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NLC OBSERVATIONS IN FINLAND 1997
Report by Veikko Mäkelä
Ursa Atmospheric Optics Section have recorded NLC observations since
early 1980's. Earlier the observations have been published in paper
reports. Since 1989 Reports have been published only in Ursa Minor
bulletin of Ursa sections.
The summer 1997 was rather successful, even there were only seven
observers. July 1997 was one of the most active months in the history
of the section. 22 display were detected, 4 nights were negative and 5
without observations. During Aug 1-16 there were still 7 displays.
Unfortunately June was poorly observed, partly due to the lights skies
in the most parts of Finland.
With verbal description, some numeric estimations have been used:
W wideness (1-5, 1 = single forms, 5 = all-sky)
I intensity (1-5, 1 = faint, 5 = remarkable bright)
S structures (I = veil, II = bands, III = billows, IV = whirls,
0 = unkonwn, unclassified, K = "knots", S = "crossing
streaks"
N = "net-like")
r reliability (0 = unsure, 1 = quite sure, 2 = sure)
OBSERVERS
Name Code Sites obs neg
Jani Katava KAT Helsinki, Raisio 6 -
Tomi Lyytikäinen LYY Helsinki 3 -
Olli Manner MAN Helsinki 3 -
Veikko Mäkelä MAK Helsinki, Hämeenlinna 4 2
Pekka Parviainen PAR Kustavi, Turku, Paimio 14 -
Leo Rajala RAJ Jämsä 18 7
Teemu Öhman ÖHM Oulu, Äänekoski, Hämeenlinna 3 1
obs = NLC displays, neg = negative observations
JUNE
27/28.6. W=2, I=3, S=II+IV, r=2
Small display with two small areas. Bands in both areas.
MAK,RAJ
JULY
1/2.7. W=3, I=4, S=I+II+III+IV, r=2
Quite a large NLC area. Some billows, which disappered later. One
strong
whirl and band structure. Top brightness was 4 (1-5).
LYY, RAJ
2/3.7. W=3, I=2, S=I+II, r=1
About 60 degrees wide area with veil and bands. Few bands also in
eastern sky. Intensity was low maybe due to light sky.
RAJ
5/6.7. NEG, r=1
MAK
6/7.7. W=3, I=3, S=I+II, r=1
About 90 degrees wide area. Veil+band type display. The brightest
structure was a strong band (I=4).
MAN,PAR
7/8.7. W=2, I=2, S=0, r=1
50 degrees wide area with undefined structures. Quite faint display.
The
weather conditions were poor.
PAR
8/9.7. W=3, I=4, S=I+II+III+IV, r=2
Display mainly in the western sky from all the thre observers.
Band+billow
type structure, bright billow observed by Parviainen and Lyytikäinen.
The
top intensity was 4. The stereo photographing by Parviainen.
KAT,LYY,PAR
11/12.7. W=4, I=5, S=I+II+III+IV+S+P, r=1
Bright display detected only by Lyytikäinen (perhaps cloudy in other
sites). Wide area, all the structures. Dominating forms were bands and
strong whirl. Yellowish and brownish color also observed.
LYY
12/13.7. W=4, I=3, S=I+II+III+S+P, r=1
A half-sky display by Rajala (30 degrees over zenith). Manin band type
display, with "knots" and crossing streaks. Also some billows existed.
Fast motion to northwest.
RAJ
13/14.7. W=4, I=4, S=I,II,III,IV,S,P, r=2
As large as the night before. Bands were directed SE-NW. Very active
and dynamics display with sharp edged bands and strong whirled area.
Some herring-like structures and billows, too. The motion westwards or
northwestwards.
MAN,PAR,RAJ
14/15.7. W=1, I=4, S=II+0, r=2
The fourth night with NLC. Small area display in north with band type
structure. Two bright yellowish patches reported by Mäkelä. The NLC
disappeared about 1:00 local daylight saving time.
KAT,MAK,PAR
15/16.7. r=1
In the beginning of the night negative observations (KAT,MAK,RAJ). At
2:00 local time Manner report some NLC.
MAN,KAT,MAK,RAJ
16/17.7. W=2, I=4, S=I,II, r=2
Some faint bands and veil. Area was first in NW-NE, later in east by
Rajala. Some cloud distrubed observations.
MAK,PAR,RAJ
17/18.7. W=2, I=3, S=I,II,III, r=1
Medium bright display with 70 degrees wide area. Sharp IIb bands as
dominating structures in NW. Also some billow groups. Possible motion
to NW.
RAJ
18/19.7. W=2, I=2, S=II, r=1
Faint bands in NNW. The observations were interrupted by clouds.
RAJ
19/20.7. W=4, I=3, S=I,II, r=2
Mainly western sky display with quite a large are (up to 50-60 degrees
by Mäkelä and Öhman, over zenith by Rajala). Mainly band type display,
some billow observed by Öhman. Top intensity 3.
MAK, PAR, RAJ, ÖHM
20/21.7. NEG, r=1
RAJ
21/22.7. NEG, r=1
RAJ
22/23..7. W=2, I=3, S=I,II,III, r=1
40 degrees wide band+billow area in N. The brigthnees increased (max.
I=3) to 1:00 local time, then the NLCs disappered.
PAR
23/24.7. W=4, I=3, S=I,II,III,IV, r=1
Quite a large display, upper limit almost in zenith. Veil, bands and
billows. In the midnight strong band with crossing streaks. Later the
band disappered, streaks were left. Motion to SW. The intensity
decreased at 1:00, probably due to Earth's shadow.
RAJ
24/25.7. W=2, I=3, S=II,III, r=1
Bands and billows. Brightness mainly 3, but few bands brightened up
to value 5 for a moment. Motion southwards. There were some cloud
disturbance in observation.
PAR
25/26.7. W=3, I=3, S=I,II,III, r=1
Veil+bands and strange lenticularis like billows or patches. They
were quite regular sized (0,5x3-4 and 0,5x1-2 degress). The intensity
was 2-3 and the area width about 70 degrees.
RAJ
26/27.7. W=2, I=3, S=II,III, r=1
Fifth night with NLC in row! In the beginning faint, later medium
bright bands and billows. There was cloud disturbance in observation.
PAR
28/29.7. W=2, I=4, S=I,II,III, r=1
Poor observing conditions. Some rather bright band+billow structures
were visible throught cloud caps.
RAJ.
29/30.7. W=2, I=1, r=1
Some unindentified faint NLC forms. Clouds disturbed observations.
PAR
30/31.7. W=3, I=3, S=I,II,IV,0, r=2
The observing conditions were poor in both sites. Some veil and
unsharp (IIa) bands was observed. Rajala reported also whirl
structures and some unclassified NLC forms. The reports of the
both observer are made about different NLC areas. The intensity
was 3.
PAR,RAJ
31.7./1.8. NEG, r=1
RAJ
AUGUST
1/2.8. W=3, I=2, S=I,II, r=1
Rather faint veil+band type display. The area was small, 20 degress
wide in low altitude in N.
RAJ
3/4.8. W=2, I=2, S=II, r=1
A little unsure case. Some bands in NE.
ÖHM
4/5.8. NEG, r=1
RAJ
5/6.8. NEG, r=1
RAJ
6/7.8. W=2, I=2, S=I,II,III, r=2
Veil and bands between N and NE. Later the area expanded northeastwards
(due to Earth's shadow?). Later there were also billows. The intensity
were low (I=2).
PAR, RAJ
8/9.8. W=3, I=3, S=I,II, r=2
Veil and bands. In Raisio, Southwestern Finland Katava observed
20 degrees wide bluish area with veil. The intensity was low in
the beginning, but the display brightened later.
KAT,RAJ,ÖHM
9/10.8. NEG, r=1
RAJ
10/11.8. W=4, I=4, S=I,II,III,IV,S,P, r=2
The display with many structures (veil, bands, whirl, "knots" and
"streaks"). Billows were reported by Öhman. In the midnight the
display were low in the north, but in the morning, 4:00 local time,
the areas expanded as an all-sky display. The top intensity was I=4.
PAR, RAJ, ÖHM
13/14.8. W=3, I=4, S=I,II,III, r=1
Quite a nice display. Some medium bright NLC (veil, bands and billows).
There were also some brighter points in NLC forms.
(tm)HM
16/17.8. W=2, I=4, S=II, r=1
The last reported NLC display in 1997. 20 degrees wide group of bands.
it brightened up to I=4 (probable this was contrast effect between dark
sky and NLCs).
RAJ, ÖHM
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