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Eipper, Daniel T., Steven J. Greybush, George S. Young, Seth Saslo, Todd D. Sikora und Richard D. Clark. „Lake-Effect Snowbands in Baroclinic Environments“. Weather and Forecasting 34, Nr. 6 (17.10.2019): 1657–74. http://dx.doi.org/10.1175/waf-d-18-0191.1.
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Abstract Lake-effect snowstorms are often observed to manifest as dominant bands, commonly produce heavy localized snowfall, and may extend large distances inland, resulting in hazards and high societal impact. Some studies of dominant bands have documented concomitant environmental baroclinity (i.e., baroclinity occurring at a scale larger than the width of the parent lake), but the interaction of this baroclinity with the inland structure of dominant bands has been largely unexplored. In this study, the thermodynamic environment and thermodynamic and kinematic structure of simulated dominant bands are examined using WRF reanalyses at 3-km horizontal resolution and an innovative technique for selecting the most representative member from the WRF ensemble. Three reanalysis periods are selected from the Ontario Winter Lake-effect Systems (OWLeS) field campaign, encompassing 185 simulation hours, including 155 h in which dominant bands are identified. Environmental baroclinity is commonly observed during dominant-band periods and occurs in both the north–south and east–west directions. Sources of this baroclinity are identified and discussed. In addition, case studies are conducted for simulation hours featuring weak and strong along-band environmental baroclinity, resulting in weak and strong inland extent, respectively. These contrasting cases offer insight into one mechanism by which along-band environmental baroclinity can influence the inland structure and intensity of dominant bands: in the case with strong environmental baroclinity, inland portions of this band formed under weak instability and therefore exhibit slow overturning, enabling advection far inland under strong winds, whereas the nearshore portion forms under strong instability, and the enhanced overturning eventually leads to the demise of the inland portion of the band.
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Connelly, Ryan, und Brian A. Colle. „Validation of Snow Multibands in the Comma Head of an Extratropical Cyclone Using a 40-Member Ensemble“. Weather and Forecasting 34, Nr. 5 (11.09.2019): 1343–63. http://dx.doi.org/10.1175/waf-d-18-0182.1.
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Abstract This paper investigates the ability of the Weather Research and Forecasting (WRF) Model in simulating multiple small-scale precipitation bands (multibands) within the extratropical cyclone comma head using four winter storm cases from 2014 to 2017. Using the model output, some physical processes are explored to investigate band prediction. A 40-member WRF ensemble was constructed down to 2-km grid spacing over the Northeast United States using different physics, stochastic physics perturbations, different initial/boundary conditions from the first five perturbed members of the Global Forecast System (GFS) Ensemble Reforecast (GEFSR), and a stochastic kinetic energy backscatter scheme (SKEBS). It was found that 2-km grid spacing is adequate to resolve most snowbands. A feature-based verification is applied to hourly WRF reflectivity fields from each ensemble member and the WSR-88D radar reflectivity at 2-km height above sea level. The Method for Object-Based Diagnostic Evaluation (MODE) tool is used for identifying multibands, which are defined as two or more bands that are 5–20 km in width and that also exhibit a >2:1 aspect ratio. The WRF underpredicts the number of multibands and has a slight eastward position bias. There is no significant difference in frontogenetical forcing, vertical stability, moisture, and vertical shear between the banded versus nonbanded members. Underpredicted band members tend to have slightly stronger frontogenesis than observed, which may be consolidating the bands, but overall there is no clear linkage in ambient condition errors and band errors, thus leaving the source for the band underprediction motivation for future work.
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Jurewicz, Michael L., und Michael S. Evans. „A Comparison of Two Banded, Heavy Snowstorms with Very Different Synoptic Settings“. Weather and Forecasting 19, Nr. 6 (01.12.2004): 1011–28. http://dx.doi.org/10.1175/waf-823.1.
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Abstract Two banded, heavy snowstorms that occurred over the northern mid-Atlantic region are compared and contrasted. On 6–7 January 2002, a narrow, intense band of heavy snow was observed, along with several other weaker bands, embedded within a large area of moderate snow. On 19–20 January 2002, a single, broader band of heavy snow was observed, embedded within a broken area of light snow. The synoptic-scale settings associated with these two storms were strikingly dissimilar. In the first case, strong quasigeostrophic (QG) forcing for ascent was present just to the south of the heavy snowfall area. A highly amplified longwave trough was located over the Mississippi River valley, while a compact shortwave trough moved northward, up the east side of the longwave trough. The result was robust cyclogenesis off of the mid-Atlantic coast. In the second case, the relatively weaker QG forcing for ascent was located much farther southwest of the snowband. The flow aloft was much less amplified, with weaker cyclogenesis occurring off of the mid-Atlantic coast. Analysis of the frontal scale environments for both cases indicated that the snowbands were each associated with the collocation of midtropospheric frontogenesis and reduced stability. In the first case, evidence is shown that a layer of potential symmetric instability (PSI) was located just above a deep, sloping zone of frontogenesis, in the presence of deep near-saturated conditions. In the second case, evidence is shown that a layer of potential instability (PI), associated with rapidly decreasing relative humidity with height, was located just above a shallow, sloping zone of frontogenesis. In addition, it is shown that a particularly favorable thermal environment for snowflake growth and accumulation became collocated with the heavy snowband. It is hypothesized that the differences in the intensity and horizontal extent of the bands observed with these two events resulted from differing atmospheric responses associated with the areal extent of large-scale and frontogenetical forcing, moisture availability, degree of instability, and specific thermal profiles.
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Eipper, Daniel T., George S. Young, Steven J. Greybush, Seth Saslo, Todd D. Sikora und Richard D. Clark. „Predicting the Inland Penetration of Long-Lake-Axis-Parallel Snowbands“. Weather and Forecasting 33, Nr. 5 (01.10.2018): 1435–51. http://dx.doi.org/10.1175/waf-d-18-0033.1.
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Abstract Predicting the inland penetration of lake-effect long-lake-axis-parallel (LLAP) snowbands is crucial to public safety because LLAP bands can produce hazardous weather well downwind of the parent lake. Accordingly, hypotheses for the variation in inland penetration of LLAP-band radar echoes (InPen) are formulated and tested. The hypothesis testing includes an examination of statistical relationships between environmental variables and InPen for 34 snapshots of LLAP bands observed during the Ontario Winter Lake-effect Systems (OWLeS) field campaign. Several previously proposed predictors of LLAP-band formation or InPen demonstrate weak correlations with InPen during OWLeS. A notable exception is convective boundary layer (CBL) depth, which is strongly correlated with InPen. In addition to CBL depth, InPen is strongly correlated with cold-air advection in the upper portion of the CBL, suggesting that boundary layer destabilization produced by vertically differential cold-air advection may be an important inland power source for preexisting LLAP bands. This power production is quantified through atmospheric energetics and the resulting variable, differential thermal advection power (DTAP), yields reasonably skillful predictions of InPen. Nevertheless, an InPen model developed using DTAP is outperformed by an empirical model combining CBL depth and potential temperature advection in the upper portion of the CBL. This two-variable model explains 76% of the observed InPen variance when tested on independent data. Finally, implications for operational forecasting of InPen are discussed.
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Radford, Jacob T., Gary M. Lackmann und Martin A. Baxter. „An Evaluation of Snowband Predictability in the High-Resolution Rapid Refresh“. Weather and Forecasting 34, Nr. 5 (01.10.2019): 1477–94. http://dx.doi.org/10.1175/waf-d-19-0089.1.
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Abstract Narrow regions of intense, banded snowfall present hazardous travel conditions due to rapid onset, high precipitation rates, and lowered visibility. Despite their importance, there are few verification studies of snowbands in operational forecast models. The objective of this study is to evaluate the ability of the High-Resolution Rapid Refresh (HRRR) model to predict snowbands in the United States east of the Rocky Mountains. An automated band-detection algorithm was applied to a 3-yr period of simulated and observed radar reflectivity to compare snowband climatologies. This algorithm uses the distributions of reflectivities in contiguous precipitation regions to determine a band intensity threshold. The predictability of snowbands on a case-by-case basis was also evaluated using an object-oriented approach. The distribution of HRRR forecast banding resembles that of the observations, but with a significant positive frequency bias. This may partially be due to underrepresentation of observed bands in our verification dataset due to limited radar coverage in portions of the central United States. On a case-by-case basis, traditional skill metrics indicate limited predictability, but allowing for small timing discrepancies dramatically improves scores. Object-oriented verification yields mixed results, with 30% of forecasts receiving a score indicative of a well-predicted event. However, 69% of cases have at least one forecast lead demonstrating skill, suggesting the HRRR is successful in depicting environments conducive to band formation. These results suggest adopting a probabilistic, ensemble approach, and indicate that the deterministic HRRR is best suited for the identification of regions of elevated snowband risk and not precise timing or location information.
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Moore, James T., Charles E. Graves, Sam Ng und Jamie L. Smith. „A Process-Oriented Methodology Toward Understanding the Organization of an Extensive Mesoscale Snowband: A Diagnostic Case Study of 4–5 December 1999“. Weather and Forecasting 20, Nr. 1 (01.02.2005): 35–50. http://dx.doi.org/10.1175/waf-829.1.
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Abstract A case study of a long, narrow band of heavy snowfall is presented that illustrates those processes that force and focus the precipitation in a unique linear fashion. System-relative flow on isentropic surfaces shows how the trough of warm air aloft (trowal) formed to the north-northwest of a weak synoptic-scale surface cyclone. To the north of the trowal, midtropospheric frontogenesis formed as the warm, moist, high-θe air in the trowal canyon became confluent with cold, dry air to the northwest of a closed midlevel circulation. Within the trowal airstream, isentropic uplsope is shown to contribute to vertical motion, while transverse to this flow, mesoscale lift is enhanced on the warm side of a frontogenetical zone in the presence of weak symmetric stability and conditional symmetric instability. Further, it is shown that a sloping zone of small positive to negative equivalent potential vorticity forms to the southeast of the midtropospheric system-relative closed circulation as low-θe air associated with the dry conveyor belt, seen in water vapor imagery, overruns warm, moist high-θe air associated with the warm conveyor belt. In this way cold season instability forms due to differential moisture advection on the warm side of the frontogenesis axis. Finally, a conceptual model is shown that encapsulates the key processes that contributed to the extensive, narrow band of heavy snow in the presence of a weak synoptic-scale surface cyclone.
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Mahale, Vivek N., Jerald A. Brotzge und Howard B. Bluestein. „The Advantages of a Mixed-Band Radar Network for Severe Weather Operations: A Case Study of 13 May 2009“. Weather and Forecasting 29, Nr. 1 (01.02.2014): 78–98. http://dx.doi.org/10.1175/waf-d-13-00024.1.
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Abstract Adding a mix of X- or C-band radars to the current Weather Surveillance Radar-1988 Doppler (WSR-88D) network could address several limitations of the network, including improvements to spatial gaps in low-level coverage and temporal sampling of volume scans. These limitations can result in missing critical information in highly dynamic events, such as tornadoes and severe straight-line wind episodes. To evaluate the potential value of a mixed-band radar network for severe weather operations, a case study is examined using data from X- and S-band radars. On 13 May 2009, a thunderstorm complex associated with a cold front moved southward into southwest Oklahoma. A tornado rapidly developed from an embedded supercell within the complex. The life cycle of the tornado and subsequent wind event was sampled by the experimental Collaborative Adaptive Sensing of the Atmosphere (CASA) radar testbed of four X-band radars as well as two operational WSR-88Ds. In this study, the advantages of a mixed-band radar network are demonstrated through a chronological analysis of the event. The two radar networks provided enhanced overall situational awareness. Data from the WSR-88Ds provided 1) clear-air sensitivity, 2) a broad overview of the storm complex, 3) a large maximum unambiguous range, and 4) upper-level scans up to 19.5°. Data from the CASA radars provided 1) high-temporal, 1-min updates; 2) overlapping coverage for dual-Doppler analysis; and 3) dense low-level coverage. The combined system allowed for detailed, dual- and single-Doppler observations of a wind surge, a mesocyclone contraction, and a downburst.
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Kenyon, Jaymes S., Daniel Keyser, Lance F. Bosart und Michael S. Evans. „The Motion of Mesoscale Snowbands in Northeast U.S. Winter Storms“. Weather and Forecasting 35, Nr. 1 (13.01.2020): 83–105. http://dx.doi.org/10.1175/waf-d-19-0038.1.
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Abstract The spatial distribution of snowfall accumulation accompanying winter storms is a product of both snowfall rate and duration. Winter storms are commonly associated with mesoscale snowbands that can strongly modulate snowfall accumulation. Although the development of mesoscale snowbands can usually be anticipated, snowband residence time at a fixed location is often a forecasting challenge. However, given that snowband residence time is related to characteristics of band motion, an improved understanding of band motion presents an opportunity to improve snowfall-accumulation forecasts. This study investigates environmental features associated with specific snowband motion characteristics. Using radar reflectivity data, snowband events in the northeast United States spanning a 6-yr period are categorized according to a band-motion classification scheme, with this scheme consisting of laterally translating, hybrid, laterally quasi-stationary, and pivoting snowbands. On the basis of this classification, composite analysis is performed to identify common environmental features associated with particular band-motion categories. Results indicate that snowband motion is related to cyclone-relative band position, the confluence/diffluence and curvature of midlevel streamlines, and the distribution of horizontal temperature advection. Snowband motion is also related to hodograph shape, as well as to the across- and along-isotherm components of the Q vector. Composite results are supplemented with case studies, which suggest that laterally quasi-stationary and pivoting snowbands can favor distinct gradients in snowfall accumulation. The present study proposes that snowband motion warrants consideration during the forecasting process and, to that end, conceptual models are presented to synthesize key findings for operational application.
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Novak, David R., und Brian A. Colle. „Diagnosing Snowband Predictability Using a Multimodel Ensemble System“. Weather and Forecasting 27, Nr. 3 (01.06.2012): 565–85. http://dx.doi.org/10.1175/waf-d-11-00047.1.
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Abstract The forecast uncertainty of mesoscale snowband formation and evolution is compared using predictions from a 16-member multimodel ensemble at 12-km grid spacing for the 25 December 2002, 12 February 2006, and 14 February 2007 northeast U.S. snowstorms. Using these predictions, the case-to-case variability in the predictability of band formation and evolution is demonstrated. Feature-based uncertainty information is also presented as an example of what may be operationally feasible from postprocessing information from future short-range ensemble forecast systems. Additionally, the initial condition sensitivity of band location in each case is explored by contrasting the forecast evolutions of initial condition members with large differences in snowband positions. Considerable uncertainty in the occurrence, and especially timing and location, of band formation and subsequent evolution was found, even at forecast projections <24 h. The ensemble provided quantitative mesoscale band uncertainty information, and differentiated between high-predictability (14 February 2007) and low-predictability (12 February 2006) cases. Among the three cases, large (small) initial differences in the upper-level PV distribution and surface mean sea level pressure of the incipient cyclone were associated with large (small) differences in forecast snowband locations, suggesting that case-to-case differences in predictability may be related to the quality of the initial conditions. The complexity of the initial flow may also be a discriminator. Error growth was evident in each case, consistent with previous mesoscale predictability research, but predictability differences were not correlated to the degree of convection. Discussion of these results and future extensions of the work are presented.
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He, Guangxin, Gang Li, Xiaolei Zou und Peter Sawin Ray. „Applications of a Velocity Dealiasing Scheme to Data from the China New Generation Weather Radar System (CINRAD)“. Weather and Forecasting 27, Nr. 1 (01.02.2012): 218–30. http://dx.doi.org/10.1175/waf-d-11-00054.1.
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Abstract An improved velocity dealiasing algorithm is developed as an extension of the Next Generation Weather Radar (NEXRAD) dealiasing algorithm. The algorithm described in this paper is evaluated on selected China Next Generation Weather Radar (CINRAD) S-band radar radial velocity observations. This algorithm includes four modules for removing weak signals and determining the starting radial as a prelude to identifying and correcting aliased velocities. The proposed dealiasing algorithm was tested on 14 different weather systems, composed of typhoons, squall lines, and heavy rains. The results show that the algorithm is robust and stable for dealiasing S-band CINRAD radial velocity measurements. The performance levels for the typhoon and heavy rain cases are slightly better than for squall-line cases.
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Tai, Sai-Choi, Edwin Wing-Lui Ginn und Chiu-Ying Lam. „Dual-Doppler Observations of Severe Tropical Storm Maggie 1999“. Weather and Forecasting 20, Nr. 1 (01.02.2005): 112–23. http://dx.doi.org/10.1175/waf-828.1.
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Abstract Severe Tropical Storm Maggie crossed Hong Kong, China, in June 1999. The dual-Doppler winds of Maggie captured by the Hong Kong Observatory's (HKO) S-band Doppler weather radar array were studied. The tracks of Maggie's vorticity centers at 1–3-km levels were analyzed and compared with that at the surface as determined from the wind observations of automatic weather stations. The results indicated that the storm had a vertical tilt toward the west to northwest during the transit over Hong Kong. The tracks also deviated significantly from the deep-layer environmental steering flow. The southward movement and vertical tilt could be partly attributed to the easterly vertical shear in the ambient flow. But the terrain of Hong Kong could have also played a significant role in the lowest 1 km of the atmosphere. The tendency of the storm track to avoid mountains was well illustrated and may serve as a useful forecasting guidance indicator for tropical areas with significant terrain. Experimental runs of a nonhydrostatic model at 5-km resolution were able to simulate the broad west-southwestward movement of Maggie and the vertical tilt of the circulation near the center of the tropical cyclone as revealed by the dual-Doppler observations.
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Amiot, Corey G., Lawrence D. Carey, William P. Roeder, Todd M. McNamara und Richard J. Blakeslee. „C-band Dual-Polarization Radar Signatures of Wet Downbursts around Cape Canaveral, Florida“. Weather and Forecasting 34, Nr. 1 (10.01.2019): 103–31. http://dx.doi.org/10.1175/waf-d-18-0081.1.
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Abstract Wind warnings are the second-most-frequent advisory issued by the U.S. Air Force’s 45th Weather Squadron (45WS) at Cape Canaveral, Florida. Given the challenges associated with nowcasting convection in Florida during the warm season, improvements in 45WS warnings for convective wind events are desired. This study aims to explore the physical bases of dual-polarization radar signatures within wet downbursts around Cape Canaveral and identify signatures that may assist the 45WS during real-time convective wind nowcasting. Data from the 45WS’s C-band dual-polarization radar were subjectively analyzed within an environmental context, with quantitative wind measurements recorded by weather tower sensors for 32 threshold-level downbursts with near-surface winds ≥ 35 kt (1 kt ≈ 0.51 m s−1) and 32 null downbursts. Five radar signatures were identified in threshold-level downburst-producing storms: peak height of 1-dB differential reflectivity ZDR column, peak height of precipitation ice signature, peak reflectivity, height below 0°C level where ZDR increases to 3 dB within a descending reflectivity core (DRC), and vertical ZDR gradient within DRC. Examining these signatures directly in updraft–downdraft cycles that produced threshold-level winds yielded mean lead times of 20.0–28.2 min for cumulus and mature stage signatures and 12.8–14.9 min for dissipating stage signatures, with higher signature test values generally yielding higher skill scores. A conceptual test of utilizing signatures within earlier cells in multicell storms to indirectly predict the potential for intense downbursts in later cells was performed, which offered increased lead times and skill scores for an Eulerian forecast region downstream from the storm initiation location.
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Smith, Craig M., Darko Koračin und Kristian Horvath. „Day-Ahead Predictability of Complex Terrain Flows for Wind Resource Production: A Case Study of the Washoe Zephyr“. Weather and Forecasting 29, Nr. 6 (01.12.2014): 1343–55. http://dx.doi.org/10.1175/waf-d-14-00021.1.
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Abstract A detailed description of the meteorological conditions of the Washoe Valley (Nevada) and simulations that examine the predictability of the westerly high wind event known as the Washoe Zephyr are presented. Numerical weather model prediction skill is computed for day-ahead (24–48 h) forecasts of wind speed at a meteorological tower on the Virginia Hills range relative to a persistence forecast based on a seasonal climatology constructed of hourly mean observations. The model predictions are shown to be more skillful than a climatology based on seasonal and hourly means during winter and less skillful than the seasonal-hourly climatology (SHC) during summer. Overall skill of the forecasted winds tends to increase with finer horizontal grid spacing. Phase errors compose the largest component of the error decomposition and large phase errors are associated with the onset and decay of the diurnally forced Washoe Zephyr during summer and synoptically forced high wind events and valley rotors during winter. The correlation coefficient between forecasts and observations for all forecast horizontal grid spacings considered is shown to depend roughly linearly on the ratio of the integrated power spectral density in the synoptic band to the integrated power spectral density in the combined diurnal and subdiurnal band.
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Mahale, Vivek N., Jerald A. Brotzge und Howard B. Bluestein. „An Analysis of Vortices Embedded within a Quasi-Linear Convective System Using X-Band Polarimetric Radar“. Weather and Forecasting 27, Nr. 6 (01.12.2012): 1520–37. http://dx.doi.org/10.1175/waf-d-11-00135.1.
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Abstract On 2 April 2010, a developing quasi-linear convective system (QLCS) moved rapidly northeastward through central Oklahoma spawning at least three intense, mesoscale vortices. At least two of these vortices caused damage rated as category 0 to 1 on the enhanced Fujita scale (EF0–EF1) in and near the town of Rush Springs. Two radar networks—the National Weather Service Weather Surveillance Radar-1988 Doppler network (WSR-88D) and the Engineering Research Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) radar network—collected high spatial and temporal resolution data of the event. This study is an in-depth polarimetric analysis of mesovortices within a QLCS. In this case study, the storm development and evolution of the QLCS mesovortices are examined. Significant findings include the following: 1) The damage in Rush Springs was caused by a combination of the fast translation speed and the embedded circulations associated with QLCS vortices. The vortices’ relative winds nearly negated the storm motion to the left of the vortex, but doubled the ground-relative wind to the right of the vortex. 2) A significant differential reflectivity (ZDR) arc developed along the forward flank of the first vortex. The ZDR arc propagated northeastward along the QLCS with the development of each new vortex. 3) A minimum in the copolar correlation coefficient (ρhv) in the center of the strongest vortex was observed, indicating the likely existence of a polarimetric tornado debris signature (TDS). A secondary ρhv minimum also was found just to the right of the vortex center, possibly associated with lofted debris from straight-line winds.
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Baxter, Martin A., und Philip N. Schumacher. „Distribution of Single-Banded Snowfall in Central U.S. Cyclones“. Weather and Forecasting 32, Nr. 2 (06.03.2017): 533–54. http://dx.doi.org/10.1175/waf-d-16-0154.1.
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Abstract A climatology of single-banded snowfall in the central United States and the variability of processes at work in its formation are presented. Ninety-eight snowbands are identified in association with 66 cyclones over 5 yr spanning the winters from 2006/07 through 2010/11. An additional 38 cyclones featured nonbanded snowfall exceeding 4 in. (10.2 cm). Nearly twice as many bands were observed to the northeast of the surface low than to the northwest. Over each snowband’s life cycle, the median (mean) snowband lasted 4.0 (5.2) h, was 42 (45) km wide, 388 (428) km long, and had an aspect ratio of 10.2 (10.8). A common appearance exists for snowbands in different large-scale flow regimes and locations relative to the surface cyclone. The median snowband elongates during the first half of its life span, with its width remaining constant. During the second half of the median snowband’s life span, the length and width contract. Composite analysis of the synoptic and broad mesoscale environments that snowbands form in illustrates that the juxtaposition of the ingredients necessary for snowbands are similar no matter which quadrant of the surface low the band is located in, indicating that the synoptic-scale flow determines where these ingredients are organized with respect to the cyclone. The frequency of banded snowfall within each northern quadrant of the surface low, the typical snowband characteristics and their evolution, and the patterns that give rise to snowbands documented by this work can all prove useful to forecasters tasked with maintaining situational awareness in the presence of many solutions provided by ensemble numerical weather prediction.
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Jiang, Jun, Wei Yan, Shuo Ma, Yangyang Jie, Xiarong Zhang, Shensen Hu, Lei Fan und Linyu Xia. „Three Cases of a New Multichannel Threshold Technique to Detect Fog/Low Stratus during Nighttime Using SNPP Data“. Weather and Forecasting 30, Nr. 6 (01.12.2015): 1763–80. http://dx.doi.org/10.1175/waf-d-15-0050.1.
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Abstract The day–night band (DNB) low-light-level visible sensor, mounted on the Suomi–National Polar-Orbiting Partnership (SNPP) satellite, can measure visible radiances from the earth and atmosphere (solar/lunar reflection, and natural/anthropogenic nighttime light emissions) during both day and night and can achieve unprecedented nighttime low-light-level imaging with its accurate radiometric calibration and fine spatiotemporal resolution. Based on the good characteristics of DNB, a multichannel threshold (MCT) algorithm combining DNB with other Visible–Infrared Imager–Radiometer Suite (VIIRS) channels is proposed to monitor nighttime fog/low stratus. Through a gradual separation of the underlying surface (land, vegetation, water bodies, and city lights), snow, and high/medium clouds, a fog/low-stratus region can ultimately be extracted by the algorithm. Then, the algorithmic feasibility is verified by three typical cases of heavy fog/low stratus in China. The experimental results demonstrate that the outcomes of the MCT algorithm approximately coincide with the ground-measured results. Furthermore, the MCT algorithm shows promise for nighttime fog/low-stratus detection in some example cases with about a 0.84 average probability of detection (POD), a 0.73 average critical success index (CSI), and a 0.15 average false alarm ratio (FAR), which reveals some improvement over the conventional dual-channel difference (DCD) algorithm.
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Van Den Broeke, Matthew S., Dana M. Tobin und Matthew R. Kumjian. „Polarimetric Radar Observations of Precipitation Type and Rate from the 2–3 March 2014 Winter Storm in Oklahoma and Arkansas“. Weather and Forecasting 31, Nr. 4 (07.07.2016): 1179–96. http://dx.doi.org/10.1175/waf-d-16-0011.1.
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Abstract A powerful winter storm affected the south-central United States in early March 2014, accompanied by elevated convective cells with hail and high rates of sleet, freezing rain, and snow. During portions of the event the thermal profile exhibited a shallow surface cold layer and warm, unstable air aloft. Precipitation falling into the cold layer refroze into ice pellets and was accompanied by a polarimetric refreezing signature and numerous crowdsourced surface ice pellet reports. Quasi-vertical profiles of the polarimetric variables indicated an enhanced reflectivity factor ZHH below the melting layer bright band and enhanced low-level differential reflectivity ZDR values coincident with surface ice pellet reports. Freezing rain rate was highest in areas with high ZHH and specific differential phase KDP values at low levels. High snow rates were most closely associated with 1- and 1.5-km ZHH values, though KDP and ZDR also appeared to show some ability to distinguish high snow rate. Numerous elevated convective cells contained rotating updrafts that appeared to contribute to storm longevity and intensity. Most contained well-defined ZDR maxima or columns and relatively high base-scan ZDR values. Several contained polarimetric signatures consistent with heavy mixed-phase precipitation and hail; social media reports indicated that large hail was produced by some of the storms.
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Campbell, Leah S., und W. James Steenburgh. „Finescale Orographic Precipitation Variability and Gap-Filling Radar Potential in Little Cottonwood Canyon, Utah“. Weather and Forecasting 29, Nr. 4 (22.07.2014): 912–35. http://dx.doi.org/10.1175/waf-d-13-00129.1.
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Abstract Finescale variations in orographic precipitation pose a major challenge for weather prediction, winter road maintenance, and avalanche forecasting and mitigation in mountainous regions. In this investigation, ground-based X-band radar observations collected during intensive observing period 6 (IOP6) of the Storm Chasing Utah Style Study (SCHUSS) are used to provide an example of these variations during a winter storm in the Wasatch Mountains of northern Utah. Emphasis is placed on precipitation features in and around Little Cottonwood Canyon (LCC), which cuts orthogonally eastward into the central Wasatch Mountains. Precipitation during the weakly stratified prefrontal storm stage featured a wavelike barrier-scale reflectivity maximum over the Wasatch Crest and upper LCC that extended weakly westward along the transverse ridges flanking LCC. This precipitation pattern appeared to reflect a veering wind profile, with southwesterly flow over the transverse ridges but cross-barrier westerly flow farther aloft. Sublimation within dry subcloud air further diminished low-level radar reflectivities over lower LCC. In contrast, the cold-frontal stage was associated with stronger reflectivities over lower LCC and the adjoining north- to northwest-facing canyon wall, consistent with shallow, northwesterly upslope flow. These results highlight the finescale precipitation variations that can occur during winter storms in complex terrain and demonstrate the potential for improved analysis and forecasting of precipitation in LCC using a gap-filling radar.
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Snyder, Jeffrey C., und Howard B. Bluestein. „Some Considerations for the Use of High-Resolution Mobile Radar Data in Tornado Intensity Determination“. Weather and Forecasting 29, Nr. 4 (22.07.2014): 799–827. http://dx.doi.org/10.1175/waf-d-14-00026.1.
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Abstract The increasing number of mobile Doppler radars used in field campaigns across the central United States has led to an increasing number of high-resolution radar datasets of strong tornadoes. There are more than a few instances in which the radar-measured radial velocities substantially exceed the estimated wind speeds associated with the enhanced Fujita (EF) scale rating assigned to a particular tornado. It is imperative, however, to understand what the radar data represent if one wants to compare radar observations to damage-based EF-scale estimates. A violent tornado observed by the rapid-scan, X-band, polarimetric mobile radar (RaXPol) on 31 May 2013 contained radar-relative radial velocities exceeding 135 m s−1 in rural areas essentially devoid of structures from which damage ratings can be made. This case, along with others, serves as an excellent example of some of the complications that arise when comparing radar-estimated velocities with the criteria established in the EF scale. In addition, it is shown that data from polarimetric radars should reduce the variance of radar-relative radial velocity estimates within the debris field compared to data from single-polarization radars. Polarimetric radars can also be used to retrieve differential velocity, large magnitudes of which are spatially associated with large spectrum widths inside the polarimetric tornado debris signature in several datasets of intense tornadoes sampled by RaXPol.
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Min, Ki-Hong, Sunhee Choo, Daehyung Lee und Gyuwon Lee. „Evaluation of WRF Cloud Microphysics Schemes Using Radar Observations“. Weather and Forecasting 30, Nr. 6 (19.11.2015): 1571–89. http://dx.doi.org/10.1175/waf-d-14-00095.1.
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Abstract The Korea Meteorological Administration (KMA) implemented a 10-yr project to develop its own global model (GM) by 2020. To reflect the complex topography and unique weather characteristics of the Korean Peninsula, a high-resolution model with accurate physics and input data is required. The WRF single-moment 6-class microphysics scheme (WSM6) and WRF double-moment 6-class microphysics scheme (WDM6) that will be implemented in the Korea GM (KGM) are evaluated. Comparisons of the contoured frequency by altitude diagram (CFAD), time–height cross sections, and vertical profiles of hydrometeors are utilized to assess the two schemes in simulating summer monsoon and convective precipitation cases over the Korean Peninsula during 2011. The results show that WSM6 and WDM6 overestimate the height of the melting level and bright band as compared to radar observations. However, the accuracy of WDM6 is in better agreement with radar observations. This is attributed to the difference in the sedimentation process simulated by the additional second-moment total number concentrations of liquid-phase particles in WDM6. WDM6 creates larger raindrops and higher relative humidity beneath the melting layer, allowing the scheme to simulate a more realistic reflectivity profile than WSM6 for the summer monsoon case. However, for the convective case, both schemes underestimate the precipitation and there is resolution dependence in the WRF Model’s ability to simulate convective precipitation.
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Kuster, Charles M., Pamela L. Heinselman und Marcus Austin. „31 May 2013 El Reno Tornadoes: Advantages of Rapid-Scan Phased-Array Radar Data from a Warning Forecaster’s Perspective*“. Weather and Forecasting 30, Nr. 4 (01.08.2015): 933–56. http://dx.doi.org/10.1175/waf-d-14-00142.1.
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Abstract On 31 May 2013, a supercell produced a tornado rated as 3 on the enhanced Fujita scale (EF3) near El Reno, Oklahoma, which was sampled by the S-band phased-array radar (PAR) at the National Weather Radar Testbed in Norman, Oklahoma. Collaboration with the forecaster who issued tornado warnings for the El Reno supercell during real-time operations focused the analysis on critical radar signatures frequently assessed during warning operations. The wealth of real-world experience provided by the forecaster, along with the quantitative analysis, highlighted differences between rapid-scan PAR data and the Weather Surveillance Radar-1988 Doppler located near Oklahoma City, Oklahoma (KTLX), within the context of forecast challenges faced on 31 May 2013. The comparison revealed that the 70-s PAR data proved most advantageous to the forecaster’s situational awareness in instances of rapid storm organization, sudden mesocyclone intensification, and abrupt, short-term changes in tornado motion. Situations where PAR data were most advantageous in the depiction of storm-scale processes included 1) rapid variations in mesocyclone intensity and associated changes in inflow magnitude; 2) imminent radar-indicated development of the short-lived (EF0) Calumet, Oklahoma, and long-lived (EF3) El Reno tornadoes; and 3) precise location and motion of the tornado circulation. As a result, it is surmised that rapid-scan volumetric radar data in cases like this would augment a forecaster’s ability to observe rapidly evolving storm features and deliver timely, life-saving information to the general public.
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Kuster, Charles M., Pamela L. Heinselman und Terry J. Schuur. „Rapid-Update Radar Observations of Downbursts Occurring within an Intense Multicell Thunderstorm on 14 June 2011“. Weather and Forecasting 31, Nr. 3 (01.06.2016): 827–51. http://dx.doi.org/10.1175/waf-d-15-0081.1.
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Abstract On 14 June 2011, an intense multicell thunderstorm produced one nonsevere and three severe downbursts within 35 km of the rapid-update, S-band phased array radar (PAR) at the National Weather Radar Testbed in Norman, Oklahoma, and the nearby polarimetric research Weather Surveillance Radar 1988-Doppler (KOUN). Data collected from these radars provided the opportunity to conduct a quantitative analysis of downburst precursor signature evolution depicted by 1-min PAR data and the associated evolution of differential reflectivity ZDR depicted by 5-min KOUN data. Precursors analyzed included descent of the reflectivity core, evolution of the magnitude and size of midlevel convergence (i.e., number of bins), and descending “troughs” of ZDR. The four downbursts exhibited midlevel convergence that rapidly increased to peak magnitude as the reflectivity core (65-dBZ isosurface) bottom and top descended. The ZDR troughs seen in the 5-min KOUN data appeared to descend along with the core bottom. Midlevel convergence size increased to a peak value and decreased as the reflectivity core descended in the three severe downbursts. In contrast, midlevel convergence size exhibited little change in the nonsevere downburst. The time scale of trends seen in the PAR data was 11 min or less and happened several minutes prior to each downburst’s maximum intensity. These results point to the importance of 1-min volumetric data in effectively resolving the evolution of downburst precursors, which could be beneficial to forecast operations.
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van der Linden, Roderick, Andreas H. Fink, Joaquim G. Pinto und Tan Phan-Van. „The Dynamics of an Extreme Precipitation Event in Northeastern Vietnam in 2015 and Its Predictability in the ECMWF Ensemble Prediction System“. Weather and Forecasting 32, Nr. 3 (27.04.2017): 1041–56. http://dx.doi.org/10.1175/waf-d-16-0142.1.
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Abstract A record-breaking rainfall event occurred in northeastern Vietnam in late July–early August 2015. The coastal region in Quang Ninh Province was hit severely, with station rainfall sums in the range of 1000–1500 mm. The heavy rainfall led to flooding and landslides, which resulted in an estimated economic loss of $108 million (U.S. dollars) and 32 fatalities. Using a multitude of data sources and ECMWF ensemble forecasts, the synoptic–dynamic development and practical predictability of the event is investigated in detail for the 4-day period from 1200 UTC 25 July to 1200 UTC 29 July 2015, during which the major portion of the rainfall was observed. A slowly moving upper-level subtropical trough and the associated surface low in the northern Gulf of Tonkin promoted sustained moisture convergence and convection over northeastern Vietnam. The humidity was advected in a moisture transport band lying across the Indochina Peninsula and emanating from a tropical storm over the Bay of Bengal. Analyses of the ECMWF ensemble forecasts clearly showed a sudden emergence of the predictability of the extreme event at lead times of 3 days that was associated with the correct forecasts of the intensity and location of the subtropical trough in the 51 ensemble members. Thus, the Quang Ninh event is a good example in which the predictability of tropical convection arises from large-scale synoptic forcing; in the present case it was due to a tropical–extratropical interaction that has not been documented before for the region and season.
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Saslo, Seth, und Steven J. Greybush. „Prediction of Lake-Effect Snow Using Convection-Allowing Ensemble Forecasts and Regional Data Assimilation“. Weather and Forecasting 32, Nr. 5 (15.09.2017): 1727–44. http://dx.doi.org/10.1175/waf-d-16-0206.1.
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Abstract Lake-effect snow (LES) is a cold-season mesoscale convective phenomenon that can lead to significant snowfall rates and accumulations in the Great Lakes region of the United States. While limited-area numerical weather prediction models have shown skill in prediction of warm-season convective storms, forecasting the sharp nature of LES precipitation timing, intensity, and location is difficult because of model error and initial and boundary condition uncertainties. Ensemble forecasting can incorporate and quantify some sources of forecast error, but ensemble design must be considered. This study examines the relative contributions of forecast uncertainties to LES forecast error using a regional convection-allowing data assimilation and ensemble prediction system. Ensembles are developed using various methods of perturbations to simulate a long-lived and high-precipitation LES event in December 2013, and forecast performance is evaluated using observations including those from the Ontario Winter Lake-Effect Systems (OWLeS) campaign. Model lateral boundary conditions corresponding to weather conditions beyond the Great Lakes region play an influential role in LES precipitation forecasts and their uncertainty, as evidenced by ensemble spread, particularly at lead times beyond one day. A strong forecast dependence on regional initial conditions was shown using data assimilation. This sensitivity impacts the timing and intensity of predicted precipitation, as well as band location and orientation assessed with an object-based verification approach, giving insight into the time scales of practical predictability of LES. Overall, an assimilation-cycling convection-allowing ensemble prediction system could improve future lake-effect snow precipitation forecasts and analyses and can help quantify and understand sources of forecast uncertainty.
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Witt, Arthur, Donald W. Burgess, Anton Seimon, John T. Allen, Jeffrey C. Snyder und Howard B. Bluestein. „Rapid-Scan Radar Observations of an Oklahoma Tornadic Hailstorm Producing Giant Hail“. Weather and Forecasting 33, Nr. 5 (19.09.2018): 1263–82. http://dx.doi.org/10.1175/waf-d-18-0003.1.
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Abstract Rapid-scan radar observations of a supercell that produced near-record size hail in Oklahoma are examined. Data from the National Weather Radar Testbed Phased Array Radar (PAR) in Norman, Oklahoma, are used to study the overall character and evolution of the storm. Data from the nearby polarimetric KOUN WSR-88D and rapid-scanning X-band polarimetric (RaXPol) mobile radar are used to study the evolution of low- to midaltitude dual-polarization parameters above two locations where giant hailstones up to 16 cm in diameter were observed. The PAR observation of the supercell’s maximum storm-top divergent outflow is similar to the strongest previously documented value. The storm’s mesocyclone rotational velocity at midaltitudes reached a maximum that is more than double the median value for similar observations from other storms producing giant hail. For the two storm-relative areas where giant hail was observed, noteworthy findings include 1) the giant hail occurred outside the main precipitation core, in areas with low-altitude reflectivities of 40–50 dBZ; 2) the giant hail was associated with dual-polarization signatures consistent with past observations of large hail at 10-cm wavelength, namely, low ZDR, low ρHV, and low KDP; 3) the giant hail fell along both the northeast and southwest edges of the primary updraft at ranges of 6–10 km from the updraft center; and 4) with the exception of one isolated report, the giant hail fell to the northeast and northwest of the large tornado and the parent mesocyclone.
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Ribeiro, Bruno Z., Luiz A. T. Machado, Joao H. Huamán Ch., Thiago S. Biscaro, Edmilson D. Freitas, Kathryn W. Mozer und Steven J. Goodman. „An Evaluation of the GOES-16 Rapid Scan for Nowcasting in Southeastern Brazil: Analysis of a Severe Hailstorm Case“. Weather and Forecasting 34, Nr. 6 (14.11.2019): 1829–48. http://dx.doi.org/10.1175/waf-d-19-0070.1.
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Abstract The GOES-16 mesoscale domain sector (MDS) scans with 1-min intervals are used in this study to analyze a severe thunderstorm case that occurred in southeastern Brazil. The main objective is to evaluate the GOES-16 MDS rapid scans against the operational full-disk scans with lower temporal resolution for nowcasting. Data from a C-band radar, observed sounding, and a ground-based lightning network are also used in the analysis. A group of thunderstorms formed in the afternoon of 29 November 2017 in an environment of moderate convective available potential energy (CAPE) and deep-layer shear. The storms presented supercell characteristics and intense lightning activity with peak rates in excess of 150 flashes per 5 min. The satellite-derived trends with 1-min interval were skillful in detecting thunderstorm intensification, mainly in the developing stage. The decrease in cloud-top 10.35-μm brightness temperature was accompanied by increases in ice mass flux, concentration of small ice particles at cloud top, and storm depth. In the mature stage, there is no evident trend in the satellite-derived parameters that could indicate storm intensification, but the cluster area expands suggesting cloud-top divergence. The 1-min rapid scans indicate greater lead time to severe weather relative to 10- and 15-min-resolution imagery, but also presented numerous false alarms (indication of severe weather but no occurrence) due to oscillations in the satellite-derived parameters. The parameters calculated every 5 min presented better skill than 10 and 15 min and fewer false alarms than 1 min.
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Schultz, David M., und W. James Steenburgh. „Nonclassic Evolution of a Cold-Frontal System across the Western United States during the Intermountain Precipitation Experiment (IPEX)“. Weather and Forecasting 35, Nr. 1 (01.02.2020): 255–71. http://dx.doi.org/10.1175/waf-d-19-0166.1.
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Abstract A cold-frontal passage through northern Utah was studied using observations collected during intensive observing period 4 of the Intermountain Precipitation Experiment (IPEX) on 14–15 February 2000. To illustrate some of its nonclassic characteristics, its origins are considered. The front developed following the landfall of two surface features on the Pacific coast (hereafter, the cold-frontal system). The first feature was a surface pressure trough and wind shift associated with a band of precipitation and rope cloud with little, if any, surface baroclinicity. The second, which made landfall 4 h later, was a wind shift associated with weaker precipitation that possessed a weak temperature drop at landfall (1°C in 9 h), but developed a stronger temperature drop as it moved inland over central California (4°–6°C in 9 h). As the first feature moved into the Great Basin, surface temperatures ahead of the trough increased due to downslope flow and daytime heating, whereas temperatures behind the trough decreased as precipitation cooled the near-surface air. Coupled with confluence in the lee of the Sierra Nevada, this trough developed into the principal baroclinic zone of the cold-frontal system (8°C in less than an hour), whereas the temperature drop with the second feature weakened further. The motion of the surface pressure trough was faster than the posttrough surface winds and was tied to the motion of the short-wave trough aloft. This case, along with previously published cases in the Intermountain West, challenges the traditional conceptual model of cold-frontal terminology, structure, and evolution.
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Bankert, Richard L., Jeremy E. Solbrig, Thomas F. Lee und Steven D. Miller. „Automated Lightning Flash Detection in Nighttime Visible Satellite Data“. Weather and Forecasting 26, Nr. 3 (01.06.2011): 399–408. http://dx.doi.org/10.1175/waf-d-10-05002.1.
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Abstract The Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) nighttime visible channel was designed to detect earth–atmosphere features under conditions of low illumination (e.g., near the solar terminator or via moonlight reflection). However, this sensor also detects visible light emissions from various terrestrial sources (both natural and anthropogenic), including lightning-illuminated thunderstorm tops. This research presents an automated technique for objectively identifying and enhancing the bright steaks associated with lightning flashes, even in the presence of lunar illumination, derived from OLS imagery. A line-directional filter is applied to the data in order to identify lightning strike features and an associated false color imagery product enhances this information while minimizing false alarms. Comparisons of this satellite product to U.S. National Lightning Detection Network (NLDN) data in one case as well as to a lightning mapping array (LMA) in another case demonstrate general consistency to within the expected limits of detection. This algorithm is potentially useful in either finding or confirming electrically active storms anywhere on the globe, particularly those occurring in remote areas where surface-based observations are not available. Additionally, the OLS nighttime visible sensor provides heritage data for examining the potential usefulness of the Visible-Infrared Imager-Radiometer Suite (VIIRS) Day/Night Band (DNB) on future satellites including the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP). The VIIRS DNB will offer several improvements to the legacy OLS nighttime visible channel, including full calibration and collocation with 21 narrowband spectral channels.
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Heinselman, Pamela L., Daphne S. LaDue und Heather Lazrus. „Exploring Impacts of Rapid-Scan Radar Data on NWS Warning Decisions“. Weather and Forecasting 27, Nr. 4 (01.08.2012): 1031–44. http://dx.doi.org/10.1175/waf-d-11-00145.1.
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Abstract Rapid-scan weather radars, such as the S-band phased array radar at the National Weather Radar Testbed in Norman, Oklahoma, improve precision in the depiction of severe storm processes. To explore potential impacts of such data on forecaster warning decision making, 12 National Weather Service forecasters participated in a preliminary study with two control conditions: 1) when radar scan time was similar to volume coverage pattern 12 (4.5 min) and 2) when radar scan time was faster (43 s). Under these control conditions, forecasters were paired and worked a tropical tornadic supercell case. Their decision processes were observed and audio was recorded, interactions with data displays were video recorded, and the products were archived. A debriefing was conducted with each of the six teams independently and jointly, to ascertain the forecaster decision-making process. Analysis of these data revealed that teams examining the same data sometimes came to different conclusions about whether and when to warn. Six factors contributing toward these differences were identified: 1) experience, 2) conceptual models, 3) confidence, 4) tolerance of possibly missing a tornado occurrence, 5) perceived threats, and 6) software issues. The three 43-s teams issued six warnings: three verified, two did not verify, and one event was missed. Warning lead times were the following: tornado, 18.6 and 11.5 min, and severe, 6 min. The three tornado warnings issued by the three 4.5-min teams verified, though warning lead times were shorter: 4.6 and 0 min (two teams). In this case, use of rapid-scan data showed the potential to extend warning lead time and improve forecasters’ confidence, compared to standard operations.
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Kalina, Evan A., Katja Friedrich, Brian C. Motta, Wiebke Deierling, Geoffrey T. Stano und Nezette N. Rydell. „Colorado Plowable Hailstorms: Synoptic Weather, Radar, and Lightning Characteristics“. Weather and Forecasting 31, Nr. 2 (01.04.2016): 663–93. http://dx.doi.org/10.1175/waf-d-15-0037.1.
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Abstract Synoptic weather, S-band dual-polarization radar, and total lightning observations are analyzed from four thunderstorms that produced “plowable” hail accumulations of 15–60 cm in localized areas of the Colorado Front Range. Results indicate that moist, relatively slow (5–15 m s−1) southwesterly-to-westerly flow at 500 hPa and postfrontal low-level upslope flow, with 2-m dewpoint temperatures of 11°–19°C at 1200 LST, were present on each plowable hail day. This pattern resulted in column-integrated precipitable water values that were 132%–184% of the monthly means and freezing-level heights that were 100–700 m higher than average. Radar data indicate that between one and three maxima in reflectivity Z (68–75 dBZ) and 50-dBZ echo-top height (11–15 km MSL) occurred over the lifetime of each hailstorm. These maxima, which imply an enhancement in updraft strength, resulted in increased graupel and hail production and accumulating hail at the surface within 30 min of the highest echo tops. The hail core had Z ~ 70 dBZ, differential reflectivity ZDR from 0 to −4 dB, and correlation coefficient ρHV of 0.80–0.95. Time–height plots reveal that these minima in ZDR and ρHV gradually descended to the surface after originating at heights of 6–10 km MSL ~15–60 min prior to accumulating hailfall. Hail accumulations estimated from the radar data pinpoint the times and locations of plowable hail, with depths greater than 5 cm collocated with the plowable hail reports. Three of the four hail events were accompanied by lightning flash rates near the maximum observed thus far within the thunderstorm.
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Griffin, Erica M., Terry J. Schuur, Alexander V. Ryzhkov, Heather D. Reeves und Joseph C. Picca. „A Polarimetric and Microphysical Investigation of the Northeast Blizzard of 8–9 February 2013“. Weather and Forecasting 29, Nr. 6 (01.12.2014): 1271–94. http://dx.doi.org/10.1175/waf-d-14-00056.1.
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Abstract On 8–9 February 2013, the northeastern United States experienced a historic winter weather event ranking among the top five worst blizzards in the region. Heavy snowfall and blizzard conditions occurred from northern New Jersey, inland to New York, and northward through Maine. Storm-total snow accumulations of 30–61 cm were common, with maximum accumulations up to 102 cm and snowfall rates exceeding 15 cm h−1. Dual-polarization radar measurements collected for this winter event provide valuable insights into storm microphysical processes. In this study, polarimetric data from the Weather Surveillance Radar-1988 Doppler (WSR-88D) in Upton, New York (KOKX), are investigated alongside thermodynamic analyses from the 13-km Rapid Refresh model and surface precipitation type observations from both Meteorological Phenomena Identification Near the Ground (mPING) and the National Weather Service (NWS) Forecast Office in Upton, New York, for interpretation of polarimetric signatures. The storm exhibited unique polarimetric signatures, some of which have never before been documented for a winter system. Reflectivity values were unusually large, reaching magnitudes >50 dBZ in shallow regions of heavy wet snow near the surface. The 0°C transition line was exceptionally distinct in the polarimetric imagery, providing detail that was often unmatched by the numerical model output. Other features include differential attenuation of magnitudes typical of melting hail, depolarization streaks that provide evidence of electrification, nonuniform beamfilling, a “snow flare” signature, and localized downward excursions of the melting-layer bright band collocated with observed transitions in surface precipitation types. In agreement with previous studies, widespread elevated depositional growth layers, located at temperatures near the model-predicted −15°C isotherm, appear to be correlated with increased snowfall and large reflectivity factors ZH near the surface.
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Neupane, Hari Krishna, und Narayan Prasad Adhikari. „Structural, Electronic and Magnetic Properties of Defected Water Adsorbed Single-Layer MoS2“. Journal of Institute of Science and Technology 26, Nr. 1 (17.06.2021): 43–50. http://dx.doi.org/10.3126/jist.v26i1.37817.
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Water adsorbed in MoS2 (wad-MoS2), 1S atom vacancy defect in wad-MoS2 (1S-wad-MoS2), 2S atoms vacancy defects in wad-MoS2 (2S-wad-MoS2), and 1Mo atom vacancy defect in wad-MoS2 (Mo-wad-MoS2) materials were constructed, and their structural, electronic, and magnetic properties were studied by spin-polarized density functional theory (DFT) based first-principles calculations. The wad-MoS2, 1S-wad-MoS2, 2S-wad-MoS2, and Mo-wad-MoS2 materials were found stable. From band structure calculations, wad-MoS2, 1S-wad-MoS2 and 2S-wad-MoS2 materials open energy bandgap of values 1.19 eV, 0.65 eV and 0.38 eV respectively. Also, it was found that the conductivity strength of the material increases with an increase in the concentration of S atom vacancy defects in the structure. On the other hand, the Mo-wad-MoS2 material has metallic properties because energy bands of electrons crossed the Fermi energy level in the band structure. For the investigation of magnetic properties, the density of states (DoS) and partial density of states (PDoS) calculations were used and found that wad-MoS2, 1S-wad-MoS2, and 2S-wad-MoS2 are non-magnetic materials, while Mo-wad-MoS2 is a magnetic material. The total magnetic moment of Mo-wad-MoS2 has a value of 2.66 µB/cell, due to the arrangement of unpaired up-spin and down-spin of electrons in 3s & 3p orbitals of S atoms; and 4p, 4d & 5s orbitals of Mo atoms in the material.
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Kim, Dong-Hyun, Soon-Soo Oh, Kyeong-Sik Min und Suk-Youb Kang. „X-Band 6-Way Waveguide Power Divider Using Inductive Post“. Journal of Korean Institute of Electromagnetic Engineering and Science 21, Nr. 4 (30.04.2010): 417–26. http://dx.doi.org/10.5515/kjkiees.2010.21.4.417.
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Shiohara, M., WS el-Deiry, M. Wada, T. Nakamaki, S. Takeuchi, R. Yang, DL Chen, B. Vogelstein und HP Koeffler. „Absence of WAF1 mutations in a variety of human malignancies“. Blood 84, Nr. 11 (01.12.1994): 3781–84. http://dx.doi.org/10.1182/blood.v84.11.3781.bloodjournal84113781.
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A newly cloned gene named wild-type p53-activated fragment 1 (WAF1; also known as p21, Pic-1, Cip-1, or SDI1) is directly regulated by p53 and can itself suppress tumor cell growth in culture. Induction of expression of WAF1 may be an important means by which cells with DNA injury arrest their growth to repair DNA or undergo apoptosis. Based on the hypothesis that mutations of this gene may play a role in carcinogenesis, we have studied 351 DNAs from 14 kinds of malignancies, as well as 36 human transformed cell lines, for alterations of WAF1 gene by single-strand conformation polymorphism analysis of polymerase chain reaction amplification of the DNA coding region of the WAF1 gene. No abnormal band shifts of WAF1 were noted in any of the samples or cell lines, but three major variants in exons 2 and 3 of the gene were found that are consistent with the existence of two different DNA polymorphisms. Sequence analysis of the amplified products producing these three variants in each exon from normal DNAs confirmed the presence of the polymorphisms in the WAF1 gene. Of 290 selected tumor samples previously evaluated for p53 mutations by single-strand conformation polymorphism, 90% had no detectable p53 alterations. In summary, mutations within the coding portion of the WAF1 gene were undetectable in a large series of human tumors, many of which had a normal p53 gene. This suggests that WAF1 alterations are generally caused indirectly, through p53 mutations rather than through intragenic mutation of the WAF1 itself.
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Giuffrida, Sergio, Antonio Cupane und Grazia Cottone. „“Water Association” Band in Saccharide Amorphous Matrices: Role of Residual Water on Bioprotection“. International Journal of Molecular Sciences 22, Nr. 5 (02.03.2021): 2496. http://dx.doi.org/10.3390/ijms22052496.
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Saccharides protect biostructures against adverse environmental conditions mainly by preventing large scale motions leading to unfolding. The efficiency of this molecular mechanism, which is higher in trehalose with respect to other sugars, strongly depends on hydration and sugar/protein ratio. Here we report an Infrared Spectroscopy study on dry amorphous matrices of the disaccharides trehalose, maltose, sucrose and lactose, and the trisaccharide raffinose. Samples with and without embedded protein (Myoglobin) are investigated at different sugar/protein ratios, and compared. To inspect matrix properties we analyse the Water Association Band (WAB), and carefully decompose it into sub-bands, since their relative population has been shown to effectively probe water structure and dynamics in different matrices. In this work the analysis is extended to investigate the structure of protein-sugar-water samples, for the first time. Results show that several classes of water molecules can be identified in the protein and sugar environment and that their relative population is dependent on the type of sugar and, most important, on the sugar/protein ratio. This gives relevant information on how the molecular interplay between residual waters, sugar and protein molecules affect the biopreserving properties of saccharides matrices.
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Yoshimoto, T., M. Naruse, Z. Zeng, T. Nishikawa, T. Kasajima, H. Toma, S. Yamamori et al. „The relatively high frequency of p53 gene mutations in multiple and malignant phaeochromocytomas“. Journal of Endocrinology 159, Nr. 2 (01.11.1998): 247–55. http://dx.doi.org/10.1677/joe.0.1590247.
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To explore the clinical significance of p53 in the pathogenesis of adrenal neoplasms, we investigated the incidence of p53 gene mutations in functioning human adrenal tumours using the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) technique to screen p53 exons 4 to 9. We examined 29 adrenocortical adenomas (primary aldosteronism, n=17; Cushing's syndrome, n=12, all benign), and 33 phaeochromocytomas (benign solitary, n=18; benign multiple, n=5; malignant, n=10) in Japanese and Chinese patients. PCR-SSCP did not show any abnormal band-shifts in any of the adrenocortical adenoma and benign solitary phaeochromocytoma tissues. In contrast, six phaeochromocytoma tissues (two cases benign multiple, four cases malignant) showed PCR-SSCP band-shifts. Subsequent DNA sequencing analysis of the shifted bands revealed six cases with nine mutations or intronic sequence alterations: three cases contained sequence alterations within intronic regions, three cases with silent mutation (sequence alteration in codon without amino acid alteration), and three cases contained missense mutations (one case each in exons 5, 6 and 9). Immunohistochemical staining demonstrated that two of three cases with missense mutations and one case with an intronic sequence alteration over-expressed p53 protein in tumour cell nuclei. We observed no association between p53 gene mutation and p21/WAF1/Cip-1 expression. The relatively high incidence of p53 gene mutations or intronic sequence alteration in multiple and malignant phaeochromocytomas, but not in benign solitary cases, suggests that p53 mutation could play some role in the pathogenesis of multiple and/or malignant phaeochromocytomas.
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Ausaf, Asfund, Mohammad Zubair Khan, Muhammad Awais Javed und Ali Kashif Bashir. „WLAN Aware Cognitive Medium Access Control Protocol for IoT Applications“. Future Internet 12, Nr. 1 (11.01.2020): 11. http://dx.doi.org/10.3390/fi12010011.
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Internet of Things (IoT)-based devices consist of wireless sensor nodes that are battery-powered; thus, energy efficiency is a major issue. IEEE 802.15.4-compliant IoT devices operate in the unlicensed Industrial, Scientific, and Medical (ISM) band of 2.4 GHz and are subject to interference caused by high-powered IEEE 802.11-compliant Wireless Local Area Network (WLAN) users. This interference causes frequent packet drop and energy loss for IoT users. In this work, we propose a WLAN Aware Cognitive Medium Access Control (WAC-MAC) protocol for IoT users that uses techniques, such as energy detection based sensing, adaptive wake-up scheduling, and adaptive backoff, to reduce interference with the WSN and improve network lifetime of the IoT users. Results show that the proposed WAC-MAC achieves a higher packet reception rate and reduces the energy consumption of IoT nodes.
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Warford, Elisa. „The Joaquín Band: The History behind the Legend by Lori Lee Wilson“. Western American Literature 48, Nr. 4 (2014): 467–69. http://dx.doi.org/10.1353/wal.2014.0022.
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Kang, Bongmo, Sungjun Park, Wansik Kim, Juyoung Lee, Kichul Kim, Jeung Won Choi, Juman Park und Jinho Jeong. „Rectangular Waveguide-Based W-Band Eight-Way Radial Power Combiner“. Journal of Korean Institute of Electromagnetic Engineering and Science 33, Nr. 3 (März 2022): 181–89. http://dx.doi.org/10.5515/kjkiees.2021.33.3.181.
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Sabaghi, Masoud, Mohsen Dashtbayazi und Saeid Marjani. „Dynamic Hysteresis Band Fixed Frequency Current Control“. World Applied Programming 6, Nr. 1 (01.03.2016): 1–4. http://dx.doi.org/10.21828/wap-06-01-001.
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Kim, Ji-Han, Tae-Kyung Kim, Dong-Min Shin, Hyun-Wook Kim, Young-Boong Kim und Yun-Sang Choi. „Comparative effects of dry-aging and wet-aging on physicochemical properties and digestibility of Hanwoo beef“. Asian-Australasian Journal of Animal Sciences 33, Nr. 3 (01.03.2020): 501–5. http://dx.doi.org/10.5713/ajas.19.0031.
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Objective: The purpose of this study was to investigate the effects of aging methods (AM) i.e. dry-aging (DA) and wet-aging (WA) on the physicochemical properties and in vitro digestibility of proteins in beef short loin.Methods: Short loins (M. longissmus lumborum), were trimmed and boned-out on the fifth day postmortem, from a total of 18 Hanwoo, which were purchased from a commercial slaughterhouse. Short loins were separated randomly grouped into one of the three treatments: control, WA (1°C, 7 days), and DA (1°C, 0.5 m/s, 85% relative humidity [RH], 30 days).Results: Dry-aged beef (DAB) exhibited higher pH, water holding capacity (WHC), myofibrillar fragmentation index (MFI), and digestibility, however lower lightness, redness, and yellowness values, cooking loss, and shear force (SF), than those of wet-aged beef (WAB) (p<0.05). The myosin light chain band intensity of DAB was higher than that of control and WAB in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The in vitro digestibility of aged beef was highly (p<0.001) correlated to physicochemical properties except WHC. The correlation coefficient between AMs and WHC was higher than that between AM and SF (p<0.05) or MFI (p<0.001). A high correlation was observed between SF and MFI (p<0.001).Conclusion: Thus, we believe that DAB is more advantageous than WAB owing to its high digestibility and WHC and low SF.
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Kang, Bongmo, Wansik Kim, Juyoung Lee, Kichul Kim, Jaesoo Jung und Jinho Jeong. „W-Band 4-Way Waveguide Power Combiner Using Perpendicular Mode Conversion“. Journal of Korean Institute of Electromagnetic Engineering and Science 32, Nr. 4 (April 2021): 353–59. http://dx.doi.org/10.5515/kjkiees.2021.32.4.353.
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Parvin, Nargis, Moinur Rahman, Irana Tabassum Ananna und Md Saifur Rahman. „Fundamental Frequency Extraction by Utilizing Accumulated Power Spectrum based Weighted Autocorrelation Function in Noisy Speech“. International Journal of Information Technology and Computer Science 16, Nr. 3 (08.06.2024): 52–60. http://dx.doi.org/10.5815/ijitcs.2024.03.05.
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This research suggests an efficient idea that is better suited for speech processing applications for retrieving the accurate pitch from speech signal in noisy conditions. For this objective, we present a fundamental frequency extraction algorithm and that is tolerant to the non-stationary changes of the amplitude and frequency of the input signal. Moreover, we use an accumulated power spectrum instead of power spectrum, which uses the shorter sub-frames of the input signal to reduce the noise characteristics of the speech signals. To increase the accuracy of the fundamental frequency extraction we have concentrated on maintaining the speech harmonics in their original state and suppressing the noise elements involved in the noisy speech signal. The two stages that make up the suggested fundamental frequency extraction approach are producing the accumulated power spectrum of the speech signal and weighting it with the average magnitude difference function. As per the experiment results, the proposed technique appears to be better in noisy situations than other existing state-of-the-art methods such as Weighted Autocorrelation Function (WAF), PEFAC, and BaNa.
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Yunus Ahmad, Muhammad, Irwan Irwan, Ruhamah Ruhamah, Nurul Izatul Jannah, Ida Hasanah und Radja Fadlul Arabi. „Fenomena Korean Wave pada Kehidupan Mahasiswa di Kota Banda Aceh“. Jurnal Adabiya 26, Nr. 1 (13.02.2024): 110. http://dx.doi.org/10.22373/adabiya.v26i1.21626.
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This research discusses the phenomenon of the development of Korean culture among students in the city of Banda Aceh, and how students respond and view the phenomenon of Korean Wafe. The method used in this research is descriptive qualitative method. The data collection method is through observation, interview, and documentation. The results of this study indicate that Korean Wave spreads through social media which is currently loved by many teenagers, many factors influence the interest in K-Wave such as fashion styles, music colors, beauty products, and others. The various impacts of K-Wave include increasing the enthusiasm for learning foreign languages, working hard, making money by selling merchandise, and others. as for the negative impacts, namely spending money to buy useless items, and excessive halu. ------------------------------------------------------------------------------------------------Penelitian ini membahas tentang fenomena perkembangan budaya Korea di kalangan mahasiswa di kota Banda Aceh, dan Bagaimana respon dan pandangan mahasiswa terhadap gejala Korean Wafe ini. Penelitian ini bertujuan untuk mengetahui bagaimana mahasiswa bisa menerima, dan terpengaruh dengan budaya Korea. Metode yang digunakan dalam penelitian ini ialah metode deskriptif kualitatif. Adapun metode pengumpulan data melalui observasi, wawancara, dan dokumentasi. Hasil penelitian ini menunjukkan bahwa Korean Wave menyebar melalui sosial media yang saat ini banyak digandrungi oleh remaja, banyaknya faktor yang mempengaruhi ketertarikan terhadap K-Wave seperti fashion style, warna musik, produk kecantikan, dan lainnya. Dampak dari K-Wave yang beragam diantaranya adalah meningkatkan semangat belajar bahasa asing, kerja keras, menghasilkan uang dengan menjual merchandise, dan lainnya.
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Hamd, Mohamed A. El, Marzough Aziz Albalawi, Hassanien Gomaa, Bassam Shaaban Mohammad, Rady F. Abdul-Kareem, Reem H. Obaydo, Wejdan T. Alsaggaf, Safaa F. Saleh, Manal A. Alossaimi und Mohamed A. Abdel-Lateef. „Ziziphus spina-christi Leaf-Derived Carbon Dots as a Fluorescence Nanosensor to Evaluate Rifaximin Antibacterial via Inner Filter Effect: Greenness and Whiteness Studies“. Chemosensors 11, Nr. 5 (03.05.2023): 275. http://dx.doi.org/10.3390/chemosensors11050275.
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Rifaximin (RFX) is a non-absorbable antibiotic with broad-spectrum efficacy. It treats travelers’ diarrhea, irritable bowel syndrome, non-systematic bacterial diarrhea, bowel infections, overgrowth syndrome, and enteric infections. In this work, carbon dots prepared from Ziziphus spina-christi leaves’ powders are utilized as a green fluorometric biosensor for the assessment of RFX. The morphological lineaments of the prepared carbon dots were recognized by using TEM and SEM techniques. The prepared carbon dots manifest a fluorescence emission peak at 432 nm after an excitation fluorescence peak at 366 nm. The absorbance band of RFX (absorbance peaks at 370 nm and 443 nm) could be thoroughly overlapped with fluorescence excitation/emission bands of the produced carbon dots. A fluorometric tool has been designed and validated for the evaluation of RFX reliant on the inner filter effect methodology, in which the produced carbon dots act as an inner filter effect fluorophore and RFX as an inner filter effect absorber. The quenching degree in the fluorescence activity of the prepared carbon dots depended on the concentration of RFX. The analytical parameters were checked and directed for successfully applied assessment of RFX concentration in different pharmaceutical formulations. The proposed tool’s greenness and eco-friendliness profile was evaluated using the most recent greenness assessment tool, which is the complementary green analytical procedure index (Complex-GAPI) and the Analytical GREEnness metric (AGREE). Additionally, using the recently released White Analytical Chemistry (WAC) tool, the whiteness characteristic—which indicated the method’s sustainability—was investigated.
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Kim, Yu-Jin, und Jae Gyoo Lee. „WRF Numerical Study on the Convergent Cloud Band and Its Neighbouring Convective Clouds“. Atmosphere 24, Nr. 1 (31.03.2014): 49–68. http://dx.doi.org/10.14191/atmos.2014.24.1.049.
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Go, Jonggyu, Kyungmin Nam, Boki Kim, Kunjun Lee, Jian Park, Sanghoon Kim und Seungsik Yang. „Ka-Band 16-Way Radial Power Combiner Design with Low-Loss and High-Efficiency“. Journal of Korean Institute of Electromagnetic Engineering and Science 33, Nr. 4 (April 2022): 293–99. http://dx.doi.org/10.5515/kjkiees.2022.33.4.293.
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Batai, Ken, Zuxi Cui, Amit Arora, Ebony Shah-Williams, Wenndy Hernandez, Maria Ruden, Courtney M. P. Hollowell et al. „Genetic loci associated with skin pigmentation in African Americans and their effects on vitamin D deficiency“. PLOS Genetics 17, Nr. 2 (18.02.2021): e1009319. http://dx.doi.org/10.1371/journal.pgen.1009319.
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A recent genome-wide association study (GWAS) in African descent populations identified novel loci associated with skin pigmentation. However, how genomic variations affect skin pigmentation and how these skin pigmentation gene variants affect serum 25(OH) vitamin D variation has not been explored in African Americans (AAs). In order to further understand genetic factors that affect human skin pigmentation and serum 25(OH)D variation, we performed a GWAS for skin pigmentation with 395 AAs and a replication study with 681 AAs. Then, we tested if the identified variants are associated with serum 25(OH) D concentrations in a subset of AAs (n = 591). Skin pigmentation, Melanin Index (M-Index), was measured using a narrow-band reflectometer. Multiple regression analysis was performed to identify variants associated with M-Index and to assess their role in serum 25(OH)D variation adjusting for population stratification and relevant confounding variables. A variant near the SLC24A5 gene (rs2675345) showed the strongest signal of association with M-Index (P = 4.0 x 10−30 in the pooled dataset). Variants in SLC24A5, SLC45A2 and OCA2 together account for a large proportion of skin pigmentation variance (11%). The effects of these variants on M-Index was modified by sex (P for interaction = 0.009). However, West African Ancestry (WAA) also accounts for a large proportion of M-Index variance (23%). M-Index also varies among AAs with high WAA and high Genetic Score calculated from top variants associated with M-Index, suggesting that other unknown genomic factors related to WAA are likely contributing to skin pigmentation variation. M-Index was not associated with serum 25(OH)D concentrations, but the Genetic Score was significantly associated with vitamin D deficiency (serum 25(OH)D levels less than 12 ng/mL) (OR, 1.30; 95% CI, 1.04–1.64). The findings support the hypothesis suggesting that skin pigmentation evolved responding to increased demand for subcutaneous vitamin D synthesis in high latitude environments.
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Emery, Jean M. „Inside Passage: Living with Killer Whales, Bald, Eagles, and Kwakiutl Indians by Michael Modzelewski“. Western American Literature 29, Nr. 1 (1994): 89. http://dx.doi.org/10.1353/wal.1994.0038.
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Hu, Liang, Elizabeth A. Ritchie und J. Scott Tyo. „Short-Term Tropical Cyclone Intensity Forecasting from Satellite Imagery Based on the Deviation Angle Variance Technique“. Weather and Forecasting 35, Nr. 1 (01.02.2020): 285–98. http://dx.doi.org/10.1175/waf-d-19-0102.1.
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Abstract The deviation angle variance (DAV) is a parameter that characterizes the level of organization of a cloud cluster compared with a perfectly axisymmetric tropical cyclone (TC) using satellite infrared (IR) imagery, and can be used to estimate the intensity of the TC. In this study, the DAV technique is further used to analyze the relationship between satellite imagery and TC future intensity over the North Atlantic basin. The results show that the DAV of the TC changes ahead of the TC intensity change, and this can be used to predict short-term TC intensity. The DAV-IR 24-h forecast is close to the National Hurricane Center (NHC) 24-h forecast, and the bias is lower than NHC and other methods during weakening periods. Furthermore, an improved TC intensity forecast is obtained by incorporating all four satellite bands. Using SST and TC latitude as the other two predictors in a linear regression model, the RMSE and MAE of the DAV 24-h forecast are 13.7 and 10.9 kt (1 kt ≈ 0.51 m s−1), respectively, and the skill space of the DAV is about 5.5% relative to the Statistical Hurricane Intensity Forecast model with inland decay (Decay-SHIFOR) during TC weakening periods. Considering the DAV is an independent intensity technique, it could potentially add value as a member of the suite of operational intensity forecast techniques, especially during TC weakening periods.