Faculty of Engineering, Kyushu University, 744 Motooka, Nishiku, Fukuoka, , Japan d

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1 Full Paper Journal of Agricultural Meteorology 71 (4): , 215 An artificial rainfall experiment based on the seeding of liquid carbon dioxide by aircraft on December 27, 213, at Saijo, Ehime, in the Inland Sea of Japan Taichi MAKI a, d,, Osamu MORITA b, Koji NISHIYAMA c, Yoshinori SUZUKI d and Kenji WAKIMIZU e a Japan International Research Center for Agricultural Sciences, 1-1 Ohwashi, Tsukuba, Ibaraki, , Japan b Office for a Sustainable Future, Fukuoka University, Nanakuma, Minamiku, Fukuoka, , Japan c Faculty of Engineering, Kyushu University, 744 Motooka, Nishiku, Fukuoka, , Japan d Professor Emeritus, Kyushu University, Hakozaki, Higashiku, Fukuoka, , Japan e Faculty of Agriculture, Kyushu University, Hakozaki, Higashiku, Fukuoka, , Japan Abstract An artificial rainfall experiment was conducted using an aircraft to seed liquid carbon dioxide (LCD) under particular weather and topographic conditions near the northern area of Saijo, Ehime, with the climatic type of the Inland Sea of Japan on Dec. 27, 213. Following the seeding, a convective cloud developed quickly above Saijo between 11:3 and 11:5, and rain fell within a short time. A high cumulus cloud was dissipated by the rain, and the cloud over a mountainous area had rapidly and almost completely disappeared by around 12:3, approximately one hour after seeding. The rain at 5 mm/h was observed for 5 6 minutes at around 11:5 at the Saijo City office area, and.5 mm of rain was observed up until 13: at the Saijo Fire Station. This rainfall was believed to be artificial, and it was significant in the southern mountainous area of Niihama and could be clearly observed visually throughout the area from the aircraft at around 12:1. The artificial rainfall was expected to be observed at amounts of.5 mm and 4. mm at Ohjoin and Besshiyama of Niihama Fire Station, respectively, and at.5 mm during the period from 11:5 12: at AMeDAS Tomisato located south of Shikokuchuo. Rainfalls of.5 mm from 14:2 14:3 at AMeDAS Ikeda, 2. mm from 13:3 15: at AMeDAS Kyojo, and 1. mm from 13: 15: in the areas of Miyoshi, Tokushima, and Ohtoyo, Kochi, were thought to be artificial considering the seeding time, seeding position, wind direction, and wind speed. The main line of the rainfall area was Saijo Besshiyama Kyojo, and the effect of the artificial rainfall expanded up to 7 km of the lee side. The amount of rain was estimated at roughly 1.3 million tons in the areas of Saijo, Ikeda, Sugeo, and Kurotakigawa. Thus, the artificial rainfall experiment conducted through the seeding of LCD at Saijo was clearly successful. Key words: Aircraft seeding, Artificial rainfall, Convective cloud, Liquid carbon dioxide (LCD), Saijo City. 1. Introduction There are four existing methods for producing artificial rainfall, i.e., seeding with dry ice, seeding with silver iodide, seeding with liquid carbon dioxide (LCD), and scattering liquids such as pure water, salt water, and so on. However, these methods produce only small amounts of rain and have economic drawbacks; in addition, silver iodide method includes environmental disadvantages. The LCD artificial rainfall technique was invented by Fukuta (1988). The seeding of LCD is done by aircraft that spreads LCD near the base of a cloud in the layer of supercooled humid air mass at temperatures below zero. The sprayed-out LCD cools the surrounding atmosphere to 9 instantaneously and produces ice crystals with 1 13 particles per 1 g CO 2 (Fukuta, 1988); these, in turn, collect ambient water vapor and grow to ice crystals or rain particles, thereby producing snow or rain. This method proved successful at Fukuoka on Feb. 2, 1999, as the first effective rainfall-production method in the world, and a second rainfall experiment confirmed the properties and efficiency Received; November 4, 214. Accepted; March 25, 215. Corresponding Author: maki@affrc.go.jp, makitm@kra.biglobe.ne.jp DOI: 1.248/agrmet.D-14-5 of the LCD method on Oct. 27, 1999 (Fukuta et al., 2; Wakimizu et al., 22; Maki et al., 212). However, for unavoidable reasons (e.g., cloudless or clear days), there was not another successful experiment until 25. Experiments were conducted on Feb. 4 and Nov. 7, 26; on Jan. 8 and 17, 27; and on Jan. 24, 29; other experiments included those in 212 and 213 at Fukuoka, Saga, Yamaguchi, Nagasaki, Tokyo, Ehime, and so on (Maki et al., 211; 212; 213a, b). The results of experiments on Feb. 27, 212, and Mar. 14, 213 were presented in papers (Maki et al., 213a, b; 214a, b). Water deficits are an especially urgent problem in countries with arid or desert climates. Droughts and other water problems are increasing in frequency as a result of abnormal weather and global warming, and a global water crisis is predicted for the 21st century. Because the demand for water continues to increase as the population grows, even in regions where the water supply is currently adequate the demand may finally outpace the supply. Researchers are attempting to find effective techniques for inducing artificial rainfall to help meet the world s water demands, to protect against desertification, and to develop arid lands (Maki et al., 28). This paper presents and discusses the results of an experiment conducted at Saijo City, Ehime Prefecture, on the north side of Shikoku Island in the Seto Inland Sea. This area receives a small amount of rainfall in summer and winter, and its climate type is

2 Journal of Agricultural Meteorology 71 (4), 215 that of the Inland Sea of Japan. In the area, northern winds are frequently observed flowing against the Shikoku Mountains in winter. The experiment was conducted using an aircraft that seeded LCD for about 15 minutes (min) under adequate weather and topographic conditions on Dec. 27, Materials and Methods 2.1 Principles of the LCD rainfall technique This technique of LCD seeding exerts its effects through two processes: (1) air masses with new ice crystals rise due to the released latent heat of condensation, and expand in twin cylindrical vortexes as they reach the top of the cloud, and (2) supercooling clouds with ice crystals rise up in humid air masses, reach the top of the cloud, and grow vertically and horizontally. In addition, the natural updraft in the cloud is increased by the latent heat from the ice crystals and the artificial clouds lifting from the seeded level enter higher-humidity air masses, causing the cloud to grow. Eventually, snowflakes or rain droplets grow large enough to fall to the ground as snow or rain. These convective clouds expand in three dimensions with horizontal and vertical components. The development of clouds is improved and becomes effective when a stable temperatureinversion air layer lies above them, suppressing vertical convection and promoting their horizontal spread. Ice crystals produced by LCD grow actively for.5 to 1 hour (h), mainly after seeding, and the artificial snowfall or rainfall that they induce continues for several hours. 2.2 General weather conditions and experimental methods The surface weather map at 12: JST on Dec. 27, 213 is shown in Fig. 1. The pressure pattern of west high=east low type was recognized, i.e., 4 lows of 99 hpa existed from north to south at Hokkaido and an eastern sea area of Honshu, and a high of 136 hpa existed on the Asian continent. Isobars around the Shikoku District were found as a straight north-to-south line. Experimental conditions are not always perfect, but adequate conditions include air temperature below zero, a convective cloud, wind direction from north to west, topography of high mountains to the south, and so forth. A date for the seeding experiment was chosen two days beforehand based on the weather map, weather forecast, and meteorological data. A Cessna T33 aircraft operated by SGC Saga Aviation Co., LTD, and loaded with a 1-kg gas tank of LCD took off from Matsuyama Airport at 1:36 on Dec. 27, passed over Imabari at the northern tip of Takanawa Peninsula (left side of Fig. 2), observed the winds, seeded LCD at Saijo, observed the clouds, and took photos after about.5 h. It then passed over the southern tip of Takanawa Peninsula along Route 11 and returned to Matsuyama Airport at 12:41. According to the satellite infrared image shown after in Fig. 6, the density of stratocumulus clouds over northern Shikoku District was higher than that over Sanyo District. These clouds were targeted for the seeding experiment. From approximately 11:2 to 11:3, the seeding cloud was partially over 3 m high near Takanawa Peninsula. LCD was seeded at the height of 137 m near the bottom of the 3-m high cloud over the seashore of northwest Saijo. LCD seeding time was from 11:23 11:48 as shown in Fig. 2 as No. 1 4 within the square frame. Four series of seeding lines at the northern regions of land and sea over Saijo are shown at the left side of Fig. 2. The four times of the seeding series are shown in Table 1. The locations of Saijo, Niihama, and Shikokuchuo Cities, the surface observation points, and the flight route during seeding are shown in Fig. 2. The city offices of Imabari, Saijo, Niihama, and Shikokuchuo are shown in black circles. The AMeDAS for Imabari, Fig. 1. Surface weather map of 12: on Dec. 27, 213 (Japan Meteorological Agency (JMA))

3 T. Maki et al. Artificial rainfall experiment based on the aircraft seeding of LCD on December 27 in 213 at Saijo Fig. 2. Flight route, order of seeding route, seeding area of LCD, and observation area on Dec. 27, 213. The seeding orders of color lines are shown as No. 1 4 with square frame. Red circle is AMeDAS observatory (JMA) and black circle is the other observatory. The first seeding (1-1, 1-2, 1-3) is shown in red color, the second (2) yellow, the third (3) green, and the forth (4) blue. Table 1. Seeding series, seeding time and seeding direction of LCD on Dec. 27, 213. Series Seeding time (seeding period) Seeding direction 1 11:22:57 11:27:15 (about 4 min) :33:25 11:34:4 (about 1 min) 11:35:4 11:39:2 (about 4 min) 11:42:52 11:48:15 (about 5 min) 1st:1 1 from north to south, 2nd: 1 2 from west to east, and 3rd: 1 3 from south to north from south to north from north to south from west to east Niihama, and Shikokuchuo, except for AMeDAS Saijo, are not shown because they are close to the city office and each other. The AMeDAS at Saijo, Tomisato, Ikeda, and Kyojo are shown in red (gray for monochrome) circles, and other observation points are represented by black circles. After the seeding flight, the author conducted a hearing and research about the surface conditions around Saijo and Niihama on Dec. 27 and 28. The data of surface and upper-level weather, radar, satellites, etc. were collected mainly by the Japan Meteorological Agency (JMA) and analyzed. 3. Experiment Results 3.1 Movement of the convective cloud and the production of artificial rain over the Saijo area When the aircraft reached an upper level air east of Imabari at approximately 11: on Dec. 27, we investigated wind direction, wind speed, and cloud conditions. After then, we seeded LCD around the upper air (137 m) north of Saijo, and observed the cloud and rain status in the areas of Saijo and Niihama. As there was no temperature-inversion layer, the developing limitation of a convective cloud was not found, and cumulus clouds developed to 3 m in height partially near the seeding area. Figure 3 shows the photos of (A) a convective cloud before seeding near the bottom of the cloud around 11:2; (B) the sky clearing after rain fell near central Saijo (business and shopping area) around 12:; (C) snow or rain as virga near the mountainside of Niihama around 12:1; and (D) the sky clearing after rain fell near the northern mountainous area of Niihama around 12:15 on Dec. 27, 213. The weather and cloud conditions around the seeding height are shown in Fig. 3. The height of the cloud s top was 274 m with air temperatures of 12.5 to 14. and wind direction W to WNW, the height of the bottom of the cloud was 17 m with temperatures of 2. to 2.5, and wind direction W to WNW. Then cloud thickness was 167 m. LCD of 4.9 kg was seeded at a seeding rate of 5.5 g/s at a height of 137 m (45 ft) and a temperature of 5 around the air layer with a

4 Journal of Agricultural Meteorology 71 (4), 215 W WNW wind direction four times for 14 min 36 s between 11:23 and 11:48. Rain fell at approximately 11:45 11:5, with a rather stronger rain intensity of about 5 mm/h by the seeding site between 11:23 and 11:27 at the area of central Saijo or Saijo City Office (Saijo CO). This was expected to be artificial rainfall. It stopped after about 5 or 6 min, and fair weather with 7 8% cloud cover formed rapidly. The visual estimation of rain intensity of 5 mm/h was based on the author s long-time experience, it was not 1 or 2 mm/h or 1 mm/h but seemed to be somewhere in the middle, and there was no conflict with the amount of rain at.5 mm and observation time of 5 6 min. Approximately 2 to 3 min after the seeding between 11:23 and 11:27, ice crystals at the seeding height of about 14 m developed quickly as a result of the catch or collision with the surrounding supercooled liquid water drops. Then snow formed from ice crystals that were graupel pellet-type and melted to become rain (Fig. 2, Figs. 3(A), (B)). This indicated a high possibility of artificial rainfall in relation to the seeding time and the starting time of rain (an interval of about 3 min) and based on the estimations of previous experiments (Maki et al., 213a, b; 214 a, b). In regard to the development of the cloud and the accelerated rate of graupel pellets or snow from the 14-m level, the rainfall area and precipitation period of 2 to 3 min was in alignment with the estimation of rainfall time according to the WNW wind direction and wind speed. The hourly precipitation at observation points is shown in Table 2. The precipitation at Saijo Fire Station s main office (Saijo FS), located in a NNE direction of about 1 km from Saijo CO, continued until 6: (:-6: JST) at mm; 6: 7:, 1. mm; 7: 8:, 1. mm; 8: 9:,.5 mm; 9: 12:, mm; 12: 13:,.5 mm; and 13: 18:, mm. The.5 mm rainfall recorded at 13: was determined to be artificial rain, and the observation time of rainfall was thought to be just after 12:. The reasons for these estimations are related to the seeding time, place, height, wind direction, wind speed, and other examples of reaction times found by previous experiments (Maki et al., 213a, b; 214a, b). At AMeDAS Saijo (33 55 N, E, 4 m), located at Shufu, Saijo, in a WNW direction 1 km from Saijo CO, it rained from 5: 6:,.5 mm; 6: 7:, 2. mm; 7: 8:, mm; 8: 9:, 3. mm; 9: 1:,.5 mm; 1: 11:, mm; 11: 12: (11:2),.5 mm; and 12: 17:, mm. It rained until 1: and stopped before the experimental period, but the amount of rain observed from 11: 11:2 was.5 mm. Since the seeding time was from 11:23 11:48, this was not artificial rainfall because of before seeding. However, the amount of rain under.5 mm was possible to observe at the AMeDAS Saijo just after 12:, similar to the Saijo FS. As the next rain was at 17:3 because of the.5 mm scale-type rain gauge, it was not possible to determine if this was artificial rain based on the actual data. As AMeDAS Saijo is located in the western part of Saijo, the evaluation of artificial rain was difficult due to the wind direction at this Fig. 3. Photos of (A) a convective cloud before seeding near the bottom of the cloud around 11:2, (B) the sky clearing after rain fell near central Saijo around 12:, (C) snow or rain as virga near the mountain-side of Niihama around 12:1, and (D) the sky clearing after rain fell near the northern mountainous area of Niihama around 12:15 on Dec. 27, 213. Photos were taken at (A) height 3 m near the east of Imabari, (B) height 2 m near Saijo Fire Station, (C) and (D) height 1 m near Niihama shown in Fig

5 T. Maki et al.:artificial rainfall experiment based on the aircraft seeding of LCD on December 27 in 213 at Saijo Table 2. Amount of precipitation at observation points on Dec. 27, 213. Place / Time AMeDAS Saijo Saijo Fire Station Ohjoin, Niihama FS Besshiyama, Niihama FS AMeDAS Tomisato AMeDAS Ikeda AMeDAS Kyojo Ex.: Amount of rain in time duration 6 is the amount of rain in 5:-6: JST. time. As rain fell from the higher level of the cloud just after seeding, it seemed that the amount of visible cloud was reduced by the artificial rain in the areas of Saijo CO, Saijo FS, and AMeDAS Saijo. The duration of sunshine at AMeDAS Saijo was zero during : 12: but 34 min during 12: 12:4 and almost nothing during the period from 12:4 13:4 (1 min in 13:2 13:3) with the formation of new clouds. This describes how artificial rainfall affects rain phenomena by the seeding and consumption of clouds, i.e., fair weather and recovery of clouds after 1 h. It did not rain around 12: at Kitanocho in the south of Saijo CO or at the mountainous areas of Ohfuki and Hachido. This was in agreement with the estimation of no rain, i.e., artificial rainfall had no effect south of Saijo based on seeding time, seeding route, and the strong WNW wind. There was no rainfall for 3 to 4 h before and after the experimental period during 9: and 16: at AMeDAS and the fire stations at Niihama and Shikokuchuo located at the northern latitude of Saijo FS because of the seeding time, seeding area, wind direction, and wind speed. 3.2 Observation of artificial rain leeward of the LCD seeding area The hourly precipitation rates at the observation points are shown in Table 2. It rained at the Ohjoin and Besshiyama Observatories of the Niihama Fire Station s main office (Niihama FS). At Ohjoin, rain fell until 6: (1: 6:), mm; 6: 7:,.5 mm; 7: 8:,.5 mm; 8: 9:, 2. mm; 9: 13:, mm; 13: 14:,.5 mm; and 14: 18:, mm. Then, the.5 mm rainfall that fell just after 13: (14:) seemed to be artificial rain according to the time, place, wind direction, and wind speed. At Besshiyama, rain fell until 7: (: 7:), mm; 7: 8:, 2. mm; 8: 9:,.5 mm; 9: 1:, 1. mm; 1: 11:, 1.5 mm; 11: 12:, 2.5 mm; 12: 13:, 2.5 mm; 13: 14:,.5 mm; and 15: 16:, mm. According to the seeding time of 11:23 11:48, the effect was observed during the period from 11:4 12:, 1. mm; and 12: 14:, 3. mm; in total, 4. mm of rainfall was presumed to be artificial rain for about 1.5 h from 11:5 13:3 based on the seeding time, seeding area, wind direction, wind speed, and observation from the aircraft near Niihama until 12:2. The artificial rainfall was significant over the southern mountainous area of Niihama and could be clearly observed visually; see Figs. 3(C) and (D). It was shown that the cloud inclined to decrease naturally, but the cloud stimulated by seeding developed to become rain, and then decreased and disappeared. This precipitation was concluded to be artificial rainfall according to the seeding time, seeding place, wind direction, and wind speed. AMeDAS Tomisato (33 55 N, E, 31 m) is located in the southern mountainous area of Shikokuchuo. Rain there was observed at 8: 9:, 1.5 mm; 9: 1:, 1. mm; 1: 11:, 1.5 mm; 11: 12:, 1. mm; 12: 16:, mm; in detail 11: 11:1,.5 mm; 11:1 11:5, mm; and 11:5 12:,.5 mm. The.5 mm rainfall between 11:5 and 12: was presumed to be the artificial rain based on the distance of 3 km from the cloud that developed at the high altitude level of 2 3 m at Tomisato, and on the time passed from 33 to 37 min, wind direction of WNW, and wind speed of 15 m/s at 12:. It almost agreed with 3 to 33 km, but it will be closer to the moving distance if the wind speed of 18 m/s at 9: is used in the case around 11:3. These three-point rains mentioned above were presumably accelerated by mountainous topographical conditions. According to AMeDAS Ikeda (34 1 N, E, 25 m), Tokushima Prefecture, rain was observed until 7: (2: 7:), mm; 7: 8:,.5 mm; 8: 14:, mm; 14: 15:,.5 mm; 15: 16:,.5 mm; 16: 17:, 3. mm; 17: 18:, 6. mm; and 18: 19:, 2.5 mm. Based on these data, the rain of.5 mm at approximately 14:2 14:3 (15:) has the possibility of being artificial rain according to the seeding time, seeding place, wind direction, and wind speed. Another reason is that no rain was observed for about 1.5 h during the period from 14:3 15:5 until a natural rainfall of.5 mm during 15:5 16:, i.e., the interval of 1.5 h can be accepted as separating a period of artificial rain from one of natural rain. At AMeDAS Kyojo (33 52 N, E, 56 m), Tokushima, it rained until 7: (: 7:), mm; 7: 8:, 1. mm; 8: 9:, 1. mm; 9: 1:, 1. mm; 1: 11:,.5 mm; 11: 12:,.5 mm; 12: 13:, mm; 13: 14:,.5 mm; 14: 15:, 1.5 mm; 15: 16:, 1. mm; 16: 17:, 1.5 mm; 17: 18:, 2.5 mm; and 18: 19:, 3. mm. According to these data, 13:3 13:4 (14:),.5 mm; 14:1 14:2, 14:2 14:3, 14:4 14:5 (15:), each.5 mm, for a total of 2. mm, this will be artificial rain according to the time, place, wind direction, and wind speed. This takes place 81 km from the seeding area in 1.5 h with a wind speed of 15 m/s at 15 3 m height (7 85 hpa), the esti

6 Journal of Agricultural Meteorology 71 (4), 215 mated distance is 81 km in 2 h with a wind speed of m/s at 12: at 75 m height (925 hpa) agrees with the transported distance according to the observed data. According to the rainfall data (1 mm scale-type gauge) of Shikoku Mountains Erosion Work Office, Ministry of Land, Infrastructure, Transport and Tourism in Miyoshi City (Ikeda, Higashi Iyayama, and Nishi Iyayama), Tokushima, and Ohtoyo Town, Kochi Prefecture, the observation point of 1 mm of observed rain at 13: was Deai near JR Ikeda Station, Oiya east of Deai, Aruse in Miyoshi south of Iyadani (Ohboke, Koboke) of far south of Ikeda, and Ohtaki and Minamidaiou in Ohtoyo. The point of 1 mm at 14: was Sugenuma east of Kyojo and Kurotakigawa in Ohtoyo and.5 mm at AMeDAS Kyojo, and the point of 1 mm at 15: was Kawasaki southwest of Ikeda and Okinono in Ohtoyo and.5 mm at AMeDAS Ikeda and 1.5 mm at AMeDAS Kyojo. Consequently, there were about 1 points where rain was observed during 13: 15: (actually 12:3 14:3), but there were more than 16 observation points that did not observe rainfall due to topographical conditions (Seto et al., 211; Maki et al., 212; 213a, b) and due mainly to the 1 mm gauge because rains will be mainly.5 to 1. mm. Finally, precipitation in these regions seemed to be artificial rain. Moreover, because there was no rainfall during 15:3 16: in these regions, it was determined that natural and artificial rains could be separated. The rain that fell after 16: seemed to be naturally produced precipitation. The reason was that there was no rain in a wide area until 15:, but.5 mm fell at 16: and 1. mm fell at 17: at Takamatsu,.5 mm at 17: at Tadotsu, and 1. mm at 17: and 1.5 mm at 18: at Tokushima. At AMeDAS Saijo west of Saijo just under the seeding area, no rain was observed by the rain gauge because of the western wind, but the artificial effect was significant in wide eastern areas. The range of rainfall in the eastern part of Ehime included Saijo CO, Saijo FS, Ohjoin and Besshiyama of Niihama FS, and AMeDAS Tomisato. Moreover, in Tokushima and Kochi, there were rainfalls of 2. mm at AMeDAS Kyojo, Higashiiya, and.5 mm at AMeDAS Ikeda, Ikeda in Miyoshi City. Moreover, each 1 mm of rain for the 1-point data for the rain observatory at Tokushima and Kochi was thought to be artificial rain. Next, the amount of rainfall for water resources was estimated on the ranges of rain at Saijo west of its origin, Ikeda to the north, Kyojo to the east, and Ohtoyo to the south. The rain at the Saijo Kyojo area (a km triangle with.5 mm rain) was.31 million tons (mt), at Besshiyama (a 3 2-km rectangle with 4 mm).24 mt, at Kyojo (a 6 3-km rectangle with 2 mm).36 mt, east of Kyojo (a 5 1-km rectangle with 1 mm).5 mt, and in the north surrounding Ikeda (a 2 7-km rectangle with.25 mm).4 mt; the subtotal was about 1. mt, and in the Ohtoyo area (a 1 65-km triangle with 1 mm), it was.32 mt, for a total of 1.32 mt. 3.3 Analysis of the development of a convective cloud using radar images The experiment was conducted at the upper level of air northwest of Saijo in the southern area of the Seto Inland Sea. LCD was seeded by aircraft, then the aircraft flew up to the seeded cloud at approximately 11:5, and we observed it from the upper air. The cloud developed to be a high level of 3 m in spite of the small area (Fig. 3(A), Figs. 4 (A) (D)). The convective cloud changed to rain, and the rain was observed in central Saijo around 11:5, then the cloud rapidly decreased around 12: (Fig. 3(B), Figs. 4(E), (F)). The development of ice crystals in clouds existed in two cases, and the rate of ice crystals caught in supercooled liquid water particles was higher than that of ice crystals connected to each other (Fukuta, 1988; Fukuta et al., 2; Maki et al., 212). Figure 4 shows the radar echo of the convective cloud as higher than the 2 m level at 11: 15:. According to the radar echo, high clouds were found around the eastern seashore in the upper air of Takanawa Peninsula and in the upper air from west of Saijo to Shikokuchuo. The rain intensity of the radar echo was 1 5 mm/h. Somewhat developed rain clouds were observed west of Saijo and Shikokuchuo at 11:3 but not around Niihama. A rain cloud was observed over the Shikoku Mountains in the southern area at 12:, but it decreased and rapidly disappeared; that is, the rain cloud seemed to almost disappear; however, convective clouds developed because of the artificial cloud that resulted from the seeding of LCD, and it seemed to remain over the mountainous region of southern Niihama, as shown in Figs. 4 (E) and (F). This means the rain was observed from the cloud under the condition of no natural rain and/or from the cloud with a small amount of rain. As the cloud finally transformed to rain, after 12: the artificial rain cloud resulting from seeding was disappearing, and finally the cloud over the Shikoku Mountains disappeared almost all of them remained until 12:3. These phenomena were explained even though they were partially repeated. Fig. 4(A) (11:) shows the radar echo of the northwest seashore of Saijo. LCD was seeded to the cloud of the radar echo shown in Fig. 4(B) (11:2) and Fig. 4(C) (11:3) from 11:23 11:48. These clouds moved eastward and developed except for a small region at 11:3 11:4, and it was snowing or raining in the sky (Fig. 4(D)) (11:4), but no snow or rain was observed on the surface. After that, a rather stronger rainfall (about 5 mm/h) was estimated by visible observation and changed to graupel pellet-type snow or rain. The changing pattern is shown in Figs. 4(D) and (E) on the radar echo around 11:4 11:5. The radar echoes in Fig. 4(E) (11:5) and Fig. 4(F) (12:) are shown in the regions from the small area southwest of Saijo to the areas south of Niihama and southwest of Shikokuchuo. It was interesting that the higher clouds in Saijo and Niihama disappeared on the radar echo, i.e., it was thought that a high and significant cloud was dissipated by the artificial rain. The lower cloud could not be detected by the radar; however, stratocumulus clouds of snow or rain existed for a short time there and could be seen from the aircraft. The situation corresponded to the time when the cloud with the rain air mass, i.e., virga (preaecipitatio), appeared. Snow and rain were observed visually from the aircraft and photos taken, as shown as in Figs. 3(C) and (D) at the north slope of the Shikoku Mountains in the south of Niihama, and the remaining cloud, i.e., pannus or scud clouds rose on a ridge of mountain just after the rain stopped. The higher cloud shown by the radar echo around the Saijo and Niihama areas (e.g., strong echo area of oval in Fig. 4(A)) disappeared in the Shikoku Mountains at 12:3, but lower clouds partially remained and could

7 T. Maki et al. Artificial rainfall experiment based on the aircraft seeding of LCD on December 27 in 213 at Saijo Fig. 4. Radar echoes of cloud around Saijo at (A) 11:, (B) 11:2, (C) 11:3, (D) 11:4, (E) 11:5, (F) 12:, (G) 12:3, (H) 13:, (I) 13:3, (J) 14:, (K) 14:3 and (L) 15: on Dec. 27, 213 (JMA). Red oval is objective cloud. be seen over Saijo and Niihama occasionally from the aircraft (Fig. 3(B)). The concluding results follow. The cloud on the radar echo existed around Saijo from 1: 11:. The cloud of the radar echo developed and changed to rain rapidly based on the seeding, and was seen by eye from the aircraft around 11:3 11:4. It was thought that the cloud existed hardly until 11:3, i.e., the cloud almost disappeared as no rain was stimulated, developed and changed to a rather strong rain artificially. After that, the cloud diffused quickly up to 12:3. The rain cloud almost totally disappeared at 12:3 and 13: (Figs. 4(G), (H)), respectively, in the Shikoku Mountains south of Niihama and Shikokuchuo. However, at 13: (Fig. 4(H)), a cloud appeared in the Iya Valley area with the rain at Deai, Oiya, Aruse, Ohtaki, and Minamidaiou. This rain was first explained as virga that changed continuously from a higher cloud with the moving of wind for a long distance and also seemed to be artificial rain with the similar result of the chaintype cloud at Mikura Island in the secondary effect of artificial seeding (Maki et al., 213a, b) and topographical effects (Seto et al., 211; Maki et al., 213b). The low cloud developed and could be detected by radar based on the artificial effect in the leeward valleys and mountains. At 13:3 (Fig. 4(I)), the cloud

8 Journal of Agricultural Meteorology 71 (4), 215 area with 1 5 mm/h enlarged over Iya, and a small cloud appeared over the Tomisato area due to the Tomisato Dam for about 1 min. At 14: (Fig. 4(J)), the cloud enlarged over Iya with rain at Kurotanigawa, Kyojo, and Sugeo. At 14:3 (Fig. 4(K)), the cloud enlarged again over Iya, and rain was observed at Kyojo. A cloud appeared over the Ohsa Konpira area not affected by artificial rain that moved in an eastward direction until 15:. At 15: (Fig. 4(L)), the cloud enlarged again over Iya, and rain was observed at Ikeda, Kawasaki, Okinono, and Kyojo. These were also artificial rains for the fundamental reasons of the seeding time, seeding area, wind direction, and wind speed. 3.4 Analyses of artificial clouds by radar echo top and satellite images The heights of radar echo top cloud from 11: to 12: are shown in Fig. 5. A high cloud over 3 m was found around the northwest of Saijo at 11:. A cloud of 2 to 3 m remained above Saijo until 11:3; however, it was recognized that its region of cloud decreased gradually, and at 11:4 the cloud moved inland, i.e., over central Saijo. During this period, rain was definitely observed on the ground for about 5 6 min at central Saijo. The cloud s area decreased as a result of rain, and the cloud moved to the southeast of Saijo and south of Niihama at 11:5 and decreased more rapidly until 12:. At 12:, the artificial rain area depending on the radar echo top moved to the inland mountainous area. The analyzed changing pattern of radar echo top and radar echo were similar, but the evaluation of cloud development and height could be found in greater detail. The infrared satellite images from 11: to 15: are shown in Fig. 6. The stripe type cloud existed significantly in the Sanin District facing the Sea of Japan (e.g., Fig. 6(B)), and the thin cloud was widely recognized from the seashore area of northern Shikoku to an inland area, i.e., the Shikoku Mountains. At the time, there were rather thick clouds on the Shikoku Mountains (e.g., Fig. 6(A), red oval area) from 11: 12:, they were a little thinner from 12:3 13:3 and a little thicker from 14: 15:. This shows that the artificial effect was found on the clouds, but the clouds were diminished by artificial rainfall and recovered afterward. There were rather thick clouds over Iya and Ohtoyo (e.g., Fig. 6(E), yellow oval area) from 11: 15: continuously. The thick clouds mentioned above seemed to be related to the artificial rain. There were thin clouds in the western part of Kagawa at 11: and from 14: 15: and clouds were not found in Kagawa from 11:3 13:3. There were no clouds east of Iya from 13:3 15: or east of Kagawa from 14:3 15:. There was no relationship to artificial rain in Kagawa and east of Tokushima. 3.5 Analysis of upper weather by the meso scale model (MSM) Figure 7 shows the upper level weather maps by meso scale model (MSM) at the levels of 7 and 85 hpa at 9:, 12:, and 15: on Dec. 27, 213. The initial values of meteorological data at the main observatory are the observation data by AMeDAS, radar, satellite, aerological observation, etc. every 3 h. Moreover, wind direction and Fig. 5. Heights of radar echo top cloud at (A) 11:, (B) 11:2, (C) 11:3, (D) 11:4, (E) 11:5 and (F) 12: on Dec. 27, 213 (JMA)

9 T. Maki et al. Artificial rainfall experiment based on the aircraft seeding of LCD on December 27 in 213 at Saijo Fig. 6. Satellite infrared images at (A) 11:, (B) 11:3, (C) 12:, (D) 12:3, (E) 13:, (F) 13:3, (G) 14:, (H) 14:3 and (I) 15: on Dec. 27, 213 (JMA). speed were data observed at Takamatsu, Kochi, and Tosashimizu in Shikoku by a wind profiler. The height at 7 hpa around Saijo at 9: was 288 m; wind direction was W; wind speed was 18 m/s; air temperature was 12 ; and relative humidity was under 96%. At 12:, it was 287 m, WNW, 15 m/s, 14, under 96%, and at 15:, it was 2865 m, NNW, 15 m/s, 16, under 96%. The height at 7 hpa was inclining to decrease, and wind direction changed gradually from W to WNW and NW. Wind speed decreased slightly, and air temperature was inclining to decrease. It was thought that the increment of upstream in the cloud affected by the seeding of LCD was decreased by the horizontal wind of cold air mass with NW direction as the general wind flowing from the Asian continent. The height on 85 hpa at 9: was 1385 m; the wind direction was WNW; wind speed was 15 m/s; air temperature was 5 ; and relative humidity was over 96%. At 12:, it was 137 m, WNW, 15 m/s, 6, near 96%, and at 15:, 137 m, WNW, 17 m/s, 6, near 96%. It was agreed with the upper weather map on the decreases of height on 85 hpa and of air temperature with time by the cold air mass, and the humidity changed from humid to dry conditions by passing of raining around 12:. At 15:, the horizontal wind speed increased a little, because that the effect of upstream decreased. The height on 925 hpa at 9: was 71 m, wind direction NW, wind speed 11 m/s, air temperature, and relative humidity under 96%, at 12:, 75 m, WNW, 1 m/s,, under 96%, and at 15:, 7 m, WNW, 1 m/s,, under 96%. It was agreed with the upper weather map on the decreasing of height on 925 hpa, wind direction changed from NW to WNW, and wind speed decreased a little. However, the air temperature did not change. Consequently, it was presumed that the decrease in height of the isobaric surface by time was the effect of anticyclone, i.e., fair weather after the artificial rainfall resulting from the seeding. The wind direction changed from W to NNW at the higher level and, on the contrary, from NW to WNW at the lower level. The wind shear was large, and the winds circulated like a vortex at the upper and lower levels. This is probably based on the upwind by the latent heat of the seeding and after the downwind by the artificial rainfall mentioned above. The decrease in air temperature is presumably based on the cold air mass from the continent, and the air temperature decreased as a result of the artificial rainfall mentioned above. These relationships between cause and effect are rather high in relation to each other, but it is not always perfect whether the local artificial rainfall affects a wide air mass or not. The seeding area was the distance of 12 km for the E W direction and 8 km for the N S direction. The seeding distances were similar to the distances in the experiments on Feb. 27, 212, and Mar. 14, 213, near Miyake Island (Maki et al., 213a, b; 214a, b). These seeding actions affected a 1 km length order, so they also seemed to have an effect on the analyzed results based on MSM in this case

10 Journal of Agricultural Meteorology 71 (4), 215 Fig. 7. Upper level weather maps by meso scale model (MSM) of height, air temperature, humidity (over 96%), wind direction and isotach at the levels of 7 hpa and 85 hpa at 9:, 12: and 15: on Dec. 27, 213 (JMA). Fig. 8. Upper level weather maps of height, air temperature, wind direction and wind speed at (A) 9:, (B) 12: and (C) 15: at the isobaric surface of 85 hpa (15m) on Dec. 27, 213 (JMA). The blue or dot line is the height of isobaric surface, red or bold line the air temperature, arrow the wind direction and vane the wind speed as 1 full scale=1 m/s. 3.6 Analysis of upper weather map Figure 8 shows the upper weather maps at 9:, 12:, and 15: at the isobaric surface of the 85 hpa level on Dec. 27. The height of 85 hpa level at 9: around Saijo was 139 m; wind direction was NW-WNW (NW); wind speed was 15 m/s; and air temperature was 5. At 12:, it was 138 m, W WNW (WNW), 12.5 m/s, and 6. The height is almost the same as the height used for seeding. At 12:, rain was already found and the effect seemed to find on the upper air layer. The decrease in height of the isobaric surface, the effect of fair weather, the change in wind direction from NW to WNW, and the decrease in wind speed and air temperature are somewhat related by the artificial rain in this case. However, it is presumable that the decrease in isobaric surface by time is due to the anticyclone for downwind, i.e., cold air mass, and the decrease in air temperature and drying of the upper air mass based on clear and fair weather due to artificial rainfall. Wind direction changed from NW to WNW at the upper layer and from NW to W at the lower layer, that is, a large shear was shown significantly at the upper and lower levels. The decrease of wind speed presumably indicated that the outbreak upstream based on the latent heat by seeding affected in a general horizontal wind (Fukuta et al., 2; Maki et al., 212; 213a, b; 214a, b). This was based on the natural upwind and, moreover, artificial upwind due to the outbreak of latent heat basically by the seeding. At the 85 hpa level, the estimation of upper weather from 15:

11 T. Maki et al.:artificial rainfall experiment based on the aircraft seeding of LCD on December 27 in 213 at Saijo on Dec. 26, shown at 15: on Dec. 27, it was 138 m, WNW, 15 m/s, and 7.5. Actually, the height was low, wind direction did not change, the wind speed was fast, and the air temperature was high. At the 925 hpa level at 9:, the height was 72 m; wind direction was NW; wind speed was 12.5 m/s; and air temperature was. At 12:, 72 m, W WNW (W), 12.5 m/s, and, thus, they did not change significant. The estimation from 15: Dec. 26 showed 71 m, WNW, 12.5 m/s, and 1 at 15: Dec. 27. Actually, the height was low; wind direction showed no change; wind speed was slow; and the air temperature was high. And at 975 hpa level at 9:, it was 29 m, 7.5 m/s, WNW, and 3.5, and at 12:, 285 m, W, 7.5 m/s, and Conclusions The artificial rainfall experiment was conducted using an aircraft for the seeding of LCD for about 15 min under adequate weather and topographical conditions near the north area of Saijo, Ehime, in the northern area of Shikoku Island in the Seto Inland Sea with the climatic type of the Inland Sea of Japan on Dec. 27, 213. (1)After the LCD seeding, the convective cloud observed by the aircraft developed quickly above Saijo from 11:3 11:5 and it rained within 2 3 min. The high-altitude cumulus cloud that developed was changed to rain by the LCD seeding and decreased in size as a result of the artificial rain. The cloud over a mountainous area almost completely disappeared rapidly by 12:3, 1 h after the seeding. Rainfall with a rate of approximately 5 mm/h was observed visually for 5 6 min around 11:5 at the Saijo City office area. The precipitation (rain) was observed at.5 mm until 13: at the Saijo Fire Station. (2)Rain at.5 mm was observed until 14: and at 4. mm from 12: 14: at Ohjoin and Besshiyama at the Niihama Fire Station, respectively, and observed at.5 mm from 11:5 12: at AMeDAS Tomisato. This was expected to be artificial rainfall because of the seeding time, seeding location, wind direction at WNW, and wind speed. The artificial rain was significant on the southern mountainous area of Niihama and Shikokuchuo, Ehime. (3)Radar echo observation showed that the cloud existed hardly until 11:3. The cloud almost disappeared as no rain was stimulated and developed by the seeding of LCD, then it changed to a rather strong artificial rain, and the cloud dissipated until 12:3. (4)The rainfall amounts were.5 mm during 14:2 14:3 at AMeDAS Ikeda, 2. mm during 13:3 15: at AMeDAS Kyojo, Miyoshi, and 1. mm during 13: 15: at 1 points in Miyoshi, Tokushima and Ohtoyo, Kochi. These seemed to be artificial rainfall due to the time, position, direction, and wind speed. (5)The main line of artificial rainfall was Saijo Kyojo with the effect continuing to about 7 km. The amount of artificial rain was roughly estimated to be 1.3 million tons in the areas of Saijo, Ikeda, Sugeo, and Kurotakigawa. (6)The experiment conducted to produce artificial rainfall by LCD seeding at Saijo on Dec. 27, 213 was clearly successful. Acknowledgments The authors would like to express sincere thanks to the staff of SGC Saga Aviation Co., LTD for the aircraft experiment, and Saijo Fire Station, Niihama Fire Station and Shikoku Mountains Erosion Work Office for the offering of rain data. This research was supported by a Grant-in-Aid for Science Research (A), No from the Ministry of Education, Culture, Sports, Sciences and Technology from April 211 to March 214. References Fukuta, N., 1988: Meteorological Engineering new method of meteorological control. Meteorological Research Note, MSJ, (in Japanese) Fukuta, N., Wakimizu, K., Nishiyama, K. Suzuki, Y. and Yoshiokoshi, H., 2: Large unique radar echoes in a new, selfenhancing cloud seeding. Atmospheric Research, 55, Maki, T., Hashimoto, Y., Okushima, R., Mitsuno, T., Noguchi, N., Aoki, M., Isoda, H., Omasa, K., Goto, E., Suzuki, Y., Takatsuji, M., Nonami, H., Hashiguchi, K., Hayakawa, S., Murase, H. and Yamagata, T., 28: Promotion of Artificial Rainfall Technique for Countermeasure of Drought and Prevention of Desertification. Science Council of Japan, (in Japanese) Maki, T., Suzuki, Y., Wakimizu, K., Tomine, K. and Nishiyama, K., 211: Artificial Rainfall. Encyclopedia of Wind, Maruzen Shuppan, Tokyo, (in Japanese) Maki, T., Suzuki, Y., Wakimizu, K. and Nishiyama, K., 212: Artificial Rainfall from countermeasure of drought to water resources, Gihodo Shuppan, Tokyo, (in Japanese) Maki, T., Morita, O., Suzuki, Y. and Wakimizu, K., 213a: Artificial Rainfall Produced by Seeding with Liquid Carbon Dioxide at Miyake and Mikura Islands, Japan. Journal of Developments in Sustainable Agriculture, 8(1), Maki, T., Morita, O., Suzuki, Y. and Wakimizu, K., 213b: Artificial rainfall technique based on the aircraft seeding of liquid carbon dioxide near Miyake and Mikura Islands, Tokyo, Japan. Journal of Agricultural Meteorology, 69(3), Maki, T., Morita, O., Suzuki, Y. and Wakimizu, K., 214a: Artificial rainfall experiment by the aircraft seeding of liquid carbon dioxide near Miyake and Mikura Islands. Agriculture and Horticulture, 89(1), (in Japanese) Maki, T., Morita, O., Suzuki, Y., Wakimizu, K. and Nishiyama, K., 214b: Artificial rainfall experiment by seeding of liquid carbon dioxide above the Izu Islands of Tokyo on March 14 in 213. Journal of Agricultural Meteorology, 7(4), Seto, J., Tomine, K., Wakimizu, K. and Nishiyama, K., 211: Artificial cloud seeding using liquid carbon dioxide: Comparisons of experimental data and numerical analyses. Journal of Applied Meteorology and Climatology, 5, Wakimizu, K., Nishiyama, K., Suzuki, Y., Tomine, K., Yamazaki, M., Ishimaru, A., Ozaki, M., Itano, T., Naito, G. and Fukuta, N., 22: Low level penetration seeding experiment of liquid carbon dioxide in a convective cloud. Hydrological Processes, 16,