Recent Advances in the Understanding of Near-Cloud Turbulence

2012 ◽  
Vol 93 (4) ◽  
pp. 499-515 ◽  
Author(s):  
Todd P. Lane ◽  
Robert D. Sharman ◽  
Stanley B. Trier ◽  
Robert G. Fovell ◽  
John K. Williams
Keyword(s):  
Hazard Identification ◽  
Commercial Aircraft ◽  
Convective Clouds ◽  
Air Turbulence ◽  
Reporting Systems ◽  
Deep Convective Clouds ◽  
Airline Passengers ◽  
Research Questions ◽  
Upper Level ◽  
The Cost

Anyone who has flown in a commercial aircraft is familiar with turbulence. Unexpected encounters with turbulence pose a safety risk to airline passengers and crew, can occasionally damage aircraft, and indirectly increase the cost of air travel. Deep convective clouds are one of the most important sources of turbulence. Cloud-induced turbulence can occur both within clouds and in the surrounding clear air. Turbulence associated with but outside of clouds is of particular concern because it is more difficult to discern using standard hazard identification technologies (e.g., satellite and radar) and thus is often the source of unexpected turbulence encounters. Although operational guidelines for avoiding near-cloud turbulence exist, they are in many ways inadequate because they were developed before the governing dynamical processes were understood. Recently, there have been significant advances in the understanding of the dynamics of near-cloud turbulence. Using examples, this article demonstrates how these advances have stemmed from improved turbulence observing and reporting systems, the establishment of archives of turbulence encounters, detailed case studies, and high-resolution numerical simulations. Some of the important phenomena that have recently been identified as contributing to near-cloud turbulence include atmospheric wave breaking, unstable upper-level thunderstorm outflows, shearing instabilities, and cirrus cloud bands. The consequences of these phenomena for developing new en route turbulence avoidance guidelines and forecasting methods are discussed, along with outstanding research questions.

scholarly journals SIMULASI NUMERIK MEKANISME TURBULENSI DEKAT AWAN KONVEKTIF

2021 ◽  
Vol 22 (1) ◽  
pp. 25-33
Author(s):  
Ni Putu Tiana Verayanti ◽  
I Kadek Nova Arta Kusuma
Keyword(s):  
Kinetic Energy ◽  
Satellite Imagery ◽  
Wind Shear ◽  
Richardson Number ◽  
Vertical Wind Shear ◽  
Commercial Aircraft ◽  
Convective Clouds ◽  
Air Turbulence ◽  
North Sumatra ◽  
Cumulonimbus Cloud

Intisari Turbulensi yang dialami oleh pesawat komersial rute Jakarta-Medan telah dilaporkan mengalami Clear Air Turbulence (CAT) di atas Sumatera Utara pada tanggal 24 Oktober 2017. Namun berdasarkan data citra satelit Himawari dari Badan Meteorologi, Klimatologi, dan Geofisika (BMKG) Indonesia menyebutkan bahwa di sekitar lokasi turbulensi terdapat awan kumulonimbus. Penelitian ini memanfaatkan model WRF-ARW dengan resolusi spasial dan temporal tinggi untuk mengetahui secara detail proses yang terjadi pada awan konvektif penyebab Near Cloud Turbulence (NCT). Turbulensi tersebut disebabkan oleh bilangan Richardson rendah yang terbentuk di wilayah udara jernih (clear air) yang berjarak 300-700 m di atas puncak awan dan diperkuat dengan adanya Turbulensi Energi Kinetik (TKE) mencapai 4,4 m2 / s2 dan geser angin vertikal (VWS) oleh arus keluar awan konvektif.  Abstract Turbulence encountered by commercial aircraft Jakarta-Medan routes has been reported that experienced Clear Air Turbulence (CAT) over North Sumatra on October 24th, 2017. However, based on Himawari satellite imagery data produced by Agency for Meteorology, Climatology, and Geophysics (BMKG), Indonesia stated that there was a cumulonimbus cloud around the turbulence location. This study utilizes WRF-ARW models with a high spatial and temporal resolution to find out in detail the processes that occur in convective clouds causing Near Cloud Turbulence (NCT). The turbulence was caused by a low Richardson number formed in the clear-air area, which has a distance of 300 - 700 m above the cloud top and reinforced by the existence of Turbulence Kinetic Energy (TKE) reaching 4,4 m2/s2 and vertical wind shear (VWS) by deep convection’s outflow.

scholarly journals Tropical, oceanic, deep convective cloud morphology as observed by CloudSat

2015 ◽  
Vol 15 (11) ◽  
pp. 15977-16017 ◽  
Author(s):  
M. R. Igel ◽  
S. C. van den Heever
Keyword(s):  
Convective Cloud ◽  
Data Partitioning ◽  
Width Ratio ◽  
Length Scales ◽  
Morphological Attributes ◽  
Convective Clouds ◽  
Deep Convective Clouds ◽  
Physical Shape ◽  
The Mean ◽  
Upper Level

Abstract. An investigation into the physical shape and size of mature, oceanic, tropical, deep convective clouds is conducted. A previously developed CloudSat data-partitioning methodology is used that separates components of cloud objects and measures their various length scales. In particular, the cloud objects are divided into a lower "pedestal" region on which the upper-level "anvil" region sits. Mean cloud objects are discussed in the framework of this morphological partitioning. For single-core clouds, the mean cloud has an anvil width of 95 km, a pedestal width of 11 km, and an anvil thickness of 6.4 km. The number of identified convective cores within the pedestal correlates positively with certain cloud length scales and morphological attributes of cloud objects such as anvil width. As the number of cores increases, the width of cloud objects is observed to grow. Pedestal width is shown to regress linearly to anvil width when a 2/3rd power scaling is applied to pedestal width. This result implies a decrease in the anvil width to pedestal width ratio with growing pedestals and an equivalence between the mass convected through the pedestal top and that into the anvil. Taller clouds are found to be wider. Some of the results obtained using the CloudSat methodology are also examined with a large-domain radiative-convective equilibrium numerical simulation and are found to exhibit similar trends when modeled. Finally, various CloudSat sampling issues are discussed in several appendices.

scholarly journals The Impact of Supply Chain Management on Financial Performance and Responsibility Accounting Agribusiness Case from Egypt

2017 ◽  
Vol 6 (2) ◽  
pp. 136 ◽  
Author(s):  
Mohamed Ali Wahdan ◽  
Mohamed Ashraf Emam
Keyword(s):  
Supply Chain ◽  
Supply Chain Management ◽  
Financial Performance ◽  
Financial Statements ◽  
Net Income ◽  
Chain Management ◽  
Research Questions ◽  
The Cost ◽  
The Impact ◽  
Responsibility Accounting

This paper presents the impact of applying the supply chain management (SCM) on the agribusiness field to optimize productivity and decreasing cost which will have a direct impact on the net income of the organization. The main two research questions are: is there a significant impact of supply chain management on financial performance? and is there a significant relationship between supply chain management and financial performance as well as responsibility accounting? To answer the research questions, data was collected from financial statements of agribusiness case from Egypt and the survey was conducted. The findings of the study indicated that there is a significant impact of supply chain management on financial performance through enhancing the productivity, decreasing the cost and improving profitability. Moreover, applying the efficient supply chain management can improve the use of responsibility accounting through the efficient usage for the budget of the crop.

scholarly journals Frequency of deep convective clouds in the tropical zone from 10 years of AIRS data

2013 ◽  
Vol 13 (21) ◽  
pp. 10795-10806 ◽  
Author(s):  
H. H. Aumann ◽  
A. Ruzmaikin
Keyword(s):  
Brightness Temperature ◽  
Frequency Of Occurrence ◽  
Tropical Zone ◽  
Convective Clouds ◽  
The Past ◽  
Atmospheric Window ◽  
Deep Convective Clouds ◽  
Sst Anomaly ◽  
The Difference ◽  
Global Precipitation

Abstract. Deep convective clouds (DCCs) have been widely studied because of their association with heavy precipitation and severe weather events. Changes in the properties of DCCs are likely in a changing climate. Ten years of data collected by Atmospheric Infrared Sounder (AIRS) allow us to identify decadal trends in frequency of occurrence of DCCs over land and ocean. In the past, DCCs have been identified in the thermal infrared by three methods: (1) thresholds based on the absolute value of an atmospheric window channel brightness temperature; (2) thresholds based on the difference between the brightness temperature in an atmospheric window channel and the brightness temperature centered on a strong water vapor absorption line; and (3) a threshold using the difference between the window channel brightness temperature and the tropopause temperature based on climatology. Simultaneous observations of these infrared identified DCCs with the Advanced Microwave Sounding Unit–Humidity Sounder for Brazil (AMSU-HSB) using 183 GHz water channels provide a statistical correlation with microwave deep convection and overshooting convection. In the past 10 years, the frequency of occurrence of DCCs has decreased for the tropical ocean, while it has increased for tropical land. The area of the tropical zone associated with DCCs is typically much less than 1%. We find that the least frequent, more extreme DCCs show the largest trend in frequency of occurrence, increasing over land and decreasing over ocean. The trends for land and ocean closely balance, such that the DCC frequency changed at an insignificant rate for the entire tropical zone. This pattern of essentially zero trend for the tropical zone, but opposite land/ocean trends, is consistent with measurements of global precipitation. The changes in frequency of occurrence of the DCCs are correlated with the Niño34 index, which defines the sea surface temperature (SST) anomaly in the east-central Pacific. This is also consistent with patterns seen in global precipitation. This suggests that the observed changes in the frequency are part of a decadal variability characterized by shifts in the main tropical circulation patterns, which does not fully balance in the 10-year AIRS data record. The regional correlations and anti-correlations of the DCC frequency anomaly with the Multivariate ENSO Index (MEI) provide a new perspective for the regional analysis of past events, since the SST anomaly in the Nino34 region is available in the form of the extended MEI from 1871.

scholarly journals How do changes in warm-phase microphysics affect deep convective clouds?

2017 ◽  
Vol 17 (15) ◽  
pp. 9585-9598 ◽  
Author(s):  
Qian Chen ◽  
Ilan Koren ◽  
Orit Altaratz ◽  
Reuven H. Heiblum ◽  
Guy Dagan ◽  
...  
Keyword(s):  
Rain Rate ◽  
Convective Cloud ◽  
Cloud Fraction ◽  
Marshall Islands ◽  
Cloud System ◽  
Main Question ◽  
Convective Clouds ◽  
Deep Convective Clouds ◽  
Aerosol Effects ◽  
Deep Convective Cloud

Abstract. Understanding aerosol effects on deep convective clouds and the derived effects on the radiation budget and rain patterns can largely contribute to estimations of climate uncertainties. The challenge is difficult in part because key microphysical processes in the mixed and cold phases are still not well understood. For deep convective clouds with a warm base, understanding aerosol effects on the warm processes is extremely important as they set the initial and boundary conditions for the cold processes. Therefore, the focus of this study is the warm phase, which can be better resolved. The main question is: How do aerosol-derived changes in the warm phase affect the properties of deep convective cloud systems? To explore this question, we used a weather research and forecasting (WRF) model with spectral bin microphysics to simulate a deep convective cloud system over the Marshall Islands during the Kwajalein Experiment (KWAJEX). The model results were validated against observations, showing similarities in the vertical profile of radar reflectivity and the surface rain rate. Simulations with larger aerosol loading resulted in a larger total cloud mass, a larger cloud fraction in the upper levels, and a larger frequency of strong updrafts and rain rates. Enlarged mass both below and above the zero temperature level (ZTL) contributed to the increase in cloud total mass (water and ice) in the polluted runs. Increased condensation efficiency of cloud droplets governed the gain in mass below the ZTL, while both enhanced condensational and depositional growth led to increased mass above it. The enhanced mass loading above the ZTL acted to reduce the cloud buoyancy, while the thermal buoyancy (driven by the enhanced latent heat release) increased in the polluted runs. The overall effect showed an increased upward transport (across the ZTL) of liquid water driven by both larger updrafts and larger droplet mobility. These aerosol effects were reflected in the larger ratio between the masses located above and below the ZTL in the polluted runs. When comparing the net mass flux crossing the ZTL in the clean and polluted runs, the difference was small. However, when comparing the upward and downward fluxes separately, the increase in aerosol concentration was seen to dramatically increase the fluxes in both directions, indicating the aerosol amplification effect of the convection and the affected cloud system properties, such as cloud fraction and rain rate.

scholarly journals Vertical distribution of the phase state of particles in tropical deep-convective clouds as derived from cloud-side reflected solar radiation measurements

2017 ◽  
Author(s):  
Evelyn Jäkel ◽  
Manfred Wendisch ◽  
Trismono C. Krisna ◽  
Florian Ewald ◽  
Tobias Kölling ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Phase State ◽  
Lower Boundary ◽  
Mixed Phase ◽  
Vertical Position ◽  
Cloud Particle ◽  
Phase Layer ◽  
Spectral Reflectivity ◽  
Convective Clouds ◽  
Deep Convective Clouds

Abstract. Vertical profiles of the cloud particle phase state in tropical deep-convective clouds (DCCs) were investigated using airborne solar radiation data collected by the German research aircraft HALO during the ACRIDICON-CHUVA campaign, which was conducted over the Brazilian Amazon in September 2014. A phase discrimination retrieval based on imaging spec-troradiometer measurements of cloud side spectral reflectivity was applied to DCCs under different aerosol conditions. From the retrieval results the height of the mixed phase layer of the DCCs was determined. The retrieved profiles were compared with in situ measurements and satellite observations. It was found that the depth and vertical position of the mixed phase layer can vary up to 900 m for one single cloud scene. In particular, this variation is attributed to the different stages of cloud development in one scene. Clouds of mature or decaying stage are affected by falling ice particles resulting in lower levels of fully glaciated cloud layers compared to growing clouds. Comparing polluted and moderate aerosol conditions revealed a shift of the lower boundary of the mixed phase layer from 5.6 ± 0.2 km (269 K) [moderate] to 6.2 ± 0.3 km (267 K) [polluted], and of the upper boundary from 6.8 ± 0.2 km (263 K) [moderate] to 7.4 ± 0.4 km (259 K) [polluted], as would be expected from theory.

scholarly journals Retrieving clear-air turbulence information from regular commercial aircraft using Mode-S and ADS-B broadcast

2015 ◽  
Vol 8 (11) ◽  
pp. 11817-11852 ◽  
Author(s):  
J. M. Kopeć ◽  
K. Kwiatkowski ◽  
S. de Haan ◽  
S. P. Malinowski
Keyword(s):  
Dissipation Rate ◽  
Vertical Acceleration ◽  
Background Wind ◽  
Commercial Aircraft ◽  
Processing Methods ◽  
Turbulence Measurements ◽  
Significant Potential ◽  
Air Turbulence ◽  
Research Aircraft ◽  
Comparison Of The Results

Abstract. Navigational information broadcast by commercial aircraft in the form of Mode-S and ADS-B messages can be considered a new and valid source of upper air turbulence measurements. A set of three processing methods is proposed and analysed using a quality record of turbulence encounters made by a research aircraft. The proposed methods are based on processing the vertical acceleration or the background wind into the eddy dissipation rate. All the necessary parameters are conveyed in the Mode-S/ADS-B messages. The comparison of the results of application of the processing against a reference eddy dissipation rate obtained using on-board accelerometer indicate a significant potential of those methods. The advantages and limitation of the presented approaches are discussed.

scholarly journals ENROLMENT PROJECTION AND COST IMPLICATION OF UNIVERSAL BASIC EDUCATION IN NIGERIA

2015 ◽  
Vol 16 (2) ◽  
pp. 15
Author(s):  
V. O. Igbineweka ◽  
J. K. Adeyemi
Keyword(s):  
Basic Education ◽  
Previous Experiment ◽  
Cost Implication ◽  
Universal Basic Education ◽  
Governmental Organizations ◽  
Documentary Analysis ◽  
Non Governmental Organizations ◽  
Research Questions ◽  
The Cost ◽  
Analysis Models

The paper evaluated implementation of the Universal Basic Education (UBE) scheme for the first ten years of implementation, 2002-2012. Pupil enrolment for the period was projected and the cost implication of implementing the scheme estimated to guide government assess its ability to continue the implementation of the scheme, review its strategies of implementation or even abandon the scheme like the previous experiment with UBE scheme. The two research questions raised for the study were answered using documentary analysis, models and descriptive statistics. The result of analysis showed that over 46 million children would have been enrolled in schools and N52.9 billion spent annually if the scheme had been effectively implemented. The sight of basic school-going aged children at motor parks, markets and hawking along major streets during school hours suggests that the implementation of the scheme has not effective. It was therefore recommended among others that government should concentrate only on the supply and management of basic education in order to garner adequate funds to sustain its implementation and, allow private individuals and non-governmental organizations to supply and manage other levels of education.

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