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Dynamics of Orographic Gravity Waves Observed in the Mesosphere over the Auckland Islands during the Deep Propagating Gravity Wave Experiment (DEEPWAVE)

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JOURNAL OF THE ATMOSPHERIC SCIENCES 2016年第10期73卷 3855-3876页

作者： Eckermann, Stephen D. Broutman, Dave Ma, Jun Doyle, James D. Pautet, Pierre-Dominique Taylor, Michael J. Bossert, Katrina Williams, Bifford P. Fritts, David C. Smith, Ronald B. US Naval Res Lab Div Space Sci Washington DC USA Computat Phys Inc Springfield VA USA US Naval Res Lab Marine Meteorol Div Monterey CA USA Utah State Univ Ctr Atmospher & Space Sci Logan UT 84322 USA GATS Inc Boulder CO USA Yale Univ Dept Geol & Geophys New Haven CT USA

On 14 July 2014 during the Deep Propagating Gravity Wave Experiment (DEEPWAVE), aircraft remote sensing instruments detected large-amplitude gravity wave oscillations within mesospheric airglow and sodium layers at altitudes z similar to 78-83 km downstream of the Auckland Islands, located similar to 1000 km south of Christchurch, New Zealand. A high-altitude reanalysis and a three-dimensional Fourier gravity wave model are used to investigate the dynamics of this event. At 0700 UTC when the first observations were made, surface flow across the islands' terrain generated linear three-dimensional wave fields that propagated rapidly to z similar to 78 km, where intense breaking occurred in a narrow layer beneath a zero-wind region at z similar to 83 km. In the following hours, the altitude of weak winds descended under the influence of a large-amplitude migrating semidiurnal tide, leading to intense breaking of these wave fields in subsequent observations starting at 1000 UTC. The linear Fourier model constrained by upstream reanalysis reproduces the salient aspects of observed wave fields, including horizontal wavelengths, phase orientations, temperature and vertical displacement amplitudes, heights and locations of incipient wave breaking, and momentum fluxes. Wave breaking has huge effects on local circulations, with inferred layer-averaged westward flow accelerations of similar to 350 ms(-1) h(-1) and dynamical heating rates of similar to 8K h(-1), supporting recent speculation of important impacts of orographic gravity waves from subantarctic islands on the mean circulation and climate of the middle atmosphere during austral winter.

关键词： Geographic location/entity Southern Ocean Circulation/ Dynamics Gravity waves Mountain waves Wave breaking Atm/Ocean Structure/ Phenomena Middle atmosphere observational techniques and algorithms Aircraft observations

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Potential Gaps in the Satellite Observing System Coverage: Assessment of Impact on NOAA's Numerical Weather Prediction Overall Skills

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MONTHLY WEATHER REVIEW 2016年第7期144卷 2547-2563页

作者： Boukabara, Sid-Ahmed Garrett, Kevin Kumar, V. Krishna NOAA NESDIS STAR College Pk MD USA NOAA RTi NESDIS STAR College Pk MD USA

The current constellation of environmental satellites is at risk of degrading due to several factors. This includes the following: 1) loss of secondary polar-orbiting satellites due to reaching their nominal lifetimes, 2) decrease in the density of extratropical radio-occultation (RO) observations due to a likely delayed launch of the Constellation Observing System for Meteorology, Ionosphere and Climate-2 (COSMIC-2) high inclination orbit constellation, and 3) the risk of losing afternoon polar-orbiting satellite coverage due to potential launch delays in the Joint Polar Satellite System (JPSS) programs. In this study, the impacts from these scenarios on the National Oceanic and Atmospheric Administration (NOAA) Global Forecast System skill are quantified. Performances for several metrics are assessed, but to encapsulate the results the authors introduce an overall forecast score combining metrics for all parameters, atmospheric levels, and forecast lead times. The first result suggests that removing secondary satellites results in significant degradation of the forecast. This is unexpected since it is generally assumed that secondary sensors contribute to system's robustness but not necessarily to forecast performance. Second, losing the afternoon orbit on top of losing secondary satellites further degrades forecast performances by a significant margin. Finally, losing extratropical RO observations on top of losing secondary satellites also negatively impacts the forecast performances, but to a lesser degree. These results provide a benchmark that will allow for the assessment of the added value of projects being implemented at NOAA in support of mitigation strategies designed to alleviate the negative impacts associated with these data gaps, and additionally help NOAA to define requirements of the future global observing system architecture.

关键词： Forecast verification/skill Forecasting Numerical weather prediction/forecasting observational techniques and algorithms Satellite observations Sensitivity studies

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Reconstructed Regional Mean Climate with Bayesian Model Averaging: A Case Study for Temperature Reconstruction in the Yunnan-Guizhou Plateau, China

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JOURNAL OF CLIMATE 2016年第14期29卷 5355-5361页

作者： Zhang, Xianliang Yan, Xiaodong Chen, Zhenju Shenyang Agr Univ Tree Ring Lab Coll Forestry Shenyang Peoples R China Beijing Normal Univ State Key Lab Earth Surface Proc & Resource Ecol Beijing Peoples R China Chinese Acad Sci Qingyuan Forest CERN Shenyang Peoples R China

A method was developed, based on Bayesian model averaging (BMA), to reconstruct regional mean temperature. Different from the arithmetic mean, which gives equal weight to each chronology, BMA weights the chronologies according to their contributions to the actual temperature variances. Thus, BMA holds advantages in integrating chronologies to reconstruct the regional mean temperature. The regional mean temperature for the Yunnan-Guizhou Plateau was reconstructed for the past four centuries (1628-2005) using BMA, which performed better than the simple arithmetic mean. The reconstruction explained 41.33% of total observed temperature variances during the period of 1961-2005. The warmest decade was found to be 1840-50 and the coldest 1810-20 prior to the instrumental period. The reconstructed temperature showed a high correlation (r > 0.7, p < 0.001) with gridded observed temperatures in most grid cells of the Yunnan-Guizhou Plateau, suggesting that the regional temperature changes were captured well by the reconstruction.

关键词： Physical Meteorology and Climatology Climate change Paleoclimate observational techniques and algorithms Tree rings Mathematical and statistical techniques Bayesian methods

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Factors Controlling Cloud Albedo in Marine Subtropical Stratocumulus Regions in Climate Models and Satellite Observations

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JOURNAL OF CLIMATE 2016年第10期29卷 3559-3587页

作者： Bender, Frida A. -M. Engstrom, Anders Karlsson, Johannes Stockholm Univ Dept Meteorol S-10691 Stockholm Sweden Stockholm Univ Bolin Ctr Climate Res S-10691 Stockholm Sweden

This study focuses on the radiative properties of five subtropical marine stratocumulus cloud regions, on monthly mean scale. Through examination of the relation between total albedo and cloud fraction, and its variability and relation to other parameters, some of the factors controlling the reflectivity, or albedo, of the clouds in these regions are investigated. It is found that the main part of the variability in albedo at a given cloud fraction can be related to temporal rather than spatial variability, indicating spatial homogeneity in cloud radiative properties in the studied regions. This is seen most clearly in satellite observations but also appears in an ensemble of climate models. Further comparison between satellite data and output from climate models shows that there is good agreement with respect to the role of liquid water path, the parameter that can be assumed to be the primary source of variability in cloud reflectivity for a given cloud fraction. On the other hand, the influence of aerosol loading on cloud albedo differs between models and observations. The cloud-albedo effect, or cloud brightening caused by aerosol through its coupling to cloud droplet number concentration and droplet size, is found not to dominate in the satellite observations on monthly mean scale, as it appears to do on this scale in the climate models. The disagreement between models and observations is particularly strong in regions with frequent occurrence of absorbing aerosols above clouds, where satellite data, in contrast to the climate models, indicate a scene darkening with increasing aerosol loading.

关键词： Atm/Ocean Structure/ Phenomena Clouds Physical Meteorology and Climatology Aerosols Cloud radiative effects observational techniques and algorithms Satellite observations Models and modeling Climate models

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Sea Surface Temperature Climate Data Record for the North Sea and Baltic Sea

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JOURNAL OF CLIMATE 2016年第7期29卷 2529-2541页

作者： Hoyer, Jacob L. Karagali, Ioanna Danish Meteorol Inst Lyngbyvej 100 DK-2100 Copenhagen O Denmark Tech Univ Denmark Dept Wind Energy Riso Campus Roskilde Denmark

A 30-yr climate data record (CDR) of sea surface temperature (SST) has been produced with daily gap-free analysis fields for the North Sea and the Baltic Sea region from 1982 to 2012 by combining the Pathfinder AVHRR satellite data record with the Along-Track Scanning Radiometer (ATSR) Reprocessing for Climate (ARC) dataset and with in situ observations. A dynamical bias correction scheme adjusts the Pathfinder observations toward the ARC and in situ observations. Largest Pathfinder-ARC differences are found in the summer months, when the Pathfinder observations are up to 0.4 degrees C colder than the ARC observations on average. Validation against independent in situ observations shows a very stable performance of the data record, with a mean difference of -0.06 degrees C compared to moored buoys and a 0.46 degrees C standard deviation of the differences. The mean annual biases of the SST CDR are small for all years, with a negligible temporal trend when compared against drifting and moored buoys. Analysis of the SST CDR reveals that the monthly anomalies for the North Sea, the Danish straits, and the central Baltic Sea regions show a high degree of correlation for interannual and decadal time scales, whereas the monthly variability differs from one region to another. The linear trends of the 1982-2012 SST anomaly time series range from 0.037 degrees C yr(-1) for the North Sea to 0.041 degrees C yr(-1) for the Baltic Sea.

关键词： Physical Meteorology and Climatology Satellite observations observational techniques and algorithms Surface temperature Remote sensing Climate change Climate variability

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Evaporative and Radiative Cooling in POST Stratocumulus

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JOURNAL OF THE ATMOSPHERIC SCIENCES 2016年第10期73卷 3877-3884页

作者： Gerber, H. Malinowski, Szymon P. Jonsson, Haflidi Gerber Sci Inc 1643 Bentana Way Reston VA 20190 USA Univ Warsaw Warsaw Poland Naval Postgrad Sch Monterey CA USA

Buoyancy reversal by evaporative cooling in entrainment holes has a minimal influence on stratocumulus (Sc) observed during the Physics of Stratocumulus Top (POST) aircraft field study held off the California coast in 2008. High-resolution temperature and microphysics measurements show only small differences for Sc with and without buoyancy reversal predicted by mixing fraction analysis that relates mixtures of cloudy air and free-atmospheric air to buoyancies of the mixtures. The reduction of LWC due to evaporation in the holes is a small percentage (average similar to 12%) of liquid water diluted in the Sc by entrainment from the entrainment interface layer (EIL) located above unbroken cloud top where most mixing, evaporation, and reduction of the large buoyancy jump between the cloud and free atmosphere occur. Entrainment is dominated by radiative cooling at cloud top.

关键词： Circulation/ Dynamics Entrainment Physical Meteorology and Climatology Clouds observational techniques and algorithms Aircraft observations In situ atmospheric observations

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Development and Application of a Simplified Coplane Wind Retrieval Algorithm Using Dual-Beam Airborne Doppler Radar Observations for Tropical Cyclone Prediction

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MONTHLY WEATHER REVIEW 2016年第7期144卷 2645-2666页

作者： Melhauser, Christopher Zhang, Fuqing Penn State Univ Dept Meteorol 503 Walker Bldg University Pk PA 16802 USA Penn State Univ Ctr Adv Data Assimilat & Predictabil Tech University Pk PA 16802 USA

Based on established coplane methodology, a simplified three-dimensional wind retrieval algorithm is proposed to derive two-dimensional wind vectors from radial velocity observations by the tail Doppler radars on board the NOAA P3 hurricane reconnaissance aircraft. Validated against independent in situ flight-level and dropsonde observations before and after genesis of Hurricane Karl (2010), each component of the retrieved wind vectors near the aircraft track has an average error of approximately 1.5 ms(-1), which increases with the scanning angle and distance away from the aircraft track. Simulated radial velocities derived from a convection-permitting simulation of Karl are further used to systematically quantify errors of the simplified coplane algorithm. The accuracy of the algorithm is strongly dependent on the time between forward and backward radar scans and to a lesser extent, the zero vertical velocity assumption at large angles relative to a plane parallel with the aircraft wings. A proof-of-concept experiment assimilating the retrieved wind vectors with an ensemble Kalman filter shows improvements in track and intensity forecasts similar to assimilating radial velocity super observations or the horizontal wind vectors from the analysis retrievals provided by the Hurricane Research Division of NOAA. Future work is needed to systematically evaluate this simplified coplane algorithm with proper error characteristics for TC initialization and prediction through a large number of events to establish statistical significance.

关键词： Atm/Ocean Structure/ Phenomena Tropical cyclones observational techniques and algorithms Aircraft observations Data quality control Sensitivity studies Models and modeling Data assimilation

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ATDnet Detection Efficiency and Cloud Lightning Detection Characteristics from Comparison with the HyLMA during HyMeX SOP1

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第9期33卷 1899-1911页

作者： Enno, Sven-Erik Anderson, Graeme Sugier, Jacqueline Met Off FitzRoy Rd Exeter EX1 3PB Devon England

This study provides the first comprehensive quantitative detection efficiency (DE) estimation of the Met Office long-range very low-frequency (VLF) lightning location system, the Arrival Time Difference Network ATDnet, with a focus on cloud flash detection. ATDnet uses sensors in and around Europe to detect lightning in Europe, northern Africa, and northern parts of the Atlantic. In the present paper, ATDnet is validated against the Hydrological Cycle in the Mediterranean Experiment (HyMeX) Lightning Mapping Array (HyLMA) deployed in the south of France in autumn 2012 as a part of the HyMeX project Special Observation Period 1 (SOP1). Three storms (on 5, 11, and 25 September 2012) were selected for this study, as their activity was sufficient to provide good statistics but also low enough to avoid ambiguous situations due to temporally overlapping flashes. The overall ATDnet flash DE was approximately 89% for the 281 ground flashes [ cloud to ground (CG)] and 24% for the 1324 cloud flashes [inter/intracloud (IC)] during the storms. It was also demonstrated that variations in cloud flash characteristics (e.g., flash vertical extent) have a significant impact on DE between and during the studied storms.

关键词： Atm/Ocean Structure/ Phenomena Data quality control Lightning observational techniques and algorithms Remote sensing

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Rainfall-Type Categorization of Radar Echoes Using Polar Coordinate Reflectivity Data

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第3期33卷 523-538页

作者： Powell, Scott W. Houze, Robert A. Brodzik, Stella R. Univ Washington Dept Atmospher Sci Seattle WA 98195 USA

An algorithm used to classify precipitation echoes by rain type without interpolating radar data to a constant height is detailed. The method uses reflectivity data without clutter along the lowest available scan angle so that the classifications yield a more accurate representation of the rain type observed at the surface. The algorithm is based on that of Steiner et al. but is executed within a polar coordinate system. An additional procedure allows for more small, isolated, and/or weak echo objects to be appropriately identified as convective. Echoes in the immediate vicinity of convective cores are included in a new transition category, which consists mostly of echoes for which a convective or stratiform determination cannot be confidently made. The new algorithm more effectively identifies shallow convection embedded within large stratiform regions, correctly identifies isolated shallow and weak convection as such, and more often appropriately identifies periods during which no stratiform precipitation is present.

关键词： Physical Meteorology and Climatology observational techniques and algorithms Radars/Radar observations Convection Mesoscale processes Circulation/Dynamics

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Observations of the Structure and Evolution of Hurricane Edouard (2014) during Intensity Change. Part I: Relationship between the Thermodynamic Structure and Precipitation

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MONTHLY WEATHER REVIEW 2016年第9期144卷 3333-3354页

作者： Zawislak, Jonathan Jiang, Haiyan Alvey, George R., III Zipser, Edward J. Rogers, Robert F. Zhang, Jun A. Stevenson, Stephanie N. Florida Int Univ Miami FL 33199 USA Univ Utah Salt Lake City UT USA NOAA Atlantic Oceanog & Meteorol Lab Hurricane Res Div Miami FL 33149 USA Univ Miami Rosenstiel Sch Marine & Atmospher Sci Cooperat Inst Marine & Atmospher Studies 4600 Rickenbacker Causeway Miami FL 33149 USA SUNY Albany Albany NY 12222 USA

The structural evolution of the inner core and near environment throughout the life cycle of Hurricane Edouard (2014) is examined using a synthesis of airborne and satellite measurements. This study specifically focuses on the precipitation evolution and thermodynamic changes that occur on the vortex scale during four periods: when Edouard was a slowly intensifying tropical storm, another while a rapidly intensifying hurricane, during the initial stages of weakening after reaching peak intensity, and later while experiencing moderate weakening in the midlatitudes. Results suggest that, in a shear-relative framework, a wavenumber-1 asymmetry exists whereby the downshear quadrants consistently exhibit the greatest precipitation coverage and highest relative humidity, while the upshear quadrants (especially upshear right) exhibit relatively less precipitation coverage and lower humidity, particularly in the midtroposphere. Whether dynamically or precipitation driven, the relatively dry layers upshear appear to be ubiquitously caused by subsidence. The precipitation and thermodynamic asymmetry is observed throughout the intensification and later weakening stages, while a consistently more symmetric distribution is only observed when Edouard reaches peak intensity. The precipitation distribution, which is also discussed in the context of the boundary layer thermodynamic properties, is intimately linked to the thermodynamic symmetry, which becomes greater as the frequency, areal coverage, and, in particular, rainfall rate increases upshear. Although shear is generally believed to be detrimental to intensification, observations in Edouard also indicate that subsidence warming from mesoscale downdrafts in the low- to midtroposphere very near the center may have contributed favorably to organization early in the intensification stage.

关键词： Atm/Ocean Structure/ Phenomena Hurricanes/typhoons Precipitation Tropical cyclones Physical Meteorology and Climatology Thermodynamics observational techniques and algorithms Dropsondes Satellite observations

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