Atmosphere

5279 KiB

Open AccessArticle

Characterization of the Interannual Variability of Precipitation and Streamflow in Tensift and Ksob Basins (Morocco) and Links with the NAO

by Zineb Zamrane, Imen Turki, Benoit Laignel, Gil Mahé and Nour-Eddine Laftouhi

Atmosphere 2016, 7(6), 84; https://doi.org/10.3390/atmos7060084 - 17 Jun 2016

Cited by 23 | Viewed by 6018

Abstract

The aim of this study is to understand the inter-annual hydrological variability (precipitation and streamflow) in the basins of the High Atlas in Morocco and to determine how climate fluctuations (represented by the North Atlantic Oscillation (NAO) climate index) are expressed in the [...] Read more.

The aim of this study is to understand the inter-annual hydrological variability (precipitation and streamflow) in the basins of the High Atlas in Morocco and to determine how climate fluctuations (represented by the North Atlantic Oscillation (NAO) climate index) are expressed in the hydrological system. To reach this objective, time series of precipitation and streamflow are processed as standardized anomalies and studied by continuous wavelet analysis and wavelet coherence analysis, which are particularly suitable for the study of unsteady processes. Wet and dry periods vary from one basin to another between three and five years. The wavelet analysis shows the existence of many bands of energy in most of the sub-basins, from annual to inter-annual scales regarding the precipitation and streamflow time series. These bands correspond to intervals of one year, 2–4 years, 4–8 years and 8–12 years. The wavelet coherence analysis shows a strong coherence between NAO/streamflow and precipitation/NAO identified at the inter-annual scale. Non-stationarity can be observed in the late 1980s, 1990s and 2000s. The contribution of the NAO is different from one basin to another ranging between 67% and 77%. Full article

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4746 KiB

Open AccessArticle

Detection of Ground Clutter from Weather Radar Using a Dual-Polarization and Dual-Scan Method

by Mohammad-Hossein Golbon-Haghighi, Guifu Zhang, Yinguang Li and Richard J. Doviak

Atmosphere 2016, 7(6), 83; https://doi.org/10.3390/atmos7060083 - 15 Jun 2016

Cited by 19 | Viewed by 9343

Abstract

A novel dual-polarization and dual-scan (DPDS) classification algorithm is developed for clutter detection in weather radar observations. Two consecutive scans of dual-polarization radar echoes are jointly processed to estimate auto- and cross-correlation functions. Discriminants are then defined and estimated in order to separate [...] Read more.

A novel dual-polarization and dual-scan (DPDS) classification algorithm is developed for clutter detection in weather radar observations. Two consecutive scans of dual-polarization radar echoes are jointly processed to estimate auto- and cross-correlation functions. Discriminants are then defined and estimated in order to separate clutter from weather based on their physical and statistical properties. An optimal Bayesian classifier is used to make a decision on clutter presence from the estimated discriminant functions. The DPDS algorithm is applied to the data collected with the KOUN polarimetric radar and compared with the existing detection methods. It is shown that the DPDS algorithm yields a higher probability of detection and lower false alarm rate in clutter detection. Full article

(This article belongs to the Special Issue Radar Meteorology)

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3770 KiB

Open AccessArticle

Validation of ERA-Interim Precipitation Estimates over the Baltic Sea

by Karl Bumke

Atmosphere 2016, 7(6), 82; https://doi.org/10.3390/atmos7060082 - 11 Jun 2016

Cited by 8 | Viewed by 5314

Abstract

European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim reanalysis total precipitation estimates are validated against ten years of in situ precipitation measurements onboard of ships over the Baltic Sea. A statistical analysis for binary forecasts and mean rain rates derived from all data [...] Read more.

European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim reanalysis total precipitation estimates are validated against ten years of in situ precipitation measurements onboard of ships over the Baltic Sea. A statistical analysis for binary forecasts and mean rain rates derived from all data show a good agreement with observations. However, a closer look reveals an underestimation of ERA-Interim total precipitation in spring and an overestimation in autumn, obviously related to stability. Deriving stability and evaporation by a bulk flux scheme it could be shown, in fact, that ERA-Interim underestimates precipitation for conditions with low evaporation and strongly overestimates it for conditions with high evaporation. Since ERA-Interim surface fields become too dry with increasing evaporation compared to independent synoptic ship observations, uncertainties in the ECMWF convection scheme may possibly cause these biases in seasonal precipitation. Full article

(This article belongs to the Special Issue Advances in Clouds and Precipitation)

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39314 KiB

Open AccessArticle

Accurate Characterization of Winter Precipitation Using Multi-Angle Snowflake Camera, Visual Hull, Advanced Scattering Methods and Polarimetric Radar

by Branislav M. Notaroš, Viswanathan N. Bringi, Cameron Kleinkort, Patrick Kennedy, Gwo-Jong Huang, Merhala Thurai, Andrew J. Newman, Wonbae Bang and GyuWon Lee

Atmosphere 2016, 7(6), 81; https://doi.org/10.3390/atmos7060081 - 11 Jun 2016

Cited by 29 | Viewed by 7217

Abstract

This article proposes and presents a novel approach to the characterization of winter precipitation and modeling of radar observables through a synergistic use of advanced optical disdrometers for microphysical and geometrical measurements of ice and snow particles (in particular, a multi-angle snowflake camera—MASC), [...] Read more.

This article proposes and presents a novel approach to the characterization of winter precipitation and modeling of radar observables through a synergistic use of advanced optical disdrometers for microphysical and geometrical measurements of ice and snow particles (in particular, a multi-angle snowflake camera—MASC), image processing methodology, advanced method-of-moments scattering computations, and state-of-the-art polarimetric radars. The article also describes the newly built and established MASCRAD (MASC + Radar) in-situ measurement site, under the umbrella of CSU-CHILL Radar, as well as the MASCRAD project and 2014/2015 winter campaign. We apply a visual hull method to reconstruct 3D shapes of ice particles based on high-resolution MASC images, and perform “particle-by-particle” scattering computations to obtain polarimetric radar observables. The article also presents and discusses selected illustrative observation data, results, and analyses for three cases with widely-differing meteorological settings that involve contrasting hydrometeor forms. Illustrative results of scattering calculations based on MASC images captured during these events, in comparison with radar data, as well as selected comparative studies of snow habits from MASC, 2D video-disdrometer, and CHILL radar data, are presented, along with the analysis of microphysical characteristics of particles. In the longer term, this work has potential to significantly improve the radar-based quantitative winter-precipitation estimation. Full article

(This article belongs to the Special Issue Advances in Clouds and Precipitation)

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1435 KiB

Open AccessArticle

An Inter-Comparison of the Holiday Climate Index (HCI) and the Tourism Climate Index (TCI) in Europe

by Daniel Scott, Michelle Rutty, Bas Amelung and Mantao Tang

Atmosphere 2016, 7(6), 80; https://doi.org/10.3390/atmos7060080 - 07 Jun 2016

Cited by 116 | Viewed by 13692

Abstract

Much research has been devoted to quantifying optimal or unacceptable climate conditions both generally and for specific tourism segments or activities over the last 10 years. This knowledge is not incorporated in the Tourism Climate Index (TCI), which has also been subject to [...] Read more.

Much research has been devoted to quantifying optimal or unacceptable climate conditions both generally and for specific tourism segments or activities over the last 10 years. This knowledge is not incorporated in the Tourism Climate Index (TCI), which has also been subject to other substantial critiques. To more accurately assess the climatic suitability of destinations for leisure tourism, the Holiday Climate Index (HCI) was developed. A major advancement of the HCI is that its variable rating scales and the component weighting system are based on this aforementioned literature of tourists’ stated climatic preferences. This paper will discuss the design of the HCI and how the limitations of the TCI were overcome. It then presents an inter-comparison of the results from HCI:Urban and TCI for geographically diverse urban destinations across Europe. The results illustrate how the HCI:Urban rates the climate of many cities higher than the TCI, particularly in shoulder seasons and the winter months, which is more consistent with observed visitation patterns. The results empirically demonstrate that use of the TCI should be discontinued. Full article

(This article belongs to the Special Issue Tourism Climatology)

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2974 KiB

Open AccessArticle

A Commercial Aircraft Fuel Burn and Emissions Inventory for 2005–2011

by Donata K. Wasiuk, Md Anwar H. Khan, Dudley E. Shallcross and Mark H. Lowenberg

Atmosphere 2016, 7(6), 78; https://doi.org/10.3390/atmos7060078 - 04 Jun 2016

Cited by 24 | Viewed by 5535

Abstract

The commercial aircraft fuel burn and emission estimates of CO₂, CO, H₂O, hydrocarbons, NO_x and SO_x for 2005–2011 are given as the 4-D Aircraft Fuel Burn and Emissions Inventory. On average, the annual fuel burn and emissions [...] Read more.

The commercial aircraft fuel burn and emission estimates of CO₂, CO, H₂O, hydrocarbons, NO_x and SO_x for 2005–2011 are given as the 4-D Aircraft Fuel Burn and Emissions Inventory. On average, the annual fuel burn and emissions of CO₂, H₂O, NO_x, and SO_x increased by 2%–3% for 2005–2011, however, annual CO and HC emissions decreased by 1.6% and 8.7%, respectively because of improving combustion efficiency in recent aircraft. Approximately 90% of the global annual aircraft NO_x emissions were emitted in the NH between 2005 and 2011. Air traffic within the three main industrialised regions of the NH (Asia, Europe, and North America) alone accounted for 80% of the global number of departures, resulting in 50% and 45% of the global aircraft CO₂ and NO_x emissions, respectively, during 2005–2011. The current Asian fleet appears to impact our climate strongly (in terms of CO₂ and NO_x) when compared with the European and North American fleet. The changes in the geographical distribution and a gradual shift of the global aircraft NO_x emissions as well as a subtle but steady change in regional emissions trends are shown in particular comparatively rising growth rates between 0 and 30°N and decreasing levels between 30 and 60°N. Full article

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2900 KiB

Open AccessArticle

Detailed Source-Specific Molecular Composition of Ambient Aerosol Organic Matter Using Ultrahigh Resolution Mass Spectrometry and ¹H NMR

by Amanda S. Willoughby, Andrew S. Wozniak and Patrick G. Hatcher

Atmosphere 2016, 7(6), 79; https://doi.org/10.3390/atmos7060079 - 03 Jun 2016

Cited by 33 | Viewed by 6905

Abstract

Organic aerosols (OA) are universally regarded as an important component of the atmosphere that have far-ranging impacts on climate forcing and human health. Many of these impacts are related to OA molecular characteristics. Despite the acknowledged importance, current uncertainties related to the source [...] Read more.

Organic aerosols (OA) are universally regarded as an important component of the atmosphere that have far-ranging impacts on climate forcing and human health. Many of these impacts are related to OA molecular characteristics. Despite the acknowledged importance, current uncertainties related to the source apportionment of molecular properties and environmental impacts make it difficult to confidently predict the net impacts of OA. Here we evaluate the specific molecular compounds as well as bulk structural properties of total suspended particulates in ambient OA collected from key emission sources (marine, biomass burning, and urban) using ultrahigh resolution mass spectrometry (UHR-MS) and proton nuclear magnetic resonance spectroscopy (¹H NMR). UHR-MS and ¹H NMR show that OA within each source is structurally diverse, and the molecular characteristics are described in detail. Principal component analysis (PCA) revealed that (1) aromatic nitrogen species are distinguishing components for these biomass burning aerosols; (2) these urban aerosols are distinguished by having formulas with high O/C ratios and lesser aromatic and condensed aromatic formulas; and (3) these marine aerosols are distinguished by lipid-like compounds of likely marine biological origin. This study provides a unique qualitative approach for enhancing the chemical characterization of OA necessary for molecular source apportionment. Full article

(This article belongs to the Special Issue Air Quality and Source Apportionment)

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3192 KiB

Open AccessArticle

The Spatial Variation of Dust Particulate Matter Concentrations during Two Icelandic Dust Storms in 2015

by Pavla Dagsson-Waldhauserova, Agnes Ösp Magnusdottir, Haraldur Olafsson and Olafur Arnalds

Atmosphere 2016, 7(6), 77; https://doi.org/10.3390/atmos7060077 - 03 Jun 2016

Cited by 20 | Viewed by 5132

Abstract

Particulate matter mass concentrations and size fractions of PM₁, PM_2.5, PM₄, PM₁₀, and PM₁₅ measured in transversal horizontal profile of two dust storms in southwestern Iceland are presented. Images from a camera network were [...] Read more.

Particulate matter mass concentrations and size fractions of PM₁, PM_2.5, PM₄, PM₁₀, and PM₁₅ measured in transversal horizontal profile of two dust storms in southwestern Iceland are presented. Images from a camera network were used to estimate the visibility and spatial extent of measured dust events. Numerical simulations were used to calculate the total dust flux from the sources as 180,000 and 280,000 tons for each storm. The mean PM₁₅ concentrations inside of the dust plumes varied from 10 to 1600 µg·m⁻³ (PM₁₀ = 7 to 583 µg·m⁻³). The mean PM₁ concentrations were 97–241 µg·m⁻³ with a maximum of 261 µg·m⁻³ for the first storm. The PM₁/PM_2.5 ratios of >0.9 and PM₁/PM₁₀ ratios of 0.34–0.63 show that suspension of volcanic materials in Iceland causes air pollution with extremely high PM₁ concentrations, similar to polluted urban areas in Europe or Asia. Icelandic volcanic dust consists of a higher proportion of submicron particles compared to crustal dust. Both dust storms occurred in relatively densely inhabited areas of Iceland. First results on size partitioning of Icelandic dust presented here should challenge health authorities to enhance research in relation to dust and shows the need for public dust warning systems. Full article

(This article belongs to the Special Issue Air Quality and Source Apportionment)

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218 KiB

Open AccessTechnical Note

Calibration Accuracy of the Dual-Polarization Receivers of the C-Band Swiss Weather Radar Network

by Marco Gabella, Marco Boscacci, Maurizio Sartori and Urs Germann

Atmosphere 2016, 7(6), 76; https://doi.org/10.3390/atmos7060076 - 31 May 2016

Cited by 11 | Viewed by 4722

Abstract

The electromagnetic power that comes from the Sun has been proved to be an effective reference for checking the quality of dual-polarization weather radar receiver. Operational monitoring methods have been developed and implemented for determining the electromagnetic antenna pointing, assessing the receiver stability, [...] Read more.

The electromagnetic power that comes from the Sun has been proved to be an effective reference for checking the quality of dual-polarization weather radar receiver. Operational monitoring methods have been developed and implemented for determining the electromagnetic antenna pointing, assessing the receiver stability, and the differential reflectivity offset. So far, the focus has been on relative calibration: horizontal and vertical polarization have been mutually compared and evaluated versus the reference mainly in terms of standard deviation of the error. Radar receivers have been able to capture and describe the monthly variability (slowly varying component) of the microwave signal emitted by the Sun. In this paper, we present results from a novel Sun-based method aiming at the absolute calibration of dual-polarization weather radar receivers. To obtain best results, the radar receiver has to be off-line for a few minutes during the tracking of the Sun in order to have the antenna beam axis pointing at the center of the Sun. Among the five polarimetric weather radar receivers of the Swiss network, radar “WEI” located at an altitude of 2850 m next to Davos shows the best absolute agreement with the Dominion Radio Astrophysical Observatory (DRAO) reference for both horizontal (H) and vertical (V) polarization. Albis radar, which is located at an altitude of 938 m near Zurich, shows the largest difference: the radar receiver is too low compared to the Sun reference by −1.62 (−1.25) dB for the H (V) channel. Interestingly, the standard deviation of the error is smaller than ±0.17 dB for all Swiss radar receivers. With a standard deviation of ±0.04 dB Albis radar shows the best relative agreement between H and V. These results are encouraging and MeteoSwiss is planning to repeat off-line Sun-tracking measurements in the future on a regular basis. Full article

(This article belongs to the Special Issue Radar Meteorology)

620 KiB

Open AccessArticle

Stratospheric Aerosols from Major Volcanic Eruptions: A Composition-Climate Model Study of the Aerosol Cloud Dispersal and e-folding Time

by Giovanni Pitari, Glauco Di Genova, Eva Mancini, Daniele Visioni, Ilaria Gandolfi and Irene Cionni

Atmosphere 2016, 7(6), 75; https://doi.org/10.3390/atmos7060075 - 26 May 2016

Cited by 36 | Viewed by 10431

Abstract

Large explosive volcanic eruptions are capable of injecting considerable amounts of particles and sulfur gases above the tropopause, causing large increases in stratospheric aerosols. Five major volcanic eruptions after 1960 (i.e., Agung, St. Helens, El Chichón, Nevado del Ruiz and Pinatubo) [...] Read more.

Large explosive volcanic eruptions are capable of injecting considerable amounts of particles and sulfur gases above the tropopause, causing large increases in stratospheric aerosols. Five major volcanic eruptions after 1960 (i.e., Agung, St. Helens, El Chichón, Nevado del Ruiz and Pinatubo) have been considered in a numerical study conducted with a composition-climate coupled model including an aerosol microphysics code for aerosol formation and growth. Model results are compared between an ensemble of numerical simulations including volcanic aerosols and their radiative effects (VE) and a reference simulations ensemble (REF) with no radiative impact of the volcanic aerosols. Differences of VE-REF show enhanced diabatic heating rates; increased stratospheric temperatures and mean zonal westerly winds; increased planetary wave amplitude; and tropical upwelling. The impact on stratospheric upwelling is found to be larger when the volcanically perturbed stratospheric aerosol is confined to the tropics, as tends to be the case for eruptions which were followed by several months with easterly shear of the quasi-biennial oscillation (QBO), e.g., the Pinatubo case. Compared to an eruption followed by a period of westerly QBO, such easterly QBO eruptions are quite different, with meridional transport to mid- and high-latitudes occurring later, and at higher altitude, with a consequent decrease in cross-tropopause removal from the stratosphere, and therefore longer decay timescale. Comparing the model-calculated e-folding time of the volcanic aerosol mass during the first year after the eruptions, an increase is found from 8.1 and 10.3 months for El Chichón and Agung (QBO westerly shear), to 14.6 and 30.7 months for Pinatubo and Ruiz (QBO easterly shear). The corresponding e-folding time of the global-mean radiative flux changes goes from 9.1 and 8.0 months for El Chichón and Agung, to 28.7 and 24.5 months for Pinatubo and Ruiz. Full article

(This article belongs to the Special Issue Atmospheric Aerosols and Their Radiative Effects)

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4580 KiB

Open AccessArticle

Indirect Prediction of Welding Fume Diffusion inside a Room Using Computational Fluid Dynamics

by Sujit Dahal, Taehyeung Kim and Kwangseog Ahn

Atmosphere 2016, 7(6), 74; https://doi.org/10.3390/atmos7060074 - 25 May 2016

Cited by 8 | Viewed by 5620

Abstract

Welding is an important and widely used process in the manufacturing and maintenance of various works involving metals and alloys. While welding has broad applications, the welding fume generated during the process has impacts on workers’ health, which needs to be addressed. One [...] Read more.

Welding is an important and widely used process in the manufacturing and maintenance of various works involving metals and alloys. While welding has broad applications, the welding fume generated during the process has impacts on workers’ health, which needs to be addressed. One of the major steps that can be undertaken to take care of this issue is the use of ventilation, which requires knowledge of characteristics and dispersion of the welding fume in the workers’ breathing zone. It is difficult to assess welding fume dispersion from manual measurement due to numerous welding processes and sufficient data requirement. Numerical prediction of welding fume is dubious due to several errors. This paper considers the use of numerically predicted CO₂ concentrations to indirectly predict welding fume distribution in workshops. This is based on the assumption that if the particles are sufficiently small size, they follow the diffusion pattern of gases. Experiments are carried out in a room with an opening and a welding fume generation system for measurement of CO₂ and fume diffusion. The results show high possibility of predicting welding fume concentration based on Computational Fluid Dynamics (CFD) simulated CO₂ concentration with a correlation coefficient of 0.74. Full article

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Atmosphere, Volume 7, Issue 6 (June 2016) – 11 articles

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