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Abstract
This paper describes the development of a novel airborne system that receives a real-time imagery broadcast in the Automatic Picture Transmission (APT) format from polar-orbiting weather satellites. The availability of such real-time imagery allows for the possibility of redirecting an aircraft measurement platform to sample an area of the atmosphere in a timely and spatially meaningful fashion. This technology could also provide pilots with new and potentially important information that could be used to reroute aircraft around weather systems. The authors are not aware of any other airborne APT imaging system that has been documented in the open literature.
The system described in this paper has been used in a number of meteorological field experiments, and imagery obtained during these experiments is presented to illustrate the capabilities of the system.
The most critical element for an airborne system is the antenna due to the conflicting requirements imposed by the wavelength, which is greater than 2 m, and aerodynamic–structural considerations favoring the smallest possible size. The authors describe a low-profile “electrically small” 40-cm-square patch antenna developed for this system that provides excellent gain for elevation angles over 25°.
Abstract
This paper describes the development of a novel airborne system that receives a real-time imagery broadcast in the Automatic Picture Transmission (APT) format from polar-orbiting weather satellites. The availability of such real-time imagery allows for the possibility of redirecting an aircraft measurement platform to sample an area of the atmosphere in a timely and spatially meaningful fashion. This technology could also provide pilots with new and potentially important information that could be used to reroute aircraft around weather systems. The authors are not aware of any other airborne APT imaging system that has been documented in the open literature.
The system described in this paper has been used in a number of meteorological field experiments, and imagery obtained during these experiments is presented to illustrate the capabilities of the system.
The most critical element for an airborne system is the antenna due to the conflicting requirements imposed by the wavelength, which is greater than 2 m, and aerodynamic–structural considerations favoring the smallest possible size. The authors describe a low-profile “electrically small” 40-cm-square patch antenna developed for this system that provides excellent gain for elevation angles over 25°.
Abstract
Operational radar data from three winter seasons (2003–06) in Portland, Oregon, in the U.S. Pacific Northwest are used to describe how orographic precipitation varies with cross-barrier wind speed, 0°C level height, and stability over the moderately wide (~50-km half-width) Cascade Mountain Range. Orographic enhancement is specified in terms of location, frequency, and relative intensity of the reflectivity (precipitation field). The typical storm for the region, as defined by the 25th to 75th percentile characteristics, is compared to storms with <25th and >75th percentile characteristics for a given variable. About half of Portland-region storms have a low-level wind direction within a relatively narrow azimuth range. This subset of storms is used to examine the sensitivity of orographic enhancement relative to other environmental variables. Cross-barrier wind speed has a stronger role in determining the magnitude of precipitation frequency than either 0°C level or stability. Cross-barrier wind speed and 0°C level height have separate but comparable roles in determining the frequency of relatively heavier precipitation. The increase in precipitation frequency with stronger cross-barrier wind speed is partially attributed to the higher occurrence of intermittent convective cells intersecting the slope. The area where inferred riming growth occurs over local peaks on the windward slope broadens upslope as the 0°C level height increases. In the Portland region, variations in the squared moist Brunt–Väisälä frequency yield smaller differences in the pattern and intensity of precipitation enhancement than either cross-barrier wind speed or 0°C level height.
Abstract
Operational radar data from three winter seasons (2003–06) in Portland, Oregon, in the U.S. Pacific Northwest are used to describe how orographic precipitation varies with cross-barrier wind speed, 0°C level height, and stability over the moderately wide (~50-km half-width) Cascade Mountain Range. Orographic enhancement is specified in terms of location, frequency, and relative intensity of the reflectivity (precipitation field). The typical storm for the region, as defined by the 25th to 75th percentile characteristics, is compared to storms with <25th and >75th percentile characteristics for a given variable. About half of Portland-region storms have a low-level wind direction within a relatively narrow azimuth range. This subset of storms is used to examine the sensitivity of orographic enhancement relative to other environmental variables. Cross-barrier wind speed has a stronger role in determining the magnitude of precipitation frequency than either 0°C level or stability. Cross-barrier wind speed and 0°C level height have separate but comparable roles in determining the frequency of relatively heavier precipitation. The increase in precipitation frequency with stronger cross-barrier wind speed is partially attributed to the higher occurrence of intermittent convective cells intersecting the slope. The area where inferred riming growth occurs over local peaks on the windward slope broadens upslope as the 0°C level height increases. In the Portland region, variations in the squared moist Brunt–Väisälä frequency yield smaller differences in the pattern and intensity of precipitation enhancement than either cross-barrier wind speed or 0°C level height.
The NOAA FM-CW Snow-Level RadarAbstract
A vertically pointing radar for monitoring radar brightband height (BBH) has been developed. This new radar utilizes frequency-modulated continuous wave (FM-CW) techniques to provide high-resolution data at a fraction of the cost of comparable pulsed radars. This S-band radar provides details of the vertical structure of precipitating clouds, with full Doppler information. Details of the radar design are presented along with observations from one storm. Results from a calibration using these storm data show the radar meets the design goals. Eleven of these radars have been deployed and provide BBH data in near–real time.
Abstract
A vertically pointing radar for monitoring radar brightband height (BBH) has been developed. This new radar utilizes frequency-modulated continuous wave (FM-CW) techniques to provide high-resolution data at a fraction of the cost of comparable pulsed radars. This S-band radar provides details of the vertical structure of precipitating clouds, with full Doppler information. Details of the radar design are presented along with observations from one storm. Results from a calibration using these storm data show the radar meets the design goals. Eleven of these radars have been deployed and provide BBH data in near–real time.
Abstract
Terrestrial hydrologic trends over the conterminous United States are estimated for 1980–2015 using the National Climate Assessment Land Data Assimilation System (NCA-LDAS) reanalysis. NCA-LDAS employs the uncoupled Noah version 3.3 land surface model at 0.125° × 0.125° forced with NLDAS-2 meteorology, rescaled Climate Prediction Center precipitation, and assimilated satellite-based soil moisture, snow depth, and irrigation products. Mean annual trends are reported using the nonparametric Mann–Kendall test at p < 0.1 significance. Results illustrate the interrelationship between regional gradients in forcing trends and trends in other land energy and water stores and fluxes. Mean precipitation trends range from +3 to +9 mm yr−1 in the upper Great Plains and Northeast to −1 to −9 mm yr−1 in the West and South, net radiation flux trends range from +0.05 to +0.20 W m−2 yr−1 in the East to −0.05 to −0.20 W m−2 yr−1 in the West, and U.S.-wide temperature trends average about +0.03 K yr−1. Trends in soil moisture, snow cover, latent and sensible heat fluxes, and runoff are consistent with forcings, contributing to increasing evaporative fraction trends from west to east. Evaluation of NCA-LDAS trends compared to independent data indicates mixed results. The RMSE of U.S.-wide trends in number of snow cover days improved from 3.13 to 2.89 days yr−1 while trend detection increased 11%. Trends in latent heat flux were hardly affected, with RMSE decreasing only from 0.17 to 0.16 W m−2 yr−1, while trend detection increased 2%. NCA-LDAS runoff trends degraded significantly from 2.6 to 16.1 mm yr−1 while trend detection was unaffected. Analysis also indicated that NCA-LDAS exhibits relatively more skill in low precipitation station density areas, suggesting there are limits to the effectiveness of satellite data assimilation in densely gauged regions. Overall, NCA-LDAS demonstrates capability for quantifying physically consistent, U.S. hydrologic climate trends over the satellite era.
Abstract
Terrestrial hydrologic trends over the conterminous United States are estimated for 1980–2015 using the National Climate Assessment Land Data Assimilation System (NCA-LDAS) reanalysis. NCA-LDAS employs the uncoupled Noah version 3.3 land surface model at 0.125° × 0.125° forced with NLDAS-2 meteorology, rescaled Climate Prediction Center precipitation, and assimilated satellite-based soil moisture, snow depth, and irrigation products. Mean annual trends are reported using the nonparametric Mann–Kendall test at p < 0.1 significance. Results illustrate the interrelationship between regional gradients in forcing trends and trends in other land energy and water stores and fluxes. Mean precipitation trends range from +3 to +9 mm yr−1 in the upper Great Plains and Northeast to −1 to −9 mm yr−1 in the West and South, net radiation flux trends range from +0.05 to +0.20 W m−2 yr−1 in the East to −0.05 to −0.20 W m−2 yr−1 in the West, and U.S.-wide temperature trends average about +0.03 K yr−1. Trends in soil moisture, snow cover, latent and sensible heat fluxes, and runoff are consistent with forcings, contributing to increasing evaporative fraction trends from west to east. Evaluation of NCA-LDAS trends compared to independent data indicates mixed results. The RMSE of U.S.-wide trends in number of snow cover days improved from 3.13 to 2.89 days yr−1 while trend detection increased 11%. Trends in latent heat flux were hardly affected, with RMSE decreasing only from 0.17 to 0.16 W m−2 yr−1, while trend detection increased 2%. NCA-LDAS runoff trends degraded significantly from 2.6 to 16.1 mm yr−1 while trend detection was unaffected. Analysis also indicated that NCA-LDAS exhibits relatively more skill in low precipitation station density areas, suggesting there are limits to the effectiveness of satellite data assimilation in densely gauged regions. Overall, NCA-LDAS demonstrates capability for quantifying physically consistent, U.S. hydrologic climate trends over the satellite era.
Abstract
Since its initial release in 2000, the Weather Research and Forecasting (WRF) Model has become one of the world’s most widely used numerical weather prediction models. Designed to serve both research and operational needs, it has grown to offer a spectrum of options and capabilities for a wide range of applications. In addition, it underlies a number of tailored systems that address Earth system modeling beyond weather. While the WRF Model has a centralized support effort, it has become a truly community model, driven by the developments and contributions of an active worldwide user base. The WRF Model sees significant use for operational forecasting, and its research implementations are pushing the boundaries of finescale atmospheric simulation. Future model directions include developments in physics, exploiting emerging compute technologies, and ever-innovative applications. From its contributions to research, forecasting, educational, and commercial efforts worldwide, the WRF Model has made a significant mark on numerical weather prediction and atmospheric science.
Abstract
Since its initial release in 2000, the Weather Research and Forecasting (WRF) Model has become one of the world’s most widely used numerical weather prediction models. Designed to serve both research and operational needs, it has grown to offer a spectrum of options and capabilities for a wide range of applications. In addition, it underlies a number of tailored systems that address Earth system modeling beyond weather. While the WRF Model has a centralized support effort, it has become a truly community model, driven by the developments and contributions of an active worldwide user base. The WRF Model sees significant use for operational forecasting, and its research implementations are pushing the boundaries of finescale atmospheric simulation. Future model directions include developments in physics, exploiting emerging compute technologies, and ever-innovative applications. From its contributions to research, forecasting, educational, and commercial efforts worldwide, the WRF Model has made a significant mark on numerical weather prediction and atmospheric science.
Abstract
The February–March 2014 deployment of the National Aeronautics and Space Administration (NASA) Airborne Tropical Tropopause Experiment (ATTREX) provided unique in situ measurements in the western Pacific tropical tropopause layer (TTL). Six flights were conducted from Guam with the long-range, high-altitude, unmanned Global Hawk aircraft. The ATTREX Global Hawk payload provided measurements of water vapor, meteorological conditions, cloud properties, tracer and chemical radical concentrations, and radiative fluxes. The campaign was partially coincident with the Convective Transport of Active Species in the Tropics (CONTRAST) and the Coordinated Airborne Studies in the Tropics (CAST) airborne campaigns based in Guam using lower-altitude aircraft (see companion articles in this issue). The ATTREX dataset is being used for investigations of TTL cloud, transport, dynamical, and chemical processes, as well as for evaluation and improvement of global-model representations of TTL processes. The ATTREX data are publicly available online (at https://espoarchive.nasa.gov/).
Abstract
The February–March 2014 deployment of the National Aeronautics and Space Administration (NASA) Airborne Tropical Tropopause Experiment (ATTREX) provided unique in situ measurements in the western Pacific tropical tropopause layer (TTL). Six flights were conducted from Guam with the long-range, high-altitude, unmanned Global Hawk aircraft. The ATTREX Global Hawk payload provided measurements of water vapor, meteorological conditions, cloud properties, tracer and chemical radical concentrations, and radiative fluxes. The campaign was partially coincident with the Convective Transport of Active Species in the Tropics (CONTRAST) and the Coordinated Airborne Studies in the Tropics (CAST) airborne campaigns based in Guam using lower-altitude aircraft (see companion articles in this issue). The ATTREX dataset is being used for investigations of TTL cloud, transport, dynamical, and chemical processes, as well as for evaluation and improvement of global-model representations of TTL processes. The ATTREX data are publicly available online (at https://espoarchive.nasa.gov/).
