Patrick Essien(1), I. Paulino(2), C. M. Wrasse(1), J. A. V. - - PowerPoint PPT Presentation

Patrick Essien(1), I. Paulino(2), C. M. Wrasse(1), J. A. V. Campos(2), A. R. Paulino(2), A. F. Medeiros(2), R. A. Buriti(2), H. Takahashi(1), E. Agyei-Yeboah(2), D. Barros(1), C. A. O. B. Figueiredo(1), and A. N. Lins(2) (1) Instituto Nacional de Pesquisas Espaciais (INPE) (2) Universidade Federal de Campina Grande

OUTLINE

Introduction

• Objectives

Image Analysis Results & Discussion  Summary

Objectives

• Seasonal characteristics of SSGWs and MSGWs in the MLT region over Brazilian equatorial

region for the first time.

• Apply the critical level theory to study the effects of wind filtering on SSGWs and

MSGWs propagation directions in the middle atmosphere.

• The possible wave source region in the troposphere

Raw Image

The linearized and rotated image ready for the FFT analysis

The image after the stars have been removed

Image Analysis

(a) (b (c).

Estimation of parameters of SSGWs using 2D spectrum OH Cariri

• Feb. 25-26, 2001

OH, Cariri, Feb. 25-26, 2001

Keogram

Results

The yearly distribution of the SSGWs, MSGWs events, clear sky, cloudy and observed nights

The average monthly distribution of the SSGWs, MSGWs events, clear sky nights, cloudy nights and observed nights

SSGWs MSGWs

• Filtering process by the background wind
• Location of the wave source region

There are two main factors which could create the observed anisotropy of AGWs propagation (Fritts et al., 2008). OH

• Using HWM-07 as the parameter for

the background wind

• The Outgoing Longwave Radiation

(OLR) data was obtained from the National Oceanic and Atmospheric Administration (NOAA) to localize the deep convective regions

Critical Layer

• This situation may occur at any height level when the local horizontal wind speed

along the direction of propagation equals the observed horizontal phase speed of the gravity wave (Taylor et al. 1993)

• Following the analysis by Booker and Bretherton (1967), and ignoring the terms

involving isothermal scale height, etc in Taylor-Goldstein equation

• The Doppler-shifted frequency, Ω, due to the horizontal wind Vo is given by

Doppler shifted

Source Frequency horizontal wave vector

• Component of horizontal wind along vx
• where vx is the observed horizontal phase speed of the

wave

• the critical layer when Vox= vx
• where Vz and Vm are the zonal and the meridionawl wind components

2000 2001

2004 2007

2006 2009

Oct-12-2009 Oct-13-2009 Oct-17-2009 Oct-16-2009 Oct-15-2009 Oct-14-2009

Nov-09-2009 Nov-12-2009 Nov-19-2009

Summary

• Eleven years of AGWs observations were made from NIR-OH emissions using an all-

sky airglow imager at Cariri .

• The measurements were made from September 2000 to December 2010, with a total of

1252 nights of clear sky.

• In summer, fall and winter both SSGWs and MSGWs propagated preferentially

northeastward and southeastward, while in spring the waves propagated in all directions.

• The horizontal propagation directions of SSGWs and MSGWs show clear seasonal

variations based on the influence of the wind filtering process and wave source location

THANK YOU