Correlation analysis of lidar derived optical parameters for investigations on thin cirrus features at a tropical station Gadanki(13.5ºN and 79.2ºE), India

The optical characterization of thin cirrus clouds is very important to understand its radiative effects. The optical parameters of cirrus clouds namely extinction

Macro-physical, optical and radiative properties of tropical cirrus clouds and its temperature dependence at Gadanki (13.5° N, 79.2° E) observed by ground based lidar

The macro-physical and optical properties of cirrus clouds and its temperature dependencies have been investigated at the National Atmospheric Research Laboratory (NARL; 13.5° N, 79.2° E), Gadanki, Andhra Pradesh, India; an inland tropical station during the period of observation January to December 2009 using a ground based pulsed monostatic lidar system data and radiosonde measurements. Based on the analysis of measurements the cirrus macrophysical properties such as occurrence height, mid cloud temperature, cloud geometrical thickness, and optical properties such as extinction coefficient, optical depth, depolarization ratio and lidar ratio have been determined. The variation of cirrus macrophysical and optical properties with mid cloud temperature have also been studied. The cirrus clouds mean height has been generally observed in the range of 9-17 km with a peak occurrence at 13-14 km. The cirrus mid cloud temperatures were in the range from -81 °C to -46 °C. The cirrus geometrical thickness ranges from 0.9-4.5 km and 56% of cirrus occurrences have thickness 1.0 -2.7 km. The monthly cirrus optical depth ranges from 0.01-0.47, but most (>80%) of the cirrus have values less than 0.1. The monthly mean cirrus extinction ranges from 2.8E-06 to 8E-05 and depolarization ratio and lidar ratio varies from 0.13 to 0.77 and 2 to 52 respectively. The temperature and thickness dependencies on cirrus optical properties have also been studied. A maximum cirrus geometrical thickness of 4.5 km is found at temperatures around – 46 °C with an indication that optical depth increases with increasing thickness and mid cloud temperature. The cloud radiative properties such as outgoing long-wave radiation (OLR) flux and cirrus IR forcing are studied. OLR flux during the cirrus occurrence days ranged from 348-456 W/m2 with a low value in the monsoon period. The cirrus IR forcing varied from 3.13 – 110.54 W/m2 and shows a peak at monsoon period

Optical properties of cirrus clouds in the tropical tropopause region during two contrasting seasons

155-166<span style="font-size:11.0pt;font-family: " times="" new="" roman","serif";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" mangal;mso-ansi-language:en-gb;mso-fareast-language:en-us;mso-bidi-language:="" hi"="" lang="EN-GB">Radiation budget of Earth’s atmospheric system is largely impacted by the presence of cirrus clouds. In order to quantify the effect of cirrus clouds, particularly in tropics, it is important to characterise its vertical structure and optical properties. The variation of the optical and microphysical properties along with the structure and dynamics of the cirrus during two contrasting seasons, the summer and the southwest monsoon over the period 2006 - 2010 were studied using the ground-based lidar measurements made at the tropical station, Gadanki (13.5°N, 79.2°E), India. The related meteorological indicators derived from radiosonde data available with Wyoming Atmospheric Data Centre were analysed .The results were compared with the data obtained from the CALIOP on board the CALIPSO satellite. Both the observations show similar pattern of seasonal variation. In most of the cirrus clouds, the top height observed was 0.8 km above and below the tropopause and top height was maximum during monsoon season. The seasonal variation of optical depth showed that most of cirrus clouds were thin and the optical depth showed highest value during monsoon period.</span

Optical Properties of Cirrus Clouds in the Tropical Tropopause Region during two Contrasting Seasons

Radiation budget of Earth’s atmospheric system is largely impacted by the presence of cirrus clouds. In order to quantify the effect of cirrus clouds, it is important to characterise their vertical structure and optical properties. The variation of the optical and microphysical properties along with the structure and dynamics of the cirrus during two contrasting seasons, the summer and the south west monsoon were studied using ground based lidar measurements made at the tropical station, Gadanki (13.50 N, 79.20 E), India. The related meteorological indicators derived from radiosonde data available with Wyoming atmospheric data centre are analysed .The results are compared with the data obtained from CALIOP on board the CALIPSO satellite. Both the observations follow similar pattern of variation. Most of the cirrus clouds top heights are observed 0.8 km above and below the tropopause and have the maximum top height during monsoon seasons. The seasonal variation of optical depth shows that most of cirrus clouds observed was thin clouds and the optical depth shows highest value during monsoon period

Lidar investigations on the optical and dynamical properties of cirrus clouds in the upper troposphere and lower stratosphere regions at a tropical station, Gadanki, India (13.5 degrees N, 79.2 degrees E)

High altitude cirrus clouds are composed mainly of ice crystals with a variety of sizes and shapes. They have a large influence on Earth's energy balance and global climate. Recent studies indicate that the formation, dissipation, life time, optical, and micro-physical properties are influenced by the dynamical conditions of the surrounding atmosphere like background aerosol, turbulence, etc. In this work, an attempt has been made to quantify some of these characteristics by using lidar and mesosphere-stratosphere-troposphere (MST) radar. Mie lidar and 53 MHz MST radar measurements made over 41 nights during the period 2009 to 2010 from the tropical station, Gadanki, India (13.5 degrees N, 79.2 degrees E). The optical and microphysical properties along with the structure and dynamics of the cirrus are presented as observed under different atmospheric conditions. The study reveals the manifestation of different forms of cirrus with a preferred altitude of formation in the 13 to 14 km altitude. There are considerable differences in the properties obtained among 2009 and 2010 showing significant anomalous behavior in 2010. The clouds observed during 2010 show relatively high asymmetry and large multiple scattering effects. The anomalies found during 2010 may be attributed to the turbulence noticed in the surrounding atmosphere. The results show a clear correlation between the crystal morphology in the clouds and the dynamical conditions of the prevailing atmosphere during the observational period. (c) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE

The role of crystallinity of the Nb₂O₅blocking layer on the performance of dye-sensitized solar cells

The prevention of back electron transfer by inserting an energy barrier layer at the interface of a photo-anode is an effective method for improving the photovoltaic parameters in dye sensitised solar cells (DSSCs). In this study, phase a modified Nb2O5 blocking layer was inserted at the fluorine doped tin oxide (FTO)/TiO2 interface via a Rf magnetron sputtering process. For a critical tunnelling distance of -40 nm, the crystalline Nb2O5 blocking layer improved the efficiency close to 7% and outperformed the amorphous blocking layer by about 68%. The longer electron lifetime observed in DSSCs containing an inhomogeneous Nb2O5 layer indicates that trapping/de-trapping impedes the discharge of electrons to the TiO2 band edge. The origin of the longer electron lifetime is explained by formulating a theory from photovoltage decay measurements