APPENDIX A 



OBSERVATIONS ON THE CLIMATE OF SOUTH-WEST YUNNAN 



As throughout the whole of Central Asia, Yunnan has a dry season and a 

 rainy season, influenced by the N.E. and S.W. monsoons. The dry season lasts 

 from the ist or 15th of October to the 1st or 15th of May. August and Sep- 

 tember are the two wettest months ; during which swollen torrents and torn-up 

 roads often render travelling wholl)' impossible. Many routes are only to be 

 followed by caravans during the dry season, amongst which was the one taken 

 by us from Tayang-ka to Muong-le. 



But this general rule is subject to many natural modifications caused by the trend 

 of the mountain chains, altitudes, etc. In winter, for example, the valley of the 

 Red River is completely arid, as also the mountains which dominate it, to a height 

 of 3000 feet : whilst the same ranges from 3000 feet to 8000 feet are thickly 

 wooded and frequently enveloped in mists and rain. 



The direction of the wind varies, as shown in the foregoing tables. Generally 

 speaking, it blows from the south-east during the dry months, and from the west 

 in the wet. I never experienced a north wind, but was told that in the winter it 

 often blows hard from this quarter over the plain of Tali, causing wrecks upon the lake. 



In a country so mountainous as Yiinnan the climate alters much according to 

 altitude. In summer the valleys of the Red River, the Mekong, and the Salwen, the 

 plains of Muong-le, Ssumao, Yiinchou, and the portion of Yiinnan formed by the 

 basin of the Yang-tse-kiang, /.e. the lower districts from 2000 feet to 4000 feet, are 

 subject to high temperature, 91" to 100" in the daytime, and 76' to 86° at night; 

 whereas in the mountainous regions and higher plains such as those of Tali, 

 Meng-hua-ting, Chunning-fou, etc., from 4000 feet to 7000 feet, the temperature 

 remains within the extremes 53° and 82°. The climate of the plain of Tali (6929 feet) 

 is particularly bracing. 



In this part of Yunnan we met with no snow, nor did we sight it on any summits 

 save those of the Tsang Mountains on the agth May. Certainl)' we were only there 

 between February and June. The Lolos informed us that in the end of November 

 and in I )eceniber snow falls almost every year on the chain separating the Red River 

 from the Black River, but that it never lies for more than a few days at a time. The 

 Tsang Mountains are the highest in South-\\'est Yiinnan. They rise on the west 

 of the plain of Tali to an average height of 1 1,500 feet, with some peaks of 1 2,500 feet 

 and 13,000 feet, and are covered from November to April. Snow also falls ever)' 

 winter in the plain of Tali, but does not lie. 



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