SFERICS 
storms, lightning, and cumulonimbus from the rela- 
tively dense United States weather-reporting network 
east of the 95th meridian. For the six-month period, 
May to October, 1945, 87 per cent of 135 four-station 
fixes were within 100 miles of a thunderstorm, lightning, 
or cumulonimbus report within one hour of the sferics 
observation, and 68 per cent of 19,130 three-station 
fixes were similarly verified. On the other hand, of 
11,006 reports of thunderstorms or hghtning, 57 per 
cent were attended by fixes within 100 miles, and 80 per 
cent, within 200 miles. The diurnal variation averaged 
between ten and fifteen per cent on either side of the 
figures given, with poorest performance at 0600 and 
0900 GMT, best at 2100 and 0000 GMT. A survey made 
in 1945 [388] of 98 U. S. Air Force weather stations 
located within the area of coverage of this network, 
selected only for having forecasting problems in the 
Gulf of Mexico, Caribbean, or western Atlantic, re- 
vealed that 42 per cent considered sferics reports over 
the oceans in middle latitudes to be ‘“‘extremely useful,” 
and 98 per cent considered them either ‘extremely use- 
ful” or ‘“useful.”? Almost identical percentages resulted 
as regards sferics reports over oceans in the tropics. 
The average length of experience with sferics was nine 
months. In a series of airplane flights over the ocean 
bordering on the network, 81 per cent of the sferics 
reports near the flight path were attended by signifi- 
cant weather within 100 miles. 
Interesting remarks on the use of sferics in weather 
forecasting in Switzerland, including a discussion of 
the implications of both active and quiet regions, may 
be found in [16]. The relation of sferics to the Indian 
monsoon may be found in [35, 36]. For examples of 
recent North Atlantic weather and corresponding sferics 
fixes, see [25]. Studies relating to the utility of sferics 
as regards hurricanes have thus far tended to be in- 
conclusive or negative [30], although further work 
appears justified in view of reports from the western 
Pacific during World War II of their use in following 
the progress of easterly waves. Recently sferics have 
been studied in tornado investigations, with emphasis 
on analysis of wave forms. 
More studies are needed relating broad meteorological 
patterns to the distribution of thunderstorms and other 
intense electrical activity occurring in regions of rapid 
charge separation. The physical nature of the hghtning 
flash, its visible and photographic forms, the resulting 
field changes, the propagation of attending electro- 
magnetic waves—these researches have been and are 
still emphasized. Consequently, sferics research has 
tended to appear in nonmeteorological publications. 
Doubtless room for further application of modern direc- 
tion-finding techniques to sferics exists, if only because 
present systems are essentially those first employed 
two or three decades ago. However, if the field of sferics 
is to find important use in meteorology, studies of re- 
gional application of sferics observations to characteris- 
tic weather patterns must be undertaken; reference is 
made to the areal distribution of thunderstorms at- 
tending the large-scale flow patterns. Such patterns may 
include cyclogenesis, especially in regions off the east 
1299 
coasts of the continents. Presumably, departures from 
the normal in the disposition of sferics may yet be found 
in the neighborhood of developing tropical storms. As to 
the utility of sferics over land areas occupied by a dense 
meteorological observational network, the burden of 
proof rests with sferics, although the mexpensiveness of 
simple sferics receivers compared with radar sometimes 
recommends them for warning of the approach of local 
storms, especially during daylight hours when the detec- 
tion of thunder is limited to a distance of the order of ten 
miles. Because of an essential requirement for a thun- 
derstorm, that is, sufficient available moisture, sferics 
methods find negligible application im some areas, and 
only seasonal use in some others. The development of 
a synoptic climatology of sferics distribution over the 
oceans would contribute toward maximum utility of 
sferics methods. Great benefit should also be derived 
from the analysis of wave forms that imdicates the 
relative frequency of cloud-to-cloud, cloud-to-air, and 
cloud-to-ground discharges. 
Sferics study promises to refine our knowledge of the 
distribution of thunderstorms over the oceans. Brooks’ 
classical work [6] was necessarily based largely upon 
ships’ reports for the ocean, and it is expected that 
conclusions based upon this essentially small sample 
may be improved. A minor disadvantage in the use 
of sferics for this purpose lies in the loss in accuracy as 
one proceeds away from a central area or point, but 
this objection is not final as regards the refinement of 
our climatological knowledge over the oceans. The 
development of a climatology of radio static appears 
desirable [37]. It should become possible to estimate 
reasonably well for any given place on the globe the 
monthly, seasonal, and annual noise level, and its 
diurnal variation. Meteorologists may well assist in 
the interpretation of noise-level records made over the 
world. Specific results will depend upon increased ac- 
quaintance with the synoptic climatology of thunder- 
storm occurrence over the oceans. 
Present sferics methods are time-consuming when it 
is desired to locate fixes accurately and to obtain a 
large sample. Photography has mostly found applica- 
tion for research purposes. Rapid techniques for han- 
dling the considerable volume of information obtained 
even with a simple direction finder will increase the util- 
ity of sferics in applications to forecasting. With small 
sample methods, the reliability of a sferics observation 
as an indication of electrical activity is greater than 
that of a negative observation as an indication of quiet 
conditions. Electronic methods are apparently available 
for the presentation of the areal distribution of electrical 
discharges continuously on oscilloscope screens [27]. 
The electronic determination of frequency distribution 
of azimuths of discharges above predetermined levels 
of intensity also seems feasible. It should be possible 
to present the results of a complete sferies observation 
made at map time well before the map is plotted and 
analyzed. Finally, it would be helpful to investigate the 
proper length of observational sample necessary in order 
to obtain a reasonably complete picture of the sferics 
activity occurring at a given time. 
