Spatial distribution and temporal variation of reference evapotranspiration in arid and semi‐arid regions of Iran

Analysis of spatial and temporal variations of reference evapotranspiration (ET_o) is important in arid and semi‐arid regions where water resources are limited. The main aim of this study was to analyse the spatial distribution and the annual, seasonal and monthly trends of the Penman–Monteith ET_o for 21 stations in the arid and semi‐arid regions of Iran. Three statistical tests the Mann‐Kendall, Sen's slope estimator and linear regression were used for the analysis. The analysis revealed that ET_o increased from January to July and deceased from July to December at almost all stations. Additionally, higher annual ET_o values were found in the southeast of the study region and lower values in the northwest of the region. Although the results showed both positive and negative trends in annual ET_o series, ET_o generally increased, significantly so in six (～30%) of the stations. Analysis of the impacts of meteorological variables on the temporal trends of ET_o indicated that the increasing trend of ET_o was most likely due to a significant increase in minimum air temperature, while decreasing trend of ET_o was mainly caused by a significant decrease in wind speed. At the sites where increasing ET_o trends were statistically significant, the rate of increase varied from (+)8·36 mm/year at Mashhad station to (+)31·68 mm/year at Iranshahr station. On average, an increasing trend of (+)4·42 mm/year was obtained for the whole study area during the last four decades. Seasonal and monthly ET_o have also tended to increase at the majority of the stations. The greatest numbers of significant trends were observed in winter on the seasonal time‐scale and in September on the monthly time‐scale. Copyright © 2011 John Wiley & Sons, Ltd.     

Spatio-temporal variations of reference crop evapotranspiration and pan evaporation in the West Songnen Plain of China

Abstract

The spatio-temporal variations of reference crop evapotranspiration (ET_ref) reflect the combined effects of meteorological variables, primarily wind speed, relative humidity, net radiation and air temperature. This study investigated the spatial distribution and temporal trends of ET_ref (calculated by the FAO-56 Penman-Monteith equation), pan evaporation (E_pan) and pan coefficient (K_p) in a 140?×?10³ km² semi-humid to semi-arid area in China. The results show that: (i) although the spatial distributions of ET_ref and E_pan are roughly similar and their spatial correlation is high over the growing season, K_p varied considerably in space due to high humidity in the east of the region and low humidity in the southwest; (ii) the monthly variations of ET_ref and E_pan are similar to that of net radiation and opposite to that of relative humidity, while the monthly variation of K_p is similar to that of relative humidity and opposite to that of wind speed, and the long-term trend is slightly increasing for ET_ref and E_pan, while significantly (10% significance level) increasing for K_p; and (iii) generally, the time series of ET_ref and E_pan from 1951 to 2001 could be divided into three phases due to variations of meteorological variables.

Citation Liang, L.-Q., Li, L.-J. & Liu, Q. (2011) Spatio-temporal variations of reference crop evapotranspiration and pan evaporation in the West Songnen Plain of China. Hydrol. Sci. J. 56(7), 1300–1313.     

Environmental regulation and innovation: Evidence from China

The relevance of analyzing effects of environmental regulation on innovation cannot be overemphasized. In this paper, we first develop a theoretical model to predict how command-and-control environmental regulation affects innovation, and then we derive its channels. Using the difference-in-difference-in-differences strategy and a comprehensive dataset at city-industry-year level of manufacturing sectors in China, we found that the more stringent environmental regulations that are faced by cities, measured by the reduction targets of chemical oxygen demand (COD) and sulfur dioxide (SO₂) during the eleventh Five-Year Plan, are negatively associated with innovation. Thus, the evidence contradicts the Porter Hypothesis. On average, a one standard deviation increase in the reduction targets of COD (SO₂) is associated with a 0.023 (0.016) standard deviation decrease in the innovation index. We controlled carefully for various potential confounders, and the results were supported by robustness and falsification checks. There exists an evident heterogeneity effect across regions and industries with different pollution intensities. The channel analysis shows that stricter environmental regulation also accounts for a sharp decline in labor demand, firm entry, and inbound foreign direct investment. Our findings are also robust to alternative measures for innovation and environmental regulation.     

M5 model tree based modelling of reference evapotranspiration

This paper investigates the potential of M5 model tree based regression approach to model daily reference evapotranspiration using climatic data of Davis station maintained by California irrigation Management Information System (CIMIS). Four inputs including solar radiation, average air temperature, average relative humidity, and average wind speed whereas reference evapotranspiration calculated using a relation provided by the CIMIS was used as output. To compare the performance of M5 model tree in predicting the reference evapotranspiration, FAO–56 Penman–Monteith equation and calibrated Hargreaves–Samani relation was used. A comparison of results suggests that M5 model tree approach works well in comparison to both FAO–56 and calibrated Hargreaves–Samani relations. To judge the generalization capability of M5 model tree approach, model created by using the Davis data set was tested with the datasets of four different sites. Results from this part of the study suggest that M5 model tree could successfully be employed in modeling the reference evapotranspiration. Further, sensitivity analysis with M5 model tree approach suggests the suitability of solar radiation, average air temperature, average relative humidity, and average wind speed as input parameters to model the reference evapotranspiration Copyright © 2009 John Wiley & Sons, Ltd.     

鄂尔多斯盆地中东部奥陶系马家沟组马五6亚段硬石膏产状类型与成因*

鄂尔多斯盆地中东部奥陶系马家沟组马五₆亚段硬石膏产状类型多样,基于系统的宏观与微观岩石学分析,识别并区分出星散状(A1型)、纹层状(A2型)、致密块状(A3型)、结核状或团块状(A4型)、鸡雏状或角砾状(A5型)等硬石膏产状类型。单井高频旋回和微相分析表明,马五₆亚段发育与潮坪、潟湖、鲕粒滩、砂屑滩、微生物丘等有关的5种高频向上变浅序列,硬石膏的产状类型、产出位置和分布形式等与向上变浅序列有很好的耦合关系。A1型和A2型硬石膏发育于高频向上变浅序列的下部和中部,主要与膏云质或云膏质潟湖相关,属于潟湖相原生化学沉积成因。A3型硬石膏分布于高频向上变浅序列的上部,受膏质潟湖控制,也属于原生化学沉积成因。经典的结核状硬石膏(A4-1)呈随机分布形式产于潮坪沉积序列,为成岩期交代作用或者膏化作用成因,与传统萨布哈交代成因的膏质结核相似。A4-2型硬石膏主要出现在颗粒岩和微生物岩中,主要由富含CaSO₄的下渗卤水在溶蚀孔洞中沉淀形成;A5型硬石膏发育于向上变浅序列的上部和顶部,与高频暴露有关,为准同生期以溶蚀—充填为主的岩溶改造成因。发育完整的单个高频旋回,大致经历了高频快速海侵早期、高频快速海侵晚期至缓慢海退早期、高频缓慢海退晚期和高频海退末期暴露4个演化阶段,形成了与之耦合的海相碳酸盐岩与硬石膏共生序列。这些认识将对马家沟组沉积古环境的再认识具有重要的参考意义。     

Distribution of whitemouth croaker (Micropogonias furnieri, Desmarest 1823) larvae in the Río de la Plata estuarine front

Whitemouth croaker (Micropogonias furnieri) larvae obtained and hydrographic data collected in the Rio de la Plata estuary (35°S–56°W) between 1987 and 2000 were used to explore the early life stages spatial and temporal distribution patterns and their relation to oceanographic features. The spatial distribution, restricted to a band in the inner part of the estuary, coincided with the bottom salinity front and the maximum turbidity zone (MTZ, turbidity front). Larvae were present during the warmest months (October through May) within a range of 14–24.5 °C temperature and 0.9–33 salinity. A vertically stratified sampling performed in the region where the largest abundance was found (December 2005 and March 2006) was used to test the hypothesis that larvae retention occurs in the bottom salinity front.The vertically stratified sampling showed larvae throughout the water column with high predominance in the river–estuary transition zone. A positive correlation between abundance and the bottom salinity horizontal gradient was found. The size analysis showed that the largest individuals (>10 mm SL), probably undergoing the settlement process, inhabited near the bottom and that the smallest (<10 mm SL) were present in the whole water column. Length distribution along the front showed no trend.Results support the estuarine retention hypothesis of previous studies on whitemouth croaker gravid females, eggs distribution and outcomes from a numerical simulation model. Retention in the salinity front/MTZ would allow larvae to benefit from food accumulation in the region, the high turbidity level provide shelter against predators and retention in the estuary secure closeness to the main nursery ground.     

Bare soil evaporation under high evaporation demand: a proposed modification to the FAO-56 model

Abstract

This study evaluates the evaporation component of the FAO-56 model under high evaporation demand. To perform this, two data sets were used as field evaluation, and a second model was used for comparison (a model based on the square root of time, SRT). The results show that although FAO-56, the field data and the SRT model present similar cumulative evaporation over the study period (approximately one month), when the data are analysed daily, FAO-56 overestimated evaporation at the beginning of the process and underestimated it at the end. A correction for FAO-56 is proposed to amend the mismatch between FAO-56 and the field-measured data under high evaporation conditions. Consequently, the parameters used by the FAO-56 evaporation component are discussed.

Citation Torres, E. A. & Calera, A. (2010) Bare soil evaporation under high evaporation demand: a proposed modification to the FAO-56 model. Hydrol. Sci. J. 55(3), 303–315.     

Modelling hourly evapotranspiration and soil water content at the grass-covered boundary-layer field site Falkenberg,Germany

Abstract

The study analyses a 2-year period of hourly rates of real evapotranspiration (ETr) derived from eddy covariance measurements and soil water contents at depths from 8 to 90 cm, monitored by time domain reflectometry probes at the grass-covered boundary-layer field site Falkenberg of the Lindenberg Meteorological Observatory – Richard-Aßmann-Observatory, operated by the German Meteorological Service (DWD). The ETr rates and soil water contents were compared with the results of a modelling approach consisting of the Penman-Monteith equation and the soil water balance model Hydrus-1D using a noncompensatory and a compensatory root-water uptake model. After optimization of soil hydraulic parameters by inverse modelling, using measured soil water contents as the objective function, simulated and measured model outputs showed good agreement for soil water contents above 90 cm depth and for ETr rates simulated by our modelling approaches using noncompensatory root-water uptake. The application of a compensatory root-water uptake model led to a decrease in the simulation quality for the total investigation period.

Editor Z.W. Kundzewicz

Citation Wegehenkel, M. and Beyrich, F., 2014. Modelling of hourly evapotranspiration and soil water content at the grass-covered boundary-layer field site Falkenberg, Germany. Hydrological Sciences Journal, 59 (2), 376–394.