V. M. Mendoza

Numerical experiments on the prediction of sea surface temperature anomalies in the Gulf of Mexico

Abstract The conservation of thermal energy equation applied to the mixed layer of the ocean, has been used to predict the sea surface temperature anomalies (SSTA) and the month-to-month changes in the Gulf of Mexico. The model includes the horizontal transport of heat by mean ocean currents and by turbulent eddies, as well as the heating by short and long wave radiation, evaporation and sensible heat given off to the atmosphere. A comparative study is carried out on the relative importance of the heating and transport terms. An objective verification of the skill of the predictions is presented for each season and for the whole period from March 1986 to February 1987. The predictions using only the heating terms have some skill over the control predictions (persistence and return to normal). The skill is substantially increased when the horizontal transport of heat by turbulent mixing is included in the model. The incorporation in the model of the Ekman wind drift current anomalies computed from the anomalous surface geostrophic wind improves appreciably the skill of the predictions in winter and fall. The mixed layer depth computed using the Kraus and Turner theory with dissipation, shows that the depths in summer and fall are shallower than in spring and winter. The effect of the shallow mixed layer depth in the model becomes apparent in summer and fall, improving the skill of the predictions in these seasons, with respect to the skill obtained using a constant mixed layer depth of 60 m. The incorporation in the model of the cooling in the mixed layer by turbulent entrainment of colder water from the thermocline, does not improve in an appreciable way the average skill of the predictions.

Monthly and seasonal prediction of sea surface temperature anomalies in the Gulf of Mexico

Abstract A thermodynamic model is used to predict the sea surface temperature (SST) anomalies in the Gulf of Mexico for extended periods as long as 3 months and for seasonal prediction. The basic equation of the model is the thermodynamic energy equation applied to the upper mixed layer of the ocean, which includes the horizontal transport of heat by mean ocean currents and by eddy turbulence, as well as heating by short and long-wave radiation, evaporation and sensible heat given off to the atmosphere. An objective verification of the skill of the predictions is presented for the period from March 1986 to February 1987. As an initial condition for the first month of the prediction we used the observed SST anomalies in the previous month, and for the second and third month we used the predicted monthly value in the previous corresponding month. Regarding the atmospheric interaction, the results show that the initial atmospheric forcing, which consists of the observed anomalies of surface air temperature and the surface wind in the month previous to the first month of the prediction, plays an important role in the prediction. The skill of the model is increased in the semi-prediction where we use, as atmospheric forcing, the surface air temperature anomalies and the surface wind anomalies for the current month instead of those belonging at the previous month to the first month of prediction. This result suggests that a coupled model in which were predicted simultaneously the ocean temperature and the atmospheric variables would improve the predictions of the SST anomalies.

Mexico's contribution to global radiative forcing by major anthropogenic greenhouse gases: CO2, CH4 and N2O

The IPCC (2013) gives simplified formulas to compute the radiative forcing (RF) resulting from the increase in anthropogenic greenhouse gases (AGG): carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide (N 2 O) and halocarbons. These formulas allow to compute the global RF of these gases relative to their pre-industrial (1750 A.D.) concentrations, and are used in this work to estimate the contribution of Mexico to the global RF by its emissions of CO 2 (the most significant of the AGG), CH 4 and N 2 O during the period 1990-2011, which are reported in the Inventario Nacional de Emisiones de Gases de Efecto Invernadero (National Inventory of Greenhouse Gases Emissions, INEGEI) (INECC, 2013). In comparison, by 2010 the national emissions per capita of Argentina, Spain and the United States were 108.8, 110.8 and 327.0% of the Mexican emissions, respectively, in units of equivalent CO 2 . Mexico’s CO 2 emissions retained in the atmosphere during 1990-2011 amount to 4 624 457 Gg; they are higher than those of Spain and Argentina together, and represent 1/12 of the USA contribution. Mexico’s contribution is 1.47% of the global RF due to CO 2 , with a similar proportion than Spain and Argentina, but a smaller fraction compared to that of the USA (1/15). The main uncertainties of our computations for Mexico’s contribution to the global RF come from national emissions; the INEGEI indicates that the emissions considered for the calculation of uncertainties represent 89% of the total emissions of the inventory, resulting in a total uncertainty of ±5.6%. We are aware that, as a consequence, the concentration increase of CH 4 and N 2 O due to Mexico’s emissions retained in the atmosphere during 1990-2011 is lower than their respective uncertainties for global concentrations: 1.72 vs. 2 ppbv and 0.13 vs. 1 ppbv.