Ground-based measurements of local cloud cover

Silva, Abel Antônio; Echer, Mariza Pereira de Souza

doi:10.1007/s00703-013-0245-9

Cited by 26 publications

(30 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As shown by Silva et al . , cloud cover in Belo Horizonte generally increases from morning to afternoon, especially in fall and summer.…”

Section: Resultsmentioning

confidence: 99%

“…A personal computer routine provided by the manufacturer controls the equipment and processes the captured images, determining the percentage of the sky covered by clouds (cloud cover). Uncertainties in the measurements by the TSI are higher than 10%, except for overcast or cloudless skies to which uncertainties can be lower .…”

Section: Methodsmentioning

confidence: 92%

“…There are many others, even out of noontime as it can be deduced comparing them with the thick black line referring to the EDR on JAN022010. They all are potential figures to be identified as radiation enhancement events, occurring mainly in the afternoons when cloud cover tends to be larger in the site . Thus, summertime and noon are not the only potential times for the occurrence of radiation enhancement events.…”

Section: The Edr Measurementsmentioning

confidence: 99%

See 2 more Smart Citations

Daily Maximum Erythemal Dose Rates in the Tropics

Silva¹,

Yamamoto

Correa

2018

Photochem & Photobiology

View full text Add to dashboard Cite

The maximum erythemal dose rate (EDRmax) at the Earth's surface tends to occur at local noon. However, clouds can make the timing of EDRmax significantly away from local noon. In fact, EDRmax and its time of occurrence depend mainly on the solar zenith angle at noon (SZAn), site's altitude, the total ozone column (TOC), cloud cover, cloud genera and aerosols. This work depicts the daily incidence of EDRmax for Belo Horizonte (19.92°S, 43.94°W, 858 m a.s.l.) in the Southern Hemisphere tropics for a period of five years (2005–2010). Daily values of EDRmax ranged from 0.063 W m−2 (1σ > 6.9%, Moderate UV‐Index of 3, winter) to 0.486 W m−2 (Extreme UVI of 19, summer). Indicative values of EDRmax for cloudless days were 0.336 W m−2 (summer, TOC = 258 Dobson Units), 0.311 W m−2 (fall, 260 DU), 0.253 W m−2 (spring, 274 DU) and 0.143 W m−2 (winter, 246 DU). Radiation enhancement events by clouds made EDRmax up to 45% higher than the reference EDRmax for cloudless summer skies at a time resolution of a few minutes. The main cloud genera to be associated with such events are Cumulus, Altocumulus, Altostratus and Stratocumulus. The EDR can also be significantly affected by aerosols, which attenuated on average 0.031 W m−2 (22%) of the erythemal UV in a case study at the site.

show abstract

“…As shown by Silva et al . , cloud cover in Belo Horizonte generally increases from morning to afternoon, especially in fall and summer.…”

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 92%

Section: The Edr Measurementsmentioning

confidence: 99%

See 1 more Smart Citation

Daily Maximum Erythemal Dose Rates in the Tropics

Silva¹,

Yamamoto

Correa

2018

Photochem & Photobiology

View full text Add to dashboard Cite

show abstract

“…Silva and Souza‐Echer () have developed a routine to obtain the local cloud cover (LCC) based on the analysis of digital images from a ground‐based automatic imager. LCC is defined as the running average of values of cloud cover within a given field of view (around 100°) from images taken within a time interval T shifted forwards in time steps of Δ T .…”

Section: Introductionmentioning

confidence: 99%

“…Aiming at contributing to the replacement of CC HO by LCC, the present study (1) compares almost 3 years of LCC data from a Total Sky Imager set up in a tropical, urban site with data of CC HO and (2) validates the routine proposed by Silva and Souza‐Echer () for the determination of LCC. Section explains the site and instruments, which is followed by Section referring to the analysis of the data.…”

Section: Introductionmentioning

confidence: 99%

Ground‐based observations of clouds through both an automatic imager and human observation

Silva¹,

Souza-Echer

2015

Meteorological Applications

Self Cite

View full text Add to dashboard Cite

ABSTRACT:The routine to determine the local cloud cover (LCC) drawn from sky images obtained using a ground-based automatic imager is validated. Almost 3 years of daily data of LCC and cloud cover measurements by ground-based human observation (CC HO ) were compared for two Brazilian stations set 6 km apart. The linear fitting between daily values showed a co-efficient of determination (r 2 ) and a percent scattering of points (SD%) of ≈ 0.77 and ≈ 19.4% respectively. These results are evidence for the significant similarity between the two sets of data. On the other hand, the level of difference found can be explained by the fact that (1) the data refer to independent micro-scale observations of the sky from stations set a few kilometres apart and (2) the data were drawn from interpretations of cloud cover by an automatic imager and a human observer. The monthly average values of LCC and CC HO showed better linear fitting parameters r 2 = 0.95 and SD% = 6.3%. Average differences of ≈ −10% from LCC to CC HO were found. These average differences may reflect a systematic bias between the two processes of measuring cloud cover.

show abstract

Clouds Affecting Total Ozone Column Measurements

Silva¹

2022

Pure Appl. Geophys.

View full text Add to dashboard Cite

Ground-based measurements of local cloud cover

Cited by 26 publications

References 39 publications

Daily Maximum Erythemal Dose Rates in the Tropics

Daily Maximum Erythemal Dose Rates in the Tropics

Ground‐based observations of clouds through both an automatic imager and human observation

Clouds Affecting Total Ozone Column Measurements

Contact Info

Product

Resources

About