CLARA-A3: CM SAF cLoud, Albedo and surface RAdiation dataset from AVHRR data - Edition 3

The CLARA-A3 record provides cloud properties and radiation parameters derived from the AVHRR
sensor onboard polar orbiting NOAA and METOP satellites. CLARA-A3 is the latest edition of
CLARA with previous editions documented in Karlsson et al. (2013) and Karlsson et al. (2017).
CLARA-A3 covers the time period 1979/01/01 until 2020/12/31 as climate data record (CDR), but
is operationally extended as interim climate data record (ICDR) to the present with a latency
of 10 days. The AVHRR measurement input to the CLARA-A3 retrieval algorithms is the EUMETSAT
PyGAC AVHRR Fundamental Data Record (FDR) Release 1 (DOI:10.15770/EUM_SEC_CLM_0060). CLARA-A3
features a range of cloud products: cloud mask, cloud top temperature/pressure/height, cloud
thermodynamic phase, and (for liquid and ice clouds separately) cloud optical thickness,
particle effective radius and cloud water path. Additionally, cloud droplet number
concentration and cloud geometrical thickness are provided for liquid clouds. Furthermore, a
range of radiation products are included in CLARA-A3: surface black-sky, white-sky and
blue-sky albedo; surface downwelling short- and longwave radiation as well as surface net
radiation; top-of-atmosphere (TOA) upwelling short- and longwave radiation. Cloud products are
available as monthly and daily averages and histograms, as well as daily resampled global
products (Level 2b) for individual satellites. Surface albedo is presented as monthly and
pentad (5 day) averages. Surface and TOA radiation products are provided as daily and monthly
averages. All averages are available on a 0.25° x 0.25° global grid. Surface albedo and
selected cloud products are also provided on two equal area grids with a resolution of 25 km x
25 km covering the polar regions. Daily resampled cloud products (level 2b) are provided in a
global grid with a resolution of 0.05°x0.05°. CLARA-A3 features a comprehensive set of
documentation including User Manuals, Validation Reports and Algorithms Theoretical Baseline
Documents.

CLARA-A3数据集提供了源自极轨NOAA与METOP卫星搭载的先进甚高分辨率辐射计（Advanced Very High Resolution Radiometer）传感器反演得到的云属性与辐射参数。CLARA-A3是CLARA数据集系列的最新版本，此前版本的相关文档可参见Karlsson等人（2013）与Karlsson等人（2017）。CLARA-A3作为气候数据记录（Climate Data Record, CDR），时间覆盖范围为1979年1月1日至2020年12月31日；其作为临时气候数据记录（Interim Climate Data Record, ICDR）已通过业务化扩展至当前，数据延迟为10天。CLARA-A3反演算法所使用的先进甚高分辨率辐射计测量输入数据，为欧洲气象卫星应用组织（European Organisation for the Exploitation of Meteorological Satellites, EUMETSAT）的PyGAC AVHRR基础数据记录（Fundamental Data Record, FDR）第1版（DOI:10.15770/EUM_SEC_CLM_0060）。CLARA-A3包含多款云产品：云掩码、云顶温度/气压/高度、云热力学相态，以及分别针对液态云与冰云的云光学厚度、粒子有效半径与云水路径。此外，还为液态云提供了云滴数浓度与云几何厚度产品。CLARA-A3还包含多款辐射产品：地表晴空反照率、全天空反照率与蓝天反照率；地表下行短波辐射、下行长波辐射以及地表净辐射；大气顶（Top-of-atmosphere, TOA）上行短波辐射与上行长波辐射。云产品可获取的形式包括月均与日均数据、直方图，以及针对单颗卫星的每日重采样全球产品（2b级）。地表反照率以月均与候均（5天平均）数据形式提供。地表与大气顶辐射产品以日均与月均数据形式提供。所有平均数据均采用0.25°×0.25°的全球网格。地表反照率与部分选定的云产品，还以25 km×25 km分辨率的两个等面积网格形式提供，覆盖极地地区。每日重采样云产品（2b级）以0.05°×0.05°的全球网格形式提供。CLARA-A3附带一套全面的文档资料，包括用户手册、验证报告以及算法理论基线文档。

搜集汇总

背景与挑战

背景概述

CLARA-A3数据集是基于AVHRR传感器的全球云、反照率和地表辐射数据集，提供从1979年至今的长期气候数据记录，包含多种云属性、辐射参数和地表反照率产品，覆盖全球范围，并具有多种时间和空间分辨率。