摘要:

AbstractIn view of the implications for the assessment of climatic changes since the mid‐nineteenth century, systematic changes of exposure of thermometers at land stations are reviewed. Particular emphasis is laid on changes of exposure during the late nineteenth and early twentieth century when shelters often differed considerably from the Stevenson screens, and variants thereof, which have been prevalent during the past few decades. It is concluded that little overall bias in land surface air temperature has accumulated since the late nineteenth century: however, the earliest extratropical data may have been biased typically 0.2°C warm in summer and by day, and similarly cold in winter and by night, relative to modern observations. Furthermore, there is likely to have been a warm bias in the tropics in the early twentieth century: this bias, implied by comparisons between Stevenson screens and the tropical sheds then in use, is confirmed by comparisons between coastal land surface air temperatures and nearby marine surface temperatures, and was probably of the order of 0.2

ISSN:0899-8418    

DOI:10.1002/joc.3370140102

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractGeographical distribution across the Southern Hemisphere of 15‐year averages (23‐year averages in the Australian Region) of monthly anticyclonicity and cyclonicity as well as monthly anticyclone and cyclone immobility times, for the months of January, April, July and October for the years 1973–1987 (1965–1987 in the Australian Region) are presented in the form of maps.Comparisons are made with an existing atmospheric climatology of the Southern Hemisphere by the National Climate Centre of the Bureau of Meteorology, Melbourne covering the period 1976–1990 calculated from numerical analyses and with relevant climatologies contained in the World Survey of Climatology. References are made to past works relating to the climatology of the Southern Hemisphere and synoptic features of the climatology are

ISSN:0899-8418    

DOI:10.1002/joc.3370140103

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractMoisture fields derived from the Tiros‐N Operational Vertical Sounder (TOVS) data onboard previous National Oceanic and Atmospheric Administration (NOAA) series of satellites have been used to study monthly moisture fields over the Arabian Sea and the Bay of Bengal for the years 1979–1981. It is observed that monthly averaged moisture fields over the Bay of Bengal are always more than those over the Arabian Sea at a given latitudinal belt. Further, the monthly mean moisture flux divergence has been calculated using monthly mean winds from ship observations over the same areas of the Arabian Sea and the Bay of Bengal. It is found that net moisture flux divergence over the Arabian Sea is consistently higher than that over the Bay of Bengal for the years, 1979, 1980, and 1981, which are deficient, and excess monsoon rainfall years in terms of departure from long‐term climatological rainfall values. Moisture variability over the Arabian Sea and the Bay of Bengal on a monthly scale has also been studied for the months of June, July, and August for the years 1979–1981.A plot of the zonally averaged (at every 2° latitude) differential moisture signal (DMS) by latitude indicates the approximate position of the low‐level westerly jet. The overall differential signal between zonally averaged moisture fields over the Arabian Sea and the Bay of Bengal has also been found to be an indicator of total Indian rainfall excluding orographically influenced regions, although more data is needed to firmly establish the relationship quan

ISSN:0899-8418    

DOI:10.1002/joc.3370140104

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractA network of rain‐gauges has been optimized to reconstruct the spatially representative summer monsoon rainfall series (1871–1984) of India prepared by averaging the normalized rainfall (actual divided by mean) of 306 rain‐gauges. Three approaches have been attempted: (i) random selection, (ii) fitting a multiple linear regression and (iii) selecting objectively a subset of a few gauges, the mean of which shows the highest correlation coefficient (CC) with the all‐India series. By averaging a randomly selected 45 rain‐gauges, an average CC with the all‐India rainfall series ofca.0.94 was achieved, and by averaging 100 gauges the average CC wasca.0.97. By fitting a multiple linear regression between the all‐India series and the normalized rainfall series of 306 gauges, a maximum of 34 independent gauges (parameters) were identified and the estimated rainfall series showed a highest CC of 0.9969 with the full series. In the third approach, a subset of 34 rain‐gauges was identified following an objective criterion; the mean rainfall of this subset showed a CC of 0.9931 with the all‐India series. For routine updating of the all‐India summer monsoon rainfall series, however, 35 rain‐gauges were selected by applying the third approach to 64 randomly chosen India Meteorological Department (IMD) rain‐gauges better known for their timely availability of data. The reconstructed (CC = 0.9866) all‐India summer monsoon rainfall series for the peri

ISSN:0899-8418    

DOI:10.1002/joc.3370140105

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractIn many tropical and sub‐tropical climates the year is divided into well‐defined wet and dry seasons. To maximize agricultural production it is important that crops are planted as early as possible in a wet season, but deciding exactly when the wet season has started may be a problem. A decision can be made on the basis of previous years' data, or we may try to incorporate information from the current season. The latter approach is discussed in the present paper, and shown to be potentially of greater value than relying solely on historical d

ISSN:0899-8418    

DOI:10.1002/joc.3370140106

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractLand suitability mapping requires information about climate, topography, and soils in relation to crop performance. Climatic data are available from recording stations which present point samples and so interpolation is needed to generate estimates for non‐sampled points. The annual temperature cycle must be interpolated differently for different land suitability projects. A common theme, however, is spatial interpolation and here we investigate the application of kriging with external drift to mapping January mean temperatures in Scotland. The spatial structure of the mean temperature is analysed using variograms computed in different directions. From these we see that January temperature is second‐order stationary in the north‐south direction. Hence the variogram exists in that direction and is taken to represent the underlying variogram. This variogram is modelled and used in universal kriging to produce point‐kriged estimates on a 5‐km square grid. These estimates do not adequately show the variation in temperature between stations and so the correlation with elevation was exploited in universal kriging with elevation as external drift. This method gives a kriged estimate for temperature that reproduces the correlation with elevation at the climate

ISSN:0899-8418    

DOI:10.1002/joc.3370140107

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper studies data of ultraviolet (290–385 nm band) horizontal solar irradiation and global horizontal solar irradiation measured at Valencia (Spain) during the period March 1991 to September 1991. Analysis of error estimations and correlation coefficients show that the 10 minute, hourly, and daily values of ultraviolet (UV) and global irradiation are highly correlated. Improved figures and less dependence on location are achieved by defining a clearness index for the UV 290–385 nm band and relating it to the conventional whole‐band clearness index. The novel clearness index obtained from Valencia data is approximately half of the conventional clearness index. Considering solar elevation as an additional parameter, the correlation coefficients increase to values in the 0.94 to 0.96 interval for solar elevations greater than 55°, both for hourly and 10‐minut

ISSN:0899-8418    

DOI:10.1002/joc.3370140108

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractMeasurements of reflected shortwave radiation were made at an Amazonian ranchland site for a period in which the grass was completely burnt and then subsequently regrew. For the 35 days prior to the fire the mean albedo was 0.19. After the fire the albedo was reduced by a factor two and thereafter took about 80 days to recover to its previous value. The influence on the energy balance is described and it is suggested that such seasonal albedo changes during the dry season may need to be described in climate models for the prediction of the seasonal impact of deforestation.

ISSN:0899-8418    

DOI:10.1002/joc.3370140109

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

ISSN:0899-8418    

DOI:10.1002/joc.3370140110

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

ISSN:0899-8418    

DOI:10.1002/joc.3370140111

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY