scholarly journals Ramdas layer and thermal wave during winter period

MAUSAM ◽  
2022 ◽  
Vol 52 (4) ◽  
pp. 697-702
Author(s):  
S. ABRAHAM THAMBI RAJA ◽  
G. RENUKA ◽  
K. RETNAKUMARI
Keyword(s):  
Mathematical Model ◽  
Heat Flux ◽  
Energy Balance ◽  
Thermal Wave ◽  
Soil Surface ◽  
Soil Heat Flux ◽  
Rate Of Change ◽  
Winter Period ◽  
Maximum Height ◽  
Lower Height

Earlier works on Ramdas Layer were about its certainty, its existence, energy balance on the layer and a matching mathematical model. We, first identified it in Thiruvananthapuram, Kerala, for eight days during a fortnight study on soil heat flux. A lifted minimum in temperature could have implications in agriculture and horticulture and so with a view to finding out a range of height through which Ramdas layer occurs, Ramdas-max, Ramdas-min are identified. On 24 January 1994, Ramdas layer occurred at a maximum height of 0.8m from the surface and the day is labeled as Ramdas-max. On 1 February 1994, it occurred at a lower height of 0.4m from the surface and the day is labeled as Ramdas-min.   The thermal wave at the ground and at 0.05m depth, the range of thermal wave, its relationship with Ramdas layer, the temperature profile, the rate of change of heat in that layer with that at the surface and the subsoil heat flux at the sub-soil surface stratum(surface-0.05m) during R~mdas-max and Ramdas-min are duly compared and discussed.

scholarly journals Radiation and energy balance of lettuce culture inside a polyethylene greenhouse

1999 ◽  
Vol 34 (10) ◽  
pp. 1775-1786 ◽  
Author(s):  
Valéria de Almeida Frisina ◽  
João Francisco Escobedo
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Global Radiation ◽  
Soil Surface ◽  
Soil Heat Flux ◽  
Short Wave ◽  
Wave Radiation ◽  
Radiation Balance ◽  
Net Radiation ◽  
Crop Cycle

The objective of this paper was to describe the radiation and energy balance, during the lettuce (Lactuca sativa, L. cv. Verônica) crop cycle inside a polyethylene greenhouse. The radiation and energy balance was made inside a tunnel greenhouse with polyethylene cover (100 mum) and in an external area, both areas with 35 m². Global, reflected and net radiation, soil heat flux and air temperature (dry and humid) were measured during the crop cycle. A Datalogger, which operated at 1 Hz frequency, storing 5 minutes averages was utilized. The global (K<FONT FACE=Symbol>¯</FONT>) and reflected (K<FONT FACE=Symbol></FONT>) radiations showed that the average transmission of global radiation (K<FONT FACE=Symbol>¯</FONT>in / K<FONT FACE=Symbol>¯</FONT>ex) was almost constant, near to 79.59%, while the average ratio of reflected radiation (K<FONT FACE=Symbol></FONT>in / K<FONT FACE=Symbol></FONT>ex) was 69.21% with 8.47% standard-deviation. The normalized curves of short-wave net radiation, in relation to the global radiation (K*/ K<FONT FACE=Symbol>¯</FONT>), found for both environments, were almost constant at the beginning of cycle; this relation decreased in the final stage of culture. The normalized relation (Rn/ K<FONT FACE=Symbol>¯</FONT>) was bigger in the external area, about 12%, when the green culture covered the soil surface. The long-wave radiation balance average (L*) was bigger outside, about 50%. The energy balance, estimated in terms of vertical fluxes, showed that, for the external area, in average, 83.07% of total net radiation was converted in latent heat evaporation (LE), and 18% in soil heat flux (G), and 9.96% in sensible heat (H), while inside of the greenhouse, 58.71% of total net radiation was converted in LE, 42.68% in H, and 28.79% in G.

scholarly journals Bower ratio-energy balance associated errors in vineyards under dripping irrigation

2007 ◽  
Vol 22 (2) ◽  
pp. 233-240 ◽  
Author(s):  
José Monteiro Soares ◽  
Pedro Vieira De Azevedo ◽  
Bernado Barbosa Da Silva
Keyword(s):  
Energy Balance ◽  
Soil Surface ◽  
Field Measurements ◽  
Bowen Ratio ◽  
Global Solar Radiation ◽  
Soil Heat Flux ◽  
Vitis Vinifera L ◽  
Data Logger ◽  
And Storage ◽  
Ratio Energy

This study was conducted at the Bebedouro Experimental Station in Petrolina-PE, Brazil, to evaluate the errors associated to the application of the Bowen ratio-energy balance in a 3-years old vineyard (Vitis vinifera, L), grown in a trellis system, irrigated by dripping. The field measurements were taken during fruiting cycle (July to November, 2001), which was divided into eigth phenological stages. A micrometeorological tower was mounted in a grape-plants row in which sensors of net radiation, global solar radiation and wind speed were installed at about 1.0 m above the canopy. Also in the tower, two psicometers were installed at two levels (0.5 and 1.8 m) above the vineyard canopy. Two soil heat flux plates were buried at 0.02 m beneath the soil surface. All these sensors were connected to a Data logger 21 X of Campbell Scientific Inc., programmed for collecting data once every 5 seconds and storage averages for every 15 minutes. A comparative analysis were made among four Bowen ratio accepting/rejecting rules, according to the methodology proposed by Spano et al. (2000): betar1 - values of beta calculated by Bowen (1926) equation; betar2 - values of beta as proposed by Verma et al. (1978) equation; betar3 - exclusion of the beta values obtained as recommended by Unland et al. (1996) and betar4 - exclusion of the beta values calculated as proposed by Bowen (1926), out of the interval (-0.7 < beta < 0.7). Constacted that the Unland et al. (1996) and Soares (2003) accepting/rejection rules were better than that of Verma et al. (1978) for attenuating the advective effects on the calculations of the Bowen ratio. The comparison of betar1 with betar2 rules showed that the statistical errors reaching maximum values of 0.015. When comparing betar1 with betar3 e betar4, the beta errors reaching maximum values of 5.80 and 3.15, respectively.

ENERGY BALANCE OVER PRAIRIE GRASS

1972 ◽  
Vol 52 (2) ◽  
pp. 215-225 ◽  
Author(s):  
LAWRENCE C. NKEMDIRIM ◽  
SHUJI YAMASHITA
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Bowen Ratio ◽  
Soil Heat Flux ◽  
Daily Basis ◽  
Net Radiation ◽  
Large Variability ◽  
Prairie Grass ◽  
Latent Flux ◽  
Evaporative Flux

The energy balance over prairie grass was computed for four cloudless days using the Bowen ratio and the Fourier heat conduction equation. For the 3 advection-free days evaporation accounted for an average of 55% of daytime net radiation. Turbulent flux of heat and soil heat flux shared the remaining portion almost equally. Hourly evaporation can be related to net radiation by the empirical equation: E = 1.2 + 0.75 R cal cm−2 hr−1, where E is the evaporative flux and R the net radiation. The patterns of the soil heat flux was fairly steady from day to day. The relation between hourly flux of sensible heat and soil heat flux was linear on a daily basis. The linearity of the two fluxes when the hourly value for the whole period of investigation was pooled was poor. The proportion of net radiation used as latent flux and sensible flux showed large variability under advection conditions.

scholarly journals Estimation of surface energy fluxes in the Arctic tundra using the remote sensing thermal-based Two-Source Energy Balance model

2017 ◽  
Vol 21 (3) ◽  
pp. 1339-1358 ◽  
Author(s):  
Jordi Cristóbal ◽  
Anupma Prakash ◽  
Martha C. Anderson ◽  
William P. Kustas ◽  
Eugénie S. Euskirchen ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Heat Flux ◽  
Energy Balance ◽  
Surface Energy ◽  
Arctic Tundra ◽  
Soil Heat Flux ◽  
Energy Balance Model ◽  
The Arctic ◽  
Balance Model ◽  
Climate Conditions

Abstract. The Arctic has become generally a warmer place over the past decades leading to earlier snow melt, permafrost degradation and changing plant communities. Increases in precipitation and local evaporation in the Arctic, known as the acceleration components of the hydrologic cycle, coupled with land cover changes, have resulted in significant changes in the regional surface energy budget. Quantifying spatiotemporal trends in surface energy flux partitioning is key to forecasting ecological responses to changing climate conditions in the Arctic. An extensive local evaluation of the Two-Source Energy Balance model (TSEB) – a remote-sensing-based model using thermal infrared retrievals of land surface temperature – was performed using tower measurements collected over different tundra types in Alaska in all sky conditions over the full growing season from 2008 to 2012. Based on comparisons with flux tower observations, refinements in the original TSEB net radiation, soil heat flux and canopy transpiration parameterizations were identified for Arctic tundra. In particular, a revised method for estimating soil heat flux based on relationships with soil temperature was developed, resulting in significantly improved performance. These refinements result in mean turbulent flux errors generally less than 50 W m−2 at half-hourly time steps, similar to errors typically reported in surface energy balance modeling studies conducted in more temperate climatic regimes. The MODIS leaf area index (LAI) remote sensing product proved to be useful for estimating energy fluxes in Arctic tundra in the absence of field data on the local biomass amount. Model refinements found in this work at the local scale build toward a regional implementation of the TSEB model over Arctic tundra ecosystems, using thermal satellite remote sensing to assess response of surface fluxes to changing vegetation and climate conditions.

Comparison of energy fluxes from eddy covariance and scintillometer over an agricultural field

2020 ◽  
Author(s):  
Matěj Orság ◽  
Milan Fischer ◽  
Josef Eitzinger ◽  
Miroslav Trnka
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Eddy Covariance ◽  
Latent Heat ◽  
Soil Heat Flux ◽  
Radiation Balance ◽  
Energy Balance Closure ◽  
Sensible Heat ◽  
Agricultural Field ◽  
Available Energy

&lt;p&gt;In this study we compare turbulent energy fluxes obtained from eddy covariance (EC) (LI-7500A, LI-COR + Windmaster, Gill Instruments) and large aperture scintillometer (BLS900, Scintec) over an agricultural field (wheat field, straw and bare soil). As the EC method provides direct measurements of sensible heat (H&lt;sub&gt;EC&lt;/sub&gt;) and latent heat (LE&lt;sub&gt;EC&lt;/sub&gt;) fluxes we use it as a reference method. The EC method enables to determine fluxes within a footprint centered around the point of measurement in the middle of the field. The scintillometer provides an estimation of sensible heat flux (H&lt;sub&gt;SC&lt;/sub&gt;), derived from air refractive index fluctuation integrated over the measurement path length, in this case 570 m diagonally across whole field. The reference measurements of the radiation balance components consist of 4-component net radiometer for net radiation (Rn) (NR01, Hukseflux), three soil heat flux plates for soil heat flux (G) monitoring (HFP01, Hukseflux), including thermocouples for quantification of the heat storage above the soil heat flux plates. The scintillometer-based latent heat (LE&lt;sub&gt;SC&lt;/sub&gt;) is calculated as a residuum from available energy (Rn-G) and H&lt;sub&gt;SC&lt;/sub&gt;, provided by scintillometer. The measurement of radiation balance components was located at the top of 3.5 m mast with the EC system, while the soil heat flux plates were collocated around in 5 cm depth. The site is a flat, rectangular agricultural field (app. 16.5 ha), in the north-eastern Austria, Danube river lowland (48.21N, 16.622E), sown with winter wheat during growing season 2019. The measurement campaign was established in February 2019 with aim for multi-seasonal monitoring. The EC measurement height is 2.7 m, the scintillometer transmitter and receiver are fixed on 4 m masts, facing towards each other from NW and SE corners of the field.&lt;/p&gt;&lt;p&gt;Comparison of the EC-based turbulent fluxes (H&lt;sub&gt;EC&lt;/sub&gt;+LE&lt;sub&gt;EC&lt;/sub&gt;) and the available energy (Rn-G) during the period March to Mid-June showed a very good agreement, resulting in the energy balance closure of 0.96 (R&lt;sup&gt;2 &lt;/sup&gt;= 0.93). This suggest high accuracy and robustness of the measurement setup together with the ability of the EC method to capture all scales of eddies responsible for energy transport at this site. The comparison of methods indicates that H&lt;sub&gt;SC&lt;/sub&gt; overestimated H&lt;sub&gt;EC&lt;/sub&gt; by 10 % (R&lt;sup&gt;2 &lt;/sup&gt;= 0.74) and LE&lt;sub&gt;SC&lt;/sub&gt; underestimated LE&lt;sub&gt;EC&lt;/sub&gt; by 13 % (R&lt;sup&gt;2 &lt;/sup&gt;= 0.81). Related to Rn, the H&lt;sub&gt;EC&lt;/sub&gt;, LE&lt;sub&gt;EC&lt;/sub&gt; and G fluxes accounted for 22 % (R&lt;sup&gt;2 &lt;/sup&gt;= 0.53), 59 % (R&lt;sup&gt;2 &lt;/sup&gt;= 0.70) and 15% (R&lt;sup&gt;2 &lt;/sup&gt;= 0.62) of the Rn flux, respectively. We assume that the combination of EC and scintillometer method has a potential to bring deeper insight into the analysis of the energy balance closure problem.&lt;/p&gt;

scholarly journals Heat storage in forest biomass improves energy balance closure

2010 ◽  
Vol 7 (1) ◽  
pp. 301-313 ◽  
Author(s):  
A. Lindroth ◽  
M. Mölder ◽  
F. Lagergren
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Latent Heat ◽  
Heat Storage ◽  
Soil Heat Flux ◽  
Energy Balance Closure ◽  
Sensible Heat ◽  
Net Radiation ◽  
Tree Biomass ◽  
Stable Conditions

Abstract. Temperature measurements in trunks and branches in a mature ca. 100 years-old mixed pine and spruce forest in central Sweden were used to estimate the heat storage in the tree biomass. The estimated heat flux in the sample trees and data on biomass distributions were used to scale up to stand level biomass heat fluxes. The rate of change of sensible and latent heat storage in the air layer below the level of the flux measurements was estimated from air temperature and humidity profile measurements and soil heat flux was estimated from heat flux plates and soil temperature measurements. The fluxes of sensible and latent heat from the forest were measured with an eddy covariance system in a tower. The analysis was made for a two-month period in summer of 1995. The tree biomass heat flux was the largest of the estimated storage components and varied between 40 and −35 W m−2 on summer days with nice weather. Averaged over two months the diurnal maximum of total heat storage was 45 W m−2 and the minimum was −35 W m−2. The soil heat flux and the sensible heat storage in air were out of phase with the biomass flux and they reached maximum values that were about 75% of the maximum of the tree biomass heat storage. The energy balance closure improved significantly when the total heat storage was added to the turbulent fluxes. The slope of a regression line with sum of fluxes and storage as independent and net radiation as dependent variable, increased from 0.86 to 0.95 for half-hourly data and the scatter was also reduced. The most significant finding was, however, that during nights with strongly stable conditions when the sensible heat flux dropped to nearly zero, the total storage matched the net radiation very well. Another interesting result was that the mean energy imbalance started to increase when the Richardson number became more negative than ca. −0.1. In fact, the largest energy deficit occurred at maximum instability. Our conclusion is that eddy covariance measurements can function well during stable conditions but that the functioning under strong instabilities might be a so far unforeseen problem.

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