Preliminary assessment of the soil moisture memory role on Southeastern South America summer circulation

LORENA FERREIRA; CELESTE SAULO; CAROLINA VERA; PAULA GONZÁLEZ

Melbourne, Australia

Conferencia; 9th International Conference on Southern Hemisphere Meteorology and Oceanography; 2009

American Meteorological Society

<!-- /* Font Definitions */ @font-face {font-family:Helvetica; panose-1:2 11 6 4 2 2 2 2 2 4; mso-font-charset:0; mso-generic-font-family:swiss; mso-font-pitch:variable; mso-font-signature:536902279 -2147483648 8 0 511 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; mso-hyphenate:none; font-size:12.0pt; mso-bidi-font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-fareast-language:AR-SA;} p.WW-Textoindependiente2, li.WW-Textoindependiente2, div.WW-Textoindependiente2 {mso-style-name:"WW-Texto independiente 2"; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; mso-hyphenate:none; font-size:12.0pt; mso-bidi-font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; color:black; mso-fareast-language:AR-SA;} @page Section1 {size:612.0pt 792.0pt; margin:72.0pt 90.0pt 72.0pt 90.0pt; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Previous works have shown that land surface characteristics –particularly soil moisture- can influence the circulation and precipitation patterns over the Amazon Basin, as well as the structure and evolution of the South American Monsoon system. Moreover, it has been recently suggested that the Pampas/Pantanal region of South America exhibits signs of land-atmosphere feedback throughout most of the year, and that the soil moisture memory over these areas is larger than that over other regions in the world. With these findings in mind, we aimed at exploring the coupling between soil moisture and regional circulation at particular phases of the South American Sea-Saw (SASS) pattern. SASS, the leading pattern of intraseasonal variability is characterized by a dipole-like structure associated with wet (dry) conditions over the South Atlantic Convergence Zone (SACZ) and dry (wet) conditions over southeastern South America (SESA). The preliminary assessment is focused in the 2002-2003 austral summer, which corresponds to the WCRP/SALLJEX field experiment, and thus has the advantage of better data coverage over the area of interest. Daily area averaged soil moisture (SM) and precipitation (PP) data over two boxes centered over continental SACZ and SESA are analyzed and combined with a detailed study of the main circulation patterns. The overall objective is to determine whether it can be documented any influence of the soil moisture memory in the strength and or the duration of the SASS. Results show that a significant relationship, between the soil moisture in both the SESA and the SACZ region and the SASS pattern, is present along almost the whole period of study. Largest persistence/memory in soil moisture is founded at SESA, in concordance with recently other author results. The soil inertia shows some degree of modulation over the precipitation and circulation pattern at summer, stressing the role of the local forcing.