Distribution of global and net radiation over the Indian Ocean and its environments

Mani, A.; Chacko, O.; Krishnamurthy, V.; Desikan, V.

doi:10.1007/bf02319113

Cited by 16 publications

(5 citation statements)

References 8 publications

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“…However, although they made no mention of the fact, several workers have presented measurements which indicated or implied that a cross-over did exist. Mani et al [15], among many others, indicated that for direct radiation the albedo of water varied from a few percent at noon to near 100 per cent with the sun at the horizon, while for diffuse radiation the albedo remained fairly constant all day at about 10 per cent. This suggests that a seasonal cross-over in daily albedos, similar to that observed by the authors for wheat and barley, might be present for water surfaces.…”

Section: Seasonal Differences In Clear Andmentioning

confidence: 99%

Variations in the albedo of wheat and barley crops

Piggin

Schwerdtfeger

1973

Arch. Met. Geoph. Biokl. B.

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The albedo of wheat and barley crops was measured during the course of two successive growing seasons, one of which was exceedingly wet (1966) and the other abnormally dry (1967) at Derrimut, Victoria, Australia.Daily albedo values ranged from 0.13 to 0.25 for wheat and from 0.14 to 0.36 for barley. The seasonal trends are explained in terms of changes in crop development and soil moisture. Albedo variation with solar elevation is also discussed. This leads to a consideration of the differences in albedo under clear and overcast skies, and it is shown that overcast days have an effective solar elevation of about 450 . Zusammenfassung Variationen der Albedo yon Weizen-und GerstenfeldernDie Albedo yon Weizen-und Gerstenfeldern wurde in Derrimut, Victoria, Australien, in zwei aufeinanderfolgenden Vegetationszeiten gemessen. Eine dieser Vegetationszeiten (1966) war auf~erordentlich nat~, die andere (1967) abnormal trocken.Die t~glichen Albedowerte reichten von 0.13 bis 0.25 fiir Weizen und von 0.14 bis 0.36 ffir Gerste. Der Jahresgang der Albedo wird aus den Ver~inderungen in der Entwicklung der Pflanzen und im Bodenfeuchtegehalt erkl~irt. Die Xnderung der Albedo in Abh~ingigkeit vom H6henwinkel der Sonne wird ebenfalls diskutiert. Es werden auch die Unterschiede zwischen der Albedo bei Harem und bei bedecktem Himmel untersucht. Es zeigt sich, daf~ die Albedo an bedeckten Tagen der Albedo bei einem effektiven Sonnenwinkel von 45 o gleichkommt. Arch. Met. Geoph. Biokl. B. Bd. 21, H. 4 24 366 I. Piggin et al.

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Section: Seasonal Differences In Clear Andmentioning

confidence: 99%

Variations in the albedo of wheat and barley crops

Piggin

Schwerdtfeger

1973

Arch. Met. Geoph. Biokl. B.

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“…Generally, the value of k varies between 0.55 in high latitudes and 0.33 in low latitudes (Mani et al 1967). This formula is very similar to the Anstrom-Prescott (A-P) formula relating sunshine duration (S) with global solar radiation (H) as:…”

Section: Estimation Of Sunshine Duration From Cloud Amountmentioning

confidence: 99%

Estimation of solar radiation from cloud cover data of Bangladesh

Sarkar

2016

Renewables

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In this study, an analysis of the monthly mean values of the fraction of the sky covered by clouds (C) of all types and the duration of bright sunshine hours (S) and global solar radiation on the horizontal surface (H) was carried out to establish relationship for solar radiation estimation for Bangladesh. The relationship between C and (1 − S/S 0 ), where S 0 is the maximum possible hours of sunshine, was found to be nonlinear. The relationship between C and (1 − H/H 0 ), where H 0 is the extraterrestrial solar radiation, was also found to be nonlinear. Few quadratic regression equations were derived for different regions of Bangladesh. The data were separated in Zone 1 (below the tropic of cancer, i.e., ≤23.5°N) and Zone 2 (above the tropic of cancer, i.e., ≥23.5°N). All the developed models were checked statistically. It was found that it is always better to estimate solar radiation from sunshine duration as it gives the best estimation and accuracy, but if there is no sunshine duration data available for a site, then solar radiation can be estimated directly from cloud cover data. Estimating sunshine duration first from cloud data to estimate solar radiation introduces more error as it has to go through the modeling stage twice. In case of the need of sunshine duration data only, the estimation from cloud cover is quite helpful. It was also found from the study that for small country like Bangladesh separating data according to latitude has insignificant effect.

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“…The desirability of establishing this instrumentally is obvious. The distribution of global and net radiation over the Indian Ocean has been discussed by Mani, Chacko, Krishnamurthy & Desikan (1967): the average cloud cover in the tropics has been evaluated by Sadler (1968) from satellite observations. An atlas of Indian Ocean clouds has also been recently published (Bunker & Chaffee, 1968).…”

Section: Sunshine and Cloudmentioning

confidence: 99%

The climate of Aldabra Atoll

Farrow

1971

Phil. Trans. R. Soc. Lond. B

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Meteorological observations made by members of the expedition since August 1967 are the first to appear from Aldabra which cover a sufficient time span to merit analysis. Data for the period November 1967 to October 1968 are compared with marine derived parameters available from climatological atlases. Aldabra experiences a 5- or 6-month wet season in most years and its climate may be classified as V 2 /V 3 . During midsummer 1967/8 a marked positive pressure anomaly was observed: this coincided with a 3-month failure of the monsoon. For 7 months of the year the southeast trade winds blow, with a constancy of more than 90%. Summer maximum temperatures average 32 °C (90 °F) at the Settlement synoptic station, but this station is atypical for much of the atoll where maximum temperatures are about 3 °C lower. Winter minimum temperatures average 22 °C (72 °F). The annual pattern of temperature fluctuation for Picard compares most closely with the Comoro Islands. Summer maxima are identical with Diégo Suarez values; winter minima with the Seychelles. The highest and lowest shade temperatures recorded in the year were 36.3 °C (97.4 °F) and 19.5 °C (67.1 °F). The diurnal temperature range varies little throughout the year, averaging 6.5 °C, though extremes of 11 °C are occasionally recorded. Lagoon water temperatures are tidally controlled. At springs mean values may exceed the local air shade temperature by more than 3 °C. This could lead to very high temperatures in the lagoon in summer, but the exact magnitude must be ascertained from future observations. Sunshine measurements have not yet been made on the atoll. Calculations of probable monthly sunshine totals based on cloud observations show that October is clearly the sunniest month with a computed average of 8.6 h/day; January and April are least sunny, with 5.4 h/day. The annual total calculated for Aldabra (2400 h average; 2100 h 1967/8) is considerably at variance with regional values shown on world maps of climatology (indicating 1800 h). This can be resolved only by obtaining instrumental records from the island. The mean annual rainfall of 670 mm (26.5 in) derived from 7 years records is strikingly lower than atlas predictions. It places Aldabra in the most arid sector of the western Indian Ocean. From 1950 to 1960 a sequence of pairs of wet and dry years can be discerned, with extreme yearly totals of 1200 and 350 mm (47 and 14 in). The monsoon may occasionally be as short as 2 months, and droughts of 3 months or more are recorded during the trades. In 1967/8 summer rainfall showed a continental-type bimodal distribution, though on average it shows a broad plateau tending towards a late summer maximum (cf. Lindi, Tanzania). In 1967/8, 42% of the yearly rainfall fell on 5 days as violent showers with more than 40 mm (1.6 in). Local climatic effects were investigated from an auxiliary meteorological station set up at Middle Camp, Passe Houareau. In October 1968 the mean trade-wind speed exceeded 9 m s -1 (19 knots) from 08h00 to 13h00; which indicates a tendency to underestimate its strength considerably when observing at Settlement. Appreciable east—west variation in rainfall totals occurred. It is this essential to evaluate any precipitation gradient which may exist during the monsoon, for rainfall totals from Picard may bear little relation to the southeastern region. Analysis of autographic charts indicates that relative humidity varies from stable night values of around 93% to minima of 70% during early afternoon. In late September/October, values as low as 50% have been recorded. A strongly semi-diurnal distribution of rainfall is shown by Dines tilting syphon raingauge charts, which correlates with the S 2 atmospheric tide. During the monsoon frequency of rain shows a pre-dawn maximum: during the trades a pre-dusk maximum, which is not typical of a truly oceanic atoll.

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Distribution of global and net radiation over the Indian Ocean and its environments

Cited by 16 publications

References 8 publications

Variations in the albedo of wheat and barley crops

Variations in the albedo of wheat and barley crops

Estimation of solar radiation from cloud cover data of Bangladesh

The climate of Aldabra Atoll

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