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On the Secondary Eyewall Formation of Hurricane Edouard (2014)

MONTHLY WEATHER REVIEW 2016年第9期144卷 3321-3331页

作者： Abarca, Sergio F. Montgomery, Michael T. Braun, Scott A. Dunion, Jason Natl Ocean & Atmospher Adm IM Syst Grp Natl Ctr Environm Protect Natl Weather Serv College Pk MD USA Naval Postgrad Sch Monterey CA USA NASA Goddard Space Flight Ctr Greenbelt MD USA Univ Miami Cooperat Inst Marine & Atmospher Studies Miami FL USA NOAA Atlantic Oceanog & Meteorol Lab Hurricane Res Div Miami FL 33149 USA

A first observationally based estimation of departures from gradient wind balance during secondary eyewall formation is presented. The study is based on the Atlantic Hurricane Edouard (2014). This storm was observed during the National Aeronautics and Space Administration's (NASA) Hurricane and Severe Storm Sentinel (HS3) experiment, a field campaign conducted in collaboration with the National Oceanic and Atmospheric Administration (NOAA). A total of 135 dropsondes are analyzed in two separate time periods: one named the secondary eyewall formation period and the other one referred to as the decaying double eyewalled storm period. During the secondary eyewall formation period, a time when the storm was observed to have only one eyewall, the diagnosed agradient force has a secondary maximum that coincides with the radial location of the secondary eyewall observed in the second period of study. The maximum spinup tendency of the radial influx of absolute vertical vorticity is within the boundary layer in the region of the eyewall of the storm and the spinup tendency structure elongates radially outward into the secondary region of supergradient wind, where the secondary wind maximum is observed in the second period of study. An analysis of the boundary layer averaged vertical structure of equivalent potential temperature reveals a conditionally unstable environment in the secondary eyewall formation region. These findings support the hypothesis that deep convective activity in this region contributed to spinup of the boundary layer tangential winds and the formation of a secondary eyewall that is observed during the decaying double eyewalled storm period.

关键词： Atm/Ocean Structure/ Phenomena Hurricanes/typhoons observational techniques and algorithms Dropsondes In situ atmospheric observations

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Experimental Assimilation of the GPM Core Observatory DPR Reflectivity Profiles for Typhoon Halong (2014)

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MONTHLY WEATHER REVIEW 2016年第6期144卷 2307-2326页

作者： Okamoto, Kozo Aonashi, Kazumasa Kubota, Takuji Tashima, Tomoko Japan Meteorol Agcy Meteorol Res Inst Tsukuba Ibaraki Japan Japan Aerosp Explorat Agcy Earth Observat Res Ctr Tsukuba Ibaraki Japan Remote Sensing Technol Ctr Japan Tsukuba Ibaraki Japan

Space-based precipitation radar data have been underused in data assimilation studies and operations despite their valuable information on vertically resolved hydrometeor profiles around the globe. The authors developed direct assimilation of reflectivities (Ze) from the Dual-Frequency Precipitation Radar (DPR) on board the Global Precipitation Measurement (GPM) Core Observatory to improve mesoscale predictions. Based on comparisons with Ze observations, this cloud resolving model mostly reproduced Ze but produced overestimations of Ze induced by excessive snow with large diameter particles. With an ensemble-based variational scheme and preprocessing steps to properly treat reflectivity observations including conservative quality control and superobbing procedures, the authors assimilated DPR Ze and/or rain-affected radiances of GPM Microwave Imager (GMI) for the case of Typhoon Halong in July 2014. With the vertically resolving capability of DPR, the authors effectively selected Ze observations most suited to data assimilation, for example, by removing Ze above the melting layer to avoid contamination due to model bias. While the GMI radiance had large impacts on various control variables, the DPR made a fine delicate analysis of the rain mixing ratio and updraft. This difference arose from the observation characteristics (coverage width and spatial resolution), sensitivities represented in the observation operators, and structures of the background error covariance. Because the DPR assimilation corrected excessive increases in rain and clouds due to the radiance assimilation, the combined use of DPR and GMI generated more accurate analysis and forecast than separate use of them with respect to the agreement of observations and tropical cyclone position errors.

关键词： observational techniques and algorithms Microwave observations Radars Radar observations Satellite observations Forecasting Numerical weather prediction forecasting Models and modeling Cloud resolving models Data assimilation

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All Sonic Anemometers Need to Correct for Transducer and Structural Shadowing in Their Velocity Measurements

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第1期33卷 149-167页

作者： Frank, John M. Massman, William J. Swiatek, Edward Zimmerman, Herb A. Ewers, Brent E. US Forest Serv Rocky Mt Res Stn 240 W Prospect Rd Ft Collins CO USA Univ Wyoming Dept Bot Laramie WY 82071 USA Univ Wyoming Program Ecol Laramie WY 82071 USA Campbell Sci Inc Logan UT USA Appl Technol Inc Longmont CO USA

Sonic anemometry is fundamental to all eddy-covariance studies of surface energy and ecosystem carbon and water balance. Recent studies have shown that some nonorthogonal anemometers underestimate vertical wind. Here it is hypothesized that this is due to a lack of transducer and structural shadowing correction. This is tested with a replicated intercomparison experiment between orthogonal (K-probe, Applied Technologies, Inc.) and nonorthogonal (A-probe, Applied Technologies, Inc.;and CSAT3 and CSAT3V, Campbell Scientific, Inc.) anemometer designs. For each of the 12 weeks, five randomly selected and located anemometers were mounted both vertically and horizontally. Bayesian analysis was used to test differences between half-hourly anemometer measurements of the standard deviation of wind (sigma(u), sigma(v), and sigma(w)) and temperature, turbulent kinetic energy (TKE), the ratio between vertical/horizontal TKE (VHTKE), and sensible heat flux (H). Datasets were analyzed with various applications of transducer shadow correction. Using the manufacturer's current recommendations, orthogonal anemometers partitioned higher VHTKE and measured about 8%-9% higher sigma(w) and similar to 10% higher H. This difference can be mitigated by adding shadow correction to nonorthogonal anemometers. The horizontal manipulation challenged each anemometer to measure the three dimensions consistently, which allowed for testing two hypotheses explaining the underestimate in vertical wind. While measurements were essentially unchanged when the orthogonal anemometers were mounted sideways, the nonorthogonal anemometers changed substantially and confirmed the lack of shadow correction. Considering the ubiquity of nonorthogonal anemometers, these results are consequential across flux networks and could potentially explain half of the similar to 20% missing energy that is typical at most flux sites.

关键词： Atm/Ocean Structure/ Phenomena Wind Physical Meteorology and Climatology Heat budgets/fluxes observational techniques and algorithms Instrumentation/sensors Mathematical and statistical techniques Bayesian methods

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Convective Initiation near the Andes in Subtropical South America

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MONTHLY WEATHER REVIEW 2016年第6期144卷 2351-2374页

作者： Rasmussen, K. L. Houze, R. A., Jr. Natl Ctr Atmospher Res Mesoscale & Microscale Meteorol Lab POB 3000 Boulder CO 80307 USA Univ Washington Dept Atmospher Sci Seattle WA 98195 USA

Satellite radar and radiometer data indicate that subtropical South America has some of the deepest and most extreme convective storms on Earth. This study uses the full 15-yr TRMM Precipitation Radar dataset in conjunction with high-resolution simulations from the Weather Research and Forecasting Model to better understand the physical factors that control the climatology of high-impact weather in subtropical South America. The occurrence of intense storms with an extreme horizontal dimension is generally associated with lee cyclogenesis and a strengthening South American low-level jet (SALLJ) in the La Plata basin. The orography of the Andes is critical, and model sensitivity calculations removing and/or reducing various topographic features indicate the orographic control on the initiation of convection and its upscale growth into mesoscale convective systems (MCSs). Reduced Andes experiments show more widespread convective initiation, weaker average storm intensity, and more rapid propagation of the MCS to the east (reminiscent of the MCS life cycle downstream of lower mountains such as the Rockies). With reduced Andes, lee cyclogenesis and SALLJ winds are weaker, while they are stronger in increased Andes runs. The presence of the Sierras de Cordoba (secondary mountain range east of the Andes in Argentina) focuses convective initiation and results in more intense storms in experiments with higher Andes. Average CAPE and CIN values for each terrain modification simulation show that reduced Andes runs had lower CIN and CAPE, while increased Andes runs had both stronger CAPE and CIN. From this research, a conceptual model for convective storm environments leading to convective initiation has been developed for subtropical South America.

关键词： Circulation Dynamics Convective storms Mesoscale systems Physical Meteorology and Climatology Orographic effects Storm environments observational techniques and algorithms Radars Radar observations Models and modeling Mesoscale models

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Impact of Assimilating Dropsonde Observations from MPEX on Ensemble Forecasts of Severe Weather Events

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MONTHLY WEATHER REVIEW 2016年第10期144卷 3799-3823页

作者： Romine, Glen S. Schwartz, Craig S. Torn, Ryan D. Weisman, Morris L. Natl Ctr Atmospher Res POB 3000 Boulder CO 80307 USA

Over the central Great Plains, mid- to upper-tropospheric weather disturbances often modulate severe storm development. These disturbances frequently pass over the Intermountain West region of the United States during the early morning hours preceding severe weather events. This region has fewer in situ observations of the atmospheric state compared with most other areas of the United States, contributing toward greater uncertainty in forecast initial conditions. Assimilation of supplemental observations is hypothesized to reduce initial condition uncertainty and improve forecasts of high-impact weather. During the spring of 2013, the Mesoscale Predictability Experiment (MPEX) leveraged ensemble-based targeting methods to key in on regions where enhanced observations might reduce mesoscale forecast uncertainty. Observations were obtained with dropsondes released from the NSF/NCAR Gulfstream-V aircraft during the early morning hours preceding 15 severe weather events over areas upstream from anticipated convection. Retrospective data-denial experiments are conducted to evaluate the value of dropsonde observations in improving convection-permitting ensemble forecasts. Results show considerable variation in forecast performance from assimilating dropsonde observations, with a modest but statistically significant improvement, akin to prior targeted observation studies that focused on synoptic-scale prediction. The change in forecast skill with dropsonde information was not sensitive to the skill of the control forecast. Events with large positive impact sampled both the disturbance and adjacent flow, akin to results from past synoptic-scale targeting studies, suggesting that sampling both the disturbance and adjacent flow is necessary regardless of the horizontal scale of the feature of interest.

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

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Multidecadal Change of the South Pacific Gyre Circulation

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JOURNAL OF PHYSICAL OCEANOGRAPHY 2016年第6期46卷 1871-1883页

作者： Roemmich, Dean Gilson, John Sutton, Philip Zilberman, Nathalie Univ Calif San Diego Scripps Inst Oceanog 9500 Gilman Dr La Jolla CA 92093 USA Natl Inst Water & Atmospher Res Wellington New Zealand

Multidecadal trends in ocean heat and freshwater content are well documented, but much less evidence exists of long-term changes in ocean circulation. Previously, a 12-yr increase, 1993 to 2004, in the circulation of the South Pacific Subtropical Gyre interior was described. That analysis was based on differences between early Argo and 1990s hydrographic data and changes in sea surface height. Here, it is shown that the trend of increasing circulation continues through 2014, with some differences within the Argo decade (2005 to 2014). Patterns that indicate or are consistent with increasing equatorward transport in the eastern portion of the South Pacific Gyre are seen in Argo temperature and steric height, Argo trajectory velocity, altimetric sea surface height, sea surface temperature, sea level pressure, and wind stress. Between 2005 and 2014 the geostrophic circulation across 35 degrees S, from 160 degrees W to South America, was enhanced by 5 Sv (1 Sv 10(6) m(3) s(-1)) of added northward flow. This was countered by a southward transport anomaly between the date line and 160 degrees W. Corresponding temperature trends span the full 2000-m depth range of Argo observations. The 22-yr trend, 1993 to 2014, in sea surface height at 35 degrees S, 160 degrees W is 8 cm decade(-1). Trends in sea surface temperature over 34 yr, 1981 to 2014, show a similar spatial pattern to that of sea surface height, with an increase of 0.5 degrees C decade(-1) at 35 degrees S, 160 degrees W. These multidecadal trends support the interpretation of the 40 degrees S maximum in global ocean heat gain as resulting from anomalous wind forcing and Ekman convergence.

关键词： Circulation Dynamics Atmosphere-ocean interaction Mass fluxes transport Ocean circulation observational techniques and algorithms In situ oceanic observations Profilers oceanic

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Subpixel Characterization of HIRS Spectral Radiances Using Cloud Properties from AVHRR

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第7期33卷 1519-1538页

作者： Staten, Paul W. Kahn, Brian H. Schreier, Mathias M. Heidinger, Andrew K. Indiana Univ 1001 E 10th St Bloomington IN 47405 USA CALTECH Jet Prop Lab NASA Pasadena CA USA NOAA NESDIS Ctr Satellite Applicat & Res Madison WI USA

This paper describes a cloud type radiance record derived from NOAA polar-orbiting weather satellites using cloud properties retrieved from the Advanced Very High Resolution Radiometer (AVHRR) and spectral brightness temperatures (Tb) observed by the High Resolution Infrared Radiation Sounder (HIRS). The authors seek to produce a seamless, global-scale, long-term record of cloud type and Tb statistics intended to better characterize clouds from seasonal to decadal time scales. Herein, the methodology is described in which the cloud type statistics retrieved from AVHRR are interpolated onto each HIRS footprint using two cloud classification methods. This approach is tested over the northeast tropical and subtropical Pacific Ocean region, which contains a wide variety of cloud types during a significant ENSO variation from 2008 to 2009. It is shown that the Tb histograms sorted by cloud type are realistic for all HIRS channels. The magnitude of Tb biases among spatially coincident satellite intersections over the northeast Pacific is a function of cloud type and wavelength. While the sign of the bias can change, the magnitudes are generally small for NOAA-18 and NOAA-19, and NOAA-19 and MetOp-A intersections. The authors further show that the differences between calculated standard deviations of cloud-typed Tb well exceed intersatellite calibration uncertainties. The authors argue that consideration of higher-order statistical moments determined from spectral infrared observations may serve as a useful long-term measure of small-scale spatial changes, in particular cloud types over the HIRS-AVHRR observing record.

关键词： Atm/Ocean Structure/ Phenomena Climate change Climate records Clouds ENSO observational techniques and algorithms Physical Meteorology and Climatology Remote sensing Satellite observations

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Independent Benthic Microbial Fuel Cells Powering Sensors and Acoustic Communications with the MARS Underwater Observatory

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第3期33卷 607-617页

作者： Schrader, Paul S. Reimers, Clare E. Girguis, Peter Delaney, Jennifer Doolan, Cody Wolf, Michael Green, Dale Oregon State Univ Hatfield Marine Sci Ctr Coll Earth Ocean & Atmospher Sci 2030 SE Marine Sci Dr Newport OR 97365 USA Harvard Univ Biol Labs Cambridge MA 02138 USA Teledyne Benthos Inc N Falmouth MA USA

Most oceanographic instruments on the seafloor have no connections with the surface and therefore have to run on batteries and store data until recovery. To demonstrate a developing technology, sensors and acoustic modems were powered with energy harvested from the seafloor, and data were relayed acoustically in near-real time to the Monterey Accelerated Research System (MARS) observatory in Monterey Bay, California, and to surface research vessels. MARS is a cabled observatory in deep water (~890 m) at the edge of Monterey Canyon. An acoustic modem was attached to the MARS node and configured to send out commands to, and relay data received from, remote modems. Two benthic microbial fuel cells (BMFCs) positioned approximately 0.5 km away from MARS supplied power to the remote modems and sensors. At their peak performance, these BMFCs produced continuous power densities of ~35 mW m(-2) (footprint area). The modems utilized in this study contained an integrated power management platform (PMP) designed to manage and store the electrical energy generated by each BMFC and to record BMFC performance parameters and sensor data on an hourly basis. Temperature and either oxygen or conductivity sensors were chosen because of their common use and environmental relevance. Acoustically transmitted data records show that the BMFCs renewed energy stores and that the oceanographic sensors measured dissolved oxygen, temperature, and conductivity reliably throughout the operational life of each BMFC system (~6 months). These systems remained in place for more than 12 months.

关键词： observational techniques and algorithms Remote sensing Field experiments Instrumentation/sensors Surface observations Ship observations Renewable energy Applications

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Stratospheric Gravity Wave Fluxes and Scales during DEEPWAVE

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JOURNAL OF THE ATMOSPHERIC SCIENCES 2016年第7期73卷 2851-2869页

作者： Smith, Ronald B. Nugent, Alison D. Kruse, Christopher G. Fritts, David C. Doyle, James D. Eckermann, Steven D. Taylor, Michael J. Doernbrack, Andreas Uddstrom, M. Cooper, William Romashkin, Pavel Jensen, Jorgen Beaton, Stuart Yale Univ Dept Geol & Geophys POB 208109 New Haven CT 06520 USA GATS Boulder CO USA Naval Res Lab Monterey CA USA Naval Res Lab Washington DC 20375 USA Utah State Univ Logan UT 84322 USA German Aerosp Ctr DLR Oberpfaffenhofen Germany Natl Inst Water & Atmospher Res Wellington New Zealand Natl Ctr Atmospher Res POB 3000 Boulder CO 80307 USA

During the Deep Propagating Gravity Wave Experiment (DEEPWAVE) project in June and July 2014, the Gulfstream V research aircraft flew 97 legs over the Southern Alps of New Zealand and 150 legs over the Tasman Sea and Southern Ocean, mostly in the low stratosphere at 12.1-km altitude. Improved instrument calibration, redundant sensors, longer flight legs, energy flux estimation, and scale analysis revealed several new gravity wave properties. Over the sea, flight-level wave fluxes mostly fell below the detection threshold. Over terrain, disturbances had characteristic mountain wave attributes of positive vertical energy flux (EFz), negative zonal momentum flux, and upwind horizontal energy flux. In some cases, the fluxes changed rapidly within an 8-h flight, even though environmental conditions were nearly unchanged. The largest observed zonal momentum and vertical energy fluxes were MFx = -550 mPa and EFz = 22W m(-2), respectively. A wide variety of disturbance scales were found at flight level over New Zealand. The vertical wind variance at flight level was dominated by short "fluxless'' waves with wavelengths in the 6-15-km range. Even shorter scales, down to 500 m, were found in wave breaking regions. The wavelength of the flux-carrying mountain waves was much longer-mostly between 60 and 150 km. In the strong cases, however, with EFz > 4W m(-2), the dominant flux wavelength decreased (i.e., "downshifted'') to an intermediate wavelength between 20 and 60 km. Apotential explanation for the rapid flux changes and the scale "downshifting'' is that low-level flow can shift between "terrain following'' and "envelope following'' associated with trapped air in steep New Zealand valleys.

关键词： Circulation/ Dynamics Gravity waves Mountain waves Waves atmospheric observational techniques and algorithms Aircraft observations In situ atmospheric observations

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Estimation of Volcanic Ash Emissions Using Trajectory-Based 4D-Var Data Assimilation

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MONTHLY WEATHER REVIEW 2016年第2期144卷 575-589页

作者： Lu, S. Lin, H. X. Heemink, A. W. Fu, G. Segers, A. J. Delft Univ Technol Mekelweg 4 NL-2628 CD Delft Netherlands TNO Dept Climate Air & Sustainabil Utrecht Netherlands

Volcanic ash forecasting is a crucial tool in hazard assessment and operational volcano monitoring. Emission parameters such as plume height, total emission mass, and vertical distribution of the emission plume rate are essential and important in the implementation of volcanic ash models. Therefore, estimation of emission parameters using available observations through data assimilation could help to increase the accuracy of forecasts and provide reliable advisory information. This paper focuses on the use of satellite total-ash-column data in 4D-Var based assimilations. Experiments show that it is very difficult to estimate the vertical distribution of effective volcanic ash injection rates from satellite-observed ash columns using a standard 4D-Var assimilation approach. This paper addresses the ill-posed nature of the assimilation problem from the perspective of a spurious relationship. To reduce the influence of a spurious relationship created by a radiate observation operator, an adjoint-free trajectory-based 4D-Var assimilation method is proposed, which is more accurate to estimate the vertical profile of volcanic ash from volcanic eruptions. The method seeks the optimal vertical distribution of emission rates of a reformulated cost function that computes the total difference between simulated and observed ash columns. A 3D simplified aerosol transport model and synthetic satellite observations are used to compare the results of both the standard method and the new method.

关键词： observational techniques and algorithms Satellite observations Mathematical and statistical techniques Optimization Variational analysis Models and modeling Data assimilation Applications Air pollution

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