news

Categories

Search

[Seminar] Dr. Haeyoung Lee

November 5, 2021

The observations of atmospheric CO2 and 14CO2 at KMA/GAW regional stations, their characteristics, and implications.

To understand the carbon cycle at policy-relevant spatial scales, a high density of high-quality CO2 measurement sites is needed. In 2012, the Korea Meteorological Administration (KMA) installed CO2 monitoring systems at Anmyeondo (AMY) in the west, Jejudo Gosan Suwolbong (JGS) in the southwest, and Ulleungdo (ULD) in the east of South Korea. In this presentation their monitoring system, and measurement uncertainty will be presented. We also show the observed CO2 characteristics at each station and comparisons with other east Asia station. The radio carbon (14C) in CO2 was known for the tracer of fossil fuel CO2 contributions. AMY collected air for 14C analysis from 2014 to 2016 to analyze characteristics of fossil fuel CO2. The proxies such as CO and SF6 are used for the calculation of emission ratios from observations to compare to those values from inventories. This study provided information on sources of observed CO2 at AMY and confirms the measurement data can verify and improve reported bottom-up inventories. Here, this result will be discussed briefly.

[Seminar] Prof. Wonbae Jeon

November 2, 2021

Modeling studies on chemical production/loss of PM2.5 and O3 during their long-range transport

The first study investigates the production/loss of sulfate on the sea surface during its transport from Eastern China to South Korea. Results of the CMAQ simulation show high sulfate (SO42-) concentrations over the sea surface areas between Eastern China and South Korea despite nearly zero emissions. The results from a quantitative analysis using the integrated process rate (IPR) in CMAQ suggest that increasing SO42- concentrations during the transport was mainly attributable to chemical SO42- productions. The chemical production of SO42- over the Yellow Sea can primarily be attributed to the “aerosol process”, which is mainly dependent on weather conditions (e.g., temperature and wind speed) and concentrations of precursors such as SO2 and OH. The results of the analysis of the mechanism of SO42- formation using the Sulfur Tracking Model (STM) show that most chemical SO42- production on the surface of the Yellow Sea is the result of the aqueous-phase chemical reactions following the SO2 oxidation reaction (OH + SO2 → H2SO4 + HO2). The second study presents an analysis of high surface ozone (O3) episodes occurring in a rural area (Chuncheon), which is situated 70 km to the prevailing westerly downwind direction of Seoul Metropolitan Area. Although Chuncheon has much lower emission levels than Seoul, the daily mean and maximum O3 levels were higher in Chuncheon than those in Seoul during the episode days. Results of CMAQ simulation demonstrate that the O3 concentration in the air mass moving from Seoul to Chuncheon was very sensitive to the concentration of nitrogen oxide (NOx) because of abundant biogenic volatile organic compounds (BVOCs). The IPR results also show that the NOx emitted from Seoul strongly affected the high O3 levels over its downwind area, mainly with local BVOC emissions. The produced O3 was gradually accumulated during its transport downwind, leading to an O3 concentration maximum at Chuncheon.

[Seminar] Dr. Haklim Choi

October 31, 2021

Measurement of atmospheric halogenated compounds and the implication for regional emissions in East Asia

Halogen substances (fluoride, chlorine, bromine, and iodine) are chemical elements that play a fundamental role in the Earth’s atmosphere and are associated with a variety of environmental problems. It is well known that halogens (primarily chlorine and bromine) destroy the Earth’s stratospheric ozone layer and cause the infamous “ozone hole” over Antarctica that was first known in the 1980s. The artificial halogen compounds, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), are representative ozone-depleting substances (ODSs) that have been produced by industry for a variety of uses such as refrigerants, foam blowing agents, propellants, solvents, and fire retardants. For this reason, the consumption and production of these compounds are regulated by the Montreal Protocol to protect the stratospheric ozone layer. Hydrofluorocarbons (HFCs) as an alternative to CFCs and HCFCs, rapidly increased in use, are greenhouse gases (GHG) thousands of times more powerful than CO2 in terms of global warming potential (GWP). Accordingly, the production and consumption of HFCs in developed and developing countries will be phase-down under the Kyoto Protocol and the Kigali Amendment. In terms of economic and industrial in East Asia, which includes China, Korea, and Japan, these halogen compounds are significant factors influencing the climate system. However, research on emission sources and the quantification of these substances is still insufficient. In this presentation, the abundance of halogenated compounds in the atmosphere will be analyzed that observed at Gosan, a regional monitoring site in East Asia that has been operated since 2008 as a part of the Advanced Global Atmospheric Gases Experiment (AGAGE). Moreover, we introduce the estimated regional and country-specific emissions using not only the Interspecies correlation (ISC) method but also the inversion framework, FLEXINVERT+, which applies a Bayesian optimization method based on the FLEXPART (FLEXible PARTicle) Lagrangian transport and dispersion model.

[Seminar] Prof. Masahito Ueyama

October 22, 2021

Biosphere-atmosphere interaction in boreal ecosystems under changing climate

Boreal forests, so called taiga, occupy the circum-polar land between the north dominated by arctic tundra and south dominated by temperate forests. They occupy approximately 9% of the total land, and accumulate up to 23% of global soil carbon stock. The northern high latitude regions have experienced 3.1 o C warming during the past 40 year; warming speed is three times of the global mean of the warming. In the lecture, I review environmental changes currently happened in the northern high latitudes: sea ice declining, greening vegetation, prolonged growing season of vegetation, permafrost degradation, and increasing and intensified wild fires. Then, I introduce our research activities, monitoring biosphere-atmosphere interaction in boreal forests in Alaska. First, I introduce the eddy covariance method, which is the key technique for monitoring fluxes between ecosystem and the atmosphere. Then, I introduce long-term measurements of CO 2 flux at a lowland black spruce forest on the ice-rich permafrost in Fairbanks, Alaska (US-Uaf site registered in AmeriFlux; Ueyama et al., 2014) and measurements of CO 2 flux at two burned forests after fire (US-Rpf and US-Fcr sites; Ueyama et al., 2019). Finally, I introduce regional CO 2 flux based on the upscaling CO 2 fluxes measured at multiple sites, through international collaborations (Ueyama et al., 2013; Virkkala et al., 2021).

[Seminar] Dr. Young-Cheol Kwon

October 11, 2021

한국형수치예보모델, 현업 1주년 성과 및 계획

한국형수치예보모델 (Korean Integrated Model: KIM)은 2011년부터 2019년까지 9년간 자체 개발로 만들어진 전 지구 모델이다. 기상청은 2020년 4월 28일부터 공식 현업모델로서 KIM 운영을 시작하였으며, 이는 지난 20여년간 외국모델에 의존하던 우리나라 기상예보에 획기적인 전환점이라 생각된다. 한국형모델의 지난 1년간의 현업운영 후 성능을 북반구 전체 예보정확도 측면에서 평가한 결과, 500hPa 지위고도의 이상상관계수는 병행운영 영국 통합모델 (UM)에 비해 약 98% 정도의 성능을 보였다. 반면 작년 여름철 우리나라 여름철 기상예측은 한국형모델이 통합모델과 유사하거나 약간 우수한 성능을 보였다. 예를 들어 작년 역대 최장 장마철의 강수예측의 정확도 (ACC)는 KIM이 0.67, UM이 0.68로 비슷하였으나 최고기온의 예측은 KIM이 더 우수하였다. 지난해 8월말에 우리나라에 영향을 주었던 바비, 마이삭, 하이선은 KIM이 강도에서 UM은 경로 예보에서 우위를 보였다.

[Seminar] Prof. Hana Kim

October 5, 2021

스마트 에너지 전환 – ‘정보제공의 인식과 소비 변화 연구 소개’

그간 전력소비자는 한 달 동안의 전력소비량과 요금에 대한 정보를 한 달에 한 번 제공받아왔다. 이 결과 소비자는 “언제” “어떤 가전제품 혹은 전자기기”를 “얼마나” 사용하고 있는지, 내 소비패턴이 전기요금에 미치는 영향에 대해 제한된 합리성(bounded rationality)에 기반해 전기를 소비해왔다. 스마트미터는 에너지 사용량을 실시간으로 계측하고 이를 공급자뿐 아니라 소비자에게도 이를 제공함으로써, 효율적인 전력 수급 관리를 지원하는 기기로, 2024년까지 총 2,250만호에 설 완료를 목표로 2020년 9월 기준 전국 982만 호에 보급이 완료되었다. 이는 ‘탄소 중립시나리오(안)’의 전환부문의 주요 정책으로 제언된 ‘전국민적 참여를 통해 전력수요의 감축 유도’를 이행가능하게 할 가장 근본적인 수단이기도 하다. 그러나 실제 스마트미터에서 생산되는 정보를 활용하는 가구 비율을 매우 낮아, 실시간 전력 소비 정보제공에 따른 전력 소비패턴 변화 및 요인별 영향력 규명이 필요한 실정이다. 본 세미나에서는 에너지 전환의 측면에서 스마트 미터의 역할과 ‘카이스트 녹색 커뮤니케이션’ 연구팀에서 진행 중인 연구와 연구의 기대효과를 공유하고자 한다.

[Seminar] Prof. Xinzhao Chu

September 28, 2021

First Lidar Observations of Vertical Transport of Heat and Meteoric Na by the Complete Temporal Spectrum of Gravity Waves in the Mesosphere and Lower Thermosphere (MLT) over McMurdo, Antarctica

The upper atmosphere is filled with waves that originate in the lower atmosphere from storm systems and airflow over mountainous terrain, and then propagate upward. These waves play key roles in establishing the composition and temperature structures by mixing the upper atmosphere and by perturbing chemical reactions of important reactive species like atomic oxygen and ozone. By using meteoric sodium (Na) that is injected between 78 and 110 km altitude by the vaporization of cosmic dust, as a tracer, and exciting the Na atoms to fluorescence using a lidar system located at McMurdo Station, Antarctica, we directly measured the vertical transport of heat and Na induced by the full spectrum of waves. The results in the lower thermosphere (97–106 km) show that wave-driven motions in this region are not purely adiabatic (heat does not enter or leave the perturbed air parcel for adiabatic motions), which contradicts conventional thinking. By comparing the measured Na transport with theory, we also show that many of the waves between 80 and 95 km are propagating downward, which we believe are generated in this region when upward propagating waves become unstable and break, much like ocean waves behave when breaking over a shoal. This seminar will also introduce the lidar campaigns and highlight science discoveries made by the University of Colorado lidar group during the last 10+ years in Antarctica.

[Seminar] Dr. Sungju Moon

September 24, 2021

Chaos Synchronization and data assimilation

Examples of synchronization, pervasive throughout the natural world, are often awe-inspiring because they tend to transcend our human intuition. Synchronization found in chaotic dynamical systems, of which the Lorenz ’63 system is a quintessential example, is even more surprising because the very defining features of chaos include sensitive dependence on initial conditions. In this talk, I will explore chaos synchronization in high-dimensional extensions of the Lorenz ’63 system. These systems are conceived from both physical and mathematical points of view, faithful to the original derivation of the Lorenz ’63 system out of the governing partial differential equations that describe two-dimensional Reyleigh-Benard convection. In particular, the (3N)- and (3N+2)-dimensional generalizations extend the Lorenz ’63 system to higher dimensions by including additional wavenumber modes, allowing the system to resolve smaller scale motions. These generalized Lorenz systems exhibit not only self-synchronization when two coupled systems are identical but also generalized synchronization when they are of different dimensions. It is emphasized that chaos synchronization between high- and low-dimensional Lorenz systems following these generalizations share some similarities with a conceptual understanding of data assimilation; namely, given a high-dimensional ‘true’ system and lower-dimensional ‘model’ system, the information transmitted from the true system to the model system can be taken as the ‘observations’. Following this conceptual framework, it is argued that the generalized Lorenz systems can serve as a testbed model for evaluating various data assimilation schemes and can stand out amongst other more widely used testbed models such as the Lorenz ’63 and ’96 systems. Preliminary testbed results for the ensemble Kalman filter scheme using a very simple setup involving the (3N)-dimensional Lorenz systems will be discussed.

[Seminar] Dr. Hanli Liu

September 17, 2021

Development of NCAR WACCM-X and Its Research Applications

As a research laboratory under the National Science Foundation (NSF), the National Center for Atmospheric Research (NCAR) is responsible for developing and maintaining research facilities for community use. Community models are an important part of this service. The High Altitude Observatory (HAO) has led the development of community models for studying the space environment, including the Thermosphere-Ionosphere-Mesosphere General Circulation Model (TIE-GCM) and the Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X). WACCM-X is a first-principle model that simulates processes from the Earth surface to the upper thermosphere, including radiative, physical, chemical, dynamical, and electrodynamical processes. It is used to study various coupling processes for Sun-Earth connection. In this talk, I will briefly describe the numerical requirements for developing a whole atmosphere model, and the structure, components, and current capabilities of WACCM-X. I will show examples applying the model for studying (1) lower atmospheric forcing of the upper atmosphere, and (2) climate response to solar forcing. I will also present an outlook of future development.

[Seminar] Dr. Nicholas Pedatella

September 14, 2021

Predictability of the Mesosphere and Lower Thermosphere during Major Sudden Stratospheric Warmings

Sudden stratospheric warmings (SSWs) significantly influence the entirety of Earth’s atmosphere, with effects ranging from the troposphere to the ionosphere and thermosphere. The impacts of SSWs on the upper atmosphere are especially dramatic, and SSWs are recognized as a significant source of the day-to-day weather of the near-Earth space environment. As SSWs can be predicted ~10-15 days in advance, they provide the potential to improve predictability of the near-Earth space environment. In this study, the predictability of the middle atmosphere during major SSWs is investigated based on subseasonal hindcasts in the Community Earth System Model, version 2 with the Whole Atmosphere Community Climate Model as its atmospheric component (CESM2(WACCM6)). The CESM2(WACCM6) hindcasts allow for the first comprehensive investigation into the predictability of the mesosphere and lower thermosphere (MLT) during SSWs. Analysis of 14 major SSWs demonstrates that CESM2(WACCM6) hindcasts initialized ∼5-15 days prior to the SSW onset are able to predict the timing of the SSW, though they underestimate the strength of the SSW. Aspects of the MLT variability, such as the mesosphere cooling and enhanced semidiurnal tide, are found to be well predicted. The demonstrated ability to predict MLT variability during SSWs indicates the potential for improved multi-day space weather forecasting through the use of whole atmosphere models that can predict the MLT variability that drives ionosphere-thermosphere variability during SSWs.

[Seminar] Dr. Jihoon Ryu

September 10, 2021

GPM/DPR에서 관측된 전구영역 집중호우의 강수입자크기분포 특성

위 분류를 통해 얻은 결과 중 두 가지 결과에 주목하고 있다. 하나는 대륙성 깊은 대류 유형의 구름 높이 분포에서 나타나는 두 개의 극값이다. 이에 착안하여 구름 높이에 따라 두 가지 유형으로 분류한 결과 각 유형의 발생 지역 및 시기가 두 가지로 명확히 구분되는 것을 발견하였다. 강수입자가 큰 유형에 대해 기존 연구에서 잘 알려진 여름철 육지에서 주로 나타나는 깊은 대류 구름 유형과 더불어 구름의 높이가 낮고 겨울철 중위도 지역의 스톰트랙에서 주로 발생된 유형이 발견되었다. 두 번째 결과는 해양성 얕은대류유형 발생비율이 동태평양 열대수렴대 지역에서 상당히 높은 점이다. 이 결과는 해당 지역에 영향을 미치는 대규모 대기순환과 연관이 있다고 생각된다. 현재 이 두 결과에 대한 추가적인 연구가 진행 중이다.

[Seminar] Prof. Taehee Hwang

September 3, 2021

Linking vegetation dynamics with watershed-scale hydrologic behavior

Forested watersheds provide important ecosystem services through the provision of high quality freshwater, mitigation of floods, and maintenance of base flows. Therefore, it is important to understand how watershed-scale hydrologic behavior will be altered by forest responses under ongoing climate change. We investigated the impact of climate-induced vegetation dynamics, such as longer growing season and infestation, on long- or short-term non-stationary hydrologic behavior across the eastern US. Within a distributed hydrological modeling framework, we combine multi-temporal remote sensing data and field observations to separate the net effect of vegetation dynamics on emergent hydrologic behavior at the watershed scale. Our study indicates that non-stationary hydrologic behavior at the forested watersheds has been closely mediated by seasonal and structural forest canopy responses to climate variables rather than directly driven by climatic variables. This talk would emphasize the importance of understanding the ecosystem responses to ongoing climate change for predictions of future freshwater regimes.

[Seminar] Dr. Kanghyun Song

June 4, 2021

Stratospheric-Tropospheric interaction and its application: Stratospheric sudden warming events

Stratospheric sudden warming (SSW) events are one of the most remarkable examples of subseasonal variability in the boreal-winter stratosphere. These events are driven by vertically-propagating planetary-scale waves from the upper troposphere, but also significantly impact on the tropospheric circulation through stratosphere-troposphere dynamical coupling. The downward influence is often maintained for up to two months in the northern extratropics. The SSW events also exhibit pronounced interannual variability, related to El Niño-Southern Oscillation (ENSO) in the troposphere and quasi-biennial oscillation (QBO) in the stratosphere. The SSW events occur more favorably during El Niño and easterly-phase QBO winters. Due to the long-lasting impact on the troposphere and the relationship with the interannual variability, the SSW events have been regarded as an important source for subseasonal-to-seasonal (S2S) prediction in the northern extratropics. In the numerical weather prediction models, the tropospheric prediction skills are improved during the winters accompanying SSW events. For the better prediction on the S2S timescale, the improved prediction of SSW events should be needed during the winter.

[Seminar] Dr. Junhong Lee

May 31, 2021

Implementation of the 3D Smagorinsky turbulence scheme in the ICON model and its applications

The efforts have been taken to perform the simulation at a higher resolution. The storm- resolving simulation is one of the approaches to reduce the uncertainty due to convective parameterization. A much higher resolution is needed to resolve shallow convection which is also another major source of uncertainty. However, the previous turbulence parameterization is not valid on this scale. In the present work, the 3D Smagorinsky turbulence scheme is implemented in the ICOsahedral Non-hydrostatic (ICON) model, which enables the ICON model to perform even at the scale in large-eddy simulations. The details of the implementation and evaluations are discussed. Implemented 3D Smagorinsky turbulence scheme reproduces the mean profiles of reference model well. In addition, the applications using the 3D Smagorinsky turbulence scheme are briefly introduced.

[Seminar] Dr. Daniel Holdway

May 12, 2021

Towards the next generation data assimilation system for NASA’s GEOS model

The Joint Center for Satellite Data Assimilation (JCSDA) is developing the Joint Effort for Data assimilation Integration (JEDI). JEDI is built using a generic software infrastructure making it reusable and sharable between weather forecast centers around the World. Unlike legacy data assimilation system JEDI can function using any model grid and set of fields. FV3-JEDI will form the interface between JEDI and the atmospheric components of models formulated using the FV3 (Finite Volume cubed-sphere) dynamical core. These models include NASA’s GEOS model and NOAA’s GFS model. Similarly an interface is being formulated between the ocean and sea-ice components of these models and JEDI. In this talk we will describe the effort towards constructing these systems and report on the progress towards achieving operationally viable data assimilation using the JEDI data assimilation system.

[Seminar] Dr. Jae-Heung Park

May 7, 2021

New approach for estimating soil moisture and soil organic matter from microwave brightness temperature

Various climate (i.e., oceanic and atmospheric) variability modes with interannual timescales are co- existed around the Pacific Ocean. In the tropics, the El Nino-Southern Oscillation (ENSO) which is characterized by the strongest interannual variability in the world exists. For the subtropical North Pacific, the Pacific Meridional Mode (PMM) which is another ocean-atmospheric coupled variability mode evolves, in association with the Pacific Intertropical Convergence Zone (ITCZ). For the midlatitudes, the Aleutian Low (AL) and the North Pacific Oscillation (NPO) reside together, which are primary atmospheric modes, featured as a monopole and a meridional dipole of sea level pressure anomaly, respectively.

[Seminar] Prof. Hyungjun Kim

April 27, 2021

New approach for estimating soil moisture and soil organic matter from microwave brightness temperature

Runoff is one of key component in water cycle which partitions precipitation with evapotranspiration and storage changes as the results of energy and water balance at the Earth’s surface. In numerical model, it is defined as water draining out from a soil column of which amount is greater than field capacity. River is an integrated pathway to transport runoff to ocean. It has important roles not only lateral distribution of water but also energy and biogeochemical constituents.

[Seminar] Dr. Chang-Hwan Park

April 23, 2021

New approach for estimating soil moisture and soil organic matter from microwave brightness temperature

Soil moisture (SM) plays a critical role in weather and climate by effecting to atmospheric variables via evapotranspiration. For example, the near-surface air temperature can change by evapotranspiration of surface and root zone soil moisture. Therefore, its correlation with the near surface temperature is usually considered as an effective indicator of the coupling strength between land surface and the atmosphere (Seneviratne et al., 2013) . Especially, soil moisture anomaly in dry regime has been reported as a main cause of the strong land-atmosphere coupling able to trigger droughts and heat waves (Miralles et al., 2011) . Soil moisture also influences precipitation formation and storm tracks via its coupling with the atmosphere (Santanello et al., 2019 ) . Consequently, inaccurate SM in the land-surface-model initialization hinders us from better predictions of extreme climate and weather because of unrealistic land-atmosphere interactions through uncertainties in air temperature, moisture, dynamics, cloud formation and precipitation. Therefore, the data assimilation (DA) of global soil moisture estimation from remote sensing measurements becomes more and more critical in weather and climate prediction. In this seminar, I would like to introduce new microwave radiative transfer model (RTM) required in DA system improved by considering variability of soil organic matter and vegetation scattering albedo. As a result, the improved RTM can provide more accurate soil moisture estimation from SMAP brightness temperature with uncertainty information to DA system. Soil organic matter (SOM) plays also a critical role for the parametrization for surface run-off, infiltration, evapotranspiration and soil respiration in hydrological modeling. It means that more accurate estimates of SOM from remote sensing measurements will allow us to predict more realistic SM and ST ultimately effecting on surface air temperature and relating weather and climate events. We are the novel RTM capable of capturing the unrecognized global variability of SOM with well synchronized with SM from SMAP microwave brightness, which will be key in proper reflection of hydrological impact on climate prediction model. In this seminar, I will provide a preliminary result about whether it is possible to estimate not only soil moisture, but also soil SOM simultaneous from microwave.

[Seminar] Dr. Hyeyum Shin

April 9, 2021

Supporting Urban Air Mobility Operations with Building-Resolving Simulations: Weather Sensitivities of Fine-Scale Urban Flows

The recent emergence of unmanned aerial system (UAS) and urban air mobility (UAM), the new frontiers in air transportation operating in the atmospheric boundary layer (ABL), is expanding the scope of aviation turbulence forecasting system from ensemble-mean to eddy-resolving forecasts (Muñoz-Esparza et al. 2018). Despite its tangible benefits, operational turbulence- resolving forecasting at scales of 10-100 m is not quite feasible yet due to its high computational costs, and resolving urban landscapes at scales of 1 m for UAM applications poses additional challenges. This study investigates the impact of urban landscapes on low-level turbulence and associated turbulence hazards to UAM operations, based on ideal- and real-case building- resolving simulations using the GPU-accelerated FastEddy® large-eddy simulation (LES) model (Sauer and Muñoz-Esparza 2020) with explicit representation of building effects by an immersed body force method (Muñoz-Esparza et al. 2020).

[Seminar] Dr. Yongjoo Choi

April 2, 2021

Regional variability in black carbon and carbon monoxide ratio from long-term observations over East Asia: assessment of emission inventories and wet removal scheme

The ability to obtain accurate emission estimates of greenhouse gases (GHGs) has been highlighted as an important issue for many decades, not only for regulating local air quality but also for assessing national-scale air quality and climate concerns. In particular, urban emissions need to be well-understood because approximately 70% of anthropogenic greenhouse gas emissions originate from urban areas. Emission of carbon dioxide (CO2) and methane (CH4) and the meteorological factors affecting them using an aircraft equipped with a cavity ring-down greenhouse gas sensor as part of the Alpha Jet Atmospheric eXperiment (AJAX) project flights in a cylindrical pattern was estimated over Sacramento, California. To better constrain the emission fluxes, we designed flights in a cylindrical pattern and computed the emission fluxes from two flights using a kriging method and Gauss’s divergence theorem. Differences in wind treatment and assumptions about background concentrations affect the emission estimates by a factor of 1.5 to 7. The uncertainty is also impacted by meteorological conditions and distance from the emission sources. The total flux estimates accounting for the entire circumference are larger than those based solely on measurements made in the downwind region. This indicates that a closed-shape flight profile can better contain total emissions relative to a one-sided curtain flight because most cities have more than a point source and wind direction can change with time and altitude. To reduce the uncertainty of the emission estimate, it is important that the sampling strategy account not only for known source locations but also possible unidentified sources around the city. Other than CO2 and CH4 emission estimates study, the recent studies regarding long-range ozone transport and extreme precipitation events (e.g. atmospheric rivers) are also briefly introduced.