Rainfall and climate variability: long-term trends in the Metropolitan Area of Sao Paulo in the 20th century

Author(s)

Obregon, Guillermo O. ^[1] ; Marengo, Jose A. ^[1] ; Nobre, Carlos A. ^[2]

Affiliation

^[1] Natl Inst Space Res CCST INPE, Ctr Earth Syst Sci, BR-12630000 Sao Paulo - Brazil

^[2] Minist Sci Technol & Innovat SEPED MCTI, BR-12227010 Brasilia, DF - Brazil

• Document type: Journal article
• Source: CLIMATE RESEARCH; v. 61, n. 2, p. 93-107, SEP 2014.
• Web of Science Citations: 5

Abstract

We investigated spatial temporal variability and long-term). trends of rainfall over the Metropolitan Area of Sao Paulo (MASP). Due to a lack of continuous and consistent rainfall observations in the MASP, a database for the spatial analysis was created from a composite of 94 stations, with daily rainfall data for 1973-1997, plus data from the University of Sao Paulo's Institute of Geophysics and Astronomy (IAG/USP) station for 1933-2011, as the base of the long-term variability analysis. It is shown that the seasonal and interannual rainfall variability result from underlying local influences and remote large-scale atmospheric dynamics. These effects appear to be more complex during the austral spring and fall seasons, and seem to determine the duration of the rainy period over the MASP. The intraseasonal (30-60 d) oscillation of rainfall does not exhibit any long-term modulation; interannual rainfall variability for 1975-1990 appears modulated by the El Nino-Southern Oscillation (ENSO) scale (2-8 yr). Nonetheless, there exists statistical evidence that the rainfall climate over the MASP had an abrupt change at the end of the 1950s, but the global climatic change that occurred in the middle of the 1970s is not evident. The progressive increase in the frequency of rainy days and total daily rainfall throughout the period of analysis are prominent factors in the trend of annual and seasonal rainfall. Furthermore, rainfall variability over the MASP may be modulated by the Southern Annular Mode (SAM), Pacific Decadal Oscillation (PDO) and ENSO at seasonal scales, altering the normal progression of the seasonal rainfall cycle, while at interannual scales, each one of these patterns drives the rainfall variability, mainly when each pattern reaches its extreme value. (AU)

• FAPESP's process: 13/50538-7 - Understanding the causes of the biases that determine the onset of the rainy season in Amazonia in climate models using GoAmazon-CHUVA measurements
• Grantee: Jose Antonio Marengo Orsini
• Support Opportunities: Regular Research Grants
• FAPESP's process: 11/51843-2 - Impact of climate extremes on ecosystems and human health in Brazil: PULSE-Brazil
• Grantee: Jose Antonio Marengo Orsini
• Support Opportunities: Regular Research Grants
• FAPESP's process: 08/58161-1 - Assessment of impacts and vulnerability to climate change in Brazil and strategies for adaptation option
• Grantee: Jose Antonio Marengo Orsini
• Support Opportunities: Research Program on Global Climate Change - Thematic Grants
• FAPESP's process: 08/57719-9 - Program on Climate Change - INCT CLIMA
• Grantee: Carlos Afonso Nobre
• Support Opportunities: Research Program on Global Climate Change - Thematic Grants