Impact of Multisatellite Altimeter Data Assimilation on Wave Analysis and Forecast

Satellite altimetry has become an important discipline in the development of sea-state forecasting or more generally in operational oceanography. Météo-France Marine and Oceanography Division is much involved in altimetry, in which it is also one of the main operational customers. Sea-state forecasts are produced every day with the help of numerical models assimilating Fast Delivery Product altimeter data from ESA ERS-2 satellite, available in real-time (3–5 h). These forecasts are transmitted to seamen as part of safety mission of persons and properties, or specific assistance for particular operations. With the launch of ENVISAT (from ESA, launched on 1 March 2002, to take over the ERS mission) and JASON-1 (from CNES/NASA, launched on 7 December 2001, successor of TOPEX/Poseidon), we have an unprecedented opportunity of improved coverage with the availability in quasi-real-time of data from several altimeters. The objective of this study is to evaluate the impact of using multisources of altimeter data in real-time, to improve wave model analyses and forecasts, at global scale. Since July 2003, Météo-France injects the wind/wave JASON-1 Operational Sensor Data Record on the WMO Global Transmitting System, making them available in near real-time to the international meteorological community. Similarly, fast delivery altimeter data of ENVISAT will improve coverage and contribute to the constant progress of marine meteorology. For this purpose, significant wave height time series were generated using the Wave Model WAM and the assimilation of altimeter wave heights from two satellites ERS-2 and JASON-1. The results were then compared to Geosat Follow-On (GFO, U.S. Navy Satellite) and moored buoy wave data. It is shown that the impact of data assimilation, when two (ERS-2 and JASON-1) or three (ERS-2 with JASON-1 and GFO) sources of data are used instead of one (ERS-2), in term of significant wave height, is larger in wave model analyses but smaller in wave model forecasts. However, there is no improvement in terms of wave periods, both in the analysis and forecast periods.     

Vertical Profile of Night-Time Stratospheric OClO

The first night-time observation of the vertical profile of OClO wasperformed by the AMON balloon-borne spectrometer during the SESAME arcticcampaign, launched from Kiruna in northern Scandinavia. The flight, which tookplace inside the polar vortex on February 10, 1995, reveals mixing ratios of45±10 pptv at 20 km. These results are in excellent agreement with theREPROBUS 3D model simulations, which indicate that the observed OClOcorresponds to daytime ClO and BrO mixing ratios of 1.2 ppbv and 10 pptv,respectively.     

Mountaineering incidents in France: analysis of search and rescue interventions on a 10-year period(from 2008 to 2018)

In Europe and especially in France,there is a growing enthusiasm for outdoor sports and recreation.In the meantime,the risk of both severe and frequent injuries associated with active pursuits is acknowledged,especially in mountainous areas.The effectiveness of prevention must rely on detailed knowledge of typical circumstances and scenarios but thorough understanding of the mechanisms of accidentality remains limited by the fragmentation of sources and by mostly heterogeneous methodologies.This paper aims at giving insights on victims’profiles,season,location,and circumstances of mountaineering accidents in the French Alps,through the study of rescue interventions data from 2008 to 2018.Thanks to the analysis of the exhaustive database of search and rescue interventions from the French mountain national police force,and while questioning its limitations,we strive to answer two questions:what are the characteristics of the hazardous situations leading to a rescue intervention in mountaineering?Among these situations,what are the characteristics that tend to make them more harmful?