In order to make a further understand of the difference and representativeness between gridded merging real-time product

and observed data, the paper evaluated and corrected the CLDAS 2 m temperature merging product based on the observational data of automatic stations in Lanzhou and Wuwei region. The results are as follows: (1) The hourly temperature and daily minimum temperature products are lower than observations, and these errors decrease with the altitude going up below 2 500 m. The mean error of the daily maximum temperature product is negative around the altitude of 1 500 m, and changes to positive values above 1 500 m, then the positive mean error increases with the increase of altitude. The errors of daily maximum and minimum temperature are larger than those of hourly temperature, but their mean errors are all within 2 ℃. (2) The near gridding validation further shows that the diurnal change of

CLDAS hourly temperature is generally similar to observations in the daytime, while it is relatively 0.2 ℃ lower than observations at night. The daily average temperature of CLDAS merging product is generally lower about 1 ℃, and the negative deviation in Lanzhou urban area is relatively small. Spatial distribution of high temperature days above 30 ℃ of merging products is basically consistent with observations, but there are more actual high temperature days in Lanzhou urban area. (3) Both the linear regression and the decaying averaging method have a certain correction effect on CLDAS temperature merging products, and the latter has a better correction effect. The correction effect becomes better with the altitude increasing. To sum up, the CDLAS temperature merging products can better reflect the characteristics of actual temperature change in Lanzhou and Wuwei region, but its ability to reflect the daily maximum and minimum temperature is not as good as the hourly temperature, and the error is relatively large in complex terrain.

为更好地理解格点融合实况数据与观测数据的差异和代表性，利用甘肃兰州和武威两地站点

的观测数据对中国气象局陆面数据同化系统（CMA Land Data Assimilation System，CLDAS）地面2 m气

温融合产品进行检验评估及偏差订正。结果表明：（1）逐小时气温和日最低气温融合产品的平均误差

总体为负值，较实际气温偏低，且在2 500 m以下误差随海拔上升而减小；日最高气温融合产品平均误

差在海拔1 500 m附近为负值，1 500 m以上误差变为正值且随海拔升高而增大；日最高和最低气温误

差较逐小时气温误差偏大，但平均误差均在2 ℃以内。（2）通过近网格点检验，发现逐小时CLDAS气温

产品白天与实况相近，夜间较实况偏低0.2 ℃；日平均气温CLDAS融合产品总体较实况偏低1 ℃，兰州

城区产品偏差相对较小；30 ℃以上高温天数融合产品与实况分布基本一致，但在兰州城区，CLDAS融

合产品的高温天数较观测天数偏少。（3）线性回归法和递减平均法对CLDAS气温融合产品都有一定

的订正效果，递减平均法订正效果更优且在高海拔地区订正效果更明显。CLDAS气温实况融合产品

在兰州和武威两地能较好地反映气温变化特征，但日最高、最低气温误差较逐小时气温大，且在复杂

地形下误差相对较大。