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Kelangkaan awan pada saat musim transisi menyebabkan penggunaan pesawat terbang untuk kegiatan modifikasi cuaca menjadi tidak efisien, sedangkan penyemaian awan dari darat sangat terbatas wilayahnya bergantung dari posisi menara Ground Based Generator (GBG) dibangun. Perbaikan sistem penyemaian awan dari darat telah dilakukan dengan menggunakan drone pertanian yang dimodifikasi. Dengan menambahkan sistem penyemburan pada tangki yang telah tersedia, drone dapat digunakan untuk menyemai awan menggunakan bahan semai serbuk berukuran 2-5 mikrometer. Drone akan dioperasikan di wilayah pegunungan dengan menyasar pada awan-awan orografis. Hasil studi explorasi menunjukkan bahwa Drone Agras MG 1 P memenuhi spesifikasi yang dibutuhkan dengan penambahan sistem pengeluaran bahan semai serbuk. Uji sistem penyemaian menunjukkan bahwa bahan semai dapat menyembur keluar sampai ~1,4 meter dari ujung cerobong

Drought is defined as a water deficit condition from normal conditions in the hydrological system. Hydrological drought is a complex process that is preceded by a rainfall deficit. Unlike many other natural disasters, droughts develop slowly, making it difficult to pinpoint the beginning and end of a drought event. Research that focuses on studying the propagation of meteorological drought to hydrological drought is fundamental to revealing the processes and mechanisms of drought propagation. Drought propagation describes the change of meteorological drought signal into hydrological drought through the hydrological cycle. This study aims to analyze the characteristics of drought and evaluate the propagation of drought in the Upper Brantas watershed of East Java. This study uses the Standardized Precipitation Index (SPI) and Standardized Streamflow Index (SSI) methods with an accumulated time of 1, 3, 6, and 12 months to analyze meteorological and hydrological drought characteristics, while the drought propagation was analyzed using Pearson correlation. The results showed that the duration and severity of drought increased with the increase in the period of accumulation of SPI and SSI, while the number of drought events was inversely proportional to the period of accumulation of SPI and SSI. The severity of hydrological drought is higher than the severity of meteorological. The worst hydrological drought (SSI1 = -22.9) with a duration of 12 months occurred in 1997-1998. The high correlation in the condition that there is no time lapse between SSI and SPI shows that the meteorological drought indicator with SPI has the potential to be used as an early detection tool for hydrological drought in the Upper Brantas watershed. This research can be the first step to developing a hydrological drought early detection technique that is very useful in water resource management in watersheds for hydropower operations.

Kebanyakan kejadian hujan di Serpong, Indonesia (6.4°S, 106.7°E) terjadi setelah lewat tengah hari, walaupun demikian hasil pengamatan dengan penakar hujan otomatis selama 6 tahun menunjukkan adanya puncak hujan di pagi hari. Dari struktur awannyayang dipantau oleh BLR menunjukkan bahwa awan di pagi hari yang muncul adalahkebanyakan dari jenis awan Stratiform. Pada tulisan ini akan disajikan kajian statistik dari jenis awan yang muncul di wilayah ini.Most of the precipitation in Serpong (6.4°S, 106.7°E), Indonesia were occurred in the afternoon, however from the 6 years observation by using automatic rain gauge shows another peak of precipitation in the morning. In this paper, the vertical structure of theprecipitating cloud appeared in this area will be analyzed statistically using the data from Boundary Layer Radar (BLR) observation. The result shows that for the morning precipitation, the occurrence of the stratiform-type clouds were dominant.

Teknologi modifikasi cuaca sudah sering diaplikasikan di Indonesia terutama untukmeningkatkan jumlah curah hujan. Teknologi modifikasi cuaca diterapkan bila terjadiindikasi penurunan jumlah curah hujan dan kemungkinan akan munculnya fenomena ElNiño sebagai tindakan preventif. Aplikasi teknologi modifikasi cuaca yang dilaksanakan diDAS Citarum, Jawa Barat mulai tanggal 12 Maret s.d. 10 April 2001 adalah berdasarkan kenyataan bahwa inflow DAS Citarum menurun dengan drastis pada bulan Desember 2000 dan sebagai tindakan preventif akan munculnya fenomena El Niño pada akhir tahun 2001 atau 2002. Pada awal tahun 2001, tiga kaskade waduk di DAS Citarum mengalami defisit cadangan air sebanyak 486,36 juta m . Waduk Ir. Juanda yang merupakan waduk multi fungsi harus menyediakan pasokan air untuk: irigasi teknis pada lahan sawah seluas 296.000 ha (2 kali tanam), yang memberikan kontribusi sebesar ± 40 % ke Jabar atau setara dengan ± 10 % Nasional; air baku permukiman dan industri; serta penyediaan tenaga listrik (± 4,5 milyar kWh). Data akhir setelah dilaksanakan penerapan teknologi modifikasi cuaca dengan menggunakan konsep sistim dan lingkungan adalah nilai rata-rata aliran total Citarum sebesar 326,81 m /det dan volume total aliran Citarum sejak mulai kegiatan hingga tanggal 10 April 2001 adalah sebesar 847,1 juta m3.Weather modification technology has been applied in Indonesia especially to enhancerainfall. Weather modification technology has been employed whenever there has beenan indication of rainfall shortage and the possibility of El Niño occurrence asprecautionary action. Weather modification technology that was applied in Citarumcatchment area – West Java on 12 March – 10 April 2001 was based on the fact thatCitarum inflow decreased drastically in December 2000 and also as a preventiveendeavor to the possibility of warm episode in 2001/2002. In the early of 2001, threecascade dams had water storage deficit as much as 486.36 million m3. Ir. Juanda dam,which has multi purposes, has to supply water for: technical irrigation for 296,000 ha ofrice field (2 planting seasons) that contributes ± 40 % to West Java or about ± 10 % ofnational production; fresh water for community and industry; as well as electricity of about 4.5 billion kWh. After the application of weather modification technology by employing system and environment concept, it was recorded that the average inflow of Citarum catchment area was 326.81 m /sec and total volume during the activity was 847.1million m3.

Penelitian dengan menggunakan disdrometer untuk mengamati karakteristik hujan diwilayah Bukittinggi telah dilakukan pada bulan Agustus 2001 sampai dengan November2001. Perbandingan hasil pengukuran curah hujan dengan penakar hujan dan distribusibutir hujan menunjukkan korelasi yang kuat. Dalam penelitian ini, distribusi butir hujan dianalisis berdasarkan jenis awan hasil analisis boundary layer radar yang ada dilokasiyang sama. Perbedaan distribusi butir hujan terlihat dengan jelas antara hujan yangterjadi dari awan convective dan awan stratiform.Study on rainfall characteristic in Bukitttinggi using disdrometer has been done duringrainy season 2001. Comparison of rain gauge measurement and disdrometer is wellassociated. In this research, dropsize distribution has also been analized based on cloudtype which is analyzed by using boundary layer radar. The difference between drop sizedistribution of each cloud type can easily be seen, especially between stratiform type andconvective type of cloud.

Boundary Layer Radar (BLR) merupakan sebuah L-band Doppler radar. BLR yang terletak di Serpong, merupakan program kerjasama pengamatan antara RASC Kyoto University, Jepang, BPPT dan LAPAN. Pada dasarnya BLR digunakan untuk mengamati dinamika atmosfir pada kondisi udara cerah dari permukaan sampai ketinggian 3 km. Pada tulisan ini akan ditunjukkan bahwa BLR dapat juga digunakan untuk mengamati hujan.Boundary Layer Radar is an L-band Doppler radar. BLR that located at Serpong, Indonesia (6°S, 107°E) is a collaborative program between RASC, Kyoto University, Japan, BPPT and LAPAN. Although this radar is basically designed to measure winds in clear-air. This study, however, shows that BLR can also be used to detect the rain drops.