Complexity of Forces Driving Trend of Reference Evapotranspiration and Signals of Climate Change
Understanding the trends of reference evapotranspiration (<i>ET<sub>o</sub></i>) and its influential meteorological variables due to climate change is required for studying the hydrological cycle, vegetation restoration, and regional agricultural production. Although several...
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MDPI AG
2020-10-01
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| Series: | Atmosphere |
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| Online Access: | https://www.mdpi.com/2073-4433/11/10/1081 |
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| author | Mohammad Valipour Sayed M. Bateni Mohammad Ali Gholami Sefidkouhi Mahmoud Raeini-Sarjaz Vijay P. Singh |
| author_facet | Mohammad Valipour Sayed M. Bateni Mohammad Ali Gholami Sefidkouhi Mahmoud Raeini-Sarjaz Vijay P. Singh |
| author_sort | Mohammad Valipour |
| collection | DOAJ |
| description | Understanding the trends of reference evapotranspiration (<i>ET<sub>o</sub></i>) and its influential meteorological variables due to climate change is required for studying the hydrological cycle, vegetation restoration, and regional agricultural production. Although several studies have evaluated these trends, they suffer from a number of drawbacks: (1) they used data series of less than 50 years; (2) they evaluated the individual impact of a few climatic variables on <i>ET<sub>o</sub></i>, and thus could not represent the interactive effects of all forces driving trends of <i>ET<sub>o</sub></i>; (3) they mostly studied trends of <i>ET<sub>o</sub></i> and meteorological variables in similar climate regions; (4) they often did not eliminate the impact of serial correlations on the trends of <i>ET<sub>o</sub></i> and meteorological variables; and finally (5) they did not study the extremum values of meteorological variables and <i>ET<sub>o</sub></i>. This study overcame the abovementioned shortcomings by (1) analyzing the 50-year (1961–2010) annual trends of <i>ET<sub>o</sub></i> and 12 meteorological variables from 18 study sites in contrasting climate types in Iran, (2) removing the effect of serial correlations on the trends analysis via the trend-free pre-whitening approach, (3) determining the most important meteorological variables that control the variations of <i>ET<sub>o</sub></i>, and (4) evaluating the coincidence of annual extremum values of meteorological variables and <i>ET<sub>o</sub></i>. The results showed that <i>ET<sub>o</sub></i> and several meteorological variables (namely wind speed, vapor pressure deficit, cloudy days, minimum relative humidity, and mean, maximum and minimum air temperature) had significant trends at the confidence level of 95% in more than 50% of the study sites. These significant trends were indicative of climate change in many regions of Iran. It was also found that the wind speed (<i>WS</i>) had the most significant influence on the trend of <i>ET<sub>o</sub></i> in most of the study sites, especially in the years with extremum values of <i>ET<sub>o</sub></i>. In 83.3% of the study sites (i.e., all arid, Mediterranean and humid regions and 66.7% of semiarid regions), both <i>ET<sub>o</sub></i> and <i>WS</i> reached their extremum values in the same year. The significant changes in <i>ET<sub>o</sub></i> due to <i>WS</i> and other meteorological variables have made it necessary to optimize cropping patterns in Iran. |
| first_indexed | 2024-03-10T15:44:32Z |
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| language | English |
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| publishDate | 2020-10-01 |
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| spelling | doaj.art-97e8df3553b44f0b8d5e645ebb927aae2023-11-20T16:35:30ZengMDPI AGAtmosphere2073-44332020-10-011110108110.3390/atmos11101081Complexity of Forces Driving Trend of Reference Evapotranspiration and Signals of Climate ChangeMohammad Valipour0Sayed M. Bateni1Mohammad Ali Gholami Sefidkouhi2Mahmoud Raeini-Sarjaz3Vijay P. Singh4Department of Civil and Environmental Engineering and Water Resources Research Center, University of Hawaii at Manoa, Honolulu, HI 96822, USADepartment of Civil and Environmental Engineering and Water Resources Research Center, University of Hawaii at Manoa, Honolulu, HI 96822, USADepartment of Water Engineering, Sari Agricultural Sciences and Natural Resources University, Sari 382220, IranDepartment of Water Engineering, Sari Agricultural Sciences and Natural Resources University, Sari 382220, IranDepartment of Biological and Agricultural Engineering and Zachry Department of Civil Engineering, Texas A and M University, 321 Scoates Hall, 2117 TAMU, College Station, TX 77843-2117, USAUnderstanding the trends of reference evapotranspiration (<i>ET<sub>o</sub></i>) and its influential meteorological variables due to climate change is required for studying the hydrological cycle, vegetation restoration, and regional agricultural production. Although several studies have evaluated these trends, they suffer from a number of drawbacks: (1) they used data series of less than 50 years; (2) they evaluated the individual impact of a few climatic variables on <i>ET<sub>o</sub></i>, and thus could not represent the interactive effects of all forces driving trends of <i>ET<sub>o</sub></i>; (3) they mostly studied trends of <i>ET<sub>o</sub></i> and meteorological variables in similar climate regions; (4) they often did not eliminate the impact of serial correlations on the trends of <i>ET<sub>o</sub></i> and meteorological variables; and finally (5) they did not study the extremum values of meteorological variables and <i>ET<sub>o</sub></i>. This study overcame the abovementioned shortcomings by (1) analyzing the 50-year (1961–2010) annual trends of <i>ET<sub>o</sub></i> and 12 meteorological variables from 18 study sites in contrasting climate types in Iran, (2) removing the effect of serial correlations on the trends analysis via the trend-free pre-whitening approach, (3) determining the most important meteorological variables that control the variations of <i>ET<sub>o</sub></i>, and (4) evaluating the coincidence of annual extremum values of meteorological variables and <i>ET<sub>o</sub></i>. The results showed that <i>ET<sub>o</sub></i> and several meteorological variables (namely wind speed, vapor pressure deficit, cloudy days, minimum relative humidity, and mean, maximum and minimum air temperature) had significant trends at the confidence level of 95% in more than 50% of the study sites. These significant trends were indicative of climate change in many regions of Iran. It was also found that the wind speed (<i>WS</i>) had the most significant influence on the trend of <i>ET<sub>o</sub></i> in most of the study sites, especially in the years with extremum values of <i>ET<sub>o</sub></i>. In 83.3% of the study sites (i.e., all arid, Mediterranean and humid regions and 66.7% of semiarid regions), both <i>ET<sub>o</sub></i> and <i>WS</i> reached their extremum values in the same year. The significant changes in <i>ET<sub>o</sub></i> due to <i>WS</i> and other meteorological variables have made it necessary to optimize cropping patterns in Iran.https://www.mdpi.com/2073-4433/11/10/1081reference evapotranspirationclimate changedroughtmeteorological extremesclimatic variableswind speed |
| spellingShingle | Mohammad Valipour Sayed M. Bateni Mohammad Ali Gholami Sefidkouhi Mahmoud Raeini-Sarjaz Vijay P. Singh Complexity of Forces Driving Trend of Reference Evapotranspiration and Signals of Climate Change Atmosphere reference evapotranspiration climate change drought meteorological extremes climatic variables wind speed |
| title | Complexity of Forces Driving Trend of Reference Evapotranspiration and Signals of Climate Change |
| title_full | Complexity of Forces Driving Trend of Reference Evapotranspiration and Signals of Climate Change |
| title_fullStr | Complexity of Forces Driving Trend of Reference Evapotranspiration and Signals of Climate Change |
| title_full_unstemmed | Complexity of Forces Driving Trend of Reference Evapotranspiration and Signals of Climate Change |
| title_short | Complexity of Forces Driving Trend of Reference Evapotranspiration and Signals of Climate Change |
| title_sort | complexity of forces driving trend of reference evapotranspiration and signals of climate change |
| topic | reference evapotranspiration climate change drought meteorological extremes climatic variables wind speed |
| url | https://www.mdpi.com/2073-4433/11/10/1081 |
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