METEOROLOGY AND ATMOSPHERIC CHEMISTRY 



81 



TABLE 2 



Tropical Storms and Disturbances 

 Affecting Enewetak. 1959-1979 



'CD, Climatological Data. National Summary, a NOAA publi- 

 cation from the Environmental Data Service, National Climatic 

 Center, Asheville, N. C. 



we emphasize the most important aspects of the upper 

 level wind structure, proceeding upward from the surface 

 and covering each 3-month period and the east-west and 

 north-south components of the wind. The discussion Is 

 based on radiosonde data compiled and analyzed by 

 Newell et al. (1972) and, to a lesser extent, on the illus- 

 tration (their Fig. 4) of Blumenstock and Rex (1960). 



The near-surface trade winds are strongest in the dry 

 season, and they extend at least some 5 km or so into the 

 atmosphere all the year around. The east-west component 

 of the wind is negative, i.e., the wind is from the east, up 

 to 500 mbar (~5.6 km) in March to May, and up to about 

 300 mbar (~9.5 km) in September to November. The 

 westerly winds which overlie this layer are absent, in the 

 long-term average, in December to February. The 

 north-south component is near zero up to above 700 

 mbar (^-3.0 km), with the average value being negative 

 (i.e., from the north) in December to May and just positive 

 (from the south) in June to November. This is consistent 

 with surface wind roses presented above. 



In the layer between 500 mbar (March to May) or 300 

 mbar (September to November) and —150 mbar (14.5 

 km), there are westerly winds on the average in March to 

 November and weak easterlies in the remainder of the 

 year. The strongest westerly winds are in the months of 



March to May, centered in height around 200 mbar ' 

 (~12.2 km). These are part of the subtropical jet which is 

 strongest at higher latitudes and earlier in the year. The 

 north-south component in this layer is, again, quite weak 

 on the average. Due to the passage of large-scale weather 

 systems, these mean winds are not representative of the 

 observed circulation on a given day. Also, the weak 

 north-south component is particularly sensitive to such 

 variability, and this is all the more unfortunate as knowl- 

 edge of this component is fundamental to understanding 

 the large-scale transport, e.g., of heat and of tracers. While 

 there are enough upper-air stations in the western tropical 

 Pacific to make certain our knowledge of this component, 

 there are vast areas in the mid-latitude Pacific where this 

 is not so. 



There is a quasi-biennial oscillation in the tropical 

 stratosphere, i.e., the monthly averaged winds shift from 

 west to east with a period of approximately 26 months in 

 a band ~-25° latitude wide (full width at half maximum 

 amplitude) around the equator; this extends from very high 

 in the stratosphere (>35 km) to at least 100 mbar (—16 

 km). This is now understood to be an interaction phenome- 

 non illustrating the coupling between the troposphere and 

 tropical stratosphere. Its discovery in the early 1960s 

 illustrates how recently we have begun to learn about this 

 area of the atmosphere. The "Krakatoa Easterlies," so 

 named because they were first observed transporting 

 debris from the spectacular 1883 volcanic eruption, are 

 not as constant as had been thought. 



Sources of Additional Data 



Several of the important sources of additional meteoro- 

 logical data for Enewetak have been referenced in the 

 previous sections. Here we summarize briefly the 

 availability of various types of data and indicate the best 

 sources for discussions on sp>ecialized subjects. 



The archive of data used to prepare the figures in this 

 chapter is the Revised Uniform Summan; of Surface 

 Weather Observations for Eniwetok Marshall Islands. In 

 addition to the wind, cloudiness, temperature, and humid- 

 ity data presented here, it contains extensive information 

 imfKDrtant primarily for aircraft operations, e.g., ceiling and 

 visibility data. The document can be obtained for copying 

 costs from the National Climatic Center, AsheviUe, North 

 Carolina. 



A reliable and useful atlas of tropical wind and tem- 

 perature charts is included in Newell et al. (1972) along 

 with sophisticated discussions of the global tropical circula- 

 tion in dynamical terms. The Pacific island rainfall data and 

 analysis of Taylor (1973) are an excellent resource. There 

 is a collection of marine meteorological observations (Sum- 

 mary of Si/noptic Meteorological Observations, Volume 3, 

 which includes "Area 10 — Eniwetok") available from the 

 National Technical Information Service as AD-725 138, 

 but the data are very sparse. 



Solar radiation data are available for certain periods 

 beginning in May 1977 from the Department of Meteorol- 



