scholarly journals Seasonal and Diurnal Variations in the Priestley–Taylor Coefficient for a Large Ephemeral Lake

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 849 ◽  
Author(s):  
Guojing Gan ◽  
Yuanbo Liu ◽  
Xin Pan ◽  
Xiaosong Zhao ◽  
Mei Li ◽  
...  
Keyword(s):  
Poyang Lake ◽  
High Water ◽  
Diurnal Variations ◽  
Observation Data ◽  
Available Energy ◽  
Diurnal Patterns ◽  
Ephemeral Lakes ◽  
Seasonal And Diurnal Variations ◽  
Daily Scale ◽  
Mean Square Errors

The Priestley–Taylor equation (PTE) is widely used with its sole parameter (α) set as 1.26 for estimating the evapotranspiration (ET) of water bodies. However, variations in α may be large for ephemeral lakes. Poyang Lake, which is the largest freshwater lake in China, is water-covered and wetland-covered during its high-water and low-water periods, respectively, over a year. This paper examines the seasonal and diurnal variations in α using eddy covariance observation data for Poyang Lake. The results show that α = 1.26 is overall feasible for both periods at daily and subdaily scales. No obvious seasonal trend was observed, although the standard deviation in α for the wetland was larger than that for the water surface. The mean bias in evaporation estimations using the PTE was less than 5 W·m−2 during both periods, and the root mean square errors were much smaller than the average evaporation measurements at daily scale. U-shaped diurnal patterns of α were found during both periods, due partly to the negative correlation between α and the available energy (A). Compared to the vapor pressure deficit (VPD), wind speed (u) exerts a larger contribution to these variations. In addition, u is positively correlated with α during both periods, however, VPD was positively and negatively correlated with α during the high-water and low-water periods, respectively. Subdaily α exhibited contrasting clusters in the (u, VPD) plane under the same available energy ranges. Our study highlights the seasonal and diurnal course of α and suggests the careful use of PTE at subdaily scales.

Spatial and Temporal Variations of Eutrophication in Poyang Lake

2020 ◽  
Author(s):  
aiping huang
Keyword(s):  
Chlorophyll A ◽  
Poyang Lake ◽  
High Water ◽  
Temporal Variations ◽  
Spatial And Temporal Variations ◽  
Nutrient Concentrations ◽  
Observation Data ◽  
Chlorophyll A Concentration ◽  
High Water Period ◽  
Field Observation Data

<p>Lake eutrophication is a key point in water environmental problems in the world. Spatiotemporal variations of nutrients and chlorophyll-a and eutrophication index in Poyang Lake, the largest freshwater lake in China, are analyzed in this paper basing on field observation data at 17 sampling points from 2011 to 2016. The results show that nutrient concentrations have obvious seasonality characteristics and present bigger values in the low water period than the high water period. The peak value of chlorophyll-a concentration appears in July and October respectively. As a whole, the eutrophication index in the low water period is higher than the high water period, and the maximum value is found in October which mainly due to the high chlorophyll-a concentration. Poyang Lake is at light eutrophication level from 2011 to 2012, and mesotrophic from 2013 to 2016. From the perspective of space, nutrient concentrations in the southern part of the lake is higher than the northern part in general, and chlorophyll-a and eutrophication index show the similar law. This paper makes a quantitative analysis for spatial and temporal variations of eutrophication which benefit the water management especially water pollution control in Poyang Lake</p>

scholarly journals Seasonal and diurnal variations of black carbon and organic carbon aerosols in Bangkok

2011 ◽  
Vol 116 (D15) ◽  
Author(s):  
L. K. Sahu ◽  
Y. Kondo ◽  
Y. Miyazaki ◽  
Prapat Pongkiatkul ◽  
N. T. Kim Oanh
Keyword(s):  
Organic Carbon ◽  
Black Carbon ◽  
Diurnal Variations ◽  
Seasonal And Diurnal Variations ◽  
Carbon Aerosols

scholarly journals Mars Global Ionosphere-Thermosphere Model: Solar cycle, seasonal, and diurnal variations of the Mars upper atmosphere

2015 ◽  
Vol 120 (2) ◽  
pp. 311-342 ◽  
Author(s):  
S. W. Bougher ◽  
D. Pawlowski ◽  
J. M. Bell ◽  
S. Nelli ◽  
T. McDunn ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Diurnal Variations ◽  
Upper Atmosphere ◽  
Seasonal And Diurnal Variations

scholarly journals Seasonal and diurnal variations in moisture, heat and CO2 fluxes over a typical steppe prairie in Inner Mongolia, China

2009 ◽  
Vol 13 (7) ◽  
pp. 987-998 ◽  
Author(s):  
Z. Gao ◽  
D. H. Lenschow ◽  
Z. He ◽  
M. Zhou
Keyword(s):  
Inner Mongolia ◽  
Surface Albedo ◽  
Sensible Heat Flux ◽  
Experimental Period ◽  
Diurnal Variations ◽  
Heat Fluxes ◽  
Co2 Fluxes ◽  
Sensible Heat ◽  
Eddy Covariance Method ◽  
Seasonal And Diurnal Variations

Abstract. In order to examine energy partitioning and CO2 exchange over a steppe prairie in Inner Mongolia, China, fluxes of moisture, heat and CO2 in the surface layer from June 2007 through June 2008 were calculated using the eddy covariance method. The study site was homogenous and approximately 1500 m×1500 m in size. Seasonal and diurnal variations in radiation components, energy components and CO2 fluxes are examined. Results show that all four radiation components changed seasonally, resulting in a seasonal variation in net radiation. The radiation components also changed diurnally. Winter surface albedo was higher than summer surface albedo because during winter the snow-covered surface increased the surface albedo. The seasonal variations in both sensible heat and CO2 fluxes were stronger than those of latent heat and soil heat fluxes. Sensible heat flux was the main consumer of available energy for the entire experimental period. The energy imbalance problem was encountered and the causes are analyzed.

scholarly journals The Diurnal Variations of GPS PWV near Poyang Lake in China during Midsummer

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Shanshan Wu ◽  
Haibo Zou ◽  
Junjie Wu
Keyword(s):  
Diurnal Variation ◽  
Global Positioning System ◽  
Diurnal Cycle ◽  
Poyang Lake ◽  
Precipitable Water ◽  
Diurnal Variations ◽  
Diurnal Cycles ◽  
Global Positioning ◽  
Variance Contribution ◽  
Gps Observation

With the 1 h-averaged data of atmospheric precipitable water vapor (PWV) for 2015–2018 retrieved from 18 ground-based Global Positioning System (GPS) observation stations near Poyang Lake (PL), China, the diurnal variations of the PWV during midsummer (July-August) are studied by the harmonic method. Results show that significant diurnal variations of PWV are found at the 18 GPS stations. The harmonics with 24 h cycle (diurnal cycle) over PL (i.e., Duchang and Poyang) and Nanchang city only have about 50% (or even smaller than 50%) of variance contribution with the amplitude of about 0.2 mm, while above 70% (or even 80%) of variance contribution occurs elsewhere around PL, with the amplitude of about 0.9 mm. The harmonics with diurnal cycles in most stations peak from afternoon to evening (i.e., 1200-2000 LST), but one exception is Duchang site, where the diurnal cycle peaks in the morning (i.e., 1000 LST). Moreover, the harmonics with 12 h cycle (semidiurnal cycle) have the relatively uniform amplitude of about 0.2 mm, but their variance contributions show uneven distribution, with the contributions of about or above 50% in PL and Nanchang city (the semidiurnal cycles peak about 0000 LST or 1200 LST) and below 30% (or even 10%) in other areas. The preliminary diagnosis analysis shows that the diurnal variation of the low-level (below 850 hPa) air temperature (increasing after the sunrise, decreasing after the sunset, and peaking around 1400-1800 LST) may be responsible for the diurnal cycle. Moreover, in PL (Duchang and Poyang) and Nanchang city, the effects (heating or cooling) of lake and urban, the diurnal variation of the 10 m wind over PL, and the acceleration of PL on overlying air also contributed to the diurnal variation of PWV.

Aldosterone Regulation in Primary Aldosteronism: Differences between Adenoma and Bilateral Hyperplasia

1976 ◽  
Vol 51 (s3) ◽  
pp. 329s-332s ◽  
Author(s):  
F. Mantero ◽  
M. Gion ◽  
D. Armanini ◽  
G. Opocher
Keyword(s):  
Primary Aldosteronism ◽  
Plasma Renin ◽  
Upright Position ◽  
Diurnal Variations ◽  
Upright Posture ◽  
Aldosterone Secretion ◽  
Predominant Role ◽  
Diurnal Patterns ◽  
Different Response ◽  
Dependent Mechanism

1. The diurnal patterns of plasma aldosterone, plasma renin activity (PRA), Cortisol and adreno-corticotrophic hormone (ACTH) in the supine and in the upright position have been studied in fourteen patients with primary aldosteronism, five with adenoma and nine with bilateral hyperplasia. Blood samples were drawn at intervals from 6 h to 30 min. 2. Supine patients with an adenoma showed marked diurnal variations of aldosterone, with maximal values at 08.00 hours and minimal values at 18.00 hours and secretory spurts beginning after 02.00 hours. Plasma Cortisol paralleled aldosterone, and ACTH seemed to anticipate aldosterone and Cortisol variations; PRA remained unchanged. In patients with hyperplasia, aldosterone was signicantly lower than in the adenoma group at 08.00 hours, and its decline during the day was less marked; fluctuations rather than secretory episodes were seen. 3. After patients assumed the upright posture, aldosterone remained unchanged or decreased in patients with adenoma, whereas it significantly increased in hyperplasia; PRA remained low, although a slight increment was seen in the latter group. The different response of aldosterone in the two groups was not modified by the administration of propranolol, apparently excluding a renin-dependent mechanism. On the other hand, dexamethasone seemed to affect the response of aldosterone to the upright posture in both groups; in adenoma there was a slight but significant increase, and in hyperplasia the usual rise was partially suppressed. 4. It is concluded that ACTH has a predominant role in regulating aldosterone secretion in primary aldosteronism due to adenoma, whereas its action in bilateral hyperplasia is only permissive.

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