intraseasonal variability of the surface fluxes in santarém pedro l. silva dias (1) pedro l. silva...
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Intraseasonal Variability of the Surface Intraseasonal Variability of the Surface Fluxes in SantarémFluxes in Santarém
Pedro L. Silva Dias (1)Pedro L. Silva Dias (1)
Maria Isabel Vitorino (1)Maria Isabel Vitorino (1)Humberto Rocha (1)Humberto Rocha (1)Michael Goulden (2)Michael Goulden (2)
Scott Miller (2)Scott Miller (2)
((1) Institute of Astronomy and Geophysics1) Institute of Astronomy and GeophysicsUniversity of São PauloUniversity of São PauloSão Paulo SP – BrazilSão Paulo SP – Brazil
(2) University of California(2) University of CaliforniaDept. of Earth System ScienceDept. of Earth System Science
Irvine CA - USAIrvine CA - USA
E-mail:E-mail: [email protected]
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 CO2 fluxes measured by the eddy correlation tower at the FLONA reserve.
IntroductionIntroduction
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 MethodologyData 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) CO2 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 16 2000 to December 16 2003 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 Winter S. 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
dta
bttf
abaf )(
1 ),)((W
2/20)( ttiw eet Morlet Function:
0 100 200 300-1
-0.5
0
0.5
1
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
2001 2002 2003 2001 2002 2003
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
ConclusionConclusion
•The atmospheric signal of the intraseasonal variability in the Santarém The atmospheric signal of the intraseasonal variability in the Santarém region is significant during some selected periods of the time series region is significant during some selected periods of the time series (specify which periods are more relevant). The analysis indicates that the (specify which periods are more relevant). The analysis indicates that the intensity of the trade winds, as measured by the zonal component of 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 wind at the 925 hPa level is particularly modulated in the intraseasonal band (much more evident than in the meridional component of the wind). band (much more evident than in the meridional component of the wind). Outgoing long wave radiation and therefore precipitation also indicate the Outgoing long wave radiation and therefore precipitation also indicate the intraseasonal modulation, in coherence with the wind field. (Is there any intraseasonal modulation, in coherence with the wind field. (Is there any preferred period of the year in which the intraseasonal signal is more preferred period of the year in which the intraseasonal signal is more evident? - specify similarities between 2000, 2001, 2002 and 2003 and the evident? - specify similarities between 2000, 2001, 2002 and 2003 and the differences…).differences…).
•The COThe CO22 fluxes do not indicate a very strong intraseasonal modulation fluxes do not indicate a very strong intraseasonal modulation
although a small signal is in the analysis throughout the period. Of 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 particular interest is the period from October 2002 to Abril 2003 when the modulation exerted by the atmospheric intraseasonal variability was modulation exerted by the atmospheric intraseasonal variability was particularly strong in the Co2 fluxes..particularly strong in the Co2 fluxes..