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1.
Homogenization of climate observations remains a challenge to climate change researchers, especially in cases where metadata (e.g., probable dates of break points) are not always available. To examine the influence of metadata on homogenizing climate data, the authors applied the recently developed Multiple Analysis of Series for Homogenization (MASH) method to the Beijing (BJ) daily temperature series for 1960--2006 in three cases with different references: (1) 13M---considering metadata at BJ and 12 nearby stations; (2) 13NOM---considering the same 13 stations without metadata; and (3) 21NOM---considering 20 further stations and BJ without metadata. The estimated mean annual, seasonal, and monthly inhomogeneities are similar between the 13M and 13NOM cases, while those in the 21NOM case are slightly different. The detected biases in the BJ series corresponding to the documented relocation dates are as low as -0.71oC, -0.79oC, and -0.5oC for the annual mean in the 3 cases, respectively. Other biases, including those undocumented in metadata, are minor. The results suggest that any major inhomogeneity could be detected via MASH, albeit with minor differences in estimating inhomogeneities based on the different references. The adjusted annual series showed a warming trend of 0.337, 0.316, and 0.365oC (10 yr)-1 for the three cases, respectively, smaller than the estimate of 0.453oC (10 yr)-1 in the original series, mainly due to the relocation-induced biases. The impact of the MASH-type homogenization on estimates of climate extremes in the daily temperature series is also discussed.  相似文献   

2.
Homogenized Daily Relative Humidity Series in China during 1960?2017   总被引:1,自引:0,他引:1  
Surface relative humidity(RH)is a key element for weather and climate monitoring and research.However,RH is not as commonly applied in studying climate change,partly because the observation series of RH are prone to inhomogeneous biases due to non-climate changes in the observation system.A homogenized dataset of daily RH series from 746 stations in Chinese mainland for the period 1960–2017,ChinaRHv1.0,has been developed.Most(685 or 91.82%of the total)station time series were inhomogeneous with one or more break points.The major breakpoints occurred in the early 2000s for many stations,especially in the humid and semi-humid zones,due to the implementation of automated observation across the country.The inhomogeneous biases in the early manual records before this change are positive relative to the recent automatic records,for most of the biased station series.There are more break points detected by using the MASH(Multiple Analysis of Series for Homogenization)method,with biases mainly around?0.5%and 0.5%.These inhomogeneous biases are adjusted with reference to the most recent observations for each station.Based on the adjusted observations,the regional mean RH series of China shows little long-term trend during 1960–2017[0.006%(10 yr)^?1],contrasting with a false decreasing trend[?0.414%(10 yr)?1]in the raw data.It is notable that ERA5 reanalysis data match closely with the interannual variations of the raw RH series in China,including the jump in the early 2000s,raising a caveat for its application in studying climate change in the region.  相似文献   

3.
利用国家气象信息中心2013年发布的逐日均一化气温资料,对沈阳站资料均一化处理前后平均气温和极端气温指数序列的线性趋势及其城市化影响偏差进行了比较评价。结果表明:1)资料均一化处理对日最高气温及其衍生的极端气温指数序列趋势估计的影响较弱,但对日最低气温及其衍生的极端气温指数序列趋势估计具有显著影响。2)经资料均一化处理后,平均气温序列中的城市化影响偏差有所增大,平均最低气温序列中的城市化影响偏差增大尤其明显;与冷事件有关的极端气温指数序列的城市化影响偏差数值有所减小,与暖事件有关的极端气温指数序列的城市化影响偏差数值有所增加。3)资料均一化处理有效纠正了因迁站等原因造成的地面气温观测记录中的非均一性,但却在很大程度上还原了城市站地面气温观测记录中的城市化影响偏差。  相似文献   

4.
中国均一化日平均温、最高温和最低温序列1960-2008   总被引:8,自引:0,他引:8       下载免费PDF全文
Inhomogeneities in the daily mean/maximum/ minimum temperature (Tm/Tmax/Tmin) series from 1960- 2008 at 549 National Standard Stations (NSSs) in China were analyzed by using the Multiple Analysis of Series for Homogenization (MASH) software package. Typical biases in the dataset were illustrated via the cases of Beijing (B J), Wutaishan (WT), Urumqi (UR) and Henan (HN) stations. The homogenized dataset shows a mean warming trend of 0.261/0.193/0.344℃/decade for the annual series of Tm/Tmax/Tmin, slightly smaller than that of the original dataset by 0.006/0.009/0.007℃/decade. However, considerable differences between the adjusted and original datasets were found at the local scale. The adjusted Tmin series shows a significant warming trend almost everywhere for all seasons, while there are a number of stations with an insignificant trend in the original dataset. The adjusted Tm data exhibit significant warming trends annually as well as for the autumn and winter seasons in northern China, and cooling trends only for the summer in the middle reaches of the Yangtze River and parts of central China and for the spring in southwestern China, while the original data show cooling trends at several stations for the annual and seasonal scales in the Qinghai, Shanxi, Hebei, and Xinjiang provinces. The adjusted Tmax data exhibit cooling trends for summers at a number of stations in the mid-lower reaches of the Yangtze and Yellow Rivers and for springs and winters at a few stations in southwestern China, while the original data show cooling trends at three/four stations for the annual/autumn periods in the Qinghai and Yunnan provinces. In general, the number of stations with a cooling trend was much smaller in the adjusted Tm and Tmax dataset than in the original dataset. The cooling trend for summers is mainly due to cooling in August. The results of homogenization using MASH appear to be robust; in particular, different groups of stations with consideration of elevation led to minor effects i  相似文献   

5.
A second generation adjusted precipitation daily dataset has been prepared for trend analysis in Canada. Daily rainfall and snowfall amounts have been adjusted for 464 stations for known measurement issues such as wind undercatch, evaporation and wetting losses for each type of rain-gauge, snow water equivalent from ruler measurements, trace observations and accumulated amounts from several days. Observations from nearby stations were sometimes combined to create time series that are longer; hence, making them more useful for trend studies. In this new version, daily adjustments are an improvement over the previous version because they are derived from an extended dataset and enhanced metadata knowledge. Datasets were updated to cover recent years, including 2009. The impact of the adjustments on rainfall and snowfall total amounts and trends was examined in detail. As a result of adjustments, total rainfall amounts have increased by 5 to 10% in southern Canada and by more than 20% in the Canadian Arctic, compared to the original observations, while the effect of the adjustments on snowfall were larger and more variable throughout the country. The slope of the rain trend lines decreased as a result of the larger correction applied to the older rain-gauges while the slope of the snow trend lines increased, mainly along the west coast and in the Arctic. Finally, annual and seasonal rainfall and snowfall trends based on the adjusted series were computed for 1950–2009 and 1900–2009. Overall, rainfall has increased across the country while a mix of non-significant increasing and decreasing trends was found during the summer in the Canadian Prairies. Snowfall has increased mainly in the north while a significant decrease was observed in the southwestern part of the country for 1950–2009.

  相似文献   

6.
The CarbonTracker(CT) model has been used in previous studies for understanding and predicting the sources, sinks, and dynamics that govern the distribution of atmospheric CO_2 at varying ranges of spatial and temporal scales. However, there are still challenges for reproducing accurate model-simulated CO_2 concentrations close to the surface, typically associated with high spatial heterogeneity and land cover. In the present study, we evaluated the performance of nested-grid CT model simulations of CO_2 based on the CT2016 version through comparison with in-situ observations over East Asia covering the period 2009–13. We selected sites located in coastal, remote, inland, and mountain areas. The results are presented at diurnal and seasonal time periods. At target stations, model agreement with in-situ observations was varied in capturing the diurnal cycle. Overall, biases were less than 6.3 ppm on an all-hourly mean basis, and this was further reduced to a maximum of 4.6 ppm when considering only the daytime. For instance, at Anmyeondo, a small bias was obtained in winter, on the order of 0.2 ppm. The model revealed a diurnal amplitude of CO_2 that was nearly flat in winter at Gosan and Anmyeondo stations, while slightly overestimated in the summertime. The model's performance in reproducing the diurnal cycle remains a challenge and requires improvement. The model showed better agreement with the observations in capturing the seasonal variations of CO_2 during daytime at most sites, with a correlation coefficient ranging from 0.70 to 0.99. Also, model biases were within-0.3 and 1.3 ppm, except for inland stations(7.7 ppm).  相似文献   

7.
百分位统计降尺度方法及在GCMs日降水订正中的应用   总被引:9,自引:0,他引:9  
刘绿柳  任国玉 《高原气象》2012,31(3):715-722
在格点观测的逐日降水量数据基础上,采用百分位统计降尺度方法对全球气候模式(GCM)输出的日降水量进行了订正处理。5种订正方案的比较结果表明,取12个百分位数进行日降水量订正是合理的。观测资料与3个GCMs订正前后全国平均年、季降水量空间分布以及主要流域平均年、月和日降水序列多年平均、变化趋势及概率密度的对比分析表明:(1)统计降尺度处理可在一定程度上降低GCMs模拟的降水量偏差,特别是中国中部、长江以南和东北部分地区,对德国马普研究所的海气耦合模式(MPI/ECHAM5)模拟的降水量订正效果最显著;(2)GCMs统计降尺度处理的降水量季节分布特征与观测更为接近,所有流域MPI/ECHAM5订正的降水量优于或接近直接输出结果;(3)与GCM直接输出的降水相比,部分流域经统计降尺度处理后降水量变化趋势与观测的一致性有所增加,但不明显;(4)当日降水量<30mm时,订正的降水量与观测的偏差明显减小;当日降水量>30mm时,部分流域由负偏差转为正偏差。由于GCMs结构和降尺度方法的局限性,在用于具体流域未来气候变化预估及气候变化影响评估时,应选择尽可能多的、模拟能力强的GCMs数据,以包含尽可能多的模拟气候情景。  相似文献   

8.
Despite their potential impact, trends in thunderstorm occurrence in Canada have not received scientific scrutiny, one of the reasons for this likely being lack of data availability. A previous study showed thunderstorm observations at eight staffed weather stations in southern Ontario, Canada, to be accurate for distances within 10?km. We used hourly thunderstorm data from these stations and one additional station to determine whether a trend exists in the thunderstorm record in this region. A Mann-Kendall test and Theil-Sen approach determined that although some stations do have trends in number of thunderstorm hours per year over this time, a consistent increase in the number of thunderstorms that might be expected in a warming climate is not seen. Daily precipitation totals and maximum wind gust speeds were also used as proxies for thunderstorm intensity, neither of which confirmed an increase in the intensity of thunderstorms at these sites over the time period.  相似文献   

9.
青藏高原是全球变化研究的热点区域,气候模式模拟是研究该区域气候变化的重要数据来源。本文使用基于中国地面台站的插值格点数据集(CN05.1),对国际气候耦合模式第5次比较计划(CMIP5)及其高分辨率统计降尺度数据集(NEX-GDDP)中15个模式1966-2005年间的逐日最高/最低气温、降水和平均风速在青藏高原区域的模拟能力进行了评估。使用多领域间影响模型比较计划(ISI-MIP)的偏差校正方法对上述数据进行了训练和验证,并对未来时期模式数据进行了校正。研究表明:(1)训练时期(1986-2005年),NEX-GDDP高估了日最高气温(1.04℃)和日最低气温(0.23℃),低估了日降水量(-0.11 mm),CMIP5低估了日平均风速(-0.11 m·s-1)。年/季平均值/总量和极端值存在较大偏差。(2)校正后,验证时期(1966-1985年)各变量逐日数据的相关系数提高(除气温外),均方根误差下降,平均偏差幅度减小。各变量的年/季平均值/总量和极端值的偏差大幅减小。(3)对于未来时期(2006-2095年),校正过程保留了原有数据年/季平均值/总量和极端值的变化趋势,调整了各要素平均值/总量和极端值的基准值和空间分布特征,以更准确地衔接历史时期的规律,可为该地区未来气候变化及其影响研究提供重要参考。  相似文献   

10.
以高山站为背景研究城市化对气温变化趋势的影响   总被引:4,自引:0,他引:4  
本文基于1957~2005年的逐日气象资料,对比分析了中国东部7组高山气象站和山下附近的城市气象站年 与四季气温变化趋势.在此基础上,利用高山站作为气候变化背景场来分析城市化对平均气温、最高气温、最低气温变化趋势影响的性质和程度,及其对气温变化非对称性的影响.结果表明:平均气温和最低气温变化趋势城市站多比高山站大,而最高气温变化趋势高山站多比城市站大;城市站最低气温变化趋势均大于最高气温变化趋势,具有明显的非对称性现象,而高山站这种表现十分微弱.城市站气温变化受到明显的城市化影响,对于平均气温和最低气温以正影响为主,而对于最高气温为负影响为主,说明城市化对气温变化的影响也存在非对称性.城市化影响的非对称性是气温变化非对称性形成的主要因素.  相似文献   

11.
Summary Observational biases in hourly surface wind speed and direction measurements from 41 northeastern U.S. stations are evaluated. Based on this analysis, a number of consistent wind observation biases are detected which should be considered when using these data in modeling and other climatological applications. These biases include a preference to report wind speed as a multiple of either 2 or 5 kt and a similar bias for reporting even, in terms of tens of degrees, wind directions. Temporal and station-dependent trends in estimating winds less than the starting speed of the anemometer are also evident. Given these biases, potential inaccuracies in analyses using wind data are illustrated. In addition, analyses are conducted to identify biases related to archival and summarization practices. In particular, the comparability of wind climatologies based on varying record lengths is determined. These assessments suggest that at least nine years of data are required to obtain representative wind frequency tabulations. The potential consequences of using too small of a record length are also illustrated. To achieve this minimum record length, climatologies can be constructed using either hourly or 3-hourly observations. Received February 26, 1996 Revised April 21, 1997  相似文献   

12.
利用1960~2015年京津冀地区88个国家级气象站观测资料(包括日平均气温、日最高气温、日最低气温、日降水、日平均风速等),使用MASH(Multiple Analysis of Series for Homogenization)方法剔除台站迁址、仪器变更等因素所致偏差后,生成均一化的观测资料集。基于新资料集计算了各站气温、降水和凤速序列的线性趋势和Morlet小波等统计特征,分析了京津冀地区气候变化格局。结果表明:MASH方法能较准确地检测并校订观测序列中迁站、仪器变更等因素所导致的非均一性;1960~2015年期间京津冀年平均气温显著上升,上升幅度为0.261℃/10 a;降水减少,平均减少11.27 mm/10 a;风速显著减小,平均减小0.193 m s-1(10 a)-1。  相似文献   

13.
为深入认识城市对其附近气象站气温的影响,采用位于长沙市区东部和西部两个气象观测站的2007-2009年的逐日气温、风向和风速资料,结合地表覆盖特征数据,对比分析了两站气象记录差异,并通过改进的城市影响指数模型估算了气温资料中的城市影响偏差。分析显示:(1)2007-2009年东、西气象站逐月平均气温(Tmean)、最高气温(Tmax)和最低气温(Tmin)差异很大,最大差异分别可达0.90℃、0.83℃和1.34℃;(2)受城市及风向的影响,两气象站的逐月城市影响指数(K)差异较大,东、西站平均K值分别为2.01和1.50,年内同一台站的K值存在季节变化规律;(3)两站逐月△K与△T之间存在极显著正相关关系;(4)东、西两站2007年Tmean中的城市增温最大,分别达0.63℃和0.45℃。城市附近气象站气温记录受城市规模、风向和风速等因素影响明显,在分析长历时气候变化特征和利用站点记录数据进行空间分析时,有必要对气温数据进行订正。  相似文献   

14.
Annually averaged daily maximum and minimum surface temperatures from southeastern China were evaluated for artificial discontinuities using three different tests for undocumented changepoints. Changepoints in the time series were identified by comparing each target series to a reference calculated from values observed at a number of nearby stations. Under the assumption that no trend was present in the sequence of target-reference temperature differences, a changepoint was assigned to the target series when at least two of the three tests rejected the null hypothesis of no changepoint at approximately the same position in the difference series. Each target series then was adjusted using a procedure that accounts for discontinuities in average temperature values from nearby stations that otherwise could bias estimates of the magnitude of the target series step change. A spatial comparison of linear temperature trends in the adjusted annual temperature series suggests that major relative discontinuities were removed in the homogenization process. A greater number of relative change points were detected in annual average minimum than in average maximum temperature series. Some evidence is presented which suggests that minimum surface temperature fields may be more sensitive to changes in measurement practice than maximum temperature fields. In addition, given previous evidence of urban heat island (i.e., local) trends in this region, the assumption of no slope in a target-reference difference series is likely to be violated more frequently in minimum than in maximum temperature series. Consequently, there may be greater potential to confound trend and step changes in minimum temperature series.  相似文献   

15.
根据北京和上海气象观测站的详细历史资料,修正了两站逐日温度序列的不均一性,并分析这种不均一性对长期气候变化趋势估计的影响。对北京序列,不同时期的主要修正幅度在-0.33-0.6℃;对上海序列则为-0.33-0.3℃。从逐日序列计算出年平均温度和年极端温度序列,并把修正之前和修正之后的序列趋势进行比较,修正之后的两站年平均温度序列自20世纪初起呈现出0.5℃/百年的变暖趋势,自20世纪60年代起这一趋势增强为2.0℃/百年。相比之下,上海的未修正资料显示出两倍于此的趋势;北京的未修正资料几乎没有长期趋势,而对近期的变暖趋势则高估了50%-30%。北京温度序列在20世纪40年代至70年代呈变冷趋势,极端事件的频率降低;此后又呈变暖趋势,极端事件的频率增加。上海温度极端事件的变化趋势基本呈相反趋。这意味着即使区域性平均温度变化一致,区域性强天气波动的变化趋势也会有所不同。  相似文献   

16.
基于统计降尺度模型的江淮流域极端气候的模拟与预估   总被引:4,自引:0,他引:4  
利用江淮流域29个代表站点1961--2000年逐日最高温度、最低温度和逐日降水资料,以及NCEP逐日大尺度环流场资料,引入基于多元线性回归与随机天气发生器相结合的统计降尺度模型SDSM(statistical downscalingmodel),通过对每个站点建模,确立SDSM参数,并将该模型应用于SRESA2排放情景下HadCM3和cGcM3模式,得到了江淮流域各代表台站21世纪的逐日最高、最低温度和降水序列以及热浪、霜冻、强降水等极端气候指数。结果表明,当前气候下,统计降尺度方法模拟的极端温度指数与观测值有很好的一致性,能有效纠正耦合模式的“冷偏差”,如SDSM对江淮平均的冬季最高、最低温度的模拟偏差较CGCM3模式分别减少3℃和4.5℃。对于极端降水则能显著纠正耦合模式模拟的降水强度偏低的问题,如CGCM3对江淮流域夏季降水强度的模拟偏差为-60.6%,但降尺度后SDSM—CGCM3的偏差仅为-6%,说明降尺度模型SDSM的确有“增加值”的作用。21世纪末期在未来SRESA2情景下,对于极端温度,无论Had.CM3还是CGCM3模式驱动统计模型,江淮流域所有代表台站,各个季节的最高、最低温度都显著增加,且以夏季最为显著,增幅在2—4℃;与之相应霜冻天数将大幅减少,热浪天数大幅增多,各站点冬季霜冻天数减少幅度为5—25d,夏季热浪天数增加幅度为4~14d;对于极端降水指数,在两个不同耦合模式HadCM3和CGCM3驱动下的变化尤其是变化幅度的一致性比温度差,但大部分站点各个季节极端强降水事件将增多,强度增强,SDSM—HadCM3和SDSM-CGCM3预估的夏季极端降水贡献率将分别增加26%和27%。  相似文献   

17.
We evaluate the capacity of a regional climate model to represent observed extreme temperature and precipitation events and also examine the impact of increased resolution, in an effort to identify added value in this respect. Two climate simulations of western Canada (WCan) were conducted with the Canadian Regional Climate Model (version 4) at 15 (CRCM15) and 45?km (CRCM45) horizontal resolution driven at the lateral boundaries by data from the European Centre for Medium-range Weather Forecasts (ECMWF) 40-year Reanalysis (ERA-40) for the period 1973–1995. The simulations were evaluated using the spline-interpolated dataset ANUSPLIN, a daily observational gridded surface temperature and precipitation product with a nominal resolution of approximately 10?km. We examine a range of climate extremes, comprising the 10th and 90th percentiles of daily maximum (TX) and minimum (TN) temperatures, the 90th percentile of daily precipitation (PR90), and the 27 core Climate Daily Extremes (CLIMDEX) indices.

Both simulations exhibit cold biases compared with observations over WCan, with the bias exacerbated at higher resolution, suggesting little added value for temperature overall. There are instances, however, of regional improvement in the spatial pattern of temperature extremes at the higher resolution of CRCM15 (e.g., the CLIMDEX index for the annual number of days when TX?>?25°C). The high-resolution simulations also reveal similarly localized features in precipitation (e.g., rain shadows) that are not resolved at the 45?km resolution. With regard to precipitation extremes, although both simulations generally display wet biases, CRCM15 features a reduced bias in PR90 in all seasons except winter. This improvement occurs despite the fact that spatial and interannual variability of PR90 in CRCM15 is significantly overestimated relative to both CRCM45 and ANUSPLIN. We posit that these characteristics are the result of demonstrable differences between corresponding topographical datasets used in the gridded observations and CRCM, the resulting errors propagated to physical variables tied to elevation and the beneficial effect of subsequent spatial averaging. Because topographical input is often discordant between simulations and gridded observations, it is argued that a limited form of spatial averaging may contribute added value beyond that which has already been noted in previous studies with respect to small-scale climate variability.  相似文献   

18.
This study presents a simplified multivariate bias correction scheme that is sequentially implemented in the GEOS5 data assimilation system and compared against a control experiment without model bias correction. The results show considerable improvement in terms of the mean biases of rawinsonde observation-minus-background (OmB) residuals for observed water vapor, wind and temperature variables. The time series spectral analysis shows whitening of bias-corrected OmB residuals, and mean biases for rawinsonde observation-minus-analysis (OmA) are also improved. Some wind and temperature biases in the control experiment near the equatorial tropopause nearly vanish from the bias-corrected experiment. Despite the analysis improvement, the bias correction scheme has only a moderate impact on forecast skill. Significant interaction is also found among quality-control, satellite observation bias correction, and background bias correction, and the latter positively impacts satellite bias correction.  相似文献   

19.
Multi-channel sea surface temperature (MCSST) data were retrieved from the Japanese geostationary satellite, MTSAT-1R, for East Asia in western North Pacific. The coefficients used to calculate the MCSST data were estimated by assuming a linear relationship between the brightness temperatures obtained from the satellite and the in-situ buoy SST. It is important to remove cloud contamination pixels to retrieve meaningful information from infrared data. Therefore, the cloud detection algorithm was improved by using a 10-day maximum or minimum composite map for infrared and visible channels. The RMSE of the MCSST in comparison with the two-year buoy SST was about 0.89oC. The error was the largest at mid-latitudes in summer. Additionally, the error between the two SSTs showed that diurnal variation had a positive bias during daytime and a negative bias during nighttime. Furthermore, in 2007, both SSTs showed seasonal and spatial diurnal variation. The magnitude of the daily variation in the MCSST was two times larger than that in the buoy SST, and this was attributed to diurnal heating with a weak surface wind speed.  相似文献   

20.
基于南极18个站点探空气象观测数据对欧洲中期天气预报中心的再分析数据(ERA-Interim)和美国国家环境预报中心的再分析数据(NECP)在南极地区高层大气的适用性进行验证。结果表明:在南极上空,随着高度抬升,探空气象观测数据与两套再分析数据中四个气象要素的差值均逐渐变大,再分析数据数值愈加偏离实际观测数值。两套再分析数据的位势高度和温度与探空观测数据偏差较小;风向则和探空观测数据相差甚远;两套再分析数据的风速与探空观测数据在300 hPa偏差较大。在季节变化中,南极的春季,再分析数据中的位势高度和温度与探空观测数据相差较大,在其他季节相差相对较小。再分析数据中的风速与探空观测数据在南极的夏季相差较小。再分析数据中的风向与探空观测数据存在较大偏差,且差值没有明显的季节变化。尽管两套再分析数据都存在很大偏差,但ERA-Interim数据整体上优于NCEP数据。对比分析也表明,采用这些再分析资料作为初始条件和边界条件驱动南极区域大气模式将带来较大的误差。未来需要加强南极探空观测,改进再分析资料同化和数值模拟系统。  相似文献   

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