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Aerosol Plume Detection Algorithm Based on Image Segmentation of Scanning Atmospheric Lidar Data

JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第4期33卷 697-712页

作者： Weekley, R. Andrew Goodrich, R. Kent Cornman, Larry B. Natl Renewable Energy Lab Golden CO USA Univ Colorado Natl Ctr Atmospher Res Boulder CO 80309 USA Univ Colorado Dept Math Boulder CO 80309 USA Sci & Technol Atmospher Res LLC Boulder CO USA Natl Ctr Atmospher Res POB 3000 Boulder CO 80307 USA

An image-processing algorithm has been developed to identify aerosol plumes in scanning lidar backscatter data. The images in this case consist of lidar data in a polar coordinate system. Each full lidar scan is taken as a fixed image in time, and sequences of such scans are considered functions of time. The data are analyzed in both the original backscatter polar coordinate system and a lagged coordinate system. The lagged coordinate system is a scatterplot of two datasets, such as subregions taken from the same lidar scan (spatial delay), or two sequential scans in time (time delay). The lagged coordinate system processing allows for finding and classifying clusters of data. The classification step is important in determining which clusters are valid aerosol plumes and which are from artifacts such as noise, hard targets, or background fields. These cluster classification techniques have skill since both local and global properties are used. Furthermore, more information is available since both the original data and the lag data are used. Performance statistics are presented for a limited set of data processed by the algorithm, where results from the algorithm were compared to subjective truth data identified by a human.

关键词： algorithms Classification Data processing Lidars/Lidar observations Mathematical and statistical techniques observational techniques and algorithms

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Evidence for SST-Forced Anomalous Winds Revealed from Simultaneous Radiosonde Launches from Three Ships across the Kuroshio Extension Front

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MONTHLY WEATHER REVIEW 2016年第10期144卷 3553-3567页

作者： Nishikawa, Hatsumi Tachibana, Yoshihiro Kawai, Yoshimi Yoshioka, Mayumi K. Nakamura, Hisashi Mie Univ Weather & Climate Dynam Div 1577 Kurimamachiya Cho Tsu Mie 5148507 Japan Japan Agcy Marine Earth Sci & Technol Yokosuka Kanagawa Japan Nagoya Univ Nagoya Aichi Japan Univ Tokyo Res Ctr Adv Sci & Technol Tokyo Japan

Simultaneous launches of radiosondes were conducted from three research vessels aligned meridionally across a sea surface temperature (SST) front on the flank of the Kuroshio Extension. The soundings carried out every 2 h over 5 days in early July 2012 provided a unique opportunity in capturing unambiguous data on anomalous easterly winds derived from a pronounced meridional SST gradient. The data indicate that a meridional contrast in surface heat fluxes from the underlying ocean enhanced the air temperature anomaly across the SST front, which was observed from the surface up to 300-m altitude. Correspondingly, high and low pressure anomalies that reached 800-m altitude formed on the north and south sides of the SST front, respectively. These temperature and pressure anomalies were maintained even during the passage of synoptic-scale disturbances. Although the free-tropospheric winds are overall westerly, winds below the 1000-m level were easterly due to geostrophic anomalies driven by the northward pressure gradient near the surface. During periods of the northerlies at the surface, especially over the warmer side of the SST front, the wind direction changed in a clockwise direction from 1500 m to the surface, in the opposite sense to the Ekman spiral. The vertical wind shear is apparently in the thermal wind balance ascribed to the meridional contrast in air temperature derived from the SST anomaly.

关键词： Atm/Ocean Structure/ Phenomena Atmosphere-ocean interaction Fronts Sea surface temperature Wind Physical Meteorology and Climatology Air-sea interaction observational techniques and algorithms Radiosonde observations

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In Situ-Based Reanalysis of the Global Ocean Temperature and Salinity with ISAS: Variability of the Heat Content and Steric Height

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JOURNAL OF CLIMATE 2016年第4期29卷 1305-1323页

作者： Gaillard, Fabienne Reynaud, Thierry Thierry, Virginie Kolodziejczyk, Nicolas von Schuckmann, Karina IFREMER CNRS Ifremer IRD UBO LPO UMR 6523 F-29280 Plouzane France UBO CNRS Ifremer IRD UBO LPO UMR 6523 Plouzane France Mediterranean Inst Oceanog Marseille France

The In Situ Analysis System (ISAS) was developed to produce gridded fields of temperature and salinity that preserve as much as possible the time and space sampling capabilities of the Argo network of profiling floats. Since the first global reanalysis performed in 2009, the system has evolved, and a careful delayed-mode processing of the 2002-12 dataset has been carried out using version 6 of ISAS and updating the statistics to produce the ISAS13 analysis. This last version is now implemented as the operational analysis tool at the Coriolis data center. The robustness of the results with respect to the system evolution is explored through global quantities of climatological interest: the ocean heat content and the steric height. Estimates of errors consistent with the methodology are computed. This study shows that building reliable statistics on the fields is fundamental to improve the monthly estimates and to determine the absolute error bars. The new mean fields and variances deduced from the ISAS13 reanalysis and dataset show significant changes relative to the previous ISAS estimates, in particular in the Southern Ocean, justifying the iterative procedure. During the decade covered by Argo, the intermediate waters appear warmer and saltier in the North Atlantic and fresher in the Southern Ocean than in World Ocean Atlas 2005 long-term mean. At interannual scale, the impact of ENSO on the ocean heat content and steric height is observed during the 2006/07 and 2009/10 events captured by the network.

关键词： Databases Physical Meteorology and Climatology observational techniques and algorithms Temperature In situ oceanic observations Profilers, oceanic Data quality control Salinity

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Remote Sensing of the Surface Wind Field over the Coastal Ocean via Direct Calibration of HF Radar Backscatter Power

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第7期33卷 1377-1392页

作者： Kirincich, Anthony Woods Hole Oceanog Inst 266 Woods Hole Rd Woods Hole MA 02543 USA

The calibration and validation of a novel approach to remotely sense surface winds using land-based high-frequency (HF) radar systems are described. Potentially available on time scales of tens of minutes and spatial scales of 2-3 km for wide swaths of the coastal ocean, HF radar-based surface wind observations would greatly aid coastal ocean planners, researchers, and operational stakeholders by providing detailed real-time estimates and climatologies of coastal winds, as well as enabling higher-quality short-term forecasts of the spatially dependent wind field. Such observations are particularly critical for the developing offshore wind energy community. An autonomous surface vehicle was deployed within the Massachusetts Wind Energy Area, located south of Martha's Vineyard, Massachusetts, for one month, collecting wind observations that were used to test models of wind-wave spreading and HF radar energy loss, thereby empirically relating radar-measured power to surface winds. HF radar-based extractions of the remote wind speed had accuracies of 1.4 m s(-1) for winds less than 7 m s(-1), within the optimal range of the radar frequency used. Accuracies degraded at higher winds due to low signal-to-noise ratios in the returned power and poor resolution of the model. Pairing radar systems with a range of transmit frequencies with adjustments of the extraction model for additional power and environmental factors would resolve many of the errors observed.

关键词： algorithms Atm/Ocean Structure/ Phenomena In situ oceanic observations observational techniques and algorithms Radars/Radar observations Remote sensing Surface observations Wind

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Seasonal Variability in Middepth Gyral Circulation Patterns in the Central East/Japan Sea as Revealed by Long-Term Argo Data

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JOURNAL OF PHYSICAL OCEANOGRAPHY 2016年第3期46卷 937-946页

作者： Kang, Sok Kuh Seung, Young Ho Park, Jong Jin Park, Jae-Hun Lee, Jae Hak Kim, Eun Jin Kim, Young Ho Suk, Moon-Sik Korea Inst Ocean Sci & Technol 787 Haeanro Ansan 426744 South Korea Geo Syst Res Corp Gunpo South Korea Kyungpook Natl Univ Kyungpook Inst Oceanog Taegu 702701 South Korea Inha Univ Inchon South Korea

Trajectories of Argo floats deployed in the East/Japan Sea from 2001 to 2014 reveal that the middepth gyral circulation pattern of the Japan basin, the central part of the East/Japan Sea, undergoes a seasonal variation. The middepth circulation of the Japan basin is found to be characterized usually by the gyres trapped to the east of the Bogorov Rise (E-gyres) and those extending farther westward into the whole basin (BW-gyres). The E-gyre trajectories are generally associated with the turning of the floats toward deeper regions off the isobaths. This occurs in winter either on the northern or eastern side of the eastern Japan basin. It seems that the upstream part of the otherwise BW-gyre is subject to a strong negative wind stress curl in winter, and there the circulating water columns are driven toward the deeper region, thus triggering the formation of the E-gyre. The topographic effect associated with the Bogorov Rise seems to interfere thereafter in the process of determining the passage of the E-gyre. Otherwise, the water columns continue to flow along the isobaths, hence maintaining the BW-gyre. To the knowledge of the authors, this is the first observational evidence of seasonal variability in the middepth gyral circulation pattern in the East/Japan Sea. It suggests that oceanic middepth circulation, usually known to be quasi steady or slowly varying on climatological time scales, might also undergo a significant seasonal variation as it does in the East/Japan Sea.

关键词： observational techniques and algorithms Ocean dynamics Trajectories Circulation/ Dynamics Profilers, oceanic Seasonal variability Ocean circulation Variability Wind stress

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Evaluation of the Accuracy and Utility of Tropical Cyclone Intensity Estimation Using Single Ground-Based Doppler Radar Observations

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MONTHLY WEATHER REVIEW 2016年第5期144卷 1823-1840页

作者： Shimada, Udai Sawada, Masahiro Yamada, Hiroyuki Meteorol Res Inst Tsukuba Ibaraki 3050052 Japan Univ Ryukyus Nishihara Okinawa 90301 Japan

Intensities (central pressures) of 28 cases of 22 tropical cyclones (TCs) that approached Japan were estimated by using single ground-based Doppler radar observations, and the accuracy and utility of the estimation-method were evaluated. The method uses the ground-based velocity track display (GBVTD) technique, which retrieves tangential winds, and the gradient wind balance equation. Before application of the method to the 28 cases, a preliminary experiment was performed with pseudo-Doppler velocities obtained by numerical simulation to confirm that the method could reasonably estimate central pressures. Compared with best track data from the Regional Specialized Meteorological Center (RSMC) Tokyo, the estimated intensities of the 28 cases had a root-mean-square error of 8.37 hPa and showed a bias of 1.51 hPa. This level of accuracy is comparable to or better than the accuracies of Dvorak and satellite microwave-derived estimates. Two distance metrics are defined: 1) the distance between the TC center and the radar location and 2) the distance between the TC center and the weather station whose sea level pressure was used as an anchor for pressure measurement. In general, the accuracy of the Doppler radar estimates was higher when the distance metrics were shorter, as well as when wind retrieval accuracy was better and radar coverage was denser. For TCs with a radius of maximum wind of 20-70 km, the estimated central pressures had a root-mean-square error of 5.55 hPa. These results confirm that Doppler radar intensity estimates have sufficient accuracy and utility for operational use.

关键词： Atm/Ocean Structure/ Phenomena Tropical cyclones observational techniques and algorithms Radars/Radar observations

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Impact of MPEX Upsonde Observations on Ensemble Analyses and Forecasts of the 31 May 2013 Convective Event over Oklahoma

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MONTHLY WEATHER REVIEW 2016年第8期144卷 2889-2913页

作者： Hitchcock, Stacey M. Coniglio, Michael C. Knopfmeier, Kent H. Univ Oklahoma Sch Meteorol Norman OK 73019 USA Univ Oklahoma Cooperat Inst Mesoscale Meteorol Studies Norman OK 73019 USA NOAA OAR Natl Severe Storms Lab Norman OK USA Colorado State Univ Dept Atmospher Sci 3915 W Laport Ave Ft Collins CO 80523 USA

This study examines the impact of assimilating three radiosonde profiles obtained from ground-based mobile systems during the Mesoscale Predictability Experiment (MPEX) on analyses and convection-permitting model forecasts of the 31 May 2013 convective event over Oklahoma. These radiosonde profiles (in addition to standard observations) are assimilated into a 36-member mesoscale ensemble using an ensemble Kalman filter (EnKF) before embedding a convection-permitting (3 km) grid and running a full ensemble of 9-h forecasts. This set of 3-km forecasts is compared to a control run that does not assimilate the MPEX soundings. The analysis of low-to midlevel moisture is impacted the most by the assimilation, but coherent mesoscale differences in temperature and wind are also seen, primarily downstream of the location of the soundings. The ensemble of forecasts of convection on the 3-km grid are improved the most in the first three hours of the forecast in a region where the analyzed position of low-level frontal convergence and midlevel moisture was improved on the mesoscale grid. Later forecasts of the upscale growth of intense convection over central Oklahoma are improved somewhat, but larger ensemble spread lowers confidence in the significance of the improvements. Changes in the horizontal localization radius from the standard value applied to the MPEX sounding assimilation alters the specific times that the forecasts are improved in the first three hours of the forecasts, while changes to the vertical localization radius and specified temperature and wind observation error result in little to no improvements in the forecasts.

关键词： Atm/Ocean Structure/ Phenomena Severe storms observational techniques and algorithms Radiosonde observations Forecasting Numerical weather prediction/forecasting Models and modeling Data assimilation Mesoscale models Applications Field experiments

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Tropical Cyclone Diurnal Cycle as Observed by TRMM

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MONTHLY WEATHER REVIEW 2016年第8期144卷 2793-2808页

作者： Leppert, Kenneth D., II Cecil, Daniel J. Univ Alabama Ctr Earth Syst Sci Huntsville AL 35899 USA NASA Marshall Space Flight Ctr Huntsville AL USA Univ Louisiana Monroe Monroe LA USA

Previous work has indicated a clear, consistent diurnal cycle in rainfall and cold cloudiness coverage around tropical cyclones. This cycle may have important implications for structure and intensity changes of these storms and the forecasting of such changes. The goal of this paper is to use passive and active microwave measurements from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and Precipitation Radar (PR), respectively, to better understand the tropical cyclone diurnal cycle throughout a deep layer of a tropical cyclone's clouds. The composite coverage by PR reflectivity >= 20 dBZ at various heights as a function of local standard time (LST) and radius suggests the presence of a diurnal signal for radii <500 km through a deep layer (2-10-km height) of the troposphere using 1998-2011 Atlantic tropical cyclones of at least tropical storm strength. The area covered by reflectivity >= 20 dBZ at radii 100-500 km peaks in the morning (0130-1030 LST) and reaches a minimum 1030-1930 LST. Radii between 300 and 500 km tend to reach a minimum in coverage closer to 1200 LST before reaching another peak at 2100 LST. The inner core (0-100 km) appears to be associated with a single-peaked diurnal cycle only at upper levels (8-10 km) with a maximumat 2230-0430 LST. The TMI rainfall composites suggest a clear diurnal cycle at all radii between 200 and 1000 km with peak rainfall coverage and rain rate occurring in the morning (0130-0730 LST).

关键词： Atm/Ocean Structure/ Phenomena Tropical cyclones observational techniques and algorithms Microwave observations

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Calibration Method of Low-Light Sensor Based on Bridge Lights

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第6期33卷 1123-1134页

作者： Ma, Shuo Yan, Wei Huang, Yunxian Jiang, Jun Hu, Shensen Wang, Yingqiang Peoples Liberat Army Univ Sci & Technol Coll Meteorol & Oceanog 60 Shuanglong St Nanjing 211101 Jiangsu Peoples R China

Many quantitative uses of the nighttime imagery provided by low-light sensors, such as the day-night band (DNB) on board the Suomi-National Polar-Orbiting Partnership (SNPP), have emerged recently. Owing to the low nighttime radiance, low-light calibration at night must be investigated in detail. Traditional vicarious calibration methods are based on some targets with nearly invariant surface properties under lunar illumination. However, the relatively stable light emissions may also be used to realize the radiometric calibration under low light. This paper presents a low-light calibration method based on bridge lights, and Visible Infrared Imaging Radiometer Suite (VIIRS) DNB data are used to assess the proposed method. A comparison of DNB high-gain-stage (HGS) radiances over a 2-yr period from August 2012 to July 2014 demonstrates that the predictions are consistent with the observations, and the agreement between the predictions and the observations is on the order of -2.9% with an uncertainty of 9.3% (1 sigma) for the Hangzhou Bay Bridge and -3.9% with an uncertainty of 7.2% (1 sigma) for the Donghai Bridge. Such a calibration method based on stable light emissions has a wide application prospect for the calibration of low-light sensors at night.

关键词： Geographic location/entity Asia Physical Meteorology and Climatology Radiances observational techniques and algorithms algorithms Remote sensing Satellite observations Mathematical and statistical techniques Statistics

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Comparison of the Tornadic and Nontornadic Supercells Intercepted by VORTEX2 on 10 June 2010

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MONTHLY WEATHER REVIEW 2016年第9期144卷 3201-3231页

作者： Klees, Alicia M. Richardson, Yvette P. Markowski, Paul M. Weiss, Christopher Wurman, Joshua M. Kosiba, Karen K. Penn State Univ University Pk PA 16802 USA Texas Tech Univ Lubbock TX 79409 USA Ctr Severe Weather Res Boulder CO USA

On 10 June 2010, the second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) armada collected a rare set of observations of a nontomadic and a tornadic supercell evolving in close proximity to each other. The storms and their environments were analyzed using single- and dual-Doppler radar, mobile mesonet, deployable surface mesonet, and mobile sounding data, with the goal of understanding why one supercell produced no tornadoes while the other produced at least two. Outflow temperature deficits were similar for the two storms, both within the normal range for weakly tornadic supercells but somewhat cold relative to significantly tornadic supercells. The storms formed in a complex environment, with slightly higher storm-relative helicity near the tornadic supercell. The environment evolved significantly in time, with large thermodynamic changes and increases in storm-relative helicity, leading to conditions much more favorable for tomadogenesis. After a few hours, a new storm developed between the supercells, likely leading to the demise of the nontomadic supercell before it was able to experience the enhanced environmental conditions. Two tornadoes developed within the single mesocyclone of the other supercell. After the dissipation of the second tornado, rapid rearward motion of low- to midlevel circulations may have inhibited further tornado production in this storm.

关键词： Atm/Ocean Structure/ Phenomena Severe storms Tornadoes observational techniques and algorithms Radars/Radar observations Soundings

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