INTERNATIONAL JOURNAL OF CLIMATOLOGY Int. J. Climatol. 31: 621–629 (2011) Published online 3 February 2010 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/joc.2071 The characteristics of the sensible heat and momentum transfer coefficients over the Gobi in Northwest China Qiang Zhang, a * Sheng Wang, a Michael Barlage, b Wenshou Tian c and Ronghui Huang d a Gansu Province Key laboratory of Arid Climatic Changes and disaster Reduction, Institute of Arid Meteorology, China Meteorological Administration, Lanzhou 730020, People’s Republic of China b Institute of Atmospheric Physics, University of Arizona, Tucsun, 85721, USA c The School of Environment, University of Leeds, Leeds, UK d Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, People’s Republic of China ABSTRACT: Utilizing the data of the intensive observation period (May–June 2000) of the Dunhuang land-surface process field experiment supported by the ‘Atmosphere-land Interactive Field Experiment over Arid Regions of Northwest China(NWC-ALIEX)’, the bulk momentum transfer coefficient (C d ) and the bulk sensible heat transfer coefficient (C h ) between the surface and the atmosphere over the arid Gobi Desert region are determined using three different methods. The results indicate that these coefficients, especially the means, are the same order of magnitude. The influence of the building near the observational station on the results is significant. When the building effect exists, the diurnal variation of the atmospheric bulk transfer coefficients and the bulk Richardson number are irregular. After the building effect is eliminated through analysing the wind direction, the bulk Richardson number and the range of the typical values of the bulk transfer coefficients over the Gobi are obtained. The diurnal variations of the bulk transfer coefficients are smoother than that without the building affect. The bulk transfer coefficients are larger in the daytime than in the nighttime. It is also worth noting that the variations of the bulk transfer coefficients and the bulk Richardson number are just opposite in phase, and that the bulk transfer coefficient for sensible heat flux is more related to the bulk Richardson number than that for momentum flux. The results are more reasonable than that after removing the building effect. The relation between the bulk transfer coefficients is also discussed. Copyright  2010 Royal Meteorological Society KEY WORDS Gobi; bulk transfer coefficient; bulk Richardson number; building effect Received 9 June 2006; Revised 28 October 2008; Accepted 21 November 2009 1. Introduction The momentum and heat transfer over land surfaces not only have notable implications for global climate change, but also are a key part of physical processes in atmospheric numerical models on various scales. At present, the land-surface fluxes in macro-scale models are obtained through the bulk transfer method, which requires the determination of bulk transfer coefficients (Stull, 1988). However, the bulk transfer coefficients used in most numerical models are not accurate. In arid regions, the bulk transfer coefficients on grid points in macro-scale models are not accurately provided due to a shortage of observations. The bulk transfer coefficients vary not only with different regions, but also with dif- ferent times (Stull, 1988). Because of various reasons such as deriving methods and the observational prob- lems, the estimated bulk transfer coefficients are often quite different even in the same region (Ye et al., 1979; Li et al., 2000; Zhao et al., 2000). * Correspondence to: Qiang Zhang, Institute of Arid Meteorology, China Meteorological Administration, No. 2070, Donggang East Road, Lanzhou, 730020, People’s Republic of China. E-mail: Zhanggiang@cma.gov.ca The error in bulk transfer coefficients will cause pro- portional errors in surface fluxes and atmospheric models are then sensitive to these errors. Therefore, more accu- rate bulk transfer coefficients are necessary. The arid region of Northwest China, where an important surface feature is the Gobi (or desert), is very broad. The inte- grated contribution of its land-surface fluxes may have an effect not only on global climate change, but also on the East Asia monsoon circulation and the formation of the arid climate in Northwest China. Therefore, the obser- vational study on the bulk transfer coefficients over the Gobi in Northwest China arid region is important both theoretically and practically. From 1988 to 1992, a land-surface process field exper- iment in the arid region – Atmosphere-Land Surface Pro- cess Experiment at Heihe River Basin – was carried out in Gansu province in Northwest China by scientists from China and Japan(Gao, 1990). The results already obtained have improved our understanding and recognition on the land-surface process over the arid region (Wang et al., 1991; Hu et al., 1992, 1994; Zhang et al., 1999). The primary attention of the experiment has been on the description of characteristics of land-surface processes Copyright  2010 Royal Meteorological Society