Within the framework of the Helmholtz Association Strategy Project ''GPS Atmosphere Sounding'' (GASP), an operational monitoring of integrated water vapor was established using 170 GPS sites in Germany and neighboring countries. The product, which can be obtained within 12-15 minutes of computer time on a single Linux PC, is generated each hour with a 30-minute time resolution and an accuracy of G1-2 mm in the precipitable water vapor. The GPS estimates are regularly validated using collocated instruments and the local model (LM) of the German Weather Service (DWD). First experiments for numerical weather predictions are performed at DWD and showed 2% improvement for the relative humidity in a 12-hour forecast, whilst the impact on the precipitation forecast over 24 hours is mixed up to now.

To study why, where, and when deep convection

With the increase of spatial resolution of weather forecast models to order O(1 km), the need for adequate observations for model validation becomes evident. Therefore, we designed and constructed the ''KITcube'', a mobile observation platform for convection studies of processes on the meso-c scale. The KITcube consists of in-situ and remote sensing systems which allow measuring the energy balance components of the Earth's surface at different sites; the mean atmospheric conditions by radiosondes, GPS station, and a microwave radiometer; the turbulent characteristics by a sodar and wind lidars; and cloud and precipitation properties by use of a cloud radar, a micro rain radar, disdrometers, rain gauges, and an X-band rain radar. The KITcube was deployed fully for the first time on the French island of Corsica during the HyMeX (Hydrological cycle in the Mediterranean eXperiment) field campaign in 2012. In this article, the components of KITcube and its implementation on the island are described. Moreover, results from one of the HyMeX intensive observation periods are presented to show the capabilities of KITcube.

Soil moisture is a geophysical key observable for predicting floods and droughts, modeling weather and climate and optimizing agricultural management. Currently available in situ observations are limited to small sampling volumes and restricted number of sites, whereas measurements from satellites lack spatial resolution. Global navigation satellite system (GNSS) receivers can be used to estimate soil moisture time series at an intermediate scale of about 1000 m 2 . In this study, GNSS signal-to-noise ratio (SNR) data at the station Sutherland, South Africa, are used to estimate soil moisture variations during 2008-2014. The results capture the wetting and drying cycles in response to rainfall. The GNSS Volumetric Water Content (VWC) is highly correlated (r 2 = 0.8) with in situ observations by time-domain reflectometry sensors and is accurate to 0.05 m 3 /m 3 . The soil moisture estimates derived from the SNR of the L1 and L2P signals compared to the L2C show small differences with a RMSE of 0.03 m 3 /m 3 . A reduction in the SNR sampling rate from 1 to 30 s has very little impact on the accuracy of the soil moisture estimates (RMSE of the VWC difference 1-30 s is 0.01 m 3 /m 3 ). The results show that the existing data of the global tracking network with continuous observations of the L1 and L2P signals with a 30-s sampling rate over the last two decades can provide valuable complementary soil moisture observations worldwide.

The Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences (GFZ) is operating a worldwide Global Navigation Satellite Systems (GNSS) station network since many years. With recent developments in receiver technology and new upcoming navigation satellite systems like Galileo an upgrade of our stations was needed to track all GNSS. We will present the current status and setup of our station network and the plan for future upgrades. All modernized stations are presently contributing to the Multi-GNSS EXperiment (MGEX) of the International GNSS Service (IGS) as well as to the COoperative Network of GNSS Observations (CONGO). Selected results from a combined GPS/Galileo data processing will be shown. The used data were taken mainly from the public available MGEX network whereas the focus of analysis lies on precise orbit and clock determination of Galileo In-Orbit-Validation (IOV) satellites. Quality assessments are given which are based on orbit overlap statistics, clock stabilities as well as comparisons with external solutions. Additionally an independent validation of the orbits is derived through Satellite Laser Ranging (SLR) measurements. Furthermore some initial results of BeiDou data processing are shown which were derived with an experimental set of MGEX data.