Annual Precipitation Projections 2050-2079

What does the data show? This data shows annual averages of precipitation (mm/day) for 2050-2079 from the UKCP18 regional climate projections. The data is for the high emissions scenario (RCP8.5). Limitations of the data We recommend the use of multiple grid cells or an average of grid cells around a point of interest to help users get a sense of the variability in the area. This will provide a more robust set of values for informing decisions based on the data. What are the naming conventions and how do I explore the data? This data contains a field for the average over the period. They are named 'pr' (precipitation), the month, and 'upper' 'median' or 'lower'. E.g. 'pr Median' is the median value. To understand how to explore the data, see this page: https://climatedataportal.metoffice.gov.uk/pages/user-guide Please note, if viewing in ArcGIS Map Viewer, the map will default to ‘pr January Median’ values. What do the ‘median’, ‘upper’, and ‘lower’ values mean? Climate models are numerical representations of the climate system. To capture uncertainty in projections for the future, an ensemble, or group, of climate models are run. Each ensemble member has slightly different starting conditions or model set-ups. Considering all of the model outcomes gives users a range of plausible conditions which could occur in the future. For this dataset, the model projections consist of 12 separate ensemble members. To select which ensemble members to use, the annual averages of precipitation for 2050-2079 were calculated for each ensemble member and they were then ranked in order from lowest to highest for each location. The ‘lower’ fields are the second lowest ranked ensemble member. The ‘upper’ fields are the second highest ranked ensemble member. The ‘median’ field is the central value of the ensemble. This gives a median value, and a spread of the ensemble members indicating the range of possible outcomes in the projections. This spread of outputs can be used to infer the uncertainty in the projections. The larger the difference between the lower and upper fields, the greater the uncertainty. Data source pr_rcp85_land-rcm_uk_12km_12_ann-30y_200912-207911.nc (median) pr_rcp85_land-rcm_uk_12km_05_ann-30y_200912-207911.nc (lower) pr_rcp85_land-rcm_uk_12km_04_ann-30y_200912-207911.nc (upper) UKCP18 v20190731 (downloaded 04/11/2021) Useful links Further information on the UK Climate Projections (UKCP). Further information on understanding climate data within the Met Office Climate Data Portal本数据集展示了何种内容？本数据集呈现了英国气候投影18（UKCP18）区域气候预估中2050至2079年的降水（precipitation）年平均值（单位：毫米/日），所用情境为高排放情景（RCP8.5）。 数据局限性 我们建议使用多个网格单元或目标点周边网格单元的平均值，以帮助用户感知区域内的变异性，这将为基于本数据集的决策提供更稳健的数值依据。 命名规范与数据探索方法 本数据集包含时段平均值字段，命名格式为'pr'（降水precipitation的缩写）、月份，以及'upper'（上限）、'median'（中位数）或'lower'（下限）。例如，'pr Median'代表中位数数值。如需了解数据探索方法，请参阅此页面：https://climatedataportal.metoffice.gov.uk/pages/user-guide 请注意，若在ArcGIS地图查看器中浏览，地图将默认显示"pr January Median"（一月降水中位数）数值。 ‘中位数’‘上限’与‘下限’数值的含义 气候模型是气候系统的数值表征。为捕捉未来预估中的不确定性，研究者会运行一个集合（ensemble）气候模型组。每个集合成员的初始条件或模型设置均存在细微差异。综合所有模型结果，可得到未来可能出现的一系列合理情景。本数据集的模型预估包含12个独立的集合成员。针对每个位置，先计算每个集合成员2050-2079年的降水年平均值，再按从低到高的顺序对其进行排序。其中，‘lower’字段对应排名第二低的集合成员，‘upper’字段对应排名第二高的集合成员，‘median’字段对应集合的中心数值。由此得到的中位数以及集合成员的离散区间，可体现预估中可能出现的结果范围。该输出离散区间可用于推断预估中的不确定性：下限与上限数值的差值越大，则不确定性越高。 数据集文件 相关数据文件如下： pr_rcp85_land-rcm_uk_12km_12_ann-30y_200912-207911.nc（中位数） pr_rcp85_land-rcm_uk_12km_05_ann-30y_200912-207911.nc（下限） pr_rcp85_land-rcm_uk_12km_04_ann-30y_200912-207911.nc（上限） 数据集版本为UKCP18 v20190731（下载于2021年11月4日） 相关链接 英国气候预估（UKCP）的更多相关信息。 英国气象局（Met Office）气候数据门户中关于气候数据解读的更多内容。