CMIP5 GCMs과 추정 방법에 따른 우리나라 기준증발산량 평가

박지훈,조재필,이은정,정임국,Park, Jihoon,Cho, Jaepil,Lee, Eun-Jeong,Jung, Imgook 한국농촌계획학회 2017 농촌계획 Vol.23 No.4

The main objective of this study was to assess reference evapotranspiration based on multiple GCMs (General Circulation Models) and estimation methods. In this study, 10 GCMs based on the RCP (Representative Concentration Pathway) 4.5 scenario were used to estimate reference evapotranspiration. 54 ASOS (Automated Synoptic Observing System) data were constructed by statistical downscaling techniques. The meteorological variables of precipitation, maximum temperature and minimum temperature, relative humidity, wind speed, and solar radiation were produced using GCMs. For the past and future periods, we estimated reference evapotranspiration by GCMs and analyzed the statistical characteristics and analyzed its uncertainty. Five methods (BC: Blaney-Criddle, HS: Hargreaves-Samani, MK: Makkink, MS: Matt-Shuttleworth, and PM: Penman-Monteith) were selected to analyze the uncertainty by reference evapotranspiration estimation methods. We compared the uncertainty of reference evapotranspiration method by the variable expansion and analyzed which variables greatly influence reference evapotranspiration estimation. The posterior probabilities of five methods were estimated as BC: 0.1792, HS: 0.1775, MK: 0.2361, MS: 0.2054, and PM: 0.2018. The posterior probability indicated how well reference evapotranspiration estimated with 10 GCMs for five methods reflected the estimated reference evapotranspiration using the observed data. Through this study, we analyzed the overall characteristics of reference evapotranspiration according to GCMs and reference evapotranspiration estimation methods The results of this study might be used as a basic data for preparing the standard method of reference evapotranspiration to derive the water management method under climate change.

FAO Penman-Monteith 기준증발산식 민감도 분석

임창수 한국수자원학회 2023 한국수자원학회논문집 Vol.56 No.4

Estimating the evapotranspiration is very important factor for effective water resources management, and FAO Penman-Monteith (FAO P-M) model has been applied for reference evapotranspiration estimation by many researchers. However, because various input data are required for the application of FAO P-M model, understanding the effect of each input data on FAO P-M model is necessary. Therefore, in this study, for 56 study stations located in South Korea, the effects of 8 meteorological factors (maximum and minimum temperature, wind speed, relative humidity, solar radiation, vapor pressure deficit, net radiation, ground heat flux), energy and aerodynamic terms of FAO P-M model, and elevation on FAO P-M reference evapotranspiration (RET) estimation were analyzed. The relative sensitivity analysis was performed to determine how 10% increment of each specific independent variable affects a reference evapotranspiration under given set of condition that other independent variables are unchanged. Furthermore, to select the 5 representative stations and perform the monthly relative sensitivity analysis for those stations, 56 study stations were classified into 5 clusters using cluster analysis. The study results showed that net radiation was turned out to be the most sensitive factor in 8 meteorological factors for 56 study stations. The next most sensitive factor was relative humidity, solar radiation, maximum temperature, vapor pressure deficit and wind speed, followed by minimum temperature in order. Ground heat flux was the least sensitive factor. In case of ground surface condition, elevation showed very low positive relative sensitivity. Relativity sensitivities of energy and aerodynamic terms of FAO P-M model were 0.707 for energy term and 0.293 for aerodynamic term respectively, indicating that energy term was more contributable than aerodynamic term for reference evapotranspiration. The monthly relative sensitivities of meteorological factors showed the seasonal effects, and also the relative sensitivity of elevation showed different pattern each other among study stations. Therefore, for the application of FAO P-M model, the seasonal and regional sensitivity differences of each input variable should be considered. 증발산량을 산정하는 것은 수자원 관리에서 매우 중요한 요소이고, 많은 연구자들에 의해서 FAO Penman-Monteith (FAO P-M) 식이 기준증발산량을 산정을 위해 적용되고 있다. 하지만 FAO P-M 식에는 다양한 입력 변수들이 적용되어서, 이들 입력변수들의 영향력을 파악하는 것은 필요하다. 따라서 본 연구에서는 우리나라 56개 연구지역을 대상으로 8개의 기상요소들(최고기온, 최저기온, 풍속, 상대습도, 일사량, 증기압부족, 순복사량, 지중열유동)과 FAO Penman-Monteith (FAO P-M) 기준증발산식의 에너지항과 공기동력항, 그리고 고도의 변화에 따른 FAO P-M 기준증발산량 산정에 미치는 영향을 분석하였다. 이를 위해 다른 변량들은 고정한 상황에서 각 특정 변량을 10% 증가시킴에 따른 기준증발산량의 변화를 평가하기 위해 상대 민감도분석을 실시하였다. 또한 5개 대표 지역을 선정하여 그 지역들에 대해서 월별 민감도분석을 실시하고자 군집분석을 이용하여 56개 연구지역을 5개로 분류하였다. 분석결과에 의하면 56개 연구지역에서 8개의 기상요소 중에서 순복사량이 가장 민감한 것으로 나타났고, 다음으로 상대습도, 일사량, 최고기온, 증기압부족, 풍속, 최저기온 순으로 나타났다. 지중열유동은 가장 덜 민감한 요소인 것으로 나타났다. 지표면 특성의 경우, 고도는 매우 낮은 양의 상대 민감도를 보였다. FAO P-M 기준증발산식의 에너지항과 공기동력항의 상대적 민감도는 에너지항이 0.707, 공기동력항이 0.293을 보여서 에너지항이 공기동력항보다 기준증발산량 산정에 기여도가 더 큰 것으로 나타났다. 월별 민감도분석에 의하면 기상요소별 민감도는 계절적인 영향을 보이는 것으로 나타났고, 고도의 상대민감도는 지역 간 서로 다른 양상을 보였다. 따라서 FAO P-M 식 적용을 위해서는 입력변수의 지역적, 계절적 민감도 차이를 고려해야할 것으로 판단된다.

우리나라 기준 증발산량 산정을 위한 Hargreaves 계수 산정

이길하(Lee Khil-Ha),박재현(Park Jae-Hyeon) 대한토목학회 2008 대한토목학회논문집 B Vol.28 No.6B

기상자료가 부족하거나 결측인 지역의 기준 증발산량 산정을 위해서는 Hargreaves 공식의 매개변수 추정을 수행할 필요가 있다. 본 연구에서는 우리나라 전역에 걸쳐 1997년-2006년 기상자료를 바탕으로 Hargreaves 공식을 이용하여 기준 증발산량(이하 ETo)을 산정하였다. 각 지점별로 PM공식에 의해 산정한 값을 증발산량의 정해로 가정하여 Hargreaves 매개변수를 지점별로 추정하였다. 최소의 오차가 발생하도록 Hargreaves 계수를 조정한 후 Root Mean Square Error와 Nash Sutcilffe Coefficient of Efficiency분석을 통하여 추정효율이 크게 향상되는 것을 알 수 있었다. 또한 추정된 매개변수를 바탕으로 기온 자료만의 의한 Hargreaves 증발산량을 추정할 수 있도록 일반화된 하나의 회귀직선을 도출하여 보았다. 온도­Hargreaves 계수의 선형 상관관계를 이용한 Hargreaves 계수의 일반화에서는 개선의 여지가 있지만 만족스러운 결과를 보여주는 것으로 나타났다. 이 연구결과는 우리나라의 수자원, 관개분야 및 환경 운용에 많은 도움이 될 것으로 판단된다. In this study, the daily-based reference evapotranspiration was evaluated with Hargreaves equation at the 23 meteorological stations for the time period of 1997-2006. The Hargreaves coefficient was self-calibrated to give the best fit with Penman-Monteith evapotranspiration, being regarded as a reference. On the basis of the estimated parameter set, a generalized regression was conducted to estimate the Hargreaves evapotranspiration by just using temperature data. This study will contribute to water resources planning, irrigation schedule, and environmental management.

Reference Evapotranspiration Calculator Software를 이용한 기상관측소 기준증발산 추정

최원호(Choi Wonho),최민하(Choi Minha),오현제(Oh Hyunje),박주양(Park Jooyang) 대한토목학회 2010 대한토목학회논문집 B Vol.30 No.2B

Reference Evapotranspiration Calculator Software (REF-ET)는 ASCE 및 FAO 기준증발산량을 포함한 총 17개의 FAO Penman-Monteith (PM) 방정식의 연산을 동시에 수행할 수 있는 프로그램으로서, 본 연구에서는 REF-ET에 대한 상세한 소개와 함께 기상관측소의 관측지료를 이용하여 REF-ET의 효용성을 논하였다. REF-ET는 각종 PM 방정식들에 대한 시일 월 단위 모의와 지역적 특성의 반영 및 결측자료에 대한 보정 등이 가능하다. REF-ET를 이용하여 서울 기상관측소의 29년간 증발산량을 모의한 결과, 일복사량에 주로 좌우되는 FAO24-Rd 식과 1957-Makk 식의 상관계수가 각각 0.89와 0.88로 높게 나타났으며, 이는 소형증발접시를 이용한 기준증발산량 관측값이 공기 동력학적 증발량만을 주로 반영하기 때문인 것으로 사료된다. 또한 RMSE/bias 분석을 통해 기준증발산 방정식들에 의한 계산값이 증발접시로부터의 기준증발산량에 비해 다소 과대평가되는 현상을 나타내었으나, 이 경우에도 1957-Makk 식이 가장 정확한 것으로 나타났다. 일단위 시계열 분석시 1957-Makk 식은 여름철의 증발산량을 저평가하는 경향을 나타내었으나, 전체적으로 1.06 ㎜/day의 오차로 증발산량을 모의 가능하였다. 차후 기상관측자료의 정확도를 높이는 연구들과 REF-ET를 병행한다면, 해당 지역 및 기간에 대한 증발산량 모의 및 관련 특성인자를 파악하는 연구에 활용도가 높을 것으로 기대된다. The Reference Evapotranspiration Calculator Software (REF-ET) supports computational guidelines for the reference evapotranspiration using seventeen FAO Penman-Monteith (PM) equations simultaneously such as the ASCE and FAO standardized forms. The REF-ET can conveniently consider missing data predictions and regional site characterizations, when reference ET is computed on monthly, daily, and hourly time steps. The applicability of the REF-ET was estimated to simulate the reference ET using hourly weather data from Seoul weather station for 29 years. The result found that the FAO24-Rd and 1957-Makk equations closely concerned with solar radiation parameter which were the most highly correlated to reference ET computed by pan coefficient. In addition, the 1957-Makk equation was identified as the most correct computational method for reference ET by analysis of bias and root mean square error. The 1957-Makk equation could predict the reference ET within the error of less than 1.06 ㎜/day, though all the other equations tended toward overestimation of predicting the reference ET in comparison with refecence ET of pan. The results of this study suggest that the REF-ET will be applicable to support reference ET estimation for a variety of field condition and time-scale.

Impact of climate change on spatial distribution and temporal trends of reference evapotranspiration in Egypt

( Ahmed Nagy Yassen ),( Won-ho Nam ) 한국농공학회 2018 한국농공학회 학술대회초록집 Vol.2018 No.-

Reference evapotranspiration is the first step in determining agriculture water requirements and irrigation scheduling, Understanding the changes in reference evapotranspiration under climate change is an important component to improve crop management because it is projected to cause potential effects of crop production. Therefore, detecting the changes in the spatial distribution and temporal trends of reference evapotranspiration at the regional and local scale aids in understanding the impacts of climate change and its subsequent effect on hydrology and agriculture. The aim of this study is to identify whether there have been changes in the annual and monthly reference evapotranspiration in Egypt, as evidenced by spatial distribution and temporal trends. The results showed that a statistically significant spatial distribution of reference evapotranspiration change has occurred in the last 35 years beginning in the 1980s. The southeastern regions, the older agricultural lands in the Nile Delta and valley, as well as the northwestern regions showed significant differences when the western desert showed non-significant effect of climate change in the annual and monthly distributions. According to statistical analysis conducted on the monthly distribution, during the winter season from November to February showed the lowest effect of climate change, while during the summer season, the highest and most significant differences occurred, especially from June to October. The last five years (2013-2017) showed a significant decrease from the previous 5 years (2008-2012) but still show a significant increase from previous periods of time (1983-2007). Based on previous results, the western desert is suitable for new reclaimed projects. Furthermore, the summer crops should allow the redetermination of water requirements so involved parties can confront the effect of climate change, especially in older agricultural lands. This study is significant, as it provides baseline information regarding long-term spatial distribution and temporal trends of reference evapotranspiration related to climate variability and change.

Climate Change Impacts on Reference Evapotranspiration and Drought Risk Management under Environmental Egyptian Condition

( Ahmed Nagy Yassen ),( Won-ho Nam ) 한국농공학회 2018 한국농공학회 학술대회초록집 Vol.2018 No.-

Reference evapotranspiration is the first step in determining agricultural water requirements and irrigation scheduling. Impact of drought is more acute in arid and semi-arid regions. Droughts have always had far-reaching effects causing failure of crops, decreasing natural vegetation, and depleting water supplies. so today, due to the impact of climate change, the assessment of spatial distribution and temporal trends of reference evapotranspiration and drought is very important and necessary. The aim of this study is to identify whether there have been changes in the annual and monthly reference evapotranspiration and annual and seasonal drought in Egypt. The results showed that a statistically significant spatial distribution of reference evapotranspiration change has occurred in the last 35 years beginning in the 1980s. The southeastern regions, the older agricultural lands in the Nile Delta and valley, as well as the northwestern regions showed significant differences when the western desert showed non-significant effect of climate change in the annual and monthly distributions. According to statistical analysis conducted on the monthly distribution, during the winter season from November to February showed the lowest effect of climate change, while during the summer season, the highest and most significant differences occurred, especially from June to October. The last five years (2013-2017) showed a significant decrease from the previous 5 years (2008-2012) but still show a significant increase from previous periods of time (1983-2007). The drought indices showed that Coastal, Middle Delta and Middle Egypt regions were the most affected areas by drought risk, drought event occurred in 2010 in most regions at all timescales. Western desert and southeastern showed the lowest parts affected by drought risk. SPI showed lower impact than SPEI. Based on previous results, the western desert is suitable for new reclaimed projects. Furthermore, the summer crops should allow the redetermination of water requirements so involved parties can confront the effect of climate change, especially in older agricultural lands. The maps prepared using the spatiotemporal analysis will be useful to policymakers and local administrators to take effective measures to plan water resources.

기상자료의 결측과 산정에 따른 기준작물 증발산량 공식의 비교 평가

윤푸른,최진용,Yoon, Pu Reun,Choi, Jin-Yong 한국농공학회 2018 한국농공학회논문집 Vol.60 No.3

Estimating the reference evapotranspiration is an important factor to consider in irrigation system design and agricultural water use. However, there is a limitation in using the FAO Penman-Monteith (FAO P-M) equation, which requires various meteorological data. The purpose of this study is to compare three reference evapotranspiration (ETo) equations in the case of meteorological data missing for 11 study weather stations. Firstly, the FAO P-M equation is used for reference potential evapotranspiration estimation with the actual solar radiation data $R_n$ and the actual vapor pressure $e_a$. Then, in the case of $R_n$, and $e_a$ are missed, the reference evapotranspirations applying FAO P-M, Priestley-Taylor (P-T), Hargreaves (HG) equation were calculated using other meteorological factors. Secondly, MAE, RMSE, $R^2$ were calculated to compare ETo relationship from the ETo equations. From the results, ETo with Hargreaves equation in coastal areas and the Priestley-Taylor equation in the inland areas showed relatively high correlation with FAO P-M when $e_a$ data is missed. In the case of $R_n$ data is missed or two weather data, $e_a$, and $R_n$ data are all missed, $R^2$ value in Priestley-Taylor equation was highest in coastal areas, and $R^2$ values in Hargreaves equation were the high values for 7 inland areas. The results of sensitivity analysis showed that net radiation was the most sensitive for P-T and HG equation, and for FAO P-M, the most sensitive factor was net radiation and relative humidity, air temperature and wind speed were follows. Therefore, in considering of the accessibility to the coast, the types of the missing wether data, and the correlation and the magnitude of error, the reference evapotranspiration equations would be selected in sense of different conditions.

Verification of Reference Evapotranspiration Estimated by Weighable Lysimeters and Its Applicability

김동진,한경화,조희래,황승아,옥정훈 한국토양비료학회 2019 한국토양비료학회지 Vol.52 No.3

The reference evapotranspiration (ET0) is an essential indicator in explaining the water movement in the environment. In this study, we carried out to investigate the ET0, which were LYET (reference evapotranspiration calculated by the weighable lysimeter), PMET (reference evapotranspiration calculated by the FAO Penman- Monteith equation), and HSET (reference evapotranspiration calculated by the Hargreaves equation), respectively, and to estimate the relationship among the LYET, PMET, and HSET by regression analysis. Turfgrass was selected as the reference crop for calculating the ET0 by the lysimeters. The experiment period was from 1st June to 31st December in 2015. The ET0 in the lysimeter study area (National Institute of Agricultural Sciences, Wanju; WJ) was compared with that in the nearby Jeonju (JJ) location because of similar weather conditions. The relationship between PMET-WJ and PMET-JJ has the slope of 1.138, the coefficient of determination (R2) of 0.972, and the relationship between HSET-WJ and HSET-JJ has a slope of 0.934 (R2=0.984); thus the fitness was high in both cases. The relationship between LYET and PMET in both soils (fine loamy, FL; coarse loamy, CL) showed a relatively high R2 as higher than 0.9, whereas the relationship between LYET and HSET showed relatively low fitness (0.676 - 0.736 of R2). According to the month, the fitness of PMET:LYET was higher than that of HSET:LYET, and in November and December, the R2 of PMET:LYET was lowered to 0.7 or less as turfgrass entered into a dormant stage. The LYET, PMET, and HSET were found to have significantly high positive correlations with the minimum temperature, maximum temperature, mean temperature, and solar radiation (p < 0.01) and a significantly high negative correlation with mean humidity (p < 0.01). The estimated ET0 by the lysimeter experiment was evaluated to be highly conformable with the ET0 calculated by the FAO PM equations. Follow-up studies such as long-term monitoring are necessary to cope with the changing climate every year.

Verification of Reference Evapotranspiration Estimated by Weighable Lysimeters and Its Applicability

Dong-Jin Kim,Kyung-Hwa Han,Yong-Seon Zhang,Hee-Rae Cho,Seon-Ah Hwang,Jung-Hun Ok 한국토양비료학회 2019 한국토양비료학회지 Vol.52 No.3

The reference evapotranspiration (ET0) is an essential indicator in explaining the water movement in the environment. In this study, we carried out to investigate the ET0, which were LYET (reference evapotranspiration calculated by the weighable lysimeter), PMET (reference evapotranspiration calculated by the FAO Penman-Monteith equation), and HSET (reference evapotranspiration calculated by the Hargreaves equation), respectively, and to estimate the relationship among the LYET, PMET, and HSET by regression analysis. Turfgrass was selected as the reference crop for calculating the ET0 by the lysimeters. The experiment period was from 1st June to 31st December in 2015. The ET0 in the lysimeter study area (National Institute of Agricultural Sciences, Wanju; WJ) was compared with that in the nearby Jeonju (JJ) location because of similar weather conditions. The relationship between PMET-WJ and PMET-JJ has the slope of 1.138, the coefficient of determination (R<SUP>2</SUP>) of 0.972, and the relationship between HSET-WJ and HSET-JJ has a slope of 0.934 (R<SUP>2</SUP>=0.984); thus the fitness was high in both cases. The relationship between LYET and PMET in both soils (fine loamy, FL; coarse loamy, CL) showed a relatively high R<SUP>2</SUP><SUP></SUP> as higher than 0.9, whereas the relationship between LYET and HSET showed relatively low fitness (0.676 - 0.736 of R<SUP>2</SUP>). According to the month, the fitness of PMET:LYET was higher than that of HSET:LYET, and in November and December, the R<SUP>2</SUP> of PMET:LYET was lowered to 0.7 or less as turfgrass entered into a dormant stage. The LYET, PMET, and HSET were found to have significantly high positive correlations with the minimum temperature, maximum temperature, mean temperature, and solar radiation (p < 0.01) and a significantly high negative correlation with mean humidity (p < 0.01). The estimated ET0 by the lysimeter experiment was evaluated to be highly conformable with the ET0 calculated by the FAO PM equations. Follow-up studies such as long-term monitoring are necessary to cope with the changing climate every year.

기후변화에 따른 우리나라 기준증발산량 변화 분석

문장원 한국방재학회 2018 한국방재학회논문집 Vol.18 No.7

본 연구에서는 기후변화가 우리나라의 증발산 특성에 미치는 영향을 평가하기 위한 연구를 수행하였다. RCP 4.5 및 8.5 시나리오를 이용하여 기상청 62개 지점에 대한 기준증발산량을 산정한 후 관측자료에 의한 산정 결과와 비교하였다. 분석 결과, 연평균 기준증발산량의 경우 RCP 4.5 시나리오에서는 현재 대비 5.4%, RCP 8.5 시나리오에서는 현재 대비 9.5% 증가할 것으로 나타났으며, 월별로는 1월, 2월, 11월, 12월에서 현재 대비 10% 이상 기준증발산량이 증가할 것으로 나타났다. 연 강수량과 연 기준증발산량의 비율을 이용하여 미래 기간에 대한 가뭄 발생 가능성을 검토하였으며, RCP 4.5 시나리오에 비해 RCP 8.5 시나리오의 가뭄 발생 가능성이 상대적으로 높게 나타나는 결과를 확인할 수 있었다. 따라서 기후변화로 인한 기준증발산량의 증가는 이용 가능한 수자원량의 감소를 초래할 수 있으므로 지속적인 모니터링과 적절한 적응대책의 수립이 필요하다는 결과를 얻을 수 있었다. In this study, the impact of climate change on the characteristics of evapotranspiration in Korea was assessed. The Regional Concentration Pathway (RCP) 4.5 and 8.5 scenarios were used to calculate the reference evapotranspiration for 62 stations of the Korea Meteorological Administration (KMA) and compared with the calculation results from observation data. The results of the analysis showed that the average annual evapotranspiration increases by 5.4% in the RCP 4.5 scenario and 9.5% in the RCP 8.5 scenario compared with the current one. On a monthly scale, the reference evapotranspiration for January, February, November and December is expected to increase by more than 10% compared to the current period. The ratio of annual rainfall to yearly evapotranspiration was used to examine the possibility of droughts for future periods, and the results were found to be relatively high in the RCP 8.5 scenario when compared to the RCP 4.5 scenario. The increase in the reference evapotranspiration due to climate change may lead to a decrease in the available water resources, and therefore, continuous monitoring and appropriate adaptation measures are necessary.