期刊
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
卷 123, 期 7, 页码 3645-3667出版社
AMER GEOPHYSICAL UNION
DOI: 10.1002/2017JD028004
关键词
urban land use; aerosol; rainfall; Gangetic Basin; cloud invigoration; microphysics
资金
- Earth System Science Organization, Ministry of Earth Sciences, Government of India under INCOMPASS project [MM/NERC-MoES-03/2014/002]
- U.S. Department of Energy's Office of Science as part of the Regional and Global Climate Modeling Program
- DOE by Battelle Memorial Institute [DE-AC05-76RL01830]
Coupling of urban land use land cover (LULC) and aerosol loading on rainfall around cities in the Gangetic Basin (GB) is examined here. Long-term observations illustrate more rainfall at urban core and climatological downwind regions compared to the upwind regions of Kanpur, a metropolitan area located in central GB. In addition, analysis of a 15day cloud resolving simulation using the Weather Research and Forecasting model also illustrated similar rainfall pattern around other major cities in the GB. Interestingly, the enhancement of downwind rainfall was greater than that over urban regions, and it was positively associated with both the urban area of the city and ambient aerosol loading during the propagating storm. Further, to gain a process-level understanding, a typical storm that propagated northwestward across Kanpur was simulated using Weather Research and Forecasting under three different scenarios. Case 1 has realistic LULC representation of Kanpur, while the grids representing the Kanpur urban region were replaced by cropland LULC pattern in Case 2. Comparison illustrated that urban heat island effect caused convergence of winds and moisture in the lower troposphere, which enhances convection over urban region and induced more rainfall over the urban core compared to upwind regions. Case 3 is similar to Case 1 but lower aerosol concentration (by a factor of 100) over the storm region. Analysis shows that aerosol-induced microphysical changes delay the initiation of warm rain (over the upwind region) but enhance ice phase particle formation in latter stages (over the urban and downwind regions) resulting in increase in downwind rainfall.
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