Intraseasonal Variability of the Surface Fluxes in Santarém Pedro L. Silva Dias (1) Pedro L. Silva Dias (1) Maria Isabel Vitorino (1) Humberto Rocha (1) Michael Goulden (2) Scott Miller (2) (1) Institute of Astronomy and Geophysics University of São Paulo São Paulo SP – Brazil (2) University of California Dept. of Earth System Science Irvine CA - USA

The main objective in this report is to: (a) identify the intraseasonal signal in the atmosphere in the Santarém (western region the Pará state in Brazil) and (b) explore the possible impact of the intraseasonal variability in the CO 2 fluxes measured by the eddy correlation tower at the FLONA reserve.Introduction Observational studies on the tropical intraseasonal variability (Madden e Julian, 1971,1972; Weickmann et al., 1985; Kayano e Kousky, 1994; Vitorino, 2003) have indicated a significant signal in the precipitation, wind and moisture fields.

Data and Methodology The following meteorological data were used in this report: (a) mean daily values of the zonal and meridional component of the wind obtained from the NCEP reanalysis at 925 hPa; (b) Outgoing long wave radiation at the top of the atmosphere, obtained from satellite measurements (a proxy of precipitation); (c) CO 2 fluxes at 30 min intervals at the top of the 64 m tower located at km 83 of the Cuiabá –Santarém highway and (d) precipitation at the same tower location. The flux tower data covers the period June to December and have been described by (Rocha et al., 2003). The high frequency tower data was averaged in order to obtain mean daily values.

Marton, 2000 Intrasazonal Oscillation Wind at 200 hPa and Outgoing Long Wave Radiation Anomaly (related to precipitation) 28 days

SA Prevailing modes at 15S – 25S OLR Anomaly 45 days 40 days

Satellite + raingage precipitation estimate 10N – 10S Mean S. Hemisphere WinterS. Hemisphere Summer

The wavelet analysis (WA) described by Daubechies (1992) is used in order to identify the spectra, in view of the possible lack of stationarity of the signal Wavelet transform of the wind field at 850 hPa Morlet Function:

Alta da Bolívia

WETAMC 1999 Vitorino & P. Silva Dias 2004

WETAMC 1999 Vitorino & P. Silva Dias 2004

Dry to Wet 2002 Vitorino & P. Silva Dias 2004

Dry to Wet 2002 Vitorino & P. Silva Dias 2004

WETAMC 1999 Dry to Wet 2002 Vitorino & P. Silva Dias 2004

WETAMC 1999 D2W 2002 Vitorino & P. Silva Dias 2004

Original Time Series of CO2 Real part of the Wavelet spectra Santarém - PA

Wavelet Spectra NCEP Reanalysis and OLR Santarém

Wavelet Spectra CO2 Flux Santarém

Wavelet Spectra CO2 Flux Santarém

Santarém - PA Real part of the Wavelet spectra Original Time Series of Zonal Wind at 925 hPa

Santarém - PA Original Time Series of OLR Real part of the Wavelet spectra

Conclusion Conclusion The atmospheric signal of the intraseasonal variability in the Santarém region is significant during some selected periods of the time series (specify which periods are more relevant). The analysis indicates that the intensity of the trade winds, as measured by the zonal component of the wind at the 925 hPa level is particularly modulated in the intraseasonal band (much more evident than in the meridional component of the wind). Outgoing long wave radiation and therefore precipitation also indicate the intraseasonal modulation, in coherence with the wind field. (Is there any preferred period of the year in which the intraseasonal signal is more evident? - specify similarities between 2000, 2001, 2002 and 2003 and the differences…).The atmospheric signal of the intraseasonal variability in the Santarém region is significant during some selected periods of the time series (specify which periods are more relevant). The analysis indicates that the intensity of the trade winds, as measured by the zonal component of the wind at the 925 hPa level is particularly modulated in the intraseasonal band (much more evident than in the meridional component of the wind). Outgoing long wave radiation and therefore precipitation also indicate the intraseasonal modulation, in coherence with the wind field. (Is there any preferred period of the year in which the intraseasonal signal is more evident? - specify similarities between 2000, 2001, 2002 and 2003 and the differences…). The CO 2 fluxes do not indicate a very strong intraseasonal modulation although a small signal is in the analysis throughout the period. Of particular interest is the period from October 2002 to Abril 2003 when the modulation exerted by the atmospheric intraseasonal variability was particularly strong in the Co2 fluxes..The CO 2 fluxes do not indicate a very strong intraseasonal modulation although a small signal is in the analysis throughout the period. Of particular interest is the period from October 2002 to Abril 2003 when the modulation exerted by the atmospheric intraseasonal variability was particularly strong in the Co2 fluxes..