordinates of profile position owing to unknown reasons. In the present work we discussed the possibilities of using the Iridium satellite fixed position as a substitute of GPSfixed locations in place of wrong GPS positions. For this, statistical analysis was done by comparing the GPS and Iridium satellite fixed profiles positions of 258 profiles from 5 floats which had no problem with the GPS. For each comparison, the GPS fixed position with least Circular Error Probability (CEP) radius was chosen. It was observed that CEP radii are relatively consistent with distances between GPS and Iridiumsatellite fixes with a correlation of 0.85. The study suggests that on an average the Iridium satellite based positions tend to differ from the GPS fixed positions by 0.09°. On the whole CEP radii are found to be consistent with the difference between Iridium satellites and GPS fixed positions. Based on this we suggest a quality flag of 2 (implying probably well) for positions with CEP radius less than or equal to 4 Km and flag 4 (implying bad) for all other positions
Bifurcation and control of an eco-epidemiological system with environmental fluctuations: a stochastic approach
No full textThis paper describes the dynamics of an infectious disease transmission modified Leslie–Gower type eco-epidemiological system in both deterministic and stochastic fluctuating environments with harvesting. The dynamics of the deterministic system is extensively investigated around coexistence equilibria. Sufficient conditions are derived for local and global stability of the system. The existence of Hopf bifurcation phenomenon is examined around interior equilibria of the system. Subsequently, we use normal form method and center manifold theorem to examine the nature of the Hopf bifurcation. The obtained results are useful to extract the criteria for disease extinction and control perspective. Later, a white noise term is incorporated to the system to describe the dynamics of the system in stochastic fluctuating environment. Sufficient conditions are derived for the mean square stability (MSS) of the system which can be used to evaluate necessary conditions for the asymptotic MSS and a threshold condition between asymptotic MSS and unstable system. Finally, some numerical simulations are carried out, and graphical illustrations are given in support of the analytical results obtained in both deterministic and stochastic system
Analysing predictability in Indian monsoon rainfall: A data analytic approach
No full textThis paper examines monthly and annual data to analyse predictability in the Indian monsoon rainfall. The periodic structure in the time series data is extracted using wavelets and the residual random part is separately modeled using artificial neural networks (ANN). Although wavelet and neural network based hybrid techniques have been widely applied in the recent years, the present approach has not been investigated so far. Our results show that the estimated periodic and random components comprise 30 and 15 , respectively, variance of the total rainfall in case of annual data, whereas the model explains 93 of variance in case of monthly data. It is shown that the prediction is more accurate when periodic and random parts are treated separately
Brief Review: The study of Ozone and its Precursors Gases
No full textOzone is a major element on earth’s atmosphere. It is made up of tri-atomic molecule of oxygen, that the reason is it
formulates “O3”. The ground level ozone act as a primary pollutant in atmosphere, made after the reaction of primary
pollutants (NOX and VOCs) in the presence of sunlight. In troposphere, to increase the level of ozone many precursor gases are present which are responsible for the production of ground level ozone. These precursor gases are carbon monoxide (CO), carbon dioxide (CO2), oxides of nitrogen (NOx), methane (CH4), hydro carbons (HCs) and volatile organic compounds (VOCs). The major anthropogenic sources of ozone in the troposphere are industrial emissions, vehicular exhaust and chemical solvents. The concentration of ozone in the atmosphere is monitored and maintain by different ozone air quality standards and national ambient air quality index (NAAQI), by observing them in monitoring system
Evaluation of changes in benthic standing stock and polychaete community structure along the south eastern Arabian Sea shelf during the monsoon trawl-ban
No full textThe south eastern Arabian Sea is characterized by moderate coastal upwelling, high biological production and subsurface oxygen depletion during the southwest monsoon(June–September). Concurrently,a seasonal closure to trawling activities(15th June–31st July)is implemented here,as a sustainable ecosystem management practise. The effects of monsoon driven environmental changes and consequences
of trawling cessation on macrofauna were assessed, based on surveys at 12 sites(30–200m)preceding and during different phases of the southwest monsoon. Macrofaunal density and biomass increased considerably towards the mid and late monsoon along the inner shelf(30–50 m)where trawling is in-
tense, while no temporal changes were observed along the outer shelf(100–200m).Density increased four-folds at the 30m contour and three-folds at 50m, while biomass nearly doubled at both depths,reflecting a marked increase in density of polychaetes(61–87% of macrofauna). The disproportionate increase in faunal density and biomass along the inner shelf(30–50 m) was due to abundance of juvenile polychaetes and dominance of small-sized opportunists towards late monsoon(August–September).A
concurrent hike in nominal species count of polychaetes was also observed in the study area. The increase in polychaete standing stock and high density of planktonic larvaed uring onset and peak monsoon, coupled with occurrence of juveniles as well as gamete-bearing adults in sediments,indicates that
the southwest monsoon is a peak breeding season for the dominant polychaetes in the region. The trawl-ban during this period facilitates the recoupment of benthos by maximising spawning success and larval settlement, thereby enhancing overall ecosystem integrity
Radiocarbon-based source apportionment of elemental carbon aerosols at two South Asian receptor observatories over a full annual cycle
Get PDFBlack carbon (BC) aerosols impact climate and air quality. Since BC from fossil versus biomass combustion have different optical properties and different abilities to penetrate the lungs, it is important to better understand their relative contributions in strongly affected regions such as South Asia. This study reports the first year-round 14C-based source apportionment of elemental carbon (EC), the mass-based correspondent to BC, using as regional receptor sites the international Maldives Climate Observatory in Hanimaadhoo (MCOH) and the mountaintop observatory of the Indian Institute of Tropical Meteorology in Sinhagad, India (SINH). For the highly-polluted winter season (December–March), the fractional contribution to EC from biomass burning (fbio) was 53 ± 5% (n = 6) at MCOH and 56 ± 3% at SINH (n = 5). The fbio for the non-winter remainder was 53 ± 11% (n = 6) at MCOH and 48 ± 8% (n = 7) at SINH. This observation-based constraint on near-equal contributions from biomass burning and fossil fuel combustion at both sites compare with predictions from eight technology-based emission inventory (EI) models for India of (fbio)EI spanning 55–88%, suggesting that most current EI for Indian BC systematically under predict the relative contribution of fossil fuel combustion. A continued iterative testing of bottom-up EI with top-down observational source constraints has the potential to lead to reduced uncertainties regarding EC sources and emissions to the benefit of both models of climate and air quality as well as guide efficient policies to mitigate emissions
Intra-urban variability of particulate matter (PM2.5 and PM10) and its relationship with optical properties of aerosols over Delhi, India
No full textHighly time-resolved measurements of particulate matter (PM: PM2.5 and PM10) were made at three different sites across Delhi (CCRI: a highly traffic site, IMD: a less traffic site and IITM: an urban background site) from 1st December, 2011 to 30th June, 2013. Also, coarse mode (PM10–2.5) mass was estimated as the difference between PM10 and PM2.5. In addition, columnar aerosol optical properties such as aerosol optical depth (AOD) and Angstrom exponent (AE) were studied concurrently over IMD. The mean mass concentrations of PM2.5, PM10–2.5 and PM10 were 118.3 ± 81.7, 113.6 ± 70.4 and 232.1 ± 131.1 μg m− 3, respectively. Among the three sites, relatively higher mass concentrations of PM2.5 (~ 35% and 3%) were observed at CRRI compared to IMD and IITM.PM10 and PM10–2.5 were higher at these sites by ~ 31% and 19%; and 27% and 40%, respectively, compared to CRRI. Coefficients of divergence (COD) and correlation coefficients (r) were calculated between site pairs to assess the spatial and temporal heterogeneity of PM and moderate spatial divergence was found over the three sites. Traffic emission particles (PM2.5) exhibited high spatial heterogeneity as well. The mass concentrations of PM2.5 and PM10 were found to be higher during the night compared to the day. The mean PM2.5/PM10 ratio was ~ 51%, indicating generally equal amounts of coarse and fine mode PM in the Delhi urban atmosphere. AOD and PM2.5 were positively correlated and a negative correlation was observed between AE and PM10–2.5. PM2.5 particles were significantly correlated with AOD during post-monsoon and winter. Because of the lower vehicular emissions on weekends compared to weekdays, PM at CRRI, IMD, and IITM were separated by day of week and large heterogeneities were found. During weekdays, the mass concentrations of PM10 were ~ 4, 2, and 12% higher than on weekends. However, for PM2.5, weekend values were 5, 7, and 9% higher for CRRI, IMD and IITM, respectively
Association of the pre-monsoon thermal field over north India and the western Tibetan Plateau with summer monsoon rainfall over India
Get PDFIn this paper, interannual variability of tropospheric air temperatures over the Asian summer monsoon region during the pre-monsoon months is examined in relation to Indian summer monsoon rainfall (ISMR; June to September total rainfall). For this purpose, monthly grid-point temperatures in the entire troposphere over the Asian summer monsoon region and ISMR data for the period 1949–2012 have been used. Spatial correlation patterns are investigated between the temperature field in the lower tropospheric levels during May over the Asian summer monsoon region and ISMR. The results indicate a strong and significant northwest–southeast dipole structure in the spatial correlations over the Indian region, with highly significant positive (negative) correlations over the regions of north India and the western Tibetan Plateau region – region R1 (north Bay of Bengal: region R2). The observed dipole is seen significantly up to a level of 850 hPa and eventually disappears at 700 hPa. Thermal indices evaluated at 850 hPa level, based on average air temperatures over the north India and western Tibetan Plateau region (TI1) and the north Bay of Bengal region (TI2) during May, show a strong, significant relationship with the ISMR. The results are found to be consistent and robust, especially in the case of TI1 during the period of analysis. A physical mechanism for the relationship between these indices and ISMR is proposed. Finally the composite annual cycle of tropospheric air temperature over R1 during flood/drought years of ISMR is examined. The study brings out the importance of the TI1 in the prediction of flood/drought conditions over the Indian subcontinent
Indian summer monsoon rainfall and its relation with SST in the equatorial Atlantic and Pacific Oceans
No full textA better understanding of the factors responsible for the variability in Indian summer monsoon rainfall (ISMR) is important in the present day climate because it is vulnerable to climate change. Here, we report the relationship between the Atlantic and Pacific sea surface temperature (SST) anomalies with ISMR. We developed a new ISMR index based on the high correlation of the SST anomaly over the oceanic regions during March–April, prior to the southwest monsoon season. The study was performed by utilizing rainfall data from the India Meteorological Department and SST anomaly derived from monthly extended reconstruction sea surface temperature data. We found that the relationship of the SST anomaly in the southwest Pacific region during the March–April period with the following ISMR is persistent in the 31-year sliding window correlation analysis. SST anomaly in the Equatorial Atlantic during the March–April period is related almost in a similar manner to the following ISMR. However, persistence of the significance level is fluctuating. This indicates that the ISMR and the SST anomalies have varying relationships. To find out the fluctuation in the relationship between ISMR and the SSTs, we subjected the parameters to harmonic analysis. We noticed that the SST anomalies have similar kind of variability in the multidecadal (32 year), decadal (10.5) and interdecadal (5.6) periodicities in both Atlantic and southwest Pacific regions. The harmonics of SST and ISMR in the multidecadal time scale is out of phase and that for decadal and interdecadal time scales are in phase