scholarly journals Variability of Observed Energy Fluxes during Rain-on-Snow and Clear Sky Snowmelt in a Midlatitude Mountain Environment

2014 ◽  
Vol 15 (3) ◽  
pp. 1220-1237 ◽  
Author(s):  
J. Garvelmann ◽  
S. Pohl ◽  
M. Weiler
Keyword(s):  
Energy Balance ◽  
Longwave Radiation ◽  
Negative Energy ◽  
Spatiotemporal Variability ◽  
Shortwave Radiation ◽  
Positive Energy ◽  
Energy Fluxes ◽  
Area Index ◽  
Clear Sky ◽  
The Individual

Abstract Hourly observations of 65 snow monitoring stations were used to investigate the spatiotemporal variability of the surface energy balance during snowmelt in the Black Forest region of southwestern Germany. The study focuses on two rain-on-snow (ROS) events in December 2012 and a clear sky period at the beginning of March 2013 using the same study locations. ROS and clear sky were chosen since they are completely different snowmelt conditions in terms of energy exchanges and dynamics. The results show that snowmelt was dominated by turbulent exchanges at the open field sites and by both turbulent exchanges and net longwave radiation in the forest during ROS. The energy available for snowmelt can be almost identical at open and forest locations during ROS, and a constant energy flux even during night was directed toward the snowpack. During the clear sky conditions, net shortwave radiation was the dominating term in the open, whereas net shortwave and net longwave radiation were most important in the forest. A diurnal signal with positive energy balance during daylight and negative energy balance in the night was observed, with considerably reduced energy available for snowmelt in the forest. Furthermore, the stratified sampling design revealed the strong influence of the canopy and the topography at the locations on the observed energy fluxes. Elevation, aspect, and leaf area index (LAI) were the most important predictor variables during ROS, whereas aspect and LAI were most influential during the clear sky period. The study highlights the distinct spatial variability of the individual energy balance terms over a relatively small area during the differing snowmelt conditions.

scholarly journals Observations and simulations of the seasonal evolution of snowpack cold content and its relation to snowmelt and the snowpack energy budget

2018 ◽  
Vol 12 (5) ◽  
pp. 1595-1614 ◽  
Author(s):  
Keith S. Jennings ◽  
Timothy G. F. Kittel ◽  
Noah P. Molotch
Keyword(s):  
Energy Budget ◽  
Meteorological Data ◽  
Longwave Radiation ◽  
Negative Energy ◽  
Energy Deficit ◽  
Positive Energy ◽  
Primary Control ◽  
Energy Fluxes ◽  
Radiation Emission ◽  
Content Development

Abstract. Cold content is a measure of a snowpack's energy deficit and is a linear function of snowpack mass and temperature. Positive energy fluxes into a snowpack must first satisfy the remaining energy deficit before snowmelt runoff begins, making cold content a key component of the snowpack energy budget. Nevertheless, uncertainty surrounds cold content development and its relationship to snowmelt, likely because of a lack of direct observations. This work clarifies the controls exerted by air temperature, precipitation, and negative energy fluxes on cold content development and quantifies the relationship between cold content and snowmelt timing and rate at daily to seasonal timescales. The analysis presented herein leverages a unique long-term snow pit record along with validated output from the SNOWPACK model forced with 23 water years (1991–2013) of quality controlled, infilled hourly meteorological data from an alpine and subalpine site in the Colorado Rocky Mountains. The results indicated that precipitation exerted the primary control on cold content development at our two sites with snowfall responsible for 84.4 and 73.0 % of simulated daily gains in the alpine and subalpine, respectively. A negative surface energy balance – primarily driven by sublimation and longwave radiation emission from the snowpack – during days without snowfall provided a secondary pathway for cold content development, and was responsible for the remaining 15.6 and 27.0 % of cold content additions. Non-zero cold content values were associated with reduced snowmelt rates and delayed snowmelt onset at daily to sub-seasonal timescales, while peak cold content magnitude had no significant relationship to seasonal snowmelt timing. These results suggest that the information provided by cold content observations and/or simulations is most relevant to snowmelt processes at shorter timescales, and may help water resource managers to better predict melt onset and rate.

scholarly journals Estimation of Net Radiation using satellite based data inputs

2014 ◽  
Vol XL-8 ◽  
pp. 307-313 ◽  
Author(s):  
S. V. S. Sai Krishna ◽  
P. Manavalan ◽  
P. V. N. Rao
Keyword(s):  
Outgoing Longwave Radiation ◽  
Surface Air Temperature ◽  
Longwave Radiation ◽  
Surface Radiation ◽  
Shortwave Radiation ◽  
Net Radiation ◽  
Clear Sky ◽  
Statistical Measures ◽  
Indian Land ◽  
Radiation Fluxes

Daily net surface radiation fluxes are estimated for Indian land mass at spatial grid intervals of 0.1 degree. Two approaches are employed to obtain daily net radiation for four sample days viz., November 19, 2013, December 16, 2013, January 8, 2014 and March 20, 2014. Both the approaches compute net shortwave and net longwave fluxes, separately and sum them up to obtain net radiation. The first approach computes net shortwave radiation using daily insolation product of Kalpana VHRR and 15 days time composited broadband albedo product of Oceansat OCM2. The net outgoing longwave radiation is computed using Stefan Boltzmann equation corrected for humidity and cloudiness. In the second approach, instantaneous clear-sky net-shortwave radiation is estimated using computed clear-sky incoming shortwave radiation and the gridded MODIS 16-day time composited albedo product. The net longwave radiation is obtained by estimating outgoing and incoming longwave radiation fluxes, independently. In this, MODIS derived surface emissivity and skin temperature parameters are used for estimating outgoing longwave radiation component. In both the approaches, surface air temperature data required for estimation of net longwave radiation fluxes are extracted from India Meteorological Department’s (IMD) Automatic Weather Station (AWS) records. Estimates by the two different approaches are evaluated by comparing daily net radiation fluxes with CERES based estimates corresponding to the sample days, through statistical measures. The estimated all sky daily net radiation using the first approach compared well with CERES SYN1deg daily average net radiation with r<sup>2</sup> values of the order of 0.7 and RMS errors of the order of 8&ndash;16 w/m<sup>2</sup>.

scholarly journals Energy Balance Calculations for the Ablation Period 1982 at Vernagtferner. Oetztal Alps

1985 ◽  
Vol 6 ◽  
pp. 158-160 ◽  
Author(s):  
Heidi Escher-Vetter
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Air Temperature ◽  
Sensible Heat Flux ◽  
Longwave Radiation ◽  
Radiation Balance ◽  
Sensible Heat ◽  
The Individual ◽  
The Relationship ◽  
Climatic Pattern

In this paper, some features of energy balance terms will be discussed in respect to the melting capacity available at the surface of Vernagtferner in the Oetztal Alps. The climatic pattern of summer 1982 is described, then the method of calculating individual terms (shortwave and longwave radiation balance, sensible and latent heat flux) from records of radiation, air temperature, humidity and wind. The results of these calculations are discussed for ice, firn and snow areas of the glacier. In particular the relationship between the four terms is shown for 15 July 1982, the day with highest meltwater production in 1982. These values are then compared with the maximum values of the individual terms, showing that the highest meltwater production is caused by the combination of quite high values of the individual terms, but not of the absolutely highest ones. The importance of sensible heat flux for meltwater production in 1982 is discussed: comparison between meltwater production for the whole summer and measured runoff shows reasonable accordance.

Physiological and genetic differences between low and high index dairy cows

2001 ◽  
Vol 26 (1) ◽  
pp. 223-236 ◽  
Author(s):  
M. C. Lucy ◽  
B. A. Crooker
Keyword(s):  
Energy Balance ◽  
Dairy Cattle ◽  
Dairy Cows ◽  
Milk Production ◽  
Negative Energy ◽  
High Index ◽  
Negative Energy Balance ◽  
Positive Energy ◽  
Serum Concentrations ◽  
Days Open

AbstractSelection of dairy cattle for increased milk production has decreased some indices of reproductive efficiency. For example, days open are increased by one day for every 100 kg of increased milk yield per lactation. Some of the change in days open can be explained by delayed onset of oestrous cyclicity and lower conception rate to artificial insemination in cows with greater milk production. Despite these negative associations between milk production and reproduction, reproduction in herds of high producing dairy cattle is not necessarily compromised relative to reproduction in herds of low producing dairy cattle. This is because there is a large environmental effect on dairy reproduction. High producing herds generally have better management and better oestrous detection. Therefore, high producing dairy herds may partially overcome the antagonistic relationship between milk production and reproduction. Physiological mechanisms that lead to poorer reproduction in high producing cows are partially defined. Negative energy balance that occurs in high producing dairy cows can be associated with a delay in the initiation of ovarian cycles and the interval to first breeding. Many of the effects of negative energy balance on postpartum reproduction can be explained by decreased serum luteinizing hormone (LH) that is associated with negative energy balance. Serum LH increases as cows move toward positive energy balance and greater LH stimulates growth and ovulation of ovarian follicles. We have initiated studies to address physiological differences in high and low index dairy cows. The reproductive endocrinology of cows from a control line (5,900 kg milk/lactation) and a select line (10,900 kg milk/lactation) of dairy cows at the University of Minnesota was studied over a two-year period. Cows in Year 1 were similar for serum concentrations of LH, follicle stimulating hormone (FSH), and oestradiol (preovulatory period). In both years, serum concentrations of progesterone during luteal phases, however, were decreased in select cows. The Year 2 cows also had a delay in the return to oestrous cyclicity that was associated with reduced LH. The possibility that decreased progesterone causes infertility in dairy cows will require further study. Collectively, these data suggest that changes in blood progesterone concentrations may explain, partially, lower fertility in high index dairy cows.

scholarly journals Reconnaissance Study of glacier energy balance in North Greenland, 1993–94

1998 ◽  
Vol 44 (147) ◽  
pp. 239-247 ◽  
Author(s):  
Roger J. Braithwaite ◽  
Thomas Konzelmann ◽  
Christoph Marty ◽  
Ole B. Olesen
Keyword(s):  
Energy Balance ◽  
Field Experiments ◽  
Longwave Radiation ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Conductive Heat ◽  
Glacier Surface ◽  
West Greenland ◽  
North Greenland

AbstractReconnaissance energy-balance studies were made for the first time at two sites in North Greenland to compare with conditions in West Greenland. The field experiments were planned to save weight because it is expensive to operate in North Greenland. The larger energy components (incoming radiation and ablation) were measured for 55 days altogether, and the smaller components were evaluated by indirect methods, e.g. turbulent fluxes are calculated from air temperature, humidity and wind speed, to save the weight of instruments. The energy-balance model is “tuned" by choosing surface roughness and albedo to reduce the mean error between measured ablation and modelled daily melting. The error standard deviation for ablation is only ± 5 kg m−2d−1’, which is much lower than found in West Greenland, due to better instruments and modelling in the present study. Net radiation is the main energy source for melting in North Greenland but ablation is relatively low because sublimation and conductive-heat fluxes use energy that would otherwise be available for melting. There is a strong diurnal variation in ablation, mainly forced by variations in shortwave radiation and reinforced by nocturnal cooling of the ice surface by outgoing longwave radiation and sublimation. The model frequently predicts a frozen glacier surface at night even when air temperatures are positive.

scholarly journals Ghrelin affects the hypothalamus–pituitary–thyroid axis in humans by increasing free thyroxine and decreasing TSH in plasma

2010 ◽  
Vol 162 (6) ◽  
pp. 1059-1065 ◽  
Author(s):  
Michael Kluge ◽  
Stefan Riedl ◽  
Manfred Uhr ◽  
Doreen Schmidt ◽  
Xiaochi Zhang ◽  
...  
Keyword(s):  
Energy Balance ◽  
Plasma Levels ◽  
Feedback Inhibition ◽  
Area Under The Curve ◽  
Negative Energy ◽  
Free Thyroxine ◽  
Positive Energy ◽  
Free Triiodothyronine ◽  
Time Points ◽  
Hpt Axis

ObjectiveGhrelin promotes a positive energy balance, e.g. by increasing food intake. Stimulation of the activity of the hypothalamus–pituitary–thyroid (HPT) axis promotes a negative energy balance, e.g. by increasing energy expenditure. We therefore hypothesized that ghrelin suppresses the HPT axis in humans, counteracting its energy-saving effect.Design and methodsIn this single-blind, randomized, cross-over study, we determined secretion patterns of free triiodothyronine (fT3), free thyroxine (fT4), TSH, and thyroid-binding globulin (TBG) between 2000 and 0700 h in 20 healthy adults (10 males and 10 females, 25.3±2.7 years) receiving 50 μg ghrelin or placebo at 2200, 2300, 0000, and 0100 h.ResultsFT4 plasma levels were significantly higher after ghrelin administration than after placebo administration from 0000 h until 0620 h except for the time points at 0100, 0520, and 0600 h. TSH plasma levels were significantly lower from 0200 until the end of the study at 0700 h except for the time points at 0540, 0600, and 0620 h. The relative increase of fT4 (area under the curve (AUC) 0130–0700 h (ng/dl×min): placebo: 1.31±0.03; ghrelin: 1.39±0.03; P=0.001) was much weaker than the relative decrease of TSH (AUC 0130–0700 h (mIU/ml×min): placebo: 1.74±0.12; ghrelin: 1.32±0.12; P=0.007). FT3 and TBG were not affected.ConclusionsThis is the first study to report that ghrelin affects the HPT axis in humans. The early fT4 increase was possibly induced by direct ghrelin action on the thyroid where ghrelin receptors have been identified. The TSH decrease might have been caused by ghrelin-mediated inhibition at hypothalamic level by feedback inhibition through fT4, or both.

scholarly journals Investigation of negative energy balance and postpartum anoestrus in an intensive dairy farm from the Chinese province of Heilongjiang

2017 ◽  
Vol 86 (1) ◽  
pp. 59-65
Author(s):  
Ziling Fan ◽  
Shi Shu ◽  
Chuchu Xu ◽  
Changsheng Li ◽  
Xinhuan Xiao ◽  
...  
Keyword(s):  
Energy Balance ◽  
Dairy Farm ◽  
Negative Energy ◽  
Negative Energy Balance ◽  
Positive Energy ◽  
Hydroxybutyric Acid ◽  
Ovarian Status ◽  
Positive Energy Balance ◽  
Chinese Province ◽  
The Relationship

The aim of this investigation was to determine the relationship between postpartum anoestrus and negative energy balance in an intensive dairy farm from the Heilongjiang Province, China. At 14 to 21 d after parturition, 100 cows were randomly selected and their plasma indices, including β-hydroxybutyric acid, non-esterified fatty acid, and glucose were measured. Cows were assigned to a positive energy balance group (n = 37) and a negative energy balance group (n = 36) based on their β-hydroxybutyric acid concentrations (> 1.20 mmol/l). The two groups of cows were examined by B-mode ultrasonography and rectal examination from 60 to 90 d after parturition to identify the ovarian status of oestrous and anoestrous animals. The incidences of negative energy balance and positive energy balance were 49 and 57%, respectively, from14 to 21 d after parturition. From 60 to 90 d after parturition, 94.4% of the negative energy balance group were in anoestrus and 5.6% were in oestrus, while 62.2% of the positive energy balance group were in anoestrus and 37.8% were in oestrus. Furthermore, the proportion of inactive ovaries in the negative energy balance group was 61.8%. In conclusion, the negative energy balance is an important factor causing inactive ovaries in high-yielding dairy cows.

scholarly journals Effect of negative energy balance on plasma metabolites, minerals, hormones, cytokines and ovarian follicular growth rate in Holstein dairy cows

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yuxi Song ◽  
Zhijie Wang ◽  
Chang Zhao ◽  
Yunlong Bai ◽  
Cheng Xia ◽  
...  
Keyword(s):  
Growth Rate ◽  
Growth Factor ◽  
Energy Balance ◽  
Negative Energy ◽  
Negative Energy Balance ◽  
Plasma Metabolites ◽  
Positive Energy ◽  
Fibroblast Growth Factor 21 ◽  
Insulin Like Growth Factor ◽  
Follicular Growth

Abstract Introduction The aim of this study was to evaluate the effect of negative energy balance (NEB) on the final growth of the dominant ovarian follicle in Holstein cows. Material and Methods Cows at 14 to 21 d postpartum from an intensive dairy farm were randomly selected and allocated into a positive energy balance group (PEB, with β-hydroxybutyric acid (BHBA) level < 1.2 mmol/L, n = 15) and an NEB group (BHBA > 1.2 mmol/L, n = 15). Plasma samples were collected at 21, 50 and 55 d postpartum to assess the concentrations of energy metabolites, minerals, hormones and cytokines. Ovaries were examined by transrectal ultrasound on days 50 and 55 (120 hours later) to evaluate the diameter of the largest follicle. Results Compared with PEB cows, there were a more severe body condition loss and a lower milk yield in NEB cows (P < 0.05) and these had greater concentrations of plasma BHBA, non-esterified fatty acids, triglycerides, urea nitrogen, growth hormone, interleukin 6, and fibroblast growth factor 21 and lesser concentrations of plasma glucose, total cholesterol, insulin, insulin-like growth factor 1, insulin-like growth factor binding protein 3, leptin, brain-derived neurotrophic factor and angiopoietin-like protein 8 on d 21 (P < 0.05), while plasma minerals were not affected by energy status (P > 0.05). These changes persisted until the end of the study period (50–55 days postpartum) resulting in a lower follicular growth rate for cows in the NEB than the PEB group. Conclusion These observations indicate that follicular growth rate is associated with measurable changes in energy metabolite, hormone and cytokine concentrations caused by early postpartum NEB.

Longwave Radiation Corrections for the OMNI Buoy Network

2021 ◽  
Keyword(s):  
Indian Ocean ◽  
Longwave Radiation ◽  
Field Measurements ◽  
North Indian Ocean ◽  
Shortwave Radiation ◽  
Data Logger ◽  
Clear Sky ◽  
The Difference ◽  
Radiation Measurements ◽  
Moored Buoy

Abstract The inception of a moored buoy network in the northern Indian Ocean in 1997 paved the way for systematic collection of longterm time series observations of meteorological and oceanographic parameters. This buoy network was revamped in 2011 with OMNI (Ocean Moored buoy Network for north Indian Ocean) buoys fitted with additional sensors to better quantify the air-sea fluxes. An inter-comparison of OMNI buoy measurements with the nearby WHOI mooring during the year 2015 revealed an overestimation of downwelling longwave radiation (LWR↓). Analysis of the OMNI and WHOI radiation sensors at a test station at NIOT during 2019 revealed that the accurate and stable amplification of the thermopile voltage records along with the customized data logger in the WHOI system results in better estimations of LWR↓. The offset in NIOT measured LWR↓ is estimated firstly by segregating the LWR↓ during clear sky conditions identified using the downwelling shortwave radiation measurements from the same test station, and secondly, finding the offset by taking the difference with expected theoretical clear sky LWR↓. The corrected LWR↓ exhibited good agreement with that of collocated WHOI measurements, with a correlation of 0.93. This method is applied to the OMNI field measurements and again compared with the nearby WHOI mooring measurements, exhibiting a better correlation of 0.95. This work has led to the revamping of radiation measurements in OMNI buoys and provides a reliable method to correct past measurements and improve estimation of air-sea fluxes in the Indian Ocean.

The Physics of Radiation

2019 ◽  
pp. 44-57
Author(s):  
Han Dolman
Keyword(s):  
Energy Balance ◽  
Radiative Forcing ◽  
Longwave Radiation ◽  
Shortwave Radiation ◽  
Tropospheric Temperature ◽  
The Sun ◽  
Current Estimate ◽  
Maximum Emission ◽  
Boltzmann Law ◽  
Gas Effect

This chapter discusses radiation, radiative transfer and the greenhouse effect. It starts by analysing radiation from a blackbody, identifying the key difference between shortwave radiation from the Sun and longwave radiation from Earth. It then describes the Planck function, which calculates the intensity of radiation emitted by a blackbody; the Stefan–Boltzmann law, which shows how changing the temperature of a blackbody affects the rate at which it emits radiation; Wien’s law, which calculates the wavelength of maximum emission; and Kirchhoff’s law of emission and absorption. These are then used to show the effect of increasing longwave-absorbing gases in the troposphere on the lower tropospheric temperature: the greenhouse gas effect. The chapter then describes the aspects of scattering, emission and absorption that are needed to understand the interaction of radiation with greenhouse gases. The chapter concludes by discussing radiative forcing and showing the current estimate of Earth’s energy balance.

Sign in / Sign up

Export Citation Format

Share Document