Abstract:
This investigation analyzed the dynamic interplay of elevation with temperature
(TMP), rainfall (PPT), and relative humidity (RH) on the mountains of north Thailand by
using daily/weekly/monthly/seasonal climate data from 12 stations. The selected data
covers the common period from 1954 to 2002, and are from the following locations:
Chiang Mai, Chiang Rai, Lampang, Mae Hong Son, Mae Sariang, Mae Sot, Nan,
Phetchaboon, Phrae, Phitsanulok, Tak, and Uttaradit. A detailed analysis of the existing
meteorological records is augmented by more than a year of direct measurements along an
elevational transect in the Chiang Dao Wildlife Sanctuary for comparison. The weather
data were complied and processed on the DPL program (Dendrochronology Program
Library), MET (Estimate Missing meteorological data), HOM (Homogeneity of
meteorological data), MAT (Correlation Matrices), and SEA (Seasonalize meteorological
data) routine were used in this study.
Preliminary analyses demonstrate that simple lapse rate models can be used to
determine the mean elevation at which dew point is reached in the mountains of North
Thailand for comparison with a network of pine chronologies from above 800 meters.
A simple homogeneity test was run for the 12 stations subset for monthly mean
TMP, RH, and monthly PPT. Results show all of the PPT stations data passed the
homogeneity test. Conversely, most of TMP data failed, even when those same stations
passed the test for both PPT and RH.
From the correlation matrix test the highest correlations for TMP are in December
(0.8056), for PPT it is in January (0.6466), and for RH the month of May shows the
highest correlation (0.7305). Substantial differences in elevation and geography for many
of these station locations have an effect on the correlations.
The relationship between the results of the tests for homogeneity and correlation
indicate that TMP and PPT are more regionally coherent than RH which shows far less
tendency toward homogeneity, and less regional agreement.
From SEA we could plot the seasonal trends through time for all stations for TMP,
PPT and RH. The trend in mean for all station data are mostly the same, though some
notable differences can be seen in some years and stations.
The year 1977 was particularly anomalous, with data from Tak exhibiting changes
in mean for PPT and RH, while Chiang Mai shows a marked change in mean for TMP.