Evaluation of irrigation management in a Canal Command area based on Agrometeorology and Remote Sensing

Efficacy of irrigation management of wheat and mustard crops grown in Western Yamuna Canal Command area was determined in the present study from agro-climatic data merged with Maximum Likelihood Classified (MXL) satellite image and from irrigation scheduling efficiencies obtained through FAO model CROPWAT. For computing irrigation scheduling efficiencies, amount of water supplied at different growth stages, soil water depletion and crop water need have been taken into account. Agro-meteorological data in combination with MXL classified crop map approximated the deficiency of applied irrigation amount compared to requirement. Irrigations at 35-80 Days After Sowing (DAS) for two times of applications, 30-60-90 DAS for three, 21-50-80-110 DAS in case of four and 20-45-70-90-120 DAS in case of five irrigations have yielded better scheduling efficiencies for wheat than other times of applications in all soil associations.     

Estimating gross primary productivity of a tropical forest ecosystem over north-east India using LAI and meteorological variables

Tropical forests act as a major sink of atmospheric carbon dioxide, and store large amounts of carbon in biomass. India is a tropical country with regions of dense vegetation and high biodiversity. However due to the paucity of observations, the carbon sequestration potential of these forests could not be assessed in detail so far. To address this gap, several flux towers were erected over different ecosystems in India by Indian Institute of Tropical Meteorology as part of the MetFlux India project funded by MoES (Ministry of Earth Sciences, Government of India). A 50 m tall tower was set up over a semi-evergreen moist deciduous forest named Kaziranga National Park in north-eastern part of India which houses a significant stretch of local forest cover. Climatically this region is identified to be humid sub-tropical. Here we report first generation of the in situ meteorological observations and leaf area index (LAI) measurements from this site. LAI obtained from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) is compared with the in situ measured LAI. We use these in situ measurements to calculate the total gross photosynthesis (or gross primary productivity, GPP) of the forest using a calibrated model. LAI and GPP show prominent seasonal variation. LAI ranges between 0.75 in winter to 3.25 in summer. Annual GPP is estimated to be \(2.11\,\hbox {kg C m}^{-2} \, \hbox {year}^{-1}\).     

Topographic effects on telluric field measurements

Using the Schwartz-Christofel transformation and numerical integration, the effect of a sloping topographic irregularity on the telluric field measurements in a sedimentary basin is estimated. Results show that in the vicinity of the topographic feature, the distortion introduced would increase with the angle of inclination of the sloping feature. It is noticed that, for moderate inclinations (20°–50°), the telluric field measured near the topographic feature is within 10% of its undisturbed value for distance greater than 0.1H–0.3H from the topographic feature, whereH is the thickness of the sedimentary column overlying the resistive basement. Suitable charts are prepared to aid as means to arrive at the estimates of errors for various angles of inclinations of such topographic feature and also to help in formulating approximate rules of thumb for selection of station sites in a field survey to minimize such topographic effects.     

Effect of Single Species or Mixed Algal (Chlorella vulgaris and Scenedesmus acutus) Diets on the Life Table Demography of Brachionus calyciflorus and Brachionus patulus (Rotifera: Brachionidae)

We tested the effect of two algal diets (Chlorella vulgaris at 1 · 10⁶ cells mL^?1and Scenedesmus acutus at 0.57 · 10⁶ cells mL^?1) offered alone or in combination (50 % each, 75 % or 25 % of either alga), at a total dry weight of 14.2 μg mL^?1on the life table demography of two rotifer species, Brachionus calyciflorus and Brachionus patulus. Data on fecundity indicated that, for any given algal food type or combination of food types, B. calyciflorus had a higher rate of offspring production than B. patulus. Regardless of the rotifer species, the average lifespan varied from 4 to 6 days. The gross and net reproductive rates were higher for B. calyciflorus than for B. patulus. These values ranged from 45 to 71 offspring female^?1 lifespan^?1 and 15 to 24 offspring female^?1 lifespan^?1, respectively, for B. calyciflorus. Generation times (around 4…5 days) were similar for both rotifer species in most of the treatments. Whatever the algal food combination, the rate of population increase (d^?1) of B. patulus was less than half (i.e. 45 %) of that for B. calyciflorus. The observed differences in the life history variables of Brachionus probably explain species‐specific adaptations to the changing phytoplankton composition occurring seasonally in natural waterbodies.     

VV Orionis – improved elements

TheUBV light curves obtained by Duerbeck (1975) andHa (wide) and Ha (narrow) light curves obtained by Chambliss & Davan (1987) of the detached eclipsing binary VV Orionis (VV Ori) were analysed using the Wilson-Devinney method fixing the two parametersT _h (25,000 K) and q(0.4172), resulting in the following absolute elements:A = 13.605 ± 0.03 LR_⊙,R _h = 5.03 ±0.03R _⊙, R_c = 2.43 ±0.02R _⊙,M _bol,h = -5.18 ± 0.11,M _bol,c = -1.54 ± 0.06,m _h =10.81 + 0.42m _⊙ andm _c = 4.51 ± 0.41m _⊙. The de-reddened colours obtained from applying the reddening corrections ofE(B-V) = 0^m.05 andE(U-B) = O ^m .04, and the derived temperatures of the components, gave spectral types ofB 1.5V for the primary and 54-5V with anUV excess of 0 ^m ·3 for the secondary component. A comparison of the logL and logT _e of the components with the observed ZAMS shows the primary component to be a little above and the secondary component to be a little below/or on the ZAMS. A comparison of the properties of the components of VV Ori and a few other detached systems with the normal stars in the logL, logR and logT _e versus logm planes, indicated a need for either a readjustment of the scales of the above parameters or modifications in the theoretical models. From the position of the components on the evolutionary tracks of Pop I composition computed by Schaller et al. (1992) it is noticed that while the primary component of W Ori had slightly evolved along the main-sequence, its secondary is still unevolved. The age of VV Ori is found to be 10 ± 1 million years and it is at a distance of 368 ± 10 pc.     

Large Area X-Ray Proportional Counter (LAXPC) Instrument on AstroSat and Some Preliminary Results from its Performance in the Orbit

Large area X-ray propositional counter (LAXPC) instrument on AstroSat is aimed at providing high time resolution X-ray observations in 3–80 keV energy band with moderate energy resolution. To achieve large collecting area, a cluster of three co-aligned identical LAXPC detectors, is used to realize an effective area in access of \({\sim }6000\,\hbox {cm}^{2}\) at 15 keV. The large detection volume of the LAXPC detectors, filled with xenon gas at \({\sim }\)2 atmosphere pressure, results in detection efficiency greater than 50%, above 30 keV. In this article, we present salient features of the LAXPC detectors, their testing and characterization in the laboratory prior to launch and calibration in the orbit. Some preliminary results on timing and spectral characteristics of a few X-ray binaries and other type of sources, are briefly discussed to demonstrate that the LAXPC instrument is performing as planned in the orbit.     

Stability Dependence of the Eddy-Accumulation Coefficients for Momentum and Scalars

From a set of turbulence data collected with a three-axis sonic anemometer/thermometer and described in a companion paper, we simulate the eddy-accumulation process for sensible heat and momentum fluxes. The resulting eddy-accumulation coefficient for momentum clearly depends on surface-layer stability; at neutral stability, its value is 0.63. On supplementing the scalar eddy-accumulation coefficients that we derive from our sensible heat flux data with values of sensible and latent heat flux coefficients reported by Businger and Oncley, we also find that scalar eddy-accumulation coefficients depend on stability, though more weakly than does the momentum coefficient. The coefficients for sensible and latent heat show no significant difference; we, thus, fit them with one function of stability whose value is 0.52 for neutral stratification.     

Photometry of the RS CVn type eclipsing binary UV piscium

The analysis of the UBV photoelectric study of the short period RS CVn eclipsing binary, UV Psc, has suggested that the primary is a transit with _e=27°,i=88 _. ^o 5, andk=0.75. The spectral type and luminosity of the hotter component is estimated to be G4-6V and that of the cooler component to be K0-2V. Absolute dimensions for the components of UV Psc were derived by combining the present analysis with that of the spectroscopic analysis given by Popper.The out-of-eclipse observations have showed large amount of scatter and an investigation of this showed that hotter component could be an intrinscic variable. No periodicity for this variation has been fixed due to lack of sufficient data.Paper presented at the Lembang-Bamberg IAU Colloquium No.80 on Double Stars: Physical Properties and Generic Relations, held at Bandung, Indonesia, 3–7 June, 1983.     

Landuse/Landcover change detection through remote sensing and its climatic implications in the godavari delta region

Interpretation of multi-date satellite imagery has revealed changes in land use/land cover pattern in the Godavari deltaic region during the past 26 years. The area under intensive agriculture has increased from 1459 to 3500 km² and the extent of wetland from 368 to 648 km² during the period 1973-1999, while the seasonal fallow has decreased by 2321 km². Analysis of the climatic data of 1970-1998 from different stations covering the entire 5100 km² area of the delta indicated that the day time temperatures have decreased by 0.2° C to 0.7° C, while the night time temperatures have increased by 0.5° C to 0.6° C during the past three decades. At the same time the rainfall has increased by about 75 to 479 mm. These trends in the climatic parameters arc attributed to the increased vegetation cover and wetland extent in the Godavari deltaic region.     

Photometric and spectroscopic study of R CMa

UBV light curves and spectrograms of R CMa obtained with the 48-inch telescope of Japal-Rangapur Observatory during 1980–82 have been used for deriving the eclipse and orbital elements as well as the absolute dimensions of the components. The primary is found to be a Main-Sequence F2V star of mass 1.52M and the secondary a subgiant star of spectral type G8 and mass 0.20M which fills its Roche lobe, in agreement with Kopal and Shapley (1956) results, Kopal (1959), or Sahade's (1963) results. From a consideration of the possible evolution of this system it is concluded that a large fraction of the original mass of the secondary is lost from the system. A study of the period changes indicates the possible presence of a third component of mass of about 0.5M which is most likely to be anM dwarf.Paper presented at the Lembang-Bamberg IAU Colloquium No. 80 on Double Stars: Physical Properties and Generic Relations, held at Bandung, Indonesia, 3–7 June, 1983.