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  • 1
    In: Journal of Applied Meteorology and Climatology, American Meteorological Society, Vol. 55, No. 3 ( 2016-03), p. 709-722
    Abstract: In this study, two different particle models describing the structure and electromagnetic properties of snow are developed and evaluated for potential use in satellite combined radar–radiometer precipitation estimation algorithms. In the first model, snow particles are assumed to be homogeneous ice–air spheres with single-scattering properties derived from Mie theory. In the second model, snow particles are created by simulating the self-collection of pristine ice crystals into aggregate particles of different sizes, using different numbers and habits of the collected component crystals. Single-scattering properties of the resulting nonspherical snow particles are determined using the discrete dipole approximation. The size-distribution-integrated scattering properties of the spherical and nonspherical snow particles are incorporated into a dual-wavelength radar profiling algorithm that is applied to 14- and 34-GHz observations of stratiform precipitation from the ER-2 aircraftborne High-Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP) radar. The retrieved ice precipitation profiles are then input to a forward radiative transfer calculation in an attempt to simulate coincident radiance observations from the Conical Scanning Millimeter-Wave Imaging Radiometer (CoSMIR). Much greater consistency between the simulated and observed CoSMIR radiances is obtained using estimated profiles that are based upon the nonspherical crystal/aggregate snow particle model. Despite this greater consistency, there remain some discrepancies between the higher moments of the HIWRAP-retrieved precipitation size distributions and in situ distributions derived from microphysics probe observations obtained from Citation aircraft underflights of the ER-2. These discrepancies can only be eliminated if a subset of lower-density crystal/aggregate snow particles is assumed in the radar algorithm and in the interpretation of the in situ data.
    Type of Medium: Online Resource
    ISSN: 1558-8424 , 1558-8432
    RVK:
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2016
    detail.hit.zdb_id: 2227779-1
    detail.hit.zdb_id: 2227759-6
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  • 2
    Online Resource
    Online Resource
    American Meteorological Society ; 2018
    In:  Journal of Applied Meteorology and Climatology Vol. 57, No. 11 ( 2018-11), p. 2605-2622
    In: Journal of Applied Meteorology and Climatology, American Meteorological Society, Vol. 57, No. 11 ( 2018-11), p. 2605-2622
    Abstract: In this study, a nonparametric method to estimate precipitating ice from multiple-frequency radar observations is investigated. The method does not require any assumptions regarding the distribution of ice particle sizes and relies on an efficient search procedure to incorporate information from observed particle size distributions (PSDs) in the estimation process. Similar to other approaches rooted in optimal-estimation theory, the nonparametric method is robust in the presence of noise in observations and uncertainties in the forward models. Over 200 000 PSDs derived from in situ observations collected during the Olympic Mountains Experiment (OLYMPEX) and Integrated Precipitation and Hydrology Experiment (IPHEX) field campaigns are used in the development and evaluation of the nonparametric estimation method. These PSDs are used to create a database of ice-related variables and associated computed radar reflectivity factors at the Ku, Ka, and W bands. The computed reflectivity factors are used to derive precipitating ice estimates and investigate the associated errors and uncertainties. The method is applied to triple-frequency radar observations collected during OLYMPEX and IPHEX. Direct comparisons of estimated ice variables with estimates from in situ instruments show results consistent with the error analysis. Global application of the method requires an extension of the supporting PSD database, which can be achieved through the processing of information from additional past and future field campaigns.
    Type of Medium: Online Resource
    ISSN: 1558-8424 , 1558-8432
    RVK:
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2018
    detail.hit.zdb_id: 2227779-1
    detail.hit.zdb_id: 2227759-6
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  • 3
    In: Remote Sensing, MDPI AG, Vol. 4, No. 10 ( 2012-10-11), p. 3022-3054
    Type of Medium: Online Resource
    ISSN: 2072-4292
    Language: English
    Publisher: MDPI AG
    Publication Date: 2012
    detail.hit.zdb_id: 2513863-7
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  • 4
    In: Monthly Weather Review, American Meteorological Society, Vol. 142, No. 2 ( 2014-02-01), p. 590-605
    Abstract: This study explores relationships between lightning, cloud microphysics, and tropical cyclone (TC) storm structure in Hurricane Karl (16 September 2010) using data collected by the NASA DC-8 and Global Hawk (GH) aircraft during NASA’s Genesis and Rapid Intensification Processes (GRIP) experiment. The research capitalizes on the unique opportunity provided by GRIP to synthesize multiple datasets from two aircraft and analyze the microphysical and kinematic properties of an electrified TC. Five coordinated flight legs through Karl by the DC-8 and GH are investigated, focusing on the inner-core region (within 50 km of the storm center) where the lightning was concentrated and the aircraft were well coordinated. GRIP datasets are used to compare properties of electrified and nonelectrified inner-core regions that are related to the noninductive charging mechanism, which is widely accepted to explain the observed electric fields within thunderstorms. Three common characteristics of Karl’s electrified regions are identified: 1) strong updrafts of 10–20 m s−1, 2) deep mixed-phase layers indicated by reflectivities & gt;30 dBZ extending several kilometers above the freezing level, and 3) microphysical environments consisting of graupel, very small ice particles, and the inferred presence of supercooled water. These characteristics describe an environment favorable for in situ noninductive charging and, hence, TC electrification. The electrified regions in Karl’s inner core are attributable to a microphysical environment that was conducive to electrification because of occasional, strong convective updrafts in the eyewall.
    Type of Medium: Online Resource
    ISSN: 0027-0644 , 1520-0493
    RVK:
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2014
    detail.hit.zdb_id: 2033056-X
    detail.hit.zdb_id: 202616-8
    SSG: 14
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  • 5
    Online Resource
    Online Resource
    American Meteorological Society ; 2010
    In:  Journal of the Atmospheric Sciences Vol. 67, No. 1 ( 2010-01-01), p. 195-216
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 67, No. 1 ( 2010-01-01), p. 195-216
    Abstract: An analysis of two days of in situ observations of ice particle size spectra, in convectively generated cirrus, obtained during NASA’s Tropical Composition, Cloud, and Climate Coupling (TC4) mission is presented. The observed spectra are examined for their fit to the exponential, gamma, and lognormal function distributions. Characteristic particle size and concentration density scales are determined using two (for the exponential) or three (for the gamma and lognormal functions) moments of the spectra. It is shown that transformed exponential, gamma, and lognormal distributions should collapse onto standard curves. An examination of the transformed spectra, and of deviations of the transformed spectra from the standard curves, shows that the lognormal function provides a better fit to the observed spectra.
    Type of Medium: Online Resource
    ISSN: 1520-0469 , 0022-4928
    RVK:
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2010
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 6
    Online Resource
    Online Resource
    American Meteorological Society ; 2009
    In:  Journal of the Atmospheric Sciences Vol. 66, No. 12 ( 2009-12-01), p. 3530-3562
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 66, No. 12 ( 2009-12-01), p. 3530-3562
    Abstract: Anvils produced by vigorous tropical convection contribute significantly to the earth’s radiation balance, and their radiative properties depend largely on the concentrations and sizes of the ice particles that form them. These microphysical properties are determined to an important extent by the fate of supercooled droplets, with diameters from 3 to about 20 microns, lofted in the updrafts. The present study addresses the question of whether most or all of these droplets are captured by ice particles or if they remain uncollected until arriving at the −38°C level where they freeze by homogeneous nucleation, producing high concentrations of very small ice particles that can persist and dominate the albedo. Aircraft data of ice particle and water droplet size distributions from seven field campaigns at latitudes from 25°N to 11°S are combined with a numerical model in order to examine the conditions under which significant numbers of supercooled water droplets can be lofted to the homogeneous nucleation level. Microphysical data were collected in pristine to heavily dust-laden maritime environments, isolated convective updrafts, and tropical cyclone updrafts with peak velocities reaching 25 m s−1. The cumulative horizontal distance of in-cloud sampling at temperatures of −20°C and below exceeds 50 000 km. Analysis reveals that most of the condensate in these convective updrafts is removed before reaching the −20°C level, and the total condensate continues to diminish linearly upward. The amount of condensate in small ( & lt;50 μm in diameter) droplets and ice particles, however, increases upward, suggesting new droplet activation with an appreciable radiative impact. Conditions promoting the generation of large numbers of small ice particles through homogeneous ice nucleation include high concentrations of cloud condensation nuclei (sometimes from dust), removal of most of the water substance between cloud base and the −38°C levels, and acceleration of the updrafts at mid- and upper levels such that velocities exceed 5–7 m s−1.
    Type of Medium: Online Resource
    ISSN: 1520-0469 , 0022-4928
    RVK:
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2009
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 7
    Online Resource
    Online Resource
    American Meteorological Society ; 2010
    In:  Journal of the Atmospheric Sciences Vol. 67, No. 2 ( 2010-02-01), p. 285-308
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 67, No. 2 ( 2010-02-01), p. 285-308
    Abstract: This paper presents observations of deep convection characteristics in the tropics and subtropics that have been classified into four categories: tropical cyclone, oceanic, land, and sea breeze. Vertical velocities in the convection were derived from Doppler radar measurements collected during several NASA field experiments from the nadir-viewing high-altitude ER-2 Doppler radar (EDOP). Emphasis is placed on the vertical structure of the convection from the surface to cloud top (sometimes reaching 18-km altitude). This unique look at convection is not possible from other approaches such as ground-based or lower-altitude airborne scanning radars. The vertical motions from the radar measurements are derived using new relationships between radar reflectivity and hydrometeor fall speed. Various convective properties, such as the peak updraft and downdraft velocities and their corresponding altitude, heights of reflectivity levels, and widths of reflectivity cores, are estimated. The most significant findings are the following: 1) strong updrafts that mostly exceed 15 m s−1, with a few exceeding 30 m s−1, are found in all the deep convection cases, whether over land or ocean; 2) peak updrafts were almost always above the 10-km level and, in the case of tropical cyclones, were closer to the 12-km level; and 3) land-based and sea-breeze convection had higher reflectivities and wider convective cores than oceanic and tropical cyclone convection. In addition, the high-resolution EDOP data were used to examine the connection between reflectivity and vertical velocity, for which only weak linear relationships were found. The results are discussed in terms of dynamical and microphysical implications for numerical models and future remote sensors.
    Type of Medium: Online Resource
    ISSN: 1520-0469 , 0022-4928
    RVK:
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2010
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
    Library Location Call Number Volume/Issue/Year Availability
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  • 8
    Online Resource
    Online Resource
    American Meteorological Society ; 2023
    In:  Journal of Applied Meteorology and Climatology Vol. 62, No. 3 ( 2023-03), p. 289-315
    In: Journal of Applied Meteorology and Climatology, American Meteorological Society, Vol. 62, No. 3 ( 2023-03), p. 289-315
    Abstract: Coincident radar data with Doppler radar measurements at X, Ku, Ka, and W bands on the NASA ER-2 aircraft overflying the NASA P-3 aircraft acquiring in situ microphysical measurements are used to characterize the relationship between radar measurements and ice microphysical properties. The data were obtained from the Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS). Direct measurements of the condensed water content and coincident Doppler radar measurements were acquired, facilitating improved estimates of ice particle mass, a variable that is an underlying factor for calculating and therefore retrieving the radar reflectivity Z e , median mass diameter D m , particle terminal velocity, and snowfall rate S . The relationship between the measured ice water content (IWC) and that calculated from the particle size distributions (PSDs) using relationships developed in earlier studies, and between the calculated and measured radar reflectivity at the four radar wavelengths, are quantified. Relationships are derived between the measured IWC and properties of the PSD, D m , Z e at the four radar wavelengths, and the dual-wavelength ratio. Because IWC and Z e are measured directly, the coefficients in the mass–dimensional relationship that best match both the IWC and Z e are derived. The relationships developed here, and the mass–dimensional relationship that uses both the measured IWC and Z e to find a best match for both variables, can be used in studies that characterize the properties of wintertime snow clouds. Significance Statement The goal of this study is to provide reliable microphysical measurements and algorithms to facilitate improvements in cloud model microphysical parameterizations and in retrieval of snow precipitation properties from spaceborne active remote sensors and to characterize ice and snow precipitation development within clouds. This work draws upon a unique set of in situ measurements of the ice and total water content coupled with overflying aircraft radar measurements at four radar wavelengths. Better estimates of the contributions of the ice phase to the total global precipitation using spaceborne radar data pave the way for assessing and advancing global climate modeling, thereby strengthening predictions of global climate change.
    Type of Medium: Online Resource
    ISSN: 1558-8424 , 1558-8432
    RVK:
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2023
    detail.hit.zdb_id: 2227779-1
    detail.hit.zdb_id: 2227759-6
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  • 9
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 103, No. 5 ( 2022-05), p. E1243-E1269
    Abstract: The Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) is a NASA-sponsored field campaign to study wintertime snowstorms focusing on East Coast cyclones. This large cooperative effort takes place during the winters of 2020–23 to study precipitation variability in winter cyclones to improve remote sensing and numerical forecasts of snowfall. Snowfall within these storms is frequently organized in banded structures on multiple scales. The causes for the occurrence and evolution of a wide spectrum of snowbands remain poorly understood. The goals of IMPACTS are to characterize the spatial and temporal scales and structures of snowbands, understand their dynamical, thermodynamical, and microphysical processes, and apply this understanding to improve remote sensing and modeling of snowfall. The first deployment took place in January–February 2020 with two aircraft that flew coordinated flight patterns and sampled a range of storms from the Midwest to the East Coast. The satellite-simulating ER-2 aircraft flew above the clouds and carried a suite of remote sensing instruments including cloud and precipitation radars, lidar, and passive microwave radiometers. The in situ P-3 aircraft flew within the clouds and sampled environmental and microphysical quantities. Ground-based radar measurements from the National Weather Service network and a suite of radars located on Long Island, New York, along with supplemental soundings and the New York State Mesonet ground network provided environmental context for the airborne observations. Future deployments will occur during the 2022 and 2023 winters. The coordination between remote sensing and in situ platforms makes this a unique publicly available dataset applicable to a wide variety of interests.
    Type of Medium: Online Resource
    ISSN: 0003-0007 , 1520-0477
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2022
    detail.hit.zdb_id: 2029396-3
    detail.hit.zdb_id: 419957-1
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  • 10
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 90, No. 8 ( 2009-08), p. 1137-1156
    Type of Medium: Online Resource
    ISSN: 0003-0007 , 1520-0477
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2009
    detail.hit.zdb_id: 2029396-3
    detail.hit.zdb_id: 419957-1
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