ESA Land Surface Temperature Climate Change Initiative (LST_cci): Daily land surface temperature from ATSR-2 (Along-Track Scanning Radiometer 2), level 3 collated (L3C) global product (1995-2003), version 4.00

This dataset contains land surface temperatures (LSTs) and their uncertainty estimates from the Along-Track Scanning Radiometer (ATSR-2) on European Remote-sensing Satellite 2 (ERS-2). Satellite land surface temperatures are skin temperatures, which means, for example, the temperature of the ground surface in bare soil areas, the temperature of the canopy over forests, and a mix of the soil and leaf temperature over sparse vegetation. The skin temperature is an important variable when considering surface fluxes of, for instance, heat and water.

Daytime and nighttime temperatures are provided in separate files corresponding to the morning and evening ERS-2 equator crossing times which are 10:30 and 22:30 local solar time.

Per pixel uncertainty estimates are given in two forms, first, an estimate of the total uncertainty for the pixel and second, a breakdown of the uncertainty into components by correlation length.

Also provided in the files, on a per pixel basis, are the observation time, the satellite viewing and solar geometry angles, a quality flag, and land cover class.

The dataset coverage is near global over the land surface. Small regions were not covered due to downlinking constraints (most noticeably a track extending southwards across central Asia through India – further details can be found on the ATSR project webpages at https://artefacts.ceda.ac.uk/frozen_sites/www.atsr.rl.ac.uk/documentation/docs/userguide/index.shtml).

LSTs are provided on a global equal angle grid at a resolution of 0.01° longitude and 0.01° latitude. ATSR-2 achieves full Earth coverage in 3 days so the daily files have gaps where the surface is not covered by the satellite swath on that day. Furthermore, LSTs are not produced where clouds are present since under these circumstances the IR radiometer observes the cloud top which is usually much colder than the surface.

Dataset coverage starts on 1st June 1995 and ends on 22nd June 2003. There are two gaps of several months in the dataset: no data were acquired from ATSR-2 between 23 December 1995 and 30 June 1996 due to a scan mirror anomaly; and the ERS-2 gyro failed in January 2001, data quality was less good between 17th Jan 2001 and 5th July 2001 and are not used in this dataset. There are minor interruptions (1-2 days) during satellite/instrument maintenance periods.

Version 4.00 uses data from the 4th reprocessing of the ATSR L1B archive. The emissivities used in the retrieval come from the Combined ASTER and MODIS Emissivity over Land (CAMEL) Version 2 database; in Version 4.00 a climatology is used since there are temporal instabilities in the CAMEL time series.

The dataset was produced by the University of Leicester (UoL) and LSTs were retrieved using the (UoL) LST retrieval algorithm and data were processed in the UoL processing chain.

The dataset was produced as part of the ESA Land Surface Temperature Climate Change Initiative which strives to improve satellite datasets to Global Climate Observing System (GCOS) standards.

本数据集包含搭载于欧洲遥感卫星2号（European Remote-sensing Satellite 2, ERS-2）的沿轨扫描辐射计（Along-Track Scanning Radiometer, ATSR-2）获取的地表温度（Land Surface Temperatures, LST）及其不确定性估算结果。卫星遥感获取的地表温度属于表层温度（skin temperature），具体而言，裸土区域对应地表自身温度，森林区域对应林冠层温度，而稀疏植被覆盖区则为土壤与叶片温度的混合值。在研究热量、水汽等地表通量时，表层温度是一项关键参数。
数据集按昼、夜分别存储为两个独立文件，对应ERS-2卫星的赤道过境时刻：当地太阳时10:30（晨间过境）与22:30（晚间过境）。
逐像素的不确定性估算包含两种形式：其一为该像素的总不确定性估算值，其二为基于相关长度将不确定性拆解为各分量的结果。
数据文件中还逐像素提供了观测时刻、卫星观测几何角与太阳几何角、质量控制标志（quality flag）以及土地覆盖类型（land cover class）。
本数据集的地表覆盖范围接近全球尺度，但受下行链路传输限制，部分区域未覆盖（最显著的是一条横跨中亚向南延伸至印度的观测条带）。更多细节可查阅ATSR项目官方网页：https://artefacts.ceda.ac.uk/frozen_sites/www.atsr.rl.ac.uk/documentation/docs/userguide/index.shtml。
数据集采用全球等角网格存储，空间分辨率为经度0.01°、纬度0.01°。ATSR-2需3天即可完成一次全球覆盖，因此单日数据文件存在数据空白，对应当日卫星观测条带未覆盖的地表区域。此外，有云覆盖区域不会生成LST数据，因为此时红外辐射计（IR radiometer）观测的是云顶温度，通常远低于地表实际温度。
本数据集的时间覆盖范围为1995年6月1日至2003年6月22日，存在两处为期数月的数据空白：其一，1995年12月23日至1996年6月30日期间，因扫描镜异常，ATSR-2未获取任何数据；其二，2001年1月ERS-2的陀螺仪失效，2001年1月17日至7月5日期间的数据质量较差，未纳入本数据集。此外，在卫星/仪器维护期间还存在少量1-2天的数据中断。
本数据集4.00版本采用ATSR L1B档案的第四次重处理数据。反演过程中使用的发射率来自ASTER与MODIS地表发射率融合数据集（Combined ASTER and MODIS Emissivity over Land, CAMEL）V2版本；但由于CAMEL时间序列存在时间不稳定性，4.00版本实际采用了气候态发射率。
本数据集由莱斯特大学（University of Leicester, UoL）制作，地表温度反演采用UoL自研的LST反演算法，数据处理流程亦基于UoL的标准处理链。
本数据集是欧洲空间局（European Space Agency, ESA）地表温度气候变化倡议项目的成果之一，该项目旨在将卫星遥感数据集提升至全球气候观测系统（Global Climate Observing System, GCOS）标准。