Transition of Surface Energy Budget in the Gobi Desert between Spring and Summer Seasons

Abstract

An investigation of the transition between spring and summer seasons of the surface energy budget in the Gobi desert is presented. The motivation behind this study is to determine eventually the degree to which changes in a desert system can be monitored over a short-term climate time scale (decadel) by remote means. A seasonal transition is used to evaluate the control factors involved in a variational process. The measurements incorporated in the analysis were obtained in 1984 from a specialized surface energy budget monitoring system deployed at a site in the western Gobi desert, just north of the northeastern edge of the Tibet Plateau in western Gansu province, P.R.C. The data were collected during the spring and summer periods in 1984 by a joint team of United States and Chinese scientists. Results of the analysis reveal an interesting feature of the seasonal transition which had not been expected of a midlatitude desert. That is, although radiative forcing at the surface is altered between spring and summer through the diurnal net radiation heating function, the total radiative energy integral available for heating is largely unchanged. In some sense, the partitioning of the radiative heat supply at the surface can be viewed as a principal ingredient in defining the seasonal cycle. In terms of the Gobi desert, it may well be the only important ingredient. Both similarities and differences in the spring and summer surface energy budgets arise from differences imparted to the system by an increase in the summertime atmospheric moisture content. Changes in the near-surface mixing ratio are shown to alter the effectiveness of the desert surface in absorbing radiative energy and redistributing it to the lower atmosphere through sensible and latent heat exchange.