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Modeling and analysis of a marine plankton system with nutrient recycling and diffusion
No full textThis article describes a nutrient-phytoplankton-zooplankton system with nutrient recycling in the presence of toxicity. We have studied the dynamical behavior of the system with delayed nutrient recycling in the first part of the article. Uniform persistent of the system is examined. In the second part of the article, we have incorporated diffusion of the plankton population to the system and dynamical behavior of the system is analyzed with instantaneous nutrient recycling. The condition of the diffusion driven instability is obtained. The conditions for the occurrence of Hopf and Turing bifurcation critical line in a spatial domain are derived. Variation of the system with small periodicity of diffusive coefficient has been studied. Stability condition of the plankton system subject to the periodic diffusion coefficient of the zooplankton is derived. It is observed that nutrient-phytoplankton-zooplankton interactions are very complex and situation specific. Moreover, we have obtained different exciting results, ranging from stable situation to cyclic oscillatory behavior may occur under different favorable conditions, which may give some insights for predictive management
An early South Asian dust storm during March 2012 and its impacts on Indian Himalayan foothills: A case study
No full textThe impacts of an early South Asian dust storm that originated over the western part of the Middle East and engulfed northwest parts of India during the third week of March 2012 have been studied at four different stations covering India and Pakistan. The impacts of this dust storm on aerosol optical properties were studied in detail at Delhi, Jodhpur, Lahore and Karachi. The impact could also be traced up to central Himalayan foothills at Manora Peak. During dust events, the aerosol optical depth (AOD) at 500. nm reached a peak value of 0.96, 1.02, 2.17 and 0.49 with a corresponding drop in à ngström exponent (AE for 440-870. nm) to 0.01, 0.02, 0.00 and 0.12 at Delhi, Jodhpur, Lahore and Karachi, respectively. The single scattering albedo (SSA) at 675. nm was relatively lower at Delhi (0.87) and Jodhpur (0.86), with absorption à ngström exponent (AAE) less than 1.0, but a large value of SSA was observed at Lahore (0.98) and Karachi (0.93), with AAE value greater than 1.0 during the event. The study of radiative impact of dust aerosols revealed a significant cooling at the surface and warming in the atmosphere (with corresponding large heating rate) at all the stations during dust event. The effect of this dust storm was also seen at Manora Peak in central Himalayas which showed an enhancement of ~. 28 in the AOD at 500. nm. The transport of dust during such events can have severe climatic implications over the affected plains and the Himalayas
High-resolution operational monsoon forecasts: an objective assessment
No full textOptimization of computational efficiency is indispensable in the incorporation of numerical complexity in a pragmatic climate forecast system. From the resource optimization standpoint, the debate regarding, to what extent increased computing efficiency and expense on resources has reduced the signal-to-noise ratio and improved our understanding towards future climate states on different time scales, still continues. With the recent advancement of real time climate forecasts from different operational agencies with increased computational efficiencies and resources, it has become necessary to perform an objective evaluation of the high resolution operational monsoon forecasts to conform if the high resolution outlooks are skillful enough as compared to a low resolution version. In this paper, we have performed a quantitative comparison of the extended range (~2-3 weeks) forecasts of monsoon intraseasonal oscillations (MISO) obtained from the climate forecast system model version 2 developed at National Centre for Environmental Prediction USA at two different resolutions: T126 (~100 km) and T382 (~38 km). It is observed that, higher model resolution (T382) has provided better basic state for MISO along with large reduction in climatological biases in June-September precipitation than the lower resolution forecast (T126). However, compared to the computing resources, there is no significant improvement in the prediction skill from increased horizontal resolution
Glyoxal observations in the global marine boundary layer
No full textGlyoxal is an important intermediate species formed by the oxidation of common biogenic and anthropogenic volatile organic compounds such as isoprene, toluene, and acetylene. Although glyoxal has been shown to play an important role in urban and forested environments, its role in the open ocean environment is still not well understood, with only a few observations showing evidence for its presence in the open ocean marine boundary layer (MBL). In this study, we report observations of glyoxal from 10 field campaigns in different parts of the world's oceans. These observations together represent the largest database of glyoxal in the MBL. The measurements are made with similar instruments that have been used in the past, although the open ocean values reported here, average of about 25 parts per trillion by volume (pptv) with an upper limit of 40 pptv, are much lower than previously reported observations that were consistently higher than 40 pptv and had an upper limit of 140 pptv, highlighting the uncertainties in the differential optical absorption spectroscopy method for the retrieval of glyoxal. Despite retrieval uncertainties, the results reported in this work support previous suggestions that the currently known sources of glyoxal are insufficient to explain the average MBL concentrations. This suggests that there is an additional missing source, more than a magnitude larger than currently known sources, which is necessary to account for the observed atmospheric levels of glyoxal. Therefore, it could play a more important role in the MBL than previously considered. Key Points Largest database of glyoxal in the MBL Levels of glyoxal in the MBL are lower than previously reported Additional source of glyoxal needed to explain observations ©2014. American Geophysical Union. All Rights Reserved
Long-term trends observed in the middle atmosphere temperatures using ground based LIDARs and satellite borne measurements
Get PDFLong-term data available from Lidar systems located at three different locations namely São José dos Campos, Brazil (23.2° S, 45.8° W), Gadanki (13.5° N, 79.2° E) and Reunion (20.8° S, 55.5° E) have been used to investigate the long-term variations like Annual, Semi-annual, Quasi-biennial, El Nino Southern Oscillation and solar cycle. These oscillations are also extracted from simultaneous satellite borne measurements of HALogen Occultation Experiment (HALOE) instrument onboard UARS and SABER onboard TIMED over these stations making largest time series covering the entire middle atmosphere. A good agreement is found between the LIDAR and satellite-derived amplitudes and phases between 30 and 65 km altitude, which suggests that satellite measurements can be used to investigate the long-term trends globally. Latter measurements are extended to 80 km in order to further investigate these oscillations. Large difference in the amplitudes between the eastern pacific and western pacific is noticed in these oscillations. Changing from cooling trends in the stratosphere to warming trends in the mesosphere occurs more or less at altitude around 70 km altitude and this result agrees well with that observed by satellite measurements reported in the literature. The peak in the cooling trend does not occur at a fixed altitude in the stratosphere however maximum warming trend is observed around 75 km at all the stations. The observed long-term trends including various oscillations are compared with that reported with various techniques. © Author(s) 2014. CC Attribution 3.0 License
The linkages of anthropogenic emissions and meteorology in the rapid increase of particulate matter at a foothill city in the Arawali range of India
No full textThe city of Udaipur (24.58°N, 73.68°E) in the province of Rajasthan in the Western part of India has a special significance as it is surrounded by the Arawali mountain ranges on one side and desert on the other side. It is located around the foothills of the rocky Arawali range. It is on the world map due to its tourist attraction. The changing pattern in particulate matter (PM2.5 and PM10) during the past three years indicates an alarming increasing trend, posing a threat to its environment & tourism sector which regulates its economy to a period during the monsoon and distribution of particulate matter is found to be governed by the meteorology and changes the trend. The level of PM10, which was already above the threshold level in 2010, further increased in 2012. The trend is found to be rapid during the months of October & November where an increase by 37 is observed in 3 years. The level of PM2.5, which is the most hazardous for respiratory system diseases, has now started to cross the ambient air quality standards set by the World Health Organization. The impact is significant during winter when the inversion layer is down due to colder temperature and foreign tourists are a peak giving rise an increased morbidity rate. The linkages of local weather with an anthropogenically induced trend and long range transport of pollutants have been outlined
Trend analysis and change point detection of annual and seasonal precipitation and temperature series over southwest Iran
Get PDFThis paper presents results of trend analysis and change point detection of annual and seasonal precipitation, and mean temperature (TM), maximum temperature (TMAX) and minimum temperature (TMIN) time series of the period 1950-2007. Investigations were carried out for 50 precipitation stations and 39 temperature stations located in southwest Iran. Three statistical tests including Pettitt's test, Sequential Mann-Kendall test (SQ-MK test) and Mann-Kendall rank test (MK-test) were used for the analysis. The results obtained for precipitation series indicated that most stations showed insignificant trends in annual and seasonal series. Out of the stations which showed significant trends, highest numbers were observed during winter season while no significant trends were detected in summer precipitation. Moreover, no decreasing significant trends were detected by statistical tests in annual and seasonal precipitation series. The analysis of temperature trends revealed a significant increase during summer and spring seasons. TMAX was more stable than TMIN and TM, and winter was stable compared to summer, spring and autumn seasons. The results of change point detection indicated that most of the positive significant mutation points in TM, TMAX and TMIN began in the 1990s
Effect of major dust storm on optical, physical, and radiative properties of aerosols over coastal and urban environments in Western India
No full textThe present study deals with a major summertime dust storm event that occurred over the Arabian Desert, Saudi Arabia (SA), and the United Arab Emirates (UAE) and spread to Pakistan, the Arabian Sea, and Western India (in particular over Alibaug and Pune), using multi-satellite- and ground-based measurements. Analysis of the aerosol parameters retrieved over Alibaug and Pune from the ground-based MICROTOPS-II Sunphotometer, seven Aeronet Robotic Network (AERONET) stations, including Pune, and satellite (Moderate-resolution Imaging Spectroradiometer (MODIS)) and Ozone Monitoring Instrument ((OMI-Aura)) measurements shows significant changes on dusty days as compared with non-dusty days prior to and after the dust storm event. A large increase in aerosol optical depths (AODs) and decrease in Angstrom exponent (AE, α440-870 nm), showing the presence of a larger fraction of coarser particles comparable to those of other intense dust outbreak episodes worldwide, have been found at all these sites during the dust storm event. Higher observed AODs are considered to be the combined effect of desert dust and burning biomass/biofuel-induced aerosols. AERONET-retrieved mean aerosol volume size distributions (AVSDs) on non-dusty and dusty days are bimodal in nature at the stations of Pune, Kanpur, Jaipur, Karachi, and Lahore, while at the stations of KAUSTCampus (SA) and Mezaira (UAE), AVSDs are monomodal. This indicates that at the first five stations, the aerosol system is a complex mixture of fine- and coarse-mode aerosols with coarse mode exerting a strong influence on the system. Dust-induced turbid conditions triggered significant extinction of 30-40, in shortwave (SW) global solar irradiance, resulting in an increase of 57 and 74 in aerosol direct radiative forcing (ADRF) at Alibaug and Pune, respectively, causing perturbation in the radiation budget. The space-borne Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO)-retrieved aerosol vertical profiles reveal the presence of polluted dust (a mixture of fine- and coarse-mode aerosols), corroborating well with the aerosol behaviour captured by the MICROTOPS/AERONET measurements and MODIS retrievals over the study areas. The Dust Regional Atmospheric Model (BSC-DREAM8b) predictions are also found to be consistent with satellite retrievals, implying the ability of the model to monitor dust transport over the study region
Lightning and convective rain study in different parts of India
No full textThe effect of solar variability parameters (solar flux (F10.7cm), cosmic ray flux, sunspot numbers) and meteorological parameters on convective rainfall and lightning flashes in four different Indian regions of equal area is studied. Regions are selected having different topological, vegetation, proximity with ocean and habitat features. Solar variability shows statistically insignificant effect on lightning flash and convective rainfall. The seasonal variation of lightning flashes and convective rainfall in each region could be explained considering the variation of CAPE and surface temperature in that region. The dependence of lightning flashes and convective rainfall on meteorological parameters varies from region to region, as is evident from correlation studies. Lightning flashes is well correlated (R=0.81) with CAPE in region R1 and barely correlated (R=0.23, 0.24) in region R3 and R4 whereas rainfall is well correlated (R>0.68) in all the regions. Lightning flashes are better correlated (R>0.57) with temperature in R1, R2 and R4 and moderately correlated in R3 (R=0.44). Rainfall in R3 is very well correlated (R=0.91) with surface temperature and there is insignificant correlation in R1 (R=0.09). There is very good positive correlation (R>0.59) between cloud cover and convective rainfall in the entire region and well negative correlation (-0.83<R<-0.61) between OLR and convective rainfall. OLR and cloud cover show little impact on lightning flashes. Lightning flashes and convective rainfall show average positive correlation (0.48<R<0.53). Aerosol concentration is the largest in region R4 and showed an increasing trend between 2007 and 2011. Lightning flashes and convective rainfall are positively correlated (0.10<R<0.58) with aerosol concentration
Climatology of lightning activity over the Indian seas
No full textThe climatology of lightning activity over the Indian seas (Arabian Sea (AS) and Bay of Bengal (BoB)) has been studied using monthly satellite-based lightning flash count grid (0.5° × 0.5°) data from 1998 to 2007. These data have been used to investigate the annual and seasonal variations in lightning activity over the Indian seas. It was found that annual variations in flash rate density and sea surface temperature (SST) show a bimodal pattern with the first peak occurring in May and the second in October. The correlation coefficients between flash rate density and SSTs are 0.76 and 0.65 for the AS and BoB, respectively. Further, the relationship between flash rate density and a low pressure system (LPS) over the BoB shows that the formation of severe tropical cyclonic storms starts during April with the maximum number of storms forming during August. The performance of monsoon on a seasonal and monthly basis depends on the total number of lows, the formation of a depression in the monsoon trough, and the number of days with an LPS. Secular decreases in the number of lows and monsoon depressions were observed in 2000, 2002, and 2004. Overall, results indicate that the peaks in SST during April and September/October over the AS and the BoB may be responsible for advancing the onset of the southwest and northeast monsoon by 30–40 days