This study investigates how to properly downscale the coupled general circulation model (CGCM) ensemble prediction dynamically more efficiently than conventional method. Specifically, the ensemble ...seasonal prediction skill of dynamically downscaled precipitation over South Korea is evaluated by comparing two experiments. The first experiment (EXP1) involves conventional ensemble forecasts. Five ensemble members (EMs) are downscaled dynamically with initial and lateral boundary conditions obtained from the outputs of five CGCM EMs. The results of each EM are averaged for ensemble prediction utilizing a simple composite method. The second experiment (EXP2) is the same as EXP1, but the initial and lateral boundary conditions are obtained by arithmetically averaging the outputs of the five CGCM EMs. Therefore, five integrations are carried out for the EXP1, but only one integration is performed for the EXP2. The results show that EXP2 simulates closer to the observed precipitation than EXP1. This improvement is attributed to the strongly simulated upper zonal wind that can influence the vertically integrated moisture flux convergence. EXP2 shows comparable or better performance in simulating the interannual variability of summer precipitation than EXP1. Unlike conventional methods, such as EXP1, EXP2 provides a prediction in a single integration, and the prediction is similar to or even better than the one obtained conventionally. Hence, EXP2 can be a powerful means to drastically reduce the prediction time by reducing the number of ensemble integration to just one.
ABSTRACT
An investigation was conducted to optimize the application of the multi‐model ensemble (MME) technique for statistical downscaling using 1‐ to 6‐month lead hindcasts obtained from six ...operational coupled general circulation models (GCMs) participating in the APEC Climate Center (APCC) MME prediction system. Three different statistical downscaling MME methods (SDMMEs) were compared and estimated over South Korea. The study results revealed that under the same number of ensemble members, simple changes in the statistical downscaling method, such as an applicative order or a type of MME, can help to improve the predictability. The first method, the conventional technique, performed MME using data downscaled from the single‐model ensemble means of each GCM (SDMME‐Sm), whereas the second and third methods, newly designed in this study, calculated the simple ensemble mean (SDMME‐Ae) and the weighted ensemble mean (SDMME‐We) after statistical downscaling for each member of all model ensembles. These three methods were applied to predict temperature and precipitation for the 6‐month summer‐fall season over 23 years (1983–2005) at 60 weather stations over South Korea. The predictors were variables from hindcasts integrated by the six coupled GCMs. According to the analysis, both SDMME‐Ae and SDMME‐We showed increased predictability compared with SDMME‐Sm. In particular, SDMME‐We showed more significant improvement in long‐term prediction. In addition, in order to assess the dependence of predictability on the number of downscaled ensemble members and the type of MME, an additional experiment was performed, the results of which revealed that the model performance was closely related to the number of downscaled ensemble members. However, after approximately 30 ensemble members, the predictive skills became rapidly saturated when using the SDMME‐Ae method. SDMME‐We overcame the limited skills that can be achieved by merely increasing the number of downscaled ensemble members, thereby improving the performance.
ABSTRACT
An impact of global warming on the first‐flowering date (FFD) of cherry, peach and pear in north‐eastern Asia are investigated using the Korean national scenario. For the study, we used the ...dynamically downscaled daily temperature with 12.5 km horizontal resolution derived from five regional climate models (RCMs) under the same lateral forcing from HadGEM2‐AO on the basis of Historical (1981–2010) and four Representative Concentration Pathway (RCP) (2021–2100) scenarios. According to our analysis of the Historical simulations, the five RCMs and phenological model have good capability in simulating temperature and FFD with uncertainties of about 2.4–3.4 °C and 8.4–13.9 days, respectively, while well reflecting the topographical effect. On the basis of the highest emission scenario (RCP8.5), the temperature increments of 4.8 °C induce an acceleration in blooming rate, thereby advancing the FFDs of cherry, peach and pear by the end of the 21st century by about 14.5, 15.8 and 14.5 days, respectively, compared with the current reference simulation (Historical). We found high availability of the Korean national scenarios with moderate reliability. We believe that the next generation of the Korean national downscaling project considering diverse lateral forcing will offer better performance and more useful projections to end users.
In this study, the projected regional precipitation changes over northeast Asia (NEA) during early summer May–July (MJJ) for the late twenty-first century (2071–2100) were investigated using a ...high-resolution regional climate model (WRF3.4) based on the representative concentration pathways (RCPs) induced by the global circulation model (HadGEM2-AO). The increased horizontal resolution of the regional model with a 12.5-km horizontal resolution enabled it to reproduce the terrain-following features reasonably well compared to low-resolution reanalysis and HadGEM2-AO model data. The results of a regionally downscaled historical (1981–2010) experiment (D_Historical) demonstrated the model’s ability to capture the spatial and temporal variations of rainband migrating meridionally during MJJ over NEA. According to the regional model projection, intensive precipitation will increase and the rainband will affect the Korean Peninsula approximately 10 days earlier than in the D_Historical cases in both RCP4.5 and RCP8.5 (2071–2100). The precipitation will also increase in most of the domain, particularly in the southern Korean Peninsula and Kyushu, Japan. These increases in precipitation are attributed to increases in the northward moist transport coming from the lower latitudes and moist static instability in the lower atmosphere. According to this study, the convective precipitation contributes mainly to the increase in total precipitation. On the other hand, the large-scale nonconvective precipitation related to the stationary front will not change significantly but even tends to decrease approximately from the middle of July. The extreme precipitation intensity is also projected to increase by at least 22% (38%) in RCP4.5 (RCP8.5).
This study investigates the effects of the North Pacific sea surface temperature (NP SST) anomalies on the East Asian winter temperature (TEA), and the relationship between the Arctic Oscillation ...(AO) and NP SST anomalies in association with TEA. Time‐lagged correlation analysis revealed that the third mode of the September–October–November (SON) mean NP SST (“SON SST 3rd mode”) and the AO index for November (“Nov AO”) are closely related to TEA, and further that the first and second modes of NP SST are associated with the Pacific Decadal Oscillation (PDO) and Pacific North America (PNA) patterns, respectively. This study reveals that when the SON SST 3rd mode and Nov AO have a positive (negative) phase, the intensity of the Siberian High weakens (strengthens), which in turn weakens (strengthens) the East Asian winter monsoon (EAWM), resulting in a warm (cold) winter in East Asia. Our results suggest that the North Pacific Ocean signals influence the AO, which is one of the most pronounced Northern Hemispheric atmospheric global patterns. Such an influence in turn governs the continental‐scale circulation over Siberia and affects the subsequent local climate variation over the East Asia regions.
Key Points
The 3rd mode of North Pacific SON SST is correlated with November AO
The SST mode and Nov. AO are also related to East Asian Winter Monsoon
Atmospheric circulations related to the SST mode and AO are consistent
Studies of a modified XELIRI (mXELIRI; capecitabine plus irinotecan) regimen suggest promising efficacy and tolerability profiles in the first-line and second-line settings. Therefore, we aimed to ...compare the efficacy and safety of the mXELIRI regimen with that of standard FOLFIRI (leucovorin, fluorouracil, and irinotecan), with or without bevacizumab in both regimens, as a second-line therapy for metastatic colorectal cancer.
We did a multicentre, open-label, randomised, non-inferiority, phase 3 trial. We enrolled patients from 98 hospitals in Japan, China, and South Korea who were aged 20 years or older with histologically confirmed and unresectable colorectal adenocarcinoma, and who had withdrawn from first-line chemotherapy for metastatic colorectal cancer. We randomly assigned patients (1:1) to receive either mXELIRI with or without bevacizumab (irinotecan 200 mg/m2 intravenously on day 1 plus oral capecitabine 800 mg/m2 twice daily on days 1–14, repeated every 21 days, with or without bevacizumab 7·5 mg/kg intravenously on day 1) or FOLFIRI with or without bevacizumab (irinotecan 180 mg/m2 intravenously on day 1, leucovorin 200 mg/m2 intravenously on day 1, fluorouracil 400 mg/m2 intravenously on day 1, and a 46-h continuous intravenous infusion of fluorouracil 2400 mg/m2, repeated every 14 days, with or without the addition of bevacizumab 5 mg/kg intravenously on day 1) via a centralised electronic system. We used the minimisation method to stratify randomisation by country, Eastern Cooperative Oncology Group performance status, number of metastatic sites, previous oxaliplatin treatment, and concomitant bevacizumab treatment. Patients and clinicians were not masked to the allocated treatment. The primary endpoint was overall survival analysed on an intention-to-treat basis with a non-inferiority upper margin of 1·30 for the hazard ratio (HR). This study is registered with ClinicalTrials.gov, number NCT01996306, and is ongoing but no longer recruiting participants.
Between Dec 2, 2013, and Aug 13, 2015, 650 patients were enrolled and randomly assigned to receive mXELIRI with or without bevacizumab (n=326) or FOLFIRI with or without bevacizumab (n=324). After a median follow-up of 15·8 months (IQR 8·7–24·9), a total of 490 patients had died (242 in the mXELIRI with or without bevacizumab group and 248 in the FOLFIRI with or without bevacizumab group) and the median overall survival was 16·8 months (95% CI 15·3–19·1) in the mXELIRI group and 15·4 months (13·0–17·7) in the FOLFIRI group (HR 0·85, 95% CI 0·71–1·02; pnon-inferiority<0·0001). In the per-protocol safety population, the most common grade 3–4 adverse event was neutropenia (affecting 52 17% of 310 patients in the mXELIRI group and 133 43% of 310 in the FOLFIRI group). Incidences of grade 3–4 diarrhoea were higher in the mXELIRI group (22 7%) than in the FOLFIRI group (ten 3%). Serious adverse events were reported in 46 (15%) of 310 patients in the mXELIRI group and 63 (20%) of 310 in the FOLFIRI group. Two treatment-related deaths (one pneumonitis and one lung infection) were observed in the mXELIRI group and there was one treatment-related death (lung infection) in the FOLFIRI group.
mXELIRI with or without bevacizumab is well tolerated and non-inferior to FOLFIRI with or without bevacizumab in terms of overall survival. mXELIRI could be an alternative to FOLFIRI as a standard second-line backbone treatment for metastatic colorectal cancer, at least for Asian patient populations.
Chugai Pharmaceutical and F Hoffmann-La Roche.
ABSTRACT
The forecast capability of the first‐flowering date (FFD) over South Korea is evaluated using the seasonal (1‐ to 3‐month lead) prediction from the global Pusan National University (PNU) ...coupled general circulation model (CGCM) v1.1 and regional Weather Research and Forecast (WRF) v3.0 climate models. Gridded data with high spatial (3 km) and temporal (daily) resolution are produced using the physically based dynamical models. Dynamical downscaling is performed using WRF v3.0 with the lateral forcing from hourly outputs of PNU CGCM v1.1. Statistical correction is then used to eliminate systematic bias in the model output. The FFDs of cherry, peach and pear in South Korea are predicted for the decade of 1999–2008 by applying the corrected daily temperature predictions to the phenological thermal‐time model. The WRF v3.0 results reflect the detailed topographical effect, despite having cold and warm biases for warm and cold seasons, respectively. After applying the correction, the mean temperature for early spring (February to April) clearly represents the general pattern of observation, while preserving the advantages of dynamical downscaling. The FFD predictabilities for the three species of trees are evaluated in terms of qualitative, quantitative and categorical estimations. Although FFDs derived from the corrected WRF results well predicted the spatial distribution and the variation of observation, the prediction performance has no statistical significance or appropriate predictability. Even though the upcoming flowering phenology could not be accurately predicted, the present study approach may be helpful in obtaining detailed and useful information about FFD and regional temperature by accounting for physically based atmospheric dynamics.
Simulation and seasonal prediction of the cold surge characteristics over the Korean Peninsula by the Pusan National University CGCM (PNU CGCM), a participating model in Asia–Pacific Economic ...Cooperation Climate Center Multi-Model Ensemble Prediction System, are evaluated based on historical seasonal forecasts for 42 years (1980 − 2021). The PNU CGCM skillfully simulates the climatological characteristics of the cold surges of the non-blocking type (nB_CS), and of two blocking types (B_CS), particularly the Ural and Okhotsk blocking types (UR_CS and OK_CS). In both observation and the PNU CGCM simulations, nB_CS is the most frequent type of the cold surges over the Korean Peninsula. Duration and intensity of the nB_CSs are perfectly simulated. However, the number of occurrences and number of days are overestimated. In the model simulations, the number of occurrences and number of days of the UR_CS tend to be overestimated while those of the OK_CS tend to be underestimated. Meanwhile, for each type of cold surges, the difference in probability distributions of the simulated and observed cold surge duration and intensity is not statistically significant. Also, PNU CGCM skillfully simulates spatial–temporal evolution of the wave-train pattern causing the nB_CS, as well as spatial–temporal evolution of both B_CSs, associated with the blocking of the barotropic structure and the passage over the Korean Peninsula of trough of the baroclinic structure. Overall, seasonal predictions of the PNU CGCM are skillful for the wintertime total number of days with the cold surges, and mean intensity of the cold surges.
Crop growth models and remote sensing are useful tools for predicting crop growth and yield, but each tool has inherent drawbacks when predicting crop growth and yield at a regional scale. To improve ...the accuracy and precision of regional corn yield predictions, a simple approach for assimilating Moderate Resolution Imaging Spectroradiometer (MODIS) products into a crop growth model was developed, and regional yield prediction performance was evaluated in a major corn-producing state, Illinois, USA. Corn growth and yield were simulated for each grid using the Crop Environment Resource Synthesis (CERES)-Maize model with minimum inputs comprising planting date, fertilizer amount, genetic coefficients, soil, and weather data. Planting date was estimated using a phenology model with a leaf area duration (LAD)-logistic function that describes the seasonal evolution of MODIS-derived leaf area index (LAI). Genetic coefficients of the corn cultivar were determined to be the genetic coefficients of the maturity group included in Decision Support System for Agrotechnology Transfer (DSSAT) 4.6, which shows the minimum difference between the maximum LAI derived from the LAD-logistic function and that simulated by the CERES-Maize model. In addition, the daily water stress factors were estimated from the ratio between daily leaf area/weight growth rates estimated from the LAD-logistic function and that simulated by the CERES-Maize model under the rain-fed and auto-irrigation conditions. The additional assimilation of MODIS data-derived water stress factors and LAI under the auto-irrigation condition showed the highest prediction accuracy and precision for the yearly corn yield prediction (R2 is 0.78 and the root mean square error is 0.75 t ha-1). The present strategy for assimilating MODIS data into a crop growth model using minimum inputs was successful for predicting regional yields, and it should be examined for spatial portability to diverse agro-climatic and agro-technology regions.
The change of average winter precipitation in the South China Sea (SCS) since 1999 was investigated by analyzing the average precipitation between 1999 and 2014 and 1980–1993. The spatial ...distribution of the winter precipitation difference between the two periods showed that the negative anomalies were distributed from the equatorial eastern Pacific to the equatorial central Pacific, and the positive anomalies were distributed in the subtropical western Pacific, the Maritime Continent, and northern part of Australia, which is a typical spatial distribution of precipitation anomalies during La Niña events. In the tropical Pacific, the Walker circulation is intensified, in which air rises from the Maritime Continent and air in the tropical western Pacific descends at the equatorial central Pacific. Therefore, the change in sea surface temperature showed a typical La Niña pattern. In the East Asian regions, the local Hadley circulation in which air rises above the SCS and descends in the mid-latitudes of East Asia is intensified. This circulation is related to the anomalous pressure distribution of the west-high and east-low pattern in East Asia and the strengthening of the East Asian winter monsoon. In addition, this result is in-line with increased snow depth in mid-latitude East Asia in recent years.
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