Cheng Guodong, Wang Shaoling
The high-altitude and the high-latitude permafrost have common characteristics in origin.They all are the products of exchange of heatand mass between earth crust and atmosphere, and exist in a zone with lower level of energy.The lower limit of this zone can be described byfunction as follows: H = e2·3 (bφ+a).(where: H——elevation of permafrostlower limit, φ——latitude, b, a——constant).The high-latitude permafrost may regard as a special case where the elevation of high-altitude permafrost equals to zero.The high-altitude and the high-latitude permafrost are quite different in distribution pattern yet.Thus, it appears not so reasonable to classifying the high-altitude permafrost using continuous coefficient which is suitable for high-latitude permafrost.Therefore, a method for classifying high-altitude permafrost into zones is suggested.The basic criterion for classification is the mean annual ground temperature,which reflects the vertical zonation of high-altitude permafrost quite well.Furthermore,as exemplified by the Qinghai-Xizang plateau,a scheme for classifying high-altitude permafrost into zones is suggested as follows.In this article,the formula for determining the permafrost lower limit on the Qinghai-Xizang plateau based on latitude is proposed as follows:
Y=101-1.72X
where: Y——elevation, X——latitude.Based on this, formula for classifying high-altitude permafrost on Qinghai-Xizang plateau into zones is given according to the statistical-dependence between mean annual ground temperature of permafrost and both the elevation and altitude which are measured in situ, and tentatively applied, results are satisfactory.
