An Ocean Surface Wind Vector Model Function For A Spaceborne Microwave Radiometer And Its Application

Ocean surface wind vectors over the ocean present vital information for scientists and forecasters in their attempt to understand the Earth\u27s global weather and climate. As the demand for global wind velocity information has increased, the number of satellite missions that carry wind-measuring sensors has also increased; however, there are still not sufficient numbers of instruments in orbit today to fulfill the need for operational meteorological and scientific wind vector data. Over the last three decades operational measurements of global ocean wind speeds have been obtained from passive microwave radiometers. Also, vector ocean surface wind data were primarily obtained from several scatterometry missions that have flown since the early 1990\u27s. However, other than SeaSat-A in 1978, there has not been combined active and passive wind measurements on the same satellite until the launch of the second Advanced Earth Observing Satellite (ADEOS-II) in 2002. This mission has provided a unique data set of coincident measurements between the SeaWinds scatterometer and the Advanced Microwave Scanning Radiometer (AMSR). AMSR observes the vertical and horizontal brightness temperature (TB) at six frequency bands between 6.9 GHz and 89.0 GHz. Although these measurements contain some wind direction information, the overlying atmospheric influence can easily obscure this signal and make wind direction retrieval from passive microwave measurements very difficult. However, at radiometer frequencies between 10 and 37 GHz, a certain linear combination of vertical and horizontal brightness temperatures causes the atmospheric dependence to be nearly cancelled and surface parameters such as wind speed, wind direction and sea surface temperature to dominate the resulting signal. This brightness temperature combination may be expressed as ATBV-TBH, where A is a constant to be determined and the TBV and TBH are the brightness temperatures for the vertical and horizontal polarization respectively. In this dissertation, an empirical relationship between the AMSR\u27s ATBV-TBH and SeaWinds\u27 surface wind vector retrievals was established for three microwave frequencies: 10, 18 and 37 GHz. This newly developed model function for a passive microwave radiometer could provide the basis for wind vector retrievals either separately or in combination with scatterometer measurements

An Ocean Surface Wind Vector Model Function For A Spaceborne Microwave Radiometer

Surface wind vector measurements over the oceans are vital for scientists and forecasters to understand the Earth\u27s global weather and climate. In the last two decades, operational measurements of global ocean wind speeds were obtained from passive microwave radiometers (Special Sensor Microwave/Imagers); and over this period, full ocean surface wind vector data were obtained from several National Aeronautics and Space Administration and European Space Agency scatterometry missions. However, since SeaSat-A in 1978, there have not been other combined active and passive wind measurements on the same satellite until the launch of Japan Aerospace Exploration Agency\u27s Advanced Earth Observing Satellite-II in 2002. This mission provided a unique data set of coincident measurements between the SeaWinds scatterometer and the Advanced Microwave Scanning Radiometer (AMSR). The AMSR instrument measured linearly polarized brightness temperatures (TB) over the ocean. Although these measurements contained wind direction information, the overlying atmospheric influence obscured this signal and made wind direction retrievals not feasible. However, for radiometer channels between 10 and 37 GHz, a certain linear combination of vertical and horizontal brightness temperatures causes the atmospheric dependence to cancel and surface parameters such as wind speed and direction and sea surface temperature to dominate the resulting signal. In this paper, an empirical relationship between AMSR TB\u27s (specifically A • TBv - TBH) and surface wind vectors (inferred from SeaWinds\u27 retrievals) is established for three microwave frequencies: 10, 18, and 37 GHz. This newly developed wind vector model function for microwave radiometers can serve as a basis for wind vector retrievals either separately or in combination with active scatterometer measurements. © 2007 IEEE

Ocean Surface Wind Vector Retrievals Using Active And Passive Microwave Sensing On Adeos-Ii

Conventional multiple-azimuth-look space-borne scatterometers have been used to retrieve ocean surface wind vector for over three decades. However, the requirement for the antenna to view both forward and aft has made the scatterometer a difficult instrument to accommodate on remote sensing satellites with multiple earth-viewing sensors. In this paper, we present a new technique for ocean surface wind vector measurement using a single-azimuth-look combined active and passive microwave sensing from space. We demonstrate this methodology by using actual measurements of the ocean normalized radar cross section (sigma-0) and the radiometer-inferred wind magnitude respectively from the SeaWinds scatterometer and the Advanced Microwave Scanning Radiometer (AMSR) on-board the Advanced Earth Observing Satellite (ADEOS-II). For the scatterometer measurements, only the forward look, in the same direction as the AMSR measurements, is used. Owing to the biharmonic nature of the scatterometer anisotropic Geophysical Model Function (GMF), the retrieved wind direction consists of as many as four possible wind directions (aliases) at each wind vector cell (WVC). Alias selection is presented and performance is measured by comparison of the selected to the standard wind vector product from SeaWinds. Statistical analyses are performed and results show that it is feasible to measure ocean surface wind vector using single look geometry. © 2005 IEEE

Combined Active And Passive Microwave Sensing Of Ocean Surface Wind Vector From Trmm

This paper presents a new ocean wind vector measurement technique that uses the combined passive and active microwave measurements respectively from the Tropical Rainfall Measuring Mission (TRMM) Microwave mager (TMI) and the Precipitation Radar (PR). The wind speed is inferred by TMI over a wide swath that includes the narrower PR swath. The PR scans cross-track ±18°; and near the swath edges, where the radar backscatter responds to both the magnitude and direction of the surface wind, we use the microwave radiometer estimate of wind speed and the measured sigma-0 at incidence angles greater than 15 degrees to derive wind direction. Because the PR provides only a single azimuth look, multiple possible wind direction solutions exist. The ability to select the proper (single) direction is beyond the scope of this paper; but comparisons are presented between the closest retrieved TRMM wind vectors and near-simultaneous wind vectors measured by the QuikSCAT satellite scatterometer to demonstrate the potential for measuring ocean surface vector winds

Development Of Oceanic Wind Vector Model Function For Amsr Radiometer On Adeos-Ii Satellite

Since the advent of the first spaceborne wind scatterometers on NASA\u27s SeaSat mission in 1978, the Advanced Earth Observing Satellite (ADEOS)-II was the first satellite mission that carried both microwave scatterometer and radiometer imagers. This provided a unique opportunity to explore the possibility of combined technology for oceanic surface wind vector measurements. In contrast to conventional scatterometry that require both forward and aft multi-azimuth look measurements, our technique use only forward look radar backscatter measurement combine with collocated brightness temperature measurements to retrieve wind direction. This single-look configuration would be highly beneficial for future satellite mission to obtain improved observation of both oceanic and atmospheric information. Microwave radiometers are well-known instrument for atmospheric and oceanic physical parameters retrieval. Although, the vertical and horizontal brightness temperatures are weakly dependent on wind direction, it has been shown that certain linear combinations of vertical and horizontal brightness temperatures are almost indepentdent of the atmosphere and are predominantly a function of wind speed, direction and sea surface temperature (SST). The empirical relationship for these brightness temperatures was developed for the Advaced Microwave Scanning Radiometer (AMSR) on ADEOS-II. In addition to passive measurement, coincident radar backscatter from foreward look SeaWinds scatterometer was combined to retrieve the wind directions. The wind direction retrieval algorithm and statistical results are presented

Validation of ocean surface wind vector sensing using combined active and passive microwave measurements

A new ocean surface wind vector measurement has been developed using combined active and passive microwave measurements from the TRMM satellite. In this method, collocated ocean normalized radar backscatter from the Precipitation Radar (PR) and retrieved wind speeds from the TRMM Microwave Imager (TMI) are used to derive ocean wind direction. Since PR provides only a single azimuth look, multiple wind direction solutions exists; but we compare the "closest" retrieved wind direction with near-simultaneous surface truth from three ocean buoy networks, namely; National Data Buoy Center (NDBC), Tropical Atmosphere Ocean (TAO), and Pilot Research moored Array in the Tropical Atlantic (PIRATA). Comparisons are also presented for QuikSCAT wind vector retrievals

A Novel Active And Passive Microwave Remote Sensing Technique For Measuring Ocean Surface Wind Vector

This paper describes a novel technique of ocean surface vector wind measurement using active and passive microwave sensing from a satellite. For over a decade, satellite microwave scatterometers have remotely sensed ocean wind vector (speed and direction) by measuring ocean radar backscatter (sigma-0) at several different azimuth angles (looking forward and aft). Also, ocean wind speeds have been measured by conical scanning passive microwave radiometers looking either forward or aft. This paper combines these two techniques to obtain wind speed and direction from a conical scanning instrument that scans either forward or aft, which is extremely desirable from an instrument design and satellite accommodations standpoint. An overview of the active/passive wind vector algorithm is discussed, and wind vector retrievals are presented using microwave measurements from Japan\u27s ADEOS-II satellite. These results are compared with wind vectors from the SeaWinds scatterometer

Combined Active And Passive Microwave Sensing Of Ocean Surface Wind Vector From Trmm

This paper presents a new ocean wind vector measurement technique that uses the combined passive and active microwave measurements respectively from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and the Precipitation Radar (PR). The wind speed is inferred by TMI over a wide swath that includes the narrower PR swath. The PR scans cross-track ± 18°; and near the swath edges, where the radar backscatter responds to both the magnitude and direction of the surface wind, we use the microwave radiometer estimate of wind speed and the measured sigma-0 at incidence angles greater than 15 degrees to derive wind direction. Because the PR provides only a single azimuth look, multiple possible wind direction solutions exist. The ability to select the proper (single) direction is beyond the scope of this paper; but comparisons are presented between the closest retrieved TRMM wind vectors and near-simultaneous wind vectors measured by the QuikSCAT satellite scatterometer to demonstrate the potential for measuring ocean surface vector winds

Development of Oceanic Wind Vector Model Function for AMSR Radiometer on ADEOS-II Satellite

Since the advent of the first spaceborne wind scatterometers on NASA\u27s SeaSat mission in 1978, the Advanced Earth Observing Satellite (ADEOS)-II was the first satellite mission that carried both microwave scatterometer and radiometer imagers. This provided a unique opportunity to explore the possibility of combined technology for oceanic surface wind vector measurements. In contrast to conventional scatterometry that require both forward and aft multi-azimuth look measurements, our technique use only forward look radar backscatter measurement combine with collocated brightness temperature measurements to retrieve wind direction. This single-look configuration would be highly beneficial for future satellite mission to obtain improved observation of both oceanic and atmospheric information. Microwave radiometers are well-known instrument for atmospheric and oceanic physical parameters retrieval. Although, the vertical and horizontal brightness temperatures are weakly dependent on wind direction, it has been shown that certain linear combinations of vertical and horizontal brightness temperatures are almost indepentdent of the atmosphere and are predominantly a function of wind speed, direction and sea surface temperature (SST). The empirical relationship for these brightness temperatures was developed for the Advaced Microwave Scanning Radiometer (AMSR) on ADEOS-II. In addition to passive measurement, coincident radar backscatter from foreward look SeaWinds scatterometer was combined to retrieve the wind directions. The wind direction retrieval algorithm and statistical results are presented