ISRN Atmospheric Sciences The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Rain Height Statistics Based on 0°C Isotherm Height Using TRMM Precipitation Data for Earth-Space Satellite Links in Nigeria Sun, 23 Mar 2014 13:42:54 +0000 In the prediction of attenuation due to precipitation related phenomena, the 0°C isotherm height plays a vital role. In this paper, 2 years of precipitation data obtained from the Tropical Rain Measuring Mission (TRMM) satellite had been analyzed to establish the distribution of rain height based on 0°C isotherm heights over six locations in Nigeria. Probability of exceedance of rain heights in each of the locations was compared between the two seasons in Nigeria. Rain heights distribution was also compared with the ITU-R P.839 recommendation. The overall results show seasonal, rainfall type’s dependence and overestimation of the rain height predicted by the ITU for Nigeria. Joseph Sunday Ojo Copyright © 2014 Joseph Sunday Ojo. All rights reserved. Evaluation of Regional Climatic Model Simulated Aerosol Optical Properties over South Africa Using Ground-Based and Satellite Observations Sun, 10 Nov 2013 11:26:09 +0000 The present study evaluates the aerosol optical property computing performance of the Regional Climate Model (RegCM4) which is interactively coupled with anthropogenic-desert dust schemes, in South Africa. The validation was carried out by comparing RegCM4 estimated: aerosol extinction coefficient profile, Aerosol Optical Depth (AOD), and Single Scattering Albedo (SSA) with AERONET, LIDAR, and MISR observations. The results showed that the magnitudes of simulated AOD at the Skukuza station (24°S, 31°E) are within the standard deviation of AERONET and ±25% of MISR observations. Within the latitudinal range of 26.5°S to 24.5°S, simulated AOD and SSA values are within the standard deviation of MISR retrievals. However, within the latitude range of 33.5°S to 27°S, the model exhibited enhanced AOD and SSA values when compared with MISR observations. This is primarily associated with the dry bias in simulated precipitation that leads to the overestimation of dust emission and underestimation of aerosol wet deposition. With respect to LIDAR, the model performed well in capturing the major aerosol extinction profiles. Overall, the results showed that RegCM4 has a good ability in reproducing the major observational features of aerosol optical fields over the area of interest. M. Tesfaye, J. Botai, V. Sivakumar, and G. Mengistu Tsidu Copyright © 2013 M. Tesfaye et al. All rights reserved. Simulation of Water Vapor Condensation in a Partly Closed Structure: The Influence of the External Conditions of Temperature and Humidity Mon, 24 Jun 2013 13:56:24 +0000 Our aim is to determine the more significant parameters acting on the water vapor condensation in a partly closed structure, submitted to external constraints (temperature and humidity) which induce convective movements and thermal variations inside. These constraints locally lead to condensation of the water vapor, initially contained in the air of the volume and/or on the walls. The inside bottom wall is remained dry. Condensed water quantities depend on: (1) dimensions of the structure, (2) the air renewing and its hygrometry, and (3) the phase between thermal and hydrometric conditions. Peculiar conditions are needed to obtain a maximum of condensation. Jean Batina and René Peyrous Copyright © 2013 Jean Batina and René Peyrous. All rights reserved. Biological and Chemical Diversity of Biogenic Volatile Organic Emissions into the Atmosphere Tue, 18 Jun 2013 09:55:50 +0000 Biogenic volatile organic compounds (BVOC) emitted by terrestrial ecosystems into the atmosphere play an important role in determining atmospheric constituents including the oxidants and aerosols that control air quality and climate. Accurate quantitative estimates of BVOC emissions are needed to understand the processes controlling the earth system and to develop effective air quality and climate management strategies. The large uncertainties associated with BVOC emission estimates must be reduced, but this is challenging due to the large number of compounds and biological sources. The information on the immense biological and chemical diversity of BVOC is reviewed with a focus on observations that have been incorporated into the MEGAN2.1 BVOC emission model. Strategies for improving current BVOC emission modeling approaches by better representations of this diversity are presented. The current gaps in the available data for parameterizing emission models and the priorities for future measurements are discussed. Alex Guenther Copyright © 2013 Alex Guenther. All rights reserved. Volcanic Ash versus Mineral Dust: Atmospheric Processing and Environmental and Climate Impacts Wed, 12 Jun 2013 17:10:43 +0000 This review paper contrasts volcanic ash and mineral dust regarding their chemical and physical properties, sources, atmospheric load, deposition processes, atmospheric processing, and environmental and climate effects. Although there are substantial differences in the history of mineral dust and volcanic ash particles before they are released into the atmosphere, a number of similarities exist in atmospheric processing at ambient temperatures and environmental and climate impacts. By providing an overview on the differences and similarities between volcanic ash and mineral dust processes and effects, this review paper aims to appeal for future joint research strategies to extend our current knowledge through close cooperation between mineral dust and volcanic ash researchers. Baerbel Langmann Copyright © 2013 Baerbel Langmann. All rights reserved. Solitary Rossby Waves in the Lower Tropical Troposphere Sun, 02 Jun 2013 16:33:53 +0000 Weakly nonlinear approximation is used to study the theoretical comportment of large-scale disturbances around the intertropical midtropospheric jet. We show here that the Korteweg de Vries (KdV) theory is appropriated to describe the structure of the streamlines around the African easterly jet (AEJ) region. The introduction of the additional velocity of the soliton C1 permits to search the stage where the configuration of the wave structures is going to emerge out of specified initial conditions and this is the direct and inverse cascade method. It was also shown that the configurations of disturbances can be influenced by this parameter so that we can look if the disturbances are in the control or not of their dispersive effects. This permits to explain the evolution of initial conditions of the Tropical Storm (TS) Debby over West Africa from 20 to 24 August 2006. Andre Lenouo and Francois Kamga Nkankam Copyright © 2013 Andre Lenouo and Francois Kamga Nkankam. All rights reserved. Temporal Patterns of the Two-Dimensional Spatial Trends in Summer Temperature and Monsoon Precipitation of Bangladesh Thu, 28 Mar 2013 17:59:40 +0000 Two climate indices, TXx and PRCPTOT, representing the summer maximum temperature and annual total monsoon precipitation, respectively, in Bangladesh were computed. The temperature and precipitation measurements from 34 meteorological stations during the temporal extent of 1948–2007 were applied for indices’ computation under thorough quality control. The spatial trends of the indices were analyzed by applying two-dimensional least square approach along latitudes and longitudes of the observation points. The temporal patterns of the spatial trends were identified by temporally interpolating them applying thin plate smoothing spline method. The analyses of TXx identified regional scale spatial trends in the east-west and south-north directions, which were increasing between 1948 and 1980s. After the 1980s the spatial trends started decreasing, and after 2000 the spatial trend along the south-north changed its direction to the north-south and continued until present. The analyses of the PRCPTOT identified spatial trends in the west-east and north-south directions, which were decreasing between 1948 and 1980s and thereafter increasing until present. About half of the spatial trends were significant in F-statistics at or more than 90% confidence level. Thus, the obtained results indicated a significant climatic shift within the regional scale of the country during the study period. Avit Kumar Bhowmik Copyright © 2013 Avit Kumar Bhowmik. All rights reserved. The Diurnal Temperature Range for Europe: A Search for Cosmic Ray Forbush Decrease Manifestations and the DTR Periodicities Tue, 15 Jan 2013 08:56:39 +0000 Following on previous work by others, which gave evidence for few days’ changes in the European Diurnal Temperature Range (DTR) apparently correlated with Cosmic Ray Forbush Decreases, we have made an independent study. We find no positive evidence. An analysis has also been made of the Fourier components of the time series of the DTR value (taken as deviations from a ±10 day running mean). Evidence for a number of interesting periods is found, including one at about 27 days, albeit with a variability with time. The same period of solar irradiance (particularly in the UV) is favoured as the explanation. A. D. Erlykin and A. W. Wolfendale Copyright © 2013 A. D. Erlykin and A. W. Wolfendale. All rights reserved. An Exploration of Temperature Metrics for Further Developing the Heat-Health Weather Warning System in Hong Kong Mon, 14 Jan 2013 16:04:44 +0000 Background. The current weather warning system aims to reduce mortality from heat and cold stress but still has room to be improved in terms of incorporating other temperature metrics. The aim of this study is to determine how extreme temperature affects mortality in Hong Kong. Methods. An ecological study was used; daily weather data were subdivided into seven temperature metrics. Daily detrended mortality data were stratified by disease groups and analysed using seven different metrics for temperature. The temperature metrics were then compared. Results. A diurnal temperature range (DTR) of ≥8°C leading to an increase in median mortality of up to 16% and a mean temperature change between neighbouring days of ≥4°C leading to an increase in median mortality of up to 6% were the critical thresholds for excess mortality in Hong Kong. Conclusions. This study reveals that mean net effective temperature, DTR, and temperature change between neighbouring days are effective to predict excess mortality in Hong Kong. Cho Kwong Charlie Lam, Margaret Loughnan, and Nigel Tapper Copyright © 2013 Cho Kwong Charlie Lam et al. All rights reserved. Connecting Turbulence and Meandering Parameterization to Describe Passive Scalars Dispersion in Low Wind Speed Conditions Mon, 14 Jan 2013 13:23:24 +0000 The following study deals with meandering of the horizontal mean wind. The main motivation for such investigation came from the difficulty in describing contaminant dispersion in meandering conditions. Observational field measurements point out that the autocorrelation function of the horizontal wind components, obtained for the meandering cases, displays an oscillating behavior with the presence of large negative lobes. Such negative lobes are described by an equation containing functions that represent patterns of movement associated to meandering and turbulence. As a consequence, this mathematical formulation connects the turbulence and meandering phenomenon establishing the employment of hybrid parameters in models that describe the meandering dispersion. Therefore, considering this dualistic aspect between meandering and turbulence manifestations, a new set of relations for the turbulence parameterization joined with the meandering of the wind have been developed and are available. This new turbulence parameterization for a stable shear forcing planetary boundary layer, united with a meandering mean time scale is able to describe contaminant meandering enhanced spread in a low wind speed stable planetary boundary layer. V. S. Moreira, G. Degrazia, A. U. Timm, D. R. Roberti, and S. Maldaner Copyright © 2013 V. S. Moreira et al. All rights reserved.