Projects & Research Interest

Extreme weather (Synoptic-scale Rossby waves, Atmospheric Rivers (ARs)) processes and their link to climate (ENSO, MJO, AO, QBO).
Greenhouse gas (GHG) flux estimate and its variability modulated by atmospheric circulation at multi-scales
Sources and processes associated with local- and long-range transport of ozone and Its surface impact and human health

Meteorological impact on aerosol transport and low cloud and their interactions
ARs-wildfire-vegetation/ecosystem interactions

Atmospheric Rivers

An atmospheric river (AR) is a narrow corridor or filament of moisture in the atmosphere. In California, Atmospheric rivers primarily occur during winter when extratropical cyclones are most prevalent. The atmospheric rivers cause significant precipitation and flooding events. (Kim et al., 2013; Ryoo et al., 2015)

Extreme Weather and its link to Climate

The intensity, occurrence frequency, duration, and location of extreme weather are closely affected by existing climate patterns and large- and synoptic-scale atmospheric dynamics. For example, the El Niño–Southern Oscillation (ENSO) can alter precipitation location and intentisity through the differences in the strength and patterns of the subtropical jet and Rossby wave breakings (Potential vorticity intrusions) (Ryoo et al., 2013)

GHG flux & emission estimates

Top-down Greenhouse gas (GHG, e.g. CO2 and CH4) flux estimates demonstrated that a closed-shape aircraft measurement is very useful for identifying emission sources and estimating local and city-scale GHG fluxes (Ryoo et al., 2019).
We detected a short-term increase in CO2 mole fraction in an urban city, when traffic, energy use patterns, and other sources and sinks are expected to be different. CO2 flux tends to be largely affected by traffic. (Ryoo et al., in preparation)

Ozone Transport & surface impact

The back-trajectory model simulation demonstrates the air masses of interest came mostly from the mid troposphere (MT), but the contribution of the lower troposphere (LT) is also significant. Air coming from the LT appears to be mostly originating over Asia. The possible surface impact of the high O3 transported aloft on the surface O3 concentration through vertical and horizontal transport occurs within a few days after sampling (Ryoo et al., 2017; CABOTS)

Topography-induced surface wind and precipitation

Three different Terrain Trapper Airflows were found during an AR event and they affect the timing, locations, and intensity of precipitation in coastal and mountain regions. The blocking (e.g. barrier jets) and unblocking (e.g. gap flows) event depends on the mountain height and upstrem wind speed (Ryoo et al., 2020).

Aerosol transport and low cloud shaped by meteorology

Biomass-burning aerosols from western Africa in the Southeastern Atlantic region is advected by the southern African easterly jet (AEJ-S). For example, anomalously low aerosol optical depth in August 2017 is found along with anomalously low AEJ-S (Redemann et al., 2021; Ryoo et al., 2021; Ryoo et al. 2022)

Extreme weather-wildfire linkage

We found the record-high wildfire activity in 2020 was associated with hotter, drier, and windier conditions, with its peak shifted from July to August, unlike the climatological fire seasonality in the western U.S. It was also linked to satellite-observed low soil moisture during pre- and on fire season but high vegetation greenness, a proxy of fuel load, during the pre-fire season. Long-lived, successive, and coastal ocean originated (centered) Atmospheric Rivers (ARs) with high precipitation help suppress fire activity (e.g. September-November 2016), while short-lived or no ARs with strong wind and little precipitation rather yield fire activity (e.g. August and September 2020). (Ryoo et al.,2023)

"There is only one road to human greatness through the school of hard knocks." -Einstein

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