中文摘要：

利用中国通量网（ChinaFLUX）4个森林台站（长白山、千烟洲、鼎湖山和西双版纳）2003—2008年总辐射和光合有效辐射（PAR）观测资料,研究了CNR1总辐射表和Li-190SB光量子仪在长期观测中可能出现的不确定性和仪器性能变化等问题.结果表明：98%以上的CNR1总辐射观测精度满足技术标准,但在西双版纳站,CNR1观测的总辐射（QCNR1）比高精度短波辐射仪CM11观测的总辐射（QCM11）平均低7%;虽然温度对CNR1观测的总辐射有一定影响,但其影响大都在仪器允许的精度范围内,在西双版纳站,CNR1除了受温度影响外,还受到热带雨林特有的季节性雾的影响;通过分析光合有效辐射数据（特别是其与总辐射比值）的长期变化发现,光量子仪Li-190SB的性能衰减较明显,平均年衰减率达4%左右.为了校正PAR仪器性能衰减产生的系统误差,本文尝试给出了PAR的后期补偿校正方法,该方法可基本消除由于野外长期使用所造成的Li-190SB性能衰减.

英文摘要：

Based on the total radiation and photosynthetically active radiation（PAR） observations with net radiometer（CNR1） and quantum sensor（Li-190SB） in 4 ChinaFLUX forest sites（Changbaishan,Qianyanzhou,Dinghushan,and Xishuangbanna） in 2003-2008,this paper analyzed the uncertainties and the radiometers performance changes in long-term and continuous field observation.The results showed that the 98% accuracy of the total radiation measured with CNR1（QCNR1） could satisfy the technical criterion for the sites except Xishuangbanna where the QCNR1 was averagely about 7% lower than QCM11,the radiation measured with high accuracy pyranometer CM11.For most sites,though the temperature had definite effects on the performance of CNR1,the effects were still within the allowable range of the accuracy of the instrument.Besides temperature,the seasonal fog often occurred in tropical rain forests in Xishuangbanna also had effects on the performance of CNR1.Based on the long-term variations of PAR,especially its ratio to total radiation in the 4 sites,it was found that quantum sensor（Li-190SB） had obvious performance attenuation,with the mean annual attenuation rate being about 4%.To correct the observation error caused by Li-190SB,an attempt was made to give a post-correction of the PAR observations,which could basically eliminate the quantum sensor＇s performance attenuation due to long-term field measurement.