【作者】 周林；

【导师】 张镭； 许吟隆；

【作者基本信息】 兰州大学 ， 大气物理学与大气环境， 2013， 硕士

【摘要】 对气候变量进行可信的预估是气候变化影响评估的基础和前提。模式情景预估的统计释用方法研究旨在减小气候模式的各类偏差,是提高模式预估水平的一个重要方面。本文利用区域气候模式系统PRECIS对中国区域在SRES AIB’情景下的气候预估进行两种统计释用方法订正的研究分析。两种方法分别基于平均态调整(DC, Delta Change)与基于概率分布调整(DBS, Distribution-Based Scailing)。订正变量选取日降水、日平均温度、日最高温度和日最低温度,控制时段选取1962.12-1992.11,验证时段选取1992.12～2002.11。比较分析验证时段两种方法在这几个气候变量的均值、年内循环、概率分布、极端降水与温度指标几方面的释用效果,发现：DBS方法对气候变量均值的释用效果与DC方法相近,且对多数地区变量年内循环、概率分布以及极端指标的释用效果相对显著得多,同时存在DC方法释用效果更显著的情况。由于DBS方法对变量进行统计订正时不仅仅考虑均值的调整,更考虑了方差、极值等其他统计特征的调整,DBS方法总体上比DC方法优越。1.两种方法有效改善模拟降水与温度均值的空间分布,特别是对模拟偏差大值的显著减小,且释用效果相近。全国范围绝对偏差减小均达80%,各地区降水(温度)相关性从0.5(0.9)提高到0.95(1.0)。DBS (DC)方法对多数地区日最高(低)温度的改善效果更显著。同时,DC方法对热带地区日最高温度具有明显过订正。2.两种方法有效改善模拟降水与温度的年内循环。全国范围绝对偏差的减小均以日最低温度最大(42%、53%)而日最高温度最小(18%、33%),各地区降水相关性从0.7提高到0.8,温度相关性与模拟均一致接近1。除华南与西南DC方法对日最高温度的释用效果更显著外,DBS方法对多数地区降水与温度的释用效果更显著,但两种方法对华南降水均具有过订正,且DC方法对华东降水与日最高温度具有过订正。3.两种方法不同程度改善四季模拟降水与温度的边缘概率分布,且DBS方法的改善强度更大、范围更广。四季平均降水(温度)通过K-S检验的格点比率从29%(8%)提高到49%(21%)和74%(36%)。少数地区DC方法的释用效果更好,例如,冬季华北南部与中部北部地区的日最高温度概率分布；并且存在过订正,例如,DC方法对上海与浙江降水与温度存在明显过小订正与过低订正。夏季降水与冬夏季温度的概率分布改善程度最小,说明极端降水与高/低温是影响概率分布订正的重要原因,是提高统计释用的关键。4.两种方法可显著改善模拟连续干日数CDD、连续5日最大降水量R5D、极端年较差ETR、霜冻日数FD与日最低温度计算的高温热浪强度HTWI2,并改善极端降水贡献率,但对日最高温度计算的高温热浪指数HTWI1.1和HTWI1.2的改善不明显。FD与HTWI2地区平均相关性可达0.95以上。DBS方法对除FD外的各指标全国范围绝对偏差减小均较DC方法更大,且对除FD与HTWI2外的各指标地区相关性提高更多。少数地区DC方法的释用效果更好,例如,青藏高原的FD与东北的HTWI2。过订正现象的存在,多出现在R95T与HTWI1的统计释用中,且DC方法的过订正略多于DBS方法。因此,在影响评估研究中,应根据地区、气候变量以及研究侧重点(例如,平均态或极值)的不同,有必要选择最合适的统计释用方法订正的气候情景预估,作为评估模式的气候输入。更多还原

【Abstract】 Credible estimates of climate variables are the basis and premise of the assessment of the climate change impacts. The elimination of various types from climate models is the important aspect of improving climate projection. Therefore, this paper aims to make a research on the different statistical correction methods based on Delta Change (DC) and Distribution-based Scailing (DBS) used to reduce the bias from PRECIS projection, such as P, Tm, Tmax and Tmin, in China under SRES A1B scenario.1962.12-1992.11is chosen as the control period and1992.12～2002.11is chosen as the validation period. Compare the correction results in terms of average spatial distribution, annual cycle, probability distribution, extreme indices and find that DBS can correct the average biases as well as DC, but it can correct annual cycle, probability distribution and extreme indices over most regions better than DC. There are some circumstances that DC acts better than DBS. In general, DBS is better than DC, since it takes not only mean value but also the standard deviation and extreme values into account when correcting the variables.1. DC and DBS do a good and comparative job in terms of simulated mean precipitation and temperature, especially decreasing the large biases significantly. The absolute biases decrease up to80%in China and the precipitation (temperature) R increase to0.95(1.0) from0.5(0.9). DBS(DC) can correct Tmax(Tmin) over most regions better. Meanwhile, DC overcorrects Tmax in tropical regions.2. DC and DBS do a good and comparative job in terms of simulated annual cycle of precipitation and temperature. The absolute biases of Tmin decrease the largest (42%,53%) and Tmax the least (18%,33%). The precipitation R increase to0.8from0.7and the temperature R is similar to the simulated R, which is close to1. Except DC does better at Tmax in HN region and XN region, DBS can do better at precipitation and temperature over most regions. While the two methods both overcorrect P in HN region and DC also overcorrects P and Tmax in HD region.3. DC and DBS can correct the simulated probability distribution of precipitation and temperature and DBS is better. The grid ratio that pass the K-S test in every season precipitation (temperature) is from29%(8%) up to49%(21%) and74%(36%). There are some circumstances that DC acts better than DBS, e.g. the PDF of Tmax in South HD region and North ZB region. There are some overcorrections, e.g. DC overcorrects precipitation and temperature in Shanghai and Zhejiang. The precipitation in summer and Temperature in winter and summer have been corrected the least, which indicates extreme values are important to PDF correction and are the key to improve the correcting technique.4. DC and DBS can correct the simulated CDD, R5D, ETR, FD and HTWI2much significantly, and the R95T as well. While they can not correct HTWI1.1or HTWI1.2significantly. The region-averaged R of FD and HTWI2can be larger than0.95. DBS can decrease the absolute biases of all the indices much more than DC and increase the region-averaged R of these indices, except FD and HTWI2, more than DC. DC can do a better job in some regions, e.g. FD in QZGY region and HTWI2in DB region. The overcorrections exist more in R95T and HTWI1and DC overcorrects more than DBS.As a result, in the impact assessment researches, it is necessary to choose the better statistical correction method to correct the climate projections as the input of assessment models, based on the different regions, climate variables and research goals.更多还原