http://nopr.niscair.res.in/handle/123456789/2411 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/2459 Title: Effect of long-term ozone trend on night airglow intensity of Li 6708 Å at Dumdum (22.5°N, 88.5°E) and Halley Bay (76°S, 27°W) <br/> <br/>Authors: Jana, P K; Sarkar, D; Das, P <br/> <br/>Abstract: The paper presents the effect of O3 depletion on night airglow emission of Li 6708 Å line at Dumdum (22.5°N, 88.5°E), India and Halley Bay (76°S, 27°W), a British Antarctic Service Station. Calculations based on chemical kinetics show that the airglow intensity of Li 6708 Å line will also be affected due to the depletion of O3 concentration. The nature of yearly variation and seasonal variation of intensity of Li 6708 Å line for the above two stations are shown and compared. It is shown that the rate of decrease of intensity of Li 6708 Å line is comparatively more at Halley Bay due to dramatic decrease of Antarctic O3 concentration. <br/> <br/>Page(s): 326-332 http://nopr.niscair.res.in/handle/123456789/2455 Title: Thermal diffusivity of soils in iso-hyperthermic temperature regime by harmonic analysis <br/> <br/>Authors: Tessy, Chacko P; Renuka, G <br/> <br/>Abstract: Soil temperatures at various depths at three stations in Kerala were subjected to harmonic analysis for a period of seven years. The amplitude of soil temperature wave at various depths decreases with higher order of harmonics. The thermal diffusivity of various soil layers for the first three harmonics have been calculated using amplitudes and phase angles of the soil temperature wave. The combined effect of first three harmonics gives more reliable values for thermal diffusivity in different soil layers. <br/> <br/>Page(s): 360-365 http://nopr.niscair.res.in/handle/123456789/2454 Title: Lower atmospheric water vapour measurement at coastal Trivandrum (8.33°N, 77°E) using a high resolution Raman lidar <br/> <br/>Authors: Radhakrishnan, S R; Satyanarayana, M; Pillai, V P Mahadevan; Presennakumar, B; Rao, D Ramakrishna; Murthy, V S <br/> <br/>Abstract: Near simultaneous measurement of atmospheric aerosol and water vapour is described in this paper, making use of the Nd: YAG laser based multiwavelength lidar system, designed and developed in-house at Space Physics Laboratory, Vikram Sarabhai Space Centre, Trivandrum, India. In the present study, the vibrational Raman scattered signals of N₂ and H₂O were used for the measurement of atmospheric water vapour and aerosol extinction. Nighttime water vapour profiles are obtained in the 1-6 km altitude regions in the lower troposphere. Necessary aerosol corrections to water vapour profiles are also done. Lidar derived water vapour profiles are compared with the profiles calculated from High resolution Regional Weather Model (HRM) available during the same period. <br/> <br/>Page(s): 353-359 http://nopr.niscair.res.in/handle/123456789/2453 Title: Estimation of rain parameters from spectral moments of L-band wind profiler using Multi-Layer Perceptron Network model <br/> <br/>Authors: Konwar, Mahen; Sarma, Diganta Kumar; Sharma, Sanjay; De, U. K.; Pal, S.; Das, Jyotirmoy <br/> <br/>Abstract: Two Multi-Layer Perceptron (MLP) models are developed to estimate the radar reflectivity factor (dBZ) and rain intensity (R) from the spectral moments of an L-band wind profiler. Out of the four spectral moment inputs of the MLP models, the backscattered power (P) and Doppler velocity (VD) were found to have better correlation with the rain parameters. The model results were validated with the Joss Waldvogel Disdrometer (JWD) observations. For the training and validation data sets of dBZ, the root mean square error (rmse) of estimated and observed data sets were found to be 5.05 and 5.32 dBZ with correlation coefficients of 0.90 and 0.86, respectively. Similarly, for the training and validation data sets of R, the rmse for estimated and observed values were found to be 4.27 and 7.74 mmh⁻¹ respectively with correlation coefficients of 0.95 and 0.78. The developed models were validated with a rain event on 22 June 2000, that consisted of rain from both convective and stratiform regimes. The error between the estimated and observed rain accumulation was found to be ~ 5%. The height profiles of estimated dBZ were able to identify the bright band during stratiform rain by virtue of high values of reflectivity gradient at around 4.0 km height. Though ambiguity in the estimation of R was observed at bright band level, overall estimated parameters were in good agreement with general characteristics of convective and stratiform rain. <br/> <br/>Page(s): 341-352