Suleiman Alsweiss

Hurricane Imaging Radiometer Wide Swath Simulation for Wind Speed and Rain Rate

There is a strong national interest in the observation of ocean surface winds with high spatial and temporal resolution for understanding tropical cyclones and their effects on weather and climate and in forecasting storms making landfall. Current satellite and aircraft based remote sensing capability is limited in wind speed dynamic range and in the ability to retrieve wind information in the presence of rain, or in temporal and spatial coverage, respectively. The hurricane imaging radiometer (HIRAD) is capable to capture all the hurricane features and dynamics from a high altitude aircraft preserving high resolution measurements. A detailed description of the methods used in simulating the HIRAD instrument surface sampling of wind speed, in intense rain, from various aircraft platforms with realistic operational flight patterns through a time evolving hurricane will be provided in this paper. A noise model used to simulate the effects of rain for various observation path lengths over the swath will also be described. Results will demonstrate the extent of spatial and temporal coverage available from currently available aircraft platforms.

Stepped frequency microwave radiometer retrieval error characterization

The Stepped Frequency Microwave Radiometer (SFMR) is an instrument flown on research and reconnaissance aircraft through tropical and extratropical cyclones providing rain rate and surface wind speed estimates. Errors have been observed with the retrievals from SFMR, especially in extratropical cyclones over cold water, when compared with other sensors. In this paper, some of the SFMR wind speed errors that manifest over cold water are characterized using comparisons with in situ measurements by dropwindsondes.

A Non-MLE Approach for Satellite Scatterometer Wind Vector Retrievals in Tropical Cyclones

Satellite microwave scatterometers are the principal source of global synoptic-scale ocean vector wind (OVW) measurements for a number of scientific and operational oceanic wind applications. However, for extreme wind events such as tropical cyclones, their performance is significantly degraded. This paper presents a novel OVW retrieval algorithm for tropical cyclones which improves the accuracy of scatterometer based ocean surface winds when compared to low-flying aircraft with in-situ and remotely sensed observations. Unlike the traditional maximum likelihood estimation (MLE) wind vector retrieval technique, this new approach sequentially estimates scalar wind directions and wind speeds. A detailed description of the algorithm is provided along with results for ten QuikSCAT hurricane overpasses (from 2003-2008) to evaluate the performance of the new algorithm. Results are compared with independent surface wind analyses from the National Oceanic and Atmospheric Administration (NOAA) Hurricane Research Divisions H*Wind surface analyses and with the corresponding SeaWinds Projects L2B-12.5 km OVW products. They demonstrate that the proposed algorithm extends the SeaWinds capability to retrieve wind speeds beyond the current range of approximately 35 m/s (minimal hurricane category-1) with improved wind direction accuracy, making this new approach a potential candidate for current and future conically scanning scatterometer wind retrieval algorithms.

A Novel Ku-Band Radiometer/Scatterometer Approach for Improved Oceanic Wind Vector Measurements

This paper presents a conceptual conical-scanning radiometer/scatterometer (RadScat) instrument design for the purpose of improving satellite ocean vector wind retrievals under rain-free conditions. This technique combines the wind vector signature in the passive linearly polarized ocean brightness temperatures with the anisotropic signature of multiazimuthal radar cross-sectional measurements to retrieve oceanic surface wind vectors. The performance of the RadScat is evaluated using a Monte Carlo simulation based on actual measurements from the SeaWinds scatterometer and the Advanced Microwave Scanning Radiometer onboard the Advanced Earth Observing Satellite II. The results demonstrate significant improvements in wind vector retrievals, particularly in the near-subtrack swath, where the performance of conical-scanning scatterometers degrades.

Improved hurricane active/passive simulated wind vector retrievals

Microwave scatterometers are the standard for satellite ocean vector winds (OVW) measurements, and they provide the major source of global ocean surface winds observations for scientific and operational applications. A major challenge for Ku-band scatterometry missions is to provide reliable retrievals in the presence of precipitation, particularly in extreme ocean wind events that are usually associated with intense rain. This paper explores the advantages of combining dual frequency (C- and Ku-band) scatterometer measurements and passive microwave observations to improve high wind speed retrievals. For this study, a conceptual design proposed by the Jet Propulsion Laboratory for a Dual Frequency Scatterometer (DFS) to fly onboard the future Japan Aerospace Exploration Agency (JAXA) GCOM-W2 mission with the Advanced Microwave Scanning Radiometer (AMSR) was adopted. A computer simulation that combines the DFS and AMSR measurements was used to develop an artificial neural network OVW retrieval algorithm. The Weather Research and Forecasting (WRF) numerical weather model of Hurricane Katrina (2005) was used as the nature run (surface truth), and simulated OVW retrievals demonstrate that this new technique offers a robust option to extend the useful wind speed measurements range beyond the current operating scatterometers for future satellite missions.

Simulations for a wide swath synthetic aperture microwave radiometric imaging of wind speed and rain rate in hurricanes

There is a strong national interest in the observation of ocean surface winds with high spatial and temporal resolution for understanding tropical cyclones and their effects on weather and climate. In this paper, we will describe the details of an end-to-end simulation to support the development of the future airborne microwave Hurricane Imaging Radiometer (HIRAD). This new instrument will extend the measurements of the Stepped Frequency Microwave Imager (SFMR) from nadir looking only to a wide swath storm coverage of ± 60° earth incidence angel (EIA). A comprehensive simulation of the instrument radiances measurements during a hurricane overflight was developed based on realistic 3-D hurricane atmosphere and surface wind field using numerical weather models especially tunes to characterize hurricane environment. Afterwards, the simulated measurements were perturbed with instrument errors and input to the Maximum Likelihood Estimation (MLE) retrieval algorithm. Results will show statistical analysis and comparisons of the retrieved wind speeds and rain rates for different swath locations.

An improved active/passive oceanic wind vector retrieval technique

This paper describes the advantages of combining passive and active microwave remote sensing observations for the purpose of ocean wind vectors retrievals. Previous studies have shown that a linear combination of horizontal and vertical polarized brightness temperatures contains a robust wind direction signal. In this paper, we present results from an end-to-end simulation of ocean measurements from a Ku-band (13.4 GHz) active/passive conical scanning satellite instrument. For this simulation, realistic wind fields from the NOAA National Center for Environmental Prediction (NCEP) numerical weather model were used to produce simultaneous brightness temperatures and radar backscatter measurements. These measurements were processed using a maximum likelihood estimation technique to yield ocean wind vector retrievals that were compared to NCEP fields. Results demonstrate significant improvements over simulated measurements for an active (radar scatterometer) sensor.

Improved high wind speed retrievals using AMSR and the next generation NASA Dual Frequency Scatterometer

Microwave scatterometer measurements are the standard for satellite ocean vector winds (OVW) measurements. Unfortunately, in extreme weather events, where high wind speeds are frequently associated with strong rain bands, precipitation can significantly degrade the OVW retrieval accuracy. This study addresses the feasibility of exploiting passive measurements to improve high wind speed retrievals for such extreme weather events. The Jet Propulsion Laboratory (JPL) has developed a conceptual design for a Dual Frequency Scatterometer (DFS) proposed to fly onboard the future Japan Aerospace Exploration Agency (JAXA) GCOM-W2 mission with the Advanced Microwave Scanning Radiometer (AMSR). These two instruments will provide a complimentary dataset of simultaneous and coincident active/passive measurements, which can correct for rain effects and thereby improve the OVW retrievals. End-to-end computer simulations are performed using the Weather Research and Forecasting (WRF) numerical weather model tuned to Hurricane Katrina (2005) for the 3D nature run (surface truth). Results show that the new OVW retrievals compare well to the nature run surface wind vectors and that this active/passive technique offers a robust option to extend the useful wind speed measurements range beyond the current operating scatterometers for future satellite missions.

A Ku-Band Active/Passive Wind Vector Retrieval Over the Ocean

This work investigates the design of an innovative conical scanning Ku-band (13.4 GHz) scatterometer/radiometer for measuring ocean vector winds. The sensor design is based upon actual measurements obtained by the SeaWinds scatterometer and the Advanced Microwave Scanning Radiometer (AMSR), which operated simultaneously on JAXAs Advanced Earth Observing Satellite-II (ADEOS-II) during 2003. This new design combines the conventional forward and aft-looking two-beam microwave scatterometer (SeaWinds) measurements with simultaneous linearly polarized passive microwave brightness temperatures. The unique aspect of this remote sensing technique is that it operates at a single microwave frequency, and it combines vertical and horizontal polarized microwave brightness temperatures with the scatterometer normalized cross sections to retrieve unambiguous ocean wind vectors. This technique has the potential to significantly improve the Ocean Vector Winds retrievals for future conical-scanning microwave scatterometers.

Suitability of the amazon rain forest as an on-orbit, microwave radiometric calibration target

Passive microwave sensors known as radiometers are calibrated receivers that make absolute measurements of weak natural blackbody noise power emissions to infer geophysical properties of the Earths atmosphere and surface. Because of the high accuracy needed in measuring these geophysical parameters, frequent on-orbit radiometric calibrations over natural surfaces with stable radiometric emissions are highly desirable. This paper discusses the suitability of the Amazon rain forest as such a radiometric calibration target. Results of analysis of on-orbit microwave radiometer measurements from the Amazon are presented to demonstrate repeatable temporal and spatial emission signatures that can be used for radiometric calibration.