Spatial variability of the wind field in the area of the Kuril Islands George V. SHEVCHENKO and Vladimir Yu. Saveliev Institute of Marine Geology and Geophysics, Russian Academy of Sciences, Yuzhno-Sakhalinsk, Russia Introduction Examination of time and spatial variability of Sakhalin Paramushir IslandSHUMSHU wind field is important for various applied prob- lems. In particular, the problem of evaluation and Sea of Okhotsk development of wind power stations recently be- MATUA s d came crucial for the region of the Kuril Islands. n la Is Climatic characteristics of wind presented in gen- l ri u erally used manuals (Climate Guide, 1969; Ko- K SIMUSHIR shinsky, 1978; Pacific Ocean, 1966) are mainly based on wind data obtained by weather vanes. KURILSK Since the end of the 1970s more precise instru- N Kunashir IslandIturup Island ments have begun to be used to measure wind at Pacific Ocean meteorological stations of the former USSR. Pre- SHIKOTAN liminary analysis of old and modern data showed Hokkaido significant difference of the corresponding esti- mates. The purpose of the present work is to ex- Fig. 1 Location of the meteorological stations in amine the spatial structure and to obtain some cli- the area of the Kuril Islands. matic characteristics of the wind field in the vicinity of the Kuril Islands based on the modern wind data. and Kurilsk (Iturup Island) for the period 1966- 1984 prepared at the World Data Center (Obninsk, Russia). The location of the meteorological sta- Observational data tions is shown in Figure 1. We chose stations For analysis we used 10-min averaged wind data Shumshu and Shikotan rather than the nearby sta- from stations Shumshu, Matua, Simushir and tions Severo-Kurilsk (Paramushir Island) and Shikotan, located on the corresponding islands, Yuzhno-Kurilsk (Kunashir Island) since the wind and from station Kurilsk, located on Iturup Island, at the former pair is less influenced by the local for the period 1966–1984, prepared at the World orography than at the latter. The analysis of the Data Center at Obninsk, Russia. The location of data has revealed their essential heterogeneity, the meteorological stations is shown in Figure 1. much of the information before 1980 pertaining to We chose stations Shumshu and Shikotan rather measurements executed by weather vanes. So, for than the nearby stations Severo-Kurilsk on Para- more detailed examination we used series for mushir Island and Yuzhno-Kurilsk on Kunashir 1980–1984 since all these data were made by the Island, for the reason that the former pair is less same type of the instrument (anemorumbometer influenced by the local orography than the latter. M-63M) and had no gaps. The analysis of the data has revealed their essen- tial heterogeneity, much of the information before Recurrence of the wind by directions and speed 1980 pertaining to measurements executed by gradations weather vanes. For a more detailed examination we used a series for 1980–1984, since these data Figure 2 presents diagrams illustrating the wind had no gaps and were obtained by the same type of distribution by directions and speed gradations. instrument, an anemorumbometer M-63M. There are two maxima in the distribution of the wind speed: the main maximum corresponding to We used for analysis 10-min averaged wind data the typical wind speed of 2–4 m/s (3–5 m/s at from the stations Shumshu, Matua, Simushir, Shumshu), and a secondary maximum at 10–12 Shikotan (located at the corresponding islands) m/s. Such character of speed distribution remains 49 (a) Shikotan (b) Kurilsk 6,5 20,0 (c) Simushir (d) Matua 10,6 12,7 N (e) Shumshu 0 5 10 Frequency Scale (%) 6,9 5 10 15 20 25 30 Speed Scale (m s–1) Fig. 2 Diagrams of the direction distribution by the 5-yr averaged wind velocities for various Kuril meteorological stations. Contribution of calm weather (winds weaker than 1 m/s) is presented in the centers of the diagrams (in %). 50 basically the same for all stations and all seasons. distribution of atmospheric pressure in summer.) However, in winter, when winds are normally That means that the wind field in this area cannot stronger, the second maximum intensifies and the be satisfactorily described by a simple layout: The main maximum becomes weaker; the opposite winter monsoon with northwesterly winds is re- tendency is observed in summer. placed by the summer monsoon with southeasterly winds (Pacific Ocean, 1966). The “wind roses” (Fig. 2) demonstrate noticeable spatial variability of wind directions. Northwest- It is interesting to note that the wind velocities erly winds prevail at all stations, however the near the Kuril Islands are found to be weaker than other features are different for different stations. is usually assumed: according to Climate Guide Thus, in the vicinity of Shumshu Island winds (1969) extreme wind velocities in this region are from directions other than northwest are weak and up to 50 m/s. Results of the present examination infrequent. In contrast, near Matua Island north- of wind data for the period 1970–1984 showed erly winds are observed frequently, for Kurilsk that none of the five analyzing stations recorded easterly winds are rather frequent, for Simushir wind velocities exceeding 30 m/s. The total southeasterly, and for the area of Shikotan Island amount of the cases with wind exceeding 20 m/s is southerly winds occur quite often. rather insignificant, from 0.4% at Matua up to 2.5% at Simushir. These extreme winds with The dominant northwesterly winds are a typical speed up to 28–30 m/s are mainly observed in autumn-winter feature for the whole area of the March or in October and November (Fig. 4a). The Sea of Okhotsk (so-called “winter monsoon”, re- strongest winds have northwesterly direction for lated to the influence of the Aleutian Low). The the southern and central parts of the Kuril Islands, corresponding spatial distribution of the sea sur- southwesterly at Matua, and northeasterly at face atmospheric pressure in the area of Okhotsk Shumshu. These months correspond to the time of Sea is shown in the Figure 3a. In the spring- the major cyclonic activity in this area. The distri- summer period the air streams near the Kuril Is- bution of the extreme wind shows that the corre- lands are apparently not so stable, resulting in the sponding cyclones cross the chain of the Kuril Is- variety of the winds from the other directions ob- lands just in the center, near Matua Island. served in this period. (Figure 3b presents a typical Fig. 3 Typical spatial distribution of sea surface pressure in the area of the Kuril Islands for (a) January and (b) July according to Pacific Ocean (1966). 51 (a) (b) Shikotan Shikotan Kurilsk Kurilsk Simushir Simushir 30 m/s5 m/s Fig. 4 (a) Maximum monthly and (b) mean monthly winds for the period 1980–1984 for the meteoro- logical stations in the area of the Kuril Islands. It is interesting to note that the wind velocities varies siginicantly from year to year, except at near the Kuril Islands are found to be weaker than Shumshu where northwesterly winds are domi- is usually assumed: according to Climate Guide nant, and from station to station. Typhoons which (1969) extreme wind velocities in this region are are coming from the tropical Pacific into the area up to 50 m/s. Results of the present examination of the Kuril Islands in summer and early fall are of wind data for the period 1970–1984 showed probably the reason for destabilizing atmospheric that none of the five analyzing stations recorded circulation and producing storm winds of various wind velocities exceeding 30 m/s. The total directions. amount of the cases with wind exceeding 20 m/s is rather insignificant, from 0.4% at Matua up to Monthly mean winds 2.5% at Simushir. These extreme winds with speed up to 28–30 m/s are mainly observed in Spatial and temporal variability of monthly mean March or in October and November (Fig. 4a). The winds averaged over 5 years (1980–1984) is strongest winds have northwesterly direction for clearly seen in Figure 4b. The primary feature of the southern and central parts of the Kuril Islands, the wind field is the very strong seasonal change southwesterly at Matua, and northeasterly at of wind velocity. In the cold season (October– Shumshu. These months correspond to the time of March) mean winds are sufficiently strong and the major cyclonic activity in this area. The distri- steady. For the whole area of the Kuril Islands, bution of the extreme wind shows that the corre- they have northwesterly direction; variations from sponding cyclones cross the chain of the Kuril Is- station to station are insignificant. In contrast, in lands just in the center, near Matua Island. the warm season (April–September), mean winds are much weaker and there is essential difference The complicated picture of maximum winds is between the two northernmost stations Shumshu observed in summer. Extreme wind speeds are and Matua and the others. At stations Shikotan about 17–25 m/s, the direction of maximum winds and Kurilsk in the South Kuril Islands, winds change direction to the southerly and 52 the southerly and southeasterly, i.e. the wind field · In winter, significant northwesterly winds as- takes the character typical for summer monsoon. sociated with the Aleutian Low prevail in the A similar picture but not so evident is observed area of the Kuril Islands (“winter monsoon”); also at Simushir. At the same time, monthly mean however there are noticeable differences in winds of northwesterly and westerly direction pre- distribution of wind directions (“roses of vail at Matua and Shumshu.