A study of tropical tropopause using MST radar

International audienceUsing the MST radar data of vertical wind, the characteristics of the tropical tropopause, following four different definitions, depending on 1) temperature lapse rate, 2) cold point, 3) convective outflow and 4) potential temperature lapse rate minimum, are studied. From the vertical wind data of the radar, the altitude profiles of temperature and horizontal divergence are derived, from which the tropopause levels corresponding to i) the lapse rate ii) cold point iii) convective outflow level and iv) potential temperature lapse rate minimum are determined. The convective outflow level and hence the convective tropopause altitude is determined, for the first time using the MST radar data. The tropopause altitudes and temperatures obtained following the four definitions are compared on a day-to-day basis for the summer and winter seasons. Winter and summer differences in the tropopause altitude and temperature are also studied. Keywords. Meteorology and atmospheric dynamics (convective process; middle atmosphere dynamics; tropical meteorology

Assessment of GPS radiosonde descent data

Radiosondes are widely used to obtain basic meteorological parameters such as pressure (<i>P</i>), temperature (<i>T</i>), relative humidity (RH) and horizontal winds during the balloon ascent up to the altitude of balloon burst, usually ~ 32–35 km. Data from the radiosondes released from Gadanki (13.5° N, 79.2° E), a tropical station in India, have been collected during the ascent and during the descent as well without attaching any parachute or its equivalent since the year 2008. In the present study an attempt has been made to characterize the radiosonde descent data with the main objective of exploring its usefulness and reliability for scientific purposes. We compared the data obtained during ascent and descent phases of the same sounding. The mean differences in <i>T</i>, RH and horizontal winds between ascent and descent data are found to be small and are sometimes even within the uncertainty of the measurements and/or expected diurnal variation itself. The very good consistency observed between the ascent and the descent data shows that one more profile of the meteorological parameters can be constructed within 3 h of time of balloon launch practically at no additional cost. Further checks are done by utilizing the 3-hourly radiosonde observations collected during the Tropical Tropopause Dynamics campaigns conducted at Gadanki. In the process of checking the consistency between the radiosonde ascent and descent data, several new findings are arrived at and are reported in this study. In general, it has taken more than half an hour for the balloon to reach the ground from the burst altitude. It is also observed that the fall velocity is close to 10 m s⁻¹ near the surface. Finally, it is suggested to record the observations also when the balloon is descending as this information is useful for scientific purposes

First results from the CAWSES-India Tidal Campaign

The first CAWSES-India Tidal Campaign was conducted by the Indian scientific community during March–April 2006. The objectives of this campaign were: (1) To determine the characteristics of tides in the troposphere and lower stratosphere (0–20 km) and mesosphere and lower thermosphere (MLT) region (80–100 km), (2) to explore and identify what lower atmospheric processes drive middle atmospheric tides in the Indian continental region and (3) to provide information on those short-term variabilities of MLT tides that are likely to have an impact on the ionospheric variabilities and contribute to the upper atmospheric weather. Data sets from experiments conducted at the three low latitude radar sites, namely, Trivandrum (8.5&amp;deg; N, 76.9&amp;deg; E), Tirunelveli (8.7&amp;deg; N, 77.8&amp;deg; E) and Gadanki (13.5&amp;deg; N, 79.2&amp;deg; E) and fortnightly rocket launches from Thumba were made use of in this study. An important observational finding reported in this work is that the radar observations at Tirunelveli/Trivandrum indicate the presence of 15–20 day modulation of diurnal tide activity at MLT heights during the February–March period. A similar variation in the OLR fields in the western Pacific (120–160&amp;deg; longitude region) suggests a possible link between the observed tidal variabilities and the variations in the deep tropical convection through the nonmigrating tides it generates

PAN SHARPENING USING RELATIVE SPECTRAL RESPONSE OF SENSOR FOR CARTOSAT-1 PAN AND RESOURCESAT LISS-4 MX DATA

Most of the Indian remote sensing systems, provide sensors with one high spatial resolution panchromatic (PAN) and several multispectral (MS) bands. An increasing number of applications, such as feature detection, change monitoring, and land cover classification, often demand the use of images with both high spatial and high spectral resolution. Image fusion or pan sharpening, is a technique to enhance the spatial resolution. The most significant problem in the traditional fusion methods is spectral distortion of fused images. The main reason for this being, the physical spectral characteristic of the sensors are not considered during the fusion process, resulting in undesirable effects such as modified spectral signatures resulting in classification errors and resolution over injection. For most earth resource satellites which provide both PAN and MS bands, in ideal condition, all MS bands would be well separated and would cover exactly the same wavelengths as the PAN band. Theoretically, the measured energy in the PAN band can be obtained with the summation of corresponding MS bands. As the measured energy in an individual channel is the sum of incoming radiation and relative spectral response: Lk&thinsp;=&thinsp;L(&lambda;)&thinsp;Rk(&lambda;); where &lambda; is the wavelength, the in-band radiance, L(&lambda;) at aperture spectral radiance and Rk(&lambda;) the peak-normalized spectral response. Therefore, the energy in PAN band can be estimated by defining weights as follows: Pan&thinsp;=&thinsp;wR&thinsp;R&thinsp;+&thinsp;wG&thinsp;G&thinsp;+&thinsp;wNIR NIR&thinsp;+ other; where Pan, G, R, NIR represent the radiance of individual spectral bands wG, wR, wNIR are the weights of corresponding MS bands and other for the influence of the spectral range which is missing from MS bands but still covered with the PAN band. In this paper, a novel spectral preservation fusion method for remotely sensed images using Cartosat-1 PAN and Resourcesat-Liss4 Mx data is presented by considering the physical characteristics of the sensors. It is based on the curvelet transform using relative spectral response (RSR) values of the sensor, improved in two parts: 1) the construction of PAN image using RSR values and the curvelet components, 2) the injection method of detail information. The performance and efficiency of the proposed method is compared with traditional IHS, wavelet based methods both visually and quantitatively. The results show that the proposed method preserves spatial details and minimize spectral distortion.</p

Exactly solvable toy models of unconventional magnetic alloys: Bethe Ansatz versus Renormalization Group method

We propose toy models of unconventional magnetic alloys, in which the density of band states, $\rho(\epsilon)$, and hybridization, $t(\epsilon)$, are energy dependent; it is assumed, however, that $t^2(\epsilon)\propto\rho^{-1}(\epsilon)$, and hence an effective electron-impurity coupling $\Gamma(\epsilon)=\rho(\epsilon)t^2(\epsilon)$ is energy independent. In the renormalization group approach, the physics of the system is assumed to be governed by $\Gamma(\epsilon)$ only rather than by separate forms of $\rho(\epsilon)$ and $t(\epsilon)$. However, an exact Bethe Ansatz solution of the toy Anderson model demonstrates a crucial role of a form of inverse band dispersion $k(\epsilon)$.Comment: A final version. A previous one has been sent to Archive because of my technical mistake. Sorr

Lidar Observations of aerosol layers just below the tropopause level during IFP-INDOEX

A lidar system has been used at Gadanki (13.5º, 79.2ºE) to study the characteristics of aerosol layer (cloud) occurring just below the tropical tropopause. The preliminary results of the lidar observations indicate that the cloud occurs ~ 2 km below the tropopause. The top and bottom edges of the cloud have propensity for ice crystal presence with liquid droplets/ vapours in-between. The clouds show temporal fluctuations (in their backscattering ratio) with temporal scales of the order of 30–90 min

Studies on biosorption of nickel using immobilized fungus, Rhizomucor tauricus

Rhizomucor tauricus, an industrial fungus, was immobilized in sodium alginate and used as adsorbent for the removal of nickel from aqueous solutions. The biosorption capacity of Ni(II) was found to be 394 mg/g of immobilized biomass. It was observed that an increase in pH from 3 to 6 increased the percent adsorption, and an increase in liquid-to-solid ratio from 2 to 10 increased the metal uptake. The percent adsorption was increased when increasing the initial metal concentration from 25 to 100 mg/L. The equilibrium biosorption data was evaluated by Langmuir, Freundlich, and Langmuir-Freundlich (L-R) isotherm models, and was best described by the Langmuir and Freundlich isotherms. FTIR analysis revealed that –NH (bending), C–H (stretching), C=O (stretching), and –OH functional groups were mainly responsible for Ni(II) biosorption. Thus, this study demonstrated that the immobilized Rhizomucor tauricus biomass could be used as an adsorbent for the treatment of Ni(II) from aqueous solution

Validation of the COSMIC Radio Occultation Data over Gadanki (13.48°N, 79.2°E): A Tropical Region

Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC), consisting of six Low Earth Orbit (LEO) Global Position System (GPS) receivers, on board the Formosat Satellite 3 (FORMOSAT-3) is providing dense observations of density, refractivity, temperature and water vapor profiles of the neutral atmosphere since middle of July 2006. Special radiosonde (Väisälä) campaign was conducted at Gadanki (13.48°N, 79.18°E), a tropical site in India, during July 2006 to March 2007 to validate these meteorological parameters. Co-located Nd: YAG Rayleigh lidar was also operated during the overpass of COSMIC and is utilized to validate the temperatures in the height range of 30 to 40 km. Atotal of 142 overpasses occurred during the above mentioned period within 300 km distance from Gadanki out of which 41 overpasses occurred within a time difference of ±4 hours of radiosonde launch. In addition, 18 overpasses occurred within the time difference of ±4 hours of lidar operation. A detailed comparison has been made with all these overpasses for the refractivity, temperature and water vapor obtained from COSMIC. The water vapor comparison has shown generally a good agreement with a mean difference of 5 - 10% below 6 - 7 km. Although there is a colder bias between COSMIC and radiosonde, a very good comparison in temperature is also found between 10 and 27 km with a mean difference of less than 1 K (RMS difference is only 0.64 K). There exists a large difference in temperature of about 8 K between 30 and 40 km (between COSMIC and lidar). Possible reasons for these large differences are given. There was one event that occurred just over Gadanki for which a detailed comparison has been made with special emphasis on water vapor retrievals. Sensitivity test is also done on the fractional difference in N for the event that occurred on 24 July 2006 between COSMIC (1D-var) and radiosonde and found that pressure plays a key role than temperature in determining the refractivity

A semi-synthetic chickpea flour based diet for long-term maintenance of laboratory culture of helicoverpa armigera

Artificial rearing of insects in the laboratory is a pre-requisite for undertaking studies on insecticide/ biopesticide bioassays, and evaluation of germplasm, segregating breeding material, mapping populations, and transgenic plants for resistance to insects. For successful rearing of insects in the laboratory, there is need for standardizing a semi-synthetic diet that supports survival and development of the insect for several generations. We tested different semi-‘synthetic diets for rearing the legume pod borer, Helicoverpa armigera for two generations under laboratory conditions. All the semi-synthetic diets tested supported the growth and development of H. armigera up to adult emergence, but there were significant differences in survival and development and fecundity on different diets. The highest larval survival was observed in the wheatgerm based diet in first (97.5%) and second generation (93.5%), followed by chickpea based modified diet (93.75% survival in both the generations). The lowest larval weights (270.7 and 283.7 mg) were recorded in the tapioca granules diet in 1st and 2nd generation, respectively. The adult emergence ranged from 68.7 to 83.3%, and 60.4 to 81.2% in the 1st and 2nd generation, respectively. Least fecundity was observed in the tapioca granules based diet (422 and 603 eggs per female) in both the generations, but the differences were not significant. Complete or partial replacement of agar-agar with tapioca granules was not suitable for use in artificial diets. The results indicated that modified chickpea flour based diet was quite appropriate for rearing H. armigera under laboratory condition