Search Results

You are looking at 1 - 8 of 8 items for

  • Author or Editor: W. P. Elliott x
  • Refine by Access: All Content x
Clear All Modify Search
W. P. Elliott and R. K. Reed

Abstract

Climatological estimates of mean annual precipitation over the world ocean are presented and discussed. We obtained a value for mean annual oceanic precipitation (between 65°N and 60°S) of 93 cm, which is smaller than some other estimates. These results are supported by a recent analysis of tropical rainfall based on satellite techniques. Aspects of the need for and utility of climatological information are discussed.

Full access
W. P. Elliott and J. K. Angell

Abstract

Relationships are examined among records of atmospheric pressure at Darwin, Tahiti and Santiago and indices of the Southern Oscillation (SO) formed from these pressures for the period 1883–1984, and the sea surface temperature in the eastern equatorial Pacific (SST*) as well as Indian summer-monsoon rainfall and continental and marine hemispheric temperatures. In general, the correlations of pressures and SO indices with SST* have been greatest since World War II, but were also relatively high prior to World War I. An exception is Tahiti pressure which is poorly correlated with SST* until about 1940. The correlations have tended to be higher when moderate or strong El Niño were most frequent. The question is discussed whether the decrease in correlations among the various datasets that is apparent in the middle third of the time period in question, roughly from 1920 to 1950, reflects a real change in atmospheric processes or is due to data problems. It is suggested that prior to World War I the pressure difference between the far eastern Pacific and Darwin was more representative of the Southern Oscillation, while between the two World Wars the Southern Oscillation was not quite so prominent, and since World War II the pressure difference between the central Pacific and Darwin has best reflected the Southern Oscillation.

Full access
R. K. Reed and W. P. Elliott

Abstract

The problems of using raingages on ships are discussed, and methods of estimating rainfall from weather reports at sea are reviewed, with emphasis on discussion of efforts to verify the assessments derived by Tucker (1961). A raingage was used on cruises of the NOAA ship Oceanographer in the eastern Pacific during 1975 and 1976, and rainfall was estimated from weather reports using Tucker's assessments. In extratropical latitudes (mainly 40–60°N), a catch of 35 cm was obtained; estimates from the weather reports gave a value of 31 cm. Thus Tucker's assessments are essentially in agreement with catches from a small gage in this region. In the tropics, however, the agreement was not good. Almost three times as much rain was caught as was estimated; hence Tucker's coefficients will need to be reevaluated for this area.

Full access
W. P. Elliott and J. K. Angell

Abstract

Correlations between the June-September Indian monsoon rainfall and Santiago minus Darwin pressure, Tahiti minus Darwin pressure, and Wright's Southern Oscillation index, as well as the individual station pressure deviations themselves, show that the monsoon rainfall anticipates the Southern Oscillation Indices and the individual pressure deviations with the exception of the pressure at Santiago. Monsoon rainfall is also negatively correlated with sea surface temperatures in the eastern equatorial Pacific one to two seasons later. The correlations suggest that above average monsoon rainfall is associated with below average Southern Hemisphere temperatures two to three seasons later, whereas above average Northern Hemisphere winter temperatures—particularly continental temperatures—anticipate above average rainfall. The correlations with hemispheric temperatures are significant only since about 1947, however. A strong negative correlation (−0.64) between the seasonal change in Darwin's pressure deviation from December-February to March-May prior to the monsoon, and monsoon rainfall is found in the period 1947–84, but only weakly in the period before 1947.

Full access
J. K. Angell, W. P. Elliott, and M. E. Smith

Abstract

As a preliminary step in evaluating the feasibility of determining meaningful tropospheric humidity trends on a hemispheric or global scale using a sparse radiosonde network, radiosonde data at the earth's surface and at 850, 700 and 500 mb mandatory pressure surfaces, and significant levels between, have been examined for the interval 1958-80 at Brownsville, Texas and Great Falls, Montana. Adjustments had to be applied to the data prior to 1966 because at this earlier time dry observations (“motorboating”) were not reported. In general, the relative humidity at these two stations decreased or remained constant between 1958 and about 1970, and increased between about 1970 and 1980, but over the full record, it decreased at Brownsville and increased at Great Falls. Mixing ratio and precipitable water decreased during the earlier interval and increased during the later interval, similar to the variation in Northern Hemisphere temperature, although this may well be coincidence. On the seasonal and yearly time scale the relative humidity has tended to vary inversely with station temperature, and mixing ratio directly with this temperature, but these two stations do not define the relation among long-term trends in temperature, relative humidity and mixing ratio. It is concluded that to establish hemispheric or global trends in humidity will require use of a fairly extensive radiosonde network, as well as knowledge of instrumental changes and changes in measurement technique at individual stations within this network.

Full access
G. F. Rossknecht, W. P. Elliott, and F. L. Ramsey

Abstract

Observations of the larger airborne sea-salt particles collected on Millipore filters at varying distances from the shore show that over the ocean and at distances greater than 8 km inland the relative frequency distribution of particle diameters was well fitted by an exponential random variable but not well fitted within 8 km of the shore. The inland distribution at near ground level follows the model of Tanaka quite well when allowance for the effect of relative humility on particle size is considered.

Full access
W. P. Elliott, D. J. Gaffen, J. K. Angell, and J. D. W. Kahl

Abstract

Mean layer virtual temperature estimates, based on geopotential height measurements, form the basis for one approach being used to monitor changes in upper-air temperature. However, virtual temperature is a function of atmospheric moisture content as well as temperature. This paper investigates the impact of real or apparent changes in atmospheric moisture on changes in mean layer virtual temperature. Real changes in mean layer specific humidity of up to 50% would cause changes in mean layer virtual temperature of less than 1°C, except in the tropical boundary layer, where the high moisture content would lead to larger virtual temperature changes. The effect of humidity changes is negligible in polar regions and most pronounced in the tropics, which could influence the interpretation of the latitudinal gradient of virtual temperature trend estimates. Improvements in radiosonde humidity sensors since 1958 have led to an apparent decrease in atmospheric humidity. On global average, for the 850–300-mb layer, such changes are estimated to contribute to an apparent cooling of between 0.05° and 0.1°C, or about 10% to 20% of the observed warming trend since 1958.

Full access
Ryan J. Longman, Courtney L. Peterson, Madeline Baroli, Abby G. Frazier, Zachary Cook, Elliott W. Parsons, Maude Dinan, Katie L. Kamelamela, Caitriana Steele, Reanna Burnett, Chris Swanston, and Christian P. Giardina
Full access