GPM ATMS on SUOMI-NPP (GPROF) Radiometer Precipitation Profiling L2 1.5 hours 16 km V08 (GPM_2AGPROFNPPATMS_CLIM) at GES DISC

Version 08 is the current version of the data set. Older versions are no longer available and have been superseded by the current version.

The "CLIM" products differ from their "regular" counterparts (without the "CLIM" in the name) by the ancillary data they use. They are Climate-Reference products, which requires homogeneous ancillary data over the climate time series. Hence, the ECMWF-Interim (European Centre for Medium-Range Weather Forecasts, 2-3 months lag behind the regular production) reanalysis is used as ancillary data to derive surface and atmospheric conditions required by the GPROF algorithm for the "CLIM" output. The GPROF databases are also adjusted accordingly for these climate-referenced retrievals.

The 2AGPROF (Goddard Profiling) algorithm retrieves consistent precipitation and related science fields from the following GMI and partner passive microwave sensors:
+ TMI (TRMM)
+ GMI, (GPM)
+ SSMI (DMSP F15), SSMIS (DMSP F16, F17, F18, F19)
+ AMSR2 (GCOM-W1)
+ MHS (NOAA 18,19)
+ MHS (METOP A,B)
+ ATMS (NPP)
+ SAPHIR (MT1)

This provides the bulk of the 3-hour coverage achieved by GPM. For each sensor, there are nearrealtime (NRT) products, standard products, and climate products. These differ only in the amount of data that are available within 3 hours, 48 hours, and 3 months of collection, as well as the ancillary data used. The NRT product uses GANAL forecast fields. Standard products use the GANAL analysis product, while the climate product uses ECMWF reanalysis in order to allow for consistent data records with earlier missions. These earlier data may be archived separately. The main strength of the product is the large sampling provided.

The GPM radiometer algorithms are Bayesian-type algorithms. These algorithms search an apriori database of potential rain profiles and retrieve a weighted average of these entries based upon the proximity of the observed brightness temperature (Tb) to the simulated Tb corresponding to each rain profile. By using the same a-priori database of rain profiles, with appropriate simulated Tb for each constellation sensor, the Bayesian method is completely parametric and thus well suited for GPM's constellation approach. The a-priori information will be supplied by the combined algorithm supplied by GPM's core satellite as soon after launch as feasible. Databases for V0 of the algorithm had to be constructed from various sources as described in the ATBD. The solution provides a mean rain rate as well as the vertical structure of cloud and precipitation hydrometeors and their uncertainty.

GPM Project generated these data at spatial sampling of 16 x 18 km (cross-track x along-track nominal at nadir).

本数据集当前版本为V08，旧版本已不再提供，由当前版本完全取代。

带“CLIM”后缀的产品（下称CLIM产品）与同名常规产品（名称不含“CLIM”）的区别在于其所使用的辅助数据。CLIM产品为气候参考产品，需保证气候时间序列内的辅助数据具备均一性。为此，CLIM产品的GPROF算法所需的地表与大气条件，需借助ECMWF-Interim（欧洲中期天气预报中心，比常规生产滞后2-3个月）再分析资料作为辅助数据进行推导。针对这类气候参考反演产品，GPROF数据库也已做出相应调整。

2AGPROF（戈达德廓线算法，Goddard Profiling）可从以下GMI及合作伙伴的被动微波传感器数据中反演得到一致的降水及相关科学场：
+ TMI（TRMM，热带降雨测量任务）
+ GMI（GPM，全球降水测量计划）
+ SSMI（DMSP F15）、SSMIS（DMSP F16、F17、F18、F19）
+ AMSR2（GCOM-W1）
+ MHS（NOAA 18、19）
+ MHS（METOP A、B）
+ ATMS（NPP）
+ SAPHIR（MT1）

该算法可覆盖GPM计划实现的大部分3小时级观测频次。针对每款传感器，本数据集包含近实时（near-realtime, NRT）产品、标准产品与气候参考产品三类。三类产品的差异仅在于数据获取后的可用时效（分别为3小时内、48小时内与3个月内）以及所采用的辅助数据。其中，NRT产品采用GANAL预报场数据；标准产品采用GANAL分析场数据；而气候参考产品则采用ECMWF再分析资料，以确保与早期任务的数据记录保持均一性。此类早期数据可单独归档存储。本产品的核心优势在于其庞大的观测采样覆盖范围。

GPM辐射计反演算法属于贝叶斯类算法。此类算法会遍历潜在降水廓线的先验数据库，并基于观测亮温（brightness temperature, Tb）与各降水廓线对应的模拟亮温的匹配程度，对数据库中的条目进行加权平均反演。通过采用统一的降水廓线先验数据库，并为各组网传感器配置适配的模拟亮温参数，该贝叶斯方法为完全参数化算法，因此非常适配GPM的卫星组网观测方案。先验信息将在GPM核心卫星发射后尽快通过联合反演算法提供。该算法V0版本的数据库需按照算法理论基础文档（Algorithm Theoretical Basis Document, ATBD）中所述的方法，从多源数据中构建。反演结果可给出平均降水率、云与降水水凝物的垂直分布结构，以及对应的反演不确定性。

GPM项目生成的本数据集空间采样分辨率为16×18 km（星下点标称规格：跨轨向×沿轨向）。