Data for: Attributes of CloudSat identified echo objects

This data set contains a collection of attributes associated with CloudSat identified echo objects (or contiguous regions of radar/dBZ echo) from15 June 2006 till 17 January 2013. CloudSat is a NASA satellite that carries a 94 GHz (3 mm) nadir pointing cloud profiling radar (CPR). CloudSat makes approximately 14 orbits per day with an equator passing time of 0130 and 1330 local time. Echo objects were identified using CloudSat's 2B-GEOPROF product that includes 2D arrays (alongtrack x vertical) of the radar reflectivity factor and gaseous attenuation correction. Also included in the product is a "cloud mask" with values ranging between 0 and 40 with higher values indicating a greater likelihood of cloud detection. An EO was defined as a contiguous region of cloud mask greater than or eaqual to 20, consisting of at least three pixels with their edges and not merely their corners touching. Each echo object (EO) is assigned multiple attributes. The geographic attributes include minimum, mean, and maximum latitude and longitude, minimum and maximium location along the CloudSat orbit track, and the underlying surface altitude and land mask data, which allows the EOs to be catagorized as occuring over land, sea, or the coast. The geometric attributes include top, mean, and bottom height, width, and the total number of pixels within the EO. Attributes describing the internal structure of the EO are also available including the number of pixels and cells (i.e., group of pixels) greater than 0 dBZ and -17 dBZ. Finally, the time of day of occurance was also recorded to compare the statistics of EOs ocurring during the daytime versus nighttime. In total, we identified 15,181,193 EOs from 15 June 2006 to 17 January 2013. After 17 April 2011, data were only collected during the day due to a battery failure onboard CloudSat. Each attribute is organized as a 1D array where the size of the array corresponds to the number of EOs. This organization allows subsets of EOs to be easily identified using simple "where" statements when writing code. The attributes were used to identify cloud types and analyze global cloud climatology according to season, surface type, and region (i.e., Riley 2009; Riley and Mapes 2009). The varability of EOs across the MJO was also analyzed (Riley et al. 2011).

本数据集收录了2006年6月15日至2013年1月17日期间，由CloudSat（CloudSat）识别出的回波对象（echo object, EO，即雷达/dBZ回波的连续区域）的各类属性集合。CloudSat是美国国家航空航天局（National Aeronautics and Space Administration, NASA）搭载94 GHz（3 mm）天底指向云廓线雷达（cloud profiling radar, CPR）的卫星，每日约运行14个轨道，过赤道时刻为当地时间01:30与13:30。回波对象通过CloudSat的2B-GEOPROF产品识别，该产品包含雷达反射率因子与气体衰减校正的二维数组（沿轨×垂直方向）。该产品还附带“云掩码”数据，其取值范围为0至40，数值越高代表云检测的可信度越高。EO被定义为云掩码值大于等于20的连续区域，且至少包含3个像素，像素间需通过边缘（而非仅角落）相互连接。每个EO均被赋予多类属性：地理属性包括纬度、经度的最小值、均值与最大值，沿CloudSat轨道的最小与最大位置，以及下垫面海拔与陆地掩码数据，借此可将EO分类为陆地、海洋或海岸上空出现的类型；几何属性包括顶高、平均高度、底高、宽度，以及EO内的总像素数。此外还包含描述EO内部结构的属性，例如反射率因子大于0 dBZ与-17 dBZ的像素及像元组（即像素群）的数量。最后还记录了EO的发生时刻，用于对比日间与夜间EO的统计特征。2006年6月15日至2013年1月17日期间，研究团队共识别出15,181,193个EO。2011年4月17日后，由于CloudSat星载电池故障，仅在日间采集数据。所有属性均以一维数组形式组织，数组长度与EO的总数一一对应，该结构便于在编程时通过简单的"where"语句快速筛选目标EO子集。本数据集的属性曾被用于云类型识别与全球云气候学分析（按季节、下垫面类型与区域划分，参见Riley 2009；Riley与Mapes 2009），同时也被用于分析EO在马登-朱利安振荡（Madden-Julian Oscillation, MJO）中的变化特征（Riley et al. 2011）。