NOPR Collection:

Methane emission from open drain

Sun, 01 Mar 2015 00:00:00 GMT

Title: Methane emission from open drain Authors: Purkait, N N; Chakrabarty, D K Abstract: Solid waste that comes along with the wastewater from household gets deposited at the bottom of the drain. With passage of time, this solid waste starts decomposing and starts releasing methane. Methane is an important greenhouse gas, which is non-toxic but highly flammable. It is also an asphyxiant and can be fatal. Every year several people die for this reason while cleaning solid sewage of choked drains. Methane emission measurements from three drains of Kolkata were made during 2009-2010. The results are presented in this communication. It is found that methane emission from drains is ~4-100 times greater than that from paddy field. Data obtained in this work will be a valuable input for making reliable prediction of methane loading in the atmosphere and alert workers of the danger in order to take adequate safety measure before cleaning sewage sediments. Page(s): 56-59

A simple model for estimation of snow/ice surface temperature of Antarctic ice sheet using remotely sensed thermal band data

Sun, 01 Mar 2015 00:00:00 GMT

Title: A simple model for estimation of snow/ice surface temperature of Antarctic ice sheet using remotely sensed thermal band data Authors: Gusain, H S; Mishra, V D; Brar, Gursewak Singh; Ganju, Ashwagosha Abstract: In this paper, a model has been developed to estimate surface temperature of Antarctic ice sheet using thermal bands of Moderate Resolution Imaging Spectroradiometer (MODIS) sensor images and in situ surface temperature measurements. The brightness temperature of snow/ice surface of Antarctica has been estimated for MODIS bands 31 and 32 using Planck’s spectral radiation equation. Split window technique has been used to develop the model from brightness temperature and Automatic Weather Station recorded surface temperature. The model has been validated using in situ measurements of surface temperature of the ice sheet near Indian Antarctic Research Station ‘Maitri’. High coefficient of determination (R2 in the range 0.952 - 0.99) and low root mean square error (0.8 - 1.2°C) has been obtained between modeled and in situ recorded surface temperature. The model is easy to use and can generate the surface temperature maps at spatial resolution of 1.0 km. These maps can be useful in various glaciological, hydrological, climatological and ecological studies of the ice sheet. Page(s): 51-55

Rain attenuation using Ka and Ku band frequency beacons at Delhi Earth Station

Sun, 01 Mar 2015 00:00:00 GMT

Title: Rain attenuation using Ka and Ku band frequency beacons at Delhi Earth Station Authors: Sujimol, M R; Acharya, Rajat; Singh, Gajendra; Gupta, Ravi Kumar Abstract: Quantitative analysis and prediction of radio signal attenuation is necessary in order to improve the reliability of satellite-earth communication links and for economically efficient design. The Ka band suffers large attenuation due to rain and as most of the parts of India are situated in the tropical region, the impact of rain on Ka band propagation is severe. None of the existing ITU-R models is validated for prediction of rain attenuation over India and only a few over the tropical region and hence, it calls for a propagation experiment to validate the existing models. In this paper, study on the effect of rain attenuation on the propagation of satellite signals in Ka band has been carried out by receiving signal of frequency 20.199 GHz from the IPSTAR (Thaicom-4 Satellite) and a Ku band beacon signal of frequency 11.698 GHz from GSAT-8 satellite at Delhi Earth Station of ISRO. It has been observed that the difference between the ITU-R predicted rain attenuations and the observed rain attenuations for Ka band varies from 1.5 to 4.5 dB and that for Ku band from 2.1 to 3.7 dB. The long-term probability distribution of fade slope for any definite base value of attenuation is symmetric on both positive and negative sides and this feature is independent of frequency. This observation corroborates earlier findings. Page(s): 45-50

Atmospheric turbulences over Guwahati and their association with tropospheric dynamics

Sun, 01 Mar 2015 00:00:00 GMT

Title: Atmospheric turbulences over Guwahati and their association with tropospheric dynamics Authors: Medhi, A; Devi, M; Goswami, H; Barbara, A K Abstract: The paper presents an analysis of structure constant parameter (Cn²) over Guwahati (26.2°N, 91.75°E) in relation to tropospheric dynamics involving atmospheric variabilities, like temperature, potential temperature and specific humidity. Data collected from radiosonde operated at Guwahati are utilised for drawing seasonal profiles of Cn² up to the tropopause height. The results show that depending on season, the average values of Cn² may vary between 10^-14.5 and 10^-19 m^-2/3 and that their magnitude decreases gradually to reach a minimum of -18.3 m^-2/3at around 10 km and then starts increasing up to the tropopause height of 15-16 km. The analysis, further, demonstrates that Cn² value reaches maximum in summer and minimum in winter, within the height range of 1-10 km. But beyond the altitude of 10 km, Cn² shows higher values in winter as compared to its summer time counterparts. The paper also highlights that at pre earthquake (EQ) ambiences, this parameter may dip down by two to three orders of magnitude from its average normal range. The seasonal transition pattern of Cn²with height and the EQ time changes in Cn² features are put to a correlative analysis with the tropospheric dynamics for an explanation. Page(s): 35-44