MARCH 1940 MONTHLY WEATHER REVIEW
PERIOD PRECEDINQ HEADINQ TABLE 2.-Crop yields and weather data 1
4 6
--
70.9 74 61.1 66 74.65 66.7 68.77 68.05 60.55 69.05 68.05 64.08 64.7 68.3 66.8 68. 4 65.92 66.8 68.8 67.6 67.8 68.2 70.9 68.78 62.50
Evaporation: 45 to 50 days preceding heading ____________________ -. 374 40 to 45 days preceding heading .................... -. 449 35 to 45 days preceding heading .................... -. 505 20 to 30 days preceding heading _____________-_______ -. 446 3.06 1.21 .84 2.69 1.63 5.70 5.75 1.24 5.12 1.91 1.70 3.81 4.80 2. 28 3.31 1. 91
3.60 3.43 2.14 2. 29 2.92 3.23 1.70 1.61 3.98
-- - - Temperature: Average temperature 20 to 30 days preceding heading- -. 316
Maximum temperature 15 to 25 days preceding head-
~
Picld
11.1 15.8 21.4 17.1 5.4 42.7 34.2 14.6 26.1 16.4 20.6 24.4
--
i n g _______-_--------_--_----------------------- -.436
25 to 30 days preceding heading ____________________ +. 368 5 to 25 days preceding heading _____________________ +. 117
Humidity (for 18 years only) :
1
9 4 4 9 7 16 15 3 13 6 7 11
Data 2 3
24 27 44 24 30 12 24 34 17 34 21 25 11 37 IS 55 19 20 33 14 27 20 17 21 27
--
16.7 17.9 17.0 16.8 18.3 11.1 17.2 20.5 12.2 15.1 13.8 12.7 10.8 18.0 14.7 14.5 14.1 9.4 16.1 12.1 15.0 11.7
13.8 14.2 13.5
1.005 1.286 1.382 1.375 1.m
,679 .794
1.049 ,467 1.226 .977 ,955
.712
1.319 .701 1.435 1.174 ,535 .977 .732 .941 ,321 1.232 1.194 1.279
Rainfall planting to ripening +40 percent of fallow year-..- +. 247 Rainfall planting to heading +40 percent of fallow year--_ +. 274 Rainfall fallow year ___________________________________ +. 327 Rainfall of calendar year- _____________ - _______________ +. 113 Rainfall plantingto ripening ___________________________ +. 457 Number Of days from emergence to heading- - - - -- - - - - - -
~ -* 133
September and October rain- - ___--___- -- ---- - - -- - - ---_ -. 317
1 F i w e s in column 1 shorn number of davs with .IO inch of ralnfall from April 1st to Heading 2 Severity of drought (number df days in longest ralnless period) etc. Sea arabic nkubcrs in Figure 1, for other titles.
FLOODS IN THE SACRAMENTO VALLEY, FEBRUARY 27-MARCH 6, 1940
By E. H. FLETCHER
[Weather Bureau, Sacramento, Calif., May 18401
6 7 8
---
0.16 69.5 T 73.4 0 68.8 .55 70.8 .02 84.3 .34 71 .18 66.8
0 .45 63.6 56
0 68.8 .I 4 70.4 .53 70.6 .84 60.2 0 77 .28 64 0 80.5 0 74.6 1.68 59.4 .01 70 4 1.03 65.2 .29 68.4 .ll 56.2 0 79.2
.50 73 .08 68.6
The flood that occurred in the Sacramento Valley late in February may well be classified as one of first magnitude, exceeding that of December 1937, and in some respects sur- passing any flood smce systematic records have been kept by the Weather Bureau. From Kennett, Calif., to the mouth of the Feather River, new all-time high water
marks were established generally. The rainfall season of 193940 did not get under way until near the end of December. However, during Janu-
ary and most of February frequent rains over the Sacra- mento River system kept the streams and bypasses at high,
1921 ._....._._____
AFTER HEADING 1922 ._..__.____.._
1923 ._________._._
::;:::::::::::::: 1926 ._._..________
19?7 ..__.__...___.
lYW-- ...._.......
Average temperature for 10 days after heading----------- -. 250
GENERAL
.~
but not flood levels. Near the beginninn of the year the California-Hawaiian
35.4 12 13.6 5 21.8 11
!j!:i 3Q.4 9 15.7 7 25.6 9
high-pressure system had receded far southward of its normal winter po?itionz and was replaced by storm areas of much greater mtenslty than ordinanly appear in that
region. Consequently, a succession of slow-moving cy- clonic disturbances, advanced northeastward off the Pacific coast, mth intermittent warm-type occluded cyc.lonic systems moving inland over northern California, and causing precipitation in the form of rain at much higher elevations in the mountains than is usual during the midwinter months. This situation accounts for the marked deficiency in snowfall that prevailed until late in
the season. On February 24-25, the last one of this series of north- eastward-movmg storms apparently cauged the importa- tion of a large volume of semi-tropical air near the Cali- fornia coast, whence it was carried inland on February 27-28 by another and more intense storm of the Aleutian type with exce tional frontal activity, producing torrential
of the 29th, a cold front had advanced inland over the Pacific northwest, bringing lower temperature and snow to the mountains, with clearing weather following. Thus
ended a cycle of storms that wns directly responsible for the disastrous flood of February. The excessive rainfall was mostly confined to the 5-day period, February 25-29, with the most intensive fall occur- ring on the 27th-28th. However, the antecedent rain-
fall extending over a period of about 2 months, was ahighly
ramfall in the 8 acramento drainage area. On the morning
important contributing factor to the flood-producing
run-off. It was apparent as early as Monday morning, February 26, that a period of high wnter was inevitable, and the river bulletin that morning contained the following general forecast: A general rise is developing in all streams, and mth continued heavy rains in prospect, high stages will result in the Sacramento River and probably the lower San Joaquin, during the next 2 or 3 days. During thht day a close check was maintained on the situation by means of hourly weather reports that were
received by teletype. At, .5 p. m., w-hen the river stage at Red Bluff (flood stage 23 feet) was only about 13 feet, flood warnings were issued for tlint vicinity and Tehama County. The upper courses of all streitms in the Sacramento
drainage area began to rise rapidly during that night, and on the morning of the 27th) flood warnings were repeated, stressing that the serious conditions that were rapidly developing would be intensified during the next 24 hours by expected additional heavy rainfall, and that extremely critical flood conditions, equaling or exceeding those of December 1937, would prevail in the Sacramento Valley during the next 3 days. Warnings were also issued to the effect that mild flood conditions would be experienced in the lower reaches of the eastern tributaries of the lower San Joaquin River, namely, the Consmes, Mokelumne, Calaveras and Stanislaus Rivers. From the influence of the American River, the Sacra- mento River at Sacramento rose steadily on the 27th) and at 10:30 p. m., when the stage was 28.5 feet, the 48 gates of the Sacramento Weir, 3 miles upstream from the City, were opened, permitting the excess water to escape west- ward into the wide expanse of the Yo10 Bypass, which conducts the water southward to the vicinity of Rio Vidta, where it reenters the broad river channel. After the weir gates were opened the river a t Sacra- mento fell during the next 5 hours to 26.5 feet andremained
practically stationary for several days. The city of Sac- ramento was at no time endangered.
71
-
9
0.33
.51 .I 7 .72 .46 226 1.04
.oo 1.73 .06
.91 .55 1.72
.oo .94 1.84 1.39 1.65 .26 1.52 1.51 .30
.50
1.58 .I1
-
72 MONTHLY WEATHER REVIEW MARCH 1940
Stations
Swamento Riuer
Minerd.. __._______
Mount Shasta ______ McCloud ___________ Hobergs ____________ K k C P. H _________ Dunsmuir ._________
Montgomery Creek Volt8 P. H __________ Clear Lake ________.
Vollmers ____________ Beegum ____________ Stonyford ______.___
Middletown ________ Squaw Creek ___._..
Stony Gorge Res- ervoir .____________ Paskenta __________.
Redding _______--___ Kennett .___________
Sacramento _________
As soon as it was known that the Sacramento Weir gates would be opened, thus diverting a large volume of the Sacramento River flow into the bypass, warnings were distributed to all those hming interests in and adjacent to the lower Yolo Bypass, informing them that the water level in that basin within the next 48 hours would rise rapidly, and the so-called tidal reclamation tracts would
be flooded. At the beginning of the flood period there was very little snow below the 5,000-foot elcvation in the Sierra Nevada mountains. Above 6,000 feet, rain and snow fell intermittently nt first, but turned to snow later at the higher elevations. While there was some water released by the complete melting of from 12 to 15 inches of snow in the vicinity of the 5,500-foot level, it was not so important as compared with the effect of the unrestricted run-off
from rainfall below 6,000 feet, due to absence of the nor- mal snow pack. Because of the northward movement of the main storm center off the Oregon coast, the region of high-intensity rainfall was confined to the upper half of the Sacramento River drainage basin, including the headwater areas of the Feather River, Putah, Cache, and Stony Creeks. Following 4 days of torrential rains, centered in the Sacramento River canyon, the river a t Kennett crested on the morning of February 28, at the momentous stage of 36.3 feet, which is 3.1 feet higher than the previous high record in 1907, and 7.3 feet higher than in December
1937. By 5 p. m. of the 28th, the flood crest had reached Red Bluff with a stage of 32.2 feet, which is 9.2 feet above the flood stage and 0.2 foot above the previous high-water mark which was established in 1937. Table 1 shows the crest stages reached at various points along the Sacra- mento and tributaries as well as comparative data.
I Y
I
2 s 22 23 24 25 26 a7 2s 29 1 2 3
w s __-__-__-_____--
4 950 .a .30
3,270 .02 0
2,960 0 1.39 2 642 .16 .59
2,100 .25 .39 1,3,50 0 1,332 .07
1 mi 0 . os
11105 0 1.30
wx) .og 1.75
800 .02 740 .o4 718 T T 655 .i o .23 25 .O i . 02
3: 555 .O@ .38
2'300 .17 1. 10
a: 145 .17 .58
1'205 o .12
0 34
0 l1
TABLE 1.-Crest slages and comparative data, high water, February- hfarch 1940
0 T .33
.06 0 0
0 0
0 0 0 0
38
.38
Stat.ion and river
0 6.30 .25 7.83 0 11.34 0 19.70
.50 6.47 34 13.67 0 11.15 32 4.64 0' 7.11 0 14. 55
.05 4.92 0 6. 19
.05 13.03 .40 15.53
Bucks Storage Res- ervoir _..._________ Cflnyon Dam ______.
Stirling City _._____. Brush Creek ________ Quincy _____________ West Branch _______ Feather Falls _______ De Sable. __________ Challenge -... _______ Bucks Creek ____-__ Las Plumas _________ Oreville ____________
coluss.-: _.._. .. ______ 29.5 Knights Landing ______ 34.0 Sacramento ___________ 28.5
5 070 T .39 4' 5iO . @2 06 3: 525 T T 3,800 0 0 3 409 0 T 3: 216 .03 .01 2,973 0 0 2.700 T T 2,700 0 20 1,750 .02 0 569 0 0 273 o 0
T
.32
. 19 .03
.30 25
.30 .10
T
0
0
Colgate _____.._.....__ 14.8 Secondary crest--- 14.8 Marysville _______._.__ 25.0
17.86 .0411.39 20.49 16.69 11.19 18.04 13.08 17.47 14.72 15.73 15.21 5.63
American River I
Time and date
Folsom ____....________ 19.1 H Street Bridge _______ 39.2
De-
Par-
;ry: flood stage
Bowman Dam--.-- Lake Spadding---. Scales ._....________
Deer Creek _____.__. North Bloom5eld--. Downieville ..______
Camptonville ..-... Nevada Clty _____..
Chute Camp ______.
Colgate ._---__..____
Lisbon _____. ._________ 22.8. Liberty Is. F m s _____ 17.9,
5 347 T 5:070 .08
4.300 0 3 7 0 .oi 3: 100 0 2.890 0 2 850 12 9'570 0' i:3s8 o 582 o
0 l2 16
0 0 0
0
O4l
.23 .16 0
.33
0
T .38
l-
'1% O.48 .% .84 .97 .73
.43 .73 .l l
.75 0 .9fi .62 .59 .32
1.10 .n7 .33
l:E O.75 l:E
1.13 0 .47 1.85 .Q? .55 .26 .Cn .52
.84 0 .37 0 0 0 0
.50 .46 .16
1.28 .92 .Cn
1.32 0 .38
1.91 2.40 2.42
2.45 2.95 .75 2.36 1.40 0
2.71
.70
1.90 1.13 1.73 2.85 1.64 1.96 1.02
2.00
1.08 1.25
.58
.58 1. 29
.89
1.14
.54
T .36 14.23 T .21 15.64
0 0 17.40
.27 .31 14.B .37 .16 17.35 .10 .I4 11.15 0 .12 12.63 .21 0 10.26 0 .I4 8.12
o . zn 16.08
0
.O? .21 T .34 .15
.40
.?O
0
0
0
0
.05
.05
.06 0
9:35 a. m. Feh. 27_- ______ 1230 a. m. Feb. 28.- __ -...
11 p. m. Feb. 28 ..-- -3.0
Sacramento River
Kennett _______________ Red Blutl .....__._____
Hamilton City ________ Ord Ferrv _________._..
-
36.3 32.2
22.6,
121.6
9 a. m. Feb. 28 _____ 5 p. m. Feb. 28 .____
4 p. m. Feb. ?8 .____
7 p. m. Feh. 28 ._.__
630 a. m. Mar. 1..- 8 a. m. Mar. 1 ______ 11:lO p. m. Feb. 27-
+11.3 +9.2
+2.6
..__..
+1.5 $4.0
-. 5
~~~
High stages previous floods
.____' __.._____....___ 29.3, March 1907--- 32.2, March 1907-_- 29.6, January 1909-.
De-
1937
121.0 28.8 32.6 27.7
1-
.MI
.62 1.25 .51 1.53 .67 1.05 1.85 .90 1.21 .93 .75
1.36 2.09
.35
.72
33.2, March 1807- __ 29.0 30.5, February 1909- 32.0
W.6. March 1928--. 22.8
3.64 1.69 3.00 2.75 3.72 2.83 2.72 2.21 3.58 2.96 3.53 2.30 3.46 2.95 2.45 2.03
3.40 2.25 3.73 1.05
4.43 1.46 2.01 1.47
1.64 1.05 1.43 .95
2.11 1. w
1.34 .63 .aB2.9S .52
T .13
0 31
.27 .20
.13
.ll
0 0
0 0
.05 .I2
.oi
o .O?
Intensive rainfall was centered in the Sacra.mento River
canyon area above the Shasta Dam construction site. At Kennett 12.51 inches of rain fell in 2 days. Other high 48-hour amounts are: Hobergs, Lake County, 16.55 inches; and Stirling City, on the West Branch of the
Feather River, 15.20 inches. The greatest 5-day rainfall,
20.15 inches, also occurred a t Stirling City. Table 2
shows the daily rainfall during t,he storm period for most, of the mountain stations in this river district.
TABLE 2.-RainfaU from Feb. 29 to Mar. I, 1940, dnclu.sive (inches)
February 1 March I I
8.05 9.32
lg2: :; l?. 80 10.20 9.95 11.04
11.46 9.01 10.66
5.62
6.17
5.88
8.03
e.12 6.44
Twin Lakes. _.____.
Soda Springs _______ Blue Canyon ______.
Riverton .____.___..
Gold Run __._......
IOWB Hill ____._.___.
ColfSX ......_______.
Georgetown _.______
Foresthill .__________
Placerville ...-. _____ El Dorado P. H.--. Folsom ___.________
7.920 6,752 4,750 3.230 3.227 2.970 2.421
2,300
2,200
1.925 1.887 252
0 5.63
Feather Rioer
Oroville __________.____
Nicolaus _______.._____
Yuba Rim
=cuther I I I I I I I I I I I I
25.1 26.3 1201 a. m. Feb. 28-- 6 p. m. Feb. 29 _____ +. 1 +l. 3
Yuba-Bear River I l l l l l l l l l l l
1 a. m. Feb. ?.8 _____ 4 a. m. Feb. 28 _____
American River 1 I
-. 8 Cosumnea River
Fiddletown _________ Big Canyon Mine-.
Culaveras River
Ban A n d m ._______
Tuolumnc River
Hetch Hetchy .____.
Senora--- __________
2,100 850
996
3,530 1,825
Rong Creek
St. John _______________
Mokelumne Riw
Bensona Ferry ________
Sun Jwquzltn Rim
Lathrop _______________
Yolo avposs
13.9
13.3
14.4
230 p. m. Feb. 28-.
7a.m. Feb.29 _____
11 a. m. Mar. 2 _____
+l. 9
$1.3
-2. e
~~ ~~
In contrast to the meteorological conditions that im- mediately preceded the 1937 flood, when an extensive over- running semitropical Pacific air mass aloft caused almost
9 a. m. Mar. 1 _.____
10 a. m. Mar. 1 _____ _______ ______.
MARCH 1940 MONTHLY WEATHER REVIEW 73
unprecedented excessive rains to reach the Sierra summit with dashing run-off in headwater areas, the recent storm by comparison was not so intense at high elevations, al- though the period of effective rainfall this year embraced about 7 days, as compared with about 3 days in 1937.
While the rainfall 111 the February storm was excessive, it was not of the heavy cloudburst type generally in the higher mountains, as was characteristic in 1937. Conse- quently, the streams, althoqgh substantially higher this year, did not rise with such great rapidity, but the high flow in the river was sustained for several days longer this year, a condition that was especially damaging to levees, particularly on March 1, when accompanied by strong north winds that induced destructive wave action. The development of this flood in record proportions resulted largely from the fact that the requisite conditions necessary for high water were being built up over a period of 2 months. From continued rains the soil was thoroughly saturated and in a condition for a high percentage of run-off over a watershed with a comparatively high snow line. Also the streams and bypasses were already carry- ing large volumes of water. Preceding the 1937 flood, some OI these factors were not so highly developed. Some of the remarkable features of the recent flood were: (1) Notwithstanding the unparalleled high water in the upper Sacramento River, Stony Creek with even greater abnormality, caused the Sacramento River from Ham-
ilton City to Butte City to crest in advance of the up- stream peak flow. (2) Immediately following the break
in the levee on the Sutter and Tisdale Bypasses, the water level in the river and bypasses fell rapidly downstream, reaching the Delta region within a few hours, whereas the usual time interval is about 2 days. (3) Another feature
was the long flood wave that was in progress from Kennett to the mouth of the Feather River on February 28, form- ing an unbroken wall of flood water for about 250 miles. I t is believed that adequate and timely warnings were issued by the Weather Bureau when early in the storms development warnings were issued to the effect that conditions would equal or exceed the 1937 flood. These warnings were consequently of inesiimable value to farmers, stockmen, reclamation district officials, engi- neers, Red Cross officials, and others affected by the water situation; as all interests knew what to expect, becausc memories of the 1937 flood were still in mind. The extraordinary vigilance that was maintained by supervising engineers and reclamation officials throughout the valley in safeguarding levees that were severely strained, and in repairing hundreds of minor breaks, was instrumental, no doubt, in preventing wholesale disaster in many areas. For esample, the Sutter Basin with a
60-mile levee system, was saved only by desperate efforts. The magnitude of this flood in the upper Sacramento
Valley can be realized by considering that it is the greatest for a period of about 40 years, or since authentic records have been kept. However, farther down the river, where the flood-control system with its bypasses and levee-con- struction work has been constantly changing conditions, the present river-gage heights are not comparable with those of earlier years and consequently are not a true index to the volume of water that is being discharged by the system. Yet it is true that the gage readings are representative of the danger present and indicate the responsibility of the Weather Bureau in issuing adequate
warnings. Before there was any flood-control system in operation in the Sacramento Valley, the overflow waters drained into natural basins of unreclaimed land on each side of the river. Under present conditions where the water is con-
fined to leveed channels, gage heights are not only pro-
portionately higher for the same volume of water, but failures in levees are more disastrous because more reclaimed lands are affected. This, in a general way,
explains why the Weather Bureau, being primarily con- cerned whh floods, uses the river gage height as a measure of flood danger instead of the flow in second-feet. In this
connection it may also be explained that the gage height representing t,he flood stage that is assigned to n station on a leveed stream represents the danger stage rather than overflow stage. Overflow due to the high water was extensive. Some
of the major inundations a,nd the acreage affected are as follows :
East of Hamilton City 60,000 acres were under water. This was considerably more than in 1937 although the crest at Hamilton City was 0.2 foot lower than in 1937.
During the early morning of the 29th) numerous levee failures in the Butte City-Princeton a.rea caused increasing overflow on bosh sides of the river. On the east side, t,he
combined overflow waters from the river and from Butte and other creeks, en route to Sutter Bypass, covered an area of about 145,000 acres in the Butte Basin, which contained mostly grain lmd. On the west side of the
river, water esca.ped from a dozen breaks between Ord Ferry and Princeton and covered about 120,000 acres of
reclaimed land in the Colusn trough area. At the peak of the flood wave, on the early morning of March 1, failure of the levee on Sutter Bypass, east of Meridian and on the north side of Tisdale Bypass, caused inundation of 37,000 acres of highly valuable farm land. In the Yo10 Bypass and the adjacent Delta region, the total acreage of the five principal island tracts flooded was approximately 30,000.
In addition to the flooding of farm lands, the outskirts of many towns in the central valley were flooded and were more or less isolated for a period of time because highways and railroads became impassable and wire and power lines were decommissioned. All persons in the inundated areas were generally warned in advance to evacuate the danger zones: There were some cases in farm districts where families were marooned in houses by the sudden breaking of levees,
but these persons were rescue.d in boats by the Red Cross and other workers. According to records of the Ame.rican Red Cross no persons were injured but two lives were lost. A very specia,l effort was made to secure reliable sta- tistics of losses sustained by reason of the flood. The
tabulation below is the result of questionnaires returned from authentic sources of information. Judgment was
exercised to exclude any overlapping estimates in reports from different sources. The items were obtained mostly from County and State, officials. Comparisons were also
made with the State Engineers Office which collected similar data. The figures given by the Weather Bureau relate to the Sa.cramento and lower San Joaquin Valleys, and include losses occasioned by stream flow only. For the Sacramento and Lower San Joaquin Drainage Areas :
Estimated total property damage of all kinds caused by stream flow 1 ________________________________ $6,731,054 Estimated value of property saved by warnings- - - - - - $2,060,000 Total acreage of agricultural lands flooded (approxi- m a t e l y )-_-_-______-_---------------~---------- 508,798
1 Not included are general storm damages, such as from wind, snd earth slldes and erosion in the mountains. The State of Cahfornia Publlc Works Department, eathates a loss of $12,041,600, covering all losses from the storm for the entire state.
Acknowledgment is made of the valuable assistance given by all of-the observers who stuck to their posts and
74 MONTELY WEATHER REVIEW MARCH 1940
made rainfall and river-gage readings frequently during telephone calls as to the behavior of the river; also of the
day and night; of the aid given by United States engineers valuable cooperation of the telephoneand telegraphcompa- who, particularly in one case, assigned two of their nies, the radio and the press, in distributing warnings. employees a t Marysville to help our river observer In this connection it should be stated that the Red
during the emergency, the engineers, in. day and night Cross and other agencies promptly provided all necessary shifts taking hourly readmgs and answermg hundreds of relief and rescue facilities throughout the Valley.
NOTES AND REVIEWS
0. HOELPER. Atmospharische Triibungs-und Wasserdampfbestim-
mungen naeh Filtermessungen der Sonnenstrahlung. Reichsamt
fiir Wetterdienst, Wiss. Abh. 6, n. 10, 49 pp., Berlin, 1939
Filter measurements of solar radiation, and their re- duction by .hgstroms method to obtain dust turbidity and precipitable water in the atmosphere, are here pub- lished for Potsdam, Schomberg, Davos, and Zugspitze. Data for Aachen have already appeared (Deutsches Met. Jahrb. Aacben fur 1933, 55-62, 1935).
The practical difficulties in the way of getting sufficiently accurate solar radiation measurements seem to have been to a large degree responsible for the limited use of this theoretically very simple method for getting the total moisture content of the atmosphere above any station. These difliculties are here reviewed. It is pointed out that concurrent readings from several stations all within the same air mass, have helped to remove some of the errors; conversely, agreement in the results of independent and well-separated simultaneous observations has em- phasized the uniformity in some of the characteristics of an extended air mass. Theoretical difficulties of the Angstrom method, such
as the assumption of a mean effective size of scattering particle, and the anomalous behavior of scatter in the UV region, are claimed to be of little consequence in view of the rough nature of the required characterizations of the
atmosphere. Hoelper sets up a transformation table to put the results of observations at Blue Hill and Washington (pub- lished in the MONTHLY WEATHER REVIEW, 1933-37) in terms of the European reductions. Much of the disparity
in the Blue Hill results is supposed by Hoelper, as by Kimball, to be probably traceable to improper filter trans- mission factors. It may be mentioned here that in September 1938 it was discovered a t Blue Hill that both the OG-I and the RG-2 Jena glass filters, continually exposed there in clear or partly cloudy weather during the previous 5 years, had steadily deteriorated by crystal- lization a t and just below the glass surfaces. Subsequent development of an empirical method for estimating the curve of transmission decrease of these filters with ad- vancing time made possible the reevaluation of Blue Hill turbidity measurements now under way. Hoelper discusses a new method for correcting the re- ductions to turbidity and water-vapor content on non- normal days. It was found that observations indicating extremely high or low turbidity did not yield true values of precipitable water by the usual reductions. By the use of simultaneous airplane observations of atmospheric moisture content, a correction curve may be developed for any station, based on the differences between the pre- cipitable water found by the two methods, plotted against the difFerences in the corresponding turbidity coefficient obtained from two spectral regions. This curve permits
adjustment of the quantity of precipitable water obtained through radiation measurements and use of the corrected quantity to obtain a truer value of the turbidity, A few
successive approximations suffice for even the most ex-
treme conditions, It is felt by Hoelper that this method provides, where necessary,. at least a partial correction for the hgstrom approximation in assuming a mean effective size of scattering particle. Another subject discussed by the author is the fre- quently observed inconsistency between the surface vapor pressure and the precipitable water as obt,ained by the
filter method. The mean relation between the two does not conform to theory, for a nonlinearity appears when they are plotted in a scatter diagram. This is similar to the nonlinearity found in recent spectrographic measures of water-vapor absorption when plotted against the cor- responding surface vapor pressure (Herzing, Gerl. Beitr. 49,71,1937). It seems to be accounted for by considering Fowles absorption F, due to water vapor, not as a mean function of W-m (where m is the optical air mass) but as a family of curves, each of constant m. It then appears that for large m, F falls below themean F for all W; and for small m, F lies above the mean F. Thus an observed
F in winter (with relatively large m) should yield a much higher value of W-m than the same F in summer. It is
of course understood that the preceding correction only partially meets the difficulties inherent in approximating the total precipitable water from the surface vapor
pressure. Perhaps the outstanding contribution of this paper is in calling attention to the importance of essentially simul- taneous solar observations. Conhation of the results of one set of observations by the results of an entirely independent set is one of the fundamental controls in scientific research. For estimating the effects of the especially numerous known and unknown sources of error afflicting solar radiation measurements, particular emphasis on concurrent observations offers one of the most important possibilities.-Edmund Schulman.
W. W. SPANOENBERG. StrahlungsKlimatologische Betrachtungen. Aus d. Archiv d. deutschen Seewarte, 68, n. 8, 32 pp., 1938.
The author compares the mean monthly values of transmission, turbidity, and maximum intensity of both the total and the red-infrared radiation at eight stations of varying elevation in central Europe. The differences
are discussed in terms of variations of the climatic elements in place and time. Of especial interest is the discussion of intensity fluc- tuations of a few minutes duration. In absolute value as
well as in percent, these fluctuations are shown to vary
inversely with the solar elevation, for the total as well as for the less fluctuating red radiation. Variations up to 30
percent for large air masses are found. Wind, in com-
bination with stratified or otherwise heterogeneous distri- bution of dust and other scattering and absorbing particles, is held to be the causative agent. The effect of the lowest
layers of the atmosphere in introducing long-period (month-to-month) variations in radiation is emphasized; at relatively high solar elevations these variatinos ap- parently smooth out.--Edmund Sehulman.