Variation of Hydro-Meteorological Variables in Korea

Nkomozepi, Temba,Chung, Sang-Ok,Kim, Hyun-Ki 경북대학교 농업생명과학대학 2014 Current Research on Agriculture and Life Sciences Vol.32 No.3

The variability and temporal trends of the annual and seasonal minimum and maximum temperature, rainfall, relative humidity, wind speed, sunshine hours, and runoff were analyzed for 5 major rivers in Korea from 1960 to 2010. A simple regression and non-parametric methods (Mann-Kendall test and Sen's estimator) were used in this study. The analysis results show that the minimum temperature (Tmin) had a higher increasing trend than the maximum temperature (Tmax), and the average temperature increased by about 0.03˚C yr.-1. The relative humidity and wind speed decreased by 0.02% yr-1 and 0.01m s-1yr-1, respectively. With the exception of the Han River basin, the regression analysis and Mann-Kendall and Sen results failed to detect trends for the runoff and rainfall over the study period. Rapid land use changes were linked to the increase in the runoff in the Han River basin. The sensitivity of the evapotranspiration and ultimately the runoff to the meteorological variables was in the order of relative humidity > sunshine duration > wind speed > Tmax > Tmin. Future studies should investigate the interaction of the variables analyzed herein, and their relative contributions to the runoff trends.

Variation of Hydro-Meteorological Variables in Korea

Nkomozepi, Temba,Chung, Sang-Ok,Kim, Hyun-Ki Institute of Agricultural Science and Technology 2014 慶北大農學誌 Vol.32 No.3

The variability and temporal trends of the annual and seasonal minimum and maximum temperature, rainfall, relative humidity, wind speed, sunshine hours, and runoff were analyzed for 5 major rivers in Korea from 1960 to 2010. A simple regression and non-parametric methods (Mann-Kendall test and Sen's estimator) were used in this study. The analysis results show that the minimum temperature ($T_{min}$) had a higher increasing trend than the maximum temperature ($T_{max}$), and the average temperature increased by about $0.03^{\circ}C\;yr.^{-1}$. The relative humidity and wind speed decreased by $0.02%\;yr^{-1}$ and $0.01m\;s^{-1}yr^{-1}$, respectively. With the exception of the Han River basin, the regression analysis and Mann-Kendall and Sen results failed to detect trends for the runoff and rainfall over the study period. Rapid land use changes were linked to the increase in the runoff in the Han River basin. The sensitivity of the evapotranspiration and ultimately the runoff to the meteorological variables was in the order of relative humidity > sunshine duration > wind speed > $T_{max}$ > $T_{min}$. Future studies should investigate the interaction of the variables analyzed herein, and their relative contributions to the runoff trends.

Variation and Trends of Irrigation Requirements of Rice Paddies in Korea

Nkomozepi, Temba Darlington,Chung, Sang-Ok Institute of Agricultural Science and Technology 2013 慶北大農學誌 Vol.31 No.4

Understanding the temporal variability of agricultural parameters derived from historical climate data is important for planning in agriculture. Therefore, this study assessed the magnitude and recent trends of the transpiration ratio defined as the crop water use per harvested yield for the period from 1980 to 2010. The crop water use was estimated using the Food and Agriculture Organization's Crop Wat model for eight administrative provinces in Korea. The temporal trends and spatial uncertainty were explored using the Mann-Kendall and Theil Sen's methods. The regional average rice yield was $6.31t\;ha^{-1}$(range 5.9 to $6.9t\;ha^{-1}$). The results showed that the rice yield in Korea increased by $26kg\;ha^{-1}yr^{-1}$. Overall, the regional average transpiration ratio was $1,298m^3t^{-1}$ (range 1,162 to $1,470m^3t^{-1}$). From 1980 to 2010, the transpiration ratio decreased by $8.2m^3t^{-1}$ (range 2.7 to $14.4m^3t^{-1}$), largely as a result of the increasing yield. The statistical approach to historical data used in this study also provides a basis for simulating the future transpiration ratio.

기후변화에 따른 대구지역 지하배수 전망

Nkomozepi, Temba,Chung, Sang-Ok 경북대학교 농업생명과학대학 2012 Current Research on Agriculture and Life Sciences Vol.30 No.2

Over the last century, drainage systems have become an integral component of agriculture. Climate observations and experiments using General circulation models suggest an intensification of the hydrologic cycle due to climate change. This study presents hydrologic simulations assessing the potential impact of climate change on subsurface drainage in Daegu, Republic of Korea. Historical and Long Ashton Research Station weather generator perturbed future climate data from 15 general circulation models for a field in Daegu were ran into a water management simulation model, DRAINMOD. The trends and variability in rainfall and Soil Excess Water () were assessed from 1960 to 2100. Rainfall amount and intensity were predicted to increase in the future. The predicted annual subsurface drainage flow varied from -35 to 40 % of the baseline value while the varied from -50 to 100%. The expected increases in subsurface drainage outflow require that more attention be given to soil and water conservation practices.

기후변화에 따른 우리나라의 수문 기상학적인 불확실성

템바은코모제피 ( Temba Nkomozepi ),정상옥 ( Chung Sang-ok ) 한국농공학회 2013 한국농공학회 학술대회초록집 Vol.2013 No.-

The impact of changes in both temperature and rainfall due to climate change on surface water resources is of utmost importance in hydro-meteorology research. In this study, 4 hydro-meteorological models from the Rainfall Runoff Library were used to model the impact of climate change on runoff in streams for 5 major river basins in the Republic of Korea. Future projections of climate for the time periods of 1971-2000 (baseline), 2021-2040 (2030s), 2051-2070 (2060s) and 2081-2099 (2090s), were derived from 12 General Circulation Models (GCMs) and 3 representative concentration pathways (RCP). GCM outputs were statistically adjusted and downscaled using Long-Ashton Research Station Weather Generator (LARS-WG) and the hydro-meteorological models were well calibrated and verified for the period from 1999 to 2009. The study showed that while the uncertainty in future runoff is largely due to climate scenarios, significant uncertainty in predicting the future runoff can be attributed to hydro-meteorological models and that uncertainty is greater for the baseline than for future periods. In summary, the surface runoff and stream-flow were forecasted to increase by up to 100% by 2100 and the highest increases were noted for the Han River basin. This study presents a method to predict future stream-flow by taking into account the hydro-meterological model and climate based uncertainty.

기후변화에 따른 논 전환 밭에서의 지하배수 설계기법

템바은코모제피 ( Temba Nkomozepi ),정상옥 ( Chung Sang-ok ) 한국농공학회 2012 한국농공학회 학술대회초록집 Vol.2012 No.-

The demand of rice in the Republic of Korea is on a declining trend as the diet is becoming more diversified. Many paddy fields have to be converted to upland cultivation to meet the demand for alternative foods. The objective of this study is to assess the possible impacts of climate change on the future design standards and on currently installed drainage infrastructure in the republic of Korea. Historical climate data and Long Ashton Research Station-Weather Generator (LARS-WG) generated meteorological data from 15 General circulation models (GCMs) for a field in daegu were input into DRAINMOD. The water table management simulation model DRAINMOD was then used to simulate excess soil water (SEW30) and drain outflow. The trends in daily, annual mean and annual maximum rainfall and SEW30 were detected from 1960 to 2100. The statistical distribution of the maximum rainfall will shift in the future and more intense daily rainfall is likely to occur in the future. The annual SEW30 was simulated to increase in the future. There is a significant possibility that current drain spacing, depth and pipe diameters used in subsurface drainage may not be fully sufficient to cater for upland fields in the future. The study presents a scientific method to assess the impact of predicted climate change and would help engineers, hydrologists and planners to devise strategies for the efficient use of freshwater resources.

Variation and Trends of Irrigation Requirements of Rice Paddies in Korea

Temba Darlington Nkomozepi,Sang-Ok Chung 경북대학교 농업생명과학대학 2013 Current Research on Agriculture and Life Sciences Vol.31 No.4

Understanding the temporal variability of agricultural parameters derived from historical climate data is important for planning in agriculture. Therefore, this study assessed the magnitude and recent trends of the transpiration ratio defined as the crop water use per harvested yield for the period from 1980 to 2010. The crop water use was estimated using the Food and Agriculture Organization’s Crop Wat model for eight administrative provinces in Korea. The temporal trends and spatial uncertainty were explored using the Mann-Kendall and Theil Sen’s methods. The regional average rice yield was 6.31 t ha-1(range 5.9 to 6.9 t ha-1). The results showed that the rice yield in Korea increased by 26 kg ha-1yr-1. Overall, the regional average transpiration ratio was 1,298 m3 t-1 (range 1,162 to 1,470 m3 t-1). From 1980 to 2010, the transpiration ratio decreased by 8.2 m3 t-1 (range 2.7 to 14.4 m3 t-1), largely as a result of the increasing yield. The statistical approach to historical data used in this study also provides a basis for simulating the future transpiration ratio.

기후변화에 따른 논 필요수량의 불확실성 분석

은코모제피템바 ( Temba Nkomozepi ),윤동균 ( Dong-koun Yun ),정상옥 ( Sang-ok Chung ) 한국농공학회 2011 한국농공학회 학술대회초록집 Vol.2011 No.-

최근 기후변화에 대한 관심이 많아졌으며, 관련 연구도 많이 수행되고 있다. 우리나라의 경우에는 기후변화가 수자원에 미치는 영향에 대하여서는 활발한 연구가 수행되어 오고 있으나 농업용수에 미치는 영향에 대한 연구는 매우 미흡한 실정이다. 일반적으로 미래 기후예측 자료는 IPCC가 제공하는 SRES 시나리오별 GCM 모형 예측값을 이용하여 상세화한 결과를 이용한다. 그러나 이러한 기후예측치는 여러 가지 불확실성을 내포하고 있다. 첫째는 SRES 배출가스 시나리오의 불확실성, 둘째는 GCM 모형의 한계로 인한 불확실성, 둘째는 GCM 모형의 한계로 인한 불확실성, 셋째는 큰 격자망인 GCM 자료를 작은 격자망으로 상세화하는 과정에서의 불확실성이 있다. 따라서 보다 신뢰성 있는 결과를 위하여서는 여러 가지의 SRES 시나리오와 여러 가지 GCM 예측값을 이용하여 많은 모의발생을 하여 분석하여야 한다. 본 연구의 범위와 내용은 대구지역에 대하여 IPCC 4차 평가보고서에서 이용된 세 가지 시나리오 (A2, A1B, B1)에 대한 13개 GCM 모형예측치를 기본으로 하여 상세화한 기후예측 값을 기준년도 (1961-1990)와 미래 20년간 (2020s, 2050s, 2080s)의 월 평균 값과 비교하여 그 불확실성을 분석하였다. 또한 예측된 기후자료를 이용하여 벼의 필요수량을 산정하여 비교분석하여 그 불확실성을 분석하였다. 본 연구에서는 IPCC 4차 평가보고서에 사용된 13개 GCM 모형과 세가지 SRES 배출 시나리오에 대한 월 평균 기후예측 자료를 이용하여 대구지역에 대한 기후예측과 논 관개요구량의 불확실성을 분석하였다. 그 결과 각 GCM은 미래 기후예측에서 상당한 불확실성을 나타내었으며, 특히 시간이 지날수록 불확실성이 크게 증가하였다. 또한 작물 증발산량은 비슷하게 시간이 갈수록 증가하는 것으로 나타났으며, 2080년에는 불확실성이 크게 증가하였다. 관개요구량에 대한 불확실성은 2020s A2 시나리오가 가장 컸으며 (-9% 내지 14%), 기준년도 대비 가장 큰 증가량은 CM2.1 모형이 2080s A2 시나리오에서 24%를 나타내었다.

기후변화가 짐바브웨 옥수수 관개요구량에 미치는 영향

은코모제피템바 ( Temba Nkomozepi ),정상옥 ( Sang-ok Chung ) 한국농공학회 2010 한국농공학회 학술대회초록집 Vol.2010 No.-

Climate change is inevitable and is expected over the next century. it will affect ecosystems and access to natural resources such as fertile land and water. Studies have shown that southern Africa is one of the most vulnerable regions to climate change due to its low economic development and the diversity of local conditions. In Zimbabwe, the agricultural sector is vulnerable marginally productive areas probably shifting to non-agricultural use. The purpose of this study therefore is to assess spatial and temporal impacts of climate change on corn net irrigation requirements in a high corn producing area in Zimbabwe. Future changes in climate projected by a general circulation model (HadCM3) were applied to a baseline climatology (change factor methodology) based on 2 selected scenarios (A2b and B2a) of the The Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (IPCC SRES). CROPWAT computer program was used to estimate evapotranspiration and irrigation water requirements using the Penman-Monteith equation for the 2020s, 2050s and 2080s time periods. A GIS was used to map spatial changes in irrigation water requirement for the mentioned time periods. The maps highlight a significant predicted increase in aridity and irrigation need. Modelling of irrigation water requirements predicted a proportional increase of between 97 and 121 percent by the 2080s based on an observed 1961-1990 baseline. The increase in irrigation demand can be attributed to ambient temperature and rainfall trends. Anticipatory adaptive measures must be planned and implemented in agricultural infrastructure development and research on climate change impact mitigatory measures for the study region.

기후변화에 따른 짐바브웨 옥수수 필요수량의 불확실성 분석

은코모제피템바 ( Temba Nkomozepi ),정상옥 ( Sang-ok Chung ) 한국농공학회 2011 한국농공학회 학술대회초록집 Vol.2011 No.-

Most climate projection studies acknowledge that the earth will experience a warming trend over the 21st century. However, mesoscale water mass and energy budgets that influence regional water demand, do not respond to approximated global averages but rather to regional changes which are spatially and temporally heterogeneous and uncertain. General Circulation Model (GCM) data have been used in most impact assessments. The objective of this paper was to assess the variation of future maize irrigation water requirements estimated from various GCMs in Zimbabwe’s natural agro-ecological region II. Data were extracted from 13 GCMs for A2, A1B and B1 SRES scenarios, downscaled using the change factor method and analyzed. The CROPWAT model was used to generate crop water requirement, effective rainfall and the crop water requirement. Reference evapotranspiration and the crop water requirement were predicted to increase in the future periods (2020s, 2050s and 2080s). Rainfall predictions from different GCMs exhibited high variability. The maize irrigation water requirement was predicted to significantly increase for future periods. Regression analysis was performed on the trends of predicted water requirement over time using the Pearson’s product moment correlation coefficient. It was concluded that multiple models should be used where possible to avoid inappropriate planning or adaptation responses particularly in the short term.