Jorge Zavala-Hidalgo

Isthmus of Tehuantepec Wind Climatology and ENSO Signal

Abstract The statistical characteristics of the winds at the Isthmus of Tehuantepec and their seasonal and interannual variability are studied through the analysis of several datasets and a reconstruction of the winds for a 31-yr period. Observations show that the long-term monthly mean wind speeds and frequency of occurrence of northerly winds have a strong seasonal signal, with maximum values during December–January, minimum during May–June, and a relative maximum in July. The frequency distribution of wind speed is bimodal, a feature that is closely related to the wind direction, with northerly winds being stronger. Based on these results and the close relationship between the across-Isthmus pressure differences and the local winds, a statistical model is developed to get a reconstruction of 12-hourly winds through the Isthmus of Tehuantepec for 1964–95. The model reproduces fairly well the main characteristics of the observed winds: the bimodal distribution of the wind speed and the seasonal signal in...

Cyclonic eddies northeast of the Campeche bank from altimetry data

Eight cyclonic eddies were identified near the western edge of the Loop Current, at the northeast shelf break of the Campeche Bank, through TOPEX/Poseidon sea surface height anomaly data from January 1993 through March 2000. The eddies’ migration and their lifecycle are described. The formation of the eddies appears to be related to the dynamics of the Loop Current because the timing of their generation corresponds to the last stage of the anticyclone shedding from the Loop Current. The cyclones intensify while moving slightly to the northwest along the shelf break of the Campeche Bank; later, some cyclones are observed to move northward toward the Mississippi shelf break. The cyclones remain next to the Campeche Bank, south of 268N, from 1.3 to 9.6 months; later, some of them move northward and strengthen by merging with other eddies, extending their life span. The eddies’ vertical structure is analyzed with hydrographic data, and the connection between the formation of the cyclones and the evolution of the Loop Current is further described using sea surface temperature images.

The seasonal variability of continental shelf circulation in the northern and western Gulf of Mexico from a high-resolution numerical model

The seasonal variability of circulation on the continental shelves of the northern and western Gulf of Mexico is explained using observational data and a high-resolution numerical model. It is shown that the primarily wind-driven circulation governs the salinity field on the shelves by transporting low-salinity water formed by river discharge along seasonally shifting pathways. When buoyant low-salinity water is present over the outer continental shelf near the shelf edge, it is available for entrainment in currents associated with the mesosocale eddy field of the Gulf. The preferred locations for this cross-shelf export of fresh water shift seasonally as the shelf circulation transports low-salinity water along shelf, and impact the upper ocean salinity field throughout the Gulf. A low-salinity tongue is found in the monthly climatology in the Bay of Campeche during the winter months, and another extends southeastward from De Soto Canyon along the eastern edge of the Loop Current during the summer. A similar pattern can be seen in the monthly climatology chlorophyll concentration produced from remotely-sensed ocean color data, suggesting that the biological properties of the surface waters of the Gulf may be controlled by this combined wind-driven shelf circulation and eddy interaction mechanism responsible for redistributing river-discharged fresh water.

Midsummer Gap Winds and Low-Level Circulation over the Eastern Tropical Pacific

Abstract The low-level seasonal and intraseasonal wind variability over the northeastern tropical Pacific (NETP), its relationship with other variables, and the connection with large- and middle-scale atmospheric patterns are analyzed using a suite of datasets. Quick Scatterometer (QuikSCAT) wind data show that the low-level circulation over the NETP is mainly affected by the northerly trades, the southerly trades, and the wind jets crossing through the Tehuantepec, Papagayo, and Panama mountain gaps. The seasonal and intraseasonal evolution of these wind systems determines the circulation patterns over the NETP, showing predominant easterly winds in winter and early spring and wind direction reversals in summer over the central region of the NETP. During summer, when southerly trades are the strongest and reach their maximum northward penetration, weak westerlies are observed in June, easterlies in July–August, despite that strong southerlies tend to turn eastward, and again westerlies in September–Octob...

An open source Java web application to build self-contained web GIS sites

This work describes OWGIS, an open source Java web application that creates Web GIS sites by automatically writing HTML and JavaScript code. OWGIS is configured by XML files that define which layers (geographic datasets) will be displayed on the websites. This project uses several Open Geospatial Consortium standards to request data from typical map servers, such as GeoServer, and is also able to request data from ncWMS servers. The latter allows for the displaying of 4D data stored using the NetCDF file format (widely used for storing environmental model datasets). Some of the features available on the sites built with OWGIS are: multiple languages, animations, vertical profiles and vertical transects, color palettes, color ranges, and the ability to download data. OWGIS main users are scientists, such as oceanographers or climate scientists, who store their data in NetCDF files and want to analyze, visualize, share, or compare their data using a website. Display Omitted Open Source Java application that builds Web GIS interfaces from XML files.Capable of displaying 4D data, stored as NetCDF files, from ncWMS servers.Important features are: animations, vertical profiles, and vertical transects.Successfully used to display oceanographic data obtained from the HYCOM model.

On the wind power potential in the northwest of the Yucatan Peninsula in Mexico

Wind power density, vertical velocity profiles, and other wind characteristics were established using a 51 m meteorological mast located very close to the shoreline on the northwest of the Yucatan peninsula in the Gulf of Mexico. A comparative study of the wind power density was carried out using information obtained between September 2010 and September 2011. The wind speed probability density function was found to be bimodal due to sea-land breezes, a characteristic that becomes less evident as the vertical distance to the ground increases. The distinction between these two wind regimes was used to fit the Weibull-Weibull curve using a linear least-squares criterion in the parameters. In addition, numerical simulations from a mesoscale model are in close agreement with measurements above z = 50 m (z is the vertical distance to the ground). This result suggests that some mesoscale simulations may serve as a preliminary wind energy assessment tool in coastal zones with extended low-lying areas.

On the formation and interaction of cyclonic eddies with the Loop Current using NCOM and a suite of observations

The life cycle of cyclonic eddies associated with the Loop Current (LC) evolution is studied using the Navy Coastal Ocean Model, TOPEX/Poseidon altimetry, and AVHRR images. It is shown that the longest period registered between eddy shedding, between February 1998 and August 1999, is associated with the presence of a large cyclone that remains north of the LC during several months. Using numerical simulations, it is shown that large cyclones develop sporadically in the region and that they block the northward penetration of the LC. The LC is shifted to the east and leaks mass, momentum, and energy through a jet and small anticyclones moving along the slope of the West Florida Shelf, east of the cyclone. The process causes an enlargement of the period between eddy shedding.

Seasonal variability of the export of river discharged freshwater in the northern Gulf of Mexico

Numerical simulations of the Gulf of Mexico (GoM) using the Navy Coastal Ocean Model (NCOM) predict a seasonal signal of surface salinity throughout the northern Gulf. The model variability of salinity and currents is compared to historical hydrographic data and to transport inferred from drifting buoys. Model experiments are used to examine the roles of mesoscale eddy activity and the seasonal variability of wind forcing and river discharge in connection with the upper ocean salinity field. It is shown that the annual cycle of the local winds greatly influences the fate of the Mississippi River. Model results and drifter data show that the low salinity water is directed westward over the broad Louisiana-Texas (LATEX) shelf in the fall and winter where it remains trapped to the coast. This water is transported southward as a coastally attached current and often offshore by jets associated with eddy pairs along the western continental margin. In the spring and summer, the low salinity water of the northern Gulf spreads over deeper water to the east of the Mississippi Delta where it is influenced by the offshore circulation. Mesoscale eddies associated with the Loop Current (LC) can then entrain the low salinity water and transport it to great distances from its origin.

Sedimentary records of recent sea level rise and acceleration in the Yucatan Peninsula

Abstract Recent eustatic sea level rise (SLR) is one of the most striking manifestations of recent climate change as it directly impacts coastal activities and ecosystems. Although global SLR is well-known, local values differ due to vertical land motion, and changes in atmospheric pressure, ocean currents and temperatures. Although a reliable estimation of local SLR trends is needed to assess coastal zone vulnerabilities and plan adaptation strategies, instrumental records are usually short or sparse, especially in developing countries. Here we show that 210Pb-dated sedimentary records from mangrove saltmarshes can provide useful decadal records of local SLR trends. We quantified sediment accretion rates in sediment cores from remote mangrove saltmarshes of the Yucatan Peninsula. Best SLR records were observed for cores collected near mean sea level (MSL). During most of the XX century the SLR rate ranged from 1-2 mm yr-1, increased to a maximum of 4.5 ± 0.6 mm yr-1 and the acceleration was 0.13 mm yr-2. Assuming either a constant SLR rate or acceleration, by the end of this century MSL level will be 39 cm or 91 cm above the present value. Both coastal infrastructures and ecosystems will be negatively affected by SLR and society will need to adapt relatively fast to the new conditions.

Coastal and river flood risk analyses for guiding economically optimal flood adaptation policies: A country-scale study for Mexico

Many countries around the world face increasing impacts from flooding due to socio-economic development in flood-prone areas, which may be enhanced in intensity and frequency as a result of climate change. With increasing flood risk, it is becoming more important to be able to assess the costs and benefits of adaptation strategies. To guide the design of such strategies, policy makers need tools to prioritize where adaptation is needed and how much adaptation funds are required. In this country-scale study, we show how flood risk analyses can be used in cost–benefit analyses to prioritize investments in flood adaptation strategies in Mexico under future climate scenarios. Moreover, given the often limited availability of detailed local data for such analyses, we show how state-of-the-art global data and flood risk assessment models can be applied for a detailed assessment of optimal flood-protection strategies. Our results show that especially states along the Gulf of Mexico have considerable economic benefits from investments in adaptation that limit risks from both river and coastal floods, and that increased flood-protection standards are economically beneficial for many Mexican states. We discuss the sensitivity of our results to modelling uncertainties, the transferability of our modelling approach and policy implications. This article is part of the theme issue ‘Advances in risk assessment for climate change adaptation policy’.