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Results for “Hurricane Karl”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
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NASA NTRS2013

Understanding the Relationships Between Lightning, Cloud Microphysics, and Airborne Radar-derived Storm Structure During Hurricane Karl (2010)

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 50km 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 10-20ms21, 2) deep mixed-phase layers indicated by reflectivities.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.

Cloud mircophysics↗
NASA NTRS2012

EnKF OSSE Experiments Assessing the Impact of HIRAD Wind Speed and HIWRAP Radial Velocity Data on Analysis of Hurricane Karl (2010)

Previous studies (e.g., Zhang et al. 2009, Weng et al. 2011) have shown that radial velocity data from airborne and ground-based radars can be assimilated into ensemble Kalman filter (EnKF) systems to produce accurate analyses of tropical cyclone vortices, which can reduce forecast intensity error. Recently, wind speed data from SFMR technology has also been assimilated into the same types of systems and has been shown to improve the forecast intensity of mature tropical cyclones. Two instruments that measure these properties were present during the NASA Genesis and Rapid Intensification Processes (GRIP) field experiment in 2010 which sampled Hurricane Karl, and will next be co-located on the same aircraft for the subsequent NASA HS3 experiment. The High Altitude Wind and Rain Profiling Radar (HIWRAP) is a conically scanning Doppler radar mounted upon NASAs Global Hawk unmanned aerial vehicle, and the usefulness of its radial velocity data for assimilation has not been previously examined. Since the radar scans from above with a fairly large fixed elevation angle, it observes a large component of the vertical wind, which could degrade EnKF analyses compared to analyses with data taken from lesser elevation angles. The NASA Hurricane Imaging Radiometer (HIRAD) is a passive microwave radiometer similar to SFMR, and measures emissivity and retrieves hurricane surface wind speeds and rain rates over a much wider swath. Thus, this study examines the impact of assimilating simulated HIWRAP radial velocity data into an EnKF system, simulated HIRAD wind speed, and HIWRAP+HIRAD with the Weather Research and Forecasting (WRF) model and compares the results to no data assimilation and also to the Truth from which the data was simulated for both instruments.

Albers, Cerese↗
NASA NTRS2014

Hurricane Karl's Structure and Some Thoughts for 2014 Strategy

Karl has interesting data, but far below the standards we should be able to achieve in HS3. We need to fly AV-1 over hurricanes in 2014. Most of the cold cloud shield in the inner core of hurricanes should be safe for AV-1 to fly. Significant convection occupies a small region, but we sometimes unnecessarily apply the 5000-ft separation rule to the entire cold cloud shield.

Cecil, Dan↗
NASA NTRS2012

Observations of C-Band Brightness Temperature and Ocean Surface Wind Speed and Rain Rate in Hurricanes Earl And Karl (2010)

Ocean surface emission is affected by: a) Sea surface temperature. b) Wind speed (foam fraction). c) Salinity After production of calibrated Tb fields, geophysical fields wind speed and rain rate (or column) are retrieved. HIRAD utilizes NASA Instrument Incubator Technology: a) Provides unique observations of sea surface wind, temp and rain b) Advances understanding & prediction of hurricane intensity c) Expands Stepped Frequency Microwave Radiometer capabilities d) Uses synthetic thinned array and RFI mitigation technology of Lightweight Rain Radiometer (NASA Instrument Incubator) Passive Microwave C-Band Radiometer with Freq: 4, 5, 6 & 6.6 GHz: a) Version 1: H-pol for ocean wind speed, b) Version 2: dual ]pol for ocean wind vectors. Performance Characteristics: a) Earth Incidence angle: 0deg - 60deg, b) Spatial Resolution: 2-5 km, c) Swath: approx.70 km for 20 km altitude. Observational Goals: WS 10 - >85 m/s RR 5 - > 100 mm/hr.

Miller, Timothy↗
NASA NTRS2013

NASA's Genesis and Rapid Intensification Processes (GRIP) Field Experiment

In August–September 2010, NASA, NOAA, and the National Science Foundation (NSF) conducted separate but closely coordinated hurricane field campaigns, bringing to bear a combined seven aircraft with both new and mature observing technologies. NASA's Genesis and Rapid Intensification Processes (GRIP) experiment, the subject of this article, along with NOAA's Intensity Forecasting Experiment (IFEX) and NSF's Pre-Depression Investigation of Cloud-Systems in the Tropics (PREDICT) experiment, obtained unprecedented observations of the formation and intensification of tropical cyclones. The major goal of GRIP was to better understand the physical processes that control hurricane formation and intensity change, specifically the relative roles of environmental and inner-core processes. A key focus of GRIP was the application of new technologies to address this important scientific goal, including the first ever use of the unmanned Global Hawk aircraft for hurricane science operations. NASA and NOAA conducted coordinated flights to thoroughly sample the rapid intensification (RI) of Hurricanes Earl and Karl. The tri-agency aircraft teamed up to perform coordinated flights for the genesis of Hurricane Karl and Tropical Storm Matthew and the non-redevelopment of the remnants of Tropical Storm Gaston. The combined GRIP–IFEX–PREDICT datasets, along with remote sensing data from a variety of satellite platforms [Geostationary Operational Environmental Satellite (GOES), Tropical Rainfall Measuring Mission (TRMM), Aqua, Terra, CloudSat, and Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO)], will contribute to advancing understanding of hurricane formation and intensification. This article summarizes the GRIP experiment, the missions flown, and some preliminary findings.

hurricane↗
NASA NTRS2014

Hurricane Imaging Radiometer

The Hurricane Imaging Radiometer (HIRAD) is a synthetic thinned array passive microwave radiometer designed to allow retrieval of surface wind speed in hurricanes, up through category five intensity. The retrieval technology follows the Stepped Frequency Microwave Radiometer (SFMR), which measures surface wind speed in hurricanes along a narrow strip beneath the aircraft. HIRAD has flown in the NASA Genesis and Rapid Intensification Processes (GRIP) experiement in 2010 on a WB-57 aircraft, and on a Global Hawk unmanned aircraft system (UAS) in 2012 and 2013 as part of NASA's Hurricane and Severe Storms Sentinel (HS3) program. The GRIP program included flights over Hurricanes Earl and Karl (2010). The 2012 HS3 deployment did not include any hurricane flights for the UAS carrying HIRAD. Hurricane flights are expected for HIRAD in 2013 during HS3. This presentation will describe the HIRAD instrument, its results from the 2010 hurricane flights, and hopefully results from hurricane flights in August and September 2013.

Cecil, Daniel J.↗
NASA NTRS2014

Hurricane Imaging Radiometer

The Hurricane Imaging Radiometer (HIRAD) is a synthetic thinned array passive microwave radiometer designed to allow retrieval of surface wind speed in hurricanes, up through category five intensity. The retrieval technology follows the Stepped Frequency Microwave Radiometer (SFMR), which measures surface wind speed in hurricanes along a narrow strip beneath the aircraft. HIRAD maps wind speeds in a swath below the aircraft, about 50-60 km wide when flown in the lower stratosphere. HIRAD has flown in the NASA Genesis and Rapid Intensification Processes (GRIP) experiment in 2010 on a WB-57 aircraft, and on a Global Hawk unmanned aircraft system (UAS) in 2012 and 2013 as part of NASA's Hurricane and Severe Storms Sentinel (HS3) program. The GRIP program included flights over Hurricanes Earl and Karl (2010). The 2012 HS3 deployment did not include any hurricane flights for the UAS carrying HIRAD. The 2013 HS3 flights included one flight over the predecessor to TS Gabrielle, and one flight over Hurricane Ingrid. This presentation will describe the HIRAD instrument, its results from the 2010 and 2013 flights, and potential future developments.

Cecil, Daniel J.↗
NASA NTRS2011

APR-2 Tropical Cyclone Observations

The Second Generation Airborne Precipitation Radar (APR-2) participated in the Genesis and Rapid Intensification Processes (GRIP) experiment in August and September of 2010, collecting a large volume of data in several tropical systems, including Hurricanes Earl and Karl. Additional measurements of tropical cyclone have been made by APR-2 in experiments prior to GRIP (namely, CAMEX-4, NAMMA, TC4); Table 1 lists all the APR-2 tropical cyclone observations. The APR-2 observations consist of the vertical structure of rain reflectivity at 13.4 and 35.6 GHz, and at both co-polarization and crosspolarization, as well as vertical Doppler measurements and crosswind measurements. APR-2 normally flies on the NASA DC-8 aircraft, as in GRIP, collecting data with a downward looking, cross-track scanning geometry. The scan limits are 25 degrees on either side of the aircraft, resulting in a roughly 10-km swath, depending on the aircraft altitude. Details of the APR-2 observation geometry and performance can be found in Sadowy et al. (2003).The multiparameter nature of the APR-2 measurements makes the collection of tropical cyclone measurements valuable for detailed studies of the processes, microphysics and dynamics of tropical cyclones, as well as weaker systems that are associated with tropical cyclone formation. In this paper, we give a brief overview of how the APR-2 data are processed. We also discuss use of the APR-2 cross-track winds to estimate various quantities of interest in in studies of storm intensification. Finally, we show examples of the standard products and derived information.

radar↗
NASA NTRS2006

Hurricane Intensity Forecasts with a Global Mesoscale Model on the NASA Columbia Supercomputer

It is known that General Circulation Models (GCMs) have insufficient resolution to accurately simulate hurricane near-eye structure and intensity. The increasing capabilities of high-end computers (e.g., the NASA Columbia Supercomputer) have changed this. In 2004, the finite-volume General Circulation Model at a 1/4 degree resolution, doubling the resolution used by most of operational NWP center at that time, was implemented and run to obtain promising landfall predictions for major hurricanes (e.g., Charley, Frances, Ivan, and Jeanne). In 2005, we have successfully implemented the 1/8 degree version, and demonstrated its performance on intensity forecasts with hurricane Katrina (2005). It is found that the 1/8 degree model is capable of simulating the radius of maximum wind and near-eye wind structure, and thereby promising intensity forecasts. In this study, we will further evaluate the model s performance on intensity forecasts of hurricanes Ivan, Jeanne, Karl in 2004. Suggestions for further model development will be made in the end.

Shen, Bo-Wen↗
NASA NTRS2018

Hurricane Imaging Radiometer (HIRAD) Wind Speed Retrievals and Assessment Using Dropsondes

The Hurricane Imaging Radiometer (HIRAD) is an experimental C-band passive microwave radiometer designed to map the horizontal structure of surface wind speed fields in hurricanes. New data processing and customized retrieval approaches were developed after the 2015 Tropical Cyclone Intensity (TCI) experiment, which featured flights over Hurricanes Patricia, Joaquin, Marty, and the remnants of Tropical Storm Erika. These new approaches produced maps of surface wind speed that looked more realistic than those from previous campaigns. Dropsondes from the High Definition Sounding System (HDSS) that was flown with HIRAD on a WB-57 high altitude aircraft in TCI were used to assess the quality of the HIRAD wind speed retrievals. The root mean square difference between HIRAD-retrieved surface wind speeds and dropsonde-estimated surface wind speeds was 6.0 meters per second. The largest differences between HIRAD and dropsonde winds were from data points where storm motion during dropsonde descent compromised the validity of the comparisons. Accounting for this and for uncertainty in the dropsonde measurements themselves, we estimate the root mean square error for the HIRAD retrievals as around 4.7 meters per second. Prior to the 2015 TCI experiment, HIRAD had previously flown on the WB-57 for missions across Hurricanes Gonzalo (2014), Earl (2010), and Karl (2010). Configuration of the instrument was not identical to the 2015 flights, but the methods devised after the 2015 flights may be applied to that previous data in an attempt to improve retrievals from those cases.

wind retrieval↗
NASA NTRS2012

Observations of C-band Brightness Temperatures and Ocean Surface Wind Speed and Rain Rate from the Hurricane Imaging Radiometer (HIRAD)

HIRAD flew on the WB-57 over Earl and Karl during NASA s GRIP (Genesis and Rapid Intensification Processes) campaign in August - September of 2010. HIRAD is a new Cband radiometer using a synthetic thinned array radiometer (STAR) technology to obtain cross-track resolution of approximately 3 degrees, out to approximately 60 degrees to each side of nadir. (The resulting swath width for a platform at 60,000 feet is roughly 60 km, and resolution for most of the swath is around 2 km.) By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface wind speed and rain rate can be retrieved. This technique has been used for many years by precursor instruments, including the Stepped Frequency Microwave Radiometer (SFMR), which has been flying on the NOAA and USAF hurricane reconnaissance aircraft for several years to obtain observations within a single footprint at nadir angle. Results from the flights during the GRIP campaign will be shown, including images of brightness temperatures, wind speed, and rain rate. Comparisons will be made with observations from other instruments on the GRIP campaign, for which HIRAD observations are either directly comparable or are complementary. Features such as storm eye and eyewall, location of storm wind and rain maxima, and indications of dynamical features such as the merging of a weaker outer wind/rain maximum with the main vortex may be seen in the data. Potential impacts on operational ocean surface wind analyses and on numerical weather forecasts will also be discussed.

Miller, Timothy L.↗
NASA NTRS2014

Hurricane Imaging Radiometer Wind Speed and Rain Rate Retrievals during the 2010 GRIP Flight Experiment

Microwave remote sensing observations of hurricanes, from NOAA and USAF hurricane surveillance aircraft, provide vital data for hurricane research and operations, for forecasting the intensity and track of tropical storms. The current operational standard for hurricane wind speed and rain rate measurements is the Stepped Frequency Microwave Radiometer (SFMR), which is a nadir viewing passive microwave airborne remote sensor. The Hurricane Imaging Radiometer, HIRAD, will extend the nadir viewing SFMR capability to provide wide swath images of wind speed and rain rate, while flying on a high altitude aircraft. HIRAD was first flown in the Genesis and Rapid Intensification Processes, GRIP, NASA hurricane field experiment in 2010. This paper reports on geophysical retrieval results and provides hurricane images from GRIP flights. An overview of the HIRAD instrument and the radiative transfer theory based, wind speed/rain rate retrieval algorithm is included. Results are presented for hurricane wind speed and rain rate for Earl and Karl, with comparison to collocated SFMR retrievals and WP3D Fuselage Radar images for validation purposes.

Sahawneh, Saleem↗