NCEP North American Regional Reanalysis (NARR)

The purpose of the National Centers for Environmental Prediction (NCEP) and National Center for Atmospheric Research (NCAR) North American Regional Reanalysis (NARR) is to create a long term set of consistent climate data on a regional scale on a North American domain. NARR is an improved long-term reanalysis of basic meteorological fields on a high resolution grid that, for the first time on any scale, includes precipitation. NARR assimilates a great deal of historical climate observational data using a 32 km version of the regional NCEP North American Mesoscale (NAM) model (formally the NCEP 1993 operational ETA model) and ETA data assimilation system (EDAS). The domain of analyses includes North and Central America as well as small parts of the UK, Eastern Asia and South America and the oceans in between. The period of the reanalyses is from October 1978 to the present and includes analyses made 8 times daily. Horizontal boundary conditions were derived from the NCEP/DOE Reanalysis, hereafter referred to as the Global Reanalysis (GR). Much of the data are the same as used as in the NCAR/NCEP GR. The data include temperatures, winds, and moisture from radiosondes, as well as pressure data from surface observations. Also included in this data set are dropsondes, pibals, aircraft temperatures and winds, and cloud drift winds from geostationary satellites. In addition to the above list, a major component of the NARR is the assimilation of precipitation. The precipitation data set comes from a variety of sources. The data over the continental United States comes from a 1/8-degree gauge data set analyzed using PRISM and a least-squares distance weighting algorithm. Over Canada and Mexico, the precipitation comes from 1-degree gauge data sets. Much of the rest of the domain's precipitation comes from CMAP (CPC [Climate Prediction Center] Merged Analysis of Precipitation), a merged combination of satellite and gauge precipitation. Other data sets include winds and precipitable water from TOVS (TIROS [Television InfraRed Observations Satellite] Operational Vertical Sounder) satellite radiances, wind and moisture from hourly and 3-hourly surface stations, and ship and buoy data. Snow depth comes from the 512x512 Air Force snow data set. Sea-surface temperatures (SSTs) contain a 1-degree Reynolds data set, including the Great Lakes. Sea ice data comes from a satellite data set used for the GR. Canadian lake ice comes from the Canadian Ice Center. This data set is encoded in WMO format GRIB version 1 using the NCEP GRIB table 131. The data are stored on a Lambert conformal grid (AWIPS grids 221) and efforts have been made to make the data GrADS compatible (http://grads.iges.org/grads).美国国家环境预报中心（National Centers for Environmental Prediction, NCEP）与美国国家大气研究中心（National Center for Atmospheric Research, NCAR）联合打造的北美区域再分析数据集（North American Regional Reanalysis, NARR），其核心目标是构建一套适用于北美区域、长期一致的区域尺度气候数据集。NARR是一套经过优化的长期再分析数据集，采用高分辨率网格对基础气象场进行再分析，且首次在全尺度范围内纳入降水要素。该数据集依托32km分辨率的NCEP北美中尺度模式（North American Mesoscale, NAM，原名为NCEP 1993业务化ETA模式）以及ETA数据同化系统（ETA Data Assimilation System, EDAS），同化了大量历史气候观测数据。其分析覆盖区域涵盖北美、中美洲，以及英国、东亚、南美洲的部分区域与其间的海域。再分析的时间跨度为1978年10月至今，每日生成8次分析结果。水平边界条件取自NCEP/DOE再分析数据集，下文简称全球再分析数据集（Global Reanalysis, GR）。 该数据集的多数数据与NCAR/NCEP全球再分析数据集（GR）所用数据同源。数据来源包括无线电探空仪获取的气温、风场与水汽数据，以及地面观测的气压数据。此外，数据集还包含下投式探空仪数据、测风气球（pibal）数据、航空器观测的气温与风场数据，以及地球静止卫星反演的云迹风数据。 除上述观测数据外，降水要素同化是NARR的核心组成部分之一，其降水数据集源自多类数据源。美国本土的降水数据取自1/8度分辨率的雨量站数据集，该数据集通过PRISM（Precipitation-elevation Regressions on Independent Slopes Model，降水-高程独立坡度回归模型）与最小二乘距离加权算法进行格点化分析。加拿大与墨西哥的降水数据则取自1度分辨率的雨量站数据集。区域内其余多数区域的降水数据取自CMAP（Climate Prediction Center Merged Analysis of Precipitation，即美国气候预测中心（Climate Prediction Center, CPC）降水合并分析数据集），该数据集是卫星与雨量站观测降水的融合产品。 其余数据集还包括取自TOVS（TIROS Operational Vertical Sounder，即泰罗斯电视红外观测卫星业务垂直探测器（Television InfraRed Observations Satellite, TIROS））卫星辐射率数据的风场与可降水量数据，逐小时及3小时地面观测站获取的风场与水汽数据，以及船舶与浮标观测数据。积雪深度数据取自512×512分辨率的空军积雪数据集。海表温度（Sea-surface Temperatures, SSTs）采用1度分辨率的Reynolds数据集，覆盖范围包括五大湖区域。海冰数据取自用于全球再分析数据集（GR）的卫星数据集。加拿大湖冰数据取自加拿大冰情中心。 本数据集采用世界气象组织（World Meteorological Organization, WMO）的GRIB第1版格式进行编码，使用NCEP的GRIB表131。数据存储于兰勃特共形投影网格（AWIPS网格221），且已针对GrADS网格分析与显示系统做了适配优化，相关兼容说明详见http://grads.iges.org/grads。