Journal of Atmospheric and Oceanic Technology最新文献_第4页

Exploring Tornadic Debris Signature Hypotheses Using Radar Simulations and Large-Eddy Simulations 利用雷达模拟和大涡模拟探索龙卷风碎片特征假设

IF 2.2 4区地球科学

Journal of Atmospheric and Oceanic Technology Pub Date : 2023-08-14 DOI: 10.1175/jtech-d-22-0141.1

Rachael N. Cross, D. Bodine, R. Palmer, Casey B. Griffin, B. Cheong, S. Torres, C. Fulton, J. Lujan, T. Maruyama

{"title":"Exploring Tornadic Debris Signature Hypotheses Using Radar Simulations and Large-Eddy Simulations","authors":"Rachael N. Cross, D. Bodine, R. Palmer, Casey B. Griffin, B. Cheong, S. Torres, C. Fulton, J. Lujan, T. Maruyama","doi":"10.1175/jtech-d-22-0141.1","DOIUrl":"https://doi.org/10.1175/jtech-d-22-0141.1","url":null,"abstract":"\u0000When a tornado lofts debris to the height of the radar beam, a signature known as the tornadic debris signature (TDS) can sometimes be observed on radar. The TDS is a useful signature for operational forecasters as it can confirm the presence of a tornado and provide information about the amount of damage occurring. Since real-time estimates of tornadic intensity do not have a high degree of accuracy, past studies have hypothesized that the TDS could also be an indicator of the strength of a tornado. However, few studies have related the tornadic wind field to TDS characteristics due to the difficulty of obtaining accurate, three-dimensional wind data in tornadoes from radar data. With this in mind, the goals of this study are twofold: 1) to investigate the relationships between polarimetric characteristics of TDSs and the three-dimensional tornadic winds, and 2) to define relationships between polarimetric radar variables and debris characteristics. Simulations are performed using a dual-polarization radar simulator called SimRadar; Large-Eddy Simulations (LESs) of tornadoes; and a single-volume, T-matrix based emulator. Results show that increases (decreases) in horizontal and vertical wind speeds are related to decreases (increases) in correlation coefficient and increases (decreases) in TDS area and height for all simulated debris types. However, the range of correlation coefficient values varies with debris type, indicating that TDSs comprised of similar debris types can appear remarkably different on radar compared to a TDS with diverse scatterers. Such findings confirm past, observational hypotheses and can aid operational forecasters in tornado detection and potentially the categorization of damage severity using radar data.","PeriodicalId":15074,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46770652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A Novel Doppler Unfolding Technique Using Optical Flow 一种新型的光流多普勒展开技术

IF 2.2 4区地球科学

Journal of Atmospheric and Oceanic Technology Pub Date : 2023-08-11 DOI: 10.1175/jtech-d-23-0057.1

A. Protat, V. Louf, M. Curtis

{"title":"A Novel Doppler Unfolding Technique Using Optical Flow","authors":"A. Protat, V. Louf, M. Curtis","doi":"10.1175/jtech-d-23-0057.1","DOIUrl":"https://doi.org/10.1175/jtech-d-23-0057.1","url":null,"abstract":"\u0000Doppler radars measure Doppler velocity within the [-VN, VN] range, where VN is the Nyquist velocity. Doppler velocities outside of this range are “folded” within this interval. All Doppler “unfolding” techniques use the folded velocities themselves. In this work, we investigate the potential of using velocities derived from optical flow techniques applied to the radar reflectivity field for that purpose. The analysis of wind speed errors using six months of multi-Doppler wind retrievals showed that 99.9% of all points are characterized by errors smaller than 26 ms-1 below 5 km height, corresponding to a failure rate of less than 0.01% if optical flow winds were used to unfold Doppler velocities for VN = 26 ms-1. These errors largely increase above 5 km height, indicating that vertical continuity tests should be included to reduce failure rates at higher elevations. Following these results, we have developed the Two-step Optical Flow Unfolding (TOFU) technique, with the specific objective to accurately unfold Doppler velocities with VN = 26 ms-1.\u0000The TOFU performance was assessed using challenging case studies, comparisons with an advanced Doppler unfolding technique using higher Nyquist velocities, and six months of high VN (47.2 ms-1) data artificially folded to 26 ms-1. TOFU failure rates were found to be very low. Three main situations contributed to these errors: high low-level wind shear, elevated cloud layers associated with high winds, and radar data artefacts. Our recommendation is to use these unfolded winds as the first step of advanced Doppler unfolding techniques.","PeriodicalId":15074,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45365082","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Observations of Surface Gravity Wave Spectra from Moving Platforms 移动平台表面重力波谱观测

IF 2.2 4区地球科学

Journal of Atmospheric and Oceanic Technology Pub Date : 2023-08-08 DOI: 10.1175/jtech-d-23-0022.1

Luke Colosi, N. Pizzo, L. Grare, N. Statom, L. Lenain

{"title":"Observations of Surface Gravity Wave Spectra from Moving Platforms","authors":"Luke Colosi, N. Pizzo, L. Grare, N. Statom, L. Lenain","doi":"10.1175/jtech-d-23-0022.1","DOIUrl":"https://doi.org/10.1175/jtech-d-23-0022.1","url":null,"abstract":"\u0000Surface waves play an important role in the ocean-atmosphere coupled climate system by mediating the exchange of momentum, heat, and gas between the atmosphere and the ocean. Pseudo-Lagrangian autonomous platforms (e.g., Boeing Liquid Robotics Wave Gliders) have been used to investigate the underlying physical dynamics involved in these processes to better parameterize the air-sea exchange occurring at the scale of the surface waves. This requires accurate measurements of directional surface waves down to short scales (O(1) meter), as these shorter waves support most of the stress between the atmosphere and the ocean. A challenge to overcome for pseudo-Lagrangian autonomous vehicles is that the platform’s velocity causes the observed frequency of the waves to be Doppler shifted. This leads to a modulation of the wave spectrum, particularly at high frequencies, that depends on the platform’s speed, the wave frequency, and the relative angle between the direction of wave and platform propagation. In this work, we propose a method to account for Doppler effects that considers the full directionality of the wave field. The method is validated using a unique dataset collected from a fleet of two Wave Gliders off the coast of Southern California in September 2019 operating on the perimeter of a tight square (500-m edge length) track over a three-day deployment. This technique can be used to estimate wave spectra derived from other slow-moving surface vehicles such as Saildrones that use platform motion to characterize the surface wave field. MATLAB routines to implement this method are publicly available.","PeriodicalId":15074,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48353272","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A mapping methodology adapted to all polar and subpolar oceans with a stretching/shrinking constraint 一种适用于所有极地和副极地海洋的测绘方法，具有拉伸/收缩约束

IF 2.2 4区地球科学

Journal of Atmospheric and Oceanic Technology Pub Date : 2023-08-07 DOI: 10.1175/jtech-d-22-0143.1

Vigan Mensah, K. Ohshima

{"title":"A mapping methodology adapted to all polar and subpolar oceans with a stretching/shrinking constraint","authors":"Vigan Mensah, K. Ohshima","doi":"10.1175/jtech-d-22-0143.1","DOIUrl":"https://doi.org/10.1175/jtech-d-22-0143.1","url":null,"abstract":"\u0000Polar and subpolar oceans play a particularly important role in the global climate and its temporal changes, yet these regions are less well sampled than the rest of the global ocean. To better understand the physical or biogeochemical properties and their variabilities in these regions, accurate data mapping is crucial. In this paper, we introduce a mapping methodology that includes a water column shrinking and stretching constraint (SSC) based on the principle of conservation of potential vorticity. To demonstrate the mapping scheme efficiency, we map the ocean temperature in the southern Sea of Okhotsk, where the bottom topography comprises a broad and shallow shelf, a sharp continental slope, and a deep oceanic basin. Such topographic features are typical of polar and subpolar marginal seas. Results reveal that the SSC integrated (SSCI) mapping strongly reduces the mapping error in the broad and shallow shelf compared with a recently introduced topographic constraint integrated (TCI) mapping procedure. We also tested our mapping scheme in the Southern Ocean, which has a comparatively slanted shelf, a wider and gentler slope, and a deep and broad oceanic basin. We found that the SSCI and TCI methods are practically equivalent there. The SSCI mapping is thus an effective method to map the ocean’s properties in various topographic environments and should be adequate in all polar and subpolar regions. Importantly, we introduced a standardized procedure for determining the decorrelation length scales—a necessary step prior to implementing any mapping scheme—in any topographic conditions.","PeriodicalId":15074,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47120566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Masthead 报头

IF 2.2 4区地球科学

Journal of Atmospheric and Oceanic Technology Pub Date : 2023-08-01 DOI: 10.1175/jtech-408masthead

引用次数: 0

Estimation of transmitted differential phase on dual polarization radars 双偏振雷达上传输差相位的估计

IF 2.2 4区地球科学

Journal of Atmospheric and Oceanic Technology Pub Date : 2023-07-27 DOI: 10.1175/jtech-d-22-0014.1

D. Zrnić, V. Melnikov

{"title":"Estimation of transmitted differential phase on dual polarization radars","authors":"D. Zrnić, V. Melnikov","doi":"10.1175/jtech-d-22-0014.1","DOIUrl":"https://doi.org/10.1175/jtech-d-22-0014.1","url":null,"abstract":"\u0000A measurement procedure to determine transmitted differential phase between horizontally and vertically polarized radiation of a dual polarization radar is presented. It is applicable to radars that transmit and receive Simultaneously Horizontally and Vertically (SHV) polarized waves. The method relies solely on weather data with no instrument intrusions whatsoever. It takes data at vertical incidence while the antenna rotates in azimuth. That way a large number of samples is collected to reduce statistical errors in estimates. The theory indicates that the transmitted differential phase appears prominently in the backscatter signals off the melting layer. That and relations between various elements of the backscattering matrix are used to derive a set of nonlinear equations whereby the differential phase on transmission is one of the unknowns. Steps for solving these equations are presented as well as a demonstration of the results on radar data. Finally, a simplified algorithm that bypasses the coupled nonlinear equations is exposed. Conditions under which the simplification can be applied are presented. These restrict the range of the transmitted differential phase for which the simplified procedure may be applied.","PeriodicalId":15074,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44646626","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Estimation of Surface Current Divergence from Satellite Doppler Radar Scatterometer Measurements of Surface Ocean Velocity 卫星多普勒雷达散射仪测量海面流速估算海面海流发散

IF 2.2 4区地球科学

Journal of Atmospheric and Oceanic Technology Pub Date : 2023-07-24 DOI: 10.1175/jtech-d-23-0052.1

D. Chelton

{"title":"Estimation of Surface Current Divergence from Satellite Doppler Radar Scatterometer Measurements of Surface Ocean Velocity","authors":"D. Chelton","doi":"10.1175/jtech-d-23-0052.1","DOIUrl":"https://doi.org/10.1175/jtech-d-23-0052.1","url":null,"abstract":"\u0000The ability to estimate surface current divergence and vorticity from space is assessed from simulated satellite Doppler radar scatterometer measurements of surface velocity with an effective footprint diameter of 5 km across an 1800-km measurement swath. The focus is on non-internal-wave contributions to divergence and vorticity. This is achieved by simulating Doppler measurements of surface velocity from a numerical model in which internal waves are weak because of high dissipation, seasonal cycle forcing and the lack of tidal forcing. Divergence is much more challenging to estimate than vorticity because the signals are weaker and restricted to smaller scales. With the measurement noise that was anticipated based on early engineering studies, divergence cannot be estimated with useful resolution. Recent advances in the understanding of how the noise in measurements of surface currents depends on the ambient wind speed have concluded that measurement noise will be substantially smaller in conditions of wind speed greater than 6 m s−1. A reassessment of the ability to estimate non-internal-wave contributions to surface current divergence in this study finds that useful estimates can be obtained in such wind conditions; the wavelength resolution capability for divergence estimates in the middle of the measurement swaths will be better than 100 km in 16-day averages. The improved measurement accuracy will also provide estimates of surface current vorticity with a resolution nearly a factor-of-2 higher than was previously thought, resulting in wavelength resolutions of about 50 km, 30 km and 20 km in snapshots, 4-day averages and 16-day averages, respectively.","PeriodicalId":15074,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45319269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Performance Evaluation of the Lightning Imaging Sensor on the International Space Station 国际空间站雷电成像传感器性能评价

IF 2.2 4区地球科学

Journal of Atmospheric and Oceanic Technology Pub Date : 2023-07-21 DOI: 10.1175/jtech-d-22-0120.1

Daile Zhang, K. Cummins, T. Lang, D. Buechler, S. Rudlosky

{"title":"Performance Evaluation of the Lightning Imaging Sensor on the International Space Station","authors":"Daile Zhang, K. Cummins, T. Lang, D. Buechler, S. Rudlosky","doi":"10.1175/jtech-d-22-0120.1","DOIUrl":"https://doi.org/10.1175/jtech-d-22-0120.1","url":null,"abstract":"\u0000Optical lightning observations from low-Earth orbit play an important role in our understanding of long-term global lightning trends. Lightning Imaging Sensors (LIS) on the Tropical Rainfall Measurement Mission (TRMM) satellite (1997-2015) and International Space Station (2017-present) capture optical emissions produced by lightning. This study uses the well-documented TRMM LIS performance to determine if the ISS LIS performs well enough to bridge the gap between TRMM LIS and the new generation of Geostationary Lightning Mappers (GLMs). The average events per group and groups per flash for ISS LIS are 3.6 and 9.9, which are 25% and 10% lower than TRMM LIS, respectively. ISS LIS has 30% lower mean group energy density and 30-50% lower mean flash energy density than TRMM LIS in their common (+/−38 degree) latitude range. These differences are likely the result of larger pixel areas for ISS LIS over most of the field-of-view due to off-nadir pointing, combined with viewing obstructions and possible engineering differences. For both instruments, radiometric sensitivity decreases radially from the center of the array to the edges. ISS LIS sensitivity falls-off faster and more-variably, contributed to by the off-nadir pointing. Event energy density analysis indicate some anomalous hotspot pixels in the ISS LIS pixel array that were not present with the TRMM LIS. Despite these differences, ISS LIS provides similar parameter values to TRMM LIS with the expectation of somewhat lower lightning detection capability. In addition, recalculation of the event, group, and flash areas for both LIS datasets are strongly recommended since the archived values in the current release versions have significant errors.","PeriodicalId":15074,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":"1 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64665998","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Diagnosing seasonal forecast skill of the Indian Ocean Dipole mode using model-analogs 用模式类似物诊断印度洋偶极子模式的季节预报技巧

IF 2.2 4区地球科学

Journal of Atmospheric and Oceanic Technology Pub Date : 2023-07-20 DOI: 10.1175/jtech-d-22-0106.1

Yanling Wu, Youmin Tang

{"title":"Diagnosing seasonal forecast skill of the Indian Ocean Dipole mode using model-analogs","authors":"Yanling Wu, Youmin Tang","doi":"10.1175/jtech-d-22-0106.1","DOIUrl":"https://doi.org/10.1175/jtech-d-22-0106.1","url":null,"abstract":"\u0000A retrospective tropical Indian Ocean Dipole mode (IOD) hindcast for 1958–2014 was conducted using 20 models from the sixth phase of the Coupled Model Intercomparison Project (CMIP6), with a model-based analog forecast (MAF) method. In the MAF approach, forecast ensembles are extracted from preexisting model simulations by finding the states that initially best match an observed anomaly and tracking their subsequent evolution, with no additional model integrations. By optimizing the key factors in the MAF method, we suggest that the optimal do main for the analog criteria should be concentrated in the tropical Indian Ocean region for IOD predictions. Including external forcing trends improves the skills of the east and west poles of the IOD, but not the IOD prediction itself. The MAF IOD prediction showed comparable skills to the assimilation-initialized hindcast, with skillful predictions corresponding to a 4- and 3-month lead respectively. The IOD forecast skills had significant decadal variations during the 55-year period, with low skills after the early 2000s and before 1985 and high skills during 1985–2000. This work offers a computational efficiency and practical approach for seasonal prediction of the tropical Indian Ocean sea surface temperature.","PeriodicalId":15074,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46987576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Optimizing The Biogeochemical Argo Float Distribution 优化生物地球化学Argo浮体分布

IF 2.2 4区地球科学

Journal of Atmospheric and Oceanic Technology Pub Date : 2023-07-12 DOI: 10.1175/jtech-d-22-0093.1

P. Chamberlain, L. Talley, B. Cornuelle, M. Mazloff, S. Gille

{"title":"Optimizing The Biogeochemical Argo Float Distribution","authors":"P. Chamberlain, L. Talley, B. Cornuelle, M. Mazloff, S. Gille","doi":"10.1175/jtech-d-22-0093.1","DOIUrl":"https://doi.org/10.1175/jtech-d-22-0093.1","url":null,"abstract":"\u0000The core Argo array has operated with the design goal of uniform spatial distribution of 3° in latitude and longitude. Recent studies have acknowledged that spatial and temporal scales of variability in some parts of the ocean are not resolved by 3° sampling and have recommended increased core Argo density in the equatorial region, boundary currents, and marginal seas with an integrated vision of other Argo variants. Biogeochemical (BGC) Argo floats currently observe the ocean from a collection of pilot arrays, but recently funded proposals will transition these pilot arrays to a global array. The current BGC Argo implementation plan recommends uniform spatial distribution of BGC Argo floats. For the first time, we estimate the effectiveness of the existing BGC Argo array to resolve the anomaly from the mean using a subset of modeled, full-depth BGC fields. We also study the effectiveness of uniformly-distributed BGC Argo arrays with varying float densities at observing the ocean. Then, using previous Argo trajectories, we estimate the Argo array’s future distribution and quantify how well it observes the ocean. Finally, using a novel technique for sequentially identifying the best deployment locations, we suggest the optimal array distribution for BGC Argo floats to minimize objective mapping uncertainty in a subset of BGC fields and to best constrain BGC temporal variability.","PeriodicalId":15074,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42856665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0