A.M. Córdova 1, Melitta Fiebig-Wittmaack1,2,3, J. Quintana4, L. Valle 4 and G. Torres 4

 1.Centro de Estudios Avanzados en Zonas Áridas (CEAZA) , Benavente 980, Casilla 599, La Serena, Chile. acordova@inia.cl2. Departamento de Matemática, Universidad de La Serena, Chile.3. Centro de Investigación Atmosférica , La Serena (CIALS), Chile4. Dirección Meteorológica de Chile  

INTRODUCTIONINTRODUCTIONSeveral chemical and dynamical processes regulate surface ozone (O3) concentrations. Measurements of ultraviolet spectral irradiance, tropospheric ozone and meteorological parameters (temperature, wind speed and direction, relative humidity, etc) have been performed simultaneously at Cerro Tololo (CT) (30º 10´S, 70º 48´O, 2200 m.a.s.l.) by the Chilean Weather Office as part of the Global Atmospheric Watch (GAW) program of the World Meteorological Organization (WMO) since November 1995.

  

RESULTS AND DISCUSSION

The ozone concentrations ranged from 11 ppb to 60 ppb. Results showed that O3 concentrations measured during summer (DJF) were lower than spring season (SON) at Cerro Tololo.

The average ozone concentrations do not show significant diurnal cycle at this site. The ozone concentrations during summer and autumn are 27 ppb (SD 5.2 ppb). The increase of ozone concentrations are observed during of month of spring (SON) with the maximum concentration of 60 ppb. The maximum solar radiation decrease from 1100 Wm-2 in summer (DJF) to 620 Wm-2 in winter (JJA).

Ozone concentrations do not show a positive correlation with solar and UV-B radiation. This indicates that in situ photochemical production is not the driving process at this site. In fact that, previous work suggest that synoptical features linked with stratosphere-troposphere exchange play a significant role in explaining the spring maximum and the sudden increases in ozone mixing ratios observed at Cerro Tololo. The index UV is higher than 11 (exposure category = extreme) from November to February.

Ozone concentrations do not show correlations with wind speed and wind direction at surface. The wind direction is principally from Northeast during all year.

A inspection of the data do not shows temporal trends and ENOS do not influence significantly the ozone concentrations at this site. On the other hand, no significant change of O3 was observed in association to the El Niño 1997 and La Niña 1998.

AcknowledgementsAcknowledgements : : Dirección Meteorólogica de Chile (DMC), Chilean Research Council (CONICYT-FONDECYT 1030809).

CLIMATOLOGICAL ANALYSIS OF OZONE AND RADIATION MEASUREMENTS AT A BACKGROUND SITE IN THE SOUTHERN HEMISPHERE SUBTROPICS: Cerro Tololo 30ºS,70ºW, 2200 m.a.s.l.

Cerro Tololo

Monthly Precipitation November 1995- July 2004 Cerro Tololo

year average 1959-2003= 80,2 mm

020406080

100120140160180

Nov

-95

Feb-

96M

ay-9

6A

go-9

6N

ov-9

6Fe

b-97

May

-97

Ago

-97

Nov

-97

Feb-

98M

ay-9

8A

go-9

8N

ov-9

8Fe

b-99

May

-99

Ago

-99

Nov

-99

Feb-

00M

ay-0

0A

go-0

0N

ov-0

0Fe

b-01

May

-01

Ago

-01

Nov

-01

Feb-

02M

ay-0

2A

go-0

2N

ov-0

2Fe

b-03

May

-03

Ago

-03

Nov

-03

Feb-

04M

ay-0

4

prec

ipita

tion

(mm

) El Niño La Niña

Ozone Concentration Anomaly 1997 and 1998

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

JAN

FEB

MA

R

AP

R

MAY

JUN

JUL

AU

G

SE

T

OC

T

NO

V

DE

C

O3 c

once

ntra

tion

Ano

mal

y 19971998

Monthly Average Ozone 1995-2004 - Cerro Tololo

0

10

20

30

40

50

JAN

FEB

MA

R

AP

R

MAY JU

N

JUL

AU

G

SE

T

OC

T

NO

V

DE

C

O3 (

ppb)MEAN DIURNAL CYCLE - OZONE 1995-2004

0

10

20

30

40

50

0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00 0:00Local Time

O3 (

ppb)

summer (DJF)autumm (MAM)winter (JJA)spring (SON)

MEAN DIURNAL CYCLE - WIND SPEED 1995-2004

0

1

2

3

4

5

6

0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00 0:00Local Time

win

d sp

eed

(m s

-1)

summer (DJF) autumm (MAM)winter (JJA)spring (SON)

MEAN DIURNAL CYCLE - SOLAR RADIATION 1995-2004

0

200

400

600

800

1000

1200

0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00 0:00Local Time

SO

LAR

RA

DIA

TIO

N (W

m-2

) summer (DJF)autumm (MAM)winter (JJA)spring (SON)

Frecuency of wind direction at Cerro Tololo

Monthly Average UV Index 1995-2004 - Cerro Tololo

0

2

4

6

8

10

12

14

16

JAN

FEB

MA

R

AP

R

MAY

JUN

JUL

AU

G

SE

T

OC

T

NO

V

DE

C

UV

Inde

x