Gome U7 Global Rom Download

Abstract. Globally mapped terrestrial chlorophyll fluorescence retrievals are of high interest because they can provide information on the functional status of vegetation including light-use efficiency and global primary productivity that can be used for global carbon cycle modeling and agricultural applications. Previous satellite retrievals of fluorescence have relied solely upon the filling-in of solar Fraunhofer lines that are not significantly affected by atmospheric absorption. Although these measurements provide near-global coverage on a monthly basis, they suffer from relatively low precision and sparse spatial sampling. Here, we describe a new methodology to retrieve global far-red fluorescence information; we use hyperspectral data with a simplified radiative transfer model to disentangle the spectral signatures of three basic components: atmospheric absorption, surface reflectance, and fluorescence radiance. An empirically based principal component analysis approach is employed, primarily using cloudy data over ocean, to model and solve for the atmospheric absorption. Through detailed simulations, we demonstrate the feasibility of the approach and show that moderate-spectral-resolution measurements with a relatively high signal-to-noise ratio can be used to retrieve far-red fluorescence information with good precision and accuracy. The method is then applied to data from the Global Ozone Monitoring Instrument 2 (GOME-2). The GOME-2 fluorescence retrievals display similar spatial structure as compared with those from a simpler technique applied to the Greenhouse gases Observing SATellite (GOSAT). GOME-2 enables global mapping of far-red fluorescence with higher precision over smaller spatial and temporal scales than is possible with GOSAT. Near-global coverage is provided within a few days. We are able to show clearly for the first time physically plausible variations in fluorescence over the course of a single month at a spatial resolution of 0.5 0.5. We also show some significant differences between fluorescence and coincident normalized difference vegetation indices (NDVI) retrievals.

Operational data products of GOME as generated by DLR-DFD, the German Data Processing and Archiving Facility (D-PAF) for GOME, comprise absolute radiometrically calibrated earthshine radiance and solar irradiance spectra (level 1 products) and global distributions of total column amounts of ozone and NO2 (level 2 products), which are derived using the DOAS approach (Differential Optical Absorption Spectroscopy). (Under certain conditions and some restrictions, the operational data products are publically available from the European Space Agency via the ERS Helpdesk.)

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Dramatic changes in atmospheric composition causing a severe depletion of ozone during the Antarctic spring first detected by Farman et al. (1985) and their global impact (Houghton et al. 1991) established the need for global measurements of trace atmospheric constituents (ESA 1991). The SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) instrument proposal (Burrows et al. 1988a; Bovensmann et al. 1999) was prepared in response to an ESA (European Space Agency) call for instrumentation to fly on its polar orbiting platform, now known as ENVISAT-1 (First European Environmental Satellite), which is due for launch in 2000. In late 1988 it was recognized that an instrument for global monitoring of ozone and other trace gases should be added as the only new instrument to the Second European Remote Sensing Satellite (ERS-2) mission in order to satisfy the need for global trace constituent measurements as soon as possible prior to the launch of ENVISAT-1. In response to an ESA announcement of opportunity, SCIAMACHY scientists proposed a small-scale version of SCIAMACHY under the name SCIAmini (Burrows et al. 1988b), which after some modification was renamed the Global Ozone Monitoring Experiment (GOME) and approved by the ESA council to be launched aboard ERS-2 in June 1990 (ESA 1993).

Trace gas retrieval: global measurements of total columns of O3, NO2, BrO, H2O, O4, O2, and NO3;OClO and ClO (under ozone hole conditions), NO (above 40 km), SO2 (under polluted conditions and following volcanic eruptions), H2CO (under polluted conditions), and ozone vertical profiles.

Due to the large dynamic range of the signal below 307 nm as a result of the increasing ozone absorption in the Huggins band, the channel 1 diode array is divided into two virtual bands, 1A and 1B, which can be programmed to different integration times in order to optimize the signal-to-noise ratio. For channel 1A an integration time (IT) of 12 s was selected, while channel 1B has an IT of 1.5 s as do the remaining channels. Initially the integration time for channels 1B to 4 was limited to 0.375 s to avoid saturation effects. After a successful uplink of a co-adding software patch in March 1996, GOME achieved its intended 1.5-s integration time, which is required to obtain global coverage.

The first studies of GOME BrO columns were mainly concerned with stratospheric BrO (Eisinger et al. 1996b, Hegels et al. 1998) and showed the potential of global BrO detection by the instrument. Wagner and Platt (1998) found the first evidence of tropospheric BrO signals in the GOME measurements. They analyzed a large plume of BrO over Antarctica, and by comparing the retrieved amounts of BrO with the total Bry content of the stratosphere they concluded that for this cloud-free situation the BrO had to be located in the troposphere. The study of Richter et al. (1998) has focused on the Northern Hemisphere and showed that enhanced tropospheric BrO columns were common events in Arctic regions during spring and early summer 1997.

Ground-based measurements of tropospheric BrO in remote regions are restricted to a few stations. In contrast the GOME measurements offer a global view and an example is given in Fig. 11, where total BrO columns are shown for three days in April 1997. In the Hudson Bay area and parts of the Canadian Arctic enhanced columns indicate a large tropospheric BrO cloud. In this region enhanced BrO values were detected on many days from February to May 1997, which indicates a large and continuous local source of BrO. Enhanced BrO values are also seen along the coastlines of the Arctic Sea and toward the pole, in agreement with ground-based measurements in these areas. These results further confirm the model of bromine release from sea salt via activation on pack ice. After June no further BrO events were detected by GOME in the Northern Hemisphere, showing that bromine activation in polar regions is in fact restricted to the spring season, when ice is present.

Sulfur dioxide released from large volcanic eruptions can be injected directly into the lower stratosphere, where it is oxidized to sulfuric acid and combines with water to form stratospheric sulfate aerosols. Heterogeneous reactions on aerosols can affect global ozone chemistry (Jackman et al. 1996) and alter the radiation budget of regional and global climate due to aerosol scattering and absorption. The most prominent volcanic eruptions with global impact within the last two decades were the El Chchon (1982) and Mount Pinatubo (1991) events.

Each scan back and forth across the satellite track takes just six seconds and with a scan-width of 1920 km, global coverage can be achieved within one day. The advanced GOME-2 observes four times smaller ground pixels (80 km x 40 km) than GOME on ERS-2 and has better polarisation and the calibration processes have been improved.

The Global Ozone Monitoring Experiment (GOME) was an instrument aboard ERS-2. The main scientific objective of the GOME mission is to measure the global distribution of ozone and several trace gases which play an important role in the ozone chemistry of the Earth's stratosphere and troposphere, for example, NO2, BrO, OClO, and SO2.

Formaldehyde (H2CO) tropospheric columns have been retrieved since 2007 from backscattered UV radiance measurements performed by the GOME-2 instrument on the EUMETSAT METOP-A platform. This data set extends the successful time-series of global H2CO observations established with GOME/ ERS-2 (1996-2003), SCIAMACHY/ ENVISAT (2003-2012), and OMI on the NASA AURA platform (2005-now). In this work, we perform an intercomparison of the H2CO tropospheric columns retrieved from GOME-2 and OMI between 2007 and 2010, respectively at BIRA-IASB and at Harvard SAO. We first compare the global formaldehyde data products that are provided by each retrieval group. We then investigate each step of the retrieval procedure: the slant column fitting, the reference sector correction and the air mass factor calculation. New air mass factors are computed for OMI using external parameters consistent with those used for GOME-2. By doing so, the impacts of the different a priori profiles and aerosol corrections are quantified. The remaining differences are evaluated in view of the expected diurnal variations of the formaldehyde concentrations, based on ground-based measurements performed in the Beijing area.

A novel approach to retrieving total ozone columns from the ERS2 GOME (Global Ozone Monitoring Experiment) spectral data has been developed. With selected GOME wavelength regions, from clear and cloudy pixels alike plus orbital and instrument data as input, a feed-forward neural network was trained to determine total ozone in a one-step inverse retrieval procedure. To achieve this training, ground-based total ozone measurements from the World Ozone and Ultraviolet Data Center (WOUDC) for the years 1996-2000, supplemented with Dobson-corrected Total Ozone Mapping Spectrometer (TOMS) data to provide global coverage, were collocated with GOME ground pixels into a training data set. Validation of the neural-network-retrieved ozone values relative to independent ground stations yielded a rms error of better than 11 Dobson units. Comparisons performed on the basis of operationally available TOMS and GOME level-3 maps exhibit good agreement in general, with a latitude-dependent offset. 2351a5e196