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"Deep-Arvor": A New Profiling Float to Extend the Argo Observations Down to 4000-m Depth

JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第5期33卷 1039-1055页

作者： Le Reste, Serge Dutreuil, Vincent Andre, Xavier Thierry, Virginie Renaut, Corentin Le Traon, Pierre-Yves Maze, Guillaume IFREMER Brest France IFREMER Lab Oceanog Phys & Spatiale F-29280 Plouzane France

The international Argo program, consisting of a global array of more than 3000 free-drifting profiling floats, has now been monitoring the upper 2000m of the ocean for several years. One of its main proposed evolutions is to be able to reach the deeper ocean in order to better observe and understand the key role of the deep ocean in the climate system. For this purpose, Ifremer has designed the new "Deep-Arvor" profiling float: it extends the current operational depth down to 4000 m, and measures temperature and salinity for up to 150 cycles with CTD pumping continuously and 200 cycles in spot sampling mode. High-resolution profiles (up to 2000 points) can be transmitted and data are delivered in near-real time according to Argo requirements. Deep-Arvor can be deployed everywhere at sea without any preballasting operation and its light weight (;26 kg) makes its launching easy. Its design was done to target a cost-effective solution. Predefined spots have been allocated to add an optional oxygen sensor and a connector for an extra sensor. Extensive laboratory tests were successful. The results of the first at-sea experiments showed that the expected performances of the operational prototypes had been reached (i.e., to perform up to 150 cycles). Meanwhile, the industrialization phase was completed in order to manufacture the Deep-Arvor float for the pilot experiment in 2015. This paper details all the steps of the development work and presents the results from the at-sea experiments.

关键词： Atmosphere-ocean interaction Energy budget/balance Heating In situ oceanic observations Instrumentation/sensors observational techniques and algorithms Physical Meteorology and Climatology Profilers, oceanic

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Eddy Phase Speeds in a Two-Layer Model of Quasigeostrophic Baroclinic Turbulence with Applications to Ocean Observations

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JOURNAL OF PHYSICAL OCEANOGRAPHY 2016年第6期46卷 1963-1985页

作者： Wang, Lei Jansen, Malte Abernathey, Ryan Univ Chicago Chicago IL 60637 USA Columbia Univ New York NY USA

The phase speed spectrum of ocean mesoscale eddies is fundamental to understanding turbulent baroclinic flows. Since eddy phase propagation has been shown to modulate eddy fluxes, an understanding of eddy phase speeds is also of practical importance for the development of improved eddy parameterizations for coarse resolution ocean models. However, it is not totally clear whether and how linear Rossby wave theory can be used to explain the phase speed spectra in various weakly turbulent flow regimes. Using linear analysis, theoretical constraints are identified that control the eddy phase speed in a two-layer quasigeostrophic (QG) model. These constraints are then verified in a series of nonlinear two-layer QG simulations, spanning a range of parameters with potential relevance to the ocean. In the two-layer QG model, the strength of the inverse cascade exerts an important control on the eddy phase speed. If the inverse cascade is weak, the phase speed spectrum is reasonably well approximated by the phase speed of the linearly most unstable mode. A significant inverse cascade instead leads to barotropization, which in turn leads to mean phase speeds closer to those of barotropic-mode Rossby waves. The two-layer QG results are qualitatively consistent with the observed eddy phase speed spectra in the Antarctic Circumpolar Current and may also shed light on the interpretation of phase speed spectra observed in other regions.

关键词： Circulation/ Dynamics Baroclinic flows Eddies Mesoscale processes Potential vorticity observational techniques and algorithms Satellite observations Models and modeling Quasigeostrophic models

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Analysis of Mesoscale Atmospheric Flows above Mature Deep Convection Using Super Rapid Scan Geostationary Satellite Data

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JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY 2016年第9期55卷 1859-1887页

作者： Apke, Jason M. Mecikalski, John R. Jewett, Christopher P. Univ Alabama Huntsville Dept Atmospher Sci Huntsville AL USA Univ Alabama Huntsville Ctr Earth Syst Sci Huntsville AL USA

Super Rapid Scan Operations for the Geostationary Operational Environmental Satellite (GOES) R series (SRSOR) using GOES-14 have made experimentation with 1-min time-step data possible prior to the launch of the new satellite. A mesoscale atmospheric motion vector (mAMV) program is utilized in SRSOR with a Barnes analysis to produce objectively analyzed flow fields at the cloud tops of deep convection. Two non-supercell and four supercell storm cases are analyzed. Data from the SRSOR mAMV analysis are compared with both multi-Doppler analyses when available and idealized convection cases within the Weather Research and Forecasting (WRF) Model framework. It is found that using SRSOR data provides several additional trackable targets to produce mAMVs in rapidly "bubbling'' regions at the deep convective cloud-top level not previously available at lower temporal resolutions (, 1 min). Results also show that supercell storm cases produce long-lived maxima in SRSOR cloud-top divergence (CTD) and "couplet'' signatures in cloud-top vorticity (CTV), which when compared with idealized WRF Model simulations appear to form as a result of environmental horizontal vorticity tilting. Nonsupercell convection in contrast produced weaker, short-lived CTD signatures and no "CTV couplet'' signatures. These case study results suggest that with SRSOR data it might be possible to uniquely identify supercells using only mAMV-derived flow fields.

关键词： Circulation/ Dynamics Convective storms Mesoscale processes Atm/Ocean Structure/ Phenomena Convective clouds Supercells observational techniques and algorithms Cloud tracking/cloud motion winds Satellite observations

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Stationary Sea Surface Height Anomalies in Cyclonic Boundary Currents: Conservation of Potential Vorticity and Deviations from Strict Topographic Steering

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JOURNAL OF PHYSICAL OCEANOGRAPHY 2016年第8期46卷 2437-2456页

作者： Broome, Sara Nilsson, Johan Stockholm Univ Stockholm Sweden

In high-latitude subpolar seas, such as the Nordic seas and the Labrador Sea, time-mean geostrophic currents mediate the bulk of the meridional oceanic heat transport. These currents are primarily encountered along the continental slopes as intense cyclonic boundary currents, which, because of the relatively weak stratification, should be strongly steered by the bottom topography. However, analyses of hydrographic and satellite altimetric data along depth contours in Nordic seas boundary currents reveal some remarkable, stationary, along-stream variations in the depth-integrated buoyancy and bottom pressure. A closer examination shows that these variations are linked to changes in steepness and curvature of the continental slope. To examine the underlying dynamics, a steady-state model of a cyclonic stratified boundary current over a topographic slope is developed in the limit of small Rossby numbers. Based on potential vorticity conservation, equations for the zeroth-and first-order pressure and buoyancy fields are derived. To the lowest order, the flow is completely aligned with the bottom topography. However, the first-order results show that where the lowest-order flow increases (decreases) its relative vorticity along a depth contour, the first-order pressure and depthintegrated buoyancy increase (decrease). This response is associated with cross-isobath flows, which induce stretching/compression of fluid elements that compensates for the changes in relative vorticity. The model-predicted along-isobath variations in pressure and depth-integrated buoyancy are comparable in magnitude to the ones found in the observational data from the Nordics Seas.

关键词： Circulation/ Dynamics Barotropic flows Boundary currents Buoyancy Potential vorticity Topographic effects observational techniques and algorithms Satellite observations

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Assimilating Retrievals of Sea Surface Temperature from VIIRS and AMSR2

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第2期33卷 361-375页

作者： Brasnett, Bruce Colan, Dorina Surcel Environm & Climate Change Canada Meteorol Serv Canada Natl Predict Dev Div Dorval PQ Canada

Experiments are carried out to assess the potential contributions of two new satellite datasets, derived from the Visible Infrared Imaging Radiometer Suite (VIIRS) on board the Suomi-National Polar-Orbiting Partnership satellite and the Advanced Microwave Scanning Radiometer 2 (AMSR2) on board the Global Change Observation Mission-Water (GCOM-W) satellite, to the quality of global sea surface temperature (SST) analyses at the Canadian Meteorological Centre (CMC). The new datasets are assimilated both separately and together. Verification of the analyses against independent data shows that the VIIRS and AMSR2 datasets yield analyses with similar global average errors, with the VIIRS analysis performing better during some seasons and the AMSR2 analysis performing better in others. Seasonal cloudiness in some regions diminishes the availability of VIIRS retrievals, resulting in better performance by the AMSR2 analysis. Both datasets were assimilated together along with data from the Advanced Very High Resolution Radiometer (AVHRR), ice data, and in situ data in an updated version of the CMC analysis produced on a 0.1 degrees grid. Verification against independent data shows that the new analysis performed very well, with global average standard deviation consistently better than that of the international Group for High Resolution SST (GHRSST) Multiproduct Ensemble (GMPE) real-time system. This analysis is shown to outperform the currently operational CMC SST analysis, with most of the improvement being due to its assimilation of the VIIRS and AMSR2 retrievals and a further small gain being due to changes to the analysis methodology (including higher resolution).

关键词： observational techniques and algorithms Satellite observations Atm/Ocean Structure/ Phenomena Sea surface temperature

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Intercomparison of Unmanned Aircraftborne and Mobile Mesonet Atmospheric Sensors

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第8期33卷 1569-1582页

作者： Houston, Adam L. Laurence, Roger J., III Nichols, Tevis W. Waugh, Sean Argrow, Brian Ziegler, Conrad L. Univ Nebraska Dept Earth & Atmospher Sci 214 Bessey Hall Lincoln NE 68588 USA Univ Colorado Dept Aerosp Engn Sci Boulder CO 80309 USA Univ Oklahoma Cooperat Inst Mesoscale Meteorol Studies Norman OK 73019 USA NOAA Natl Severe Storms Lab Norman OK 73069 USA

Results are presented from an intercomparison of temperature, humidity, and wind velocity sensors of the Tempest unmanned aircraft system (UAS) and the National Severe Storms Laboratory (NSSL) mobile mesonet (NSSL-MM). Contemporaneous evaluation of sensor performance was facilitated by mounting the Tempest wing with attached sensors to the NSSL-MM instrument rack such that the Tempest and NSSL-MM sensors could collect observations within a nearly identical airstream. This intercomparison was complemented by wind tunnel simulations designed to evaluate the impact of the mobile mesonet vehicle on the observed wind velocity. The intercomparison revealed strong correspondence between the temperature and relative humidity (RH) data collected by the Tempest and the NSSL-MM with differences generally within sensor accuracies. Larger RH differences were noted in the presence of heavy precipitation;however, despite the exposure of the Tempest temperature and humidity sensor to the airstream, there was no evidence of wet bulbing within precipitation. Wind tunnel simulations revealed that the simulated winds at the location of the NSSL-MM wind monitor were similar to 4% larger than the expected winds due to the acceleration of the flow over the vehicle. Simulated vertical velocity exceeded 1 m s(-1) for tunnel inlet speeds typical of a vehicle moving at highway speeds. However, the theoretical noncosine reduction in winds that should result from the impact of vertical velocity on the laterally mounted wind monitor was found to be negligible across the simulations. Comparison of the simulated and observed results indicates a close correspondence, provided the crosswind component of the flow is small.

关键词： Data quality control In situ atmospheric observations observational techniques and algorithms

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Reconstructability of Three-Dimensional Upper-Ocean Circulation from SWOT Sea Surface Height Measurements

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JOURNAL OF PHYSICAL OCEANOGRAPHY 2016年第3期46卷 947-963页

作者： Qiu, B. Chen, Shuiming Klein, Patrice Ubelmann, Clement Fu, Lee-Lueng Sasaki, Hideharu Univ Hawaii Manoa Dept Oceanog 1000 Pope Rd Honolulu HI 96822 USA Ifremer CNRS UBO IRD Lab Phys Oceans Plouzane France CALTECH Jet Prop Lab Pasadena CA USA JAMSTEC Applicat Lab Yokohama Kanagawa Japan

Utilizing the framework of effective surface quasigeostrophic (eSQG) theory, this study explores the potential of reconstructing the 3D upper-ocean circulation structures, including the balanced vertical velocity w field, from high-resolution sea surface height (SSH) data of the planned Surface Water and Ocean Topography (SWOT) satellite mission. Specifically, the authors utilize the 1/30 degrees, submesoscale-resolving, OFES model output and subject it to the SWOT simulator that generates the along-swath SSH data with expected measurement errors. Focusing on the Kuroshio Extension region in the North Pacific where regional Rossby numbers range from 0.22 to 0.32, this study finds that the eSQG dynamics constitute an effective framework for reconstructing the 3D upper-ocean circulation field. Using the modeled SSH data as input, the eSQG-reconstructed relative vorticity zeta and w fields are found to reach a correlation of 0.7-0.9 and 0.6-0.7, respectively, in the 1000-m upper ocean when compared to the original model output. Degradation due to the SWOT sampling and measurement errors in the input SSH data for the zeta and w reconstructions is found to be moderate, 5%-25% for the 3D zeta field and 15%-35% for the 3D w field. There exists a tendency for this degradation ratio to decrease in regions where the regional eddy variability (or Rossby number) increases.

关键词： Variability Models and modeling General circulation models Vertical motion Circulation/ Dynamics Quasigeostrophic models Mesoscale processes observational techniques and algorithms Oceanic variability Altimetry

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New Statistical Model for Variability of Aerosol Optical Thickness: Theory and Application to MODIS Data over Ocean

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JOURNAL OF THE ATMOSPHERIC SCIENCES 2016年第2期73卷 821-837页

作者： Alexandrov, Mikhail D. Geogdzhayev, Igor V. Tsigaridis, Kostas Marshak, Alexander Levy, Robert Cairns, Brian Columbia Univ Dept Appl Phys & Appl Math New York NY USA NASA Goddard Inst Space Studies 2880 Broadway New York NY 10025 USA Columbia Univ Ctr Climate Syst Res New York NY USA NASA Goddard Space Flight Ctr Greenbelt MD USA

A novel model for the variability in aerosol optical thickness (AOT) is presented. This model is based on the consideration of AOT fields as realizations of a stochastic process that is the exponent of an underlying Gaussian process with a specific autocorrelation function. In this approach, AOT fields have lognormal PDFs and structure functions with the correct asymptotic behavior at large scales. The latter is an advantage compared with fractal (scale invariant) approaches. The simple analytical form of the structure function in the proposed model facilitates its use for the parameterization of AOT statistics derived from remote sensing data. The new approach is illustrated using a 1-yr-long global MODISAOT dataset (over ocean) with 10-km resolution. It was used to compute AOT statistics for sample cells forming a grid with 58 spacing. The observed shapes of the structure functions indicated that, in a large number of cases, the AOT variability is split into two regimes that exhibit different patterns of behavior: small-scale stationary processes and trends reflecting variations at larger scales. The small-scale patterns are suggested to be generated by local aerosols within the marine boundary layer, while the large-scale trends are indicative of elevated aerosols transported from remote continental sources. This assumption is evaluated by comparison of the geographical distributions of these patterns derived from MODIS data with those obtained from the GISS GCM. This study shows considerable potential to enhance comparisons between remote sensing datasets and climate models beyond regional mean AOTs.

关键词： Physical Meteorology and Climatology Aerosols observational techniques and algorithms Satellite observations Mathematical and statistical techniques Statistical techniques Models and modeling Climate models

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Observed Signatures of the Barotropic and Baroclinic Annular Modes in Cloud Vertical Structure and Cloud Radiative Effects

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JOURNAL OF CLIMATE 2016年第13期29卷 4723-4740页

作者： Li, Ying Thompson, David W. J. Colorado State Univ Dept Atmospher Sci 3915 W Laporte Ave Ft Collins CO 80521 USA

The signatures of large-scale annular variability on the vertical structure of clouds and cloud radiative effects are examined in vertically resolved CloudSat and other satellite and reanalysis data products. The northern and southern "barotropic' annular modes (the NAM and SAM) have a complex vertical structure. Both are associated with a meridional dipole in clouds between subpolar and middle latitudes, but the sign of the anomalies changes between upper, middle, and lower tropospheric levels. In contrast, the northern and southern baroclinic annular modes have a much simpler vertical structure. Both are linked to same-signed anomalies in clouds extending throughout the troposphere at middle to high latitudes. The changes in cloud incidence associated with both the barotropic and baroclinic annular modes are consistent with dynamical forcing by the attendant changes in static stability and/or vertical motion. The results also provide the first observational estimates of the vertically resolved atmospheric cloud radiative effects associated with hemispheric-scale extratropical variability. In general, the anomalies in atmospheric cloud radiative effects associated with the annular modes peak in the middle to upper troposphere, and are consistent with the anomalous trapping of longwave radiation by variations in upper tropospheric clouds. The southern baroclinic annular mode gives rise to periodic behavior in longwave cloud radiative effects at the top of the atmosphere averaged over Southern Hemisphere midlatitudes.

关键词： Circulation/ Dynamics Annular mode Clouds Physical Meteorology and Climatology Climate variability Cloud radiative effects observational techniques and algorithms Satellite observations

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Comparison of Meteorological Radar Signal Detectability with Noncoherent and Spectral-Based Processing

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第4期33卷 723-739页

作者： Mead, James B. ProSensing Inc 107 Sunderland Rd Amherst MA 01002 USA

Detection of meteorological radar signals is often carried out using power averaging with noise subtraction either in the time domain or the spectral domain. This paper considers the relative signal processing gain of these two methods, showing a clear advantage for spectral-domain processing when normalized spectral width is less than similar to 0.1. A simple expression for the optimal discrete Fourier transform (DFT) length to maximize signal processing gain is presented that depends only on the normalized spectral width and the time-domain weighting function. The relative signal processing gain between noncoherent power averaging and spectral processing is found to depend on a variety of parameters, including the radar wavelength, spectral width, available observation time, and the false alarm rate. Expressions presented for the probability of detection for noncoherent and spectral-based processing also depend on these same parameters. Results of this analysis show that DFT-based processing can provide a substantial advantage in signal processing gain and probability of detection, especially when the normalized spectral width is small and when a large number of samples are available. Noncoherent power estimation can provide superior probability of detection when the normalized spectral width is greater than similar to 0.1, especially when the desired false alarm rate exceeds 10%.

关键词： observational techniques and algorithms Data processing Radars/Radar observations

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