Converting Between SMOS and SMAP Level-1Brightness Temperature Observations Over Non frozen Land
Abstract : The Soil Moisture and Ocean Salinity (SMOS) andSoil Moisture Active Passive (SMAP) missions provide Level-1brightness temperature (Tb) observations that are used for global soil moisture estimation.The nature of these Tb data differs: the SMOS Tb observations contain atmospheric and select reflected extraterrestrial (“Sky”) radiation, whereas the SMAP Tb data are corrected for these contributions, using auxiliary near-surface information. Furthermore, the SMOS Tb observations are multi angular, whereas the SMAP Tb is measured at 40?incidenceangle only. This letter discusses how SMOS Tb, SMAP Tb, and radiative transfer modeling components can be aligned in order to enable a seamless exchange of SMOS and SMAP Tb data in soil moisture retrieval and assimilation systems. The aggregated contribution of the atmospheric and reflected Sky radiation is, on average, about 1 K for horizontally polarized Tb and 0.5 K for vertically polarized Tb at 40?incidence angle, but local and short-term values regularly exceed 5 K . Index Terms—Atmosphere, brightn
? we provide a discussion of how atmospheric and Sky contributions can be simulated in Tb forward modeling, removed from (multi angular) SMOS L1 Tb data, or added to the SMAP L1B Tb data, if so desired.
? SATELLITE-based L-band (1.4 GHz) microwave remote sensing is used for global soil moisture estimation by the Soil Moisture Ocean Salinity (SMOS) mission and the Soil Moisture Active Passive (SMAP) mission.
DISADVANTAGE OF EXISTING SYSTEM:
? The radar instrument onboard SMAP satellite stopped transmitting data on Jul 7, 2015 due to a problem in the radar’s high-power amplifier .a
? Currently, soil moisture products are retrieved from SMAP TB radiometer data using the baseline Single Channel Algorithm (SCA) V-pol.
? This is not unexpected due to uncertainties in the SMOS datasets caused by the high vegetation attenuation effects in these regions, which is a major problem for most of the remotely sensed soil moisture retrievals
? In this paper, a new method is proposed for retrieving thin SIT by establishing a direct empirical relationship between SIT acquired through various ‘airborne sea-ice thickness’ (hereinafter: ASIT) campaigns throughout the Arctic .
? during 2011–15 and SMOS PD at 50° incidence angle. This is the first empirical study that exclusively uses only ASIT data to train the algorithm.
? The latest version of SMOS Level 1B TB data in the Arctic has been used at 25 km SMOS grid during cold and dry months (October–April)
? To accurately interpret these L-band measurements in soil moisture retrieval algorithms or data assimilation schemes.
? It is important to understand how the Earth surface, atmosphere, and extrater restrial sources are contributing to the observed brightness temperature (Tb).
? Converting Between SMOS and SMAP Level-1 Brightness Temperature Observations Over Non frozen Land.
? The Moon contribution is also corrected for in the SMAP L1B product, but this correction has be enomitted for the SMOS L1 data over land, because of its negligible impact on soil moisture estimation.
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