Satellite-based analysis of the role of land use/land cover and vegetation density on surface temperature regime of Delhi,India

The knowledge of the surface temperature is important to a range of issues and themes in earth sciences central to urban climatology, global environmental change and human-environment interactions. The study analyses land surface temperature (LST) estimation using temporal ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) datasets (day time and night time) over National Capital Territory Delhi using the surface emissivity information at pixel level. The spatial variations of LST over different land use/land cover (LU/LC) at day time and night time were analysed and relationship between the spatial distribution of LU/LC and vegetation density with LST was developed. Minimum noise fraction (MNF) was used for LU/LC classification which gave better accuracy than classification with original bands. The satellite derived emissivity values were found to be in good agreement with literature and field measured values. It was observed that fallow land, waste land/bare soil, commercial/industrial and high dense built-up area have high surface temperature values during day time, compared to those over water bodies, agricultural cropland, and dense vegetation. During night time high surface temperature values are found over high dense built-up, water bodies, commercial/industrial and low dense built-up than over fallow land, dense vegetation and agricultural cropland. It was found that there is a strong negative correlation between surface temperature and NDVI over dense vegetation, sparse vegetation and low dense built-up area while with fraction vegetation cover, it indicates a moderate negative correlation. The results suggest that the methodology is feasible to estimate NDVI, surface emissivity and surface temperature with reasonable accuracy over heterogeneous urban area. The analysis also indicates that the relationship between the spatial distribution of LU/LC and vegetation density is closely related to the development of urban heat islands (UHI).     

Evidence of high PM2.5 strong acidity in ammonia-rich atmosphere of Guangzhou,China: Transition in pathways of ambient ammonia to form aerosol ammonium at [NH4+]/[SO42–] = 1.5

In this study, 24-h PM_2.5 samples were collected using Harvard Honeycomb denuder/filter-pack system during different seasons in 2006 and 2007 at an urban site in Guangzhou, China. The particles collected in this study were generally acidic (average strong acidity ([H⁺]) ~ 70 nmol m^? 3). Interestingly, aerosol sulfate was not fully neutralized in the ammonia-rich atmosphere (NH₃ ~ 30 ppb) and even when NH₄⁺]/[SO₄^2?] was larger than 2. Consequently, strong acidity ([H⁺]) as high as 170 nmol m^? 3 was observed in these samples. The kinetic rate of neutralization of acidity (acidic sulfate) by ambient ammonia was significantly higher than the rate of formation of ammonium nitrate involving HNO₃ and NH₃ for [NH₄⁺]/[SO₄^2?] ≤ 1.5 and much lower for NH₄⁺]/[SO₄^2?] > 1.5. Therefore, higher nitrate principally formed via homogeneous gas phase reactions involving ammonia and nitric acid were observed for [NH₄⁺]/[SO₄^2?] > 1.5. However, little nitrate, probably formed via heterogeneous processes e.g. reaction of HNO₃ with sea salt or crustal species, was observed for [NH₄⁺]/[SO₄^2?] ≤ 1.5. These demonstrate a clear transition in the pathways of ambient ammonia to form aerosol ammonium at [NH₄⁺]/[SO₄^2?] = 1.5 and evidently explain the observed high acidity due to the unneutralized sulfate in the ammonium-rich aerosol (NH₄⁺]/[SO₄^2?] > 1.5). In fact, the measured acidity was almost similar to the excess acid defined as the acid that remains at [NH₄⁺]/[SO₄^2?] = 1.5 due to the un-neutralized fraction of sulfate ([H⁺] = 0.5[SO₄^2?]). The presence of high excess acid and ammonium nitrate significantly lowered the deliquescence relative humidity of ammonium sulfate (from 80% to 40%) in the ammonium-rich samples.     

The time-domain magnetotelluric response over three-layer earth models

Magnetotelluric data observed in frequency and time domains are expressed as apparent resistivity. the apparent resistivity is a weighted spatial average of the subsurface resistivity distribution. In this paper, we develop analytical expressions to compute the apparent resistivity in the time domain for various three-layer earth models. the present approach to computing the magnetotelluric response in the time domain is found to overcome the problems encountered by the method of images. the magnetotelluric response in the time domain for various three-level models have been computed and shown graphically. the time-domain responses show a characteristic behaviour with a small change in layered parameters (resistivity and thickness of the layers), whereas frequency-domain responses do not show such behaviour. This characteristic behaviour of time-domain magnetotelluric sounding curves will be useful in the qualitative interpretation of field data.     

Evaluation of TRMM multi-satellite precipitation analysis (TMPA) against terrestrial measurement over a humid sub-tropical basin,India

To support the GPM mission which is homologous to its predecessor, the Tropical Rainfall Measuring Mission (TRMM), this study has been undertaken to evaluate the accuracy of Tropical Rainfall Measuring Mission multi-satellite precipitation analysis (TMPA) daily-accumulated precipitation products for 5 years (2008–2012) using the statistical methods and contingency table method. The analysis was performed on daily, monthly, seasonal and yearly basis. The TMPA precipitation estimates were also evaluated for each grid point i.e. 0.25° × 0.25° and for 18 rain gauge stations of the Betwa River basin, India. Results indicated that TMPA precipitation overestimates the daily and monthly precipitation in general, particularly for the middle sub-basin in the non-monsoon season. Furthermore, precision of TMPA precipitation estimates declines with the decrease of altitude at both grid and sub-basin scale. The study also revealed that TMPA precipitation estimates provide better accuracy in the upstream of the basin compared to downstream basin. Nevertheless, the detection capability of daily TMPA precipitation improves with increase in altitude for drizzle rain events. However, the detection capability decreases during non-monsoon and monsoon seasons when capturing moderate and heavy rain events, respectively. The veracity of TMPA precipitation estimates was improved during the rainy season than during the dry season at all scenarios investigated. The analyses suggest that there is a need for better precipitation estimation algorithm and extensive accuracy verification against terrestrial precipitation measurement to capture the different types of rain events more reliably over the sub-humid tropical regions of India.     

Fiber Optic Network Technology For Distributed Long Baseline Radio Telescopes

The construction costs of distributed radio telescopes are to a great extent determined by the deployment costs of the fiber optic data transport network that is needed to transport the received information to the data processor(s). As such, the baseline and data rates that are feasible for a specified amount of money are determined by the status of the technology and deployment costs of the communication network. In this paper the present day data transport status is described and, using a costing model, the most attractive data transport technologies are determined, taking the LOFAR telescope (ASTRON, 2005) as an example. In the outlook, the near-term data transport technology developments are described.     

Effect of autocorrelation on temporal trends in rainfall in a valley region at the foothills of Indian Himalayas

This study examines the effect of autocorrelation on step and monotonic trends in seasonal and annual rainfall. Initially, for step change, modified-Pettitt test is applied in two ways. First, using the corrected and unbiased trend-free-pre-whitening (TFPWcu) approach. Second, using a new approach in which time series is modelled by intervention analysis for modified Pettitt test. Subsequently, for monotonic trends, Mann–Kendall (MK) and six approaches of modified Mann–Kendall (MMK) test are applied to NCDC data for period 1901–2012 and its sub-periods. Approaches of MMK include pre-whitening (PW), trend-free-pre-whitening (TFPW), TFPWcu, two Variance Correction Approaches (VCAs) based on empirical formula (VCA:CF1) and Monte-Carlo-Simulations (VCA:CF2) and long term persistence (MK-LTP). A single change point is identified in 1970 for annual and monsoon rainfall from original and modified-Pettitt’s test using TFPWcu, while time series modelling approach has not exhibited any change point. Process shift in rainfall series is also studied using CUSUM and multiple change points are identified using Segment-Neighbourhood method. Outcomes of MMK show that TFPWcu is able to efficiently limit the effect of autocorrelation and may be preferred over PW and TFPW. The VCA:CF2 is not dependent on whole autocorrelation structure and corrects variance of all data series using lag-1 autocorrelation and may be preferred over VCA:CF1. MK-LTP considers long term persistence and it has exhibited presence of weaker trends than exhibited by other approaches. VCA:CF2 and MK-LTP are used to study trends of rainfall in Dehradun.     

Field evidences showing rapid frontal degeneration of the Kangriz glacier,western Himalayas,Jammu & Kashmir

Life cycle of glaciers in the Himalayan region has notably changed due to the climatic variability since last few decades. Glaciers across the world and specially the Himalayan glaciers have shown large scale degeneration in the last few decades. Himalayan glaciers serve as an important fresh water resource for the downstream communities, who are dependent on this water for domestic and other purposes. Therefore, glacier shrinkage and the associated hydrological changes pose a significant problem for regional-scale water budgets and resource management. These issues necessitate the regular and rigorous monitoring of the wastage pattern of the Himalayan glaciers in field and using satellite remote sensing data. In this work, we report rapid and enhanced degeneration of the frontal part of the Kangriz glacier, Jammu and Kashmir (J & K), in terms of surface melting, debris cover, snout characteristics and meltwater discharge. Ablation data acquired during 2016–2017 shows the average lowering of the frontal part of the glacier to be ~148 ± 34 cm, one-third of which was found to have occurred within a 13 day time period in September, 2017. Also, the quantum of ice melt was found to be inversely influenced (r = -0.84) by the debris thickness. 15 day meltwater discharge measurement revealed its strong relationship with snout disintegration pattern, evidenced twice during the said time period. Volume of water discharged from the glacier was estimated to be 7.91×10⁶ m³ for the measurement duration. Also, mean daily discharge estimated for the 15 days interval showed good positive correction (r = 0.78) with temperature indicating the direct dependency of the former on land surface temperature conditions of the region. Besides the lowering and discharge observations, the frequent ice-block break-offs at the glacier snout further enhance its overall drastic degeneration. The study suggests that, being the largest glacier in the Suru basin, the Kangriz glacier needs to be continuously monitored in order to understand its glacio-hydrological conditions.     

Studies on biodiversity using semivariogram approach from IRS-IC LISS-III data

Present study attempts to utilise the spatial information from IRS-IC LISS-III satellite data, through, tie use of Semivartogram apprqatfu for analyzing the overstorey. diversity In forest stands, Semivariance has been calculated for all the pixels in I5x15 pixel window for each of the forest stand using digital numbers from near infrared channel Variation in semivariance has been correlated to stand density and species composition. Analysis of averaged semivariance for overall diversity of forest stands suggested, decreasing semi variance in the order, mixed dry (feciduous forests, mixed scrub forests followed by dry deciduous forest Semivariance has been found to be highly Correlated to tree density (R² = 0.96) suggesting semivariograms as one of the measures for studies on tree density, canapy cover and diversity patterns.     

LOCAL SCOUR AROUND BRIDGE ABUTMENTS

1 INTRODUCTION The protrusion of a bridge abutment or a spur dike into the main channel creates a disturbance and obstruction to the otherwise equilibrium state of sediment transportation in an alluvial river. The flow accelerates and separates at the upstream face of the abutment as it moves past the obstacle, creating a vortex trail that moves downstream in a direction approximately perpendicular to the structure. The result is that the bed around the structure is eroded locally. The l…