Forced trends and internal variability in climate change projections of extreme European windstorm frequency and severity

This is the author accepted manuscript.Data Availability: Code is available at the request of the author. CMIP6 data are publicly available through the Earth System Grid Federation. The cyclone tracking and compositing algorithm TRACK is available at the request of Kevin Hodges from https://gitlab.act.reading.ac.uk/track/track (Hodges, 1994, 1995, 1999).Climate change projections of European windstorm damages are highly uncertain because of different climate model responses and large internal variability. This study uses Generalized Linear Models and a weighted median estimation to optimally extract forced trends in a number of European windstorm metrics. Footprints of windstorms associated with extratropical cyclones are created for an ensemble of models from the 6th Coupled Model Intercomparison Project (CMIP6) across a full transient timeseries from 1980-2100. Trends are assessed over time, but also as a function of global mean surface temperature changes. Trends in aggregate severity are attributed to changes in storm average severity, frequency, and area impacted, with changes in area being the dominant driver of changes to average storm severity. Confidence in the findings is assessed, with high confidence of declines in frequency for southern and northern Europe, medium confidence of an increase in average windstorm severity for parts of northwestern Europe, and low confidence of any changes for eastern Europe. A 15-member ensemble of the MPI-ESM1-2-LR model is used to assess internal variability. Trends between individual members can vary significantly, however the uncertainty due to internal variability in the 15-member ensemble is generally only 50% of that in the multi-model ensemble of CMIP6 models for aggregate severity. With largest uncertainty coming from model differences, a large proportion of uncertainty in future windstorms is therefore potentially reducible with modelling advances.WTW Research NetworkMet Office Hadley Centre Climate Programme (HCCP

Meteorological and dust aerosol conditions over the western Saharan region observed at Fennec Supersite-2 during the intensive observation period in June 2011

The climate of the Sahara is relatively poorly observed and understood, leading to errors in forecast model simulations. We describe observations from the Fennec Supersite-2 (SS2) at Zouerate, Mauritania during the June 2011 Fennec Intensive Observation Period. These provide an improved basis for understanding and evaluating processes, models, and remote sensing. Conditions during June 2011 show a marked distinction between: (i) a "Maritime phase" during the early part of the month when the western sector of the Sahara experienced cool northwesterly maritime flow throughout the lower troposphere with shallow daytime boundary layers, very little dust uplift/transport or cloud cover. (ii) A subsequent "heat low" phase which coincided with a marked and rapid westward shift in the Saharan heat low towards its mid-summer climatological position and advection of a deep hot, dusty air layer from the central Sahara (the "Saharan residual layer"). This transition affected the entire western-central Sahara. Dust advected over SS2 was primarily from episodic low-level jet (LLJ)-generated emission in the northeasterly flow around surface troughs. Unlike Fennec SS1, SS2 does not often experience cold pools from moist convection and associated dust emissions. The diurnal evolution at SS2 is strongly influenced by the Atlantic inflow (AI), a northwesterly flow of shallow, cool and moist air propagating overnight from coastal West Africa to reach SS2 in the early hours. The AI cools and moistens the western Saharan and weakens the nocturnal LLJ, limiting its dust-raising potential. We quantify the ventilation and moistening of the western flank of the Sahara by (i) the large-scale flow and (ii) the regular nocturnal AI and LLJ mesoscale processes. Key Points First detailed observations from western Sahara sector Intraseasonal shift in Saharan heat low drives meteorological/aerosol conditions Atlantic Inflow interaction with low level jet

Scaling-up productivity (NPP) using light or water use efficiencies (LUE, WUE) from a two-layer tropical plantation

International audienceNet primary productivity (NPP) is a key driver of ecosystem C balance. ScalingNPP up to larger areas requires indirectmethods: (a) for examble epsilon models based on light use efficiency (LUE = NPP/ APAR, where APAR is the absorbed photosynthetically active radiation by green elements of canopy, or else models based on water-use-efficiency (WUE = NPP/E, where E = evapo-transpiration); (b) remote sensing tools to estimate the fraction ofAPAR(fAPAR) from vegetation indexes, or to estimate E. However, LUE and WUE are suspected to vary in space (edaphoclimatic conditions, planting density) and time (seasonality, age), which needs to be documented before scaling up. Moreover, the application of this scaling approach to agroforestry systems with a stratified canopy may be difficult, since each layer contributes to the overall ecosystem light- and water-use efficiencies. The seasonal and inter-annual variabilities of LUE and WUE was assessed in a very simple bi-layer tropical coconut grove displaying minimum climatic and LAI variations, distinguishing the upper layer of coconuts, the herbaceous under-storey and the whole stand (subscripts C, H and S, respectively). We monitored NPP biometrically during 3 years above and below ground, together with microclimate and ES above the canopy (eddy-covariance), transpiration (TC) by sapflow, and fAPARC by LAI-2000 combined with canopy light absorption models. The partitioning of APAR, NPP and E was very close to the rule-of-thumb of canopy coverage by upper-layer (75%). Also the mean annual value of LUES (1.7 gDM MJPARi -1 ) or mean WUES (3.7 gDM kg_1 H2O) were mainly driven by the upper-layer of coconuts. However, the under-storey experienced around twice as much seasonal variations of NPP, E,LUE andWUE than the upper-storey. Given that NPPS varied by only 23% over the year, the high seasonal variations of WUES (240%) and LUES (250%) were mostly driven by the variations of APARS (230%) and were adjusted successfully using climate, age and density data, as a first step to estimate NPP on larger scales using climate, GIS and remotesensing

Calibration and Monitoring of the Pierre Auger Observatory

Reports on the atmospheric monitoring, calibration, and other operating systems of the Pierre Auger Observatory. Contributions to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009

Studies of Cosmic Ray Composition and Air Shower Structure with the Pierre Auger Observatory

Submissions to the 31st International Cosmic Ray Conference, Lodz, Poland (July 2009)International audienceStudies of the composition of the highest energy cosmic rays with the Pierre Auger Observatory, including examination of hadronic physics effects on the structure of extensive air showers. Submissions to the 31st ICRC, Lodz, Poland (July 2009)