Browsing by Author "Shi, Yingxi R."
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Characterizing the 2015 Indonesia fire event using modified MODIS aerosol retrievals(EGU, 2019-01-08) Shi, Yingxi R.; Levy, Robert C.; Eck, Thomas; Fisher, Brad; Mattoo, Shana; Remer, Lorraine; Slutsker, Ilya; Zhang, JianglongThe Indonesian fire and smoke event of 2015 was an extreme episode that affected public health and caused severe economic and environmental damage. The MODIS Dark Target (DT) aerosol algorithm, developed for global applications, significantly underestimated regional aerosol optical depth (AOD) during this episode. The larger-than-global-averaged uncertainties in the DT product over this event were due to both an overly zealous set of masks that mistook heavy smoke plumes for clouds and/or inland water, and also an aerosol model developed for generic global aerosol conditions. Using Aerosol Robotic Network (AERONET) Version 3 sky inversions of local AERONET stations, we created a specific aerosol model for the extreme event. Thus, using this new less-absorbing aerosol model, cloud masking based on results of the MODIS cloud optical properties algorithm, and relaxed thresholds on both inland water tests and upper limits of the AOD retrieval, we created a research algorithm and applied it to 80 appropriate MODIS granules during the event. Collocating and comparing with AERONET AOD shows that the research algorithm doubles the number of MODIS retrievals greater than 1.0, while also significantly improving agreement with AERONET. The final results show that the operational DT algorithm had missed approximately 0.22 of the regional mean AOD, but as much as AOD = 3.0 for individual 0.5∘ grid boxes. This amount of missing AOD can skew the perception of the severity of the event, affect estimates of regional aerosol forcing, and alter aerosol modeling and forecasting that assimilate MODIS aerosol data products. These results will influence the future development of the global DT aerosol algorithm.Item Satellite-detected Ocean Ecosystem Response to Volcanic Eruptionsin the Subarctic Northeast Pacific Ocean(American Geophysical Union, 2019-09-16) Westberry, Toby, K.; Shi, Yingxi R.; Yu, H.; Behrenfeld, Michael J.; Remer, L. A.Volcanic eruptions in the Aleutian archipelago during the summer of 2008 deposited large quantities of iron-laden ash to the Subarctic North Pacific Ocean. The surface ocean ecosystem response has been previously characterized using limited in situ and autonomous field measurements and numerical modeling, but basin-scale satellite remote sensing has been limited to a simple description of chlorophyll variability. Here, we show that the ecosystem response is a complex combination of phytoplankton biomass and physiology that can be described with satellite ocean color diagnostics such as the chlorophyll to carbon biomass ratio (Chl:Cphyto) and chlorophyll fluorescence yield. Together, these quantities outline a more complete picture of ecological responses spanning unique signals of iron stress (and relief from), photoacclimation, changes in phytoplankton growth rate, increases in biomass, and timescales of decay for these processes.