Research Topics
Urban Climatology and Human Health
Hu, L.*, & Brunsell, N. A., A new perspective to assess the urban heat island through remotely sensed atmospheric profiles. Remote Sensing of Environment, 158, 393-406. https://doi.org/10.1016/j.rse.2014.10.022
Hu, L.*, Monaghan, A. J., & Brunsell, N. A., Investigation of urban air temperature and humidity patterns during extreme heat conditions using satellite-derived data. Journal of Applied Meteorology and Climatology, 54, 2245-2259. https://doi.org/10.1175/JAMC-D-15-0051.1
Globally, urban environments exhibit highly diverse morphologies that are intensively influenced by regional cultures and economic development. Accurately characterizing climatic variability over such heterogeneous environments requires spatially dense observations.
To address the pressing need for better descriptions of the spatial variability of climate across cities globally, my research investigated the potential to estimate the urban near-surface air temperature and dew-point temperature using the atmospheric profile product from NASA’s MODerate resolution Imaging Spectroradiometer (MODIS)
In addition to employing thermal remote sensing for monitoring urban thermal environments, I am also interested in understanding the regional climatic features over urban areas, particularly for extreme heat events. A satellite-based approach was developed to measure and assess the spatial and diurnal variability of near-surface temperature and humidity in urban and adjacent rural areas during extreme heat events (Hu et al., 2015,J. Appl. Meteorol. Climatol.). This study unraveled the ubiquitous pattern of high temperatures and humidity throughout the Chicago metropolitan area during extreme heat events, primarily due to the disproportionate increase in rural temperature.
Another important aspect of assessing heat exposure in urban environments requires the understanding of the covariation of temperature and population temporally and spatially. My studies tackle the challenges in capturing these dynamic variables in the outdoor heat exposure assessment (Hu et al., 2018, Sci. Total Environ., Yang et a., 2020, Science Advances.).
Hu,L*, Wilhelmi, O., & Uejio, C.:Heat exposure in cities: combining the dynamics of temperature and population. Science of the Total Environment, 655, 1-12, https://doi.org/10.1016/j.scitotenv.2018.11.028
Yang, J.+*, Hu, L.+*, & Wang, C.,: Population dynamics modify urban residents’ exposure to extreme temperatures across the United States. Science Advances: https://advances.sciencemag.org/content/5/12/eaay3452
Developing Innovative Tools for Environmental Studies
Satellite remote sensing of LST has great potential for research in multiple fields, while it also has unique complications that prohibit its straightforward application, particularly over urban areas. The measurements, especially those from broad-viewing-swath sensors designed to have a high temporal frequency (sub-daily), are subject to the directional thermal anisotropy. The directional LST variation due to sensor zenith angles can reach more than 10K over highly urbanized districts. However, current airborne observing and modeling have difficulties to efficiently and effectively quantify the anisotropy over various environments at the scale of satellite observations. I developed a semi-empirical model based on MODIS LST products to quantify thermal anisotropic effects across cities as a function of the urban land use intensity (Hu et al., 2016, Remote Sens. Environ.). This study is the first of its kind to directly evaluate the influence of directional anisotropy on satellite-retrieved Surface UHI (SUHI) measurements, demonstrating that anisotropic effects can possibly introduce the uncertainty about 25~50% of the total surface urban heat island magnitudes. I am combining computer graphics techniques with detailed 3D urban building data to simulate the thermal anisotropy and quantifying the morphological impacts on anisotropy in a recent study (Hu and Wendel, 2019, ISPRS J Photogramm Remote Sens.).
Hu, L.*, & Wendel. J. : Analysis of urban surface morphologic effects on diurnal thermal directional anisotropy, Journal of Photogrammetry and Remote Sensing, 148, 1-12, https://doi.org/10.1016/j.isprsjprs.2018.12.004
While refining the satellite observations, my research also involves various quantitative remote sensing applications in agriculture, natural resource investigation, disasters, etc. If you would like to learn more about my previous and ongoing research, please see my Publications or directly contact me.