Microwave radiometer Research Papers - Academia.edu (original) (raw)

2025, Optical Engineering

This contribution investigates the effectiveness of optical communication links in enabling high-speed data transfer from deep-space (DS) probes directly to Earth ground stations. In particular, the propagation impairments induced by clouds are estimated by exploiting long-term radiosonde observation data collected in some European sites. The impact of different cloud types on optical links operating at 1.55 μm is first quantified in terms of total path attenuation, and afterward, the implementation of multisite diversity schemes is discussed to counteract the extremely high attenuation levels caused by clouds. Results show that a three-site diversity system with target availability of 90% allows reduction of the link margin to counteract cloud attenuation from at least 40 dB to ∼6 dB, which makes optical communications a viable option also for DS missions.

2025, Eos, Transactions American Geophysical Union

trends rests on high-quality measurements. It is perhaps surprising that credible answers to the second question also rely on highly accurate measurements. Our knowledge of future climate is based on predictions of climate models. But forecasts of future climate differ depending on the model used. For example, predicted temperature changes by the end of the century vary by over a factor of two. How do we know which model to trust? Establishing credibility is critical to decisions on responding to climate change. We can do it the same way we evaluate weather predictions: by checking the forecasts against what really happens. The reliability of climate predictions can be ascertained by testing decadal climate trends predicted by the models against observations. But, as emphasized above, the changes are small, and such tests can only be performed with highly accurate observations. And satellite observations from space provide the only measurements with the needed global perspective.

2025, Hydrological Processes

An evaluation of the Biosphere±Atmosphere Transfer Scheme (BATS) snow submodel was conducted, both in a stand-alone mode and within the National Center for Atmospheric Research (NCAR) Community Climate Model version 3 (CCM3). We evaluated, in the stand-alone mode, the performance of BATS parameterizations at local scales using ground-based observations from the former Soviet Union and from Mammoth Mountain, California. The BATS snow scheme reproduces well the seasonal evolution of snow water equivalent in both sites, and the results for the Mammoth Mountain site compare well with those from a more complex, physically based model (SNTHERM). In the coupled mode, we evaluated the modelled snow cover extent, snow mass, precipitation and temperature from BATS as linked to the NCAR CCM3 using available observations. The coupled models capture the broad pattern of seasonal and geographical distribution of snow cover, with better overall performance than the passive microwave snow data derived from the Nimbus-7 Scanning Multi-channel Microwave Radiometer (SMMR) which generally underestimates snow depth. In terms of continents, the snow mass is better simulated during the accumulation period than during the melt period, which is the case for both North America and Eurasia. The simulation of snow mass, precipitation and air temperature for North America is slightly better than that for Eurasia. A rigorous evaluation of snow simulations in coupled land±atmosphere models requires high quality global datasets of snow cover extent, snow depth and snow water equivalent. The available datasets and model outputs are not yet ready to ful®l this objective.

2025

A more rigorous multilayered cloud retrieval system has been developed to improve the determination of high cloud properties in multilayered clouds. The MCRS attempts a more realistic interpretation of the radiance field than earlier methods because it explicitly resolves the radiative transfer that would produce the observed radiances. A two-layer cloud model was used to simulate multilayered cloud radiative characteristics. Despite the use of a simplified two-layer cloud reflectance parameterization, the MCRS clearly produced a more accurate retrieval of ice water path than simple differencing techniques used in the past. More satellite data and ground observation have to be used to test the MCRS. The MCRS methods are quite appropriate for interpreting the radiances when the high cloud has a relatively large optical depth (tau(sub I) greater than 2). For thinner ice clouds, a more accurate retrieval might be possible using infrared methods. Selection of an ice cloud retrieval and ...

2025, Hydrology and Earth System Sciences

The first products derived over France in 2010 from the L-band brightness temperatures (T b ) measured by the SMOS (Soil Moisture and Ocean Salinity) satellite, launched in November 2009, were compared with the surface soil moisture (SSM) estimates produced by the C-band Advanced Scatterometer, ASCAT, launched in 2006 on board METOP-A. SMOS and ASCAT SSM products were compared with the simulations of the ISBA-A-gs model and with in situ measurements from the SMOSMANIA network, including 21 stations located in southern France. ASCAT tended to correlate better than SMOS with ISBA-A-gs. The significant anomaly correlation coefficients between in situ observations and the SMOS (ASCAT) product ranged from 0.23 to 0.48 (0.35 to 0.96). However, in wet conditions, similar results between the two satellite products were found. An attempt was made to derive SSM from regressed empirical logarithmic equations using a combination of SMOS T b at different incidence angles and different polarizations, and the Leaf Area Index (LAI) modeled by ISBA-A-gs. The analysis of the intercept coefficient of the regression showed an impact of topography. A similar analysis applied to ASCAT and SMOS SSM values showed a more limited impact of topography on the intercept coefficient of the SMOS SSM product, while fewer residual geographic patterns were found for the ASCAT SSM.

2025, AIP Conference Proceedings

2025

Monthly distributions of surface latent heat flux and solar irradiance in the tropical Pacific were computed from observations of the Scanning Multichannel Microwave Radiometer on Nimbus-7 and the Visible Infrared Spin Scan Radiometer on GOES-W. They are the dominant variable components of the surface heat flux, the sum of which gives the approximate thermal forcing on the ocean.

2025

The Hurricane Imaging Radiometer (HIRAD) is an experimental, airborne, microwave remote sensor that was developed to measure hurricane surface wind speed and rain rate, and thereby, provide data for scientific research and for the next generation operational hurricane surveillance. The object of this dissertation is to develop objective procedures and techniques that can be used to evaluate and characterize the HIRAD brightness temperature (Tb) image product provided by NASA MSFC. To my beloved mother, brothers and sisters To my friends and family To my lovely son David and my princess Rosalie And to my dearest wife Mais. v ACKNOWLEDGMENTS I would like to thank my advisor, Prof. W. Linwood Jones, for his hard work, dedication and support that guided me throughout these past five years towards my degree. His continuous support, encouragement, trust and vision greatly helped me towards my success. There is a lot that I learned from him and anybody who has the chance to work with him realizes how helpful and supportive he is. I also would like to thank my committee members, Dr. Wasfy Mikhael, Dr. Parveen Wahid, Dr. Josko Zec and Dr. Daniel Cecil for their advice, guidance and time. Many thanks to the Marshal Space Flight Center (MSFC) for their support throughout this process and especially to Dr. Sayak Biswas who provided me with all HIRAD data that I needed and answered all of my questions. Finally, special thanks for the Central Florida Remote Sensing Laboratory (CFRSL) team who showed support and willingness to help when needed. LIST O F FIGURES .

2025, 2014 13th Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment (MicroRad)

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 [1]. 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.

2025, 2013 IEEE International Geoscience and Remote Sensing Symposium - IGARSS

The Hurricane Imaging Radiometer (HIRAD) is an airborne passive microwave radiometer designed to provide high resolution, wide swath imagery of surface wind speed in tropical cyclones from a low profile planar antenna with no mechanical scanning. Wind speed and rain rate images from HIRAD's first field campaign (GRIP, 2010) are presented here followed, by a discussion on the performance of the newly installed thermal control system during the 2012 HS3 campaign. The paper ends with a discussion on the next generation dual polarization HIRAD antenna (already designed) for a future system capable of measuring wind direction as well as wind speed.

2025, 2013 Proceedings of IEEE Southeastcon

This dissertation presents results for an end-to-end computer simulation of a new airborne microwave remote sensor, the Hurricane Imaging Radiometer, HIRAD, which will provide improved hurricane surveillance. The emphasis of this research is the retrieval of hurricane-force wind speeds in the presence of intense rain and over long atmospheric slant path lengths that are encountered across its wide swath. Brightness temperature (T b ) simulations are performed using a forward microwave radiative transfer model (RTM) that includes an ocean surface emissivity model at high wind speeds developed especially for HIRAD high incidence angle measurements and a rain model for the hurricane environment. Also included are realistic sources of errors (e.g., instrument NEDT, antenna pattern convolution of scene T b , etc.), which are expected in airborne hurricane observations. Case studies are performed using 3D environmental parameters produced by numerical hurricane models for actual hurricanes. These provide realistic "nature runs" of rain, water vapor, clouds and surface winds from which simulated HIRAD T b 's are derived for various flight tracks from a high altitude aircraft. Using these simulated HIRAD measurements, Monte Carlo retrievals of wind speed and rain rate are performed using available databases of sea surface temperatures and climatological hurricane atmospheric parameters (excluding rain) as a priori information. Examples of retrieved hurricane wind speed and rain rate images are presented, and comparisons of the retrieved parameters with the numerical model data are made. Statistical results are presented over a broad range of wind and rain conditions and as a function of path length over the full swath.

2025

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...

2025

The Joint Center for Satellite Data Assimilation (JCSDA) was established by NASA and NOAA in 2001, with the DoD becoming a partner in 2002. The goal of the JCSDA is to accelerate the use of observations from earth-orbiting satellites in operational numerical analysis and prediction models for the purpose of improving weather forecasts, improving seasonal to interannual climate forecasts, and increasing the accuracy of climate data sets. Advanced instruments of the current and planned satellite missions, do and will increasingly provide large volumes of data related to atmospheric, oceanic, and land surface state. These data will exhibit accuracies and spatial, spectral and temporal resolutions never before achieved. The JCSDA will ensure that the maximum benefit from investment in space is realised from the advanced global observing system. It will also help accelerate the use of satellite data from both operational and experimental spacecraft for weather and climate related activities. To this end the advancement of data assimilation science by JCSDA has included the establishment of the JCSDA Community Radiative Transfer Model (CRTM) and continual upgrades including, the incorporation of AIRS and snow and ice emissivity models for improving the use of microwave sounding data over high latitudes, preparation for use of METOP IASI/AMSU/HSB, DMSP SSMIS and CHAMP GPS data, real-time delivery of EOS-Aqua AMSR-E to NWP centers, and improved physically based SST analyses. Eighteen other research projects are also being supported by the JCSDA (e.g. use of cloudy radiances from advanced satellite instruments) to develop a state of-the-art satellite data assimilation system. The work undertaken by the JCSDA represents a key component of GEOSS. In particular data assimilation, data impact studies, OSSEs, THORPEX and network design studies are key activities of GEOSS. Recent advances at the JCSDA including the demonstration of the benefits in the Northern and Southern Hemisphere of AIRS radiance assimilation on NCEP GFS forecasts, demonstration of the benefits of MODIS Polar atmospheric motion vector assimilation on NCEP GFS forecasts and the beneficial impact of the CRTM's modeling of sea ice and snow emissivity are recorded below.

2025, Remote Sensing

Data from automated meteorological instruments are used for model validation and aviation applications, but their measurement accuracy has not being adequately tested. In this study, a number of ground-based in-situ, remote-sensing instruments that measure visibility (VIS), cloud base height (CBH), and relative humidity (RH) were tested against data obtained using standard reference instruments and human observations at Cold Lake Airport, Alberta, Canada. The instruments included the Vaisala FS11P and PWD22 (FSPW), a profiling microwave radiometer (MWR), the Jenoptik ceilometer, Rotronic, Vaisala WXT520, AES-Dewcell RH, and temperature sensors. The results showed that the VIS measured using the FSPWs were well correlated with a correlation coefficient (R) of 0.84 under precipitation conditions and 0.96 during non-precipitating conditions (NPC), indicating very good agreement. However, the FS11P on average measured higher VIS, particularly under NPC. When the FSPWs were compared agai...

2025, Journal of Infrared, Millimeter, and Terahertz Waves

This paper presents measurements using a dual-polarised radiometer operating at 93 GHz to detect ice or water on asphalt in laboratory conditions. The brightness temperatures of both H and V polarizations were measured for a dry surface, liquid water, and ice on asphalt at observation angles of 50° and 56°. The results presented in this paper demonstrate that the studied road conditions can be identified by the radiometer. The measurements are compared with a model and surface parameters, such as dielectric constant and roughness are fitted and compared to reference values. The experiments and results, described in this article, are the first steps towards the future installation of a polarimetric sensor on a moving vehicle for traffic safety.

2025, Atmospheric Research

Tropospheric observations by a microwave profiling radiometer and six-hour radiosondes were obtained during the Alpine Venue of the 2010 Winter Olympic Games at Whistler, British Columbia, by Environment Canada. The radiometer provided continuous temperature, humidity and liquid (water) profiles during all weather conditions including rain, sleet and snow. Gridded analysis was provided by the U.S. National Oceanic and Atmospheric Administration. We compare more than two weeks of radiometer neural network and radiosonde temperature and humidity soundings including clear and precipitating conditions. Corresponding radiometer liquid and radiosonde wind soundings are shown. Close correlation is evident between radiometer and radiosonde temperature and humidity profiles up to 10 km height and among southwest winds, liquid water and upper level thermodynamics, consistent with up-valley advection and condensation of moist maritime air. We compare brightness temperatures observed by the radiometer and forward-modeled from radiosonde and gridded analysis. Radiosonde-equivalent observation accuracy is demonstrated for radiometer neural network temperature and humidity retrievals up to 800 m height and for variational retrievals that combine radiometer and gridded analysis up to 10 km height.

2025, Monthly Notices of the Royal Astronomical Society

We present an application of the Fast Independent Component Analysis (FASTICA) method to the Cosmic Background Explorer Differential Microwave Radiometer (COBE-DMR) 4-yr data. Although the signal-to-noise (S/N) ratio in the COBE-DMR data is typically ∼1, the approach is able to extract the cosmic microwave background (CMB) signal with high confidence from high galactic latitude regions. However, the foreground emission components have too low a S/N ratio to be reconstructed by this method (moreover, the number of components which can be reconstructed is directly limited by the number of input channels). The reconstructed CMB map shows the expected frequency scaling of the CMB and, fitting for the rms quadrupole normalization Q rms-PS and primordial spectral index n we find results in excellent agreement with those derived from the minimum-noise combination of the 90and 53-GHz DMR channels without galactic emission correction. We extend the analysis by including additional channels (priors): the Haslam map of radio emission at 408 MHz and the Diffuse Infrared Background Experiment (DIRBE) 140-µm map of galactic infrared emission. The FASTICA algorithm is now able to both detect galactic foreground emission and separate it from the dominant CMB signal. Fitting again for Q rms-PS and n we find good agreement with the results of Górski et al. where galactic emission has been taken into account by means of correlation analysis of the DMR signal. We investigate the ability of FASTICA to evaluate the extent of foreground contamination in the COBE-DMR data further including an all-sky Hα survey to determine a reliable freefree. The derived frequency scalings of the recovered foregrounds are consistent with previous correlation studies. After subtraction of the thermal dust emission as in model 7 of Finkbeiner, Davis & Schlegel, we find a clear indication of an anomalous dust-correlated component which is the dominant foreground emission at 31.5 GHz and which is well fitted by a power-law spectral shape ν -β with β ∼ 2.5 in agreement with Banday et al.

2025, The Astrophysical Journal

Likelihood analyses of the COBE Differential Microwave Radiometer (DMR) sky maps are used to determine the normalization of the inverse-power-law potential scalar-field dark energy model. Predictions of the DMR-normalized model are compared with various observations to constrain the allowed range of model parameters. Although the derived constraints are restrictive, evolving dark energy density scalar-field models remains an observationally viable alternative to the constant cosmological constant model. Subject headings: cosmic microwave background -cosmology: observationslarge-scale structure of universe

2025, IEEE Transactions on Geoscience and Remote Sensing

The stability and accuracy of the TOPEX Microwave Radiometer (TMR) measurement of the atmospheric path delay due to water vapor is assessed over the interval from launch (August 1992) through June 1998. Detailed global comparisons are made with path delays derived from the special sensor microwave imager (SSM/I) instruments and a network of 15 island radiosondes. The results provide consistent evidence that the TMR path delay measurements included an instrument-related downward drift of 1.0-1.5 mm/yr between October 1992 and December of 1996. The four-year drift correlates with an upward drift seen in the coldest TMR 18-GHz brightness temperature time series and is further supported by independent comparisons of TMR with ERS-1 and 2, GPS, and the Harvest Platform water vapor radiometer measurements. From January 1997 through June 1998, no significant relative path delay drift between TMR and SSM/I is seen in the comparison data, although anomalies do appear in early 1998. In terms of accuracy, both the SSM/I and radiosonde comparisons indicate no significant ( 2%) scale error in the TMR path delay. An overall bias of 10 mm may be present, but the comparisons are not consistent in this determination.

2025, AIP Conference Proceedings

2025, Atmospheric Measurement Techniques

CO mixing ratios for the lowermost 2-km atmospheric layer were retrieved from downwelling infrared (IR) radiance spectra of the clear sky measured between 2002 and 2009 by a zenith-viewing Atmospheric Emitted Radiance Interferometer (AERI) deployed at the Southern Great Plains (SGP) observatory of the Atmospheric Radiation Measurements (ARM) Program near Lamont, Oklahoma. A version of a published earlier retrieval algorithm was improved and validated. Archived temperature and water vapor profiles retrieved from the same AERI spectra through automated ARM processing were used as input data for the CO retrievals. We found the archived water vapor profiles required additional constraint using SGP Microwave Radiometer retrievals of total precipitable water vapor. A correction for scattered solar light was developed as well. The retrieved CO was validated using simultaneous independently measured CO profiles from an aircraft. These tropospheric CO profiles were measured from the surface to altitudes of 4572 m a.s.l. once or twice a week between March 2006 and December 2008. The aircraft measurements were supplemented with ground-based CO measurements using a non-dispersive infrared gas correlation instrument at the SGP and retrievals from the Atmospheric IR Sounder (AIRS) above 5 km to create full tropospheric CO profiles. Comparison of the profiles convolved with averaging kernels to the AERI CO retrievals found a squared correlation coefficient of 0.57, a standard deviation of ±11.7 ppbv, a bias of -16 ppbv, and a slope of

2025, Sensors

In this paper, the SOMOSTA (Soil Moisture Monitoring Station) experiment on the intercomparison of soil moisture monitoring from Global Navigation Satellite System Reflectometry (GNSS-R) signals and passive L-band microwave radiometer observations at the Valencia Anchor Station is introduced. The GNSS-R instrument has an up-looking antenna for receiving direct signals from satellites, and a dual-pol down-looking antenna for receiving LHCP (left-hand circular polarization) and RHCP (right-hand circular polarization) reflected signals from the soil surface. Data were collected from the three different antennas through the two channels of Oceanpal GNSS-R receiver and, in addition, calibration was performed to reduce the impact from the differing channels. Reflectivity was thus measured, and soil moisture could be retrieved. The ESA (European Space Agency)-funded ELBARA-II (ESA L Band Radiometer II) is an L-band radiometer with two channels with 11 MHz bandwidth and respective center fr...

2025, 2007 IEEE International Geoscience and Remote Sensing Symposium

2025, Hydrological Processes

2025

As part of our efforts to characterize the cloud properties at the North Slope of Alaska (NSA) Cloud and Radiation Testbed (CART), we have used microwave radiometers (MWRs) and multi-filter rotating shadowband radiometers (MFRSRs) at... more

2025, Journal of Geophysical Research

2025, IEEE Transactions on Geoscience and Remote Sensing

Since 1981, the Wave Propagation Laboratory of NOAA has operated a ground-based zenith-viewing microwave radiometer. This radiometer, designed to measure precipitable water vapor, cloud liquid, and temperature profiles, has two moisture-sensing channels and four temperature-sounding channels. Data from this system, taken at Denver, Colorado, are used to derive geopotential heights and thick- nesses from the surface (about 830 mbar) to 300 mbar. Time series and spectra of several directly measured and inferred quantities are analyzed for different meteorological situations: a period of unusual calm in surface pressure, a frontal passage, and a gravity wave event. The three cases presented illustrate how rapid variations in meteoro- logical variables can be studied using ground-based radiometers. These radiometers provide temporal continuity not hitherto available. The performance of the radiometer, both in observing a blackbody target and during an unusually calm pressure event, shows high sensitivity to changes in geopotential height and thickness and to integrated water vapor. Consequently, the combination of high temporal resolution and high sensitivity allows unique monitoring of rapidly changing condi- tions, such as frontal passages and gravity wave events. Comparisons of these data with various sources of ground truth, including radio- sondes, satellite cloud observations, and arrays of microbarographs, show excellent agreement.

2025, EPJ Web of Conferences

The Planetary Boundary Layer (PBL) is the lowermost part of the troposphere. In this work, we analysed some high order moments and PBL height detected continuously by three remote sensing systems: an elastic lidar, a Doppler lidar and a passive Microwave Radiometer, during the SLOPE-2016 campaign, which was held in Granada from May to August 2016. This study confirms the feasibility of these systems for the characterization of the PBL, helping us to justify and understand its behaviour along the day.

2025, Journal of Geophysical Research: Atmospheres

The SeaWinds scatterometer, launched onboard the QuikSCAT satellite in 1999, measures global ocean vector winds. In addition to measuring radar backscatter, SeaWinds simultaneously measures the microwave brightness temperature of the atmosphere/surface, and this passive microwave measurement capability is known as the QuikSCAT Radiometer (QRad). This paper presents a QRad retrieval algorithm used to infer instantaneous oceanic rain rates. This statistical algorithm is trained using near‐simultaneous observations of major rain events by QRad and the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI). Rain rate retrieval algorithm validation is presented through comparisons with independent rain measurements from the TMI 2A12 surface rain rates and the TRMM 3B42RT composite microwave and visible and infrared near‐real time data product. Results demonstrate that QRad rain rate measurements are in good agreement with these independent microwave rain observations and super...

2025, IEEE Transactions on Geoscience and Remote Sensing

2025

Inter-Calibration and Validation of Operational Sensors 4:45 PM Motivation NASA LaRC is processing the 20+ year GOES IR & Visible data record with an automated hazardous storm detection algorithm in order to understand the temporal/spatial distribution of these storms and how they've changed over time (Bedka and Khlopenkov, JAMC, 2016) Stable IR and Visible calibration is critical to minimize sensorinduced trends Accurate characterization of the Earth's radiant energy is critical for many climate monitoring and weather forecasting applications -E.g., GOES-based overshooting top climatology relies on stable 11-μm brightness temperature (BT) measurements since GOES-8 -Especially on the cold end, i.e. 220 vs. 290 K -Anomalies must be recognized and mitigated -Consistent intra-series and inter-platform calibrations

2025

NASA Langley Research Center NOAA Climate Data Record Program Calibration FCDR Specifications • Gains produced monthly using 5 methods Desert, Polar snow invariant targets (IT) Deep convective clouds (DCC) Simultaneous Nadir Overpass (SNO) w/ Aqua MODIS Merged DCC & IT results • Monthly mean gains, g, 1978-2012 • Polynomial fits to monthly means, fn(dsl) m = m0 + m1•dsl + m2•dsl Inputs to Calibration FCDR • Re-navigated Advanced Very High Resolution Radiometer (AVHRR) 0.63, 0.86, and 1.6-μm brightness counts, C • Observational geometric conditions, date • Invariant site reflectance models, SBAFs • DCC BRDF models • Spectral solar constant, launch date, Co

2025, American Geophysical Union (AGU) Fall Meeting

2025

Since its first launching, the ability of satellite Altimetry in providing reliable and accurate ocean geophysical information of the sea surface height (SSH), significant wave height (SWH), and wind speed has been proven by numerous research, as it was designed for observing the ocean dynamics through nadir range measurement between satellite and the sea surface. However, to achieve high level accuracy, environmental and geophysical effects on the range measurement must be accurately determined and corrected, in particularly the effects from the atmospheric water vapor which can divert altimeter range up to 3–45 cm. Thus, satellite Altimetry is originally equipped by the on-board microwave radiometer to measure the water vapour content for correcting the range measurement. To our knowledge, no one has attempted to apply the on-board radiometer for atmospheric studies. In this present work, we attempt to optimize the on-board radiometer data for studying the atmosphere variability d...

2025, Research Square (Research Square)

In the past few decades, satellite altimetry has surpassed tremendous achievements in examining the mesoscale of ocean dynamics. Recently, new potential of the satellite in observing the variability of climate phenomena through atmospheric medium been unlocked. As it has been ascertained that satellite altimetry not only outstanding in monitoring ocean dynamic, but also in observing atmospheric variability, we intuitively propose a hypothesis that satellite altimetry is reliable in monitoring Bjerknes feedback; a feedback loop involving interaction between atmosphere and oceans. Thus, the aim of this study is to determine the capability of satellite altimetry in observing Bjerknes feedback through Precipitable Water Vapour (PWV) and Sea Level Anomaly (SLA) during the anomalous climate mode of Indian Ocean Dipole (IOD). The results signify the convincing arguments as both PWV and SLA indexes have high correlation with Dipole Mode Index (DMI), particularly in the west region of Indian Ocean; 0.67 and 0.62, respectively. The correlation of PWV and SLA indexes are also significantly high; 0.73 and 0.69 in west and east region, respectively. The Principal Component Analysis (PCA) results are also convincing as the spatial pattern of primary (PC1) and secondary (PC2) components of both PWV and SLA are associated with positive and negative IOD, respectively. The temporal pattern of PC1 for PWV and SLA have relatively high correlation with positive IOD. The substantially high temporal correlation (0.81) between PWV and SLA PC1 has reinforce the confidence in the capability of satellite altimetry in observing the Bjerknes feedback.

2025, ESASP

The LEGOS based OSCAR project (observing continental surfaces with radar altimetry) delivers a validation of the ENVISAT RA2 altimetry, in particular over Antarctic and Greenland. We investigated the stability and reliability of every correction on the altimetric measurements. Here we show the investigations on the dry troposphere correction. Although the overall trend in this correction is difficult to qualify, we found large unreliability of this correction at smaller scale on the Antarctic icecap. Large jumps are observed at cycle 40 and 55 of the satellite's life local trends of very significant and suspect values are found as well. We show the results of our investigations and map the impact this suspect correction has on the surface height changes. The impact is found to be non negligible and locally very significant. We investigate the possibility to re-compute a correction with the ECMWF pressure fields and show the improvement on the height recovery and height change surveys.

2025, Geophysical Research Letters

Atmospheric water vapor can also be measured using GPS [Dixon and Kornreich Wolf, 1m; Bevis et aI., 1992]. PWV ranges from O. 60 mm. We show that GPS can estimate PWV with mm accuracy every 30 minutes. PWV measurements of this accuracy and frequency are useful for meteorology and hold promise to aid in the estimation of vertical watel" vapor profiles [Kuo et aI., 1993]. Because of rapid developments in GPS technology, water vapor monitoring GPS networks may become cost-effective. GPS receivers spaced at 50-500 kin could provide 30-minute water vapor data that could be assimilated into numerical weather forecasts.

2025

• A measurement time series of sufficient length, consistency, accuracy, precision, and continuity to determine climate variability and change • Satellite CDRs possess the accuracy, longevity, and stability for sustained monitoring of critical variables to enhance understanding of the global integrated Earth system and predict future conditions. • Satellite CDRs are a critical element of a global climate observing system. • Satellite CDRs are a difficult challenge and require high-level managerial commitment, extensive intellectual capital, and adequate funding. CDR • Long-term data record involving a series of platforms, such as satellite and insitu instruments each with different performance characteristics, usually with different space and time sampling, time extent, and stability • Overlaps and calibrations sufficient for generation of homogeneous and wellcharacterized global data products that are stable for climate monitoring • Includes metadata used for calibration National Research Council (2004)

2025

The Back End Module at 30 GHz for the Planck mission has been manufactured in its Qualification Model version. Design, integration and main performances are described. Electrical, thermal and vibration tests, already done for space qualification, are summarised. This module consists basically in four identical branches based on broadband low noise amplification, direct detection and video amplification.

2025, Annals of the New York Academy of Sciences

2025, EPJ Web of Conferences

Accurate measurements of the vertical profiles of water vapour are of paramount importance for most key areas of atmospheric sciences. A comprehensive inter-comparison between different remote sensing and in-situ sensors has been carried out in the frame work of the first Special Observing Period of the Hydrological cycle in the Mediterranean Experiment for the purpose of obtaining accurate error estimates for these sensors. The inter-comparison involves a ground-based Raman lidar (BASIL), an airborne DIAL (LEANDRE2), a microwave radiometer, radiosondes and aircraft in-situ sensors.

2025

The utilization of the altimetric satellite’s on-board radiometer for atmospheric observation is demonstrated. This study uses the Wet Tropospheric Correction (WTC) data from the Topex/Jason altimetry mission series (Topex/Poseidon, Jason-1, Jason-2/OSTM, and Jason-3). The data spans nearly 30 years, making them sufficient for climate study. Precipitable Water Vapor (PWV) is derived from the WTC and used to study the water vapor variability over the Tropical Indian Ocean (TIO). Standard EOF (Empirical Orthogonal Function) analysis on the derived PWV anomaly (PWVA) in the TIO generates two leading modes. The first mode has a dipole spatial structure that explains 18.3% of the total variance, and the second one has a basin-wide homogeneous structure that explains 12.3% of the total variance. Correlation analysis with IOD and ENSO monitoring indices has shown that these two modes are associated with the two interannual variabilities. Further analyses using composite techniques are done...

2025, Proceedings. 2005 IEEE International Geoscience and Remote Sensing Symposium, 2005. IGARSS '05.

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2025, IEEE Geoscience and Remote Sensing Letters

We quantify the performance of three commonly used techniques to calibrate ground-based microwave radiometers for soil moisture studies, external (EC), tipping-curve (TC), and internal (IC). We describe two ground-based C-band radiometer systems with similar design and the calibration experiments conducted in Florida and Alaska using these two systems. We compare the consistency of the calibration curves during the experiments among the three techniques and evaluate our calibration by comparing the measured brightness temperatures (T B 's) to those estimated from a lake emission model (LEM). The mean absolute difference among the T B 's calibrated using the three techniques over the observed range of output voltages during the experiments was 1.14 K. Even though IC produced the most consistent calibration curves, the differences among the three calibration techniques were not significant. The mean absolute errors (MAE) between the observed and LEM T B 's were about 2-4 K. As expected, the utility of TC at C-band was significantly reduced due to transparency of the atmosphere at these frequencies. Because IC was found to have a MAE of about 2 K that is suitable for soil moisture applications and was consistent during our experiments under different environmental conditions, it could augment less frequent calibrations obtained using the EC or TC techniques.

2025

Speed biases in Atmospheric Motion Vectors (AMVs) are discussed in a data assimilation context, and the biases are characterised in detail in terms of the atmospheric environment. There is evidence that the speed biases are related to height assignment problems and the use of a suboptimal observation operator. A statistical scheme is suggested to correct the biases in the extra-tropics through a First Guess dependent height reassignment and a revised observation operator. The concepts are tested within the ECMWF data assimilation system. The speed bias and root mean square vector difference can be significantly reduced through the height reassignment and the revised observation operator which uses layer averaging rather than interpolation to a single level. The concepts lead to a more symmetrical distribution of First Guess departures. Preliminary forecast experiments show a mainly neutral forecast impact from the revised assimilation of METEOSAT-5 and 7 AMVs. The changes allow a detailed revision of various aspects of the assimilation of AMVs such as quality control procedures and observation errors. 1 Throughout this contribution, "high level" refers to "above 400 hPa", and "middle level" to "700-400 hPa". Also, "extra-tropics" refers to the region outside 20 • latitude, and "tropics" within 20 • latitude, unless indicated otherwise.