Description of observation and data at the Lanyu atmospheric baseline station

1.	The station and its surroundings
Lanyu atmospheric baseline station is located in the Central Weather Bureau 
(CWB) meteorological station on top of a hill (348m) in the middle of Lanyu 
Island at 22°02'14''N, 121°33'29''E. To the north and south it overlooks the 
Pacific Ocean; to the east and west there are some hills. Lanyu, with five villages, 
is a small island with no more than three thousand habitants. Two predominant 
wind directions through the four seasons are the northeasterly in the winter and 
southwesterly in the summer. Under conditions of northeast wind, the wind 
usually passes over the Yehing village and then comes to the station. While under 
the influence of southwest wind, the air passes over the Fisher village and a 
diesel-engine power plant further upwind. Therefore, the influence of the two 
villages as well as the power plant may not be negligible. 
During the three months of observations at the Lanyu baseline station, the 
data quality is affected by some local activities significantly. The major 
disturbances include the followings.  1) Power outage: the exhaust pipe of the 
back-up power generator used to generate electricity is about 10 m from the 
monitoring instruments. 2) Weeding: a diesel lawnmower was used to do the 
weeding. Within the three months, they weeded twice and each time lasted about 4 
to 5 days. 3) Annual maintenance of the building: an oil paint containing toluene 
was used to repaint the building and the effects of out-gas was noticed (e.g. SO2). 
4) Biomass burning: natives usually burn their field before planting. The smoke 
plumes sometimes had large impacts on the station. Finally, cooking, tourists and 
vehicles all might have significant effects.

2.	The major instruments and their performance
Atmospheric NO-NO2-NOx, O3, SO2, CO, CO2, solar radiation (i.e. UVA, 
UVB, and TSP), and meteorological parameters (wind direction, wind speed, 
temperature and relative humidity) were observed at the monitoring station. The 
instruments for gases measurement are manufactured by the US Thermo 
Electronic Company. There were a NOx analyzer (model 42S), an SO2 analyzer 
(model 43S), an O3 analyzer (model 49), a CO analyzer (model 48), and a CO2 
analyzer. Solar radiation UVA, UVB and TSP with wavelengths of 300-380 nm, 
280-320 nm, and 0.3-3 ?m, respectively, were also observed. The meteorological 
data provided by the CWB should be better than the monitoring station because of 
better calibration and maintenance.
During the period of observation, the NO-NO2-NOx analyzer didn't function 
well because of inadequate calibration facility at the station. The performance of 
the O3 analyzer was good. The SO2 analyzer also performed well, but had a slow 
response time (usually about 10 minutes). The CO analyzer also performed well, 
but the detection limit was about 50 ppb. CO2 measurement was not part of this 
campaign. The CO2 analyzer seemed to perform normally. We list the CO2 data 
for reference.

3.	Data format
Data taken during the time period of auto calibration, manual calibration, and 
power outage have been replaced with zero. The data is divided into three 
components. The first and second components contain the same data, but have 
different formats. One is FTW****.XLS, the other FTW****.CSV. The "****" in 
both cases denotes the month and date (e.g. FTW0428.XLs is the representation of 
the data of April 28). In these two components, the 1st column is time. The 2nd 
column to 4th column are NO, NO2, and NOx (pptv), respectively. 5th to 8th 
columns are, respectively, O3 (ppbv), SO2 (pptv), CO2 (ppmv), and CO (ppbv). 
9th to 11th columns are UVA, UVB, TSP in W/m2, respectively. The four following 
columns are wind direction, wind speed, temperature and relative humidity, 
respectively. The symbol for distinguishing different columns is a comma. When 
there is no data, the cell is filled with zero. Time resolution of the data is one 
minute. The third component contains those files named TWM****.XLS. The 
"****" is again month and date. The contents are plots of time series of wind 
speed and direction (figure 1), and concentrations of air pollutants: CO, O3, SO2, 
and CO2 (Figures 2, 3, 4, and 5).