scholarly journals Searching evidence for the existence of evaporation paradox in arid environments of northwest India

2014 ◽  
Vol 17 (1) ◽  
pp. 3-11 ◽  
Keyword(s):  
Wind Speed ◽  
Sunshine Duration ◽  
Monsoon Season ◽  
Kendall Test ◽  
Arid Environments ◽  
Thar Desert ◽  
Pan Evaporation ◽  
Sunshine Hours ◽  
Northwest India ◽  
Increasing Trends

<div> <p>Trends in pan evaporation (E<sub>pan</sub>) and temperature were identified through the Mann-Kendall test over Jaisalmer to probe the existence of evaporation paradox in arid environments of Thar Desert, northwest India. We also analyzed trends in rainfall, relative humidity, wind speed, and sunshine duration in the context of climate change. Decreasing trends in E<sub>pan </sub>were witnessed over Jaisalmer in the months of January, June, October and November in the range of -2.04 to -4.1 mm/year. Significant rainfall decreases were witnessed in the three crucial months of monsoon season, i.e., July, August and September, in range of -0.23 to -1.25 mm/year. Increasing trends in mean temperature were witnessed corresponding to annual and monthly (January, April, September, October and November) time scales in the range of 0.03 to 0.07 &deg;C/year. The simultaneous E<sub>pan </sub>decrease and temperature rise at Jaisalmer confirmed the existence of evaporation paradox in the months of winter and post-monsoon seasons, which may be due to decreases in wind speed and bright sunshine hours. The increase in temperature along with decreases in E<sub>pan</sub>, rainfall, sunshine duration, and wind speed over Jaisalmer may have far reaching consequences for the fragile ecosystem of the Thar Desert.</p> </div> <p>&nbsp;</p>

scholarly journals Change in Climate Extremes and Pan Evaporation Influencing Factors over Ouémé Delta in Bénin

Climate ◽  
2018 ◽  
Vol 7 (1) ◽  
pp. 2 ◽  
Author(s):  
Rita Hounguè ◽  
Agnidé Lawin ◽  
Sounmaila Moumouni ◽  
Akambi Afouda
Keyword(s):  
Wind Speed ◽  
Partial Correlation ◽  
Sunshine Duration ◽  
Climate Extremes ◽  
Kendall Test ◽  
Pan Evaporation ◽  
Adaptation Measures ◽  
Delta Area ◽  
Increasing Trend ◽  
Precipitation Indices

This work focuses on trend analysis of rainfall, evaporation, temperature, relative humidity, wind speed, and sunshine duration over the Ouémé Delta in Bénin. Eight temperature based indices and fifteen rainfall based indices are computed from 1960 to 2016. Moreover, maximum 1, 2, 3, 5, and 10 days precipitation indices were computed at the monthly scale. Trends are detected at 0.05 confidence level, using a combination of Mann-Kendall and prewhitened Mann-Kendall test. Partial correlation and stepwise regression are used to detect the set of meteorological variables that influence pan evaporation in Ouémé Delta. Results showed intensification of heavy rainfall over Ouémé Delta. Moreover, a significant increasing trend is detected in temperature. As consequence, diurnal temperature significantly decreases as proof of the global warming. Average pan evaporation showed a significant slither increasing trend over the area. Change in pan evaporation can be explained by wind speed and sunshine duration that hold almost 50% of pan evaporation variance. As future temperature is going to be increasing, pan evaporation may increase considerably. So, adaptation measures have to be reinforced in the Ouémé Delta area where farmer are used to rainfed agriculture for food security. Moreover, Ouémé Delta plan have to be developed for it resources sustainability.

scholarly journals Simulation of Pan-Evaporation Using Penman and Hamon Equations and Artificial Intelligence Techniques

Water ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 793
Author(s):  
Abdul Razzaq Ghumman ◽  
Mohammed Jamaan ◽  
Afaq Ahmad ◽  
Md. Shafiquzzaman ◽  
Husnain Haider ◽  
...  
Keyword(s):  
Wind Speed ◽  
Water Resources ◽  
Arid Regions ◽  
Fuzzy Inference ◽  
Sunshine Duration ◽  
Pan Evaporation ◽  
Estimation Of Parameters ◽  
Inference System ◽  
Daunting Task ◽  
The Impact

The evaporation losses are very high in warm-arid regions and their accurate evaluation is vital for the sustainable management of water resources. The assessment of such losses involves extremely difficult and original tasks because of the scarcity of data in countries with an arid climate. The main objective of this paper is to develop models for the simulation of pan-evaporation with the help of Penman and Hamon’s equations, Artificial Neural Networks (ANNs), and the Artificial Neuro Fuzzy Inference System (ANFIS). The results from five types of ANN models with different training functions were compared to find the best possible training function. The impact of using various input variables was investigated as an original contribution of this research. The average temperature and mean wind speed were found to be the most influential parameters. The estimation of parameters for Penman and Hamon’s equations was quite a daunting task. These parameters were estimated using a state of the art optimization algorithm, namely General Reduced Gradient Technique. The results of the Penman and Hamon’s equations, ANN, and ANFIS were compared. Thirty-eight years (from 1980 to 2018) of manually recorded pan-evaporation data regarding mean daily values of a month, including the relative humidity, wind speed, sunshine duration, and temperature, were collected from three gauging stations situated in Al Qassim, Saudi Arabia. The Nash and Sutcliffe Efficiency (NSE) and Mean Square Error (MSE) evaluated the performance of pan-evaporation modeling techniques. The study shows that the ANFIS simulation results were better than those of ANN and Penman and Hamon’s equations. The findings of the present research will help managers, engineers, and decision makers to sustainability manage natural water resources in warm-arid regions.

scholarly journals Analysis of rainfall trends over Tripura

MAUSAM ◽  
2022 ◽  
Vol 73 (1) ◽  
pp. 27-36
Author(s):  
RANJAN PHUKAN ◽  
D. SAHA
Keyword(s):  
Heavy Rainfall ◽  
Monsoon Season ◽  
Rainfall Variability ◽  
Kendall Test ◽  
Annual Rainfall ◽  
The North ◽  
Rainfall Trends ◽  
Annual Scale ◽  
Increasing Trends ◽  
Rainy Days

Rainfall in India has very high temporal and spatial variability. The rainfall variability affects the livelihood and food habits of people from different regions. In this study, the rainfall trends in two stations in the north-eastern state of Tripura, namely Agartala and Kailashahar have been studied for the period 1955-2017. The state experiences an annual mean of more than 2000 mm of rainfall, out of which, about 60% occurs during the monsoon season and about 30% in pre-monsoon. An attempt has been made to analyze the trends in seasonal and annual rainfall, rainy days and heavy rainfall in the two stations, during the same period.Non-parametric Mann-Kendall test has been used to find out the significance of these trends. Both increasing and decreasing trends are observed over the two stations. Increasing trends in rainfall, rainy days and heavy rainfall are found at Agartala during pre-monsoon season and decreasing trends in all other seasons and at annual scale. At Kailashahar, rainfall amount (rainy days & heavy rainfall) is found to be increasing during pre-monsoon and monsoon seasons (pre-monsoon season). At annual scale also, rainfall and rainy days show increasing trends at Kailashahar. The parameters are showing decreasing trends during all other seasons at the station. Rainy days over Agartala show a significantly decreasing trend in monsoon, whereas no other trend is found to be significant over both the stations.  

scholarly journals Trend analysis of weather parameters over Indian Sundarbans

2021 ◽  
Vol 21 (3) ◽  
pp. 307-615
Author(s):  
UTTAM KUMAR MANDAL ◽  
DIBYENDU BIKAS NAYAK ◽  
SOURAV MULLICK ◽  
ARPAN SAMUI ◽  
AMIT KUMAR JANA ◽  
...  
Keyword(s):  
Monsoon Season ◽  
Temporal Trends ◽  
Kendall Test ◽  
Eastern Coast ◽  
Annual Rainfall ◽  
Crop Evapotranspiration ◽  
Indian Sundarbans ◽  
Sunshine Hours ◽  
Weather Parameters ◽  
Rainy Days

Sundarbans in West Bengal of India by virtue of its strategic location in the Eastern coast on the Bay of Bengal falls in one of the most vulnerable zones of abrupt climate change. Temporal trends of weather parameters of Canning Town (22o18'10.8'' N Latitude, 88o39'58.4'' E Longitude, elevation 3.52 m msl) representing Indian Sundarbans were analysed by non-parametric Mann-Kendall test and Sen's slope approaches. Analysis of long term rainfall data (1966-2015) indicated that Canning receives a mean annual rainfall of 1821 mm (±341.8 mm) with a considerable variation (CV = 18.8%). The results revealed that total annual rainfall trend decreased non-signicantly at the rate of 0.94 mm yr-1. On an average 84.4 rainy days in a year was recorded in the region, whereas during last ten years (2006-2015), the number of rainy days was reduced to 79.7 days yr-1. There was no signicant change in maximum, minimum and mean temperature of the region. Bright sunshine hours declined signicantly at an annual rate of 0.055 hr yr-1. Reference crop evapotranspiration (ET ) calculated using FAO Penman-Monteith method revealed that annual ET signicantly decreased at the rate of 5.98 mm yr-1. There was 2.7 times surplus rainfall than  crop evapotranspiration during monsoon months indicating very high scope of water harvesting to tackle water logging during the monsoon season and unavailability of fresh water for irrigation during lean season.

Evapotranspiration Distribution and Variation of Pakistan (1931-2015)

2017 ◽  
Vol 17 (2) ◽  
pp. 184-197 ◽  
Author(s):  
Saifullah Khan ◽  
Mahmood Ul Hasan
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Surface Pressure ◽  
Sunshine Duration ◽  
Monsoon Season ◽  
Winter Season ◽  
Main Element ◽  
Mountainous Region ◽  
Post Monsoon ◽  
Post Monsoon Season

AbstractEvapotranspiration is the main element of aridity and desertification and to balance the natural hydrological processes. Pakistan has a high degree of evapotranspiration, as it is in subtropical belt, with long sunshine duration and low cloudiness in summers. June is the warmest month, when the evapotranspiration exceeds 7mm (0.28inches), whereas, January is the coldest month, when evapotranspiration of the country falls to 1mm (0.04inches). The maximum evapotranspiration has been recorded at the southern latitudes of the country (Hyderabad and Jacobabad), while it decreases towards northwest (mountainous region) and Gilgit-Baltistan (Astore and Skardu). This variation in evapotranspiration is due to fluctuation in temperature, precipitation, sunshine duration, wind speed, relative humidity, physical relief and latitudinal as well as altitudinal extend of the country. The average evapotranspiration of Pakistan is 4.5mm with an increase of 1.0mm during 1931-2015. In winter and summer season, the lower Indus basin, has recorded high evapotranspiration as compared to the northern mountainous region. The average evapotranspiration of Pakistan during winter season is 2.7mm, while in summer it is 6.3mm. This variation is due to the variation in the length of day and night, humidity, precipitation, surface pressure, wind speed, and topography of the land. During cold season the average evapotranspiration of the country is 13.7mm, pre-monsoon season 17.1mm, monsoon season 15.8mm and post monsoon season 8mm. Obviously, the highest evapotranspiration of Pakistan has recorded during pre-monsoon season with extreme temperature, scarce precipitation, long sunshine duration, lowest relative humidity, low pressure, and calm winds and chilly condition. Furthermore, during cold (0.1mm), pre-monsoon (3.5mm), and monsoon season (2.2mm) the evapotranspiration shows an increase, where as it reveals a negative deviation of -5.6mm in post monsoon season due to increase in the precipitation from reversible monsoon lows at the southern latitudes of the country. Generally, the evapotranspiration of Pakistan increases from northwest to southeast and a main agent of delimitation of the arid region of the country. The main factors that cause variation in the evapotranspiration of the country from south towards north are temperature, precipitation, sunshine duration, relative humidity, surface pressure, wind speed, fogs, cloudiness, topography, latitudinal and altitudinal extend of the country that required further research.

Analysis of Meteorological Elements Variations of Chongqing over the Past 60 Years

2014 ◽  
Vol 501-504 ◽  
pp. 2016-2019
Author(s):  
Xun Jian Long ◽  
Chun Min Zhang ◽  
Tao Hong Yang ◽  
Yu Lin Huang
Keyword(s):  
Wind Speed ◽  
Sunshine Duration ◽  
Kendall Test ◽  
Trend Detection ◽  
Annual Data ◽  
Annual Variations ◽  
Mann Kendall Test ◽  
Mean Wind Speed ◽  
Meteorological Elements ◽  
Non Parametric

The power of a test is the probability that it cannot reject a null hypothesis when it is true. With interchangeably of non-parametric Mann-Kendall test, practical application is used in meteorological elements analysis. In this study, trend detection of meteorological elements data of Shapingba district in Chongqing, during 1951 to 2011, was estimated by non-parametric Mann-Kendall test. The analyzed elements are composed by mean precipitation, annual sunshine hours, annual humidity, annual mean temperature and annual mean wind speed. And the results show that inter-annual variations of precipitation and mean annual relative humidity are not significant. However, inter-annual variation of sunshine duration is significantly reduced, while inter-annual temperature and wind speed are significantly increased. At the same time, the non-parametric Mann-Kendall test also detects the trend on seasonal data. It is different from the annual data, and trends in different seasons show markedly different.

scholarly journals Stilling and its aerodynamic effects on pan evaporation

2020 ◽  
Vol 2 (2) ◽  
Author(s):  
Qiang Liu ◽  
Liqiao Liang
Keyword(s):  
Wind Speed ◽  
Water Resources ◽  
Temporal Trends ◽  
Vapour Pressure Deficit ◽  
Climate Factors ◽  
Pan Evaporation ◽  
The West ◽  
Sunshine Hours ◽  
The World ◽  
Standard Chinese

Declines in wind speed (u) (termed as “stilling”) has been reported in many regions of the world. To explore the temporal trends of u and its aerodynamics effects is vital to understand the changes in water resources. This study analyzed the changes of temporal trends for u and its aerodynamic effects using the data during 1959-2000 at 266 stations across China. The improved PanPen model was used to estimate Epan and quantify the contribution of radiative and aerodynamic components (aerodynamic component separated into wind speed u, vapour pressure deficit D, and air temperature Ta). Climate factors include Epan measured with the standard Chinese 20 cm diameter pan, u, Ta, relative humidity (rh) and sunshine hours (sh). The results showed: stilling occurred in most of stations (206 among 266) and 105 stations presented significant decreasing trends at 99% confidence level; stilling was the main cause for controlling the trends in Epan in most part of China, especially in the west and north of China. The results indicated that decreasing trends in Epan due to stilling would inevitably alter water resources, and should be put further investigation incorporation other factors.

scholarly journals Meteorological Factors Affecting Pan Evaporation in the Haihe River Basin, China

Water ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 317 ◽  
Author(s):  
Zhihong Yan ◽  
Shuqian Wang ◽  
Ding Ma ◽  
Bin Liu ◽  
Hong Lin ◽  
...  
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Minimum Temperature ◽  
Sunshine Duration ◽  
Maximum Temperature ◽  
Haihe River Basin ◽  
Pan Evaporation ◽  
Haihe River ◽  
Average Temperature ◽  
The Haihe River Basin

Pan evaporation (Epan) is an important indicator of regional evaporation intensity and degree of drought. However, although more evaporation is expected under rising temperatures, the reverse trend has been observed in many parts of the world, known as the “pan evaporation paradox”. In this paper, the Haihe River Basin (HRB) is divided into six sub-regions using the Canopy and k-means (The process for partitioning an N-dimensional population into k sets on the basis of a sample is called “k-means”) to cluster 44 meteorological stations in the area. The interannual and seasonal trends and the significance of eight meteorological indicators, including average temperature, maximum temperature, minimum temperature, precipitation, relative humidity, sunshine duration, wind speed, and Epan, were analyzed for 1961 to 2010 using the trend-free pre-whitening Mann-Kendall (TFPW-MK) test. Then, the correlation between meteorological elements and Epan was analyzed using the Spearman correlation coefficient. Results show that the average temperature, maximum temperature, and minimum temperature of the HRB increased, while precipitation, relative humidity, sunshine duration, wind speed and Epan exhibited a downward trend. The minimum temperature rose 2 and 1.5 times faster than the maximum temperature and average temperature, respectively. A significant reduction in sunshine duration was found to be the primary factor in the Epan decrease, while declining wind speed was the secondary factor.

Clustering analysis of regional reference evapotranspiration and its components based on climatic variables across northeast China, 1961–2010

2015 ◽  
Vol 7 (1) ◽  
pp. 128-141 ◽  
Author(s):  
Yuan Liu ◽  
Buchun Liu ◽  
Xiaojuan Yang ◽  
Wei Bai
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Northeast China ◽  
Reference Evapotranspiration ◽  
Potential Evapotranspiration ◽  
Sunshine Duration ◽  
Regional Distribution ◽  
Climatic Variables ◽  
Maximum Temperature ◽  
Sunshine Hours

Evapotranspiration integrates atmospheric demand and surface conditions. The Penman-Monteith equation was used to calculate annual and seasonal reference evapotranspiration (ET0) and thermodynamic and aerodynamic components (ETrad and ETaero) at 77 stations across northeast China, 1961–2010. The results were: (1) annual ETrad and ETaero had different regional distribution, annual ETrad values decreased from south to north, whereas the highest ETaero values were recorded in the eastern and western regions, the lowest in the central region; (2) seasonal ETaero distributions were similar to seasonal ET0, with a south–north longitudinal pattern, while seasonal ETrad distributions had a latitudinal east-west pattern; and (3) in the group for ET0 containing 69 sampling stations, effects of climatic variables on ET0 followed sunshine hours &gt; relative humidity &gt; maximum temperature &gt; wind speed. Changes in sunshine hours had the greatest effect on ETrad, but wind speed and relative humidity were the most important variables to ETaero. The decline in sunshine duration, wind speed, or both over the study period appeared to be the major cause of reduced potential evapotranspiration in most of NEC. Wind speed had opposite effects on ETrad and ETaero, and therefore the effect of wind speed on ET0 was not significant.

scholarly journals Pan Evaporative Changes in Trans-boundary Godavari River basin, India

2021 ◽  
Author(s):  
Deepak Jhajharia ◽  
Shivam Gupta ◽  
Rasoul Mirabbasi ◽  
Rohitashw Kumar ◽  
G. T. Patle
Keyword(s):  
Time Series ◽  
Wind Speed ◽  
Relative Humidity ◽  
River Basin ◽  
Monsoon Season ◽  
Total Yield ◽  
Godavari River ◽  
Mk Test ◽  
Increasing Trends ◽  
Pettitt’S Test

Abstract Pan evaporative changes are one of the key components of water resources management of a basin under changing climate and anthropogenic-induced warming. This study was undertaken for trans-boundary Godavari River (India) to identify trends through the Mann-Kendall (MK) test after removing the effect of significant lag-1 serial correlation from the climatic time-series by pre-whitening in pan evaporation (Epan) and in the probable causative meteorological parameters responsible for evaporative climatic changes in a large basin. Further, the Pettitt’s test was applied on Epan time series for estimating the change point year of Epan to find out the effective year when the change in pattern started reflecting in the time-series. At seasonal (monthly) time scales, statistically significant decreasing trends in Epan were witnessed in pre-monsoon season (in the months of March, April and May) over all the seven sites of the Godavari basin. Four sites witnessed statistically significant increasing trends in Tmin (Tmax) in July (December) and in monsoon (post monsoon) season in the basin. Statistically significant decreasing (increasing) trends in wind speed (relative humidity) in pre-monsoon and in month of March at these seven sites support the observed decline in the evaporative demand in the basin leading to possible enhancement in the total yield of the basin. Results of stepwise regression analysis showed that wind speed followed by relative humidity was found to be two main causative parameters of the observed decline in the Epan under the warmer environments in the basin. Pettitt’s test shows year 1991–1992 to be the probable year of change in the Epan in the Godavari river basin.

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