Producción CyT

Anais V Simposio Internacional de Climatologia - Variabilidad de temperaturas extremas en Argentina: cambios intermensuales de invierno

Congreso

Autoría:

BARRUCAND, MARIANA GRACIELA ; Rusticucci, Matilde ; Kim, Woon

Fecha:

2013

Editorial y Lugar de Edición:

SBMET

Resumen *

Studies of temperature extremes show a diminution in the number of cold nights (TN10) and an increase in the number of warm nights (TN90) over central and northern Argentina at least since 1960. Nevertheless, towards the end of autumn and early winter, TN90?s trends reverse its sign. Indeed, in July the decrease in the number of warm nights is significant for many Argentines? stations. In August, the trend returns towards positive values, with an increase in the number of warm nights and also in the number of warm days at a large extent of the country. These intra-seasonal differences are observed more strongly in the central region (CR) of the country, in a spatial domain between 30º and 40ºS and 57.5ºW and 67.5 ºW. Atmospheric circulation conditions were analyzed in order to explain the differences found in temperature extremes behavior during July and August. For both months, average fields of sea level pressure, geopotential height, zonal and meridional wind at 850 hPpa and 250 hPa were analyzed. NCEP/NCAR dataset for 1957-2008 period was used for this propose. Considering the different variables mentioned above, August-July differences and their evolution throughout five decades were specially analyzed. The 70?s and the 90?s presents the maximum differences in relation to the number of temperature extremes and the climate fields associated with them. Running means of these differences show a reverse in the sign at 1977. This result is congruent with the well-known climate shift 76/77, so TN90 values and different atmospheric variables relationship, before and after 1977 were analyzed. In July, an Indo-Pacific wave propagation before 1977 appear to be related with warm nights at CR when 850 hPa fields are analyzed, but this relation vanish after 1977. In August, wave propagation is reflected after 1977, and no clear relationship is found before. The meridional wind at 850 hPa affecting CR zone has also exhibit some changes. It can be observed a diminution (increase) of the northern wind at 850 hPa in July (August), that is congruent physically and temporarily with the changes observed in the frequency of warm nights. Información suministrada por el agente en SIGEVA

Palabras Clave

TEMPERATURE EXTREMESINTRA SEASONAL VARIABILITYARGENTINACIRCULATION CHANGES