Climatic analysis linked to land vegetation cover of Mexico by applying multivariate statistical and clustering analysis

"Se delimitan las regiones climáticas de México mediante el análisis jerárquico de agrupamiento. Los datos utilizados fueron medias mensuales de temperatura máxima y mínima y la precipitación mensual acumulada, obtenidas de estaciones climáticas en México para el periodo 1961-2004. Este método de agrupamiento asigna cada variable de precipitación y temperatura a grupos con base en características estadísticas similares. Se realizó un análisis de componentes principales para obtener una matriz estandarizada que se utilizó en el agrupamiento. Aplicando dos criterios de agrupamiento (K-means y Ward) fue posible definir estadísticamente los grupos de estaciones que delimitan regiones de clima similar. Además, la metodología empleada describe la distribución de la vegetación dominante para cada región climática. Este análisis puede contribuir a la generación de nuevos escenarios climáticos, donde puede incluirse la dinámica de la cobertura vegetal como bioindicador del clima.""The climate regions of Mexico are delimitated using hierarchical clustering analysis (HCA). The data used consists of monthly means of maximum and minimum temperatures and monthly-accumulated precipitation. The dataset was obtained from heterogeneously distributed climatic stations in Mexico for the period from 1961 to 2004. This cluster method assigns precipitation and temperature variables to groups of clusters based on similar statistical characteristics. We carried out a principal components analysis to obtain a standardized reduced matrix to be used in HCA. By applying two clustering criteria (K-means and Ward´s method) it was possible to define statistically groups of stations that delimit regions of similar climate. In addition, the applied methodology describes the dominant vegetation distribution for each climate region. This analysis may contribute to the generation of new climate scenarios, where the dynamics of land vegetation cover could be included as a biomarker of climate.

Regionalization and classification of bioclimatic zones in the central-northeastern region of México using principal component analysis (PCA)

"Utilizando un análisis de componentes principales, determinamos zonas climáticas en un gradiente topográfico en la zona centro-noreste de México. Se emplearon datos de precipitación y temperatura medias mensuales por un período de 30 años de 173 estaciones meteorológicas. La clasificación del clima fue llevada a cabo de acuerdo con el sistema de Köppen modificado para las condiciones de México. El análisis de componentes principales indicó una regionalización que concuerda con características de topografía y vegetación. Se describen zonas bioclimáticas, asociadas a vegetación típica para cada clima, usando sistemas de información geográfica (SIG).""Applying principal component analysis (PCA), we determined climate zones in a topographic gradient in the central-northeastern part of México. We employed nearly 30 years of monthly temperature and precipitation data at 173 meteorological stations. The climate classification was carried out applying the Köppen system modified for the conditions of México. PCA indicates a regionalization in agreement with topographic characteristics and vegetation. We describe the different bioclimatic zones, associated with typical vegetation, for each climate using geographical information systems (GIS).

Lagrangian trajectories, residual currents and rectification process in the Northern Gulf of California

"Considering a semi-implicit approximation of the Coriolis terms, a numerical solution of the vertically integrated equations of motion is proposed. To test the two-dimensional numerical model, several experiments for the calculation of Euler, Stokes and Lagrange residual currents in the Gulf of California were carried out. To estimate the Lagrangian residual current, trajectories of particles were also simulated. The applied tidal constituents were M2, S2, K2, N2, K1, P1 and O1. At spring tides, strong tidal velocities occur in the northern half of the gulf. In this region of complex geometry, depths change from a few meter in the northern shelf zone to more than 3000 m in the southern part. In the archipelago region, the presence of islands alters amplitude and direction of tidal currents producing a rectification process which is reflected in a clockwise circulation around Tiburón Island in the Lagrangian residual current. The rectification process is explained by the superposition of the Euler and Stokes residual currents. Residual current patterns show several cyclonic and anticyclonic gyres in the Northern Gulf of California. Numerical experiments for individual and combinations of several tidal constituents revealed a large variability of Lagrangian trajectories.

Estimation of total yearly CO2 emissions by wildfires in Mexico during the period 1999–2010

"The phenomenon of wildfires became a global environmental problem which demands estimations of their CO2 emissions. Wildfires have deteriorated the air quality increasingly. Using available information on documented wildfires and a data set of satellite detected hot spots, total yearly emissions of CO2 in Mexico were estimated for the period 1999-2010. A map of the main vegetation groups was used to calculate total areas for every vegetation type. The yearly number of hot spots per vegetation type was calculated. Estimates of emitted CO2 in a wildfire were then accomplished by considering parameters such as: forest fuel load, vegetation type, burning efficiency, and mean burned area. The number of wildfires and total affected areas showed an annual variability. The yearly mean of affected area by a single wildfire varied between 0.2 and 0.3 km(2). The total affected area during the period 1999 to 2010 was 86800 km(2) which corresponds to 4.3% of the Mexican territory. Total CO2 emissions were approximately 112 Tg. The most affected vegetation types were forest and rainforest.

Modeling of groundwater flow and water use for San Luis Potosí Valley aquifer system

"Land use changes are currently one of the indisputable factors in the alteration of processes and cycles of the aquifer system in the San Luis Potosí Valley. Due to its importance, is considered indispensable to investigate this detrimental factor of aquifers. The aim of this research is to use a numerical flow model to analyze the impact that land use changes have had on the aquifer. A finite differences numerical model was adapted to the size and hydrological properties of the aquifer system. It consisted of a regular grid with 30 columns and 34 rows with constant spacing of 1000 meters. It has two layers; the first includes the shallow aquifer and the second, the deep aquifer. The initial hydraulic head of the model corresponds to 1986 and was verified for 1995 and 2007. The model shows the development of a drawdown cone (central valley) extending toward the industrial area (southern valley). Piezometric water levels revealed a decrease of 0.6 to 1.6 meters annually during a period from 1977 to 2007. This work demonstrates that it is the consequence of land use changes and of the incessant overall decline in groundwater reserves. Based on the flow model, population growth projections and water use change, the calculated predictions indicate that by 2021, the total established volume of 136 Mm3/year for consume will be reached. The flow model of the San Luis Potosí Valley aquifer system shows a clear effect of the risks associated with aquifer mining.

Influence of sugarcane burning on soil carbon and nitrogen release under drought and evapotranspiration conditions in a Mexican sugarcane supply zone

"Sugarcane cultivation is an agricultural activity of worldwide importance. This crop has been cultivated in Mexico for centuries, impacting important productive areas like the study region called Huasteca Potosina which is located at the Central-East part of Mexico. The relationship between soil conditions, weather and production per hectare allows identifying the edaphological and climatic conditions (aptitude levels) for cultivating sugarcane in the study area. The objective of this research work is to analyze the relation between the cultivated hectares and production of sugarcane. Likewise, to explain its behavior and interpret the contribution of N and C released to the atmosphere for burning sugar cane in association with events and meteorological parameters involved in the flux of water between soil and atmosphere such as drought, evapotranspiration and rainfall. The methods and indicators for burning waste provided by the Intergovernmental Panel on Climate Change (IPCC), the value of potential evapotranspiration as Thornthwaite and drought severity index were applied in order to understand the correlations between the drought severity index and potential evapotranspiration, and between C and N release and potential rainfall availability. The results show the increment of harvested hectares and the loss of water from the soil by the increase of periods of drought events and evapotranspiration. The volatilized nutrients in soil varied from 1.32 x 105 to 2.17 x 105 t for C and from 1.32 x 103 t to 2.17 x 103 t for N during the burning of sugarcane, affecting production levels with values fluctuating between 38 t/ha to 77 t/ha for the term of 1990-2010.""El cultivo de caña de azúcar es una actividad agrícola de importancia mundial llevada a cabo en México durante siglos, impactando importantes áreas productivas como la región de estudio llamada Huasteca Potosina, localizada al este central de México. La relación entre las condiciones del suelo, clima y producción por hectárea permite identificar las condiciones edafológicas y climáticas (niveles de aptitud) para cultivar la caña de azúcar en el área de estudio. Bajo este contexto, el objetivo fue analizar la relación entre las hectáreas cultivadas y la producción de caña de azúcar y explicar su comportamiento al interpretar las contribuciones del N y C liberados a la atmósfera por la quema de caña asociados a eventos y parámetros meteorológicos involucrados en el flujo de agua entre el suelo y la atmósfera como sequía, evapotranspiración y lluvia. Los métodos e indicadores para la quema de residuos provistos por el Panel Intergubernamental del Cambio Climático (IPCC. por sus siglas en inglés), el valor de la evapotranspiración potencial por Thornthwaite y el índice de severidad de la sequía fueron aplicados para comprender las correlaciones entre el índice de severidad de la sequía y la evapotranspiración potencial, así como entre el C y el N liberados y la disponibilidad potencial de lluvia. Los resultados muestran el incremento en las hectáreas cosechadas y la pérdida de agua del suelo por el aumento de los periodos de sequía y la evapotranspiración. Los nutrientes del suelo volatilizados, varían de 1.32 x 105 ton a 2.17 x 105 ton para C y 1.32 x 103 ton a 2.17 x 103 ton para N durante la quema de caña de azúcar, lo que afecta sus niveles de producción con valores que fluctúan entre 38 t/ha y 77 t/ha durante el periodo 1990-2010.

Sand waves generation: a numerical investigation of the Infiernillo Channel in the Gulf of California

"The effect of the coastal geometry on sand bed forms generation has been investigated for a tidal dominated area. Different hypothetical geometries of coastal channels with flat bottoms and unlimited sediment availability were exposed to strong oscillatory tidal currents to simulate the interaction of hydrodynamics and the bedload sediment transport. The hypothetical geometries stand for the idealization of the principal geographic features of the Infiernillo Channel, a coastal area of the Gulf of California where sandbanks and sand waves have been observed. A depth integrated hydrodynamic-numerical model and a parameterized formula to estimate the bedload sediment transport were applied coupled with a sediment conservation equation to determine the sea bottom morphodynamics. Model predictions in the Infiernillo Channel were compared to available satellite imagery. This investigation demonstrates that a vertical integrated numerical model is able to reproduce the development of incipient sand waves that exist in the Infiernillo Channel. Incipient sandbanks and shoals were also simulated. Sand waves with wavelengths of about 200 m were calculated on the same locations where sand waves actually exist. A crucial finding of this research was to show that the geometry of a shallow water basin and the presence of tidal velocity gradients associated with abrupt changes in the coastline alignment were critical in determining the sand-bed pattern generation. We demonstrate that a vertical variation of tidal currents is not necessary to generate sand waves.

A new theory on tidal currents rotation

"Applying the linearized equations of motion, projection on the complex plane and a representation of the velocity vector and the forcing sea surface elevation gradient in function of the eigenvectors of the homogeneous system, we developed a theory that explains essential properties of tidal currents. We found the existence of a fundamental vector which we call sense of rotation s. The ellipticity, until now defined as a scalar quantity, results from the theory as a vector ɛ, normalized from s. ɛ is a measure of the eccentricity and sense of rotation of tidal ellipses and has some properties that are similar to those of the angular velocity. We derived an expression for the major and minor semi-axis in function of physical properties and characteristics of amphidromic systems. These and other results of the theory allow the analysis of important aspects of tidal currents.

Tropical coral reef system hydrodynamics in the western Gulf of Mexico

"The acoustic Doppler current profiler, temperature, salinity and density data set were recorded monthly over the course of a year in a tropical coral reef system to elucidate the effects of abrupt bathymetric changes on current variability and surface temperature over time. A minimum of five transect repetitions were performed during one diurnal tidal cycle each month during the year 2008. According to the empirical orthogonal functions, the dominant terms were advection and friction due to the shallowness of the system and the relatively short continental shelf located in front of the Port of Veracruz (Mexico). The data showed the dominance of the northwest-southeast current velocity components (parallel to the coast) attributed to the winds. The southeastward current velocity was the dominant component throughout the year, followed by the northwestward current velocity component. The data suggested that coral reefs produce current rectification near the shallow reef areas (1 m depth). No correlation existed between surface temperature and the chlorophyll-a levels throughout the year. Residual current velocities throughout the year never reached more than 50 cm s–1 during the sampling periods, and the surface temperature varied from 21 to 30°C, with the highest temperature being observed near the coast and reefs. Finally there was a direct correlation of the northeasterly and strong northwesterly winds with the well-mixed cold-salty water column in the reef area.""Las corrientes marinas, la temperatura del agua, la salinidad y densidad del mar fueron registradas mensualmente a lo largo de un año, en un sistema de arrecifes coralinos del Golfo de México, para obtener los efectos de los cambios batimétricos sobre la variabilidad de las corrientes marinas y de la temperatura superficial. Se realizó un mínimo de cinco repeticiones, para cada transecto durante un ciclo de marea diurna, de forma mensual durante el 2008. De acuerdo con las Funciones Ortogonales Empíricas (EOF), los términos dominantes fueron la advección y la fricción. Esto se debió a la poca profundidad del sistema (<45 m) y a la plataforma continental, relativamente corta, situada frente al puerto de Veracruz (México). Los datos mostraron que la componente de velocidad dominante en el sistema es paralela a la costa (sureste-noroeste) principalmente debido al régimen de vientos. La dirección de la velocidad de la corriente dominante fue hacia el sureste seguida por el componente noroeste. Los datos sugieren que los arrecifes de coral producen una rectificación de la corriente cerca de las zonas de arrecifes poco profundas (1 m de profundidad). No se encontró en este estudio una correlación entre la temperatura de la superficie y los niveles de clorofila-a lo largo del año. Las velocidades de las corriente residual a lo largo del año no rebasaron los 50 cm s–1 durante los períodos de muestreo, y la temperatura superficial variaron de 21 a 30°C. La temperatura más alta se observó cerca de la costa y los arrecifes. Por último, existe una correlación directa entre los vientos del noroeste con la columna de agua mezclada (fría y salada) en el área muestreada.

Approximation of a Convective-Event-Monitoring System Using GOES-R Data and Ensemble ML Models

The presence of deep convective clouds is directly related to potential convective hazards, such as lightning strikes, hail, severe storms, flash floods, and tornadoes. On the other hand, Mexico has a limited and heterogeneous network of instruments that allow for efficient and reliable monitoring and forecasting of such events. In this study, a quasi-real-time framework for deep convective cloud identification and modeling based on machine learning (ML) models was developed. Eight different ML models and model assembly approaches were fed with Interest Fields estimated from Advanced Baseline Imager (ABI) sensor data on the Geostationary Operational Environmental Satellite-R Series (GOES-R) for one region in central Mexico and another in northeastern Mexico, both selected for their intense convective activity and high levels of vulnerability to severe weather. The results indicate that a simple approach such as Logistic Regression (LR) or Random Forest (RF) can be a good alternative for the identification and simulation of deep convective clouds in both study areas, with a probability of detection of (POD) ≈ 0.84 for Los Mochis and POD of ≈ 0.72 for Mexico City. Similarly, the false alarm ratio (FAR) ≈ 0.2 and FAR ≈ 0.4 values were obtained for Los Mochis and Mexico City, respectively. Finally, a post-processing filter based on lightning incidence (Lightning Filter) was applied with data from the Geostationary Lightning Mapper (GLM) of the GOES-16 satellite, showed great potential to improve the probability of detection (POD) of the ML models. This work sets a precedent for the implementation of an early-warning system for hazards associated with intense convective activity in Mexico