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Ambient atmospheric CO at Jaduguda was measured continuously from 8^th to 31^st December 2004 as part of a campaign organized by the Indian Space Research Organization (ISRO) under the ISRO-Geosphere Biosphere Programme. Fig. 2 depicts the average diurnal CO pattern for the entire campaign period (December 9-31, 2004) observed at Jaduguda. It shows two distinct peaks, one in the morning (~08:00 h, IST) and the other in the late evening (~20:00 h, IST). Average CO observed during measurement period was 425 ppb. Since open mines function as storage for stagnant air that trap CO from the mines, the high background CO in ambient air could be due to the operation of open mines.

Fig. 2. 
Average diurnal CO pattern at Jaduguda from 9-31 December 2004.

Temporal variations of CO for the campaign period show high CO mixing ratio during 26 December 2004 - the Tsunami day. Fig. 3 shows CO mixing ratio for a period of four days from 24^th to 27^th December 2004. Each point in Fig. 3 represents the CO value at 15-minute intervals as measured by the CO analyzer. A horizontal arrow in Fig. 3 represents the Tsunami day. The Tsunami waves hit the eastern coastal areas of India at around 09:00 h on December 26, 2004. From Fig. 3, it has been seen that, ambient CO at Jaduguda showed a very high mixing ratio on 26^th December, in fact, the highest during the campaign period. CO levels went up to 2,271 ppb on the Tsunami day. Diurnal average CO mixing ratio over Jaduguda on the Tsunami day is found to be 707 ppb, which is ~2.2 times more than that of the normal days (325 ppb). A similar high in CO mixing ratio of slightly lesser magnitude is also found prior to the Tsunami, evening of the previous day (25 December 2004). A sudden increase in CO mixing ratio started at around 16:45 h on 25 December 2004 and attained a maximum of 1,674 ppb at around 18:30 h and it gradually decreased to 892 ppb at around 23:45 h. There after it started going high and continued to be high till the early morning hours (04:45 h) of the next day, 26 December 2004. CO mixing ratio is observed to be low from 04:45 h to 06:15 h on 26 December 2004 (Tsunami day), started increasing at around 06:30 h and it went high till 10:00 h with the highest value (2,271 ppb) at around 09:30 h. A low CO mixing ratio was observed after 10:00 h and continued to be low till 18:00 h, again it went high till the next day morning.

Fig. 3. 
CO variations at Jaduguda from 24-27 December 2004.

Fig. 4 shows CO diurnal pattern on the Tsunami day and average diurnal CO on normal days in December 2004. A very low CO mixing ratio can be seen during the morning hours on normal days. While from Fig. 3, it can be seen that CO mixing ratio during the morning hours as well as the morning peak on Tsunami day are very high compared to normal days. CO morning peak on a normal day is found to be ~937 ppb at around 08:30 h but on Tsunami day it is seen to be 2,271 ppb at around 09:30 h. Diurnal CO pattern on normal days shows low CO mixing ratio during the noon hours (12:30 h to 14:30 h). A low CO mixing ratio can also be seen from 17:00 to 19:15 h in the evening. High power diesel engines used for mining and transportation of raw materials at the mining site caused variations in diurnal CO. The observed lows in CO mixing ratio from 12:30 h to 14:30 h could be due to the break in operating time of mining activities. Earlier studies at the same mining site (Mohan Kumar et al., 2008) also reported that CO mixing ratio at this site depended on the operations of the mines. From Fig. 4 it can be seen that, on the Tsunami day, CO mixing ratio is very low from 10:00 h till the next day morning compared to normal days. Unlike normal days, diurnal CO pattern on the Tsunami day shows frequent highs and lows in CO mixing ratio during the night hours.

Fig. 4. 
CO diurnal pattern on Tsunami day and on normal days (average CO) in December 2004.

Fig. 5 depicts the back trajectory analysis over Jaduguda at shorter intervals (6 h) from 24 December 2004 to 27 December 2004. It shows vertical atmospheric circulations from high altitude to surface (<500m AGL) over Jaduguda. Strong vertical air movements from high altitudes can be seen on 25 December 2004 and on 26 December 2004. The vertical mixing of air started at around ~16:30 h on 25 December 2004 and it continued till around 17:30 h on 26 December 2004. A very high vertical mixing of air can be seen at around ~08:30 h to 10:30 h IST (03:00 to 05:00 UTC) on 26 December 2004. Ground-based CO measurements from the analyzer on 26 December 2004 shows a high CO mixing ratio from 08:30 h to 10:00 h, the time in which high vertical mixing occurred over Jaduguda. The high CO observed from 16:45 h on 25 December 2004 also coincides with the occurrence of vertical air mixing on the same day. The back trajectory analysis shown in Fig. 5 also shows the horizontal wind pattern over Jaduguda from 25 December 2004 to 27 December 2004. The horizontal wind pattern makes it clear that the winds coming from the north-west (NW) direction of Jaduguda causes transport of high CO from highly polluted regions situated NW of the measurement site. Fig. 6(a) depicts the back trajectory analysis at 500 m, 1,500 m and 2,500 m AGL over Jaduguda from 24 December 2004 to 31 December 2004. Back trajectory analysis on normal days in December 2008 is shown in Fig. 6(b). It can be seen that the horizontal as well the vertical wind patterns over Jaduguda on normal days (Fig. 6(b)) and on the Tsunami day (Fig. 6(a)) are significantly different.

Fig. 5. 
Back trajectory analysis over Jaduguda from 24-27 December 2004.

Fig. 6. 
(a) Back trajectory analysis over Jaduguda from 24-31 December 2004. (b) Back trajectory analysis over Jaduguda on normal days (24-28 December 2008).

As the Tsunami waves hit the west coast of India, in this study we have included the measurements of CO at a coastal station, Thiruvananthapuram, which is situated at the west coast of India. Such a measurement will help us to know the variation in CO associated with the changes in atmospheric conditions during the natural hazards like the Tsunami. Ground-based measurements of CO over at Thiruvananthapuram have been carried out continuously since 2003 using a non-dispersive IR analyzer, Monitor Europe Model 9830 B. The same analyzer was used for CO measurements at Jaduguda in December 2004. Due to the deployment of the instrument at Jaduguda, ambient CO measurements over Thiruvananthapuram in December 2004 were not possible. For monitoring the variations in CO mixing ratio over Thiruvananthapuram during the Tsunami 2004, we have used the satellite measurements of CO retrieved from MOPITT. Satellite CO data show high CO mixing ratio over Thiruvananthapuram on the Tsunami day (26 December 2004). It shows a high CO mixing ratio of ~225 ppb at 1,000 mb(surface) over Thiruvananthapuram on the Tsunami day compared to normal days in December (~200 ppb using satellite measurements, ~195 ppb using groundbased measurements). Earlier studies (Okada et al., 2004; Gupta et al., 2002) reported release of gases and oozing of water prior to the earthquake event. This supports the enhancement of CO and also changes in atmospheric parameters. Such an enhancement in CO mixing ratio is also seen at high altitudes in the troposphere on the Tsunami day.

CO mixing ratio at different altitudes (1,000-100 mb pressure levels) in the troposphere on the Tsunami day (26 December 2004), a day before the Tsunami (21 December 2004) and a day after the Tsunami (December 30, 2004) are shown in Fig. 7(a). A sudden increase in CO concentrations on the Tsunami day is also observed at 900, 800 and 700, 600 and 500 mb pressure levels compared to a normal day before the Tsunami (December 21, 2004). But on normal days, enhancement in surface CO causes enhancements in CO only up to 700 mb pressure level (~3 km altitude) on the same day. Even in summer, in which high boundary layer causes faster dispersion of pollutants to high altitude, transport of CO from 700 to 400 mb in the troposphere over Thiruvananthapuram takes more than a week. The gaseous pollutants like CO takes more time in winter than that in summer to get transported to high altitudes in the troposphere due to low boundary layer height in winter. On the contrary, dispersion of CO from 1,000 to 400 mb on the Tsunami day took only less than 12 h. Vertical mixing of air in the troposphere due to strong vertical circulations associated with the Tsunami could be the possible reason for this. From Fig. 7(a), it can be seen that CO mixing ratio from 300 to 100 mb is high on 28^th December 2004 compared to the Tsunami day. It shows that high CO at 400 mb altitude takes only 2 days to get transported to 100 mb. But, even in summer, it needs nearly one week to get transported the gaseous pollutants like CO from 400 to 100 mb (Fig. 6(b)). Only very strong vertical circulations can cause such fast and strong vertical dispersion of pollutants to high altitudes in the troposphere.

Fig. 7. 
(a) CO mixing ratio at different altitudes (1,000-100 mb pressure levels) in the troposphere over Thiruvananthapuram from 26-30 December 2004. (b) CO mixing ratio at different altitudes (1,000-100 mb pressure levels) in the troposphere over Thiruvananthapuram during a summer month (1-17 May 2008).

Fig. 8(a) depicts the back trajectory analysis over Thiruvananthapuram from 21^st December 2004 to 31^st December 2004. Strong vertical circulations over Thiruvananthapuram on the previous day of the Tsunami (25 December 2004) can be seen from Fig. 8(a). Vertical mixing of air over Thiruvananthapuram at ~17:30 h on 25 December 2004 is seen from Fig. 8 (a). It shows that the winds from high altitudes (>6 km) in the troposphere converged at ~3 km height. Convergence of high altitude winds causes a high degree of vertical mixing of air in the troposphere. Fig. 8(a) also shows the horizontal winds blown from the Bay of Bengal area. The strong horizontal as well as the vertical circulations along with the convergence in the lower troposphere causes accumulation of high CO at the surface over Thiruvananthapuram. Fig. 8(b) shows the back trajectory analysis from 24^th December 2004 to 27^th December 2004 over Thiruvananthapuram. Vertical mixing of air over Thiruvananthapuram on 25^th December 2004 can be seen from Fig. 8(b). The back trajectory analysis over Thiruvananthapuram during the normal days in December 2008 is shown in Fig. 8(c). It can be seen that the back trajectory analysis during the days near to the Tsunami in December 2004 is significantly different from that of the normal days during December in the successive year (December 2005).

Fig. 8. 
(a) Back trajectory analysis over Thiruvananthapuram from 21-31 December 2004. (b) Back trajectory analysis over Thiruvananthapuram from 24-27 December 2004. (c) Back trajectory analysis over Thiruvananthapuram on normal days (24-28 Dec 2005).