Atmosphere monitoring makes use of satellite measurements with very heterogeneous characteristics. In particular, the determination of vertical profiles of gases in the atmosphere can be performed using measurements acquired in different spectral bands and with different observation geometries. The most rigorous way to synthesize heterogeneous measurements of the same quantity in a single level 2 (L2) product is simultaneous retrieval. The main drawback of simultaneous retrieval is its complexity, due to the necessity to embed the forward models of different instruments into the same retrieval application. To overcome this shortcoming a novel data fusion method, referred to as Complete Data Fusion (CDF), has been recently developed as an efficient and adaptable alternative to simultaneous retrieval and thus, to merge a-posteriori a set of retrieved L2 products in a single one. In this work, the CDF method is applied to ozone profiles simulated in the thermal infrared and ultraviolet bands, according to the specifications of the Sentinel 4 (geostationary) and Sentinel 5 (low Earth orbit) missions of the Copernicus program. The simulated data have been produced in the context of the Advanced Ultraviolet Radiation and Ozone Retrieval for Applications project funded by the European Commission in the framework of the Horizon 2020 program. The use of synthetic data and the assumption of negligible systematic error in the simulated measurements allows studying the behavior of the CDF in ideal conditions. It is also worth noting that the CDF algorithm intrinsically provides a mechanism to account for different kinds of errors into the analysis. Furthermore, the use of synthetic data allows evaluating the performance of the algorithm also in terms of differences between the products of interest and a reference truth, represented by the atmospheric scenario used in the procedure to simulate the L2 products. In general, the CDF input is any number of L2 profiles retrieved with the optimal estimation technique and characterized by their a priori information, covariance matrix (CM) and averaging kernel (AK) matrix. The output of the CDF is a single product also characterized by an a priori, a CM and an AK matrix, which collect all the available information content. To account for the geo-temporal differences and different vertical grids of the fusing L2 profiles, a coincidence and an interpolation error have been added to the fused product error budget. In this work, we compare the quality of the fused products with that of the original retrievals in terms of bias, errors, information content and differences with respect to the reference truth. The benefit of fusing measurements with different geometries (geostationary and low Earth orbit) is also considered. In this study, we also show that the CDF method can be applied with different coincidence grid-box sizes, allowing for different compression factors of the L2 input data volume.
The Complete Data Fusion for Synergistic Exploitation of Geostationary and Low Earth Orbit Level 2 Atmospheric Products
SDel Bianco;
2019
Abstract
Atmosphere monitoring makes use of satellite measurements with very heterogeneous characteristics. In particular, the determination of vertical profiles of gases in the atmosphere can be performed using measurements acquired in different spectral bands and with different observation geometries. The most rigorous way to synthesize heterogeneous measurements of the same quantity in a single level 2 (L2) product is simultaneous retrieval. The main drawback of simultaneous retrieval is its complexity, due to the necessity to embed the forward models of different instruments into the same retrieval application. To overcome this shortcoming a novel data fusion method, referred to as Complete Data Fusion (CDF), has been recently developed as an efficient and adaptable alternative to simultaneous retrieval and thus, to merge a-posteriori a set of retrieved L2 products in a single one. In this work, the CDF method is applied to ozone profiles simulated in the thermal infrared and ultraviolet bands, according to the specifications of the Sentinel 4 (geostationary) and Sentinel 5 (low Earth orbit) missions of the Copernicus program. The simulated data have been produced in the context of the Advanced Ultraviolet Radiation and Ozone Retrieval for Applications project funded by the European Commission in the framework of the Horizon 2020 program. The use of synthetic data and the assumption of negligible systematic error in the simulated measurements allows studying the behavior of the CDF in ideal conditions. It is also worth noting that the CDF algorithm intrinsically provides a mechanism to account for different kinds of errors into the analysis. Furthermore, the use of synthetic data allows evaluating the performance of the algorithm also in terms of differences between the products of interest and a reference truth, represented by the atmospheric scenario used in the procedure to simulate the L2 products. In general, the CDF input is any number of L2 profiles retrieved with the optimal estimation technique and characterized by their a priori information, covariance matrix (CM) and averaging kernel (AK) matrix. The output of the CDF is a single product also characterized by an a priori, a CM and an AK matrix, which collect all the available information content. To account for the geo-temporal differences and different vertical grids of the fusing L2 profiles, a coincidence and an interpolation error have been added to the fused product error budget. In this work, we compare the quality of the fused products with that of the original retrievals in terms of bias, errors, information content and differences with respect to the reference truth. The benefit of fusing measurements with different geometries (geostationary and low Earth orbit) is also considered. In this study, we also show that the CDF method can be applied with different coincidence grid-box sizes, allowing for different compression factors of the L2 input data volume.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
