Microwave Radiometer And Radar Measurements In The SAAMEX Campaign (original) (raw)
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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.
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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.
IEEE Transactions on Geoscience and Remote Sensing, 2003
We discuss the performances of a set of four microwave water vapor radiometers operating in the 20-30-GHz band during a field experiment, with an emphasis on calibration and achievable accuracy. The field experiment was conducted at the Department of Energy's Atmospheric Radiation Measurement Program's field site in north central Oklahoma, and was focused on clear-sky water vapor measurements by both radiometers and radiosondes. A comparison between two published radiometric tip curve calibration procedures is presented, and these procedures are applied to measurements from two nearly identical instruments placed a few meters apart. Using the instantaneous tip cal method of the Environmental Technology Laboratory, the brightness temperature measurements for the two identical instruments differed by less than 0.2 K over a 24-h period. Results from reference load cryogenic tests and brightness temperature cross comparisons have shown differences within 0.7 K. In addition, we compare radiometric measurements with calculations of brightness temperature based on the Rosenkranz absorption model and radiosonde observations. During the experiment, both Vaisala-type RS80 and RS90 humidity sensors were used. Our comparisons demonstrate the improvements achieved by the new Vaisala RS90 sensors in atmospheric humidity profiling, which reduce or eliminate the "dry bias" problem.