Atmospheric conditions producing aircraft icing on 24-25 January 1989 - A case study utilizing combinations of surface and remote sensors

1990 ◽  
Author(s):  
B. STANKOV ◽  
A. BEDARD, JR.
Keyword(s):  
Atmospheric Conditions ◽  
Aircraft Icing ◽  
Remote Sensors

scholarly journals Growth of nucleation mode particles in the summertime Arctic: a case study

2016 ◽  
Vol 16 (12) ◽  
pp. 7663-7679 ◽  
Author(s):  
Megan D. Willis ◽  
Julia Burkart ◽  
Jennie L. Thomas ◽  
Franziska Köllner ◽  
Johannes Schneider ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Methanesulfonic Acid ◽  
Lower Troposphere ◽  
Atmospheric Conditions ◽  
Aerosol Formation ◽  
Radiative Balance ◽  
Nucleation Mode ◽  
Cloud Properties ◽  
Marine Influence

Abstract. The summertime Arctic lower troposphere is a relatively pristine background aerosol environment dominated by nucleation and Aitken mode particles. Understanding the mechanisms that control the formation and growth of aerosol is crucial for our ability to predict cloud properties and therefore radiative balance and climate. We present an analysis of an aerosol growth event observed in the Canadian Arctic Archipelago during summer as part of the NETCARE project. Under stable and clean atmospheric conditions, with low inversion heights, carbon monoxide less than 80 ppbv, and black carbon less than 5 ng m−3, we observe growth of small particles,  <  20 nm in diameter, into sizes above 50 nm. Aerosol growth was correlated with the presence of organic species, trimethylamine, and methanesulfonic acid (MSA) in particles ∼ 80 nm and larger, where the organics are similar to those previously observed in marine settings. MSA-to-sulfate ratios as high as 0.15 were observed during aerosol growth, suggesting an important marine influence. The organic-rich aerosol contributes significantly to particles active as cloud condensation nuclei (CCN, supersaturation  =  0.6 %), which are elevated in concentration during aerosol growth above background levels of ∼ 100 to ∼ 220 cm−3. Results from this case study highlight the potential importance of secondary organic aerosol formation and its role in growing nucleation mode aerosol into CCN-active sizes in this remote marine environment.

scholarly journals Variation of diurnal Turbulence Kinetic Energy using sonic anemometer observation: a case study Ledeng, Bandung

2018 ◽  
Author(s):  
Sandy Hardian Susanto Herho ◽  
Dasapta Erwin Irawan
Keyword(s):  
Kinetic Energy ◽  
Diurnal Variation ◽  
Wind Velocity ◽  
Sonic Anemometer ◽  
Diurnal Variations ◽  
Turbulence Kinetic Energy ◽  
Atmospheric Conditions

Sonic anemometer observation was performed on 29 - 30 September 2014 in Ledeng, Bandung to see diurnal variations of Turbulence Kinetic Energy (TKE) that occurred in this area. The measured sonic anemometer was the wind velocity components u, v, and w. From the observation result, it can be seen that the diurnal variation that happened was quite significant. The maximum TKE occurs during the daytime when atmospheric conditions tend to be unstable. TKE values were small at night when atmospheric conditions are more stable than during the daytime.

An Investigation of Microwave Link Degradation due to Atmospheric Conditions (A Case Study of Akure-Owo Digital Microwave Link)

2009 ◽  
Vol 62-64 ◽  
pp. 159-165 ◽  
Author(s):  
P.O. Otasowie ◽  
F.O. Edeko
Keyword(s):  
Bit Error Rate ◽  
Error Rate ◽  
Error Rates ◽  
Atmospheric Conditions ◽  
Bit Error Rates ◽  
Data Acquisition Software ◽  
Model Equations ◽  
June July ◽  
Microwave Link

This work investigates the microwave link degradation due to atmospheric conditions on the Akure-Owo Digital Microwave Link. Microwave line of sight measurements were carried out between January and December 2005 with a data acquisition software (PROCOMM PLUS SOFTWARE). The data collected were analyzed using MATLAB 7.0 SOFTWARE program to determine the months of the year that has the highest degradation due to atmospheric conditions and also the months of the year that has the highest bit error rates. The result showed that the months of January, June, July, August and September have the worst signal degradation of -0.97dbm, -2.0dbm, -3.97dbm, -3.97dbm, -1.97dbm. respectively. The result also showed that the bit error rates are good and acceptable throughout the months of the year. A model equation was developed to predict the signal strength received and the bit error rate in the microwave link investigated, when atmospheric conditions are taken into consideration. The results of the predicted model were validated by field data and the results obtained showed an error of -0.2% for the received signal level and zero error for the bit error rate which means that the developed model equations can be used to accurately predict the link degradation parameters.

Relationship between meningitis occurrence and atmospheric conditions over the African meningitis belt

2020 ◽  
Author(s):  
Cheikh Dione ◽  
Mame Diarra Diouf ◽  
Bob Alex Ogwang ◽  
Elijah Adesanya Adefisan ◽  
Steve Woolnough ◽  
...  
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Lassa Fever ◽  
Atmospheric Conditions ◽  
Numerical Weather ◽  
Endemic Diseases ◽  
Meningitis Belt ◽  
Weather And Climate

&lt;p&gt; The alternation of seasons over tropical northern Africa is associated with the occurrence of devastating diseases such as meningitis, Lassa fever and malaria. These tropical diseases are associated with specific atmospheric conditions. Thus, meningitis is one of the most endemic diseases observed over this region with a prevalence period up to 7 months (December-June). Previous studies based on the link between atmospheric conditions and the occurrence of meningitis outbreaks have shown that this disease develops under dry and dusty atmospheric conditions which are difficult to represent in numerical weather and climate models. However, the onset, breakup, and sub-seasonal variability of meningitis outbreaks are not well documented. The objective of this study is to identify the local and synoptic drivers favoring the large occurrence of this disease over the meningitis belt in order to improve its predictability by numerical weather and climate models on intra-seasonal and seasonal timescales. This study focuses on two cases studies of meningitis epidemics over Niger in 2009 and 2015. The case study of 2009 started early with a duration of more than eight weeks. The second case study was shorter than the first one. It took three weeks and was observed at the end of the dry season. Based on ERA5 data, surface dust concentration observations and satellite data, a further analysis of the role of climate metrics on the triggering of meningitis epidemics on intra-seasonal timescales at local and large scale atmospheric conditions will be presented.&lt;/p&gt;

Seasonal, Regional, and Storm-Scale Variability of Cloud-to-Ground Lightning Characteristics in Florida

2011 ◽  
Vol 139 (6) ◽  
pp. 1826-1843 ◽  
Author(s):  
Scott D. Rudlosky ◽  
Henry E. Fuelberg
Keyword(s):  
Structural Damage ◽  
Warm Season ◽  
Atmospheric Conditions ◽  
Cool Season ◽  
Peak Current ◽  
Close Proximity ◽  
Cloud To Ground Lightning ◽  
Large Peak ◽  
Reversed Polarity

Abstract Seasonal, regional, and storm-scale variations of cloud-to-ground (CG) lightning characteristics in Florida are presented. Strong positive CG (+CG) and negative CG (−CG) flashes (i.e., having large peak current) are emphasized since they often are associated with strong storms, structural damage, and wildfire ignitions. Although strong −CG flashes are most common during the warm season (May–September) over the peninsula, the greatest proportion of strong +CG flashes occurs during the cool season (October–April) over the panhandle. The warm season exhibits the smallest +CG percentage but contains the greatest +CG flash densities, due in part to more ambiguous +CG reports (15–20 kA). The more frequent occurrence of ambiguous +CG reports helps explain the unusually small average +CG peak current during the warm season, whereas strong +CG reports (&gt;20 kA) appear to be responsible for the greater average warm season +CG multiplicity. The −CG flash density, multiplicity, and peak current appear to be directly related, exhibiting their greatest values during the warm season when deep storms are most common. A case study examines the atmospheric conditions and storm-scale processes associated with two distinct groups of storms on 13–14 May 2007. Although these groups of storms form in close proximity, several factors combine to produce predominately strong +CG and −CG flashes in the northern (south Georgia) and southern (north Florida) regions, respectively. Results suggest that heat and smoke very near preexisting wildfires are key ingredients in producing reversed-polarity (+CG dominated) storms that often ignite subsequent wildfires.

The Nighttime Pedestrian Collision: Human Factors Issues and a Case Study

2001 ◽  
Vol 45 (11) ◽  
pp. 833-837 ◽  
Author(s):  
Rudolf G. Mortimer
Keyword(s):  
Human Factors ◽  
Traffic Safety ◽  
Motor Vehicle ◽  
Motor Vehicles ◽  
Atmospheric Conditions ◽  
Factors Analysis ◽  
Ambient Lighting ◽  
And Performance ◽  
Road Characteristics

Injuries to pedestrians in collisions with motor vehicles are a significant problem in traffic safety, accounting for about 13% of fatalities, with more than half occurring at night. There are many variables that affect the visibility of pedestrians in darkness such as: the reflectance of their clothing, their position on the roadway, atmospheric conditions, road characteristics, street lighting, motor vehicle headlamps and their aim and alignment; other ambient lighting and background conditions, glare of headlamps of oncoming traffic and from street lamps, the driving environment and activities and performance of the driver. These issues are discussed, the techniques used to make a human factors analysis are described and some are illustrated by a case study of a night, pedestrian collision on a rural road.

scholarly journals Formação de Dutos Troposféricos no Semiárido Brasileiro: Um Estudo de Caso em Condições Meteorológicas Extremas (Formation of Tropospheric Ducts in the Brazilian Semiarid: A Case Study in Extreme Meteorological Conditions)

2013 ◽  
Vol 6 (4) ◽  
pp. 932
Author(s):  
José Batista Chaves Filho ◽  
Magaly de Fátima Correia ◽  
Carlos Diego De Souza Gurjão ◽  
Leonardo Fagner Ponciano Barbieri ◽  
Maria Regina Da Silva Aragão
Keyword(s):  
Coefficient Of Determination ◽  
Semiarid Region ◽  
Atmospheric Conditions ◽  
Thermodynamic Structure ◽  
Atmospheric Circulation Patterns ◽  
Surface Moisture ◽  
Brazilian Semiarid ◽  
Circulation Patterns ◽  
High Incidence

A influência de condições atmosféricas anômalas na refratividade e a formação de dutos troposféricos no semiárido brasileiro são avaliadas com base em dados de sondagens de ar superior efetuadas de janeiro a outubro de 2007 em Petrolina, localizada no estado de Pernambuco. Sob o ponto de vista meteorológico, mudanças significativas no padrão da circulação atmosférica afetaram substancialmente a estrutura termodinâmica e a distribuição vertical do vapor d’água na área de estudo. Os resultados mostram que a alta frequência de inversões de subsidência explica o número elevado de dutos de altitude no período de estiagem da região. Por outro lado, o coeficiente de determinação (R²) de 0,92 entre anomalias de umidade em superfície e anomalias de refratividade em fevereiro de 2007 indica que processos de evapotranspiração e transportes convectivos podem ser responsáveis pela alta incidência de dutos de superfície (49% dos casos observados) no período chuvoso da região. A B S T R A C T The influence of anomalous atmospheric conditions on the refractivity and formation of tropospheric ducts in the Brazilian semiarid region are evaluated based on upper air sounding data collected in Petrolina, located in the state of Pernambuco. Under a meteorological viewpoint, significant changes in the atmospheric circulation patterns substantially affected the thermodynamic structure and the water vapor vertical distribution in the area of study. The results show the high frequency of subsidence inversions to explain the high number of altitude ducts in the region dry season. On the other hand, the coefficient of determination (R²) of 0.92 between surface moisture anomalies and refractivity anomalies in February 2007 indicates that processes of evapotranspiration and convective transports may be responsible for the high incidence of surface ducts (49 % of the observed cases) in the region rainy season. Keywords: tropospheric ducts, refractivity, subsidence inversion, evapotranspiration

Sign in / Sign up

Export Citation Format

Share Document