Spatial information of high-frequency brightness temperatures for passive microwave rainfall retrievals

2011 ◽  
Vol 32 (19) ◽  
pp. 5347-5363 ◽  
Author(s):  
Dong-Bin Shin
Keyword(s):  
High Frequency ◽  
Spatial Information ◽  
Passive Microwave ◽  
Brightness Temperatures

scholarly journals Microwave signatures of ice hydrometeors from ground-based observations above Summit, Greenland

2015 ◽  
Vol 15 (23) ◽  
pp. 34497-34532
Author(s):  
C. Pettersen ◽  
R. Bennartz ◽  
M. S. Kulie ◽  
A. J. Merrelli ◽  
M. D. Shupe ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
Temperature Difference ◽  
Liquid Water ◽  
High Frequency ◽  
Passive Microwave ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Cloud Radar ◽  
Brightness Temperatures ◽  
High Frequency Microwave

Abstract. Multi-instrument, ground-based measurements provide unique and comprehensive datasets of the atmosphere for a specific location over long periods of time and resulting data compliments past and existing global satellite observations. This paper explores the effect of ice hydrometeors on ground-based, high frequency passive microwave measurements and attempts to isolate an ice signature for summer seasons at Summit, Greenland from 2010–2013. Data from a combination of passive microwave, cloud radar, radiosonde, and ceilometer were examined to isolate the ice signature at microwave wavelengths. By limiting the study to a cloud liquid water path of 40 g m−2 or less, the cloud radar can identify cases where the precipitation was dominated by ice. These cases were examined using liquid water and gas microwave absorption models, and brightness temperatures were calculated for the high frequency microwave channels: 90, 150, and 225 GHz. By comparing the measured brightness temperatures from the microwave radiometers and the calculated brightness temperature using only gas and liquid contributions, any residual brightness temperature difference is due to emission and scattering of microwave radiation from the ice hydrometeors in the column. The ice signature in the 90, 150, and 225 GHz channels for the Summit Station summer months was isolated. This measured ice signature was then compared to an equivalent brightness temperature difference calculated with a radiative transfer model including microwave single scattering properties for several ice habits. Initial model results compare well against the four years of summer season isolated ice signature in the high-frequency microwave channels.

scholarly journals Beyond the Pixel: Using Patterns and Multiscale Spatial Information to Improve the Retrieval of Precipitation from Spaceborne Passive Microwave Imagers

2020 ◽  
Vol 37 (9) ◽  
pp. 1571-1591 ◽  
Author(s):  
Clément Guilloteau ◽  
Efi Foufoula-Georgiou
Keyword(s):  
Spatial Information ◽  
Quantitative Estimation ◽  
Passive Microwave ◽  
Temporal Organization ◽  
Brightness Temperatures ◽  
Retrieval Scheme ◽  
Statistical Relationships ◽  
Convective Cells ◽  
Convolution Filters ◽  
Observation Geometry

AbstractThe quantitative estimation of precipitation from orbiting passive microwave imagers has been performed for more than 30 years. The development of retrieval methods consists of establishing physical or statistical relationships between the brightness temperatures (TBs) measured at frequencies between 5 and 200 GHz and precipitation. Until now, these relationships have essentially been established at the “pixel” level, associating the average precipitation rate inside a predefined area (the pixel) to the collocated multispectral radiometric measurement. This approach considers each pixel as an independent realization of a process and ignores the fact that precipitation is a dynamic variable with rich multiscale spatial and temporal organization. Here we propose to look beyond the pixel values of the TBs and show that useful information for precipitation retrieval can be derived from the variations of the observed TBs in a spatial neighborhood around the pixel of interest. We also show that considering neighboring information allows us to better handle the complex observation geometry of conical-scanning microwave imagers, involving frequency-dependent beamwidths, overlapping fields of view, and large Earth incidence angles. Using spatial convolution filters, we compute “nonlocal” radiometric parameters sensitive to spatial patterns and scale-dependent structures of the TB fields, which are the “geometric signatures” of specific precipitation structures such as convective cells. We demonstrate that using nonlocal radiometric parameters to enrich the spectral information associated to each pixel allows for reduced retrieval uncertainty (reduction of 6%–11% of the mean absolute retrieval error) in a simple k-nearest neighbors retrieval scheme.

scholarly journals Microwave signatures of ice hydrometeors from ground-based observations above Summit, Greenland

2016 ◽  
Vol 16 (7) ◽  
pp. 4743-4756 ◽  
Author(s):  
Claire Pettersen ◽  
Ralf Bennartz ◽  
Mark S. Kulie ◽  
Aronne J. Merrelli ◽  
Matthew D. Shupe ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
Temperature Difference ◽  
Liquid Water ◽  
High Frequency ◽  
Passive Microwave ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Cloud Radar ◽  
Brightness Temperatures ◽  
High Frequency Microwave

Abstract. Multi-instrument, ground-based measurements provide unique and comprehensive data sets of the atmosphere for a specific location over long periods of time and resulting data compliment past and existing global satellite observations. This paper explores the effect of ice hydrometeors on ground-based, high-frequency passive microwave measurements and attempts to isolate an ice signature for summer seasons at Summit, Greenland, from 2010 to 2013. Data from a combination of passive microwave, cloud radar, radiosonde, and ceilometer were examined to isolate the ice signature at microwave wavelengths. By limiting the study to a cloud liquid water path of 40 g m−2 or less, the cloud radar can identify cases where the precipitation was dominated by ice. These cases were examined using liquid water and gas microwave absorption models, and brightness temperatures were calculated for the high-frequency microwave channels: 90, 150, and 225 GHz. By comparing the measured brightness temperatures from the microwave radiometers and the calculated brightness temperature using only gas and liquid contributions, any residual brightness temperature difference is due to emission and scattering of microwave radiation from the ice hydrometeors in the column. The ice signature in the 90, 150, and 225 GHz channels for the Summit Station summer months was isolated. This measured ice signature was then compared to an equivalent brightness temperature difference calculated with a radiative transfer model including microwave single-scattering properties for several ice habits. Initial model results compare well against the 4 years of summer season isolated ice signature in the high-frequency microwave channels.

scholarly journals The Estimation of Hydrometeor Profiles from Wideband Microwave Observations

2000 ◽  
Vol 39 (10) ◽  
pp. 1645-1656 ◽  
Author(s):  
Gail M. Skofronick-Jackson ◽  
James R. Wang
Keyword(s):  
High Frequency ◽  
Cloud Water ◽  
Tropical Ocean ◽  
Low Frequencies ◽  
High Frequencies ◽  
Atmospheric Research ◽  
Brightness Temperatures ◽  
Microphysical Properties ◽  
Ice Microphysics ◽  
Updraft Region

Abstract Profiles of the microphysical properties of clouds and rain cells are essential in many areas of atmospheric research and operational meteorology. To enhance the understanding of the nonlinear and underconstrained relationships between cloud and hydrometeor microphysical profiles and passive microwave brightness temperatures, estimations of cloud profiles for an anvil region, a convective region, and an updraft region of an oceanic squall were performed. The estimations relied on comparisons between radiative transfer calculations of incrementally estimated microphysical profiles and concurrent dual-altitude wideband brightness temperatures from the 22 February 1993 flight during the Tropical Ocean and Global Atmosphere Coupled Ocean–Atmosphere Response Experiment. The wideband observations (10–220 GHz) are necessary for estimating cloud profiles reaching up to 20 km. The low frequencies enhance the rain and cloud water profiles, and the high frequencies are required to detail the higher-altitude ice microphysics. A microphysical profile was estimated for each of the three regions of the storm. Each of the three estimated profiles produced calculated brightness temperatures within ∼10 K of the observations. A majority of the total iterative adjustments were to the estimated profile’s frozen hydrometeor characteristics and were necessary to match the high-frequency calculations with the observations. This requirement indicates a need to validate cloud-resolving models using high frequencies. Some difficulties matching the 37-GHz observation channels on the DC-8 and ER-2 aircraft with the calculations simulated at the two aircraft heights (∼11 km and 20 km, respectively) were noted, and potential causes were presented.

scholarly journals Effect of Structural Uncertainty in Passive Microwave Soil Moisture Retrieval Algorithm

Sensors ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 1225
Author(s):  
Lanka Karthikeyan ◽  
Ming Pan ◽  
Dasika Nagesh Kumar ◽  
Eric F. Wood
Keyword(s):  
Soil Moisture ◽  
Global Scale ◽  
Passive Microwave ◽  
Radiative Transfer Model ◽  
Retrieval Algorithm ◽  
Transfer Model ◽  
Structural Uncertainty ◽  
Three Solutions ◽  
Brightness Temperatures ◽  
Retrieval Algorithms

Passive microwave sensors use a radiative transfer model (RTM) to retrieve soil moisture (SM) using brightness temperatures (TB) at low microwave frequencies. Vegetation optical depth (VOD) is a key input to the RTM. Retrieval algorithms can analytically invert the RTM using dual-polarized TB measurements to retrieve the VOD and SM concurrently. Algorithms in this regard typically use the τ-ω types of models, which consist of two third-order polynomial equations and, thus, can have multiple solutions. Through this work, we find that uncertainty occurs due to the structural indeterminacy that is inherent in all τ-ω types of models in passive microwave SM retrieval algorithms. In the process, a new analytical solution for concurrent VOD and SM retrieval is presented, along with two widely used existing analytical solutions. All three solutions are applied to a fixed framework of RTM to retrieve VOD and SM on a global scale, using X-band Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) TB data. Results indicate that, with structural uncertainty, there ensues a noticeable impact on the VOD and SM retrievals. In an era where the sensitivity of retrieval algorithms is still being researched, we believe the structural indeterminacy of RTM identified here would contribute to uncertainty in the soil moisture retrievals.

scholarly journals Passive microwave-derived spatial and temporal variations of summer melt on the Greenland ice sheet

1993 ◽  
Vol 17 ◽  
pp. 233-238 ◽  
Author(s):  
Thomas L. Mote ◽  
Mark R. Anderson ◽  
Karl C. Kuivinen ◽  
Clinton M. Rowe
Keyword(s):  
Time Series ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Late Summer ◽  
Temporal Variations ◽  
Early Summer ◽  
Passive Microwave ◽  
Brightness Temperatures ◽  
Surface Melt ◽  
Major Surface

Passive microwave-brightness temperatures over the Greenland ice sheet are examined during the melt season in order to develop a technique for determining surface-melt occurrences. Time series of Special Sensor Microwave/ Imager (SSM/I) data are examined for three locations on the ice sheet, two of which are known to experience melt. These two sites demonstrate a rapid increase in brightness temperatures in late spring to early summer, a prolonged period of elevated brightness temperatures during the summer, and a rapid decrease in brightness temperatures during late summer. This increase in brightness temperatures is associated with surface snow melting. An objective technique is developed to extract melt occurrences from the brightness-temperature time series. Of the two sites with summer melt, the site at the lower elevation had a longer period between the initial and final melt days and had more total days classified as melt during 1988 and 1989. The technique is then applied to the entire Greenland ice sheet for the first major surface-melt event of 1989. The melt-zone signal is mapped from late May to early June to demonstrate the advance and subsequent retreat of one “melt wave”. The use of such a technique to determine melt duration and extent for multiple years may provide an indication of climate change.

Distinct Subsystems for the Parafoveal Processing of Spatial and Linguistic Information during Eye Fixations in Reading

2003 ◽  
Vol 56 (5) ◽  
pp. 803-827 ◽  
Author(s):  
Albrecht W. Inhoff ◽  
Ralph Radach ◽  
Brianna M. Eiter ◽  
Barbara Juhasz
Keyword(s):  
Eye Movement ◽  
High Frequency ◽  
Word Length ◽  
Spatial Information ◽  
Low Frequency ◽  
Visual Object ◽  
Additive Effects ◽  
Linguistic Information ◽  
Object Selection ◽  
Eye Fixations

Two experiments examined readers’ use of parafoveally obtained word length information for word recognition. Both experiments manipulated the length (number of constituent characters) of a parafoveally previewed target word so that it was either accurately or inaccurately specified. In Experiment 1, previews also either revealed or denied useful orthographic information. In Experiment 2, parafoveal targets were either high- or low-frequency words. Eye movement contingent display changes were used to show the intact target upon its fixation. Examination of target viewing duration showed completely additive effects of word length previews and of ortho-graphic previews in Experiment 1, viewing duration being shorter in the accurate-length and the orthographic preview conditions. Experiment 2 showed completely additive effects of word length and word frequency, target viewing being shorter in the accurate-length and the high-frequency conditions. Together these results indicate that functionally distinct subsystems control the use of parafoveally visible spatial and linguistic information in reading. Parafoveally visible spatial information appears to be used for two distinct extralinguistic computations: visual object selection and saccade specification.

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