scholarly journals Effects of Atmospheric Stability on Wave and Energy Propagation in the Troposphere

2007 ◽  
Vol 24 (4) ◽  
pp. 602-615 ◽  
Author(s):  
Simon P. Alexander ◽  
Toshitaka Tsuda ◽  
Junichi Furumoto
Keyword(s):  
Temporal Resolution ◽  
High Frequency ◽  
Inversion Layer ◽  
Atmospheric Stability ◽  
Vertical Wind ◽  
High Temporal Resolution ◽  
Short Time Scale ◽  
Energy Propagation ◽  
Very High Frequency ◽  
Frequency Changes

Abstract The very high frequency (VHF) middle and upper atmosphere radar radio acoustic sounding system (MU-RASS) in Shigaraki, Japan, is able to provide tropospheric virtual temperature data with high temporal resolution on the order of a few minutes. The objective of this paper is to test the usefulness of MU-RASS as a tool for examining high-frequency changes in atmospheric stability and its effects on wave and energy propagation. For this study, temperature and wind data below 8-km altitude during a 2-day campaign period in October 2001 were used. A long-lasting inversion layer at 3.5-km altitude dominated the observation period. Large vertical wind perturbations with periods of less than 30 min were observed inside this inversion layer. Wavelet analysis was used to identify the dominant wave period for calculating the wind and temperature variances. The temperature variance characteristics exhibited a combination of the horizontal and vertical wind variance characteristics. In conclusion, the high temporal resolution of the MU-RASS enabled the study of short time-scale wind and temperature perturbations. These perturbations were related to the atmospheric stability, wave propagation, and energy in the troposphere, demonstrating the usefulness of the MU-RASS for this kind of study.

scholarly journals Inferring Convective Weather Characteristics with Geostationary High Spectral Resolution IR Window Measurements: A Look into the Future

2009 ◽  
Vol 26 (8) ◽  
pp. 1527-1541 ◽  
Author(s):  
Justin M. Sieglaff ◽  
Timothy J. Schmit ◽  
W. Paul Menzel ◽  
Steven A. Ackerman
Keyword(s):  
Temporal Resolution ◽  
Spectral Resolution ◽  
Atmospheric Stability ◽  
Absorption Lines ◽  
High Spectral Resolution ◽  
High Temporal Resolution ◽  
Tropospheric Temperature ◽  
Carbon Dioxide Absorption ◽  
Water Vapor Absorption ◽  
Infrared Radiances

Abstract A high spectral resolution geostationary sounder can make spectrally detailed measurements of the infrared spectrum at high temporal resolution, which provides unique information about the lower-tropospheric temperature and moisture structure. Within the infrared window region, many spectrally narrow, relatively weak water vapor absorption lines and one carbon dioxide absorption line exist. Frequent measurement of these absorption lines can provide critical information for monitoring the evolution of the lower-tropospheric thermodynamic state. This can improve short-term convective forecasts by monitoring regions of changing atmospheric stability. While providing valuable observations, the current geostationary sounders are spectrally broad and do not resolve the important spectrally narrow absorption lines needed to observe the planetary boundary layer. The usefulness of high spectral resolution measurements from polar-orbiting instruments has been shown in the literature, as has the usefulness of high temporal resolution measurements from geostationary instruments. Little attention has been given to the combination of high temporal along with high spectral resolution measurements. This paper demonstrates the potential utility of high temporal and high spectral resolution infrared radiances.

scholarly journals New Ocean Winds Satellite Mission to Probe Hurricanes and Tropical Convection

2016 ◽  
Vol 97 (3) ◽  
pp. 385-395 ◽  
Author(s):  
Christopher S. Ruf ◽  
Robert Atlas ◽  
Paul S. Chang ◽  
Maria Paola Clarizia ◽  
James L. Garrison ◽  
...  
Keyword(s):  
Temporal Resolution ◽  
Inner Core ◽  
Dynamic Range ◽  
Surface Wind ◽  
Ocean Surface ◽  
Tropical Convection ◽  
High Temporal Resolution ◽  
Short Time Scale ◽  
Temporal Sampling ◽  
Spatial Coverage

Abstract The Cyclone Global Navigation Satellite System (CYGNSS) is a new NASA earth science mission scheduled to be launched in 2016 that focuses on tropical cyclones (TCs) and tropical convection. The mission’s two primary objectives are the measurement of ocean surface wind speed with sufficient temporal resolution to resolve short-time-scale processes such as the rapid intensification phase of TC development and the ability of the surface measurements to penetrate through the extremely high precipitation rates typically encountered in the TC inner core. The mission’s goal is to support significant improvements in our ability to forecast TC track, intensity, and storm surge through better observations and, ultimately, better understanding of inner-core processes. CYGNSS meets its temporal sampling objective by deploying a constellation of eight satellites. Its ability to see through heavy precipitation is enabled by its operation as a bistatic radar using low-frequency GPS signals. The mission will deploy an eight-spacecraft constellation in a low-inclination (35°) circular orbit to maximize coverage and sampling in the tropics. Each CYGNSS spacecraft carries a four-channel radar receiver that measures GPS navigation signals scattered by the ocean surface. The mission will measure inner-core surface winds with high temporal resolution and spatial coverage, under all precipitating conditions, and over the full dynamic range of TC wind speeds.

scholarly journals Fog dissipation through ground warming monitored by satellite image : an approach to support regional forecasting 

2021 ◽  
Author(s):  
Sylvain Cros ◽  
Martial Haeffelin ◽  
Felipe Toledo ◽  
Dupont Jean-Charles ◽  
Badosa Jordi
Keyword(s):  
Temporal Resolution ◽  
Satellite Image ◽  
Ground Level ◽  
High Temporal Resolution ◽  
Short Time Scale ◽  
Spatial Gradient ◽  
Military Operations ◽  
Air Quality Forecast ◽  
Ground Warming ◽  
Fog Dissipation

<p>By reducing the atmospheric visibility, fog events have strong impacts on several humans activities. Transport security, military operations, air quality forecast and solar energy production are critical activities considering fog dissipation time as a high valuable information.</p><p>Fog dissipation occurs through these two following processes. (1) An adiabatic cloud elevation converts the fog into a low stratus, increasing the visibility at ground level while keeping an overcast sky. (2) A radiative warming can break through a large continuous fog deck. Then, the cleared area increases progressively by heating the ground of the neighboured fog covered area.</p><p>These two events are particularly difficult to forecast using NWP models as many non-linear local processes at short-time scale are involved. Moreover, current network of fog presence sensors is too scarce to analyse and/or anticipate the phenomena. Subsequent images of geostationary meteorological satellite offer a high temporal resolution that enables to monitor large fog decks and detect punctual clear areas that induce dissipation (case 2). However, fog detection using satellite images suffers from a lack of distinction between fog and very low stratus.</p><p>In this work, we explored the potential of MSG SEVIRI radiometer through radiance observations and more advanced cloud products to analyse fog events effectively observed at the SIRTA atmospheric observatory (Palaiseau, France). We assumed that, during these events, pixels classified as “very low cloud” according to SAF-NWC algorithm were covered by fog. We monitored the evolution of these pixels using a cloud index derived from HRV channels, providing a more detailed spatial distribution of cloud cover during day time. We analysed the evolution of brightness temperature spatial gradient from the SEVIRI infrared window channel (IR 10.8µm). We isolated cases where ground warming situation could anticipate an irreversible fog dissipation. Then we deduced some fog dissipation forecasting principles.</p><p>This approach has the potential to provide to users information on morning fog sustainability with a higher accuracy and finer temporal resolution than NWP. Ongoing work focuses on characterizing favourable situations for accurate forecasts, while further predictors are investigated using recent products providing a smart distinction between fog and low stratus using SEVIRI images.</p>

scholarly journals High-Resolution Radio Acoustic Sounding System Observations and Analysis up to 20 km

2008 ◽  
Vol 25 (8) ◽  
pp. 1383-1396 ◽  
Author(s):  
Simon P. Alexander ◽  
Toshitaka Tsuda
Keyword(s):  
High Frequency ◽  
Lower Stratosphere ◽  
Energy Dissipation Rate ◽  
Energy Propagation ◽  
Acoustic Sounding ◽  
Upper Troposphere ◽  
Solar Tide ◽  
Frequency Changes ◽  
The Stability ◽  
Virtual Temperature

Abstract The first campaign-based measurements of virtual temperature in the upper-troposphere and lower-stratosphere (UTLS) region were made with the middle- and upper-atmosphere (MU) radar radio acoustic sounding system (RASS) during 4 days in August 1995. This dataset was examined in order to study high-frequency changes in the stability below 20 km, but especially in the UTLS region. Calculations of the WMO tropopause and cold-point tropopause heights showed the latter to be (1.0 ± 0.6) km higher, where 0.6 km is the standard deviation. A diurnal cycle of temperature and wind dominated the spectra, which was identified as the diurnal solar tide. Its phase maximum occurred in the afternoon between 5 and 15 km and showed upward energy propagation above this height. Changes in the UTLS kinetic energy dissipation rate ε showed significant high-frequency fluctuations embedded within layers that persisted for at least 1 day. Relative to the WMO tropopause height, the median ε increased from (0.5 ± 0.1) × 10−3 m2 s−3 in the upper troposphere to (0.7 ± 0.1) × 10−3 m2 s−3 in the lower stratosphere.

scholarly journals High-frequency productivity estimates for a lake from free-water CO<sub>2</sub> concentration measurements

2017 ◽  
Author(s):  
Maria Provenzale ◽  
Anne Ojala ◽  
Jouni Heiskanen ◽  
Kukka-Maaria Erkkilä ◽  
Ivan Mammarella ◽  
...  
Keyword(s):  
Temporal Resolution ◽  
High Frequency ◽  
Free Water ◽  
Co2 Concentration ◽  
Freshwater Ecosystems ◽  
High Temporal Resolution ◽  
Net Ecosystem Productivity ◽  
Data Set ◽  
Fully Integrated ◽  
Typical Summer

Abstract. Lakes are important actors in biogeochemical cycles and a powerful natural source of CO2. However, they are not yet fully integrated in carbon budgets, and the carbon cycle in the water is still poorly understood. In freshwater ecosystems, productivity studies have usually been carried out with traditional methods (bottle incubations, 14C technique), which are imprecise and have a poor temporal resolution. Consequently, our ability to quantify and predict the net ecosystem productivity (NEP) is limited: the estimates are prone to errors and the NEP cannot be parameterized from environmental variables. Here we expand the testing of a free-water method based on the direct measurement of the CO2 concentration in the water. The approach was proposed already in 2008, but was tested on a very short data set (3 days) under specific conditions (autumn turnover); despite showing promising results, it has not been used ever since. We tested the method under different conditions (summer stratification, typical summer conditions for boreal dark-water lakes) and on a much longer data set (40 days), and quantitatively validated it comparing our data and productivity models. We were able to evaluate the NEP with a high temporal resolution (minutes) and found an excellent agreement with the models. We also estimated the parameters of the productivity-irradiance (PI) curves that allow the calculation of the NEP from irradiance and water temperature. Overall, our work shows that the approach is suitable for productivity studies under a wider range of conditions, and is an important step towards developing it so that it becomes even more general.

SEM image sharpness analysis

1996 ◽  
Vol 54 ◽  
pp. 142-143
Author(s):  
M. T. Postek ◽  
A. E. Vladar
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Quantitative Information ◽  
Primary Electron ◽  
Image Sharpness ◽  
Critical Dimensions ◽  
Sem Image ◽  
Frequency Changes ◽  
Electron Microscopes ◽  
Scanning Electron

Fully automated or semi-automated scanning electron microscopes (SEM) are now commonly used in semiconductor production and other forms of manufacturing. The industry requires that an automated instrument must be routinely capable of 5 nm resolution (or better) at 1.0 kV accelerating voltage for the measurement of nominal 0.25-0.35 micrometer semiconductor critical dimensions. Testing and proving that the instrument is performing at this level on a day-by-day basis is an industry need and concern which has been the object of a study at NIST and the fundamentals and results are discussed in this paper.In scanning electron microscopy, two of the most important instrument parameters are the size and shape of the primary electron beam and any image taken in a scanning electron microscope is the result of the sample and electron probe interaction. The low frequency changes in the video signal, collected from the sample, contains information about the larger features and the high frequency changes carry information of finer details. The sharper the image, the larger the number of high frequency components making up that image. Fast Fourier Transform (FFT) analysis of an SEM image can be employed to provide qualitiative and ultimately quantitative information regarding the SEM image quality.

Multidetector-row Computed Tomography in the Assessment of Coronary Artery Disease – New Techniques and Insights

2010 ◽  
Vol 6 (2) ◽  
pp. 43 ◽  
Author(s):  
Andreas H Mahnken ◽  
Keyword(s):  
Computed Tomography ◽  
Coronary Artery Disease ◽  
Coronary Artery ◽  
Data Acquisition ◽  
Temporal Resolution ◽  
High Temporal Resolution ◽  
Multidetector Row ◽  
Ct Scanners ◽  
Artery Disease ◽  
Cardiac Mdct

Over the last decade, cardiac computed tomography (CT) technology has experienced revolutionary changes and gained broad clinical acceptance in the work-up of patients suffering from coronary artery disease (CAD). Since cardiac multidetector-row CT (MDCT) was introduced in 1998, acquisition time, number of detector rows and spatial and temporal resolution have improved tremendously. Current developments in cardiac CT are focusing on low-dose cardiac scanning at ultra-high temporal resolution. Technically, there are two major approaches to achieving these goals: rapid data acquisition using dual-source CT scanners with high temporal resolution or volumetric data acquisition with 256/320-slice CT scanners. While each approach has specific advantages and disadvantages, both technologies foster the extension of cardiac MDCT beyond morphological imaging towards the functional assessment of CAD. This article examines current trends in the development of cardiac MDCT.

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