The study of warm molecular gas in the inner regions of protoplanetary disks is of key importance for the study of planet formation and especially for the transport of H 2 O and organic molecules to the surfaces of rocky planets/satellites. Recent Spitzer observations have shown that the mid-infrared spectra of protoplanetary disks are covered in emission lines due to water and other molecules. Here, we present a non-LTE 2D radiative transfer model of water lines in the 10-36 µm range that can be used to constrain the abundance structure of water vapor, given an observed spectrum, and show that an assumption of local thermodynamic equilibrium (LTE) does not accurately estimate the physical conditions of the water vapor emission zones, including temperatures and abundance structures. By applying the model to published Spitzer spectra we find that: 1) most water lines are subthermally excited, 2) the gas-to-dust ratio must be as much as one to two orders of magnitude higher than the canonical interstellar medium ratio of 100-200, and 3) the gas temperature must be significantly higher than the dust temperature, in agreement with detailed heating/cooling models, and 4) the water vapor abundance in the disk surface must be significantly truncated beyond ∼ 1 AU. A low efficiency of water formation below ∼ 300 K may naturally result in a lower water abundance beyond a certain radius. However, we find that chemistry, although not necessarily ruled out, may not be sufficient to produce a sharp abundance drop of many orders of magnitude and speculate that the depletion may also be caused by vertical turbulent diffusion of water vapor from the superheated surface to regions below the snow line, where the water can freeze out and be transported to the midplane as part of the general dust settling. Such a vertical cold finger effect is likely to be efficient due to the lack of a replenishment mechanism of large, water-ice coated dust grains to the disk surface.

Abstract. In this paper we present a performance analysis of the European lightning location system EUCLID for cloud-to ground flashes/strokes in terms of location accuracy (LA), detection efficiency (DE) and peak current estimation. The performance analysis is based on ground truth data from direct lightning current measurements at the Gaisberg Tower (GBT) and data from E-field and video recordings. The E-field and video recordings were collected in three different regions in Europe, namely in Austria, Belgium and France. The analysis shows a significant improvement of the LA of the EUCLID network over the past 7 years. Currently, the median LA is in the range of 100 m in the center of the network and better than 500 m within the majority of the network. The observed DE in Austria and Belgium is similar, yet a slightly lower DE is determined in a particular region in France, due to malfunctioning of a relevant lightning location sensor during the time of observation. The overall accuracy of the lightning location system (LLS) peak current estimation for subsequent strokes is reasonable keeping in mind that the LLS-estimated peak currents are determined from the radiated electromagnetic fields, assuming a constant return stroke speed.The results presented in this paper can be used to estimate the performance of the EUCLID network related to cloud-toground flashes/strokes for regions with similar sensor baselines and sensor technology.

Abstract.We consider the excitation of water in the Photon Dominated Region (PDR) S140. With the use of a threedimensional escape probability method we compute the level populations of ortho-and para-H 2 O up to ∼350 K (i.e., 8 levels), as well as line intensities for various transitions. Homogeneous and inhomogeneous models are presented with densities of 10 4 -10 5 cm −3 and the differences between the resulting intensities are displayed. Density, temperature, and abundance distributions inside the cloud are computed with the use of a self-consistent physi-chemical (in)homogeneous model in order to reproduce the line intensities observed with SWAS, and to make predictions for various lines that HIFI will probe in the future. Line intensities vary from ∼10 −13 erg cm −2 s −1 sr −1 to a few times 10 −6 erg cm −2 s −1 sr −1 . We can reproduce the intensity for the 1 10 → 1 01 line observed by the SWAS satellite. It is found that the 2 12 → 1 01 line is the strongest, whereas the 3 12 → 2 21 line is the weakest, in all the models. It is found that the 1 10 → 1 01 line probes the total column, while higher excitation lines probe the higher density gas (e.g., clumps).

Abstract. Cloud-to-ground (CG) lightning data from the European Cooperation for Lightning Detection (EUCLID) network over the period 2006-2014 are explored. Mean CG flash densities vary over the European continent, with the highest density of about 6 km −2 yr −1 found at the intersection of the borders between Austria, Italy and Slovenia. The majority of lightning activity takes place between May and September, accounting for 85 % of the total observed CG activity. Furthermore, the thunderstorm season reaches its highest activity in July, while the diurnal cycle peaks around 15:00 UTC. A difference between CG flashes over land and sea becomes apparent when looking at the peak current estimates. It is found that flashes with higher peak currents occur in greater proportion over sea than over land.