探空资料中的人为误差对中国温度长期变化趋势的影响

利用1958～2005年探空温度序列, 通过质量控制、均一化处理和序列缺测率分析, 探讨了探空资料中人为误差对中国高空气温变化趋势的影响。中国探空温度序列存在明显的间断点, 72%的序列包含2～4个间断点。相应的订正总体上降低了1958年以来平流层低层降温和对流层升温趋势, 如700 hPa和100 hPa平均趋势值分别降低0.12 K/10 a和0.04 K/10 a。缺测率是气温区域平均趋势估算的重要参数, 30%作为最大缺测率是中国探空温度序列适宜的取样标准。提高取样标准 (台站数减少) 使1958～2005年间对流层上层和平流层下层的降温趋势减弱。中国高空气温变化趋势与全球或北半球大体一致, 但也有不同特点: 500 hPa以下大气趋于升温, 以上则趋于降温, 最大降温趋势位于对流上部的300 hPa, 而且各气候区间区域差异性十分明显。

The Effect of Artificial Bias on Free Air Temperature Trend Derived from Historical Radiosonde Data in China

The effects of the artificial bias on free air temperature trend derived from historical radiosonde data in China were assessed, by conducting quality control, homogenization and analysis on miss rate to the individual ra-diosonde temperature time series (RTTS) during 1958-2005. Identification reveals evident discontinuities in the RTTS with 2-4 breakpoints at 72% of stations. As a result of adjustments, original RTTS exhibit systematic cool-ing biases in the lower stratosphere and warming in the troposphere, suggesting both cooling in the stratosphere and warming in the troposphere are substantially overestimated in the original radiosonde data, e.g. the cooling trend at 100 hPa decreases 0.12 K/10 a and the warming trend at 700 hPa decreases 0.04 K/10 a. Missing rate is an impor-tant index to evaluate availability of RTTS for assessing regional average trend, and analyses suggest that the maxi-mum missing rate of 30% is the optimum requirement for RTTS in China. Reduction of sampling stations results in underestimate of average trends in both the troposphere and the lower stratosphere. Upper air temperature changes in China are generally consistent with the results from the globe and the Northern Hemisphere, but there are some discrepancies: the atmosphere tends to warm below 500 hPa and cool in the upper levels with the maximum cooling around 300 hPa. Furthermore, the comparison of the trends among different sub-climatic regions implies spatial het-erogeneity in upper air temperature changes in China.