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A Network of Mode-S Receivers for Routine Acquisition of Aircraft-Derived Meteorological Data

JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第4期33卷 757-768页

作者： Stone, Edmund Keith Pearce, Gary Met Off FitzRoy Rd Exeter EX1 3PB Devon England

Aircraft are an important source of meteorological observations for both numerical weather models and aviation weather forecasting. There has been increasing interest in novel methods for gathering aircraft-based observations, especially mode-selective (Mode-S) enhanced surveillance (EHS)-derived data. This paper reports on the progress made in the United Kingdom at the Met Office on receiving and processing these data. Five receivers have been deployed, providing up to 5.7 million observations of horizontal wind and temperatures per day over the United Kingdom. The receivers are relatively low cost and deploying them at existing operational weather radar sites has been shown to be an ideal choice. Heading corrections are required to improve the quality of the wind observations. When corrected the Mode-S EHS wind data have similar observations-minus-background (o - b) statistics as Aircraft Meteorological Data Relay [AMDAR;using a Met Office version of the Unified Model over the United Kingdom (UKV)]. For the u wind component, the average per model run o - b root-mean-square value for the Mode-S EHS derived data was 2.45 and 2.12 m s(-1) for AMDAR. The AMDAR data are assimilated into the model.

关键词： Aircraft observations In situ atmospheric observations observational techniques and algorithms

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Statistical Evaluation of Time Multiplexing to Mitigate Differential Reflectivity Bias Due to Cross-Polar Coupling

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第1期33卷 127-147页

作者： Ivic, Igor R. Univ Oklahoma Cooperat Inst Mesoscale Meteorol Studies Norman OK 73019 USA NOAA Natl Severe Storms Lab OAR Norman OK 73069 USA

One of the main challenges to the use of phased array radar for weather observations is the implementation of dual polarization with acceptable levels of cross-polar fields induced by the antenna. For example, to achieve acceptable differential reflectivity (ZDR) bias (e.g., less than 0.1 dB) using simultaneous transmission and reception of H and V polarized waves, the isolation between coaxial cross-polar and copolar beams needs to be in excess of 50 dB. Because such isolation cannot be achieved at an affordable price by antenna hardware, additional methods are required to attain supplementary isolation of orthogonal channels. One such option is time multiplexing. Herein, this approach is evaluated from the statistical aspect, whereby the depolarization caused by the radar hardware is accounted for in this study. An evaluation is conducted using theoretical analysis as well as simulated and time series data from a weather radar. The main criteria for evaluation are the bias and standard deviation of differential reflectivity estimates. The results indicate that the implementation of the time-multiplexing method has the capability to significantly improve upon the radar intrinsic cross-polar isolation. However, it is demonstrated herein that the reflectivity gradients in range adversely affect the efficacy of the method and that the standard deviation of estimates can significantly increase as a result of the time-multiplexing application.

关键词： observational techniques and algorithms Data processing Data quality control Radars/Radar observations Remote sensing

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Diurnal, Seasonal, and 11-yr Solar Cycle Variation Effects on the Virtual Ionosphere Reflection Height and Implications for the Met Office's Lightning Detection System, ATDnet

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第7期33卷 1429-1441页

作者： Hudson, T. S. Horseman, A. Sugier, J. Met Off Exeter Devon England Univ Cambridge Bullard Labs Madingley Rd Cambridge CB3 0EZ England

The virtual ionosphere reflection height variation is investigated temporally and spatially, with specific reference to the Met Office's lightning detection network, the Arrival Time Difference Network (ATDnet). Data from this network, operating at 13.7 kHz, and a propagation model built by the Met Office based upon published theory were used to investigate this variation, specifically with regard to diurnal, seasonal, and 11-yr solar cycle variation. Variation over these temporal scales is chosen, since they correspond with variation in solar irradiance upon the earth's atmosphere, something known to drive ionosphere height variation. The virtual ionosphere reflection height is found to vary diurnally from;similar to 65 km for the period 1000-1600 UTC to;similar to 80 km for the period 2200-0400 UTC, from 1 June to 31 August 2013 inclusive. A similar magnitude of variation is also observed seasonally, with the ionosphere height for daytime in August 2013 being;similar to 64 km and for December 2013 being;similar to 76 km. No significant variation is observed between the minimum and maximum of the last solar cycle, with a difference in ionosphere height of;similar to 1 km at most. The potential impacts of these results upon a very low-frequency (VLF) lightning detection network such as ATDnet are discussed, with solutions such as subnetting and wave-mode dominance analysis examined.

关键词： Atm/Ocean Structure/ Phenomena Data processing Ionosphere Lightning Models and modeling Numerical analysis/modeling observational techniques and algorithms Remote sensing

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A Point Cloud Method for Retrieval of High-Resolution 3D Gridded Reflectivity from Weather Radar Networks for Air Traffic Management

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第3期33卷 461-479页

作者： Scovell, Robert Al-Sakka, Hassan Met Off Exeter EX1 3PB Devon England Meteo France Toulouse France

A prototype high-resolution (1 km, 5 min) multiradar 3D gridded reflectivity product, including a suite of derived 2D vertical column products, has been developed for the Single European Skies Air Traffic Management Research program. As part of this, a new method for mapping radar data to grid points is being used, based on the concept of a binary space partitioning (BSP) tree that treats radar data as a set of points in a 3D point cloud. This allows the resulting analysis to be based on a complete picture of the nearby data from overlapping radars and can easily adapt to irregular grid configurations. This method is used with a Barnes successive corrections technique to retrieve finescale features while avoiding problems of undersmoothing in data-sparse regions. This has been tested using 3D domains enclosing the terminal maneuvering areas surrounding Paris, France, and London, United Kingdom, and using reflectivity plan position indicator scan data from the French and U.K. operational networks, encoded using the standard European Operational Programme for the Exchange of Weather Radar Information (OPERA) Data Information Model format. Quantitative intercomparisons between the new method, in various configurations;a high-resolution version of an existing method, in operational use at Meteo-France;and a method that was developed by the National Oceanic and Atmospheric Administration for use with the Weather Surveillance Radar-1998 Doppler radar network, have been done using simulated radar scans derived from 3D synthetic radar reflectivity fields in stratiform and convective regimes.

关键词： Radars/Radar observations Mathematical and statistical techniques Interpolation schemes Remote sensing algorithms observational techniques and algorithms

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Retrieval of Snow Properties for Ku- and Ka-Band Dual-Frequency Radar

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JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY 2016年第9期55卷 1845-1858页

作者： Liao, Liang Meneghini, Robert Tokay, Ali Bliven, Larry F. Morgan State Univ Goddard Earth Sci Technol & Res Program Baltimore MD 21239 USA NASA Goddard Space Flight Ctr Code 612 Greenbelt MD 20771 USA Univ Maryland Baltimore Cty Baltimore MD 21228 USA Joint Ctr Earth Syst Technol Baltimore MD USA NASA Wallops Flight Facil Wallops Isl VA USA

The focus of this study is on the estimation of snow microphysical properties and the associated bulk parameters such as snow water content and water equivalent snowfall rate for Ku- and Ka-band dual-frequency radar. This is done by exploring a suitable scattering model and the proper particle size distribution (PSD) assumption that accurately represent, in the electromagnetic domain, the micro-/macrophysical properties of snow. The scattering databases computed from simulated aggregates for small-to-moderate particle sizes are combined with a simple scattering model for large particle sizes to characterize snow-scattering properties over the full range of particle sizes. With use of the single-scattering results, the snow retrieval lookup tables can be formed in a way that directly links the Ku- and Ka-band radar reflectivities to snow water content and equivalent snowfall rate without use of the derived PSD parameters. A sensitivity study of the retrieval results to the PSD and scattering models is performed to better understand the dual-wavelength retrieval uncertainties. To aid in the development of the Ku- and Ka-band dual-wavelength radar technique and to further evaluate its performance, self-consistency tests are conducted using measurements of the snow PSD and fall velocity acquired from the Snow Video Imager/Particle Image Probe (SVI/PIP) during the winter of 2014 at the NASA Wallops Flight Facility site in Wallops Island, Virginia.

关键词： observational techniques and algorithms algorithms Radars/Radar observations Remote sensing

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An Evaluation of HIRS Near-Surface Air Temperature Product in the Arctic with SHEBA Data

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第3期33卷 453-460页

作者： Peng, Ge Shi, Lei Stegall, Steve T. Matthews, Jessica L. Fairall, Christopher W. N Carolina State Univ Cooperat Inst Climate & Satellites North Carolina Asheville NC USA NOAA Natl Ctr Environm Informat Asheville NC USA NOAA Earth Syst Res Lab Boulder CO USA

The accuracy of cloud-screened 2-m air temperatures derived from the intersatellite-calibrated brightness temperatures based on the High Resolution Infrared Radiation Sounder (HIRS) measurements on board the National Oceanic and Atmospheric Administration (NOAA) Polar-Orbiting Operational Environmental Satellite (POES) series is evaluated by comparing HIRS air temperatures to 1-yr quality-controlled measurements collected during the Surface Heat Budget of the Arctic Ocean (SHEBA) project (October 1997-September 1998). The mean error between collocated HIRS and SHEBA 2-m air temperature is found to be on the order of 1 degrees C, with a slight sensitivity to spatial and temporal radii for collocation. The HIRS temperatures capture well the temporal variability of SHEBA temperatures, with cross-correlation coefficients higher than 0.93, all significant at the 99.9% confidence level. More than 87% of SHEBA temperature variance can be explained by linear regression of collocated HIRS temperatures. The analysis found a strong dependency of mean temperature errors on cloud conditions observed during SHEBA, indicating that availability of an accurate cloud mask in the region is essential to further improve the quality of HIRS near-surface air temperature products. This evaluation establishes a baseline of accuracy of HIRS temperature retrievals, providing users with information on uncertainty sources and estimates. It is a first step toward development of a new long-term 2-m air temperature product in the Arctic that utilizes intersatellite-calibrated remote sensing data from the HIRS instrument.

关键词： Ship observations Arctic observational techniques and algorithms Geographic location/entity Physical Meteorology and Climatology Sea/ocean surface Surface temperature Satellite observations

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Investigation of the Spatial Variability of the Convective Boundary Layer Heights over an Isolated Mountain: Cases from the MATERHORN-2012 Experiment

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JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY 2016年第9期55卷 1927-1952页

作者： Pal, S. De Wekker, S. F. J. Emmitt, G. D. Univ Virginia Dept Environm Sci POB 400123291 McCormick Rd Charlottesville VA 22904 USA Simpson Weather Associates Charlottesville VA USA

Spatiotemporal variability in the convective boundary layer height z(i) over complex terrain is governed by numerous factors such as land surface processes, topography, and synoptic conditions. observational datasets to evaluate weather forecast models that simulate this variability are sparse. This study aims to investigate the z(i) spatial variability (along a total leg length of 1800 km) around and over a steep isolated mountain (Granite Mountain) of horizontal and vertical dimensions of 8 and 0.9 km, respectively. An airborne Doppler lidar was deployed on seven flights during the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) campaign conducted at Dugway Proving Ground (Utah) from 25 September to 24 October 2012. During the afternoon, an east-west z(i) gradient over the region with z(i) that was approximately 200m higher on the eastern side than on the western side of Granite Mountain was observed. This gradient illustrates the impact of two different land surface properties on z(i) spatial variability, with a sparsely vegetated desert steppe region on the east and a dry, bare lake-bed desert with high subsurface soil moisture to the west of Granite Mountain. Additionally, the z(i) spatial variability was partly attributed to the impact of Granite Mountain on the downwind z(i). Differences in z(i) were also observed by the radiosonde measurements in the afternoon but not in the morning as the z(i) variability in morning were modulated by the topography. The high-resolution lidar-derived z(i) measurements were used to estimate the entrainment zone thickness in the afternoon, with estimates ranging from 100 to 250 m.

关键词： Circulation/ Dynamics Atmosphere-land interaction Dynamics Atm/Ocean Structure/ Phenomena Boundary layer Physical Meteorology and Climatology Orographic effects observational techniques and algorithms Lidars/Lidar observations Surface observations

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Sensor-Specific Error Statistics for SST in the Advanced Clear-Sky Processor for Oceans

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第2期33卷 345-359页

作者： Petrenko, B. Ignatov, A. Kihai, Y. Dash, P. NOAA STAR 5830 Univ Res Court College Pk MD 20740 USA GST Inc Greenbelt MD USA Colorado State Univ Cooperat Inst Res Atmosphere Ft Collins CO 80523 USA

The formulation of the sensor-specific error statistics (SSES) has been redesigned in the latest implementation of the NOAA Advanced Clear-Sky Processor for Oceans (ACSPO) to enable efficient use of SSES for assimilation of the ACSPO baseline regression SST (BSST) into level 4 (L4) analyses. The SSES algorithm employs segmentation of the SST domain in the space of regressors and derives the segmentation parameter from the statistics of regressors within the global dataset of matchups. For each segment, local regression coefficients and standard deviations (SDs) of BSST minus in situ SST are calculated from the corresponding subset of matchups. The local regression coefficients are used to generate an auxiliary product-piecewise regression (PWR) SST-and SSES biases are estimated as differences between BSST and PWR SST. Correction of SSES biases, which transforms BSST back into PWR SST, reduces the effects of residual cloud;variations in view zenith angle;and, during the daytime, diurnal surface warming. This results in significant reduction in the global SD of fitting in situ SST, making it comparable with SD for the Canadian Meteorological Centre (CMC) L4 SST. Unlike the foundation CMC SST (which is consistent with in situ SST at night but biased cold during the daytime), the PWR SST is consistent with in situ data during both day and night and thus may be viewed as an estimate of "depth" in situ SST. The PWR SST is expected to be a useful input into L4 SST analyses, especially for foundation SST products, such as the CMC L4.

关键词： Remote sensing observational techniques and algorithms algorithms

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A-Train-Based Case Study of Stratiform-Convective Transition within a Warm Conveyor Belt

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MONTHLY WEATHER REVIEW 2016年第6期144卷 2069-2084页

作者： Crespo, Juan A. Posselt, Derek J. Univ Michigan Ann Arbor MI 48109 USA

Clouds are both produced by and interact with the mesoscale and synoptic-scale structure of extratropical cyclones (ETCs) in ways that are still not well understood. Cloud-scale radiative and latent heating modifies the thermal environment, leading to a response in the dynamics that can in turn feed back on cloud distribution and microphysical properties. Key to the structure of ETCs is the warm conveyor belt (WCB);the poleward-ascending airstream that produces the bulk of the clouds and precipitation. This paper examines a long-lived WCB that persisted over the western North Atlantic Ocean in nearly the same location for several days. During this time, the storm was sampled multiple times by NASA's A-Train satellite constellation, and a clear transition from stratiform to convective clouds was observed. Examination of coincident temperature and water vapor data reveals destabilization of the thermodynamic profile after the cyclone reached maturity. CloudSat radar reflectivity from two sequential overpasses of the warm front depicts a change from stratiform to convective cloud structure, and high-frequency microwave data reveal an increase in the amount of ice hydrometeors. The presence of convection may serve to strengthen the warm frontal trough while slowing the movement of the primary low pressure center. The stratiform-convective transition cannot be detected from passive measurements of cloud-top pressure. The results demonstrate the effectiveness of multivariate satellite observations for examining the outcome of dynamic processes in ETCs, and highlight the need for more rapid temporal profiling in future remote sensing observing systems.

关键词： Circulation/ Dynamics Convection Fronts Atm/Ocean Structure/ Phenomena Extratropical cyclones Frontogenesis/frontolysis Warm fronts observational techniques and algorithms Remote sensing

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Improvements in Typhoon Intensity Change Classification by Incorporating an Ocean Coupling Potential Intensity Index into Decision Trees*^,+

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WEATHER AND FORECASTING 2016年第1期31卷 95-106页

作者： Gao, Si Zhang, Wei Liu, Jia Lin, I. -I. Chiu, Long S. Cao, Kai Nanjing Univ Informat Sci & Technol Minist Educ Int Joint Lab Climate & Environm Change Nanjing 210044 Jiangsu Peoples R China Nanjing Univ Informat Sci & Technol Minist Educ Key Lab Meteorol Disaster Nanjing 210044 Jiangsu Peoples R China Natl Taiwan Univ Dept Atmospher Sci Taipei 10764 Taiwan George Mason Univ Coll Sci Dept Atmospher Ocean & Earth Sci Fairfax VA 22030 USA Natl Univ Singapore Dept Geog Singapore 117548 Singapore

Tropical cyclone (TC) intensity prediction, especially in the warning time frame of 24-48 h and for the prediction of rapid intensification (RI), remains a major operational challenge. Sea surface temperature (SST) based empirical or theoretical maximum potential intensity (MPI) is the most important predictor in statistical intensity prediction schemes and rules derived by data mining techniques. Since the underlying SSTs during TCs usually cannot be observed well by satellites because of rain contamination and cannot be produced on a timely basis for operational statistical prediction, an ocean coupling potential intensity index (OC_PI), which is calculated based on pre-TC averaged ocean temperatures from the surface down to 100 m, is demonstrated to be important in building the decision tree for the classification of 24-h TC intensity change Delta V-24, that is, RI (Delta V-24 >= 25 kt, where 1 kt = 0.51 m s(-1)) and non-RI (Delta V-24 < 25 kt). Cross validations using 2000-10 data and independent verification using 2011 data are performed. The decision tree with the OC_PI shows a cross-validation accuracy of 83.5% and an independent verification accuracy of 89.6%, which outperforms the decision tree excluding the OC_PI with corresponding accuracies of 83.2% and 83.9%. Specifically for RI classification in independent verification, the former decision tree shows a much higher probability of detection and a lower false alarm ratio than the latter example. This study is of great significance for operational TC RI prediction as pre-TC OC_PI can skillfully reduce the overestimation of storm potential intensity by traditional SST-based MPI, especially for the non-RI TCs.

关键词： observational techniques and algorithms Geographic location/entity North Pacific Ocean Hurricanes/typhoons Statistical forecasting Classification Data mining Northern Hemisphere Forecasting Mathematical and statistical techniques Atm/Ocean Structure/ Phenomena

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