Impact of land-use changes on the climate of the Mexico City Region

It is well established that anthropogenic land-use changes directly affect the atmospheric boundary layer at the mesoscale dimensions. Located in the high lands of Central Mexico, the basin of Mexico (7 500 km2) has undergone a widespread conversion of natural vegetation to urban and agricultural land by deforestation. While the urban extension of the capital city occupied 6% of the basin in 1960, at the end of the twentieth century the urban sprawl had increased considerably to 20% of the total area. This phenomenal growth has impacted on the thermal climate of substantial portions of the basin. In this paper using annual temperature and precipitation data for a 25 year period, an attempt is made to identify interdecadal climate changes. Results show that large areas of the basin have changed toward a warmer drier climate. While afternoon temperatures have increased at a rate of 0.07° C/yr in the suburbs of the city the corresponding area averaged value for the rural sites is somewhat less: 0.06° C/yr. The afternoon temperature increase for the total number of stations used was 0.06° C/yr. The area-averaged minimum temperature increase in suburban stations (3) was 0.15° C/yr while that corresponding to surrounding rural sites was 0.08° C/yr for period 1961-1985. This last result illustrates the relevant role the heat island phenomenon has had in changing the thermal climate as compared with that observed in the rural environment.