Bayesian analysis of the species-specific lengthening of the growing season in two European countries and the influence of an insect pest

A recent lengthening of the growing season in mid and higher latitudes of the northern hemisphere is reported as a clear indicator for climate change impacts. Using data from Germany (1951–2003) and Slovenia (1961–2004), we study whether changes in the start, end, and length of the growing season differ among four deciduous broad-leaved tree species and countries, how the changes are related to temperature changes, and what might be the confounding effects of an insect attack. The functional behaviour of the phenological and climatological time series and their trends are not analysed by linear regression, but by a new Bayesian approach taking into account different models for the functional description (one change-point, linear, constant models). We find advanced leaf unfolding in both countries with the same species order (oak > horse chestnut, beech, and birch). However, this advance is non linear over time and more apparent in Germany with clear change-points in the late 1970s, followed by marked advances (on average 3.67 days decade−1 in the 2000s). In Slovenia, we find a more gradual advance of onset dates (on average 0.8 days decade−1 in the 2000s). Leaf colouring of birch, beech, and oak has been slightly delayed in the last 3 decades, especially in Germany, however with no clear functional behaviour. Abrupt changes in leaf colouring dates of horse chestnut with recent advancing onset dates can be linked across countries to damage by a newly emerging pest, the horse chestnut leaf-miner (Cameraria ohridella). The lengthening of the growing season, more distinct in Germany than in Slovenia (on average 4.2 and 1.0 days decade−1 in the 2000s, respectively), exhibits the same species order in both countries (oak > birch > beech). Damage by horse chestnut leaf-miner leads to reduced lengthening (Germany) and drastic shortening (Slovenia) of the horse chestnut growing season (-12 days decade−1 in the 2000s). Advanced spring leaf unfolding and lengthening of the growing season of oak, beech and birch are highly significantly related to increasing March temperatures in both countries. Only beech and oak leaf unfolding in Germany, which is generally observed later in the year than that of the other two species, is more closely correlated with April temperatures, which comparably exhibit marked change-points at the end of the 1970s

Priority questions in multidisciplinary drought research

Addressing timely and relevant questions across a multitude of spatio-temporal scales, state-of-the-art interdisciplinary drought research will likely increase in importance under projected climate change. Given the complexity of the various direct and indirect causes and consequences of a drier world, scientific tasks need to be coordinated efficiently. Drought-related research endeavors ranging from individual projects to global initiatives therefore require prioritization. Here, we present 60 priority questions for optimizing future drought research. This topical catalogue reflects the experience of 65 scholars from 21 countries and almost 20 fields of research in both natural sciences and the humanities. The set of drought-related questions primarily covers drought monitoring, impacts, forecasting, climatology, adaptation, as well as planning and policy. The questions highlight the increasingly important role of remote sensing techniques in drought monitoring, importance of drought forecasting and understanding the relationships between drought parameters and drought impacts, but also challenges of drought adaptation and preparedness policies

Ionospheric scitillation activity measured in the African sector

Abstract A sample of ionospheric scintillation activity measured in the African sector (Douala, magnetic latitude 5.36 • N) is analysed, using measurements provided by a dual frequency GPS Ionospheric Scintillation and TEC monitor (GSV4004). The measurements consist of classical ionospheric scintillation indices evaluated at L1 and Total Electron Content (TEC) computed over 1 minute intervals on both L1 and L2. Measurements referring to quiet and disturbed conditions occurring between 4 November 2004 and 15 November 2004 were considered in this analysis. An overview of the scintillation activity in that event is presented (also in comparison with simultaneous measurements collected in the Brazilian sector). The importance of this type of analyses relies on the need to understand the potential threats to GNSS based applications

The SLR observations to GNSS satellites: Preliminary results and open questions

In the present study, we show the results of the multi-year processing of SLR observations to GNSS satellites (both for GPS and GLONASS satellites), using the Bernese GNSS Software. The aim of the study is to investigate the associated SLR range residuals, defined as the differences between: (a) the observed SLR ranges and (b) the computed spatial distances between the ground stations and the GNSS (precise) orbits, respectively. The residuals are estimated on daily basis, taking into account inter alia, the Non Tidal Atmospheric Loading (NTAL) and the Atmospheric Ocean De-aliasing (AOD) effect. The results indicate different biases for the GPS and GLONASS satellites and show remarkable variability among the ground stations

Validation of the EGSIEM-REPRO GNSS Orbitsand Satellite Clock Corrections.

In the framework of the European Gravity Service for Improved Emergency Management(EGSIEM) project, consistent sets of state-of-the-art reprocessed Global Navigation Satellite System(GNSS) orbits and satellite clock corrections have been generated. The reprocessing campaignincludes data starting in 1994 and follows the Center for Orbit Determination in Europe (CODE)processing strategy, in particular exploiting the extended version of the empirical CODE Orbit Model(ECOM). Satellite orbits are provided for Global Positioning System (GPS) satellites since 1994 and forGlobalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS) since 2002. In addition, a consistentset of GPS satellite clock corrections with 30 s sampling has been generated from 2000 and with 5 ssampling from 2003 onwards. For the first time in a reprocessing scheme, GLONASS satellite clockcorrections with 30 s sampling from 2008 and 5 s from 2010 onwards were also generated. The benefitwith respect to earlier reprocessing series is demonstrated in terms of polar motion coordinates.GNSS satellite clock corrections are validated in terms of completeness, Allan deviation, and precisepoint positioning (PPP) using terrestrial stations. In addition, the products herein were validated withGravity Recovery and Climate Experiment (GRACE) precise orbit determination (POD) and SatelliteLaser Ranging (SLR). The dataset is publicly available