2-km resolution oversampled NH3 data

Monthly, high resolution (~2 km) ammonia (NH3) column maps from the
Infrared Atmospheric Sounding Interferometer (IASI) were developed across
the contiguous United States and adjacent areas. Ammonia hotspots (95th
percentile of the column distribution) were highly localized with a
characteristic length scale of 12 km and median area of 152 km2. Five
seasonality classes were identified with k-means++ clustering. The Midwest
and eastern United States had a broad, spring maximum of NH3 (67% of
hotspots in this cluster). The western United States, in contrast, showed
a narrower mid-summer peak (32% of hotspots). IASI spatiotemporal
clustering was consistent with those from the Ammonia Monitoring Network.
CMAQ and GFDL-AM3 modeled NH3 columns have some success replicating the
seasonal patterns but did not capture the regional differences. The high
spatial-resolution monthly NH3 maps serve as a constraint for model
simulations and as a guide for the placement of future, ground-based
network sites.

本数据集包含基于红外大气探测干涉仪（Infrared Atmospheric Sounding Interferometer, IASI）生成的、覆盖美国本土及邻近区域的月度高分辨率（约2 km）大气氨（NH₃）柱含量分布图。其中，大气氨热点区域（即柱含量分布第95百分位数对应的区域）呈现显著的局地化特征，其特征长度尺度为12 km，中位面积达152 km²。通过k-means++聚类算法，本数据集共识别出5种季节变化类型。美国中西部与东部区域的大气氨含量峰值集中于春季，且覆盖范围较广，该聚类类别的热点占总热点的67%。与之相对，美国西部的大气氨含量峰值出现在仲夏时节，且覆盖范围相对狭窄，该聚类类别的热点占总热点的32%。IASI的时空聚类结果与氨监测网络（Ammonia Monitoring Network）的观测结果具有一致性。CMAQ与GFDL-AM3模式模拟的大气氨柱含量虽能一定程度复现季节变化规律，但未能准确刻画区域差异。这套高空间分辨率月度大气氨分布图，既可用于约束模式模拟工作，也可为未来地面监测网络的站点选址提供指导依据。