The land‐sea thermal contrast (LSTC) that is present at the initial stage of the North American Monsoon is analyzed as a principal driving mechanism for monsoon onset interannual variability. The vertically integrated moisture flux convergence (MFC) averaged over the core monsoon during June 16–30, derived from North American Regional Reanalysis daily fields for the period 1979–2006, is proposed as an index for initial monsoon intensity. We quantify the LSTC associated to the monsoon and propose a dynamic connection between the thermal contrast and the initial monsoon intensity. It consists of a directly proportional relation between the LSTC, the surface pressure gradient along the Gulf of California, and the ensuing low level (below 850 mb) moisture transport (from the southern Gulf of California and eastern tropical Pacific) and precipitation in the core region.

The hypothesis that global warming during the twenty-first century will increase the land–sea thermal contrast (LSTC) and therefore the intensity of early season precipitation of the North American monsoon (NAM) is examined. To test this hypothesis, future changes (2075–99 minus 1979–2004 means) in LSTC, moisture flux convergence (MFC), vertical velocity, and precipitation in the region are analyzed using six global climate models (GCMs) from phase 5 of the Coupled Model Intercomparison Project (CMIP5) under the representative concentration pathway 8.5 (RCP8.5) emission scenario. A surface LSTC index shows that the continent becomes warmer than the ocean in May in the North American Regional Reanalysis (NARR) and ECMWF Interim Re-Analysis (ERA-Interim) and in June in the mean ensemble of the GCMs (ens_GCMs), and the magnitude of the positive LSTC is greater in the reanalyses than in the ens_GCMs during the historic period. However, the reanalyses underestimate July–August precipitation in the NAM region, while the ens_GCMs reproduces the peak season surprisingly well but overestimates it the rest of the year. The future ens_GCMs projects a doubling of the magnitude of the positive surface LSTC and an earlier start of the continental summer warming in mid-May. Contrary to the stated hypothesis, however, the mean projection suggests a slight decrease of monsoon coastal precipitation during June–August (JJA), which is attributed to increased midtropospheric subsidence, a reduced midtropospheric LSTC, and reduced MFC in the NAM coastal region. In contrast, the future ens_GCMs produces increased MFC and precipitation over the adjacent mountains during JJA and significantly more rainfall over the entire NAM region during September–October, weakening the monsoon retreat.

We estimate trends of extreme daily precipitation (P95 > 95th percentile) events in the core of the North American monsoon region in Northwest Mexico during JJAS of 1961–1998. The intensity and seasonal contribution of P95 show significant upward linear trends in the mountain sites, which appear to be related to an increased contribution from heavy precipitation derived from tropical cyclones (TCs). Frequency of P95, total monsoon precipitation, and P95 in coastal stations did not change significantly. TC‐derived P95 events are associated with SST anomalies similar to weak La Niña conditions in the eastern Equatorial Pacific, SSTs > 28.5°C in the Caribbean Sea, and strong land‐sea thermal contrast over Northwest Mexico and the U.S. Southwest two weeks prior to their onset.

In this study the results of two regional fifth-generation Pennsylvania State University-NCAR Mesoscale Model (MM5) simulations forced at their boundaries with low-pass-filtered North American Regional Reanalysis (NARR) composite fields from which synoptic-scale variability was removed are presented. The filtered NARR data are also assimilated into the inner domain through the use of field nudging. The purpose of this research is to investigate wet and dry onset modes in the core region of the North American monsoon (NAM). Key features of the NAM that are present in the NARR fields and assimilated into the regional simulations include the position of the midlevel anticyclone, low-level circulation over the Gulf of California, and moisture flux patterns into the core monsoon region, for which the eastern Pacific is the likely primary source of moisture. The model develops a robust diurnal cycle of deep convection over the peaks of the Sierra Madre Occidental (SMO) that results solely from its radiation scheme and internal dynamics, in spite of the field nudging. The wet onset mode is related to a regional land-sea thermal contrast (LSTC) that is ;28C higher than in the dry mode, and is further characterized by a northward-displaced midlevel anticyclone, a stronger surface pressure gradient along the Gulf of California, larger mean moisture fluxes into the core region from the eastern Pacific, a stronger diurnal cycle of deep convection, and the more northward distribution of precipitation along the axis of the SMO. A proposed regional LSTC mechanism for NAM onset interannual variability is consistent with the differences between both onset modes.

No abstract

The Earth′s climate is warming, especially in the mid- and high latitudes of the Northern Hemisphere. The northern elephant seal (Mirounga angustirostris) breeds and haul-outs on islands and the mainland of Baja California, Mexico, and California, U.S.A. At the beginning of the 21st century, numbers of elephant seals in California are increasing, but the status of Baja California populations is unknown, and some data suggest they may be decreasing. We hypothesize that the elephant seal population of Baja California is experiencing a decline because the animals are not migrating as far south due to warming sea and air temperatures. Here we assessed population trends of the Baja California population, and climate change in the region. The numbers of northern elephant seals in Baja California colonies have been decreasing since the 1990s, and both the surface waters off Baja California and the local air temperatures have warmed during the last three decades. We propose that declining population sizes may be attributable to decreased migration towards the southern portions of the range in response to the observed temperature increases. Further research is needed to confirm our hypothesis; however, if true, it would imply that elephant seal colonies of Baja California and California are not demographically isolated which would pose challenges to environmental and management policies between Mexico and the United States.

ResumenEn este ensayo se explora la posible seguridad con soberanía alimentaria de México en la primera mitad del siglo XXI, dado el cambio climático inminente. Las condiciones iniciales incluyen una población nacional en crecimiento, una dependencia alimentaria creciente, y un modelo de aprovechamiento de los recursos naturales históricamente extractivista, que ha conducido a su degradación significativa. Se da por hecho, que la tecnología agrícola de que dispone el campo será obsoleta dentro de la primera mitad del siglo debido al cambio climático, siendo la disponibilidad de agua para los cultivos y su tolerancia genética a la sequía y a temperaturas extremas las variables centrales de la producción de alimentos. Se resalta la fragilidad de la mitad de la tierra de labor en ladera al cambio climático, debido a su exposición a la erosión del suelo por falta de protección. Se discuten adaptaciones urgentes al manejo de los recursos para corregir la acumulación diferida de inversión protectora. Se analiza planes de investigación de plazo intermedio (5 a 10 años) y de plazo largo (20 a 40 años). El primero para desarrollar tecnologías de transición y el segundo para desarrollar tecnología adecuada a etapas avanzadas de cambio climático. Se observa la necesidad 1) de tecnologías Abstract This essay explores the possible security with food sovereignty of Mexico in the first half of the century XXI, given the impending climate change. The initial conditions include a national population growth, increasing food dependence, and a model of exploitation of natural resources extractive historically, which has led to its significant degradation. It is assumed, that agricultural technology available to the field will be obsolete within the first half of the century due to climate change, with the availability of water for crops and their genetic tolerance to drought and extreme temperatures core variables food production. The fragility of half the arable land in hillside climate change, due to its exposure to soil erosion due to lack of protection is highlighted. The urgent to resource management are discussed to correct deferred investment accumulation of protective adaptations. The research plans intermediate-term (5-10 years) and long term (20 to 40 years) is analyzed. The first to develop transition technologies and the second to develop appropriate advanced stages of climate change technology. The need is observed 1) multiobjective technologies as a MIAF for agricultural 1728 Rev. Mex. Cienc. Agríc. Vol.7 Núm. 7 28 de septiembre -11 de noviembre, 2016Antonio Turrent-Fernández et al. multiobjetivo como el MIAF para el manejo agrícola de laderas; 2) la recirculación de los germoplasmas élite de cultivos anuales dentro y entre regiones; 3) la búsqueda en tiempo real y aprovechamiento del germoplasma nativo con adaptación genética a la sequía y a temperaturas extremas; y 4) el desarrollo de perennidad en el cultivo del maíz.Palabras clave: cambio climático, seguridad con soberanía alimentaria, tecnologías adaptadas a tensi...

El golfo de California es uno de los ecosistemas marinos más productivos del planeta. Es un sistema eutrófico con una producción fitoplanctónica (PF) integrada de >1 g C m-2 día-1 y en algunos lugares >4 g C m-2 día-1 (Álvarez-Borrego y Nutrient input from the Colorado River to the northern Gulf of California is not required to maintain a productive pelagic ecosystem El aporte de nutrientes del río Colorado al norte del golfo de California no se requiere para mantener un ecosistema pelágico productivo