Abstract. This paper presents a first statistical validation of tropospheric ozone products derived from measurements of the IASI satellite instrument. Since the end of 2006, IASI (Infrared Atmospheric Sounding Interferometer) aboard the polar orbiter Metop-A measures infrared spectra of the Earth's atmosphere in nadir geometry. This validation covers the northern mid-latitudes and the period from July 2007 to August 2008. Retrieval results from four different sources are presented: three are from scientific products (LATMOS, LISA, LPMAA) and the fourth one is the pre-operational product distributed by EUMETSAT (version Correspondence to: M. Eremenko (maxim.eremenko@lisa.univ-paris12.fr) 4.2). The different products are derived from different algorithms with different approaches. The difference and their implications for the retrieved products are discussed. In order to evaluate the quality and the performance of each product, comparisons with the vertical ozone concentration profiles measured by balloon sondes are performed and lead to estimates of the systematic and random errors in the IASI ozone products (profiles and partial columns). A first comparison is performed on the given profiles; a second comparison takes into account the altitude dependent sensitivity of the retrievals. Tropospheric columnar amounts are compared to the sonde for a lower tropospheric column (surface to about 6 km) and a "total" tropospheric column (surface to about 11 km). On average both tropospheric columns have small biases for the scientific products, less than 2 DobsonPublished by Copernicus Publications on behalf of the European Geosciences Union. C. Keim et al.: IASI tropospheric ozone validationUnits (DU) for the lower troposphere and less than 1 DU for the total troposphere. The comparison of the still preoperational EUMETSAT columns shows higher mean differences of about 5 DU.

A b s t r a c t .Magnetic clouds are associated with many Coronal Mass Ejections. Many CMEs involve active regions. In this work we focus on the relationship between twelve magnetic clouds and their associated active regions. We use a cylindrically symmetric constant-a force-free model to derive field line twist, total current, and total magnetic flux from in situ observations of magnetic clouds. We compare these properties with those of the associated solar active regions, which we infer from solar vector magnetograms.Our comparison of fluxes and currents reveals: (1) the total (unsigned) flux ratios $MC/$AR tend to be of order unity; (2) the total flux ratios tend to be orders of magnitude larger than the total (unsigned) current ratios IMC/IAR', and (3) there is a statistically significant proportionality between them. Our key findings in comparing total twists aL, where L is the axial dimension of the system, are: (1) the values of (OIL)MC a r e typically an order of magnitude greater than those of (OL)AR', and (2) there is no systematic sign or amplitude relationship between them. These findings compel us to believe that magnetic clouds associated with active region eruptions are formed by magnetic reconnection between these regions and their larger-scale surroundings, rather than pre-existing structures in the corona or chromosphere.132

No abstract

No abstract

Abstract. This paper presents a first statistical validation of tropospheric ozone products derived from measurements of the satellite instrument IASI. Since end of 2006, IASI (Infrared Atmospheric Sounding Interferometer) aboard the polar orbiter Metop-A measures infrared spectra of the Earth's atmosphere in nadir geometry. This validation covers the northern mid-latitudes and the period from July 2007 to August 2008. The comparison of the ozone products with the vertical ozone concentration profiles from balloon sondes leads to estimates of the systematic and random errors in the IASI ozone products. The intercomparison of the retrieval results from four different sources (including the EUMETSAT ozone products) shows systematic differences due to the used methods and algorithms. On average the tropospheric columns have a small bias of less than 2 Dobson Units (DU) when compared to the sonde measured columns. The comparison of the still pre-operational EUMETSAT columns shows higher mean differences of about 5 DU.