Simulation of the PDO effect on the North America summer climate with emphasis on Mexico

Five composite anomaly fields (CAF) are built for the summer of each Pacific decadal oscillation (PDO) phase: skin temperature; air temperature (T7), zonal (u7) and meridional (v7) wind at the 700 mb level; and precipitation (R). rgy balance model, named thermodynamic climate model (TCM), is integrated on the NH to compute the summer anomalies (sub-index A) of the land surface temperature (LST),T7, u7, v7, R and cloudiness (ε). To study the effect of the PDO phases on Mexicoʹs climate, the CAF of the sea surface temperature (SST) is used in the TCM as an input. The output fields are objectively compared with their respective CAF (except SSTA) using an index of agreement, and the six variables are mainly discussed on the north Pacific and adjacent continents (NPAC), with emphasis on Mexico. M generates a kind of atmospheric bridge by which the SSTA produces a T7A, the consequent condensation of water vapour anomaly and the corresponding εA over the continent, affecting the planetary albedo and therefore the LST. A forms a large meridional wave train over the NPAC centre, which is part of the Pacific/North American pattern in both PDO phases and is more intense in winter than in summer. In the PDO warm phase and over the eastern half of the NPAC, the v7A is positive, so that the moisture flux from the Pacific Ocean toward North America (NA) increases the precipitation during NA monsoons. These results have an acceptable agreement with the CAF. o analysed the combined effect of cloudiness and evaporation according to the soil moisture, over the eastern NA and the Gobi Desert for both PDO phases, showing its thermal moderator effect.