ROLE OF METEOROLOGY AND LITHOLOGY IN THE TEMPORAL VARIATION OF THE OUTDOOR RADON LEVEL

2019 ◽  
Vol 184 (3-4) ◽  
pp. 474-478 ◽  
Author(s):  
D Kikaj ◽  
T Kovács ◽  
J Vaupotič
Keyword(s):  
Radon Concentration ◽  
Cloud Cover ◽  
Meteorological Parameters ◽  
Radon Level ◽  
Clear Sky ◽  
Cloudy Condition ◽  
Weather Changes ◽  
Sky Conditions ◽  
The Relationship

Abstract The outdoor radon concentration was monitored together with the meteorological parameters at two contrasting complex topographies: sub-Alpine basin (SA) and sub-Mediterranean valley (SM) in winter (December 2017–February 2018) and summer (June–August 2018). The time series for each site and each season are evaluated in three different ways: (i) clear-sky and cloudy condition together, (ii) clear-sky conditions only (cloud cover <20%) and (iii) cloudy condition only (cloud cover >20%), and compared to the expected atmospheric boundary layer (ABL) ‘mixing volume’ caused by meteorological changes. The results have confirmed the sensitivity of diurnal and seasonal radon concentration to the expected ABL ‘mixing volume’ at the two selected sites. The relationship is more pronounced in calm clear-sky conditions. Cloudy conditions are associated with fast weather changes, when the ABL is well mixed and hourly mean radon concentrations do not follow the typical diurnal trend.

scholarly journals Climatological Features of the Weakly and Very Stably Stratified Nocturnal Boundary Layers. Part II: Regime Occupation and Transition Statistics and the Influence of External Drivers

2019 ◽  
Vol 76 (11) ◽  
pp. 3485-3504 ◽  
Author(s):  
Carsten Abraham ◽  
Adam H. Monahan
Keyword(s):  
Complex Terrain ◽  
Cloud Cover ◽  
Companion Paper ◽  
Statistical Features ◽  
Clear Sky ◽  
Cloud Coverage ◽  
Weakly Stable ◽  
Sky Conditions ◽  
Regime Transitions

Abstract In a companion paper hidden Markov model (HMM) analyses have been conducted to classify the nocturnal stably stratified boundary layer (SBL) into weakly stable (wSBL) and very stable (vSBL) conditions at different tower sites on the basis of long-term Reynolds-averaged mean data. The resulting HMM regime sequences allow analysis of long-term (climatological) SBL regime statistics. In particular, statistical features of very persistent wSBL and vSBL nights, in which a single regime lasts for the entire night, are contrasted with those of nights with SBL regime transitions. The occurrence of very persistent nights is seasonally dependent and more likely in homogeneous surroundings than in regions with complex terrain. When transitions occur, their timing is not seasonally dependent, but transitions are enhanced close to sunset (for land-based sites). The regime event durations depict remarkably similar distributions across all stations with peaks in transition likelihood approximately 1–2 h after a preceding transition. At Cabauw in the Netherlands, very persistent wSBL and vSBL nights are usually accompanied by overcast conditions with strong geostrophic winds Ugeo or clear-sky conditions with weak Ugeo, respectively. In contrast, SBL regime transitions can neither be linked to magnitudes in Ugeo and cloud coverage nor to specific tendencies in Ugeo. However, regime transitions can be initiated by changes in low-level cloud cover.

scholarly journals Variability and trend of diurnal temperature range in China and their relationship to total cloud cover and sunshine duration

2013 ◽  
Vol 31 (5) ◽  
pp. 795-804 ◽  
Author(s):  
X. Xia
Keyword(s):  
Diurnal Temperature Range ◽  
Cloud Cover ◽  
Sunshine Duration ◽  
Radiative Effect ◽  
Total Cloud Cover ◽  
Diurnal Temperature ◽  
Temperature Range ◽  
Clear Sky ◽  
Sky Conditions

Abstract. This study aims to investigate the effect of total cloud cover (TCC) and sunshine duration (SSD) in the variation of diurnal temperature range (DTR) in China during 1954–2009. As expected, the inter-annual variation of DTR was mainly determined by TCC. Analysis of trends of 30-year moving windows of DTR and TCC time series showed that TCC changes could account for that of DTR in some cases. However, TCC decreased during 1954–2009, which did not support DTR reduction across China. DTRs under sky conditions such as clear, cloudy and overcast showed nearly the same decreasing rate that completely accounted for the overall DTR reduction. Nevertheless, correlation between SSD and DTR was weak and not significant under clear sky conditions in which aerosol direct radiative effect should be dominant. Furthermore, 30–60% of DTR reduction was associated with DTR decrease under overcast conditions in south China. This implies that aerosol direct radiative effect appears not to be one of the main factors determining long-term changes in DTR in China.

Terrestrial Solar Radiation

2017 ◽  
pp. 191-293
Keyword(s):  
Solar Radiation ◽  
Horizontal Plane ◽  
Cloud Cover ◽  
Weather Conditions ◽  
Clear Sky ◽  
Solar Tracking ◽  
Sky Conditions ◽  
The Impact ◽  
Estimation Models

After shading a light on the extraterrestrial solar radiation in the chapter 3 it is important to evaluate the global terrestrial solar radiation and its components. The information on terrestrial solar radiation is required in several different forms depending on the kinds of calculations and kind of application that are to be done. Of course, terrestrial solar radiation on the horizontal plane depends on the different weather conditions such as cloud cover, relative humidity, and ambient temperature. Therefore, the impact of the atmosphere on solar radiation should be considered. One of the most important points of terrestrial solar radiation evaluation is its determination during clear sky conditions. Therefore, in this chapter, the equations that determine the air mass basing on available theories are given and the clear sky conditions are introduced with shading a light on the previous work in identifying clear sky conditions. Taking into consideration that, clear sky solar radiation estimation is of great importance for solar tracking, a detailed review of main available models is given in this chapter. As daily, monthly, seasonally, biannually and yearly mean daily solar radiations are required information for designing and installing long term tracking systems, different available methods are commented regarding their applicability for the estimation of solar radiation information in the desired format from the data that are available. An important accent is paid also on the assessment and comparison of monthly mean daily solar radiation estimation models.

scholarly journals Experimental and modeled UV erythemal irradiance under overcast conditions: the role of cloud optical depth

2012 ◽  
Vol 12 (8) ◽  
pp. 21241-21266
Author(s):  
M. Antón ◽  
L. Alados-Arboledas ◽  
J. L. Guerrero-Rascado ◽  
M. J. Costa ◽  
J. C. Chiu ◽  
...  
Keyword(s):  
Optical Depth ◽  
Relative Difference ◽  
Visible Range ◽  
Exponential Dependence ◽  
Cloud Optical Depth ◽  
Clear Sky ◽  
Modification Factor ◽  
High Bias ◽  
Sky Conditions

Abstract. This paper evaluates the relationship between the cloud modification factor (CMF) in the ultraviolet erythemal range and the cloud optical depth (COD) retrieved from the Aerosol Robotic Network (AERONET) "cloud mode" algorithm under overcast cloudy conditions (confirmed with sky images) at Granada (Spain). Empirical CMF showed a clear exponential dependence on experimental COD values, decreasing approximately from 0.7 for COD = 10 to 0.25 for COD = 50. In addition, these COD measurements were used as input in the LibRadtran radiative transfer code allowing the simulation of CMF values for the selected overcast cases. The modeled CMF exhibited a dependence on COD similar to the empirical CMF, but modeled values present a strong underestimation with respect to the empirical factors (mean bias of 22%). To explain this high bias, an exhaustive comparison between modeled and experimental UV erythemal irradiance (UVER) data was performed. This exercise revealed that a significant part of the bias (~8%) may be related to code's overestimation of the experimental data for clear-sky conditions. The rest of the bias (~14%) may be attributed to the substantial underestimation of modeled UVER with respect to experimental UVER under overcast conditions, although the correlation between both dataset was high (R2 ~0.93). A sensitive test showed that the main responsible for that underestimation is the experimental AERONET COD used as input in the simulations, which has been retrieved from zenith radiances in the visible range. In this sense, effective COD in the erythemal interval were derived from an iteration procedure based on searching the best match between modeled and experimental UVER values for each selected overcast case. These effective COD values were smaller than AERONET COD data in about 80% of the overcast cases with a mean relative difference of 22%.

scholarly journals Observational Characterization of the Downward Atmospheric Longwave Radiation at the Surface in the City of São Paulo

2010 ◽  
Vol 49 (12) ◽  
pp. 2574-2590 ◽  
Author(s):  
Eduardo Barbaro ◽  
Amauri P. Oliveira ◽  
Jacyra Soares ◽  
Georgia Codato ◽  
Maurício J. Ferreira ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Diurnal Variation ◽  
Planetary Boundary Layer ◽  
Air Temperature ◽  
Sao Paulo ◽  
São Paulo ◽  
Effective Emissivity ◽  
Clear Sky ◽  
Sky Conditions ◽  
The Relationship

Abstract This work describes the seasonal and diurnal variations of downward longwave atmospheric irradiance (LW) at the surface in São Paulo, Brazil, using 5-min-averaged values of LW, air temperature, relative humidity, and solar radiation observed continuously and simultaneously from 1997 to 2006 on a micrometeorological platform, located at the top of a 4-story building. An objective procedure, including 2-step filtering and dome emission effect correction, was used to evaluate the quality of the 9-yr-long LW dataset. The comparison between LW values observed and yielded by the Surface Radiation Budget project shows spatial and temporal agreement, indicating that monthly and annual average values of LW observed in one point of São Paulo can be used as representative of the entire metropolitan region of São Paulo. The maximum monthly averaged value of the LW is observed during summer (389 ± 14 W m−2; January), and the minimum is observed during winter (332 ± 12 W m−2; July). The effective emissivity follows the LW and shows a maximum in summer (0.907 ± 0.032; January) and a minimum in winter (0.818 ± 0.029; June). The mean cloud effect, identified objectively by comparing the monthly averaged values of the LW during clear-sky days and all-sky conditions, intensified the monthly average LW by about 32.0 ± 3.5 W m−2 and the atmospheric effective emissivity by about 0.088 ± 0.024. In August, the driest month of the year in São Paulo, the diurnal evolution of the LW shows a minimum (325 ± 11 W m−2) at 0900 LT and a maximum (345 ± 12 W m−2) at 1800 LT, which lags behind (by 4 h) the maximum diurnal variation of the screen temperature. The diurnal evolution of effective emissivity shows a minimum (0.781 ± 0.027) during daytime and a maximum (0.842 ± 0.030) during nighttime. The diurnal evolution of all-sky condition and clear-sky day differences in the effective emissivity remain relatively constant (7% ± 1%), indicating that clouds do not change the emissivity diurnal pattern. The relationship between effective emissivity and screen air temperature and between effective emissivity and water vapor is complex. During the night, when the planetary boundary layer is shallower, the effective emissivity can be estimated by screen parameters. During the day, the relationship between effective emissivity and screen parameters varies from place to place and depends on the planetary boundary layer process. Because the empirical expressions do not contain enough information about the diurnal variation of the vertical stratification of air temperature and moisture in São Paulo, they are likely to fail in reproducing the diurnal variation of the surface emissivity. The most accurate way to estimate the LW for clear-sky conditions in São Paulo is to use an expression derived from a purely empirical approach.

scholarly journals Cloudiness Information Services for Solar Energy Management in West Africa

Atmosphere ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 857
Author(s):  
Derrick Kwadwo Danso ◽  
Sandrine Anquetin ◽  
Arona Diedhiou ◽  
Rabani Adamou
Keyword(s):  
Solar Radiation ◽  
Solar Energy ◽  
West Africa ◽  
Cloud Cover ◽  
Shortwave Radiation ◽  
Surface Solar Radiation ◽  
Clear Sky ◽  
Incoming Solar Radiation ◽  
Sahel Region ◽  
Sky Conditions

In West Africa (WA), interest in solar energy development has risen in recent years with many planned and ongoing projects currently in the region. However, a major drawback to this development in the region is the intense cloud cover that reduces the incoming solar radiation when present and causes fluctuations in solar power production. Therefore, understanding the occurrence of clouds and their link to the surface solar radiation in the region is important for making plans to manage future solar energy production. In this study, we use the state-of-the-art European Centre for Medium-range Weather Forecasts ReAnalysis (ERA5) dataset to examine the occurrence and persistence of cloudy and clear-sky conditions in the region. Then, we investigate the effects of cloud cover on the quantity and variability of the incoming solar radiation. The cloud shortwave radiation attenuation (CRASW↓) is used to quantify the amount of incoming solar radiation that is lost due to clouds. The results showed that the attenuation of incoming solar radiation is stronger in all months over the southern part of WA near the Guinea Coast. Across the whole region, the maximum attenuation occurs in August, with a mean CRASW↓ of about 55% over southern WA and between 20% and 35% in the Sahelian region. Southern WA is characterized by a higher occurrence of persistent cloudy conditions, while the Sahel region and northern WA are associated with frequent clear-sky conditions. Nonetheless, continuous periods with extremely low surface solar radiation were found to be few over the whole region. The analysis also showed that the surface solar radiation received from November to April only varies marginally from one year to the other. However, there is a higher uncertainty during the core of the monsoon season (June to October) with regard to the quantity of incoming solar radiation. The results obtained show the need for robust management plans to ensure the long-term success of solar energy projects in the region.

scholarly journals Increased UV radiation due to polar ozone chemical depletion and vortex occurrences at southern sub-polar latitudes in the period (1997–2005)

2008 ◽  
Vol 8 (2) ◽  
pp. 6501-6537
Author(s):  
A. F. Pazmino ◽  
S. Godin-Beekmann ◽  
E. A. Luccini ◽  
R. D. Piacentini ◽  
E. J. Quel ◽  
...  
Keyword(s):  
Uv Radiation ◽  
Total Ozone ◽  
Cloud Cover ◽  
Transport Model ◽  
Austral Spring ◽  
Latitude Band ◽  
Ozone Loss ◽  
Clear Sky ◽  
Sky Conditions ◽  
The Impact

Abstract. The variability of total ozone and UV radiation from Total Ozone Mapping Spectrometer (TOMS) measurements is analyzed as a function of polar vortex occurrences over the southern subpolar regions during the 1997–2005 period. The analysis of vortex occurrences showed high interannual variability in the 40° S–60° S latitude band with a longitudinal asymmetry showing the largest frequencies over the 90° W–90° E region. The impact of vortex occurrences on UV radiation and ozone in clear sky conditions was determined from the comparison between the measurements inside the vortex and a climatology obtained from data outside the vortex over the studied period. Clear sky conditions were determined from TOMS reflectivity data. For measurements outside the vortex, clear sky conditions were selected for reflectivity values lower than 7.5%, while for measurements inside the vortex, a relaxed threshold was determined from statistically similar UV values as a function of reflectivity. UV changes and ozone differences from the climatology were analyzed in the 40° S–50° S and 50° S–60° S latitude bands during the spring period (September to November). The largest UV increases and ozone decreases, reaching 200% and 65%, respectively, were found in the 50° S–60° S latitude band in September and October. The heterogeneous ozone loss during vortex occurrences was estimated using a chemical transport model. The largest impact of vortex occurrences was found in October with mean UV increase, total ozone decrease and accumulated ozone loss in the 350 K–650 K range of respectively 47%, 32% and 63%. The region close to South America is the most affected by the Antarctic ozone depletion due to the combined effect of large number of vortex occurrences, lower cloud cover and large ozone decrease. This region would be the most vulnerable in case of cloud cover decrease linked to climate change, due to more frequent occurrence of ozone poor air masses during austral spring.

scholarly journals SALBEC – A Python Library and GUI Application to Calculate the Diurnal Variation of the Soil ALBEdo

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jarosław Jasiewicz ◽  
Jerzy Cierniewski
Keyword(s):  
Diurnal Variation ◽  
Soil Surface ◽  
Observation Time ◽  
Clear Sky ◽  
Optimal Observation ◽  
Input Parameters ◽  
Remote Measurements ◽  
Sky Conditions ◽  
Observation Times

Abstract This study presents the SALBEC – Soil ALBEdo Calculator – a Python library and Graphical User Interface designed to predict the diurnal variation of the clear-sky albedo based on the soil surface properties. Such predictions are becoming more and more necessary with the increasing role of remote measurements. The software uses the following input parameters: the soil spectrum, soil roughness, day of the year (DOY) and sample location. It returns the diurnal albedo variation and, as a unique feature, optimal observation time in the form of tables and graphs as outputs. Models created with the SALBEC were compared with the data acquired under near clear-sky conditions. The comparison shows that the differences between the models and measured data do not exceed the variation of input parameters. The software is directed towards scientists and professionals who require precise estimations of the albedo of soils for different field observation times. Our software is issued as free and open source software (FOSS) and is publicly available at https://github.com/jarekj71/salbec.

scholarly journals How representative are instantaneous evaporative fraction measurements of daytime fluxes?

2013 ◽  
Vol 17 (10) ◽  
pp. 3913-3919 ◽  
Author(s):  
J. Peng ◽  
M. Borsche ◽  
Y. Liu ◽  
A. Loew
Keyword(s):  
Remote Sensing ◽  
Cloud Cover ◽  
The Self ◽  
Global Network ◽  
Promising Technique ◽  
Evaporative Fraction ◽  
Clear Sky ◽  
Available Energy ◽  
The Common ◽  
Sky Conditions

Abstract. Sun-synchronous optical and thermal remote sensing is a promising technique to provide instantaneous ET (evapotranspiration) estimates during satellite overpass. The common approach to extrapolate the instantaneous estimates to values for daily or longer periods relies on the assumption that the EF (evaporative fraction, defined as the ratio of latent heat flux to surface available energy) remains nearly constant during daytime. However, there is still no consensus on the validity of the self-preservation of the EF. We use FLUXNET (a global network of eddy covariance stations) measurements to examine this self-preservation, and the conditions under which it can hold. It is found that the instantaneous EF could represent daytime EF under clear sky conditions, especially between 11:00 and 14:00 LT (local time) for all stations. However, the results show that the EF is more variable during cloudy sky conditions, so that an increase in cloud cover results in an increase in the variability of the EF during daytime.

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