Northwestern Mexico experiences large variations in water vapor on seasonal time scales in association with the North American monsoon, as well as during the monsoon associated with upper-tropospheric troughs, mesoscale convective systems, tropical easterly waves, and tropical cyclones. Together these events provide more than half of the annual rainfall to the region. A sufficient density of meteorological observations is required to properly observe, understand, and forecast the important processes contributing to the development of organized convection over northwestern Mexico. The stability of observations over long time periods is also of interest to monitor seasonal and longer-time-scale variability in the water cycle. For more than a decade, the U.S. Global Positioning System (GPS) has been used to obtain tropospheric precipitable water vapor (PWV) for applications in the atmospheric sciences. There is particular interest in establishing these systems where conventional operational meteorological networks are not possible due to the lack of financial or human resources to support the network. Here, we provide an overview of the North American Monsoon GPS Transect Experiment 2013 in northwestern Mexico for the study of mesoscale processes and the impact of PWV observations on high-resolution model forecasts of organized convective events during the 2013 monsoon. Some highlights are presented, as well as a look forward at GPS networks with surface meteorology (GPS-Met) planned for the region that will be capable of capturing a wider range of water vapor variability in both space and time across Mexico and into the southwestern United States.
During the last two decades, Global Positioning System (GPS) geodetic-grade receivers and accelerometers have been implemented in Structural Health Monitoring (SHM). Most recently, the use of sensors integrated in smartphones has been evolving. Although some of their capabilities are validated for small and local structures, there is a gap in knowledge about the use of sensors embedded in smartphones and other electronic devices for SHM of complex structures as bridges. To contribute in this area, this paper demonstrates the application of GPS receivers, accelerometers, and smartphones, integrating a smart sensor for the SHM of bridges. In order to validate its capabilities, the alternative smart sensor is used to study a particular bridge with vibration problems. Semistatic and dynamic displacements are obtained by means of GPS measurements. Accelerations in three directions of the bridge are determined using the accelerometer and the smartphone. Based on the results of the alternative smart sensor, inappropriate structural behavior is detected in the vertical direction of the bridge. In addition, dynamic characteristics are extracted using the smart sensor applying the Fast Fourier Transformation (FFT) and periodogram to the structural responses. As a result, it is verified the applicability of the fused smart sensor for SHM on real-scale bridges.
We conducted a baseline comparison for instrument calibration using GPS (Global Positioning System) and EDM (Electronic Distance Measurement) observations. The experiment was carried out at campus of the Autonomous University of Sinaloa (UAS) in Culiacan, Mexico. The main objective of this research was to establish a short (~125 m) baseline for calibration of geodeticgrade GPS and EDM instruments of different commercial brands to validate the precision specifications offered by the manufacturers of such instruments. We compared three types of geodetic-grade GPS receivers: Topcon Hiper Lite +, Ashtech Z-Xtreme and Leica SR500 and three types of EDM: Topcon GTS-236W, Pentax R-326EX and Leica TC-407. For the experiment, the baseline components were computed by using ionosphere-free double-difference (DD) GPS carrier phase observations processed using the PAGES software (Program for the Adjustment of GPS EphemerideS). The GPS data were processed with a 1-second sampling rate, 10-degree cutoff angle, and precise GPS orbits disseminated by IGS (International GNSS Service). The length of the calibration baseline was also obtained by averaging 20 measurements of line length directly recorded by the three different EDM instruments. GPS results agree among different brands with differences of ±2 mm in contrast with the resulting EDM values that differ within ±3 mm.
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