Abstract. Global satellite measurements of solar-induced fluorescence (SIF) from chlorophyll over land and ocean have proven useful for a number of different applications related to physiology, phenology, and productivity of plants and phytoplankton. Terrestrial chlorophyll fluorescence is emitted throughout the red and far-red spectrum, producing two broad peaks near 683 and 736 nm. From ocean surfaces, phytoplankton fluorescence emissions are entirely from the red region. Studies using satellite-derived SIF over land have focused almost exclusively on measurements in the far- red, since those are the most easily obtained with existing instrumentation. Here, we examine new ways to use existing hyper-spectral satellite data sets to retrieve red SIF over both land and ocean. Our approach offers noise reductions as compared with previously published solar line filling retrievals by making use of the oxygen (O2) γ-band that is not affected by SIF. The O2 γ-band in conjunction with solar Fraunhofer lines help to anchor the O2 B-band that provides additional information on red SIF. Biases due to instrumental artifacts that vary in time, space, and with instrument, must be addressed in order to obtain reasonable results. The satellite instruments that we use were designed to make atmospheric trace- gas measurements and are therefore not optimal for observing SIF; they have coarse spatial resolution and only moderate spectral resolution (∼0.5 nm). Nevertheless, these instruments offer a unique opportunity to compare red and far-red terrestrial SIF at regional spatial scales. Our eight year record of red SIF observations over land with the Global Ozone Monitoring Instrument 2 (GOME-2) allows for the first time reliable global mapping of monthly anomalies. These anomalies are shown to have similar spatio-temporal structure as those in the far-red, particularly for drought-prone regions. There is a somewhat larger percentage response in the red as compared with the far-red for these areas that are sensitive to soil moisture, although the differences are within the specified uncertainties that are dominated by systematic errors. We also demonstrate that high quality ocean fluorescence line height retrievals can be achieved with GOME-2 and similar instruments by utilizing the full complement of radiance measurements that span the red SIF emission feature.
On impulse excitation of the global poloidal modes in the magnetosphere
