A Gridded Climatology of Clouds over Land (1971-1996) and Ocean (1954-2008) from Surface Observations Worldwide (NDP-026E)*

Surface synoptic weather reports from ships and land stations worldwide were processed to produce a global cloud climatology which includes: total cloud cover, the amount and frequency of occurrence of nine cloud types within three levels of the troposphere, the frequency of occurrence of clear sky and of precipitation, the base heights of low clouds, and the non-overlapped amounts of middle and high clouds. Synoptic weather reports are made every three hours; the cloud information in a report is obtained visually by human observers. The reports used here cover the period 1971-96 for land and 1954-2008 for ocean. This digital archive provides multi-year monthly, seasonal, and annual averages in 5x5-degree grid boxes (or 10x10-degree boxes for some quantities over the ocean). Daytime and nighttime averages, as well as the diurnal average (average of day and night), are given. Nighttime averages were computed using only those reports that met an "illuminance criterion" (i.e., made under adequate moonlight or twilight), thus minimizing the "night-detection bias" and making possible the determination of diurnal cycles and nighttime trends for cloud types. The phase and amplitude of the first harmonic of both the diurnal cycle and the annual cycle are given for the various cloud types. Cloud averages for individual years are also given for the ocean for each of 4 seasons, and for each of the 12 months (daytime-only averages for the months). [Individual years for land are not gridded, but are given for individual stations in a companion data set, CDIAC's NDP-026D).] This analysis used 185 million reports from 5388 weather stations on continents and islands, and 50 million reports from ships; these reports passed a series of quality-control checks. This analysis updates (and in most ways supercedes) the previous cloud climatology constructed by the authors in the 1980s. Many of the long-term averages described here are mapped on the University of Washington, Department of Atmospheric Sciences Web site. The Online Cloud Atlas containing NDP-026E data is available via the University of Washington.

本数据集基于全球范围内船舶与陆基气象站的地面天气观测报告处理生成全球云气候志，包含以下内容：总云量、对流层三层内9种云型的出现量与出现频率、晴空与降水的出现频率、低云云底高度，以及中高云的无重叠云量。此类天气观测报告每3小时更新一次，报告中的云量信息由人工目视观测获取。本次研究所用的观测报告覆盖1971年至1996年的陆基观测时段，以及1954年至2008年的海洋观测时段。该数字档案提供了以5°×5°经纬度网格单元（海洋部分部分参量采用10°×10°网格单元）划分的多年月平均、季平均与年平均数据。数据集提供日间、夜间平均数据，以及日平均数据（日间与夜间数据的平均值）。夜间平均数据仅基于符合"光照判据"（即观测在充足月光或暮光条件下完成）的观测报告计算得到，以此尽可能降低"夜间探测偏差"，从而支持云型的日循环周期与夜间变化趋势分析。针对各类云型，数据集同时提供日循环与年循环的一阶谐波的相位与振幅参数。海洋部分还提供了按4个季节、12个月份划分的逐年云量平均数据（月份数据仅包含日间平均）。[陆基逐年数据未进行网格化处理，相关数据已在配套数据集CDIAC的NDP-026D中按单个观测站形式发布。]本次分析共使用来自全球大陆与岛屿上5388个气象站的1.85亿份观测报告，以及5000万份船舶观测报告，所有报告均通过了一系列质量控制检验。本数据集更新并在多数维度上替代了研究团队于20世纪80年代构建的前代云气候志。本数据集提及的多数长期平均数据已在华盛顿大学大气科学系官网发布可视化地图。包含NDP-026E数据的在线云图集可通过华盛顿大学官网获取。

搜集汇总

背景与挑战

背景概述

该数据集整合了全球地面观测站的天气报告，生成了一个包含多种云参数和降水信息的网格化气候学产品，特别强调了夜间数据的准确性和日/年变化特征，覆盖了长期的时间跨度和广泛的地理范围。