Yeonjoo Kim

Quantifying the strength of soil moisture-precipitation coupling and its sensitivity to changes in surface water budget

Abstract This paper presents a new index to quantify the strength of soil moisture–precipitation coupling in AGCMs and explores how the soil moisture–precipitation coupling in Community Atmosphere Model version 3 (CAM3)–Community Land Model version 3 (CAM3–CLM3) responds to parameterization-induced surface water budget changes. Specifically, this study (a) compares the regions of strong coupling identified by the newly proposed index and the index currently used in the Global Land–Atmosphere Coupling Experiment (GLACE); (b) examines how the surface water budget changes influence the strength of soil moisture–precipitation coupling as measured by the two indexes, respectively; and (c) examines how these changes influence the memory of the coupled land–atmosphere system as measured by the correlation between soil moisture and subsequent precipitation. The new index and the GLACE index are consistent in identifying central North America and West Africa as major regions of strong coupling during June–August (...

Modeling seasonal vegetation variation and its validation against Moderate Resolution Imaging Spectroradiometer (MODIS) observations over North America

[1] Seasonal variability of vegetation, determined by plant phenology, impacts the seasonality of surface and atmospheric water cycles as well as the seasonality of surface energy budget. At the same time, leaf seasonal variations respond to both cumulative and concurrent hydrometeorological conditions. In order to account for this vegetation feedback at the seasonal timescale, a predictive phenology scheme for various plant functional types is developed on the basis of previous studies, and a methodology for crop simulations is proposed and implanted to supplement this phenology scheme. The phenology scheme is then incorporated into the Community Land Model (CLM). The geographic focus of this study is on the United States where the need for seasonal prediction is urgent and vegetation seasonal characteristics have been shown to significantly influence summer precipitation and temperature. Comparison of the model simulation with Moderate Resolution Imaging Spectroradiometer (MODIS)-derived leaf area index data indicates that our model reproduces the observed vegetation seasonality reasonably well. Subsequent experiments demonstrate the interannual variability of vegetation phenology and its impact on surface water and energy budgets using the 1988 drought and 1993 flood in the U.S. Midwest as examples.

Impact of Initial Soil Moisture Anomalies on Subsequent Precipitation over North America in the Coupled Land–Atmosphere Model CAM3–CLM3

Abstract To investigate the impact of anomalous soil moisture conditions on subsequent precipitation over North America, a series of numerical experiments is performed using a modified version of the Community Atmosphere Model version 3 and the Community Land Model version 3 (CAM3–CLM3). First, the mechanisms underlying the impact of spring and summer soil moisture on subsequent precipitation are examined based on simulations starting on 1 April and 1 June, respectively. How the response of precipitation to initial soil moisture anomalies depends on the characteristics of such anomalies, including the timing, magnitude, spatial coverage, and vertical depth, is then investigated. There are five main findings. First, the impact of spring soil moisture anomalies is not evident until early summer although their impact on the large-scale circulation results in slight changes in precipitation during spring. Second, precipitation increases with initial soil moisture almost linearly within a certain range of soil...

Impact of Vegetation Feedback on the Response of Precipitation to Antecedent Soil Moisture Anomalies over North America

Abstract Previous studies support a positive soil moisture–precipitation feedback over a major fraction of North America; that is, initial soil moisture anomalies lead to precipitation anomalies of the same sign. To investigate how vegetation feedback modifies the sensitivity of precipitation to initial soil moisture conditions over North America, a series of ensemble simulations are carried out using a modified version of the coupled Community Atmosphere Model–Community Land Model (CAM–CLM). The modified CLM includes a predictive vegetation phenology scheme so that the coupled model can represent interactions between soil moisture, vegetation, and precipitation at the seasonal time scale. The focus of this study is on how the impact of vegetation feedback varies with the timing and direction of initial soil moisture anomalies. During summer, wet soil moisture anomalies lead to increase in leaf area index and, consequently, increase in evapotranspiration and surface heating. Such increases tend to favor p...

Development of fuzzy multi-criteria approach to prioritize locations of treated wastewater use considering climate change scenarios

This study proposed a robust prioritization framework to identify the priorities of treated wastewater (TWW) use locations with consideration of various uncertainties inherent in the climate change scenarios and the decision-making process. First, a fuzzy concept was applied because future forecast precipitation and their hydrological impact analysis results displayed significant variances when considering various climate change scenarios and long periods (e.g., 2010-2099). Second, various multi-criteria decision making (MCDM) techniques including weighted sum method (WSM), Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) and fuzzy TOPSIS were introduced to robust prioritization because different MCDM methods use different decision philosophies. Third, decision making method under complete uncertainty (DMCU) including maximin, maximax, minimax regret, Hurwicz, and equal likelihood were used to find robust final rankings. This framework is then applied to a Korean urban watershed. As a result, different rankings were obviously appeared between fuzzy TOPSIS and non-fuzzy MCDMs (e.g., WSM and TOPSIS) because the inter-annual variability in effectiveness was considered only with fuzzy TOPSIS. Then, robust prioritizations were derived based on 18 rankings from nine decadal periods of RCP4.5 and RCP8.5. For more robust rankings, five DMCU approaches using the rankings from fuzzy TOPSIS were derived. This framework combining fuzzy TOPSIS with DMCU approaches can be rendered less controversial among stakeholders under complete uncertainty of changing environments.

Assessing climate change vulnerability with group multi-criteria decision making approaches

This study developed an approach to assess the vulnerability to climate change and variability using various group multi-criteria decision-making (MCDM) methods and identified the sources of uncertainty in assessments. MCDM methods include the weighted sum method, one of the most common MCDM methods, the technique for order preference by similarity to ideal solution (TOPSIS), fuzzy-based TOPSIS, TOPSIS in a group-decision environment, and TOPSIS combined with the voting methods (Borda count and Copeland’s methods). The approach was applied to a water-resource system in South Korea, and the assessment was performed at the province level by categorizing water resources into water supply and conservation, flood control and water-quality sectors according to their management objectives. Key indicators for each category were profiled with the Delphi surveys, a series of questionnaires interspersed with controlled opinion feedback. The sectoral vulnerability scores were further aggregated into one composite score for water-resource vulnerability. Rankings among different MCDM methods varied in different degrees, but noticeable differences in the rankings from the fuzzy- and non-fuzzy-based methods suggested that the uncertainty with crisp data, rather widely used, should be acknowledged in vulnerability assessment. Also rankings from the voting-based methods did not differ much from those from non-voting-based (i.e., average-based) methods. Vulnerability rankings varied significantly among the different sectors of the water-resource systems, highlighting the need to assess the vulnerability of water-resource systems according to objectives, even though one composite index is often used for simplicity.

A phase II study of hypofractionated proton therapy for prostate cancer.

Abstract Background. Hypofractionated radiotherapy potentially offers therapeutic gain for prostate cancer. We investigated the feasibility of hypofractionated proton therapy (PT). Material and methods. Eighty-two patients with biopsy-proven T1-3N0M0 prostate adenocarcinoma and no history of androgen deprivation therapy were randomly assigned to five different dose schedules: Arm 1, 60 CGE (cobalt gray equivalent = proton dose in Gy × 1.1)/20 fractions/5 weeks; Arm 2, 54 CGE/15 fractions/5 weeks; Arm 3, 47 CGE/10 fractions/5 weeks; Arm 4, 35 CGE/5 fractions/2.5 weeks; or Arm 5, 35 CGE/5 fractions/5 weeks. Results. The median follow-up duration was 42 months (11–52 months). The acute GI and GU grade ≥ 2 toxicity rates were 0 and 5%, respectively. The late GI and GU grade ≥ 2 toxicity rates were 16% and 7%, respectively. The best arm for acute GU toxicity was Arm 3, while that for late GI toxicity was Arm 2 in which none had grade ≥ 2 toxicity. The four-year American Society for Therapeutic Radiology and Oncology and Nadir + 2ng/ml BCF free survival (BCFFS) rates were 85% and 86%, respectively. Conclusions. Hypofractionated PT for patients with prostate adenocarcinoma as used in this study is feasible with an acceptable toxicity profile. As the BCFFS rates do not seem to be inferior to those produced using conventional fractionation, the application of hypofractionated PT may save patients time and money.

Identification of Prognostic Risk Factors for Transient and Persistent Lymphedema after Multimodal Treatment for Breast Cancer

Purpose The purpose of this study is to identify risk factors for transient lymphedema (TLE) and persistent lymphedema (PLE) following treatment for breast cancer. Materials and Methods A total of 1,073 patients who underwent curative breast surgery were analyzed. TLE was defined as one episode of arm swelling that had resolved spontaneously by the next follow-up; arm swelling that persisted over two consecutive examinations was considered PLE. Results At a median follow-up period of 5.1 years, 370 cases of lymphedema were reported, including 120 TLE (11.2%) and 250 PLE (23.3%). Initial grade 1 swelling was observed in 351 patients, of which 120 were limited to TLE (34%), while the other 231 progressed to PLE (66%). All initial swelling observed in TLE patients was classified as grade 1. In multivariate analysis, chemotherapy with taxane and supraclavicular radiation therapy (SCRT) were associated with development of TLE, whereas SCRT, stage III cancer and chemotherapy with taxane were identified as risk factors for PLE (p < 0.05). The estimated incidence of TLE among initial grade 1 patients was calculated using up to three treatment-related risk factors (number of dissected axillary lymph nodes, SCRT, and taxane chemotherapy). The approximate ratios of TLE and PLE based on the number of risk factors were 7:1 (no factor), 1:1 (one factor), 1:2 (two factors), and 1:3 (three factors). Conclusion One-third of initial swelling events were transient, whereas the other two-thirds of patients experienced PLE. Estimation of TLE and PLE based on known treatment factors could facilitate prediction of this life-long complication.

Iterative Framework for Robust Reclaimed Wastewater Allocation in a Changing Environment Using Multi-Criteria Decision Making

In this study, an iterative framework for robust reclaimed wastewater allocation (IFRWA) was developed to consider multiple climate change scenarios using multi-criteria decision making (MCDM) methods. Each iteration begins with the assumption that an additional unit of water quantity is allocated to reclaimed wastewater (RWW) sites. Based on these allocation conditions, hydrologic simulations are performed and evaluated using the incremental alternative evaluation index (IAEI) to rank the best sites for each unit water quantity. The minimax regret strategy is employed to consider the uncertainty inherent in the climate change scenarios. The consequent robust ranking of the IAEIs is applied to determine the final allocation of the unit water quantity in a given iteration. This iteration continues until the total allocated water quantity satisfies the maximum available capacity of RWW for use in the studied watershed. Our results show that this incremental and robust framework can be used to determine the reasonable capacities of RWW at multiple sites within the watershed by considering various aspects of RWW use, including the water quantity and the socio-economic aspects of decision making. A choice and concentration strategy based on IAEIs should be employed to achieve the maximum utility considering the physical constraints (capacity and cost). If economic considerations, such as the cost of construction and management, are included, this framework can be applied to real problems.

Integrated assessment of climate change and urbanization impact on adaptation strategies: a case study in two small Korean watersheds

This study develops an integrated approach to assess climate change and urbanization impacts on adaptation strategies in watersheds. We considered the two adaptation strategies for two small watersheds in Korea: the redevelopment of an existing reservoir and the reuse of highly treated wastewater treatment plant (WWTP) effluent. Climate change scenarios were obtained by statistically downscaling the predicted precipitation and temperature with a global climate model (A1B and A2), and urbanization scenarios were derived by estimating the impervious area ratios with an impervious cover model. With the climate change and urbanization scenarios, we used the Hydrological Simulation Program-Fortran model to derive the flow and biochemical oxygen demand (BOD) concentration (conc.) duration curves, and calculate the numbers of days satisfying environmental requirement for instreamflow and the target BOD conc. Climate change reduced the effectiveness of the adaptation strategies with respect to low flow and BOD conc., whereas urbanization generally increased their effectiveness. Climate change had a greater impact on the effectiveness of the adaptation strategies for BOD conc. than for low flow, whereas urbanization had a greater impact on low flow. Comparing impacts of two strategies, a larger decrease in the effectiveness was observed for the WWTP effluent reuse strategy in response to climate change and urbanization. However, the consistent trends cannot be found with ease if climate change and urbanization happens jointly.