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Improvements of Rain/No-Rain Classification Methods for Microwave Radiometer over Coasts by Dynamic Surface-Type Classification

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第6期33卷 1257-1270页

作者： Mega, Tomoaki Shige, Shoichi Kyoto Univ Grad Sch Sci Kyoto Japan

The rain/no-rain classification for the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) fails to detect rain over coasts, where the microwave footprint encompasses a mixture of radiometrically cold ocean and radiometrically warm land. A static land-ocean-coast mask is used to determine the surface type of each satellite footprint. The coast mask is conservatively wide to account for the largest footprints, preventing use of the more appropriate ocean or land algorithm for coastal regions. The purpose of this paper is to develop a classification whereby the smallest region possible is defined as coast. In this endeavor, two major improvements are applied to the land-ocean-coast classification. First, the surface classification based on microwave footprints of the high frequency actually used in rain detection is employed. Second, the footprint area of the surface classification is established using an effective field-of-view size and scan geometry of the TMI. These improvements are applied to the Global Satellite Mapping of Precipitation TMI algorithm. The classification result is validated using the TRMM precipitation radar. The validation shows that these improvements lead to better rain detection in the coastal region.

关键词： Atm/Ocean Structure/ Phenomena Precipitation observational techniques and algorithms algorithms Remote sensing Satellite observations

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Polarimetric Radar Observations of Precipitation Type and Rate from the 2-3 March 2014 Winter Storm in Oklahoma and Arkansas

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WEATHER AND FORECASTING 2016年第4期31卷 1179-1196页

作者： Van Den Broeke, Matthew S. Tobin, Dana M. Kumjian, Matthew R. Univ Nebraska Dept Earth & Atmospher Sci Lincoln NE USA Penn State Univ Dept Meteorol & Atmospher Sci University Pk PA 16802 USA

A powerful winter storm affected the south-central United States in early March 2014, accompanied by elevated convective cells with hail and high rates of sleet, freezing rain, and snow. During portions of the event the thermal profile exhibited a shallow surface cold layer and warm, unstable air aloft. Precipitation falling into the cold layer refroze into ice pellets and was accompanied by a polarimetric refreezing signature and numerous crowdsourced surface ice pellet reports. Quasi-vertical profiles of the polarimetric variables indicated an enhanced reflectivity factor Z(HH) below the melting layer bright band and enhanced low-level differential reflectivity Z(DR) values coincident with surface ice pellet reports. Freezing rain rate was highest in areas with high Z(HH) and specific differential phase K-DP values at low levels. High snow rates were most closely associated with 1- and 1.5-km Z(HH) values, though K-Dp and Z(DR) also appeared to show some ability to distinguish high snow rate. Numerous elevated convective cells contained rotating updrafts that appeared to contribute to storm longevity and intensity. Most contained well-defined Z(DR) maxima or columns and relatively high base-scan Z(DR) values. Several contained polarimetric signatures consistent with heavy mixed-phase precipitation and hail;social media reports indicated that large hail was produced by some of the storms.

关键词： Atm/Ocean Structure/ Phenomena Convective clouds Hail Precipitation Snow observational techniques and algorithms Radars/Radar observations Forecasting Nowcasting

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Comparison of In Situ Soil Moisture Measurements: An Examination of the Neutron and Dielectric Measurements within the Illinois Climate Network

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第8期33卷 1749-1758页

作者： Coopersmith, Evan J. Cosh, Michael H. Jacobs, Jennifer M. ARS Hydrol & Remote Sensing Lab USDA Beltsville MD 20705 USA Univ New Hampshire Dept Civil & Environm Engn Durham NH 03824 USA

The continuity of soil moisture time series data is crucial for climatic research. Yet, a common problem for continuous data series is the changing of sensors, not only as replacements are necessary, but as technologies evolve. The Illinois Climate Network has one of the longest data records of soil moisture;yet, it has a discontinuity when the primary sensor (neutron probes) was replaced with a dielectric sensor. Applying a simple model coupled with machine learning, the two time series can be merged into one continuous record by training the model on the latter dielectric model and minimizing errors against the former neutron probe dataset. The model is able to be calibrated to an accuracy of 0.050 m(3) m(-3) and applying this to the earlier series and applying a gain and offset, an RMSE of 0.055 m(3) m(-3) is possible. As a result of this work, there is now a singular network data record extending back to the 1980s for the state of Illinois.

关键词： Agriculture Applications Geographic location/entity Instrumentation/sensors Mathematical and statistical techniques North America observational techniques and algorithms Surface observations Time series

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Mid- to Inner-Shelf Coupled ROMS-SWAN Model-Data Comparison of Currents and Temperature: Diurnal and Semidiurnal Variability

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JOURNAL OF PHYSICAL OCEANOGRAPHY 2016年第3期46卷 841-862页

作者： Kumar, Nirnimesh Feddersen, Falk Suanda, Sutara Uchiyama, Yusuke McWilliams, James Univ Calif San Diego Scripps Inst Oceanog 9500 Gilman Dr La Jolla CA 92093 USA Kobe Univ Dept Civil Engn Kobe Hyogo 657 Japan Univ Calif Los Angeles Inst Geophys & Planetary Phys Los Angeles CA 90024 USA

Accurately representing diurnal and semidiurnal internal variability is necessary to investigate inner-shelf to midshelf exchange processes. Here, a coupled Regional Ocean Model System (ROMS)-Simulating Waves Nearshore (SWAN) model is compared to observed diurnal and semidiurnal internal tidal variability on the mid and inner shelf (26-8 m water depth) near San Pedro Bay, California. Modeled mean stratification is about one-half of that observed. Modeled and observed baroclinic velocity rotary spectra are similar in the diurnal and semidiurnal band. Modeled and observed temperature spectra have similar diurnal and semidiurnal band structure, although the modeled is weaker. The observed and modeled diurnal and semidiurnal baroclinic velocity- and temperature-dominant vertical structures are similar and consistent with mode-one internal motions. Both observed and modeled diurnal baroclinic kinetic energy are strongly correlated to diurnal wind forcing and enhanced by subtidal vorticity-induced reduction in the inertial frequency. The mid- and inner-shelf modeled diurnal depth-integrated heat budget is a balance between advective heat flux divergence and temperature time derivative. Temperature-velocity phase indicates progressive semidiurnal internal tide on the midshelf and largely standing internal tide on the inner shelf in both observed and modeled. The ratio of observed to modeled inferred phase speed is consistent with the observed to modeled stratification. The San Pedro Bay modeled semidiurnal internal tide has significant spatial variability, variable incident wave angles, and multiple local generation sites. Overall, the coupled ROMS-SWAN model represents well the complex diurnal and semidiurnal internal variability from the mid to the inner shelf.

关键词： In situ oceanic observations observational techniques and algorithms Geographic location/entity Models and modeling Circulation/ Dynamics Internal waves Ocean models Empirical orthogonal functions Pacific Ocean Time series Mathematical and statistical techniques

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Mesoscale to Submesoscale Wavenumber Spectra in Drake Passage

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JOURNAL OF PHYSICAL OCEANOGRAPHY 2016年第2期46卷 601-620页

作者： Rocha, Cesar B. Chereskin, Teresa K. Gille, Sarah T. Menemenlis, Dimitris Univ Calif San Diego Scripps Inst Oceanog 9500 Gilman DrMC 0213 La Jolla CA 92093 USA CALTECH Jet Prop Lab Div Earth Sci Pasadena CA USA

This study discusses the upper-ocean (0-200 m) horizontal wavenumber spectra in the Drake Passage from 13 yr of shipboard ADCP measurements, altimeter data, and a high-resolution numerical simulation. At scales between 10 and 200 km, the ADCP kinetic energy spectra approximately follow a k(-3) power law. The observed flows are more energetic at the surface, but the shape of the kinetic energy spectra is independent of depth. These characteristics resemble predictions of isotropic interior quasigeostrophic turbulence. The ratio of across-track to along-track kinetic energy spectra, however, significantly departs from the expectation of isotropic interior quasigeostrophic turbulence. The inconsistency is dramatic at scales smaller than 40 km. A Helmholtz decomposition of the ADCP spectra and analyses of synthetic and numerical model data show that horizontally divergent, ageostrophic flows account for the discrepancy between the observed spectra and predictions of isotropic interior quasigeostrophic turbulence. In Drake Passage, ageostrophic motions appear to be dominated by inertia-gravity waves and account for about half of the near-surface kinetic energy at scales between 10 and 40 km. Model results indicate that ageostrophic flows imprint on the sea surface, accounting for about half of the sea surface height variance between 10 and 40 km.

关键词： Ship observations Atm/Ocean Structure/ Phenomena Eddies Satellite observations observational techniques and algorithms Oceanic mixed layer Tides

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Advances in Geostationary-Derived Longwave Fluxes for the CERES Synoptic (SYN1deg) Product

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第3期33卷 503-521页

作者： Doelling, David R. Sun, Moguo Le Trang Nguyen Nordeen, Michele L. Haney, Conor O. Keyes, Dennis F. Mlynczak, Pamela E. NASA Langley Res Ctr 21 Langley BlvdMS 420 Hampton VA 23681 USA Sci Syst & Applicat Inc Hampton VA USA

The Clouds and the Earth's Radiant Energy System (CERES) project has provided the climate community 15 years of globally observed top-of-the-atmosphere fluxes critical for climate and cloud feedback studies. To accurately monitor the earth's radiation budget, the CERES instrument footprint fluxes must be spatially and temporally averaged properly. The CERES synoptic 1 degrees (SYN1deg) product incorporates derived fluxes from the geostationary satellites (GEOs) to account for the regional diurnal flux variations in between Terra and Aqua CERES measurements. The Edition 4 CERES reprocessing effort has provided the opportunity to reevaluate the derivation of longwave (LW) fluxes from GEO narrowband radiances by examining the improvements from incorporating 1-hourly versus 3-hourly GEO data, additional GEO infrared (IR) channels, and multichannel GEO cloud properties. The resultant GEO LW fluxes need to be consistent across the 16-satellite climate data record. To that end, the addition of the water vapor channel, available on all GEOs, was more effective than using a reanalysis dataset's column-weighted relative humidity combined with the window channel radiance. The benefit of the CERES LW angular directional model to derive fluxes was limited by the inconsistency of the GEO cloud retrievals. Greater success was found in the direct conversion of window and water vapor channel radiances into fluxes. Incorporating 1-hourly GEO fluxes had the greatest impact on improving the accuracy of high-temporal-resolution fluxes, and normalizing the GEO LW fluxes with CERES greatly reduced the monthly regional LW flux bias.

关键词： Climate records Remote sensing Satellite observations observational techniques and algorithms Instrumentation/sensors Sampling

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Calibration, Validation, and Analysis of an Empirical Algorithm for the Retrieval of Wave Spectra from HF Radar Sea Echo

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第2期33卷 245-261页

作者： Lopez, Guiomar Conley, Daniel C. Greaves, Deborah Univ Plymouth Sch Marine Sci & Engn Marine Bldg Plymouth PL4 8AA Devon England

The accuracy of the wave products retrieved by a 12-MHz high-frequency (HF) phased-array radar is evaluated for a 5-month period. The two stations composing the system were deployed in 2011 to overlook the Wave Hub, a test site for marine renewable energy devices located on the southwestern coast of the United Kingdom. The system was conceived and configured to reduce the inaccuracies introduced by short time averaging and minimal overlap between stations, both associated with the most traditional HF radar deployments, whose primary activity is current measurement. Wave spectra were retrieved by an empirical algorithm distributed with Wellen Radars (WERA), which were calibrated using in situ measurements collected within the radar footprint. Evaluated through comparison against measurements acquired by three in situ devices, the results revealed estimates of significant wave height with nearly zero bias, linear correlations higher than 90%, and RMS errors that range from 29 to 44 cm. The relative error of wave energy period comparisons was within 10% for periods between 8 and 13 s, while both under- and overestimations were observed above and below that range, respectively. The validation demonstrated that when locally calibrated, the algorithm performs better than in its original form in all metrics considered. Observed discrepancies are mainly attributable to single-site estimations, antenna sidelobes, and the effect of the second-harmonic peaks of the Doppler spectrum.

关键词： Mathematical and statistical techniques Circulation/ Dynamics Error analysis In situ oceanic observations observational techniques and algorithms Radars/Radar observations algorithms Inverse methods Gravity waves

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On the Role of Temperature and Salinity Data Assimilation to Constrain a Coupled Physical-Biogeochemical Model in the Baltic Sea

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JOURNAL OF PHYSICAL OCEANOGRAPHY 2016年第3期46卷 713-729页

作者： Fu, Weiwei Danish Meteorol Inst Ctr Ocean & Ice DK-2100 Copenhagen Denmark Chinese Acad Sci Inst Atmospher Phys Beijing Peoples R China

A three-dimensional variational data assimilation (3DVAR) method is implemented in a coupled physical-biogeochemical (CPB) model in the Baltic Sea. This study carries out a 10-yr assimilation experiment with satellite sea surface temperature (SST) and observed in situ temperature (T) and salinity (S) profiles. The impact of the assimilation is assessed with the focus on how the biogeochemical model responds to the improved hydrodynamics. The assimilation of temperature and salinity data yields considerable improvements in the physical model. On a basin scale, the mean bias of SST, T, S, and mixed layer depth (MLD) is decreased by 0.18 degrees C (57%), 0.31 degrees C (49%), 0.34 psu (43%), and 1.8 m (43%), respectively. More importantly, the biogeochemical simulation is improved in response to the physical data assimilation. Compared with in situ observations, the mean biases of chlorophyll a (Chl), dissolved inorganic nitrogen (DIN) and phosphorus (DIP) are decreased by 0.09 mg m(-3) (15.5%), 0.19 mmol m(-3) (9%), and 0.15 mmol m(-3) (23%). Physical data assimilation also improves the simulated variability of Chl, DIN, and DIP and their correlations with observation. Compared with satellite observations, the mean bias of surface chlorophyll is reduced by 0.10-0.32 mg m(-3) especially in the Skagerrak-Kattegat area and Bornholm basin. The decrease of total Chl change is caused by different mechanisms for winter and summer. While the deepened mixed layer acts as a dilution factor in winter, strengthened stratification agrees well with the decrease of chlorophyll in summer. In the vertical, relatively large changes of DIN and DIP occur below 60 m, which corresponds to the mean permanent halocline depth (~60-80 m) of the Baltic Sea.

关键词： In situ oceanic observations Ecosystem effects Applications Data assimilation observational techniques and algorithms Regional models Models and modeling Coupled models

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The Modular Aerial Sensing System

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第6期33卷 1169-1184页

作者： Melville, W. Kendall Lenain, Luc Cayan, Daniel R. Kahru, Mati Kleissl, Jan P. Linden, P. F. Statom, Nicholas M. Univ Calif San Diego Scripps Inst Oceanog 9500 Gilman Dr La Jolla CA 92093 USA Univ Calif San Diego Dept Mech & Aerosp Engn La Jolla CA 92093 USA Univ Cambridge Dept Appl Math & Theoret Phys Silver St Cambridge CB3 9EW England

Satellite remote sensing has enabled remarkable progress in the ocean, earth, atmospheric, and environmental sciences through its ability to provide global coverage with ever-increasing spatial resolution. While exceptions exist for geostationary ocean color satellites, the temporal coverage of low-Earth-orbiting satellites is not optimal for oceanographic processes that evolve over time scales of hours to days. In hydrology, time scales can range from hours for flash floods, to days for snowfall, to months for the snowmelt into river systems. On even smaller scales, remote sensing of the built environment requires a building-resolving resolution of a few meters or better. For this broad range of phenomena, satellite data need to be supplemented with higher-resolution airborne data that are not tied to the strict schedule of a satellite orbit. To address some of these needs, a novel, portable, high-resolution airborne topographic lidar with video, infrared, and hyperspectral imaging systems was integrated. The system is coupled to a highly accurate GPS-aided inertial measurement unit (GPS IMU), permitting airborne measurements of the sea surface displacement, temperature, and kinematics with swath widths of up to 800 m under the aircraft, and horizontal spatial resolution as low as 0.2 m. These data are used to measure ocean waves, currents, Stokes drift, sea surface height (SSH), ocean transport and dispersion, and biological activity. Hydrological and terrestrial applications include measurements of snow cover and the built environment. This paper describes the system, its performance, and present results from recent oceanographic, hydrological, and terrestrial measurements.

关键词： Physical Meteorology and Climatology Air-sea interaction Snow cover observational techniques and algorithms Aircraft observations Lidars/Lidar observations Remote sensing Applications Urban meteorology

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Stratospheric Temperature Climate Data Record from Merged SSU and AMSU-A Observations

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016年第9期33卷 1967-1984页

作者： Zou, Cheng-Zhi Qian, Haifeng NOAA Ctr Satellite Applicat & Res NESDIS College Pk MD USA Earth Resource Technol Inc Laurel MD USA

Observations from the Stratospheric Sounding Unit (SSU) on board historical NOAA polar-orbiting satellites have played a vital role in investigations of long-term trends and variability in the middle-and upper-stratospheric temperatures during 1979-2006. The successor to SSU is the Advanced Microwave Sounding Unit-A (AMSU-A) starting from 1998 until the present. Unfortunately, the two observations came from different sets of atmospheric layers, and the SSU weighting functions varied with time and location, posing a challenge to merge them with sufficient accuracy for development of an extended SSU climate data record. This study proposes a variational approach for the merging problem, matching in both temperatures and weighting functions. The approach yields zero means with a small standard deviation and a negligible drift over time in the temperature differences between SSU and its extension to AMSU-A. These features made the approach appealing for reliable detection of long-term climate trends. The approach also matches weighting functions with high accuracy for SSU channels 1 and 2 and reasonable accuracy for channel 3. The total decreases in global mean temperatures found from the merged dataset were from 1.8K in the middle stratosphere to 2.4K in the upper stratosphere during 1979-2015. These temperature drops were associated with two segments of piecewise linear cooling trends, with those during the first period (1979-97) being much larger than those of the second period (1998-2015). These differences in temperature trends corresponded well to changes of the atmospheric ozone amount from depletion to recovery during the respective time periods, showing the influence of human decisions on climate change.

关键词： algorithms Climate change Climate records Microwave observations observational techniques and algorithms Physical Meteorology and Climatology Satellite observations Temperature

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