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An Assessment of the Flux Profile Method for Determining Air-Sea Momentum and Enthalpy Fluxes from Dropsonde Data in Tropical Cyclones

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JOURNAL OF THE ATMOSPHERIC SCIENCES 2016年第7期73卷 2665-2682页

作者： Richter, David H. Bohac, Rachel Stern, Daniel P. Univ Notre Dame Dept Civil & Environm Engn & Earth Sci Notre Dame IN 46556 USA Univ Corp Atmospher Res Monterey CA USA

An analysis of the reliability of using dropsonde profile data to compute surface flux coefficients of momentum and heat is performed. Monin-Obukhov (MO) similarity theory forms the basis for the flux profile method, where mean profiles of momentum, temperature, and moisture are used to estimate surface fluxes, from which bulk flux coefficients can then be determined given surface conditions. The robustness of this method is studied in terms of its sensitivity to internal, method-based parameters, as well as the uncertainty due to variability in the measurements and errors in the estimates of surface conditions, particularly sea surface temperature. In addition, "virtual sondes'' tracked through a high-resolution large-eddy simulation of an idealized tropical cyclone are used to evaluate the flux profile method's ability to recover known surface flux coefficients given known, prescribed surface conditions;this provides a test of whether or not MO assumptions are violated and under which regions they hold. Overall, it is determined that the flux profile method is only accurate within 50% and 200% for the drag coefficient C-D and enthalpy flux coefficient C-K, respectively, and thus is limited in its ability to quantitatively refine model estimates beyond typically used values. Factors such as proximity to the storm center can cause significant errors in both C-D and C-K.

关键词： Atm/Ocean Structure/ Phenomena Marine boundary layer Tropical cyclones Physical Meteorology and Climatology Atmosphere-ocean interaction Hurricanes/typhoons observational techniques and algorithms Dropsondes

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The Influence of African Easterly Waves on Convection over Tropical Africa and the East Atlantic

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MONTHLY WEATHER REVIEW 2016年第1期144卷 171-192页

作者： Janiga, Matthew A. Thorncroft, Chris D. Univ Miami Rosenstiel Sch Marine & Atmospher Sci 4600 Rickenbacker Causeway Miami FL 33149 USA SUNY Albany Albany NY 12222 USA

Using data from the Tropical Rainfall Measuring Mission (TRMM), the modulation of convection by African easterly waves (AEWs) is investigated over regions of the east Atlantic and tropical Africa. To explain the modulation of convection, the large-scale environment (lift, moisture, conditional instability, and shear) is also examined as a function of AEW phase in each *** semiarid portions of tropical Africa, unconditional rain rates are greatest in the northerly phase of AEWs due to the strong adiabatic forcing for ascent. Along the Guinea Coast, the western coast of Africa, and over the east Atlanticwhere forcing for ascent is weakerrainfall is shifted toward the trough where the air is moist. Significant contrasts in the characteristics of convection as a function of AEW phasecomparable in magnitude to regional contrastsare also observed. In all regions, large and high echo-top convective systems are more sensitive to AEW phase than small and low echo-top systems. In semiarid regions, deep convection and large high echo-top convective systems account for a large fraction of the rainfall in the ridge and northerlies. Stratiform and small low echo-top convective systems dominate in the trough and southerlies. Convective system height and conditional rain rates increase with conditional instability and system sizes may increase with shear. Over the east Atlantic, stratiform fractions and convective system sizes and echo-top heights are greatest in the trough while the ridge is dominated by shallow convection. This is primarily related to the presence of moist air in the trough and dry air in the ridge.

关键词： Geographic location entity Africa Circulation Dynamics Clouds Mesoscale systems Waves atmospheric observational techniques and algorithms Radars Radar observations Satellite observations

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Exploring Stratocumulus Cloud-Top Entrainment Processes and Parameterizations by Using Doppler Cloud Radar Observations

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JOURNAL OF THE ATMOSPHERIC SCIENCES 2016年第2期73卷 729-742页

作者： Albrecht, Bruce Fang, Ming Ghate, Virendra Univ Miami Rosenstiel Sch Marine & Atmospher Sci 4600 Rickenbacker Causeway Miami FL 33149 USA Argonne Natl Lab Div Environm Sci 9700 S Cass Ave Argonne IL 60439 USA

Observations made at the Atmospheric Radiation Measurement (ARM) Program's Southern Great Plains (SGP) site during uniform nonprecipitating stratocumulus cloud conditions for a 14-h period are used to examine cloud-top entrainment processes and parameterizations. The observations from a vertically pointing Doppler cloud radar provide estimates of vertical velocity variance and energy dissipation rate (EDR) terms in the parameterized turbulent kinetic energy (TKE) budget of the entrainment zone. Hourly averages of the vertical velocity variance term in the TKE entrainment formulation correlated strongly (r = 0.72) with the dissipation rate term in the entrainment zone, with an increased correlation (r = 0.92) when accounting for the nighttime decoupling of the boundary layer. Independent estimates of entrainment rates were obtained from an inversion-height budget using the local time derivative and horizontal advection of cloud-top height together with large-scale vertical velocity at the boundary layer inversion from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis model. The mean entrainment rate from the inversion-height budget during the 14-h period was 0.74 +/- 0.15 cm s(-1) and was used to calculate bulk coefficients for entrainment parameterizations based on convective velocity scale w* and TKE budgets of the entrainment zone. The hourly values of entrainment rates calculated using these coefficients exhibited good agreement with those calculated from the inversion-height budget associated with substantial changes in surface buoyancy production and cloud-top radiative cooling. The results indicate a strong potential for making entrainment rate estimates directly from radar vertical velocity variance and the EDR measurements.

关键词： Circulation/ Dynamics Entrainment Atm/Ocean Structure/ Phenomena Boundary layer Clouds observational techniques and algorithms Radars/Radar observations

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BASTA: A 95-GHz FMCW Doppler Radar for Cloud and Fog Studies

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第5期33卷 1023-1038页

作者： Delanoe, Julien Protat, Alain Vinson, Jean-Paul Brett, Williams Caudoux, Christophe Bertrand, Fabrice du Chatelet, Jacques Parent Hallali, Ruben Barthes, Laurent Haeffelin, Martial Dupont, Jean-Charles UPMC CNRS UVSQ Lab AtmospheresMilieuxObservat Spatiales Guyancourt France Australian Bur Meteorol Melbourne Vic Australia Ctr Natl Rech Meteorol Toulouse France Inst Pierre Simon Lapl Palaiseau France

Doppler cloud radars are amazing tools to characterize cloud and fog properties and to improve their representation in models. However, commercially available cloud radars (35 and 95GHz) are still very expensive, which hinders their widespread deployment. This study presents the development of a lower-cost semioperational 95-GHz Doppler cloud radar called the Bistatic Radar System for Atmospheric Studies (BASTA). To drastically reduce the cost of the instrument, a different approach is used compared to traditional pulsed radars: instead of transmitting a large amount of energy for a very short time period (as a pulse), a lower amount of energy is transmitted continuously. By using a specific signal processing technique, the radar can challenge expensive radars and provide high-quality measurements of cloud and fog. The latest version of the instrument has a sensitivity of about 250 dBZ at 1 km for 3-s integration and a vertical resolution of 25 m. The BASTA radar currently uses four successive modes for specific applications: the 12.5-m vertical resolution mode is dedicated to fog and low clouds, the 25-m mode is for liquid and ice midtropospheric clouds, and the 100- and 200-m modes are ideal for optically thin high-level ice clouds. The advantages of such a radar for calibration procedures and field operations are also highlighted. The radar comes with a set of products dedicated to cloud and fog studies. For instance, cloud mask, corrected Doppler velocity, and multimode products combining the high-sensitivity mode and high-resolution modes are provided.

关键词： Cloud microphysics Cloud retrieval Clouds Ice crystals Ice particles observational techniques and algorithms Physical Meteorology and Climatology Radars/Radar observations

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The Rapid Intensification of Hurricane Karl (2010): New Remote Sensing Observations of Convective Bursts from the Global Hawk Platform

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JOURNAL OF THE ATMOSPHERIC SCIENCES 2016年第9期73卷 3617-3639页

作者： Guimond, Stephen R. Heymsfield, Gerald M. Reasor, Paul D. Didlake, Anthony C., Jr. Univ Maryland Earth Syst Sci Interdisciplinary Ctr College Pk MD 20742 USA NASA Goddard Space Flight Ctr Code 612 Greenbelt MD 20771 USA NOAA Atlantic Oceanog & Meteorol Lab Hurricane Res Div Miami FL 33149 USA Oak Ridge Associated Univ Oak Ridge TN USA

The evolution of rapidly intensifying Hurricane Karl (2010) is examined from a suite of remote sensing observations during the NASA Genesis and Rapid Intensification Processes (GRIP) field experiment. The novelties of this study are in the analysis of data from the airborne Doppler radar High-Altitude Imaging Wind and Rain Airborne Profiler (HI WRAP) and the new Global Hawk airborne platform that allows long endurance sampling of hurricanes. Supporting data from the High-Altitude Monolithic Microwave Integrated Circuit (MMIC) Sounding Radiometer (HAMSR) microwave sounder coincident with HIWRAP and coordinated flights with the NOAA WP-3D aircraft help to provide a comprehensive understanding of the storm. The focus of the analysis is on documenting and understanding the structure, evolution, and role of small-scale deep convective forcing in the storm intensification process. Deep convective bursts are sporadically initiated in the downshear quadrants of the storm and rotate into the upshear quadrants for a period of similar to 12 h during the rapid intensification. The aircraft data analysis indicates that the bursts are being formed and maintained through a combination of two main processes: 1) convergence generated from counterrotating mesovortex circulations and the larger vortex-scale flow and 2) the turbulent (scales of similar to 25 km) transport of anomalously warm, buoyant air from the eye to the eyewall at low levels. The turbulent mixing across the eyewall interface and forced convective descent adjacent to the bursts assists in carving out the eye of Karl, which leads to an asymmetric enhancement of the warm core. The mesovortices play a key role in the evolution of the features described above. The Global Hawk aircraft allowed an examination of the vortex response and axisymmetrization period in addition to the burst pulsing phase. A pronounced axisymmetric development of the vortex is observed following the pulsing phase that includes a sloped eyewall s

关键词： Circulation/ Dynamics Hurricanes Mesoscale processes Turbulence Physical Meteorology and Climatology Convective-scale processes Vorticity observational techniques and algorithms Radars/Radar observations

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High-Resolution Seafloor Absolute Pressure Gauge Measurements Using a Better Counting Method

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第9期33卷 1859-1874页

作者： Webb, Spahr C. Nooner, Scott L. Columbia Univ Lamont Doherty Earth Observ 61 Route 9W Palisades NY 10964 USA Univ North Carolina Wilmington Dept Geog & Geol Wilmington NC USA

Vibrating quartz force transducers are the critical component of most deep-sea pressure and depth gauges in use in oceanography, producing a frequency output that varies with pressure. Accurate and low drift pressure measurements can be obtained by precisely measuring this frequency. In most implementations, the frequency is determined by counting the number of cycles of a high-frequency standard oscillator occurring during a large number of cycles of the lower-frequency quartz force oscillator. Resolution is limited by the sampling interval (length of counting) and the frequency of the frequency standard. Alternative counting methods can provide significant (20-40 dB) improvements in resolution at sampling rates above 1Hz. Each counting method can be described as a different filter applied to the output of a counter of the frequency standard gated at each transition of the transducer quartz oscillator. Improvements in resolution can be understood as the result of minimizing the aliasing of higher-frequency counting noise into the spectrum below the Nyquist frequency. A simple multipole infinite impulse response (IIR) filter designed to limit spectral leakage of high-frequency noise minimizes the noise spectrum and thereby optimizes the resolution of the pressure output. The resultant noise spectrum rises as frequency squared above 1Hz, independent of the sampling rate. At frequencies below 1 Hz, it is limited by noise in the electronics driving the force transducer quartz oscillator. Resolution increases with frequency of the frequency standard up to about 200 MHz, plateauing for higher frequencies due to other noise sources (likely electronic).

关键词： Circulation/Dynamics Waves, oceanic Atm/Ocean Structure/Phenomena Tides observational techniques and algorithms In situ oceanic observations Instrumentation/sensors

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Use of Geostationary Super Rapid Scan Satellite Imagery by the Storm Prediction Center

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WEATHER AND FORECASTING 2016年第2期31卷 483-494页

作者： Line, William E. Schmit, Timothy J. Lindsey, Daniel T. Goodman, Steven J. Univ Oklahoma Cooperat Inst Mesoscale Meteorol Studies Norman OK 73019 USA NOAA NWS NCEP Storm Predict Ctr 120 David L Boren Blvd Norman OK 73072 USA NOAA NESDIS Ctr Satellite Applicat & Res Adv Satellite Prod Branch Madison WI USA NOAA NESDIS Ctr Satellite Applicat & Res Reg & Mesoscale Meteorol Branch Ft Collins CO USA NOAA NESDIS GOES R Program Off Greenbelt MD USA

The Geostationary Operational Environmental Satellite-14 (GOES-14) Imager was operated by the National Oceanic and Atmospheric Administration (NOAA) in an experimental rapid scan 1-min mode during parts of 2012, 2013, 2014, and 2015. This scan mode, known as the Super Rapid Scan Operations for GOES-R (SRSOR), emulates the high-temporal-resolution sampling that will be provided by the Advanced Baseline Imager on the next-generation GOES-R series. NOAA/National Weather Service/Storm Prediction Center (SPC) forecasters utilized the 1-min imagery extensively in operations when available over convectively active regions. They found it provided them with unique insight into relevant features and processes before, during, and after convective initiation. This paper introduces how the SRSOR datasets from GOES-14 were used by SPC forecasters and how these data are likely to be applied when available operationally from GOES-R. Several animations, included as supplemental material, showcase the rapid change of severe weather related phenomena observed during the 2014 and 2015 SRSOR campaigns from the GOES-14 Imager.

关键词： Circulation/ Dynamics Convective storms/systems Atm/Ocean Structure/ Phenomena Severe storms observational techniques and algorithms Remote sensing Satellite observations Forecasting Nowcasting Operational forecasting

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On the Detection of Robust Multidecadal Changes in Earth's Outgoing Longwave Radiation Spectrum

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JOURNAL OF CLIMATE 2016年第13期29卷 4939-4947页

作者： Bantges, R. J. Brindley, H. E. Chen, X. H. Huang, X. L. Harries, J. E. Murray, J. E. Imperial Coll London London England NERC Natl Ctr Earth Observat London England Univ Michigan Ann Arbor MI 48109 USA

Differences between Earth's global mean all-sky outgoing longwave radiation spectrum as observed in 1970 [Interferometric Infrared Spectrometer (IRIS)], 1997 [Interferometric Monitor for Greenhouse Gases (IMG)], and 2012 [Infrared Atmospheric Sounding Instrument (IASI)] are presented. These differences are evaluated to determine whether these are robust signals of multidecadal radiative forcing and hence whether there is the potential for evaluating feedback-type responses. IASI-IRIS differences range from +2K in the atmospheric window (800-1000 cm(-1)) to -5.5K in the 1304 cm(-1) CH4 band center. Corresponding IASI-IMG differences are much smaller, at 0.2 and -0.8 K, respectively. More noticeably, IASI-IRIS differences show a distinct step change across the 1042 cm(-1) O-3 band that is not seen in IASI-IMG comparisons. This step change is a consequence of a difference in behavior when moving from colder to warmer scenes in the IRIS data compared to IASI and IMG. Matched simulations for the relevant periods using ERA reanalyses mimic the spectral behavior shown by IASI and IMG rather than by IRIS. These findings suggest that uncertainties in the spectral response of IRIS preclude the use of these data for quantitative assessments of forcing and feedback processes.

关键词： Physical Meteorology and Climatology Climate change Forcing Infrared radiation Radiative forcing observational techniques and algorithms Satellite observations Variability Climate variability

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Rates of Dissipation of Turbulent Kinetic Energy in a High Reynolds Number Tidal Channel

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第4期33卷 817-837页

作者： McMillan, Justine M. Hay, Alex E. Lueck, Rolf G. Wolk, Fabian Dalhousie Univ Dept Oceanog POB 15000 Halifax NS B3H 4R2 Canada Rockland Sci Inc Victoria BC Canada

The ability to estimate the rate of dissipation (a) of turbulent kinetic energy at middepth in a high-speed tidal channel using broadband acoustic Doppler current profilers (ADCPs) is assessed by making comparisons to direct measurements of a obtained using shear probes mounted on a streamlined underwater buoy. The investigation was carried out in Grand Passage, Nova Scotia, Canada, where the depth-averaged flow speed reached 2 m s(-1) and the Reynolds number was 8 x 10(7). The speed bin-averaged dissipation rates estimated from the ADCP data agree with the shear probe data to within a factor of 2. Both the ADCP and the shear probe measurements indicate a linear dependence of a on the cube of the flow speed during flood and much lower dissipation rates during ebb. The ebb-flood asymmetry and the small-scale intermittency in a are also apparent in the lognormal distributions of the shear probe data. Possible sources of bias and error in the a estimates are investigated, and the most likely causes of the discrepancy between the ADCP and shear probe estimates are the cross-channel separation of the instruments and the high degree of spatial variability that exists in the channel.

关键词： Acoustic measurements/effects Applications Atm/Ocean Structure/ Phenomena Boundary layer Circulation/ Dynamics Instrumentation/sensors observational techniques and algorithms Renewable energy Tides Turbulence

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An Investigation of the Goshen County, Wyoming, Tornadic Supercell of 5 June 2009 Using EnKF Assimilation of Mobile Mesonet and Radar Observations Collected during VORTEX2. Part II: Mesocyclone-Scale Processes Affecting Tornado Formation, Maintenance, and Decay

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MONTHLY WEATHER REVIEW 2016年第9期144卷 3441-3463页

作者： Marquis, James Richardson, Yvette Markowski, Paul Wurman, Joshua Kosiba, Karen Robinson, Paul Penn State Univ Dept Meteorol 503 Walker Bldg University Pk PA 16802 USA Ctr Severe Weather Res 1945 Vassar Cir Boulder CO 80305 USA

Storm-scale and mesocyclone-scale processes occurring contemporaneously with a tornado in the Goshen County, Wyoming, supercell observed on 5 June 2009 during the second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) are examined using ensemble analyses produced by assimilating mobile radar and in situ observations into a high-resolution convection-resolving model. This paper focuses on understanding the evolution of the vertical structure of the storm, the outflow buoyancy, and processes affecting the vertical vorticity and circulation within the mesocyclone that correspond to changes in observed tornado intensity. Tornadogenesis occurs when the low-level mesocyclone is least negatively buoyant relative to the environment, possesses its largest circulation, and is collocated with the largest azimuthally averaged convergence during the analysis period. The average buoyancy, circulation, and convergence within the near-surface mesocyclone (on spatial scales resolved by the model) all decrease as the tornado intensifies and matures. The tornado and its parent low-level mesocyclone both dissipate surrounded by a weakening rear-flank downdraft. The decreasing buoyancy of parcels within the low-level mesocyclone may partly be responsible for the weakening of the updraft surrounding the tornado and decoupling of the mid- and low-level circulation. Although the supply of horizontal vorticity generated in the forward flank of the storm increases throughout the life cycle of the tornado, it is presumably less easily tilted and stretched on the mesocyclone-scale during tornado maturity owing to the disruption of the low-level updraft/downdraft structure. Changes in radar-measured tornado intensity lag those of ensemble Kalman filter (EnKF) mesocyclone vorticity and circulation.

关键词： Atm/Ocean Structure/ Phenomena Downbursts Supercells Tornadoes observational techniques and algorithms Radars/Radar observations Models and modeling Data assimilation Numerical analysis/modeling

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