Guadalupe Cordero

Historical Droughts in Central Mexico and Their Relation with El Niño

A catalog containing an unprecedented amount of historical data in central Mexico, covering almost six centuries (1450–1900), is used. This is a catalog of agricultural disasters that includes events associated with hydrometeorological phenomena, or hazards, whose effects were mainly felt in the agricultural sector, such as droughts. An analysis of the historical series of droughts in central Mexico for the period of 1450–1900 is performed. Periods of frequent drought centered at the years 1483, 1533, 1571, 1601, 1650, 1691, 1730, 1783, 1818, and 1860 have been identified. In particular, droughts in Mexico City and northwest Mexico that were identified through poor tree-ring growth are included in the frequent drought periods obtained in this work. Moreover, it was found that droughts occurred in El Nino years mainly for events of very strong and strong strengths, at a significant level. Also, most droughts lasted for 1 or 2 yr. Last, by analyzing the periodicities of the drought time series it was found that those that are the most conspicuous are the quasi-bidecadal frequencies of 18.9 and 21 yr.

Wind effects on the entry of meteorites into the atmosphere of Venus

Abstract We considered the effect of the wind on the entry of meteorites into the venusian atmosphere by solving the entry equations involving a term related with the wind drag. We found that the wind affects only the entry of iron meteorites with masses less than 10 9 kg and stone meteorites with masses less than 10 11 kg. Since meteorites that produce craters on Venus have masses exceeding these limits we conclude that the effect of the wind is negligible in the processes of craterization of the surface of Venus.