Research Interests
atmospheric remote sensing, vegetation drought, target detection.
Atmospheric Remote Sensing
Vegetation Drought
Target Detection
Research List
Wang, H., Gong, F. Y., Newman, S., & Zeng, Z. C.* (2022). Consistent weekly cycles of atmospheric NO2, CO, and CO2 in a North American megacity from ground-based, mountaintop, and satellite measurements. Atmospheric Environment, 268, 118809. https://doi.org/10.1016/j.atmosenv.2021.118809.
We focus on the weekly cycle amplitudes of nitrogen dioxide (NO2), carbon monoxide (CO), and carbon dioxide (CO2) in the Los Angeles (LA) megacity, where the significant weekly cycle of human activities exists. In addition, abundant observations are continuously being produced from existing ground-based, mountaintop, and satellite platforms to monitor LA's carbon emissions and air quality. From our analysis, significant agreement can be found in observations from different platforms. For NO2, a 30%~35% Sunday decline can be observed from ground-based and satellite observations. For CO, the Sunday drops from ground-based, mountain-top, and satellite observations are 13%~20%. The spatial pattern shown by TROPOMI agrees with traffic density in LA. Impact due to the prevailing winds from the coast in the afternoon can also be observed. For anthropogenic CO2, we show that the weekly cycle of CO2 enhancement from OCO-2 observations has a Sunday decline (15%~20%) consistent with ground-based observations and TCCON. In addition, we also investigate the weekly cycles from stable carbon isotopologue of δ13C from ground-based observations, which undoubtedly demonstrate the weekly variation in fossil fuel usage in LA. This study highlights the consistencies and effectiveness of existing observing platforms in monitoring the anthropogenic emissions of the LA megacity.
Hua, L., Wang, H., Sui, H., Wardlow, B., Hayes, M. J., & Wang, J. (2019). Mapping the spatial-temporal dynamics of vegetation response lag to drought in a semi-arid region. Remote Sensing, 11(16), 1873. https://doi.org/10.3390/rs11161873
Studies of the vegetative response to drought are paramount to providing scientific information for drought risk mitigation. We analyzed the spatial-temporal drought pattern and the vegetation response lag in Nebraska from 2000 to 2015. Based on the long-term Daymet data set, the standard precipitation index (SPI) was computed to identify precipitation anomalies, and the Gaussian function was applied to obtain temperature anomalies. Vegetation anomaly was determined by dynamic time warping technique using a remote sensing Normalized Difference Vegetation Index (NDVI) time series. Finally, multilayer correlation analysis was applied to obtain the response lag of different vegetation types. The results show that Nebraska suffered severe drought events in 2002 and 2012. The response lag of vegetation to drought typically ranges from 30 to 45 days, varying for different vegetation types and human activities (water use and management).