Microwave Radiometer And Radar Measurements In The SAAMEX Campaign (original) (raw)
Passive microwave measurements of snow-covered forest areas in EMAC'95
IEEE Transactions on Geoscience and Remote Sensing, 1999
Airborne passive-microwave signatures collected in Northern Finland during EMAC-95 are analyzed with the emphasis on forested areas and dry snow conditions. The microwave signatures cover the 6.8-18.7-GHz frequency range and were acquired at both vertical and horizontal polarizations. The analysis is carried out with respect to the forest-stem volume data and comprises three different snow-depth situations. Emissivities approach saturation limit with the increasing stem volume. At 10.65 GHz, the saturation level was found to be linearly related to the snow-water equivalent. On the basis of passive-microwave measurements, an empirical forest transmissivity model is developed. The model is valid at vertical polarization 50 incidence angle, and it accounts for microwave frequency and forest-stem volume effects in the range of 6.8-94 GHz and 0-150 m 3 /ha, respectively. 1996. He currently is working toward the Ph.D degree at the Helsinki University of Technology (HUT), Espoo, Finland.
On the use of microwave observations over land at Météo-France
Satellite microwave measurements have large atmospheric and surface information contents and are known to be very useful for Numerical Weather Prediction (NWP). However these observations are still not fully used over land because of non negligeable uncertainties about land emissivity and surface temperature. Recent developments have been carried out at Météo-France in order to propose new methods for land emissivity and surface temperature modelling anchored on satellite microwave observations. The methods are based on (1) the use of averaged emissivity estimates calculated within the assimilation system two weeks prior to the assimilation period; (2) the dynamic computation of emissivity for each atmospheric situation for a selection of surface channels and the allocation of this estimate to remaining surface and sounding channels, and (3) the use of emissivity from method (1) and the dynamic adjustment of surface temperature using observations from selected surface sensitive channels.
TOPEX microwave radiometer performance evaluation, 1992-1998
IEEE Transactions on Geoscience and Remote Sensing, 2000
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 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 < 10 mm may be present, but the comparisons are not consistent in this determination.
IEEE Transactions on Geoscience and Remote Sensing, 2000
Satellite data are the most suitable tools for monitoring time and spatial variations of snow covered areas. At present, our knowledge of the microwave emission from the ice sheet at the lower frequencies is limited by the lack of satellite sensors and by our inadequate knowledge of the physical effects governing emission. On other hand, in addition to the interest related to climatic changes, and to glaciological and hydrological applications, there is growing interest, on the part of the remote sensing community, in using the Antarctic area, and in particular the plateau where the DOME-C base is located, for calibrating and validating data of satellite-borne microwave and optical radiometers. This is because the size, structure, spatial homogeneity and thermal stability of this area. With a view to the launching of the new low frequency space-borne sensor an experiment was carried out at Dome-C under support of ESA. In this paper, the preparatory activities, the experimental campaign in Antarctica and the results obtained are presented.
Measuring the accuracy of MARSS, An airborne microwave radiometer
2003
An airborne microwave radiometer has been thoroughly characterized by the Met Office, using a thermal- vacuum test facility and flight test data. Scan dependence due to mirror reflectivity considerations, as well as calibration target thermometry, target thermal gradients, radiometer noise, and radiometer stability are quantified. A resultant accuracy of approximately 1 K is achieved.
2013
The meeting series is intended for specialists working with theoretical, experimental or application aspects of active and passive microwave remote sensing of the Earth, Oceans, Ice and Atmosphere. Microwave Signatures 2013 provides an international forum for reporting and discussing recent achievements in microwave remote sensing instrumentation, methodology, and applications. The meeting has attracted professionals from around the world and consists of a serial sequence of oral and poster sessions. We would like to thank all members of the International Steering Committee for their work for a successful symposium. Thanks are also due to the organizers of the invited sessions: GNSS Reflectometry, L-band Active/Passive Land Surface Retrievals and SMAP, and Microwave Propagation in Vegetated and Snow Covered Soils. We also wish to thank sponsors of the Symposium. Three Commissions of the International Union of Radio Science (URSI) support the Symposium: Commission F (mode B, including travel support) and Commissions B and E (mode A, technical support). Other sponsors include the Institute of Electrical and Electronics Engineers (IEEE) Geoscience and Remote Sensing Society (GRSS) (technical support), Aalto University, and the City of Espoo. We sincerely hope that you enjoy the Symposium and your stay in Finland.
Identification of spaceborne microwave radiometer calibration sites for satellite missions
The first dedicated soil moisture satellite mission will be the European Space Agency's Soil Moisture and Ocean Salinity (SMOS) mission. This satellite, scheduled for launch in the second half of 2009, has a new type of satellite design that is based on the radio-astronomy technique of simulating a large antenna from a number of smaller ones placed some distance apart. Because of its unique design and the fact it is sensing in a currently unutilized frequency range makes it critical that on-orbit calibration targets be included in the calibration strategy. Consequently, targets such as the Antarctic, cold oceans, tropical forests and deserts are being considered. However, the large footprint size of passive microwave observations means that large scale homogeneous regions must be identified for calibration purposes. Moreover, these sites must also be either stable through time or the temporal variation easily described by models. In order to satisfy the calibration accuracy required by SMOS for soil moisture retrieval, such sites should be characterized with a brightness temperature uncertainty of less than 4K. A field experiment has been undertaken in November 2008 in the Australian Arid Zone to explore the suitability of three potential on-orbit calibration targets for SMOS. These sites were chosen for their assumed spatial homogeneity in terms of surface conditions (soil moisture and temperature, vegetation, soil type etc.), and consequently their expected microwave response. Each site covers an area of approximately 50km x 50km, being the approximate size of a satellite footprint. These sites include i) Wirringula Hills, a station to the north-east of Coober Pedy that is characterized by a dense cover of gibber; ii) Lake Eyre, characterized by a predominantly moist material under a layer of salt crust; and iii) Simpson Desert, characterized by sand dunes orientated in a north-south direction. The data collected during this field campaign consists of both airborne and ground-based measurements. The airborne data includes passive microwave emissions obtained with an L-band airborne radiometer, thermal infrared observations, and optical data. The ground data collection consisted of surface soil moisture measurements at targeted locations along sections of the high-resolution flight tracks, and station measurements of soil moisture and temperature profiles to a depth of 40cm. Additionally, there were soil core samples to a depth of 2m, surface characterization and surface roughness measurements. The airborne data were collected at two different resolutions, 1km and 50m. This paper presents the results from airborne observations made during this campaign, and discusses their significance in relation to the calibration of SMOS. Of the three study sites assessed, Wirringula Hills appears to be the most promising, having a spatial variability in brightness temperatures of less than 4K at H polarisation. In comparison, the Simpson Desert had a spatial variability of about 10K, and the moist region of Lake Eyre had a spatial variability of about 13K. Moreover, Lake Eyre was found to also have considerable spatial heterogeneity, making it unsuitable for calibration at the spatial resolution of SMOS.
EDIS
This new report from UF/IFAS researchers provides another set of observation data that can be used to develop better models for accurate prediction of weather and near-term climate. It describes the observations conducted during the MicroWEX-11, a season-long experiment incorporating active and passive microwave observations for bare soil, elephant grass, and sweet corn using a variety of sensors to understand land–atmosphere interactions and their effect on observed microwave signatures. These observations match that of satellite-based passive microwave radiometers and NASA’s recently launched Soil Moisture Active Passive (SMAP) mission. This 96-page report was written by Tara Bongiovanni, Pang-Wei Liu, Karthik Nagarajan, Daniel Preston, Patrick Rush, Tim H.M. van Emmerik, Robert Terwilleger, Alejandro Monsivais-Huertero, Jasmeet Judge, Susan Steele-Dunne, Roger De Roo, Ruzbeh Akbar, Ella Baar, Max Wallace, and Anthony England and published by the UF Department of Agricultural and ...