Jean-Pierre Barriot

TIARES Project—Tomographic investigation by seafloor array experiment for the Society hotspot

We conducted geophysical observations on the French Polynesian seafloor in the Pacific Ocean from 2009 to 2010 to determine the mantle structure beneath the Society hotspot, which is a region of underlying volcanic activity responsible for forming the Society Islands. The network for Tomographic Investigation by seafloor ARray Experiment for the Society hotspot (TIARES, named after the most common flower in Tahiti) is composed of multi-sensor stations that include broadband ocean-bottom seismometers, ocean-bottom electro-magnetometers, and differential pressure gauges. The network is designed to obtain seismic and electrical conductivity structures of the mantle beneath the Society hotspot. In addition to providing data to study the mantle structure, the TIARES network recorded unprecedented data of pressure and electromagnetic (EM) signals by tsunamis associated with large earthquakes in the Pacific Ocean, including the 2010 Chilean earthquake (Mw 8.8).

The evolution of precipitable water and precipitation over the Island of Tahiti from hourly to seasonal periods

The Island of Tahiti (French Polynesia) has a complex meteorological context governed by the South Pacific convergence zone on a large scale and the topography of a high volcanic island on the orographic scale. The island is subject to heavy rainfall (up to 8000 mm year–1 in some areas), mainly during the rainy season (November to April), generating significant geo-morphological changes and property damage each year. To better understand the underlying complex mechanisms leading to precipitation over a broad range of timescales (from hourly to seasonal), we have analysed eight years of data (2001–2008) coming from five sources: a radiometer, radiosoundings, a GPS, Era-Interim reanalysis, and two rain gauges, all located close to or inside the Matatia valley, a small typical Tahitian valley. In particular, we have decomposed the precipitable water distribution into two statistical distributions corresponding to the dry and wet seasons. The time evolution of precipitable water in the dry season is characterized by a log-normal distribution, while the precipitable water time evolution in the wet season is characterized by a reverse log-normal distribution. The bimodality of the probability distributions describing the dynamical processes involved in the Tahiti climate is confirmed by the study of the diurnal evolution in absolute humidity, precipitable water, and precipitation.

The Tsunami of March 11, 2011 as Observed by the Network of Tide Gauges of French Polynesia

We present here the network of tide gauges spanning French Polynesia, and the set of records made by this network of the tsunami wave of March 11, 2011 (Tōhoku earthquake). We also outline the least-squares procedure used to separate the tsunami signal from the oceanic tides signal.

Toward a Normalized XML Schema for the GGP Data Archives

Since 1997, the Global Geodynamics Project (GGP) stations have used a text-based data format. The main drawback of this type of data coding is the lack of data integrity during the data flow processing. As a result, metadata and even data must be checked by human operators. In this paper, we propose a new format for representing the GGP data. This new format is based on the eXtensible Markup Language (XML).

Modeling of tropospheric integrated water vapor content using GPS, radiosonde, radiometer, rain gauge and surface meteorological data in a tropical region (French Polynesia)

The integrated precipitable water vapor (IPW) is characterized by strong spatial and temporal variability, especially over tropical regions where the troposhere is not purely in hydrostatic equilibrium (convection). As an evidence, the survey of water vapor distibution as permanently as possible is an important issue and should serve as inputs for tropical climate modelling. In this paper, we present an estimation of the IPV from ground ba,.sed GPS receivers, which we compare to radiosondes and microwave radiometer. The data used here were collected in the vicinity of French Polynesia University site, during eight years from 2001 to 2008. In addition, we also include the IPW calculated using Era-Interim reanalyses (ECMWF). The main purpose of this paper is to highlight precision, qualities and limitations of each method available on the Island of Tahiti. During wet periods, the radiosondes vertical profiles of water vapor show an efficient mixing of water vapor between the the boundary layer (below trade winds inversion at Tahiti) and the free troposphere. Thus the rainy event detection allows to better constrain the validity range of a model of the vertical distribution of water vapor, which is based on a pseudo-adiabatic saturated evolution of the temperature.